Patent Grant
7501470
The present invention relates to emulsion polymerization using terpene based surfactants as emulsifiers. The terpene based surfactants comprise oxypropylene and oxyethylene units. The invention also relates to emulsion polymerization using the sulfate and phosphate salts of the terpene based surfactants as emulsifiers. Further, the present invention relates to methods of using such emulsions formed from the terpene based surfactants.
Polymers, both synthetic and natural, have been employed in aqueous solutions as thickening and flocculating agents. They have found commercial use in a variety of end uses such as wastewater treatment, water purification, papermaking, petroleum recovery, oil drilling mud stabilizers, and latex. Latex is a water based polymer dispersion, widely used in industrial applications.
Polymerization is a preferred technology used to make emulsion polymers and polymer latexes. The use of latex, produced by emulsion polymerization, in the production of paints or coatings for substrates is well known in the art. However, such paints or coatings are adversely affected by the presence of emulsifiers required in the emulsion polymerization process. The emulsifiers often cause foaming in the paint or coating. It would be desirable to have an emulsifier having low foaming effects and improved stability properties.
Furthermore, in latex polymerization, surfactants are necessary to provide stable monomer pre-emulsion, stability during the polymerization, and overall stability of the final latex. However, traditional surfactants for polymerization of latexes and emulsions tend to create foaming upon agitation and cause other difficulties during the polymerization process and in the final formulations containing the latex. To overcome this, a defoamer is generally required. Unfortunately, addition of a defoamer has numerous drawbacks including dewetting of the coating and increased raw material cost. It would be desirable to have a polymerization surfactant having low foaming effects and improved stability properties.
This invention provides a process for the production of polyoxypropylene and polyoxyethylene terpene based surfactants, and processes to produce emulsion polymers of such polyoxypropylene and polyoxyethylene terpene based surfactants and the resulting emulsion polymer products. The polyoxypropylene and polyoxyethylene terpene based surfactants produced by the process of this invention produce emulsion polymers of greatly improved properties compared to emulsion polymers produced from conventional surfactants.
Particularly, the invention is directed to the use of polyoxypropylene and polyoxyethylene terpene based surfactants for latex synthesis. More particularly, the invention is directed to the use of alkoxylate surfactants and their sulfate and phosphate salts useful in emulsion and latex synthesis. Even more particularly, the invention is directed to the use of alkoxylates of 6,6-dimethylbicyclo[3,1,1]hept-2-ene-2-ethanol and their sulfate and phosphate salts as emulsifiers useful in emulsion and latex polymerization.
Furthermore, the polyoxypropylene and polyoxyethylene terpene based surfactants may be nonionic or anionic.
The present invention relates to the use, in emulsion polymerization, of a terpene based surfactant. The terpene based surfactant in accordance with the invention comprises at least one compound having the following formula:
Z-Y—[CH(R3)—CH(R4)—O]n—[CH2CH2—O]m—R5
in which Z represents a bicyclo[a,b,c,]heptenyl or bicyclo[a,b,c]heptyl radical, and wherein a+b+c=5 and a=2, 3, or 4; b=2 or 1; and c=0 or 1. R3 and R4, which may be identical or different, represent hydrogen or a linear, branched or cyclic, saturated or unsaturated C1-C22 hydrocarbon radical, provided that at least one of the radicals R3 or R4 is other than hydrogen; and R5 represents hydrogen, or a group selected from the following:
The Z radical is optionally substituted by at least one C1-C6 alkyl radical and may comprise a backbone selected from those indicated below or the corresponding backbones minus the double bond:
Y represents —CH2—C(R1)(R2)—O— or —O—CH(R′1)—CH(R′2)—O—, wherein R1, R2, R′1, R′2, which may be identical or different, represent hydrogen or a linear, branched or cyclic, saturated or unsaturated C1-C22 hydrocarbon radical, preferably C1-C6
In a preferred embodiment of the invention a suitable terpene based surfactant comprises the use of Nopol derivative surfactants. Accordingly, the invention further provides for the novel use of Nopol derivative surfactants to make emulsion polymers or polymer latexes. In one aspect, this invention relates to a method of making Nopol alkoxylate surfactants of 6,6-dimethylbicyclo[3,1,1]hept-2-ene-2-ethanol. The alkoxylate surfactants may be nonionic or anionic. The anionic alkoxylate surfactants are preferably sulfates or phosphates of the 6,6-dimethylbicyclo[3,1,1]hept-2-ene-2-ethanol alkoxylate. Suitable alkoxylate compounds are described in U.S. patent application Ser. No. 10/820,929, which is herein incorporated by reference.
