CA1038988A - Low shrink water extended vinyl ester resin emulsion - Google Patents

Abstract

ABSTRACT
This invention concerns a water-in-resin emulsion. The resin phase comprises a mixture of 1) a terminally unsaturated vinyl ester resin prepared by reaction of a polyepoxide with an ethylenically unsaturated monocarboxylic acid, 2) a copolymerizable alkenylaromatic monomer, and 3) from 0.5 to 20 weight percent of a copolymer of a monoalkenylaromatic monomer, an alkyl acrylate or methacrylate, and optionally a hydroxyalkyl acrylate or methacrylate, which copolymer is soluble in the resin phase.
The copolymer serves as a dimension control agent to reduce shrinkage during curing of the emulsion.

Description

- ~038988 This invention concerns a water-in-re~in emulsion which can be cured, and if desired, dewatered after curing.
Vinyl ester resins, prepared by reaction of a polyepoxide with an ethylenically unsaturated mono-carboxylic acid, are now known to form water-in-resin emul~ions without the aid of an emulsifier. To as~i~t in dewatering the cured emulsion without cracking os splitting, it i9 ~ncwn to use certain nonionic ~urfactants in the emulsions. It is also known to add certain polymers which are insoluble in either phase of the emulsion to obtain dimensional control.
~ he pre~ent invention provides a water-in-resin emulsion which comprisesJ by weight from 20 to 80 per-cent of a di~persed aqueous phase and from 80 to 20percent of a continuous resin phase which compri~es a mixture of from 30 to 80 percent of a terminally un-- saturated vinyl ester resin prepared by reaction of - a polyepoxide with an ethylenically unsaturated mono-carboxylic acid and from 70 to 20 percent of a co-polymerizable aIkenylaromatic monomer, characterized in that the emulsion contains from 0.5 to 20 percent, preferably 5 to 15 percent, based on the weight of the emulsion, of a dimension control agent which is soluble in the re~in phase and which consi~t~ of a co-polymer of a) from l to 70 percent, preferably 50 to 70 percent, of a monoal~enylaromatic monomer, b) from l to 60 percent, preferably lO to 60 percent, of an aLkyl (Cl_l2) acrylate or methacrylate, and c) from 0 to 50 percent, - 30 preferably lO to 50 percent of a hydroxyalkyl(C2 63 acrylate of methacrylate.

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. ,- ~ . ~ ., ~ ~038988 The density of the cured emulsion may range from 15 to 50 lbs/cu. ft. (240-800 kg./m.3) if it is dewatered and from 40 to 180 lbs/cu. ft. (640-2880 kg./m.3) if not dewatered. The densities also vary depending on the resin components and their propor- -tions, and whether additives such as fillers are used.
The amount of the aqueous phase varies from about 20 to 80 weight percent with a preferably upper level of about 60 percent and a preferably lower level of about 40 percent. The balance to make lO0 percent - comprises the mixture of the vinyl ester resin and mono- ~-mer a~ the continuous resin phase. The weight propor-tions of re~in to monomer may vary widely, but u~ually range from about 80:20 to 30:70, respectively and pre-; ferably 70:30 to 50:50.
The emulsions are useful in making castings such as wall decorations or statuary, and in the de-;, . .
- watered ~tate have many of the characteristic~ of woodand are useful in making articles such as furniture, building panels, or ca~inet doors. ~he cured emulsions can be sawed, painted, nailed, stapled, or drilled.
- The emulsions are also useful as soil stabilizers and for surfacing canals, ponds, etc. to prevent 1088 of 'r 25 liquid by seepage and the like.
The monomers employed ~or preparing the di-mension control agent are well known and typically in-clude styrene~ vinyltoluenes a-methylstyrene~ halo-; genated styrenes such a~ chloro or ~romo styrene~ a}kyl substituted styrenes such as t-~utylstyreneS hydroxyethyl, !-16,555-F -2-, - .- : . . ::
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hydroxypropyl, hydroxybutyl and like e~ters of acrylic and methacrylic acia where the hydroxy group is usu-ally a 2-hydroxy group; and alkyl esters, which in-clude the cycloalkyl esters, of acrylic and methacrylic S acid.
The resin soluble copolymer may be prepared by any of the known vinyl polymerization methods, e.g., bulk, solution, or emulsion polymerization. Bulk or solution method are preferred herein. ~he copoly-mers are generally prepared by heating the monomers together in the presence of a free radical catalyst such as a peroxide, a persulfate, or a diazo compound.
The emulsions may be made by combining the various components in any convenient order. usually the copolymer along with the catalyst (and surfactant if used) is dissolved in the resin phase followed by combination with the water under agitation to form a creamy emulsion. As with any emulsion, stability is dependent on applying su~ficient shear in its prepara-tion to form small droplets of the dispersed phase (water, in this instance). Generally, a droplet or particle size of 10~ or less is preferred. Howe~er, stsble emul~ions with dispersed particle sizes up to 20-50~ and even larger may be prepared. A variety of mechanical agitating, stirring or homogenizing devices are well known to the trade for the preparation of such emulsions. ~he temperature of emulsification ~ can vary widely, but is usually between 30 and 140~F. ~-: (1-6~C.).

