CA1068030A - Process for the manufacture of plastics dispersions - Google Patents

Abstract

PROCESS FOR THE MANUFACTURE OF PLASTICS DISPERSIONS
Abstract of the disclosure:
Plastics dispersions are described which impart high wet adhesion to paints formulated therewith. The dispersions are obtained by copolymerizing A) from 5 to 50 % by weight, preferably from 15 to 35 % by weight, relative to the total amount of monomers, of vinyl esters of saturated branched monocarboxylic acids having from 5 to 20, preferably from 5 to 11 carbon atoms, the carboxyl groups of which are directly linked to a tertiary or quaternary car-bon atom, B) from 40 to 94.5 % by weight of vinyl acetate, vinyl propio-nate and/or vinyl isobutyrate, C) optionally from 0 to 30 % by weight of other alpha-beta-un-saturated compounds copolymerizable with the above monomers, and D) from 0.5 to 10 % by weight of an acetoacetic acid ester of the formula

Description

~IOE 75/~ 202 i~80~
This in~Jention relates to a process for the manufacture of plastics dispersions suitable for making dispersion paints hav-ing a good w~ adhesion, i.e. when wetted after drying.
The problem of the wet adhesion, i.e. the adhesion of dried ~aints on wettinq, of dispersion paints on smooth non-absorbent surfaces has limited for a long time the use of such dispersion paints. Dispersion paints having a low pigment content, which dry on the substrate with formation of a glossy or slightly dull ; film, have a poor adhesion to smooth non-absorbent surfaces when the paints are rewetted after drying. The wet adhesion is es-pecially unsatisfactory with fresh paints which have not yet undergone ageing.
Diæpersion paints of low pigment content are chosen when a washable coat of paint is desired. Owing to the high binder content of the paint a closed washable film is formed. Disper-sion paints drying with formation of a glossy or slightly dull film also have a concentration by volume of pigment of less than 40 %, generally the concentration is in the range of from about 10 to 25 %. They also c~ntain about 3 to 20 % of oryanic solvents to improve the gloss and flow, to prolong the working time and for film consolidation, for example polyhydric alcohols miscible with water and having up to 6 carbon atoms, especially ethylene and propylene glycol, or the monomethyl to monobutyl ethers thereof. To improve the film consolidation solvents having a restricted solubility in water are used, such as the monoglycol ethers of carboxylic acids and more particularly e~ters of carb-oxylic acids with monoal~syl ethers of glycols or oligoglycols. ~-Butyl diglycoi acetate is one of the most widely used represen-

2~ tatives of this group. The combination of a low pigment content with a ",! 2 - ~

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_E 75/F 202 ~0~8030 relatively high solvent content has a very detrimental effect on the wet adhesion of the coats of dispersions paints.
With a poor wet adh~sion paints formulated to give wash-able coats do not have this property when applied to smooth non ahsorhent surfaces, for example old coats of alkyd or oil paint.
In moist rooms, such as kitchen, bath rooms, or industrial places, where water of condensation may form, the new coat may detach from the substrate if the wet adhesion is insufficient. More-over, a poor wet adhesion complicates painting. When, for ex-ample, the base and the upper half of a wall or the wall and the ceiling are to be painted in different colors, the first coat of paint may be soiled with the different paint by inaccurate handling of the brush. In principle, the different paint could be wiped off with a wet cloth or sponge, but with a poor wet adhesion the first paint may then be damaged or even removed simultaneously.
Therefore, many attempts have been made to modify plastics - dispersions in such a manner that the dispersion paints made therewith have the desired wet adhesion. In German Offenlegungs-schrift 1,595,501 it has been proposed to prepare plastics dis-persions by polymerizing suitable monomers in aqueous emulsion using as comonomers 0.2 to 15 % by weight, calculated on the total amount of the monomers, of compounds carrying oxirane groups and then to react the copolymer at room temperature with ammonia or an amine. Suitable oxirane compounds, are, above all, glycidyl esters of acrylic and methacrylic acid, allyl glycidyl ethers or vinyl glycidyl ethers.
Dispersion paints prepared with plastics dispersions of 2~ this type have quite a good wet ahesion, but for many applica-~ , - 10~803() tions the wet adhesion is not at all sufficient.
The present invention provides a process for the preparation of aqueous plastics dispersions suitable for the manufacture of paints having a high wet adhesion, and having a solids content of from 20 to 70%, by copoly-merization of the following monomers:
A) from 5 to 50% by weight, relative to the total amount of monomers, of vinyl esters of saturated branched monorarboxylic acids having from 5 to 20 carbon atoms, the carboxyl groups of which are directly linked to a tertiary or quaternary carbon atom B) from 40 to 94.5% by weight of vinyl acetate, vinYl pro-pionate and/or vinyl isobutyrate;
C) from 0 to 30% by weight of other olefinically unsaturated compounds copolymerizable with the above monomers; the im-provement which comprises using additionally D) from 0.5 to 10% by weight of an acetoacetic acid ester of the formula 0 0 R R' - .......... . , .
CH3 - C - CH2 - C - X - C = CH

