CA1039892A - Method for stabilizing polyester amides - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE:

Known method of producing polyester amides, if the starting material includes condensed-in hexamethylene diammonium adipate (AH salt), result in the formation of a skin of infuse-ble and insoluble material on the surface of the polyester amide melt when the product is kept in the molten condition in open, heated storage containers. When additional polyester amide is added to the melt, the skin is easily torn and passes into the interior of the melt in the for of solid or jelly-like pieces.
If the pieces of skin get into the applicator feed lines and into the applicators themselves, the uniform application of the product is either impeded or shut off completely, resulting in inconve-nient and expensive cleaning operations. While it is known that polyester amides can be produced without the formation of a skin, such processes do not include the use of AH salt. The use of the AH salt, however, is an advantage in that it increases the rate of crystallization of the polyester amide, as well as increasing the number of glueing operations per unit of time. According to the subject invention, the method of stabilizing polyester amides containing AH salt comprises the use in combination of: phospho-rous acid or an alkyl or aryl ester thereof, or both; triphenyl phosphine; and sterically hindered phenols; in an overall amount of preferably 0.01 to 0.5% by weight in relation to the overall amount of polyester-amide-forming initial substances.

Description

1~13989~2 . A }~lo~m method ~or producing polyester amides is by fu-sion condensa-tio.n o~ glycols~ cycloa.liphatic or aliphatic or both, diprimar~ di~lines and dicarbox~ltc acids or ~J-aminocc~rboxylic acids or both, or lactames, pre~'erab:l~ in the pre~e.nce o~ ca-ta-lysts, possibly i.n the presence of stabil.izers a~d other addi-tive~, the me-thod being characteri~ed in that only 2,2-dimethyl dihydroxy propane is used as glycol~ ~he products thus obtained are for use mainly as raw materials for hot-mel-t adhesives.
It ha.s been found that polyes~ter amides of -this ki~d, if they contain condensed-in hexamethylene diammoDium adipate ("AH salt~') as the initial material supplying the amide groups 9 have inadequate fu~io.n stability, i.~ man~ cases, for use as hot-~: melt adhesives ~his is particularly so i~ the product is kep-t in the molte.n co~dition i.n open heated storage containers, so : that any applicatio.n uni-ts, such as no2~1es, applica-tor roller3, . rolls~ spray-guns, or the like may be supplied b-y p~unping.
.. Dependi.ng upon the le~gth'of time the air is allowed to act upon the sur~ace of the polyester-amide melt, there is a more ..
or less pro.nou~ced f~rmation o~ sl~in7 the ski.n cQnsisting o~ i.n- ' ~usible and insoluble materialO When the container is topped up '-~
with ~resh polyester amide, this ski.n is easily torn and thus passes i~to the interior of the melt in the ~orm of solid vr Jel~
like piece~ whe~ce it is apt to get into the applicator feed .:`
J lines and into the applicators themsel~e~d ~his i~terferes with ~.
the uniform applicatio~ of the product or shuts o~f the flow com-pletely, requiring inconvenient and expensive cleani~g operations.
~or this reason~ it is desirable to preve~t the formation of s~in ' i under the condltions mentioned, b~ discovexi.ng suitable combina~ . .
- tions of stabilizers, or at least to slow do~m this ski.n forma~
'~ 3~ tion so that it does ~ot cause trouble in pra~tice.
'~his unwanted skin formation does not occur i~ the pxo-duction of polyester amides according to oMe kno~ method~ even - ' ~
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1~39~392 . in the absence of stabi:Liz~rs o:f any kind, i~ the amid~ ~roups .
I contai.ned the~ein are derivedt not from AH salt, but from .~ml-- nocarboxylic acids or -the lac-tames, o.n which these are baEied.
However, -the ~ole or predo~ ant use of AH salt i~i the produc-`` tion of polyester amide~ is freQuently an advantage, since -the - polyester amldes thus obtained cxy~tallize s~bstantiall~ faster whe.n the melt is cooled than polyes-ter amides co.~tai.ni.ng co.n-~. de.xised-in amino acids~ especially ~ -aminocaproic acid and capro-~ lactam, .instead of the AH saltO The higher crystallization ve~ ..
locity produces faster se-tti~lg of -the adhesive compounds9 which - in turn make~ ~t possible to carry out a larger number of glue- :
~ -i~g operations per unit of time which, from the poi.nt of view of efficiency~ is o~ten desirable or demanded~ qlhus the stabili-zing of polyester amides contai.ning co.ndensed-in AH salt9 i.n - order to preve.nt skin formatio.n by thermal-oxidatio.n loading is economica~y i~.port~n-t~
~: Another co.nsideration relating to the stabilizi.ng of - polyester amide~i containi.ng conde.nsed--i.n AH salt agai.n~it ski~
formatio.n is ~e requireme~it that the products be as light as pos- i sible i.n colour and so remain, so that when the pæts to be glued are pressed together, any excess glue does ~ot spoil the appea-` rar.ice of the material in the vicinity of the glued joint. ~:
-.................... It has now been found that polyester amides co.~itai.niinig .
-.~ residues of onie or more dicaxboxylic acids, neopentyl glycol, and :~
hexamethyle.ne diammoni~un adi.pate, and p~ssibly additio.nal resi-dues of ~-aminocaproic acid, e.dhibit both a light colour and de-: .
. layed skin ~ormation on the surface of the melt as a result of :.
. the action of ai~ thereon, if -they are produced i.n the presence of a combi~atio.n of stabilizers co~sisting of:
30 - ~) phophorous acid ox an alkyl or aryl ester -thereo~ .
: or both, .. - B) triphenyl phosphi~e~