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~L038988 Various other material~, such as inert fillers (kaolin clay, silica), glass fibers, mold release agents, - surfactants, thickening agents, or pigments, also may be added. Desirably, accelerators or promoters, such ; 5 as dimethyl aniline, dimethyl toluidine, or metal naph-thenates, are frequently used and should be added last ;
to the emulsion since an accelerated cure may take only a few minutes. Small amounts of paraffin wax assist in providing tack free surfaces by concentr~ting at the surface and excluding air. Vinyl e~ter resins are prepared by reacting about equivalent quantities of an unsaturated monocarboxylic acid, such as methacrylic ~ - -acid, with a polyepoxide resin. With methacrylic acid ; and a diglycidyl ether of bisphenol A, the vinyl ester resin has the formula ~2 = C - CC~2C~C~2o ~ C~Ca3)2 ; _ _ 2 ;
Thus the vinyl ester resin is characterized by having terminal vinyl groups as opposed to acid or hydroxyl groups found in polyester resins.
Such resins which are her~in called vinyl ester resins are described in U.S. Pat. ~o. 3,~67,992 where the unsaturated monocarboxylic acid i~ an a--hydroxyal~yl acrylate or methacrylate half e~tQr of -;
a dicarboxylic acid; in U.S. Pat. No. 3,066,112; in -U.S. Pat. No. 3,179,623; in U.S. Pat. ~o. ~,256,226 where the molecular weight of the polyepoxide i8 in- -3~ creased by reaction of same with a dtcarboxylic acid~

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, ,~038988 in U.S. Pat. No. 3,301,743; and in U.S. Pat. No.
3,377,406.
A variety of polyepoxide resins may be used in the preparation of vinyl ester resins. Use-ful polyepoxides include polyglycidyl ethers of poly-hydric phenols and polyhydric alcohols, epoxy novo-lac resins, epoxidized diolefins or fatty acid~ or drying oils provided the polyepoxide contains more than one oxirane group per molecule. The polyepoxide~
also include those wherein the molecular weight is increased by reaction with a difunctional compound such as a dicarboxylic acid.
Preferred polyepoxides are the polyglycidyl ethers of polyhydric phenols and polyhydric alcohol~, the epoxy novolac resins and mixtures thereof wherein the epoxide equivalent weight m~y vary from 150 up to 2000.
Unsaturatea monocarboxylic acids u~eful in preparing vinyl ester resins include acrylic acid, ;: 20 methacrylic acid, haloqenated acrylic or methacrylic acid, cinnamic acid, and mixtures thereof. Al~o in- ~`
- cluded are the 2-hydroxyalkyl acrylate or methacry- ;
late half esters of dicarboxylic acids wherein the hydroxyalkyl group prefera~ly has from two to six carbon atoms. Typical half esters include the 2--hydroxyethyl acrylate half ester of maleic acid, and the 2-hydroxypropyl methacrylate half e~ter of phthalic acid. Either ~atUrated or unsaturated dicarboxylic acid half e~ters may be used. Con- ~
veniently the half e~ters are prepared by reactin~ ; -, : . ~,:

