CA2256529A1 - A cyanocrylate adhesive - Google Patents

Abstract

Described is a cyanacrylate adhesive containing as plasticizer at least one partial and/or full ester of aliphatic mono- or polycarboxylic acids with 1 to 5 C-atoms bound directly to each other and aliphatic mono- to pentahydric alcohols with 1 to 5 C-atoms bound directly to each other, the number of Catoms bound directly to each other in the other aliphatic groups being at the most three when one aliphatic group contains 4 or 5 C-atoms. Even at high plasticizer concentrations, the shelf life is good. This adhesive is a pressure sensitive adhesive. The addition of up to about 20 % of plasticizer causes hardly any increase in the setting time.

Description

31.0~.1996 A Cyanoa~ "l~te Adhesive This invention retates to a cyanoa~late adhesive CGI ~tai. ,iny an ester as pl~s~ ; An Cyd"odaylate adl,esives containing an ester as p'~tic;~er are known.
Thus according to DE 34 00 577 up to 25% by weight of a pl~s(ic-;~Qr are 5 added in additio" to 4 to 30% by wai~l It of a copolymer of vinyl chloride andvinyl ~oet~e. The pl li~ r in ~ ~Pstion is an ester of an dr~.",alic mono- or dicarboxylic acid and a mono- or polyhydroxy ~",~,ound. Appart:nlly the rate at which the adhesive cures is not siy. li~iCdl Itly a~reclecl by the addition of this aromatic pl-slio;~er nor is the quality of the bond fo,l,~ed during the 10 curing pn~cess. When these tests were re-run, however it was found that the curing rate was siy,)ificd, Itly re~ ~c~ Thus the setting rate of cyanoacrylate ethyl ester for example on EPDM is slowed down from 5 seconds to 35 seconds by a 30% addition of butyl benzyl phthalate In A~L l~t;vn ac~rdin~ to DE 43 17 886, the following esters are added 15 to cyanoacrylate adhesives to reduce adhesion to the skin:
1. AliphdtiC Cdl L~ylic acid esters co, Itai"i"y an alipl ,atic group in which 6 or more Cdl bon atoms are directly attached to one another 2. AIi~Jhdt;C cdlL~tylic acid esters containing at least two aliphatic groups in which 4 or more carbon atoms are directly atlact ,ed to one anotl ,er 20 3. Carboxylic acid esters of a ~, L ocyclic ~ ound which in a carbox-ylic add residue or an alcohol residue c~nlains an ali~JI ,atic group inwhich 5 or more ca~ L,on atoms are directly dtla~,e.i to one anothen In ~dLI;lir~" the cya-,odaylate adl~sives contain poly~eri~atiol~ accelerators~
The problem add~essed by the p~esenl invention was to avoid the 25 diadvantages of known cydllod~ylate adl ,esives containing pl slic;~ers and more particularly to provide a cyanoacr~late adhesive having high stability in storage useful slre, l~tl ~ values and virtually the same setting rate.