where X is -0-, -0-CH2- or -0-CH2-CH -0-C- and O : ' .
R and R' each are H or CH3, in the polymerization.
It is particularly preferred to use from 1 to 5% by weight of D).
Compounds of the kind described sub D) are for example aceto-acetic acid vinyl or allyl ester, or acetoacetic acid esters of B-hydroxy-.

~0~803V

ethylacrylate or methacrylate or crotonatel or hydroxy-propyl-acrylate or meth-acrylate or crotonate. Preferably~ acetoacetic acid allyl ester is used since it yields the best results. It is preferred to use from 15 to 35% by weight of A).
Vinyl esters of saturated monocarboxylic acids the carboxyl groups of which are directly linked to a tertiary or 4uaternary carbon atom are preferably esters of monocarboxylic acids having from 5 to 11 carbon atoms, above all pivalic acid vinyl ester, isononanoic acid vinyl ester or, prefer-ably, versatic acid vinyl esters~ as described for example in British Patent Specification No. 993,470. Versatic*-10-acid vinyl ester is particularly pre-ferred. Also mixtures of such monomers may be used.
Suitable vinyl esters as cited sub B) are vinyl acetate, vinyl propionate, vinyl butyrate or vinyl isobutyrate, or mixtures of these compounds. Preferably, vinyl acetate is employed.
Alpha-beta-unsaturated compounds of the kind cited sub C) are for example acrylic, methacrylic, crotonic, maleic or fumaric acid or esters of acrylic, methacrylic or crotonic acid, di- or monoesters of maleic or fu-maric acid, the corresponding alcohol radicals thereof having from 1 to 30, preferably from 1 to 20 carbon atoms, or other derivatives of these acids such as (meth)acrylamide, (meth)acrylonitrile or maleic anhydride. When the copoly-merization of such monomers is intended, the generally acknowledged conditions for the manufacture of dispersions have to be considered. In the first place, care should be taken that polymers are formed which yield a coherent film under the drying conditions of the coat of paint and the monomers for making copolymers should be selected in such a manner that, depending on the respec-tive polymerization parameters, the formation of copolymers with the monomers bearing keto groups in accordance with this invention can be expected.

* Trade Mark ` ` 5 :~: , ~: ,:, ,: . : : , _OE 75/F 202 iO~803V
If clesired, se~reral of the compounds cited sub C~ may be used simul~aneously.
WheJI monomers yielding water-soluble poiymers on homopoly--merization are to be copolymerized, the amounts should be chosen in such a manner that the sensitivity to water of the disper-sion films or the paint films does not exceed the limits se~. -For example, (meth)acrylic acid, crotonic, maleic or fumaric acid, (meth)acrylamide or maleic anhydride should be copolymeriz-ed in amounts not exceeding 5 %, relative to the to.al amount of the monomers.
The aqueous plastics dispersionSare prepared with a solids content of from 20 to 70 %, preferably fxom 40 to 60 %. For the rest, the aqueous plastics dispersions are manufactured according to usual processes known to those skilled in the art.
Plastics dispersions are extremely complicated systems, and the manufacture of high-quality dispersionS according to the present invention requires the application of all experience existing in the field of emulsion polymerization, including that not particularly described in this specification. Ommission of the rules known to those s};illed in the art of emulsion poly-merization may adversely affect important properties, i.e. water resistance, of the dispersion films or paint films. Therefore, the dispersions should not substantially exceed the usual amounts of up to 3 ~, preferably up to 2 %, of ionic emulsifiers, or of up to 6 ~, preferably up to 4 %, of non-ionic emulsifiers, relative to the polymer content.
Suitable non-ionic emulsifiers are, for example, alkyl poly-glycol ethers such as the ethoxylation products of lauryl,oleyl 29 or stearyl alcohol or of mixtures such as coconut fatty alcoiol;