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' 1~38988 about 1 mole of a dicarboxylic acid anhydride. Further details may be found in U.S. Pat. No. 3,367,992.
- Various catalysts may be used in the preparation of vinyl ester resin~. Catalysts include tertiary amines such as 2,4,6-tris(dimethylaminomethyl)phenol, onium catalysts, ;
triphenyl stibine, triphenyl phosphine, and CrO3. Usually hydroquinone or other like polymerization inhibitor i~
added to prevent polymerization during the preparation of the resin.
Also included within the definition of Yinyl ester resins are those vinyl ester resins which have ~een further reacted with a reactant such as a dicarboxylic - acid anhydride wherein said anhydride reacts with the hydroxyl group formed in the first step reaction of the monocarboxylic acid with the polyepoxide resin (see prior vinyl ester resin formula). The proportions of anhydride may vary from 0.05 to 1.2 moles if necessary per mole of hydroxyl group. These modified vinyl ester resins have greatly improved corrosion resistance among other properties.
Alkenyl aromatic monomers include all the mono-alkenyl aromatic monomers previously described and other : like monomers. For certain purposes it may be desirable to employ at least in part, a polyalkenyl aromatic monomer such as divinyl benzene. ~enerally, the preferred monomer is styrene. Up to 25 percent of the aromatic monomer may be replaced by a hydroxyalkyl acrylate or methacrylate monomer.
While the emulsions may be cure~ by exposing them to ionizing radiation, more frequently it is ad-vantageous bo add a free radical generating catalyst, ~6,555-F -6-.
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usually to the resin pha~e before emuleification, and heat to accelerate the cure of the emulsion~ A variety of æuch catalysts are available including peroxides, persulfates, and azo catalysts. Benzoyl peroxide, lauroyl peroxide, t-butyl hydroperoxide, ~-butyl perbenzoate, methyl ethyl ketone peroxide, potassium persulfate, and azobisiso-butyronitrile are typical. Normal catalyst levels range from 0.1 to 5 weight percent, and the emulsion may be cured at temperatures up to 200F. (93C.) or even higher. More rapid curing may be obtained by adding accelerating agents - such as lead or cobalt naphthenate or N,N-dimethylaniline.The dewaterability of the cured emulsion may be significantly improved by the addition of a polyethylene oxide--polyalkylene oxide block copolymer nonionic surface active agent wherein the hydrophobic group has a molecular weight of at least about 1000. Suitable surfactants include thoqe described by I. R. Schmolka, Chapter 10, "Nonionic Sur-factantsn, Vol. 1, edited by M. J. Schick and publi~hed by M. Dekker, Inc., N.Y. 1967. ~hese surfactants are also disclosed in U.S. 3,669,911.
The surfactant hydrophilic group ~i.e., the polyethylene oxide block segment) comprises from 44 to 90 percent of the weight of the surfactant, varying from 44 to 55 we~ght percent for monoinitiated heteric block sur$actants to 60 to 90 percent with difunctional initiated ;~
all block surfactant~. Preferred molecular weight for the former ~urfactants ranges from 1000 to 2000 while for the latter surfactants the preferred range is 1750 to 3250.

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10~8988 ' Very small amount~ of the nonionic ~urfactant, as little as 0.005 part per 100 parts of emul~ion, are effective. Much larger amounts up to 10 parts or higher may be used, but there is no advantage therefrom. Usually, 0.005 to 2 parts is sufficient.
Following cure of the resin emul~ion containing the surfactant, the thermoset resin may be dehydrated merely by standing at room temperature. ~ehydration i~ dependent on both temperature and thickness of the resin, for example, a 1 inch (2.5 cm.) thick resin might take about 15 days at 75F. (24C.) to dehydrate, but only takes 2 to 3 hours at 400F. (204C.). Temperatures up to 450-500~. (232-260C.) may be used if desired. Even at these elevated temperatures the thermo~et resins of this invention can be gubstantially dehydrated without cracking or damage to the resin. Vacuum conditions may also be u~ed in dehydrating the thermoset re~in.
` The following examples further illu~trate the invention. All parts and percentages are by weight unless otherwise specified. - -Example 1 A high mc~lecular weight polyepoxide resin was first made by reacting 32.1 parts of diglycidyl ether of ~7isphenol A having an epoxide equivalent weight (EEW) of 186-192 and 4.7 parts of an aliphatic polyepoxide having an EEW of 305-335 with 3.2 part~ of bisphenol A
in the presence of tetrabutylphogphonium acetate catalyst.
The reactant~ were heated with agitation at 150~C. for 1 hour. ~rhe temperature wag then lowered and 13.5 parts of methacrylic acid added along with a sma~l amount of 16,555-F -a- ; -.. ~ , .
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~038988 hydroquinone inhibitor and 2,4,6-tris(dimethylaminomethyl)-phenol catalyst. The reactants were then heated at 115-12QC.
until the weight percent of acid, as -COOH, reached about 1.2 percent. The resin wa~ cooled to 50C. and 45 parts of styrene monomer added. Then 0.1 part of a heteric poly-ethylene oxide-polyalkylene oxide block copolymer nonionic surfactant and 0.2 parts of paraffin wax were added. The total mixture will be called Resin A hereafter.
A copolymer was prepared by polymerizing a solution containing 70 parts styrene, 30 parts hydroxy-- propyl acrylate (HPA), 10 parts methyl methacrylate and : 1 part benzoyl peroxide at 140-150C. The resulting - terpolymer was dissolved in styrene (50 percent) and cooled.
~ water-in-resin emulsion was prepared by mixing - 15 14 Ibs. (6.3 kg.) of Resin A with 69 grams of benzoyl peroxide, 140 grams of styrene, and 1390 grams of said terpolymer solution. A clear liquid solution was obtained, ;~
to which 20.3 Ibs. (9.2 kg.) of water was slowly added with agitation. A smooth, white emulsion was prepared.
The emulsion was divided into six smaller por-tions and poured into cabinet door molds, 12 x 16 x 5/8"
(30 x 40 x 1.56 cm.). N,~-Dimethyl-p-toluidine (0.2 per-cent) was added to accelerate the room temperature cure ; of the emul~ion. Each of the parts were demolded in about 10 minutes and placed in a 390-410F. (199-210C.) forced draft oven for a~out 1.5 hours. After cooling, the parts were determined to have lost 50.6-55.6 percent ~f their weight. The linear shrin~age for each of the parts was zero percent.