The solution provided by the invention is clefi.-~J in the claims and consists ~cs~"tially in using at least one partial and/or full ester of a m~,,.ob-~ri~ or ~oly:~sio aliphatic ~.L~.<ylic acid containing 1 to 5 ca.Lo.~
atoms directly dtla~l-oJ to one a-,-~U.er and ~.-onol,~rdric to pa,~tahydric aliphatic al~l-ols containing 1 to 5 ~-I,G.I atoms directly dtla~eJ to one another as pl~ r, the number of ~- L G-~ atoms directly atlacl)ed to one another in the other aliphdtic groups being at most 3 where one aliphalic group contains 4 or 5 ~-L,o-, atoms directly dua~ J to one an~tl.er.
The alcohol ~"po,)e,~t of the ester is pr~fe,~ly an alcohol ~ntai,ling 1 to S and, more particularly, 2 to 4 OH groups and up to 2 to 5 and, more particularly, 3 or 4 ~,bon atoms directly dtlached to one a".~tl,dr. The number of carbon atoms not directly atla~ hed to one a,)otl,er may be as high as 1 10 and, more particularly, is up to 18 ~, bo, ~ atoms.
The following are ."e,ltio-.eJ as examples of monohydric alcohols:
methanol, ~ll ,anol, 1 -~rDpd, ~ol, 2-~,. opanol, 1 -butanol, 2-butanol, 2,2-dimethyl-1~opa-,ol, 2~ethyl~ ,a"ol, 2,2-dimethyl-1-~,r~a"ol, 2 rnethyl-2-propanol, 2-methyl-1-butanol, 3 rnethyl-1-butanol, 2-methyl-2-butanol, methyl-2-butanol, 1-~entanol, 2-pe"tanol, 3-~ntanol, c~clopen~al lol, cyclopenlcnol, glycidol, tetrahydrofurfuryl alcol ,ol, tetrahydro-2H-pyran~-ol, 2-methyl-3-buten-2-ol, 3 rnethyl-2-buten-2-ol, 3-methyl-3-buten-2-o1, 1-cyclupropyl etl,anol, 1~enten-3-ol, 3~,1t~n-2-ol, 4-~"ton-1-ol, 4-penten-2-ol, 3-pentin-1-ol, 4-pentin-1-ol, ~ aryyl alcol,ol, allyl alcohol, hydroxyace tone, 2-methyl-3-butin-2-ol.
The following are ~,entio"eJ as examples of dihyd~ic alcohols:
ethane-1,2-diol, prop~ne-1,2~iol, propan~1,~diol, dihydroxyacetor,e, thioglycerol, 2-methyl 1~,opan~1,3 diol, 2-butin~1,4-diol, 3-buten~1,2~iol, butane-2,3-diol, butane-1,4-diol, butane-1,3-diol, butane-1,2-diol, 2-butene-- 1,4-diol, 1,2~clope"ta"ediol, ~methyl butan~1,~diol, 2,2-di",etl"~l propane-1,3-diol, 4-cyclopenten~1,3-diol, cycJupe,lta,~1,2-diol, 2,2~Jil"ethyl propane-1,3-diol, p~nta"~1,2~iol, pellt~ne-2,4~iol, ~ tall~1,~diol, 4-cyclop~- ~t~n~1 ,3-diol, 2-methylene ~,r~pane-1 ,3-diol, 2,3-dihydroxy-1,~
dioxa--e, 2,~dihydroxy-1,~dithiane.
The followin~ are ,.,e.~ti~...ed as examples of trihydric alcohols:
glycerol, erythrulose, butan~1,2,4triol, erythrose, U,reGs~, t~i."eU"~lol 5 ethane, 2-hydroxymethyl propane-1,3-diol.
The followin~ are m~-ltio..~J as exsmples of tetrahydric alcohols:
erythritol, Ihreilol, pentaerythritol, ~r~ 1O5¢, ribose, xylose, ribulose, xylulose, Iyxose, sscorbic acid, ~luconic acid-y~ tone.
The following are ,ne.~tioneJ as exa--,ples of pa..t~l.y~l~ic alcohols:
10 arabitol, adonitol, xylitol.
In one particular e~ ~nl of the invention, the polyhydric alcohols described above may be used in etl,eri~,ed form. The ethers may be prepared from the alcohols ~ Itioned above, for example by ccnde"sation reactions, Williamson's ether synthesis or by redction with alkylene oxides, 15 such as ethylene, propylene or butylene oxide. Examples include diethylene glycol, triethylene glycol, polyethylene glycol, diglycerol, triglycerol, tetraglycerol, pentaglycerol, polyglycerol, technical mixtures of the conde"-sation products of glycerol, glycerol propoAylate, diglyc~rol ,,,upoAylate, pentaerythritol ethoxylate, dipentaerythritol, ethylene glycol ~"o- ~obutyl ether, 20 propylene glycol monohexyl ether, butyl diglycol, dipropylene glycol monomethyl ether.
The following monoL~ic carboxylic acids may be used for the este, ification reaction with the alcohols mentioned above: formic acid, acrylicacid, acetic acid, ~ opiu,-ic acid, butyric acid, isobutyric acid, valeric acid,25 isovaleric acid, 2-oxovaleric acid, 3-oxovaleric acid, pivalic acid, aceto~tic acid, levulinic acid, ~methyl-2-oxobutyric acid, propiolic acid, tetrahydrofuran-2~a~Loxy1ic acid, ."ethoxyacetic acid, dimethoxyacetic acid, 2-(2-methoxyethoxy)-acetic acid, 2-methyl acetic acid, pyruvic acid, 2-methoxyethanol, vinyl acetic acid, allyl acetic acid, 2-pelllelloic acid, 3-30 pentenoic acid, tetrahydrofuran-2~, L oxylic acid.