~, ' '',' . ~ ~ ' HO~ 75/~ 202 10f~8030 dik~l~phenol polygl-~col ethers such as the ethoxylation products of octyl- or nonyl-phenol, diisopropyl-phenol, triisopropyl-phenol or di- or tri-tert.bu~yl-phenol; or ethox~lation products of polypropylene oxide.
As ionic emulsifiers anionic emul~ifiers ar~ used in the first place, for example alkali metal or ammonium sal~s of alkyl, aryl or alkylaryl sulfonates, sulfates, phosphates, phosphona-tes, or compounds having different anionic end groups, oligo- or polyethylene oxide units possibly being contained between the hydrocarbon radical and the anionic group. Typical representa-tives are sodium lauryl sulfate, sodium octyl-phenol glycol ether sulfate, sodium dodecyl-benzene sulfonate, sodium lauryl diglycol su]fate, ammonium tri-tert. butyl-phenol penta- or octa-glycol sulfate.
As protective colloids there may be used natural substances such as gum arabic, starch, alginates, or modified natural sub-stances such as methyl, ethyl, hydroxyalkyl, or carboxymethyl cellulose, or synthetic substances, for example polyvinyl alco-hol, polyvinyl pyrrolidone, or mixtures of the aforesaid sub-20 -- stances. Modified cellulose derivatives and synthetic protective colloids are preferred.
To initiate and continue polymerization, oil-soluble and~or preferably water-soluble radical forming agents or redox systems .
are used, for example hydrogen perox-de, potassium or ammonium peroxydisulfate, dibenzoyl peroxide~ lauryl peroxide, tri-tert.
butyl peroxide, bisazodiisobutyronitrile, either per se or to-gether with reducing components,' for example sodium bisulfite, Rongalite( ), glucose, ascorbic acid, and other compounds hav-29 ing a reduc~:~g action.

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HOE /r/F 202 10~i8030 The dispersions pre~dL-~d according to the present invention have the special advantage of being suitable for ~he manufacture of gloss dispersior. paints having a good wet adhesion on non-absorbent substrates, and of displaying a high resistance to saponification.
The following examples illustrate the invention, the parts being by weight unless otherwise stated.
E X A M P L E 1:
A dispersion liquor consisting of 709 parts water 12 parts polyvinyl alcohol having a degree of hydrolysis of 88 mol %, and a viscosity of 18 cP at 20 C in a 4 aqueous solution thereof -0.9 part sodium vinylsulfonate 1.~ parts sodium dodecylbenzene sulfonate 15 parts nonylphenol polyglycol ether having about 30 ethylene oxide units 0.72 part NaH2PO4 2 H20 1.67 parts Na2HPO4 12 H2O
20 ~ 1.5 parts ammonium peroxidisulfate and 60 parts of a monomer mixture taken from a mixture of 300 parts vinylacetate, 150 parts 2-ethylhexyl acrylate, 150 parts pivalic acid vinyl ester and 18 parts acetoacetic acid allyl ester was heated while stirring in a 2 litex three-necked flasl placed in a heating bath and equipped with stirrer, reflu~ condenser, dropping funnel and thermometer, whereby the poly~erization was initiated. When the temperature had reached 90 C, addition of the remaining monomer was started.
29 Immédiately after termination of the monomer addition a solu-. , ~ ,.. . : ~ , . . .

