CA1175830A

CA1175830A - Process for preparing n-substituted acrylamides and methacrylamides

Info

Publication number: CA1175830A
Application number: CA000407528A
Authority: CA
Inventors: Karlheinz Laping; Olaf Petersen; Karl-Heinz Heinemann; Heiko Humbert; Friedrich Henn
Original assignee: Deutsche Texaco AG
Current assignee: Wintershall Dea International AG
Priority date: 1981-07-20
Filing date: 1982-07-19
Publication date: 1984-10-09
Also published as: DE3262545D1; JPS5818346A; EP0070425B1; DE3128574C2; JPH0343262B2; EP0070425A1; DE3128574A1

Abstract

ABSTRACT
The invention relates to a process for preparing N-substituted acrylamides and methacrylamides which com-prises reacting acrylamide or methacrylamide, as the case may be, with an amine reactant, decomposing the formed reaction product, and separating out and removing the formed N-substituted acrylamides or methacrylamides by dis-tillation means.

Description

~ 31 7 ~

DESCRIPTION O~ TEIE ART
There are in the prlor art severaL known processes for preparincJ ~1-substi-tuted acrylamides. A great n~lber of these processes are describecl in de-tail in European Pa-ten-t Application No. 0 013 416 (published on 7/24/80).
Acrylic esters and acrylamides are often the starting material employed to prepare these N-substituted acrylamides and methacrylamides in a great number of these processes. And, to protect the double bond of these acrylic or meth-acrylic acid derivatives, water, an alcohol or an amine are reacted with the same, breakin~ the double bond and attaching a protective ~roup to the termi-nal carbon atom. Af-ter the preparation oE the desirecl amLde, th~3 ~)rotectLve ~roup is then split ofE.
There are, however, problems with empLoying subst:ituted carboxyllc acid derivatives such as 3-hydroxy or 3-alkoxy-substituted carbo~ylic acid amides as starting ma-terials in the prepara-tion of N-substituted acrylamides or methacrylamides as compared to 3-amino carboxylic acid derivatives. Where they are employed, such as in German ~atent Applications 2 819 735 (published on 11/8/78), 2 856 383 (published on 7/3/80), 2 911 642 (published on 9/25/80),

2 836 520 (published on 2/28/80) and 2 918 486 (published on 11/13/80) which are open for public inspection and in European Application 0 013 416, there are problems in that 3-hydroxy- or 3-alkoxy-substituted carboxylic acid amides are not easily formed; they are, in fact, formed in a complicated multi-stage process.
There are also problems when an ester is employed; for example, in DE OS 2 623 838 (published on 12/15/77), where as a J ~
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~ 175~3(~

starting material a 3-alkoxy propionic ester is employed, the ester i5 prepared in a separate process apart from the main reaction sequence~
As disclosed in DE-AS 2 816 516 an additional - problem is disclosed in employing esters as a startiny material. From the beginning of the reaction, the ester ~w ,: . .
must be present in a larg~ enough amount so that despite distillation losses an excess amount of ester is maintained in the reaction. If when forming the amide not enough ester is present, the ester must be continuously added to the reaction with the charying of the amine. In addition, total reflux cannot be employed because the split-off alcohol which wou}d form as a result cannot be removed ErQm the reaction mixturc. ~d finally, the distilled off ester-alcohol mixture must be worked up.
Not only are there problems with employing these

3-hydroxy-or 3-alkoxy- substituted carboxylic acid deriva-tives as a starting material in that ~hey are very costly and time comsuming to prepare, but also there are problems when the protective group ~that is, 3-hydroxy, or 3-alkoxy group) of the starting material is split off to re-form the double bond. Because of these end groups, the pyrolysis reaction (in which the splitting off occurs) proceeds over a long period of time and in à discontinuous manner.
Alcohols are split off in the pyrolysis reaction causing azeotropes to form with whatever amines are present that have the same boiling point as the alcohols. Separation of ~:~5 the formed product is therefore complicated by these I ~ 7583n a~eotropes. ~loreover, a catalyst is re~uired to separate out the water as disclosed in DE-OS 2 918 486.
In U.S. Patent No. 3,652,671 a Michael adduct of methacrylic acld and N,N-dialkylalkylerle(liamine ls decom-posed to form an N-(dialkylaminoalkyl) methacrylamide.
This reaction process also suffers from another disadvan- p~
tage: poor yield. -Thus, in -the prior art where 3-hydroxy or 3-alkoxy-substituted acrylic or metha~rylic acid esters or amides, or 3-dialkylaminomethacrylie acid h~ve been employed as starting materials in a process for the for- -,~
mation of N-substituted acrylamidesl there have been sig-nlfieant problcms. The long ~nd eompl1eatecl process oP
preparing the starting materials, the long and discontin-uous pyrolysis process, and the formation of azeotropes complieating the separation o~ produet, present signifi~
eant drawbacks to their widespread use. It is therefore the obJect of the present învention to develop a process for preparing N-substituted acryl- and methacrylamides in good yields but without the drawbaeks of the prior art.