The following are examples of polybasic carboxylic acids: oxalic acid, malonic add, fumaric add, maleic add, succinic add, glutaric acid, acetylene dic~ ylic acid, ~ cstic acid, aceto,)e dicarboxylic acid, ",eso~-~'ic acid, ~tta~nic acid, dimethyl malonic add, methyl ",alo"ic acid, 5 ethyl malonic add, Hydroxycarboxylic acid~ may also be used as sta,li"~ ",ate,ials, examples including tartronic acid, lactic acid, malic acid, talldlic acid, citra",aleic acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, ~hydroxybu-tyric acid, 3-hydroxyglutaric acid, dihydrox~fumaric acid, 2,2~i",ell,yl-3-10 hydrox~propionic acid, cJi.ll~UIylol propionic acid, glycolic acid The esle, ification may be either complete or partial. Mixtures of theseacids may also be used for the eslerir,caliG".
The esters to be used in ac~l J~"ce with the invention as prepared from these alwhols and cal L~xylic acids or the c~ ~spo"di.)g derivatives are 5 preferably free from catalysts, more particularly alkali metals and amines The following are mentio"ed as examples of the esters according to the invenffon: glycerol ~ jA~ Q, glycerol tripropionate, tri~lycerol p~utaace-tate, polyglycerol A~tPle, diethylene glycol di~c~tAte, 3-hydroxyvaleric acid ethyl ester, lactic acid butyl ester, lactic acid isobutyl ester, 3-hydroxybutyric 20 acid ethyl ester, oxalic acid diethyl ester""eso~Alic acid diethyl ester, malic acid dimethyl ester, malic acid diiso~topyl ester, tall~l ic acid diethyl ester,tartaric acid dipropyl ester, tartaric diisopropyl ester, glutaric ester dimethyl ester, succinic acid di",etl,yl ester, succinic acid diethyl ester, maleic acid diethyl ester, fumaric acid diethyl ester, malonic acid diethyl ester, acrylic 25 acid-2-hydroxyethyl ester, 3-oxovaleric acid methyl ester, glycerol d~cetAte,glycerol tributyrate, glycerol tripropionate, glycerol cJi,u,opio,)ate, glyceroltriisobutyrate, glyoerol diisobutyrate, glycidyl butyrate, Acetoac~tic acid butyl ester, levulinic acid ethyl ester, ~hydroxyglutaric acid ~l;,ll~thyl ester, glycerol acetate Ji~,opionate, glycerol di-cet~te butyrate, propiolic acid butyl ester, 30 propylene glycol diaoetate, propylene glycol dibutyrate, diethy.ene glycol dibutyrate, l~im~ll,ylol cU.a.~e bi~t~f-, t imaU,ylol ~U,ane tributyrate, ,~p~, tyl alcohol dibutyrate, n~Un~ rao~tic acid pentyl ester, dim~U ,oxyac~
tic acid butyl ester, glycolic acid butyl ester.
The boiling point of the esters accor~in~ to the invention is above S 180~C and ~r~rably above 200~C at oG--"al pressure.
The estors according to the invention are added in a quantity of up to 50% by weight and ,~,efcrably in a quantity of 1 to 30% by weight, based on the adhesive as a whole. Beyond a co-,~-lbdtion of 30% by weight and, more particularly, 40% by weight, the polycyd"oa~ylates show ~ntacl-10 adhesive prope,lies.
The cyanoacrylate adhesives are Essentially based on typicalmonoacrylic acid esters and/or bis~yanoauylates.
~ Typical ",onocyanoacrylic acid esters~ in the contexl of the present invention are co""~ounds CGIleSpGlldill9 to the following general formula:
H2C = C(CN)-C0-O-R (I) where R is an alkyl, alkenyl, cycloalkyl, aryl, alkoxyalkyl, aralkyl or haloalkyl group, more particularly a methyl, ethyl, n-propyl, iso~,ropyl, n-butyl, isobutyl, 20 pentyl, hexyl, allyl, methallyl, uotyl, ~r~pdryyl~ cyclol,exyl, benzyl, phenyl, aesyl, 2-chloroethyl, ~chlor~propyl, 2-chlorobutyl, trifluoroetl,yl, 2-methoxy-ethyl, 3-methoxybutyl and 2-ethoxyethyl group. The cyanoacrylates mentioned above are known to the expert on adhesives, cf. Ullmann's Encyclopaedla of Industrial Chemistry, Vol. A1. page 240, Verlag 2~ Chemie, Weinheim (1985), US-PS 3,254,111 and US-PS 3,6C~,3~Q.
Prefe"ed ."GnG",er~ are the allyl, methoxyethyl, ethoxyethyl, methyl, ethyl, propyl, iso~,r~p)~l or butyl esters of 2 cydnoac, ylic acid.
~ Bis-cyanoacrylates~ in the col)text of the pres~-,l invention are compounds CGI ,esl~onding to the following ge"erdl formula:

lH2C = C(CN)-CO-OLR' (Il) where R' is a linear or ~ ~ ~1 dif~l ~ ~l alkane group CGI Itai.ling 2 to 18 and more partieularly 6 to 12 C811~ll atoms whieh may also conlai-, hetero 5 atoms, sueh as halogens and oxygen, or ali~l,atie or a~o",alie rings.
However R' is ~,rererdbly a pure hyJ~a,bon.
It is i,.,~G-lant for the bis-ey~,-oa~lates to be partieularly pure. This requirei",ent is satisfied for example, by the following pro~ ion and purifieation ",etl,ocls. ~sse,ltially ~,.G"oe~ai"oa~lates are transesterified 10 with diols and the reaetion mixtures are then worked up by hacliG"al erystallization.
Aceo(dingly a suitable pr~cess for the prod~ion of bis-eyanoaery-lates co",~rises t,~nsesleril~ing 2-eya"oa~ylie aeid or alkyl esters thereof eorresponding to the following ~aner~l formula:

H2C = C(CN)-CO-O-R2 (111) where RZ is a linear or b,ar,cl ~cJ alkyl radieal co"laining 1 to 6 ~, bo" atomswith diols ~" t7spo"~i"y to the following yei ,eral formula:

[H~]2R' (IV) where R' is a linear or ~ J ~d difi "c1ional alkane group co"tai. ~ing 2 to 18 ~, bon atoms whieh may also eontain hetero atoms sueh as halogens and 2~ oxygen or aliphatie or ~ro",atie rings, to form bis-eyanoaerylates co"_sponcJi"y to g~llerdl formula ll and then purifying the reaetion mixture by hacti~,"al eryst~ tion.
Accordingly one sta, ling produet is monofi" lOtiGI ,al Cy8~ ,oa~ ylie aeid or alkyl esters U~r~of c~l,es~"ding to formula lll. The alkyl group has to be 30 selected so that the alcohol fo",)eul is easy to remove. Suitable possibilities in this regard are known to the expert from the y~ ral b~..s~sl~lifi~tiu-l rea~tion. The alcohol is ~rvf~.~biy r~-llo~od by ~i~t~ Qn. Accordingly, R2 is a linear or bra-,~l,eJ alcol-ol r~s~due conbining 1 to 6 ~IbGll atoms and ,u,e~rdbly 1 or2 c~,Lon atoms. The monofun~tiunal cya..oa~ylic acid ester 5 is sPhili~s~l in the usual way.
The diols (formula IV) are dihydric ,uri--.a~y or secc"Ja,y alcohols, preferably ~ri,n."y alcol,ols. The hydroxyl groups may be in any ~,osilion to one another, but are ~r~fer~Lly in the alpha/o")eya f~sition. The diols co"tain 2 to 18 carbon atoms and p,efe~bly 6 to 12 carbon atoms. They may 10 be linear, branched or cyclic. The aliphatic radical may also contain an aromatic group or, in addition to the hyd~og~" and ca,L,o" atoms, may also co"lai.) hetero atoms, for example chlorine or oxygen atoms, ~,ref~rdbly in the form of polyethylene or polypropylene glycol units. Hexanediol, octanediol, decanediol and d~Jdec~ ~ediol are specifically mentioned as diols.
The cyanoaaylic acid ester is used in exc~ss Accordi"gly, the molar ratio of monofu~,lional cyanoacrylic acid ester to the diol is at least 2.0:1.0,preferably 2.5:1.0 and, more ~refer~bly, 2.2:1Ø
The transeste, if icaliG" is catalyzed by strong acids, more partic,ularly by sulfonic acids, ~r~ferably by d,un)dlic sulfonic acids, for example p-toluenesulfonic acid. However" a~l ~U ~alene suhfonic acid and bel ,~e,)e sulfonic acidand acidic ion excl,a"ger~ may also be used. The cc"centldlion of the transesterification catalyst should be between 1 and 20 % by weight, based on the monofunctional cyanoa~ylate.
The tra"ses~erificaliul"eacti~n is ca"ied out - as usual - in solution.
25 The solvents used are ar~,",dlic hyd~oc~GI~s and halo~enaled hydlucar-bons. Prefel,ed solvents are toluene and xylene. The co"cen~ralion of the solution is in the range from 10 to 50% and pre~rably in the range from 10 to 20%.
The r, ~nol ,ydric alcohol f~"lled and the water fol ",~.1 are removed in 30 known ,nar")er, ~l~ld~ly being ~istilled offwith the solvent. The conversion of the b ~ns~sts~,cdli~, f~;tion is ."u"itor~d. for examp.e, by NMR sp~a.
As usual the r~action Iasts several hours. Where toluene is used as the solvent and p-toluene sulfonic acid as the catalyst the l ~actiur, is over after10 to 15 hours i.e. there is no further elimination of alcohûl.
S Now the way in which the redctiGn mixture is worked up is very illl~lldl~t. Where acidic ion e~ n~6(s are used as the catalyst they may be removed by simple fill~alion. Where soluble suHonic acids for example p-toluene suHonic acid, are used as the catalyst they are removed by solvent su hstitl ~tion: toluene is replaced by a mixture of I ,exane, I ,~ptane or ~eca"e.
After two r,aclio,)al crystalli aliûlls pure bis-cyanoa~ylate is obtained.
According to NMR spectra it has a purity of more than 99%.
The bis-cyanoa~ylate obtai,)ed is stable in slor~ye with the usual st~hili7ers and in the usual conce, It~dtiGI ,s i.e. there is hardly any c~ ,dnye in its melting point after 6 Illontl,s at 20~C.
However the bis~yanoa~ylates obta,"e.l pol~",e,i~e very quickly in the presence of bases ~,referably almost as quickly as the colles~,G"diny ",onocyanoacrylates. As in the case of the monofu- ,~tio- ,al cyanoa~ylates traces of water are sutricieilt for this purpose. A three din,e-,siû,,ally crosslinked polymerwith relativelygood ll,en~al ~,upe,lies isformed.
Acoording to the invention tl ~ref~,e it is used in known cyanoa~ylate adhesives in a quantity of O.S to 50% by weight pre~rdbly in a quantity of 1 to 10% by weight and more prbfer&bly in a quantity of 2 to ~% by weight based on the adhesive as a whole.
~esides the pl--stic;~qr acoor~ling to the invention the adl,esive may 2~ contain other additives for example other pl-~tiçi~ers, thickeners stabilizers activators dyes and ~c~leratura for example polyethylene glycol or cyclodexl. i".
The adl ~sive is ~ parecJ in the usual way by mixing the co, "po"enls.
In all the cases invesliyate-L the new adhesives were stable in slora~e for more than one year at room te",peral.Jre or for more than ten days at 80~C.