~0~8~:)30 tion of 0.3 p~rt ammonium peroxidisulfate in 15 pa~ts water was added, heating of the polymerization miY.ture (70 C) was conti.-nued for 2 hours while stirring, and the batch was then slow]y cooled.
The dispersion obtained had a solids content of about 47.5 %.
E X A M P L E _:
Operations were exactly as described in Example 1; however, no acetoacetic acid ally]. ester was used for the polymerization.
E ~ ~ M P L E 3:
1~ In an apparatus as described in Example 1 a dispersion li-quor consisting of 618 parts water 18 parts oleyl polyglycol ether having about 25 ethylene oxide units 0.2 part sodium dodecylbenzene sulfonate 12 parts hydroxyethyl cellulose having an average degree of poly- . -merization of about 400 (molecular weight about 100,000) 1.5 parts sodium acetate : -2.5 parts ammonium peroxidisulfate and -20- 63 parts of a monomer mixture taken from a mixture of 450 parts vinyl acetate 150 parts isononanoic acid vinyl ester and 12 parts acetoacetic acid allyl ester was heated to 70~ ~ and the r~maining monomer mi~ture ~549 parts) was metered in within a period of 3 hours at this temperature.
When the addition was terminated 0.5 part ammonium peroxidisul-fate in 15 parts water were added and heating was continued for a further 2 hours. The dispersion had a solids content of 29 about 50 %.

HOE /5/F 20~
10~8030 E X A M P L E 4:
Operations were exactly as described in Example 3; however, no acetoacetic acid allyl ester was used for the polymerization.
E X A M P L E 5:
In an apparatus as described in Example 1 a di~persion liquor consisting of 657 parts water 18 parts nonylphenol polyglycol ether having about 30 ethylene glycol units 12 parts polyvinlyl alcohol having a degree of hydrolysis - of 88 mol % and a viscosity of a 4 ~ aqueous solution of 18 cP at 20 C
0.9 part sodium vinyl sulfonate 1.5 parts sodium acetate 2.5 parts ammonium peroxidisulfate 48 parts vinyl acetate and B 12 parts Versatic-1OC-acid vinyl ester was heated to 70 C and at said temperature there were added within a period of 3 hours a mixture of 432 parts vinyl acetate 20 ~ and 108 parts Versatic-lOC-acid vinyl ester and 9 parts acetô-acetic acid allyl ester.
When the addition was terminated 0.5 part ammonium peroxidi-sulfate in 15 parts water was added and the dispersion was heated for a further 2 hours. Tne dispersion had a solids content or approximately 49 ~.
E X A M P L_E 6: -Operations were exactly as described in Example 5; however, no acetoacetic acid allyl ester was used for the polymeri~ation.

~ e ~k . . . . ................. . . .

. .. . . . .. - . . .

HCE 75/F 20, 10~8030 E ~ A M P I. E 7:
In an ap?ar~tus as described in Example 1 a dispersion liquor consisting of 62~ parts water 18 parts nonylphenol polyglycol ether having about 30 ethylene oxide units 1.5 parts sodium acetate 12 parts hydroxyethyl cellulose having an average degree of polymerization of about 400 (molecular weight about 100, 000) ~, -2.5 parts ammonium peroxidisufate and 60 parts of a monomer mixture prepared from 396 parts vinyl ~ -acetate, `
B 150 parts ~ rsatic-10C-acid vinyl ester, 48 parts butyl acrylate, 18 parts acetoacetic acid allyl ester and ~ .
6 parts crotonic acid ::- :
was heated to 70 C and at said temperature there were added, within 3 hours, the remaining monomer mixture (558 parts).
When the addition was terminated 0.5 part ammonium peroxidic sulfate in 15 parts water was added and the dispersion was heated for a further 2 hours. The dispersion had a solids content of about 50 ~. .
E X A M P L E 8:
Operations were exactly as described in Example 7; how-ever, no aceto-acetic acid allyl ester was used for the poly-merization.
To prepare the dis?ersion paints having a hlgh wet ad-29 hesion the dispersions obtained according to the preceding ex- ~.

- . ... . ... . . . . . ................... . . ; .. .