Preferred alkoxylated surfactants have the general formula:
where R is hydrogen, CH3, or C2H5; n is from 0 to 20 inclusive, m is from 2 to 80 inclusive; and X represents a hydrogen atom, phosphate, sulfate, sulphonate, or carboxylate group. The moiety qualified by the integer “n” corresponds to oxypropylene units. Oxypropylene can also be substituted by oxybutylene or similar alkoxylates. The moiety qualified by the integer “m” corresponds to oxyethylene units. The oxypropylene and oxyethylene units may be of block distribution or intermixed in random or tapered distribution along the chain. The compounds of the formula may also be described as alkoxylates of 6,6-dimethylbicyclo[3.1.1]hept-2-ene-2-ethanol.
Preferred anionic alkoxylated surfactants have the general formula above wherein X represents a sulfate or phosphate group, and preferred nonionic alkoxylated surfactants have the general formula above wherein X represents a hydrogen group.
The terpene based surfactants described above are used in latex emulsion polymers or as emulsifiers/surfactants in emulsion polymerization. Latex, water based dispersions of polymers obtained by emulsion polymerization, are widely used in various applications such as paints, adhesives, paper coatings, carpet backing and rheology modifiers (HASE).
As discussed previously, the surfactants used to stabilize the latex can increase foaming during the manufacturing of the latex and in the final application and require the addition of a defoamer that may have other inconveniences such as the dewetting of the coating responsible for the formation of fish eyes in the paint film. The foaming phenomenon is also detrimental to paint quality and should be avoided. The terpene based surfactant of this invention may be used as replacements for traditional foamy emulsifiers employed in emulsion polymerization and eliminate or avoid the problem or drawbacks in the resulting latex and its final applications such as paints, coatings, adhesives, or rheology modifiers.
In another aspect, this invention relates to a method of making an emulsion polymer by emulsion polymerization in the presence of a terpene based surfactant. For example, an emulsion polymer is produced by emulsion polymerization in the presence of a Nopol surfactant having the formula:
where R is hydrogen, CH3 or C2H5.
The Nopol surfactant can be made by different routes. For example, a preferred surfactant wherein X is a sulfate, for example, —OSO3 H2, group can be made by sulfation of the product of esterification of a 6,6 dimethylbicyclo [3,1,1]hept-2-ene-2-ethanol alkoxylate. A Nopol surfactant wherein X is a sulfate —OSO3H2 group or sulfonate —SO3H group, can be made by sulfating one of the hydroxyl groups of the alkoxylate, or replacing the hydroxyl group with a sulfonate group, and then esterifying the remaining hydroxyl group of the alkoxylate with a vinyl-functional carboxylic acid, anhydride, or acid halide thereof.
Emulsion polymerization is discussed in G. Pohlein, “Emulsion Polymerization”, Encyclopedia of Polymer Science and Engineering, vol. 6, pp. 1-51 (John Wiley & Sons, Inc., N.Y., N.Y., 1986), the disclosure of which is incorporated herein by reference. Emulsion polymerization is a heterogeneous reaction process in which unsaturated monomers or monomer solutions are dispersed in a continuous phase with the aid of an emulsifier system and polymerized with free-radical or redox initiators. The product, a colloidal dispersion of the polymer or polymer solution, is called a latex.
The comonomers which are typically employed include such monomers as methyl acrylate, ethyl acrylate, methyl methacrylate, butyl acrylate, 2-ethyl hexyl acrylate, other acrylates, methacrylates and their blends, acrylic acid, methacrylic acid, styrene, vinyl toluene, vinyl acetate, vinyl esters of higher carboxylic acids than acetic acid, e.g. vinyl versatate, acrylonitrile, acrylamide, butadiene, ethylene, vinyl chloride and the like, and mixtures thereof.
In the above process, suitable initiators, reducing agents, catalysts and surfactants are well known in the art of emulsion polymerization. Typical initiators include ammonium persulfate (APS), hydrogen peroxide, sodium, potassium or ammonium peroxydisulfate, dibenzoyl peroxide, lauryl peroxide, ditertiary butyl peroxide, 2,2′-azobisisobutyronitrile, t-butyl hydroperoxide, benzoyl peroxide, and the like.
Suitable reducing agents are those which increase the rate of polymerization and include for example, sodium bisulfite, sodium hydrosulfite, sodium formaldehyde sulfoxylate, ascorbic acid, isoascorbic acid, and mixtures thereof.
