CA1174775A - Method of imparting salt and/or mechanical stability to aqueous polymer microsuspensions - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An improved method of imparting salt and/or mechanical stability to an aqueous polymer microsus-pension comprising admixing with the microsuspension a stabilizing amount of a mono- and dialkyldiphenyl ether sulfonate surfactant composition comprising, by weight, at least 35 weight percent, based on the total weight of the composition, of at least one dialkyl-diphenyl ether sulfonate.

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Description

117477~

IMPROVED METHOD OF IMPARTING SALT
AND/OR MECHANICAL STABILITY TO
AQUEOUS POLYMER MICROSUSPENSIONS

This invention relates to aqueous polymer microsuspensions. In one aspect, the invention relates to stabilizing these microsuspensions to various salt and mechanical conditions while in another aspect, the inven-tion relates to stabilizing these microsuspensions withalkyldiphenyl ether sulfonate surfactant compositions.

Surfactant compositions comprising alkyldi-phenyl ether sulfonates are known in the art. A series of such compositions is manufactured by The Dow Chemical Company under the trademark DOWFAX~. Representa~ive of these compositions are mixtures containing greater than 70 weight percent monoalkylated, essentially disulfonated diphenyl oxide. Both the chain length of the alkyl group and the neutralizing cation of the sulfonate group can vary to convenience. These composltions have a plurality of known utilities including imparting salt and mechanical stability to various aqueous polymer microsuspensions.

, :

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~174~7~i According to this invention, the salt and/or mechanical stability imparted to an aqueous polymer microsuspension by a mono- and dialkyldiphenyl ether sulfonate surfactant composition is improved wherein at least 35 weight percent of the composition is at least one dialkyldiphenyl ether sulfonate.

The surfactant compositions used in the prac-tice of this invention comprise at least 35 weight percent, preferably at least 40 weight percent, and most preferably at least 50 weight percent, of at least one dialkyldiphenyl ether sulfonate. These sulfonates are of the general formula R R

~ O ~ (I) (SO3 M )x (SO3 M )y wherein each R is an alkyl radical and each R can be the same or different, each M~ is a hydrogen, alkali metal ion, alkaline earth metal ion or ammonium ion and each M~ can he the same or different, and x and y are individually 0 or 1 with the proviso that x or y is 1 and the average value of ~(x+y) for all (I) is at least 1.7 and preferably at least 1.8. R is preferably an alkyl radical of between 4 and 18 carbon atoms, and more preferably of between 1~ and 18 carbon a-toms.
The alkyl radicals of R can be linear, branched or cyclic but the linear and branched radicals are preferred. The M~ ammonium ion radicals are of the formula -~- 27,982-F -2--~79~77S

(R')3HN (II) wherein R' is a hydrogen, Cl-C4 alkyl or Cl-C4 hydroxy-alkyl radical and each R' can be the same or different.
The illustrative Cl-C~ alkyl and hydroxyalkyl radicals include: methyl, ethyl, propyl, isopropyl, butyl, hydroxymethyl, hydroxyethyl, etc. Typical ammonium ion radicals include: ammonium (N H4), methylammonium ~CH3N H3), ethylammonium (C2H5N H3), dimethylammonium ((CH3)2N H2), methylethylammonium (CH3N H2C2H5), tri-methylammonium ((CH3)3N H), dimethylbutylammonium((CH3)2N HC4~93, hydro~yethylammonium (HOCH2CH2N H3), methylhydroxyethylammonium (CH3N H2CH2CH20H), etc- M is preferably an alkali metal ion and more preferably an ion of sodium or potassium.