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,103898~ ' Using the same resin without the terpolymer, the emulsion shrunk 3.44 percent when cured and dried as above. Essentially no shrinkage was found when the ; terpolymer content of the emulsion was increased from about - 5 4 percent, above, to 9.9 percent. (The water content was kept constant at 55 percent.) Example 2 A series of emulsions at a 50 percent water content was prepared similar to Example 1. The weight percent terpolymer was varied and the dimensional change ; after dehydration was determined.
Wt. % % Dimensional - Terpolymer Change ; ;
A 4.6 -1.0 B 8.4 +0.3 ', C 10 . O O
D 11.6 +2.0 - E 14.4 +2.3 Example 3 Tests similar to Example 2 were made except that the emulsions were cured at 98-102F. (36.6-38.8~C.) rather than at room temperature.
Wt. % % Dimensional Terpolymer Change F 7.2 -1.2 - G 8.4 -1.0 H 11.6 +0.5 I 12.6 +0.3 J 1~.4 +0.8 ' .
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1~38~88 Example 4 Similar results as above were obtained using a different preparative method. The copolymer was first - prepared in the presence of the polyepoxide resin used to form the vinyl ester resin. The polyepoxide resin (as in Example 1) was charged to a two-liter kettle and heated to 130C. under agitation. A solution containing 60 percent styrene, 40 percent isobutyl acrylate, and 1 percent benzoyl peroxide was added incrementally o~er 1-2 hours and then heated to l~O~C. to deactivate the ~ -peroxide. ;-~
After cooling to about llO~C., a stoichiometric ~ -amount of methacrylic acid to react with the epoxide groups ~ -was added. Reaction was continued until the acid content had dropped to a~out 1 percent. Then about 45 percent - styrene was added and the resin cooled. The surfactant was then added. A clear resin containing 10 percent co-polymer was prepared. An emul~ion was then prepared ~imilar to Example 1, cured and dehydrated with zero shrinkage.

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Claims (9)

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

1. A water-in resin emulsion which comprises, by weight, from 20 to 80 percent of a dispersed aqueous phase and from 80 to 20 percent of a con-tinuous resin phase which comprises a mixture of from 30 to 80 percent of a terminally unsaturated vinyl ester resin prepared by reaction of a poly-epoxide with an ethylenically unsaturated monocarboxylic acid and from 70 to 20 percent of a copolymerizable alkenylaromatic monomer, characterized in that the emulsion contains from 0.5 to 20 percent, based on the weight of the emulsion, of a dimension control agent which is soluble in the resin phase and which consists of a copolymer of a) from 1 to 70 percent of a monoalkenylaromatic monomer, b) from 1 to 60 percent of an alkyl(C1-12) acrylate or methacrylate, and c) from 0 to 50 percent of a hydroxyalkyl (C2-6)acrylate or methacrylate.

2. An emulsion as defined in claim 1 wherein the dimension control agent is present in an amount of from 5 to 15 percent.

3. An emulsion as defined in claim 1 or 2 wherein the proportion of the monoalkenylaromatic in the dimension control agent is from 50 to 70 percent.

4. An emulsion as defined in claim 1 or 2 wherein the proportion of the alkyl acrylate or methacrylate in the dimension control agent is from 10 to 60 percent.

5. An emulsion as defined in claim 1 or 2 wherein the proportion of the hydroxyalkyl acrylate or methacrylate in the dimension control agent is from 10 to 50 percent.

6. An emulsion as defined in claim 1 wherein the dimension control agent is a copolymer of styrene, methyl methacrylate, and hydroxypropyl acrylate.

7. An emulsion as defined in claim 1 wherein the dimension control agent is a copolymer of styrene and isobutyl acrylate.

8. An emulsion as defined in claim 1 or 2 wherein the copolymerizable alkenylaromatic monomer of the resin phase is styrene.

9. An emulsion as defined in claim 1 or 2 wherein the resin phase contains, in addition, a nonionic polyethylene oxide-polyalkylene oxide block copolymer.surfactant.