SUMMARY OF THE INVE~ITION
-It has now been unexpectedly and surprisingly found that N-substituted acryl- or methacrylamides ean be prepared in high yields in a process in which an aeryl- or ~ ~ 7sa3~

methacrylamide is transamidified with an amine to protect the double bond as well and the amine is subsequently split off from the intermediately Eormed ~,N'-disubstituted 3-aminopropaneamide to re-Eorm the double bond. The trans-amidation reaction can occur in an aqueous solution or nonaqueous environment;
however, when the reaction proceeds in a nonaqueous environment, the reaation should proceed in the presence of effective catalyst.
According to the present invention there is provided a process for preparing N-substituted acrylamides and methacrylamides of the general formula:

1 \y wherein X is selected Erom the group consisting of hydrogen and me~hyl and Y
is selected from the group consisting of NH-R-Rl, R2-N-R3, ~ ~Rq and 0, wherein R is selected Erom the group consisting oE linear-chained, branched-chained, and cyclic alkylene residues with from 1 to about 8 carbon atoms, and phenylene,~wherein Rl is selected from the group consisting of hyd-rogen, a dialkylamino, an alkoxy group, wherein -the alkyl residue contains from 1 to about 4 carbon atoms, wherein R2, R3 and R4 are selected from the group consisting of alkyl residues having from 1 to about 4 carbon atoms and wherein R2 and R3 are also capable of forming a 5 or 6 carbon atom ring, which comprises reacting acrylamide or methacrylamide with an amine having the gen-eral formula HY, wherein Y has the above-identified meanings, at a temperature ranging from about 100 to 250C, re~.oving formed ammonia and, if present, exc-ess amine or water or both by distillation; decomposing the formed N,~'-disub-stituted 3-aminopropaneamide at a temperature ranging from 160 to 350C and separating the decomposition products by fractional distillation.
The acryl- or methacrylamide which is employed as a reactant is added either in a crystalline or non-c~ystalline form; in the latter case, the acryl- or methacrylamide is dissolved in an aqueous solution. Thus, aqueous acryl- or methacrylamide solutions as commercially available and prepared in known ways from acrylonitrile or methacrylonitrile may be employed.

~.-, I I7S83~

Suitable primary and secondary aliphatic amines which may be reacted include those which comprise linear, branched, and cyclic carbon structures having from 1 to 8 carbon atoms. The carbon chain may have attached thereto further functional groups such as dialkylamino or alkoxy groups.
Representative primary amines include: methylamine, ethylamine, n-butylamine, cyclohexylamine, 2-ethylhexylamine, and preferably N,N-dimethyl-propanediamine, N,N-dimethylethanediamine, N,N,2,2-tetramethylpropanediamine, 3-methoxypropylamine. Representative secondary amines include: dimethylamine, : dibutylamine, morpholine, and N-methylpiperazine~ Representative aromatic : 10 amines include: anilm e, toluidines, p-methylaniline and p-dimethylaminoani-~ line~