The remainder of the surfactant composition typically comprises at least one monoalkyldiphenyl ether sulfonate. This material is similar in structure to the sulfonate of Formula I except it has but one R group which can be attached to either nucleus and, like the sulfonate of Formula I, the R can be ortho, meta or para to the ether oxygen. The monoalkyl diphenyl ether sul-fonate is present in no more than 65 weight percent, preferably no more than 60 weight percent, and most p~eferably no more than 50 weight percent, of the composition. The surfactant compositions of this invention can be essentially void of any monoalkyl diphenyl ether sulfonate, and other materials as well, and thus be essentially 100 weight percent dialkyldi-phenyl ether sulfonate.

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The dialkyldiphenyl ether sulfonates here used are known compounds and are readily prepared and formulated into surfactant compositions by any one of a number of known methods. One well-known and accepted method is taught by Steinhauer et al., USP 2,990,375 and comprises a series of steps, the first step comprising preparing an alkyldiphenyl ether by reacting an olefin or an olefin halide, such as tripropylenes, tetrapropylenes, pentapropylenes or dodecyl bromide, with diphenyl ether at a temperature between about 50C and about 100C in the presence of a Friedel-Crafts catalyst, such as aluminum chloride. The reaction mixture is washed with water to remove the catalyst, the phases separated, and the organic-rich phase subjected to distillation to obtain a fraction consisting of a mixture of monoalkylated diphenyl ether and dialkylated diphenyl ether. The member of alkyl substituents per diphenyl ether molecule can be controlled by adjusting the relative proportions of the reactants. Alternatively, the distillation can be performed so as to separate the mono- and dialkylate diphenyl ethers from one another and from lower or higher boiling ingredients after which the mono and dialkylated diphenyl ether fractions can be combined at a desirable ratio.

The mixture of mono- and dialkyldiphenyl ethers is subsequently reacted with a sulfonating agent, such as chlorosulfonic acid or sulfur trioxide, while the reactants are dissolved in an inert liquid polychlorinated aliphatic hydrocarbon solvent, such as methylene chloride, carbon tetrachloride, perchloroethylene, tetrachloroethane, ethylene dichloride, etc., and at a reaction temperature between 20C and S0~C. The sulfonating reaction proceeds -~ 27,982-F -4-~L7477S

readily with the introduction of one sulfonic acid radical per aromatic nucleus such that an average of at least 1.7, and preferably at least 1.8, of the aromatic nuclei present in the reaction mi~ture are sulfonated.

Upon completion of the sulfonation reaction, the mixture is neutralized and made slightly alkaline, e.g., is brought to a pH value between 7 and 8, with a base, such as sodium hydroxide, potassium hydroxide, an amine, or an aqueous solution of the same, to convert the mono- and dialkyldiphenyl ether sulfonic acids to the corresponding salts~ The aqueous and or~anic layers are then separated and the sulfona-tes contained in the aqueous layer. The sulfonates can be in admixture with lesser amounts of inert materials, principally alkali sulfates, e.g., sodium sulfate or potassium sulfate if these were the neutralizing materials, with lesser amounts of alkali chlorides and water. The presence of these inert materials in small quantities does not adversely affect this invention. Further description and alternative steps for preparing the dialkyldiphenyl ether sulfonates and the surfactant compositions of this invention are disclosed in Steinhauer et al., USP 2,990,375.

The surfactant compositions or formulations of this invention are used in the same manner as known surfactant compositions. They can be admixed with either a polymer microsuspension precursor, prior to polymeriza-tion, or to the microsuspension itself, as a post-additive, after polymerization. If added after the polymer micro-suspension is formed, the compositions impart an increased or improved degree of mechanical and/or salt (electrolyte) stability. If added to a polymer microsuspension precur-sor, the compositions of this invention not only impart --- 27,982-F -5 .

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,, improved mechanical and/or salt stability to the final polymer microsuspension, but also aid in the production of the polymer microsuspension par-ticles without increasing the concentration of the surfactant composition. However, in certain late~ systems where the polymeric solids are composed of primarily hard monomers, such as styrene, post addition is preferred. Moreover, and particularly in non-seeded systems, when added to a polymer micro-suspension precursor, the surfactant composition can be used to influence ultimate particle size by merely adjusting the mono-:dialkylate ratio, or in other words, without having to increase or decrease the concentration of the surfactant composition. To what extent and in what direction (larger or smaller) particle size will be influenced is dependent on several factors among which include kind of pol~mer precursor and initial loading of surfactant.