The curing rate is hardly arr.s~,laJ by the pl '~ti~ . a according to the invention, in other words it is prd~ra~ly not ~ouhl~ l and barely ~c~e~
minute in the case of EPDM.
The new cyanoauylate ~JI,esive according to the invention is 5 particularly suitable for the bondin~ of - in particular - rubber, metals, wood, c~r~-"ics, china, pap~,~oar~, paper, cork and pl~~tics except PE, PP and Teflon and Styropor.
The invention is ill~.sllatecl by the following El~a",,les In order to obtain as cc ",~ he,)si~e an overview of the cl,anges in the 10 properties of the g,a"oa~ ~/lates brought about by the addition of plasticizers according to the invention, mixtures of h~si~lly st~hili~ed pure ester and glycerol triacetate (triacetin) in the range from 0 to 50% by weight were prepared. The basic stabili~tion consists of hydroquinone (400 to 1,000 ppm) and SO2 (5 to 15 ppm). The samples were hGIIIO9enj ed for six days 15 in a shaking machine and then measured.

Examples 1 to 3 The results (viscosity, setting times, sll t "~U ,s) for the three different esters AE, BE and MOE (AE = ethyl ester, BE = butyl ester, MOE = methoxy-20 ethyl ester) are set out in Tables 1 to 3.

o ~D
UJ ~
~ ~ ~ 5 ~ N ~---- ' .. ~ O CD ¢~ ~
~ E a~
Z
o U~ ~ _ 0 0 g ~ 't ~ N ~ N
CO
O o O O O

E i-- ~, E ~ ~ ~ ~ ~OD ~o .' Cl~ ~
N ~ ~ U) ._ 3, o ~' CD a~ _ ~ 0 a~ 8 w _ c .a~ E
~ ~ C~
N t'~

~ _ - ' ae . o ~o ~o ~o ~o a a~
c~ ~ ~
~ _ ~n 6 6 ~: 6 ~ 6 ~D o O U,~
_ 6 cn ~ o ~ ~ o ~5 ~ 8 ~ o ~ .. ~D
~ ~ E
0 ,~ X