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~,`' : -,~

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` ~ 175B3~) The amine reactant may be added in stoichiometric amounts or in amounts in excess oP the stoLchiometric amount. ~ ~
A 2 to about 5 fok~ molar amount based Otl the amount ofacryl ~`;`~
or methylacryl nitrile present is preferabLy employed.
A conversion, that is, a transamidation reaction to form the disubstituted propaneamides can be effected in a continuous or discontinuous process. The reaction is con-ducted at a temperature of between about lO0 and 250C, preferably between about 100 and 190C. Suitable reaction vessels include: agitator kettles, autoklaves, or heatable reacti`on tubes. ~. c.~!
It was surprisirl~ly found that the transam1d~tlon s reaction is notic~bly accelerated by -the presence o~ water.
Thus, it is preferred to employ a 30 percent to 50 percent aqueous acrylamide solution as commercially available. In the presence of water in an autoclave reaction at l40C, , the transamidation reaction takes place within 2 to 5 hours;
whereas, the reaction of a crystalline acrylamide with a higher amine takes several days.
It was also unexpectedly and surprisingly found that when the reaction was run with crystalline acryl or methacrylamide a noticable acceleration could be achieved by conducting the reaction in the presence of a catalyst.
The reaction is accelerated by the presence of protons or ammonium ions. The use o~ commonly employed amidation catalysts have proved suitable; thus, amine hydrochloride, ammonium chloride ur acrylic-or methacrylic a~id are all ~, suitable catalysts. For example, when transamidation is conducted in the presence of l to 4 percent ammonium compounds a decrease in reaction time is noticed. That is, the _~_ !~
, . . .
.: . .
~ ~7S~3() reaction is speeded up 20 fold. Since they can be used as starting materi~ls it is most preferred that acryl or 1, methacryllc acid be employed as a catalyst; also, as it is consumed dur~n~ the course of the reaction, no impurities remain. As catalysts any inorganic or organic protons spen-ding acid (Broensted acids) can be used such as acetic acid, formic acid, propionic acid, butyric acid etc., and ortho- ``
phosphoric acid, polyphosphoric acids, sulfuric acid, hydro-chloric acid etc. The catalys-ts may be used in an amount of from about 1 to a~out 4 mole'~, b~secl on tlle acrylarnlde an(l methacrylamLde employed. ~lthough there might bc some sepa- !~"'"
ration and re-us~ problems, other suitabl~ catalysts such as Lewis acid3 whlch may be empLoyed are homogenous catalysts such as dialkyl stannic ox~des and in partlcular dibutyl stannic oxide.
With either method from about 90 to about 92 per-cent of the acrylamide or methacrylamide is converted into di-substituted propaneamides. The excess amine remaining is removed by distillation as is any other element, uch as water. If water is not present the excess amine need not be removed by distillation. The distillation operation can be performed ln a reaction tube in a continuous or discontinuous fashion. ~-The reaction product, an N,N'-disubstituted 3-amino-propaneamide is subsequently decomposed by pyrolysis to leave the product, an N-substituted ~ -9 ~-, unsaturated carboxylic acid amide. During the course of the pyrolysis reaction the -~
amine is split off. It is advantageous to effect the pyrolysis continUuslY and under reduced pressure, with the rate at ! ~
~ 1~$~3~

which -the disubstituted propaneamide is added to a heated flas~ to urlder~o decomposition equal to the r~te at whlch the decomposition products are removed~ 8y removing the N-substitutect acryl-or me~hacryl amides as a sidestream and removing the split off amines in an overhead method, purities in the order o~ 95 to 98 percent of the N-sub-stituted acrylamide product are obtained. -;
At lower temperatures it is possible for the N-substituted acrylamicle -to recombine with a corre~sponding amine in the pyrolitlc dnd separdting sta~e. To remove disubstituted propaneamides as a sidestream and to obt~ln a lar~ely pure amine at the columl) hcadl vlcgorous roflux has to take place in both column sections. Or as an alter native, the pyrolysis can he effected ln hdtches arld the split off products subJecked to ~ractionated distillation.
Although the pyrolysis can be conducted up to '~
temperatures above 350C, the preferred temperature range is from about 160 to 350C and particularly preferred is the temperature range from about 160 to 270C.
The split off amine and the propaneamide which is not pyrolyzed can be readily recycled in the process, as can be the propaneamide formed by recombination which may ;~.1 occur in the pyrolitic or in the~separating process, or in both.
In order to inhibit polymerization the reaction may be conducted in the presence of a polymerization in-hibitor such as di-ter~iary butyl cresol, ~I,N-diphenyl phenylenediamine or hydrochinon me-thylether, etc. However, the addition of a polymerization inhibitor is not compuls-ory. This is an further advantage of the presentinvention E
5 3 7~83(1 since inhibitors or their derivatives formed during the reaction may affect the subse~uent polymerizatlon of the "~!
product obtained.
The yields of the process oP the present in-vention are hi~h, up -to about 9S ~ and more.
The following examples more fully illustrate the ~;
invention.
EXAMPLE I
1560 ~rams (12 moles) of N,N,2,2--tetramethylpro-panediamlne~ 2B4 grams (4 rnoles~ of acrylamide, and 7 ~rams of acrylic acid were heatcd at 150 to 180 C over a ~our ;,?!nSi hour period (untll ammonia ~ormation was compl~te). Tha reaction mlxture containing exces~ amine was added drop-wise to a heated flask maintained a-t a temperature of 240C at the same rate as the N~N',N',2,2-tetramethyl-3- i.. ~
aminopropyl)-acrylamide was separated out via a column r under 50 mm pressure and as the split-off amine was sepa-rated out as a sidestream overhead. The amide fraction contained about 95 % N(N',N',2,2-tetramethyl-3-aminopro-pyl)-acrylamide which corresponds to a yield of 92 ~.
EXA~IPLE II
1560 grams (12 moles) of N,N,2,2-tetramethyl-propanediamine, 284 grams (4 moles) of acrylamide, and 1 gram of ammonium chloride were heated at 150 to 180C
over a 4 hour period until the ammonia formation was com-plete. The reaction mixture was worked up by a procedure as described in Example I. The same yields as in ~xample I
were also attained.

