Use of polyoxypropylene and polyoxyethylene terpene compounds in emulsion polymerization

This patent application claims priority from provisional patent application Ser. No. 60/633,050 filed on Dec. 3, 2004.

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(R 3 )—CH(R 4 )—O] n —[CH 2 CH 2 —O] m —R 5

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. R 3 and R 4 , which may be identical or different, represent hydrogen or a linear, branched or cyclic, saturated or unsaturated C 1 -C 22 hydrocarbon radical, provided that at least one of the radicals R 3 or R 4 is other than hydrogen; and R 5 represents hydrogen, or a group selected from the following:

—SO 3 M —PO 3 (M) 2 —(CH 2 ) r —COOM —(CH 2 ) n —SO 3 M

in which formula, M represents hydrogen, an alkali metal or an ammonium function N(R) 4 +, in which R, which may or may not be identical, represents hydrogen or a linear, branched or cyclic, saturated or unsaturated C 1 -C 22 hydrocarbon radical, which may be hydroxylated; r is in the range 1 to 6; z is in the range 1 to 6; n is a whole number or fraction in the range 0-20 inclusive; m is a whole number or fraction in the range 2-80 inclusive.

The Z radical is optionally substituted by at least one C 1 -C 6 alkyl radical and may comprise a backbone selected from those indicated below or the corresponding backbones minus the double bond:

Y represents —CH 2 —C(R 1 )(R 2 )—O— or —O—CH(R′ 1 )—CH(R′ 2 )—O—, wherein R 1 , R 2 , R′ 1 , R′ 2 , which may be identical or different, represent hydrogen or a linear, branched or cyclic, saturated or unsaturated C 1 -C 22 hydrocarbon radical, preferably C 1 -C 6

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, CH 3 , or C 2 H 5 ; 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, CH 3 or C 2 H 5 .

The Nopol surfactant can be made by different routes. For example, a preferred surfactant wherein X is a sulfate, for example, —OSO 3 H 2 , 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 —OSO 3 H 2 group or sulfonate —SO 3 H 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 T g monomer (e.g. methyl methacrylate) and a low T g 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.