Accordinçl to Table 1, the ~ J;tion of the ~ r according to the invention pr~ces a slight i~ r6ase in the ViSC05iti95. Accordingly, the visoosilies of the ~lr-it;c;~er-containing s~ les are slightly higher after the short-time sIora~a test (10 days/80~C in PE bottles).
lt is only with an ~ tion of 40% that there is a sli~ht increase in the setting time on EPDM, but a ~istinct ;n~;r~ase in the setli. ~~ time on Limba.
By w nIrast, the ~ddition of pl~lic;-~r does not have any adverse effect on the setting times on PVC.
The sl~"~tl ,s on aluminium only begin to fall with a pl~lic;~er co"tent of 30%; the same applies to the sl,~r,~tl,s on PVC.

Tabl~ 2: Influence of the Pl~sti~i7er Triacetin on the Viscosity, Setting Times and St~el,y~l,s of the Bu~yl Ester of Cyanoacrylic Acid ExampleAddition Ester Quantity Viscosity Setting Times 5~
1%1 ImPasl Isl INlmm21 1 Od/80~C EPDM Limba PVC Alu PVC
2a None BE 3.2 6.2 5 >60 <5 9.5 3.7 2b Triacetin BE 10 3.4 6.9 7 ~60 <5 8.4 3.4 D
2c Tr;ac~ti~ BE 20 4.0 9.1 10 ~60 <5 4.7 3.0 2d Tliacetil~ BE 30 5.0 15.9 13 ~60 <5 2.9 2.8 2e Triac~ti" BE 40 6.0 53.7 22 ~60 c5 1.2 1.9 2f Triac~ti" BE 50 8.2 87.7 90 ~60 c5 1.6 1.0 H 1867 PCT t3 Acco.cl;"~ to Table 2, the Z~ ;t;G.I of pl~s(ic;~ar also leads to an in~ease in viscosit~ in the case of the butyl ester, although this i.,~rease is more pronounced than in the case of the ethyl ester after the short-time s~o,dye test, particularly in the case of the mixtures co, Itaining 40 and 50%.
Above 40% ~I-sli.,i-er, the selli..~,~ times on EPDM are no longer ~pt~le for a reactive ~-JI ~sive. Di~er~. .c~s in the setting times on limba wood attribLnable to different ~l -- lie;-~r cc, Ite~nts were not in evids. .ce in view of the long setting time of the pure ester. The setting times on PVC are not adversely a~cte.l by the plaslic;~er.
The co",pa, atively low ~b e, ~~U ,s on aluminium and PVC in the case of the butyl ester were further red~ ~c~rl by the addition of pl--tici~er. However,they are still acce~,table for a colltd~l adhesive above 20% and 30%, respectively.

S 0 0 09< 09< 0 6 8Z 91 1 OS 30W U!l~e! 'l ~~
~ 0 0I-S 09~ 08 ~ SZ ~ 01 0~ 30W 'J!l~e!'l e~ D
1 0 1 0I-S OS SI L 9Z Z 6 0~ 30W U!l~e!)l P~ -~
Z ~-~ 0~-S St~ 8 S LZ v 8 OZ 30W 'J!lE~e!'l ~8 ~ ~ 8-9 0I-S SZ 8 1 9Z L-L 01 30W U!~ q~
lWY9-~ 1 ZI 0I-S 0~ L S 88 1~L - 30W euoN B~
~)/\d nl~d eqw!l Wad3 ~oO8/PO I
Irww/NI lsl Isedwl 1%1 41BueJls sew!lBU!lleS ~ S~!~S!~ ~4!1Uen~ ~elS3 UO!l!pp~ eldwsx3 (30W) JelS3 l~41e~X~~;13 P!~~ ~!l~oeoue~ ~o s~llfiueJls pue saw!l fiU!ll~ l!soeS!~ e41 uo U!leoe!Jl Jb~e!ls~lJ e41 ~o eouenl~ul :~ elqel d L981 H