bw -~,~P, ~ 3 7$~3C) E:,XA~ 'L l- 111 ____ __ ~
390 gr.lms (3 mo1cs) of N,N,2,2-tetramet11yl~
propanediamine, 71 gralns ~I mole) of acrylamide, and l qram of dibutyl stannic oxide were heatec1 at 150 to 170C over an ei(~ht hour period until tlle ammonia formcltion was com-plete. The reaction mixture was furt11er processed as des-cribed in Example I. The amide fraction contained 95 %
N(N',N',2,2-tetramethyl-3-aminopropyl)acrylamide which corresponds to a yield of 70 ~.
EXA~IPLL LV (CO~IPAI~lSUN) 1560 grams (12 moles~ of N,1~1,2,2-tetramcthylpro~
panetliamlne ar)c1 2~ rams ~4 moles) ot` acrylamido ~/ere heated at reflux (about 145C)~ Cas chromatogrdprlic obser-vation of the reaction showed that after a three day period only about 80 % of the s-tarting material had been converted. ¦
More by-products were protluced using the process than were produced in Examples 1 and II.
EXAMPLE V
1560 grams (12 moles) of N,1~1,2,2-tetramethylpro-panediamine and 947 grams of a 30~ aqueous acrylamide solution were heated in a 5-liter autoklave at 160C under autogenous pressure for four hours. After removing by ~.~,j;
distillation the formed ammonia, the excess aminc and water, an oily residue was obtained. The residue was added dropwise to a heated flask maintained at a temperature of 230C at the same rate as the N~N',N',2,2-tetramethyl-3-arl~inopropyl) acrylamide was separated out as a sidestream and as the spli-t-off amine was separated out overhead under a pressure of 50 mm via a co]umn connected to the flask.