A stabilizing amount of surfac-tant composition is added to the aqueous polymer microsuspension. A typi-cal minimum amount is 0.05 weight percent and preferably0.5 weight percent based on the weight of the microsus-pension. Practical considerations, such as convenience and economics, are the only limitations upon the maximum amount of surfactant composition that can be added but a maximum amount of 5 weight percent and preferably of

2 weight percent is generally employed.

"Aqueous polymer microsuspension" here means polymer particles dispersed in an aqueous phase continuum wherein the polymer is in the solid state as contrasted to the viscous liquid state. These microsuspensions are sometimes known as aqueous polymer dispersions. Polymers suitably microsuspended or dispersed include any normally 27,982-F -6-~7477~

solid (e.g., melting above 20C) thermoplastic resin whose degradation point is at a somewhat higher tempera-ture than its melting point. The polymers include, among others, polyolefins; diene rubbers such as polybutadiene-1,3 and copolymers of 1,3-butadiene with copolymerizable monomers such as styrene, acrylonitrile, etc.; vinyl resins, such as vinyl pyridine; olefin-vinyl copolymers;
polyamides; epoxy resins; homopolymers and copolymers of monovinylidene aromatic monomers; acrylic resins; poly-esters; polycarbonates; polyurethanes; etc. Vinyl micro-suspensions, such as those produced from at least one vinyl monomer, particularly benefit from this invention.
Exemplary microsuspensions include those prepared from styrene/butadiene, ethyl acrylate, polyvinyl chloride, polyvinyl acetate, etc. Further illustration of micro-suspensions that benefit from this invention is given by Warner et al., U.S. Patent 4,123,4a3. The typical par-ticle size (diameter) o~ these microsuspensions range from 150 angstroms to 10,000 angstroms, and preferably 20 between 500 and 3,000 angstroms.

The following are illustrative embodiments of this invention. Unless indicated otherwise, all parts and percentages are by weight.
:

Specific Embodiments Examples 1-2 and Controls A-B:
The microsuspensions here used were prepared by first charging a reactor with deionized water (70 parts per 100 parts monomer), Versonol~-120 (0.0125 parts per 100 parts monomer, trisodium salt of N-~hydroxyethyl)-ethylenediaminetriacetic acid (an organic chelating agent manufactured by The Dow Chemical Company) and a surfactant - 27,982-F -7-117~77~

(1.35 parts per 100 parts monomer, reported in Table I).
The contents of the reactor were heated to 80C and then 588.9 g/hr for 3 hours and subse~uently 294.4 g/hr for 3 hours of monomer was charged to the reactor. The monomer consisted of 54 parts styrene, 44 parts butadiene, 2 parts acrylic acid and 6 parts carbon tetrachloride.
After the ~ hours of monomer charging, 120.9 g/hr for 6 hours of aqueous mix (with a 15-minute aqueous prestart) was added to the reactor. The a~ueous mix consisted of 28 parts deionized water, 0.005 parts Versonol~-120, 0.3 parts surfactant (same as used in first charge), 0.6 parts sodium persulfate, and 0.12 parts sodium hydroxide.
Upon completion of the addition of the a~ueous mix, the reaction was allowed to subside over 3 hours.