Suitable catalysts are those compounds which increase the rate of polymerization and which, in combination with the above-described reducing agents, promote decomposition of the polymerization initiator under the reaction conditions. Suitable catalysts include transition metal compounds such as, for example, ferrous sulfate heptahydrate, ferrous chloride, cupric sulfate, cupric chloride, cobalt acetate, cobaltous sulfate, and mixtures thereof.
Suitable surfactants which may be used in conjunction with the Nopol surfactant include ionic and nonionic surfactants such as alkyl polyglycol ethers such as ethoxylation products of lauryl, tridecyl, oleyl, and stearyl alcohols; alkyl phenol polyglycol ethers such as ethoxylation products of octyl- or nonylphenol, diisopropyl phenol, triisopropyl phenol; alkali metal or ammonium salts of alkyl, aryl or alkylaryl sulfonates, sulfates, phosphates, and the like, including sodium lauryl sulfate, sodium octylphenol glycolether sulfate, sodium dodecylbenzene sulfonate, sodium lauryldiglycol sulfate, and ammonium tritertiarybutyl phenol and penta- and octa-glycol sulfonates, sulfosuccinate salts such as disodium ethoxylated nonylphenol half ester of sulfosuccinic acid, disodium n-octyldecyl sulfosuccinate, sodium dioctyl sulfosuccinate, and the like.
A typical process of emulsion polymerization preferably involves charging water to a reactor and feeding as separate streams a pre-emulsion of the monomer and a solution of the initiator. A small amount of the pre-emulsion and a portion of the initiator may be charged initially at the reaction temperature to produce a “seed” latex. The “seed” latex procedure results in better particle-size reproducibility. Under “normal” initiation conditions, that is initiation conditions under which the initiator is activated by heat, the polymerization is normally carried out at about 60-90° C. A typical “normal” initiated process, for example, could employ ammonium persulfate as initiator at a reaction temperature of 80+/−2° C. Under “redox” initiation conditions, that is initiation conditions under which the initiator is activated by a reducing agent, the polymerization is normally carried out at 60-70° C. Normally, the reducing agent is added as a separate solution. A typical “redox” initiated process, for example, could employ potassium persulfate as the initiator and sodium metabisulfite as the reducing agent at a reaction temperature of 65+/−2° C.
In the above emulsions, the polymer preferably exists as a generally spherical particle, dispersed in water, with a diameter of about 50 nanometers to about 500 nanometers.
In particular, the terpene based surfactants of this invention may be incorporated in effective amounts in aqueous polymer systems to enhance the stability of emulsions of the polymers. Commonly used monomers in making acrylic paints are butyl acrylate, methyl methacrylate, ethyl acrylate and the like. In acrylic paint compositions the polymer is comprised of one or more esters of acrylic or methacrylic acid, typically a mixture, e.g. about 50/50 by weight, of a high Tg monomer (e.g. methyl methacrylate) and a low Tg monomer (e.g. butyl acrylate), with small proportions, e.g. about 0.5% to about 2% by weight, of acrylic or methacrylic acid. The vinyl-acrylic paints usually include vinyl acetate and butyl acrylate and/or 2-ethyl hexyl acrylate and/or vinyl versatate. In vinyl-acrylic paint compositions, at least 50% of the polymer formed is comprised of vinyl acetate, with the remainder being selected from the esters of acrylic or methacrylic acid. The styrene/acrylic polymers are typically similar to the acrylic polymers, with styrene substituted for all or a portion of the methacrylate monomer thereof.
In order to further illustrate the invention and the advantages thereof, the following non-limiting examples are given.
Latex trials 1 to 13 were prepared using the following formulation:
1% based on total monomer concentration
Surfactant substitutions and changes in surfactant percent concentrations, were as indicated in the following trials.
Table 1 results showed that similar latex properties can be achieved with Nopol PO/EO sulfates of several different molecular weight ranges.
The results shown in Table 2 indicate that similar latex properties can be achieved with Nopol PO/EO sulfates of several different molecular weight ranges. Table 2 further illustrates the effect of adding Nopol PO/EO sulfate to the kettle charge and the ability to vary the particle size in the final latex (compare to Table 1).
Trials 7-9 were performed to “tune” the particle size of the Nopol PO/EO sulfate so that they were in the 250-300 nm range. Rhodapex CO-436 (trial # 6) was also in the 250-300 nm range. The particle size was controlled so as not to cause interference or variations in tests that can be affected by particle size variation, such as freeze/thaw, foaming, Ca++ and mechanical stability.