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HOE 75~F 202 1068~130 amples were blended ~ith a pigment suspension. Pigm~nt suspen-sions or pigm~nt pastes of this type, which are suitable for making dispersion paints of low pigment content and especially gloss paints consist, for examp~e, of titanium dioxide uniformly ~ispersed in water. They contain, in ~eneral, protective colloids such as cellulose derivatives, for example hydro~yethyl cellulose, and dispersing agents, for example salts of poly(meth)acrylic acid or sodium polyphosphate. Usual constituents of pigment sus-pensions are furthermore antimicrobic preserving agents, anti-foaming agents, pH stabilizers and fillers. Especially suitable titanium dioxide pigments are the rutile and anatase modifica-tions. For the manufacture of gloss paints the average particle diameter of the pigment should be near the lower limit of the light wave length, i.e. at about 0.4 to 0.2 micron. For making dull paints of low pigment content special large surface silicate pigments could be concomittantly used. Dull paints of high binder content yield paint coatings that are easily to clean.
The pigment paste may, of course, also contain colored pigments or the desired shade is obtained by adding a shading dyestuff to the dispersion paint containing the white pigment.
The pigment suspension can be prepared in known manner, for example by dispersing the pigment in a dissolver, a ball mill or sand mill. For use in gloss paints the pigment suspen-sion should not contain noticeable amounts of pigment aggregates which would affect the gloss.
Auxiliaries such as plasticizers, cross linking agents, buffer substances, thickening agents, thioxotropic agents, rust preventing agents, alkyd resins, or drying oils may be added-2~ to the disperion or the finished dispersion paint. Suitable ., . , : .- ~: : : , - -. - ~ -: . ` ~ : , ::

HOE 75/~ 202 10~i8~30 plasticl~ers are not the solvents initially mentioned as film consolidation agen~ having a ter.~porary action only but compounds which reduce the rilm~forming temperature and remain in the poly-mer for a longer period of time, for example dibutyl phthalate.
To test the wet adhesion gloss paints were prepared accord-ing to the follo~ing formulations:
Formulation I:
1. 41.0 parts water 15.6 parts of a 3 ~ aqueous solution of Tylose(R) H 20 0.4 part Calgon( ) N (solid~

3.0 parts dispersing agent PA 30 1.O part ammonia of 25 ~ strenyth 2.0 parts of preserving agent 3.0 parts of anti-foaming agent 175 parts of titanium dioxide having a particle size of from 0.2 to 0.4 micron 10.0 parts 1,2-propylene-glycol were dispersed and then 2. 710 parts of the respective dispersion (with a solids contents of 50 %1 which had been admixed with 2.0 parts ammonia of 25 % strength if the pH did not exceed approximately 7I were added.
Subsequently a mixture 3. of 10 parts butyl diglycol acetate and 27.0 parts 1,2-propylene-glycol was slowly added while stirring.
The liquid or soluble components indicated sub 1., with the exception of the 1,2-propyleneglycol, were introduced in the 29 cited sequence into a vessel provided with stirrer, and the pig-,.: - - - ,.
-:: . . - :

.. : ~ . , , :

OE 75/I~_,02 10~030 ment was then disperse~ in this mixture by means of a dissolver.
Subsequentl~, I,'-propylene~lycol was added. In order to ensure identical conditions for mi~ing w~th the different dispersions to be tested, for example in view of pi~ment dispersion, a large amount of this pigment paste was manufactured.
Formulation II:
. _ Formulation II dif~ered from Formulation I by a larger amount of organic solvent, that is, a mixture of 53 parts 1,2-propyleneglycol and 17 parts butyldiglycol acetate was added to the paint.
Formulation III:
Formulation III differed from FGrmulations I and II by a still larger amount of organic solvents, that is, a mixture of 68.7 parts 1,2-propyleneglycol and 21.3 parts butyldiglycol acetate was added to the practically finished paint.
Formulation IV:
Formulation IV differed from Formulation I by a varied composition of the solvent mixture added to the practically finished paint (process step 3 of paint manufacture); that is, 20- a mixture of 12.4 parts 1,2-propyleneglycol, 4.~ parts butyl-diglycol acetate and 20 parts 2,2,4-trimethylpentanediol-1,3-B monoisobutyrate-1 (trade ~nm~: F xanol) was addéd to the paint.
For the manufacture of the individual paints a correspond-ing proportion of the pigment pas-tes was mi~ed according to ~he process of _he above formulation~ while 510wly stirring, with the dispersions approximately one day old, whereupon the solvents mentioned sub 3 were added. After complete confection, the paints were passed through a sieve.
29 These gloss paints were allowed to stand for one day and .

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. . . . . ...
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- . .. : . .