Four surfactant compositions were prepared and employed. The first two compositions were outside the scope of this invention while the latter two were within the scope of this invention. All the compositions consisted of a mixture of two alkyldiphenyl ether sulfo-nates. The first composition, Control A, consisted of 100 percent monoalkyldiphenyl ether sulfonate. The sécond formulation, Control B, consisted of an 80:20 mixture of mono- and dialkyldiphenyl ether sulfonates.
The third and fourth formulations,~Examples 1 and 2, consisted of 50:50 and 20:80 mixtures, respectively, of mono- and dialkyl diphenyl ether sulfonates. In each composition, the alkyl substituents (R) were branched C12 tetrapropylene radicals, the counterion SM~) was sodium, and the degree of sulfonation (~x~y)) was equal to or greater than 1.7.

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Various tests and measurements were made upon the microsuspensions prepared with the various surfactant compositions and -the data is reported in Table I.

TABLE I
SALT AND MECHANICAL STABILITY OF A
STYRENE-BUT~DIENE MICROSUSPENSION
STABILIZED WITH VARIOUS ALKYL
DIPHENYL ETHER SULFONATES
.

Par- -10ticle Con/ mono /di- Surfactant Stability Size Ex. ratio (Total moles) Salt Mechanical (A) A 100/0 0.062 0.5 3.85 1090 B 80/20 0.06 0.5 0.25 1070 15l 50/50 0.055 >25 0.1 1250 2 20/80 0.047 >25 0.02 1740 ; Salt stability was measured by adding milliliters of a 10 percent solution of sodium chloride to a 25 g sample of microsuspension until there was evidence of agglomera-tion. Accordingly, the numbers in the salt stability column of Table I express a quantity in milliliters of the 10 percent sodium chloride solution that was added to the 25 g microsuspension sample to cause agglomera~
tion. The larger the number, the more salt stable the microsuspension.

Mechanical stability was measured by stirring a 200 g sarnple of microsuspension on a Hamilton Beach mixer for 20 minutes at high speed. The microsuspension was then filtered through a 100 mesh (0.149 mm opening) screen to gather the residue (grams of waste). Accordingly, ,, ~
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the figures in the mechanical stability column of Table I
represent the grams of waste collected on the 100 mesh (0.149 mm opening) screen. All controls and examples were run at essentially the same high speed. Here, the smaller the number, the more mechanical s-table the micro-suspension.

Comparison of the control data to the example data exhibits the improved properties of this invention.
The mechanical stability and the salt stability increased as the concentration of the dialkyldiphenyl ether sulfo-nate increased in the surfactant composition. Thls increase was achieved despite a reduction in the total moles of surfactant composition used. Also of note is the increase in particle size with the increase of dial-kylate content in the surfactant composition.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Method of imparting salt and /or mecha-nical stability to an aqueous polymer microsuspension by admixing with the microsuspension a stabilizing amount of a mono- and dialkyldiphenyl ether sulfonate surfactant composition, characterized in that at least 35 weight percent of the composition is at least one dialkyldiphenyl ether sulfonate of the formula (I) wherein:

each R is an alkyl radical and each R can be the same or different, each M? is a hydrogen, alkali metal ion, alka-line earth metal ion or ammonium ion and each M? can be the same or different, and x and y are individually 0 or 1 with the pro-viso that the average value of .SIGMA.(x+y) for all (I) is at least 1.7.
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2. The method of Claim 1 wherein M? is an alkali metal ion.

3. The method of Claim 2 wherein R is an alkyl radical of between 10 and about 18 carbon atoms.

4. The method of Claim 3 wherein M? is a sodium ion.

5. The method of Claim 1 wherein at least 50 weight percent of the composition is (I).

6. The method of Claim 1 wherein the composition is present in an amount of at least 0.05 weight percent of the microsuspension.

7. The method of Claim 1 wherein the composition is present in an amount of at least 0.5 weight percent of the microsuspension.

8. The method of Claim 1 wherein the microsuspension comprises polystyrene or polystyrene-butadiene polymers.

9. The method of Claim 1 wherein the composition is admixed with the microsuspension as a post-additive.

10. The method of Claim 1 wherein the composition is admixed with the polymer microsuspen-sion precursor.

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