_g _ 7 .
3 1 ~3~

N(N',N',2,2-tetramethyl-3-aminopropyl)acrylamide having a purity of 95 ~ was obtained. lhe total yield lias ~8nu.
EYAMPLE VI
A mixture of 390 parts (3 moles) o~ N,11,2,2-tetra-methyl-propanediamine anc1 23~.7 parts (l mole) of a 30 aqueous acrylamide solution was conducted trough a tube reactor heated at 180C, the pressure being 10 bar and the residence time being -two hours. After Ieaving the reactor, the formed ammonia, the excess amine, and water ~Yere re-moved by distillation. The resid~le was dropwise ad(1cc1 to a flask maintained at a temperature of 240 C at the same rate as N(N',N',2,2-tetramctl)yl-3-dminQpropyl)acrylamide was separated out as a sldestredm anc1 the spllt-off amine was separated 0l1t overhead under a pressure of 50 mm ~ia a column connected with the flask. NIN',N',2,2-tetramethyl- ~-3-aminopropyl)acrylamide was obtained in a purity of 98 ~
and a yield of 91 ~. The excess N,N,2,2-tetramethylpropane-diamine was recycled to the tube reactor after the water is separated out by azeotrope distillation with toluene.
The split-off amine was directly recycled to the tube reactor.
EXA~IPLE VII
1224 grams (12 moles) of N,N-dimethylpropane-diamine, 284 grams (4 moles) of acrylamide, and 7 grams of acrylic acid were heated at the reflux temperature for a four hour period. The reaction mixture was added dropwise to a heated flask maintained ~ -, ~ 1 7~3~
at a temperature of 240C at the same rate as the N(N',N'-dimethyl-3-aminopropy~l acrylamide was separated out via a column under ~() nun pressur~ as a sidestream and clS the !~;.,.-.,.
split-off amine was separated out overhead. The amide fractiont 585 grams, contained 95~ N(N',Nl-dimethyl 3-aminopropyl)acrylamide which corresponds to a yield of ~9.1%. , "c EX~MPLE VIII
1224 grams (12 moles) of N,N-dimethylpropane-diamine, 340 grams of methacrylamide were heated at the reflux temperature for a nine hour period. ~t the start o~ ~
the reactor, 3 grams of methacrylic acid w~re added to th~ t`
re~ction mixture. Dur:inq ~he course of the reaction, two more 3 c3ram adclitions of acid were added.
Tlle re~lction m~xture was added dropwise to a heated flask maintained at a tempera-ture of 240C at the same rate as the N(N',N'-dimethyl-3-aminopropyl)methacrylamide was separated out as a sidestream and as the split-off amine was separated out overhead. The amide fraction, 608 grams, contained 96%
N(N,N~'-dimethyl-3-aminopropyl)methacrylamide. This corresponds to a yield of 85.8%.
EX~MPLE IX
1044 grams (12 moles) of n-butylamine, 284 grams (4 moles) of acrylamide, and i grams of acrylic acid were heated in an autoclave at 140C for a four hour period.
~.
The excess amine was then distilled off and the residue ~? 5-`' subjected to a pyrolysis reaction conducted under similar reaction conditions as those described in the above I J 7S~3~

examples. Thus, at a pressure of 100 n~l, 1523 grams of N-n-butylacrylamide were produced: a yield of 90~. ;
~X~W PL~ X ~ k 710 grams (10 moles) of acrylam:ide and 5 grams o~
dimethylamine hydrochloride were filled into a 5-liter autoclave. 1350 grams (30 moles) of dimethylamine gas was then charged into the same and subsequently the reaction mixture was heated at 140C for four hours. After completion of the reaction, the pressure in the aut:oclave was reduced to atmospheric pressure. As the reacted mixture is added dropwise to a heated flask at a temper~ ,"
ature of 200C,th~ dimethylacrylamide therein (85 grams, which correspond to a yield of 85.9~ is simultaneously distilled off via a column connected to the flask. The split-off dimethylamide was condensed in an ace~one/ carbon dioxide snow cooling trap.
EXAMPLE XI
710 grams (10 moles~ of acrylamide and 3375 grams of a 40% aqueous dimethylamine solution were heatecl in an autoclave at 150C for four hours. The excess amine, water, and formed ammonia were distilled off. The formed residue was worked up on a similar manner as described in Example X. 871 grams of N,N-dimethylacrylamide were obtained: a ~'"i yield of 88%.
EXAMPLE XII
71 grams (1 mole) of acrylamide, 300 grams of N-methylpiperazine, and 1 gram of acrylic acid were heated at the reflux temperature. In the following eight hour period, two additions of acrylic acid of 1 gram each is added to ~ .1 7~3~1 the reaction mixture~ Then the excess amine was distilled off and the solid residue was heated at 300~C. At 100 mm press-~.,., , .i ure first the split-off amine WAS distilled off and then 123 grams (79.8~ of N(N'-methylpiperazyl)acrylamide.

EXAMPLE X:[II (COMPARISON) 71 grams (1 mole) of acrylamide and 300 grams of N-methyl-piperazine were hea~ed in an autoclave at 180C.
The amount of transamidation which took place was measured by gas chromatography. After a 48 hour per:iod only about 50~ had been converted; therefore, the mixture was not ;,.~.
worked up. t .