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! - C) a sterically hindered phenol, wherein the total weight of stabilizer composition is between 0.1 to 0.5 weight percent, based upon the combined total amount of polyester amide-forming starting materials and the weight ratio of the components A:B:C is within the following range:
1-10:1:1-40.
Components A to C contained in the combination of stabi-lizers are known per se and also in certain combinations, but not yet in a combination of all three classes of substances. Nor was it known to use this combination for stabilization against the thermal decomposition by oxidation of polyesters, polyamides, or polyester amides. It is known that oxidizing polyamides lead to cross-linking, and that this cross-linking reaction may be inhibited by the presence of anti-oxidants (V.V. KORSHAK, T.M.
FRUNZE, "Synthetic Hetero-Chain polyamides", Israel Program for Scientific Translations, Jerusalem 1964, page 279). It is therefore obvious to prevent the formation of skin on polyester amides by adding anti-oxidants. While it is well known to use compounds A
to C as anti-oxidants, when all three components are present simul-taneously, they produce the desired stabilizing effect which does -- not occur when the components are utilized individually or in a :- ~
single combination. This fact could not have been derived from what was already known.
Components A to C are preferably used in amounts of 1:
1:1 to about 0.5-:0.5:2 by weight, in which A to C are interchan-geable at will and the data for A relates to phosphorous acid.

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The sum of components A, B and C preferably amounts to between 0.1 and 0.5% by weight, in relation to the total amount of po---~ lyester-amide-forming initial materials. However, it is also possible to increase the concentration of components A and C, individually or together, to about 10 times the given values.

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This produces no disadvantages, but neither does it produce any appreciable advantages.
The choice of sterically hindered phenols is known to be not very critical; the fol:Lowing compounds may be used with practically the same results:

- 2-Methyl-6-tert.-butylphenol 2,6-ni-tert.-buty1-p-kresol ' .' : ' " .
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2~2'~M~-th~lenbis-(4-methyl-6--tert,-butylphe.nol) ; 2~6-~iisopropylphe.nol :~
4~-Methylenbis-(2~6~ditert~-buty~lphenol) -(3~5-DitertO-buty~ hydro~yypheny~ rop~onic acid es- ~~
i.
:- ter o~ pen-taerythritol ~:
2,6-Ditert.-butylphe.nol Other representati~es of -this class o~ substances may `-~: be gathered from7 among others, the boo~ by J. VOIG~ he Stabi-lizing o~ Plastic agai~st ~ight a.nd Heat~'j Spri~ger-Verlag ~erlin/Heidelberg 1966, page 595 614~
Component A may be phosphorous aoid or any desired ester of this acid; it is to be assumed that i~ esters are used~ these will be split of~, under the poly-co.nde.nsation co.~ditio.~, hydro- :
lytically, i.nto free acid a~d the corresponding hydro~y compoundsO
- This emerges from the fact tha~, as of a speci~ic molar concen-tr~tion of com~o.~ent A9 similar decomposi-tio.n pha~om~.~a oaour to the same axtent in polyester amide during the pxoduction thereof9 and these can pe attributed o~ly~ to one common case~ ~amely the ~t prese~ce o~ free phosphorous acidO In this co.nnection9 it is .~ :
i~material whether component A ccnsis-ts of the acid itsel~ or o~
`. an equimolecular amount, to this acid~ of any desired trialkyl or itriaryl phosphiteO ~he maximum amount of compound A, in rel~tio.n -;
to its phosphorous-acid content, is about 0~16~ by weig~t~ in re~
lation to the total amount of polyester-amide-forming initial maD
terials; at higher conce.ntrations7 the end product shows signs o~
. unwanted diæcolo~ation.
It is pre~erable to add stabilizers A to ~ to the poly-.~ ester-amide-~orming monomex mixture, since thiæ way the optimal .- ef~ect of the polymer i~ obtained as regards colour and thermal ;` 30 oxidizing stability; it is not impossible, ho~tever, to add all ora par-t of the stabilizers in an ad~anc~d stage of the polyester~
amide productio.nO .
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T.he char.;lc-terlstic clata given i.n -the .~ollowing examp:les were deternu.ned as ~ollo~rs:
the reduced viscosi~y, ~ red, was de-termined according -to the me-thod given by W.R O SOR~NSO~ and T .~. CAMP~LL, "Prepa-rative Methods of Polymar ~hemistry", In-terscience Publishers Inc~, New York 1961, pages 38-~0, in m~cresol at 30C, the co.n- . :
centrat10n being lgm of polymer in 100 ~ of ~olve~-t.
The colour of the melted polymers was measuxed wi.th a "~ovibo~d ~intome-ter" ~ade by the firm of '~intomer ~tdo~ of Sa~
lisbury, E~gla~d, and give~ iD l'~ovibond-Scale" v~lues~ This sca~
le co~sists of sets of glass filters with li.nearly~staged permea- .
bility for the colours red, yellow9 and blue. Any desixed colour . .
can be imitated a~d numerically indioated by a suitable combina-tion of these three sub-tractive base colours. The me-thod used is ~ :
. described in detail in two brochures issued by ~i~tometer ~td.
.. - ~ . .
e~ tled: "Colorimetric Chamical ~al~tical Methods~0 - ~he skin formatio~ is de-termined by placing 50 gm of po~
. lymer in 150 ml beakers and ~oldi.ng them at 180C in an air- !-circulating dryi.ng cabi.net~ ~he time taken for the appearance of the ~irst signs o~ skin formatio~ ~as determlned b~ ~oving the l .
surface of the melt horizontally witha glass rod (time I)~ and . . .
. the time -taken ~or the entire surface to be covered with a skin .. ; (~time II).
` The followi.ng procedures were used at all times in the -. examples given hereinafter: . ;
- 52.56 gm of adipic acid, 37.56 gm of 2,2-dimethyldihy~
droxy propane-1,3, 40.0 gm o~ he~amethylenediammonil~ adipate ~:
~ ` (A~ sal-t), and 130 mg of o~tyleneglycol titanate ~= reaction ~ro-`. duct obtai.ned by relating 1 mole o~ tetrabutyl titan~te with 4 moles of 2-ethylhexanediole~1,37 and distilli.ng off the butanol ~ -split off) were heated oontinuously i~ a 250 ml circuiar flask equipped with a stirrer and a descending cooler~ under ~ltroge.n, ~ .
.