ACCGI I~ U to Table 3, the A~ ;OI I of the ~ lic;~r according to ths invention also pro~l ~s a sli~ht in~ eas~ in the visc~ities in the case of the MOE afflou~h, in c~ ~sl to AE and BE, the short-time stability in slor~ye is slightly improved by the pl~ ;-er.
With a pl --lirl~r c~nt~ It above 40%, the settin~ times on EPDM and limba are too lon~ for a reactive a~ sive. The settin~ time on PVC
inweases ~ sli~lly above 50%.
Wlth a pl ~ r conl~- n above 20% and, more particularly, 30%, the slrenytl ,s on aluminium and PVC are at the level of a c~ntact adhesive.
Summary of Examples 1 to 3 With all three esters, the pl~ er bia~ti,) shows very good c),a"od~ylate com~ coupled with high stability in storage in quantities of up to 50% by weight.
Whereas the setling times on limba and EPDM only inc,rease beyond a pl~sli~r content of 40%, sl, e, IyU ,s are re~uc~rl by plaslici er contents of20% (BE, MOE) and 30% (AE), but are still at the level of contact adhesives.

Examples 4 to 6 The influence of pl~slici~er~ on the impact sl,e"yl~l and moisture resistance of the various c),a"oa~ ylates is illusl, ~led in Tables 4 to 6.

Table 4: Influence of the rl~-s~ic.; ~r T iaceli" on the 51 ,e,a,/l""~ Stre of the Ethyl Ester Example Addition Ester Quantity Sl,ed,/l",~acl St~e"gtl, [%] lCJ/ClTt2l (Steel Cube) 4a None AE - 18.5 4b Triaceti" AE 10 23.6 4c Triacetin AE 20 24.8 4d T~ia~tin AE 30 26.5 In the case of the ethyl ester (see Table 4) the ~- ~rlitiGn of pl~slic;-er leads to an i"a~ase in impact sb~"~U" i.e. the aJl~sive bond beco-"es more elastic.
The butyl ester ( cc Table 5) shows a similar result to the ethyl ester.
15 The impact slre"~tl~ which in the case of the pure ester, is d;slin~Aly abovethat of the ethyl ester in view of the greater chain length is further improved by the addition of triacetin.

H 1867 PCT ~7 Table 5: Influence of ~e pl~s~; ar T~ tin on the Sl -e~ "~a~t St~
of ~e Butyl Ester Example AdditionEster Quantity Sl,ea-/l",~acl Sbell~tl l lcJ/~]
(Steel Cube) 5a None BE - 30.4 5b Triacetin BE 10 32.0 5c Tl iaceti" BE 20 33.0 5d Triacetin BE 30 33.2 5e Triacetin BE 40 Not Measured 5f Tliaoelin BE 50 Not measured In the case of the MOE (see Table 6) the ~-J- Iilion of l, iacetin leads to a distinct inuease in impact st,e"~U,.
Table 6: Influenoe of the Plaslici ~er Tl iaceti" on the Impact St,e, l~l h of the Ethyl Ester Example AdditionEster Quantity Shear/lmpact Sllellyll [%] [Ncrn/cm~]
(Steel Cube) 6a None MOE - 27.2 6b Triaceti., MOE 10 39.2 6c Triacetin MOE 20 44.3 6d Tl iaceli" MOE 30 48.8 Summary of test~ 1 to 6 The viscosity and stability in s~~ e of the ethvl ester is not adversely ~nr_~J by the addition of up to 50g6 by weight of the ~ r L ia~tin. the setting times on EPDM and PVC are not si~,)ifi~"U~ i"or~ased either. Only the setting times on limba are lor~er than 60 sec~ ,~s for a pl ~-lic-;-er conte"t of 40% with no added accelerator. The aben~Jtll values on aluminium and PVC fall to the level of c~ ~A ~JI ~sives above a rl ~ ;-er c~nten~ of 30%.
The bonds b~o",e i"oreasi. "~Iy more 6~
The inco,~,dtion of ~iao~in in the butvl ester leads overall to propei ly changes no Jifrere"t from those pr~d~d by its i"cG",Gr~tion in the ethyl ester. In the short-time slo~ga test, a ~l~slic-i~er co,)tent above 40%
procluces a Jisli".1 i"of~ase in viscosit~ after 10dl80~C while the slre"~l,s on aluminium are at the level of a oonlacl aJhesive for a ~ -;-er oo, ll~l lt of only 20%.
The methoxv ethvl ester shows very good pl~lic-i~ar coi"patibility in regard to stability in slor~ya. The setting times on EPDM and limba are acceptable up to 40% while the slr~"ytl, values are at the level of conldcl adhesives above 20%.