.
~ . i .,

Claims

The embodiment of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for preparing N-substituted acryl-amides and methacrylamides of the general formula:
wherein X is selected from the group consisting of hydrogen and methyl and Y is selected from the group consisting of NH-R-R1, R2-N-R3, and , wherein R is selected Prom the group consisting of linear-chained, branched-chained, and cyclic alkylene residues with from 1 to about 8 carbon atoms, and phenylene, wherein R1 is selected from the group consisting of hydrogen, a dialkylamino, an alkoxy group, wherein the alkyl residue contains from 1 to about 4 carbon atoms, wherein R2, R3, and R4 are selected from the group consisting of alkyl residues having from 1 to about 4 carbon atoms and wherein R2 and R3 are also capable of forming a 5 or 6 carbon atom ring, which comprises reacting acrylamide or methacrylamide with an amine having the general formula HY, wherein Y has the above-identified meanings, at a temperature ranging from about 100 to 250°C, removing formed ammonia and, if present, excess amine or water or both by distillation; decomposing the formed N,N'-disubstituted 3-aminopropaneamide at a temperature ranging from 160 to 350°C and separating the decomposition products by fractional distillation.

2. The process according to Claim 1 which comprises reacting acrylamide or methacrylamide dissolved in water with the amine.

3. The process according to Claim 1 wherein the reaction is conducted with crystalline acrylamide or meth-acrylamide in the presence of effective amidation catalysts.

4. The process according to Claim 1 wherein the reaction is conducted at a temperature of about 100 to 190°C.

5. The process according to Claim 1 wherein the decomposition is conducted at a temperature of about 160 to 270°C.

6. The process according to Claim 1 wherein the decomposition is conducted in a continuous manner with the rate at which the disubstituted aminopropaneamide is added to undergo decomposition equal to the rate at which the decomposition products are removed.

7. The process according to Claim 1 or 6 wherein the decomposition is conducted under reduced pressure.

8. The process according to Claim 1 wherein based on the acrylamide or methacrylamide employed, the amine reactant is present in a mole ratio of 2:1 to 4:1.

9. The process according to Claim 3 wherein the catalyst employed is selected from the group consisting of ammonium chloride and ammonium hydrochlorides of the amine reactant employed, and acrylic and methacrylic acid salts of the amine compound employed t and acrylic and methacrylic acid.

10. A Process for preparing N-substituted acrylamides and methaacrylamides of the general formula:
wherein X is selected from the group consisting of hydrogen and methyl and Y is selected from the group consisting of NH-R-R1, CH3-N-CH3, wherein R is selected from the group consisting of linear-chained and branched-chained alkylene residues with from 2 to about 6 carbon atoms, wherein R1 is selected from the group consisting of the dimethylamino and the methoxy group, which comprises reacting acrylamide or methacrylamide with an amine having the general formula HY, wherein Y has the above-identified meanings, at a tempe-rature ranging from about 100 to 250°C, removing formed ammonia and, if present, excess amine or water or both by distillation; decomposing the formed N,N'-disubstituted aminopropaneamide at a temperature ranging from 160 to 350°C and separating the decomposition products as they form by fractional distillation.

11. The process according to Claim 10 which comprises reacting acrylamide or methacrylamide dissolved in water with the amine.

12. The process according to Claim 10 wherein the reaction is conducted with crystalline acrylamide or methacrylamide in the presence of effective amidation catalysts.

13. The process according to Claim 10 wherein the reaction is conducted at a temperature of about 100 to 190°C

14. The process according to Claim 10 wherein the decomposition is conducted at a temperature of about 160 to 270°C.

15. The process according to Claim 10 wherein the decomposition is conducted in a continuous manner with the rate at which the dissubstituted aminopropaneamide is added to undergo decomposition equal to the rate at which the decomposition products are removed.

16. The process assording to Claim 10 or 15 wherein the decomposition is conducted under reduced pressure.

17. The process according to Claim 10 wherein based on the acrylamide or methacrylamide employed, the amine reactant is present in a mole ratio of 2:1 to 4:1.

18. The process according to Claim 10 wherein the catalyst employed is selected from the group consisting of ammonium chloride and ammonium hydro-chlorides of the amine reactant employed, and acrylic and methacrylic acid salts of the amine compound employed, and acrylic and methacrylic acid.