~O~ l;/E` 20~

1~803g then spread on glass plates and steel slleets onto which a pig-mented gloss~ alr-.lr~ing alkyd resin enamel had been sprayed and which had been acJed ~fter drying for 24 hours at 100 C.
A film applicat^r was used having a slit diameter of 200 mic-rons. After a drying period of 24 hours the wet adhesion ofthe gloss paints was tested according to the two following methods:
1) Abrasion _est:
The glass plates with the dried coating of dispersion paint were inserted in a mechanical abrasion device as described, for example, in German Offenlegungsschrift 2,262,956 and similar to the Gardner Washability and Abrasion Machine, but having a moving length of approximately 1.20 m in a manner such that the applied films of dispersion paint were in a vertical posi-tion with respect to the moving direction of the brush. Dueto the long moving distance about 15 paints could be simultane-ously tested in one run. A brush with hog's bristles was used which, at the beginning of the test, had been wetted with distil-led water. During the test the area on which the brush moved was also wetted with distilled water so that the brushed areas were permanently covered with a water film. With a poor wet adhesion the dispersion paint was brushed off the substrate after a few movements of the brush and torn at the boundary between wetted and dry film. The wet adhesion is the better the higher the number of movements of the brush until the film is sAifted aside. The dispersion paint has an optimum wet adhesion when in the wetted area the film is not damaged after 5,000 passages of the brush, onepassage including a backward and forward stroke.

.. .. . . . .

~OE 73~ 2 la~030 2) Condensatiorl test:
A rectangular therm~stat was used one hal$ of which was filled with water of 50 C and in the gas space of which above the water level a fan was mounted. The upper opening was -ov-ered w~th the ~t~ h~ts with the coated surface in downwardposition so that the thermostat was closed. The thermostat was kept in a room maintained at 23 C. Owing to the temperature dif-ference steam condensed on the lower surface of the sheets and acted on the coats of paint. After 15 minutes of action the sheets were removed and the coatings evaluated.
With an unsatisfactory wet adhesion blisters form between the film of dispersion paint and the alkyd resin lacquer and the film can be easily shifted aside, for example, with the finger-tip. A film having a good wet adhesion is still free of blisters after a period of 6 hours and cannot be shifted.
The test results are listed in the following Table.
.

.

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.. . .... .

~J /~ 2~2 1CI~;8~30 Survev of tes- resu.~s Example Formul~tion Abrasion test,number Stability in con-No. No.of double strokes ofdensation test ; brush 1 II~ 5000 ~ 6 hrs.
IV> 3000 ~ 6 hrs.
_._ 2* II 500 30 min.
IV 450 25 min.
3 II~ 5000 > 6 hrs.
5000 ~ 6 hrs.

4* II 250 < 15 min.
I ~ 5000 ~ 6 hrs.
. .
6* I 120 30 min.
.. . . . .
7 I ~ 5000 ~ 6 hrs.
8* I 500 2 hrs.
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~ * Comparative Examples not in ac~ordance with this invention ~: ~
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Claims (6)

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

1. In a process for the preparation of aqueous plastics disper-sions suitable for the manufacture of paints having a high wet adhesion, and having a solids content of from 20 to 70%, by copolymerization of the follow-ing monomers:
A) from 5 to 50% by weight, relative to the total amount of monomers, of vinyl esters of saturated branched monocarboxylic acids having from 5 to 20 carbon atoms, the carboxyl groups of which are directly linked to a tertiary or quaternary carbon atom;
B) from 40 to 94.5% by weight of vinyl acetate, vinyl pro-pionate and/or vinyl isobutyrate;
C) from 0 to 30% by weight of other olefinically unsaturated compounds copolymerizable with the above monomers; the improvement which com-prises using additionally D) from 0.5 to 10% by weight of an acetoacetic acid ester of the formula where X is -O-, -O-CH2- or -O-CH2-CH2-O-?- and R and R' each are H or CH3, in the polymerization.

2. The process as claimed in Claim 1, which comprises as D) 1 to 5% by weight of the acetoacetic acid ester.

3. The process as claimed in Claim 1 or 2, wherein the aceto-acetic acid ester is allyl acetoacetate.

4. The process as claimed in Claim 1 or 2, wherein the amount of A) is from 15 to 35% by weight.

5. The process as claimed in Claim 1 or 2 wherein the monocar-boxylic acid moiety of A) has from 5 to 11 carbon atoms.

6. The process as claimed in Claim 1 or 2, wherein the amount of A) is from 15 to 35% by weight, and the acetoacetic ester is allyl acetoacetate.