Table 7: C~")~a, ison. T, iac~ti" Wlth and Wlthout 0.2% of PEG~00-Dimeth-acrylate as Accelerator in Cyanoa~ylic Acid Ethyl Ester CGmposition Stora~e Stability Settin~ rlme Sl.~n~tll Tnacetin Acccle.dtor Vscosity Vscosity EPDM Limba Aluminium mPas afler [s] [s] [Nlmmq 10d/80~C
10% - 131.3 423.0 12 55 19.3 25% ~ 183.0 487.4 17 ~60 15.3 1o% + 132.0 709.3 8 20 17.2 25% + 186.2 632.6 14 45 13 3 Res~ ~lts - ~t~~ility in slura~ improved by ~--J-J~t;~ of an accelerator, - s~Ui. ,~ times on limba accelerated by ~ tion of an A~lerator and - st~ Jtl .s all at the same level.

The tests were based on the following ...eU.GJs;
1. Viscosi~y was determined as follows:
cone/plate measuring system, Visco~ity at 20 ~ 1~C.

10 2. The setting time of all the aJI ~esive ~."positions on the materials was dete""ined as follows at 20~C t 1:

EP~M: A round solid rubber cord (dia",eter 13 mm) of ethylene/propylene terpolymer (EPDM) was r,eshly cut. 1 to 2 drops of aJI ,esive were d~plieJ to the surface and the ends of the rubber cord were i"""ed:~ely fitted toyell,er.
The setting time is the time elapsi"~ before the ~aterial tears.
Aluminium: The time at which two freshly cleanecl and Lor,Jeul alu-minium tubes (A = O.S cm') showed measurable resistance to shiflil ,9 was determined.
Wood material: Pieces of limba measuring 100)~5x10 mm were over-lappingly bor,J~cl. The time elapsing before early adhesion occurred was the setting time.
2~ PVC: The time ela~si"y before two cle~ned (Jey,eased) PVC
strips (measuring 10~5~ mm) L,G"Jed with a 10 mm overlap c~sed to aJl,er~ to one a"otl,er after breaking apart at the bGIlJeJ surfaces was cJete""i"ed.

30 3. Tensile shear alle,lyU~s were Jele""i"cJ as follows:

The test spe~.,~- ,s measured 100~5x1.5 mm and were L~nJ~d over an area of 250 mm2 with a 10 mm overlap. Aluminium plate was deaned and sand~ the PVC was ll.e.~ly cleaned (cJey,eas6d).
Five bondin~s were carried out and the results were e~ressed as the mean values. The test cor,JiliG"s were as follows: the tensile testiny IlldChill~3 ope~led with a rate of advance of 10 mm/min. Curin~ took place over a period of 6 days at 22~CI40% relative air humidity (air-cor,Jition~J at."o~Jl,ere).

4. Shearrllllpacl alle~ was determined in a~cord~"ce with DIN 29653 at room temperature. The steel cubes were L orlJeJ over an area of 1 c~. ,

Claims (8)

21

1. A cyanoacrylate adhesive containing an added ester, characterized in that at least one partial and/or full ester of monobasic or polybasic aliphatic carboxylic acids containing 1 to 5 carbon atoms directly attached to one another and monohydric to pentahydric aliphatic alcohols containing 1 to 5 carbon atoms directly attached to one another is used as the ester the number of carbon atoms directly attached to one another in the other aliphatic groups being at most 3 where one aliphatic group contains 4 or 5 carbon atoms.

2. A cyanoacrylate adhesive as claimed in claim 1, characterized by monohydric to pentahydric alcohols and more particularly dihydric to tetrahydric alcohols containing 1 to 5 and, more particularly 3 or 4 carbon atoms directly attached to one another.

3. A cyanoacrylate adhesive as claimed in claim 1 or 2 characterized by monobasic carboxylic acids containing 1 to 3 carbon atoms.

4. A cyanoacrylate adhesive as claimed in at least one of claims 1, 2 or 3, characterized by esters which are free from catalysts and, more particularly,free from alkali metals and amines.

5. A cyanoacrylate adhesive as claimed in at least one of claims 1 to 4, characterized by the following cyanoacrylic acid esters: ethyl ester butyl ester and methoxyethyl ester.

6. A cyanoacrylate adhesive as claimed in at least one of claims 1 to 5, characterized by up to 50% by weight and preferably up to 30% by weight of ester based on the adhesive as a whole.

7. A cyanoacrylate adhesive as claimed in claim 6, characterized by 20 to 50% by weight of ester and preferably 30 to 45% by weight of ester, based on the adhesive as a whole.

8. A cyanoacrylate adhesive as claimed in claim 1, 2 or 3, characterized by triacetin or diacetin as the ester.