The results in Table 3 continue to show that Nopol PO/EO sulfates of several different molecular weights produce similar latex properties such as mechanical, chemical and temperature stability, film quality and surface tension, compared to the control surfactant. Film aspect was excellent for all latexes tested in Table 3, yielding draw downs that are clear and free of defects. No observable difference was seen between the control and Nopol PO/EO sulfate latex films. The results in Table 3 also illustrate that Nopol PO/EO sulfates of several different molecular weights can be used to produce latex with lower foaming properties, as seen in lower initial foam height as well as lower foam height over time.
Four PSA latexes were tested for peel and tack properties. The latex trials tested are described in Table 2.
Loop Tack Testing:
Samples were prepared by drawing down the neutralized latex onto PET film with a 3 mil 3″ drawdown bar. The draw downs were allowed to air dry, and were oven cured at 105° C. for 5 minutes prior to covering the film with release paper. A 1″ wide strip was cut from the PET/adhesive/release paper “sandwich” and cut to 7″ long with the adhesive in the center for loop tack testing. The ends were taped for the grips, and the testing was performed by lowering the adhesive coated PET film strip to 1″ from the SS test surface. The 1″ setting ensures that each sample is forced against the SS surface with the same pressure. The Instron Tensiometer® was used to pull the loop up at 12″/minute, and the peak force required to remove the loop was recorded.
180° Peel Test:
The sample prep was a little different for the peel test, in that the drawdown was done at the low end of the PET film, as opposed to the center. This was done so that a long “tail” of PET was left for the upper grip to grab for the peel test. Standard SS substrates were used and the pressure applied to the adhesive coated PET film was kept uniform by using a standard roller for the same number of passes at approximately the same speed.
Generally, strong tack and good resistance to peel is desired in pressure sensitive adhesive latexes, and both properties can potentially be impacted by the surfactant used to make the latex.
The data in Table 4 summarizes the results of the 180° peel and loop tack testing. Multiple replications were performed for each sample. The Nopol sulfate latexes showed equivalent or better performance vs. the control.
The results shown in Table 5 show that similar latex properties can be achieved with Nopol PO/EO sulfates of several different molecular weight ranges, compared to the control surfactant. Table 5 illustrates the effect of adding Nopol PO/EO sulfate to the kettle charge and the ability to vary the particle size in the final latex.
Latex trials 14 to 27 were prepared using the following formula:
1% based on total monomer concentration
Surfactant substitutions and changes in surfactant percent concentrations, were as indicated in the following trials.
Table 6 shows the latex properties of the Example 2 Nopol PO/EO sulfate formulation in comparison to three commercially available surfactants. Table 6 illustrates that similar latex properties were achieved with the Nopol PO/EO sulfate compared to the control commercial surfactants.
The Table 7 results show that similar latex properties can be achieved with Nopol PO/EO sulfates of several different molecular weight ranges, in comparison to the control surfactants (Table 6).
The Table 8 results show that latex particle size can be adjusted (“tuned”) by changing the amount of surfactant added upfront in the kettle charge while maintaining the same total amount of surfactant used in the polymerization. (See control surfactant trials in Table 6, for comparison.) When the control surfactants and Nopol PO/EO sulfate were adjusted to the same particle size range, as in Table 8, lower foaming results are achieved with the Nopol PO/EO sulfate in comparison to the commercially available surfactants.
Latex trials 28 to 32 were prepared using the following formula:
1% based on total monomer concentration
2tert- butyl hydroperoxide, 70%
Surfactant substitutions and changes in surfactant percent concentrations, were as indicated in the following trials.
Table 9 shows the latex properties of the Example 3 formulations, which uses both an anionic surfactant (Surfactant A) and a nonionic surfactant (Surfactant B).
Anionic surfactants, such as sulfated alcohol ethoxylates, carry a negative charge. Nonionic surfactants, such as alcohol ethoxylates, have a neutral charge. Some latex formulations use both types of surfactant to optimize certain properties, such as stability and resistance to salts.
The results in Table 9 compare two commercially available standard surfactants to a Nopol PO/EO sulfate (anionic) and also a Nopol PO/EO (nonionic). In Trial # 30 the Nopol PO/EO sulfate is substituted for the control anionic surfactant. In Trial # 31 the Nopol PO/EO is substituted for the control nonionic surfactant. In Trial # 32, both Nopol surfactants were substituted for the control surfactants.
As illustrated in Table 9 similar latex properties were achieved with the Nopol based surfactants. Table 9 further illustrates that lower foaming properties were achieved by substituting the Nopol PO/EO sulfate for the control anionic surfactant.
This patent application claims priority from provisional patent application Ser. No. 60/633,050 filed on Dec. 3, 2004.
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| Number | Date | Country | |
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| 20060135683 A1 | Jun 2006 | US |
| Number | Date | Country | |
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| 60633050 | Dec 2004 | US |