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i for threehours, from 150 to 270C, under normal pre~ure, ln the presence o~ the amounts of ~tabilizers A to C gi~e~ below, the :'; reaction water being thus expelled. Then, at 270C, vacuum wa~
i~: applied, and this was increa~ed continuously within an hour from 760 to 10 torr~O Thls 10-torr vaccum wa3 main-talned at 270C for another two ~ours, after which the product ~as allowed to ~olidi~
fy under nitrogen in the flas~. ~he flask was the~ broken and ?i the content isolated. ~his produced the follo~Jing results:
,~ ~ .. , ... _...... . .. . _ _ Ex. No. . Stabilizer (mg)~red. ~ovibond Color Forming of . . A B C Red Yellc~ j :B.l~.esl~ ' n :
; . :~, : . _ I II :

1 1) _ _ 0,59 2,0 15 ~,3 5 8 ;
~: 2 240 _ _ 0,63 4, 30 1,0 7 13 `~ `
.. 3 1601) _ _ 0,56 4,0 10 9o 6 15 .- 4 801) _ _ 0,58 2,0 10 0,4 6 14 :
; 5 9002) _ _ 0,65 3,8 35 1,0 6 14 . 6 6002) _ _ 0,60 4,0 10 1,8 6 14 ,:` 20 7 3002) _ _ 0,60 1,8 10 o,6 6 15 .~ 8 _ 500 _ 0958 1,8 10 0,2 _ _ `~. :
: 9 _ 200 _ 0,63 2,0 10 0,3 6 10 :
_ 100 _ 0,60 2,0 . 9 0,2 6 14 '~
~: 11 _ 5o _ 0,57 2,0 20 0,1 _ . , __ . . . . _ . . . .
. 12 _ _ 5003)0,60 2,1 20 0'3 3 15 A'`~
13 _ _ 2000,58 2,0 10 0,2 _ _ ~`
.. 14 _ _ 1003)0,63 1,7 9 '4 10 12 _ _ 7o3)0,61 2,0 9 0,1 _ _ . 16 _ _ 1 oc4) o, 63 1,8 10 0,3 9 12 :;
: 30 17 _ _ 1005)0,57 2,0 10 0,4 10 13 `~
. _ _ _._ . _ .. _ 18 601) 200 _ 0,58 3,2 20 2,1 6 10 .~ 19 501) 80 _ 0,60 2,1 10 1,1 6 10 . ~
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, Ex. No. S-tabilizer (mg) ~,r~d.. I.ovibo.nd Color Forming of . A ¦ B C Red Yellow B~e ~hrs ) . . I II ~:
' ,. _ ~ _ . . . ~ . ~ ~ ' : ,, ; 20 _ 100 1004) 0,63 5~4 25 2,1 10 13 ~ ~ :
21 ~ 200 1305) 0,57 3,5 26 2,~ 9 12 . 22 1601) _ 1004) 0~58 3,2 20 4,2 10 16 10. ~ 23 801) _ 804) 0,62 2,1 10 1~1 9 15 ;~
¦ 24 1601) _. 5004) 0,59 5~o 20 4,2 10 14 .. . .. ~ _ . _ ~ , . ~ , ,.
. Example~ 1 to 24 contai~ stabilizers A to C either in- -~
: dividually or combi.ned i~ pairs. It may be see.~ that the time required for a skin to ~orm may be doubled i.n any case, almo3t regardless of their concentration, although in these case~ allow-; ance must be made for a deterioratio.n of the colou~

Ex. No. S~ r- ~nS~ ~ ~ed. ~ovibond Color ~Formlng of :` A ~ C Red ~ellow ¦Blue (hrs ) 20 - . l ................. l l I II ¦ . .
:' - _ ~ _ _ j_ ._ .. _ __ , ~
~oo1 ) 200 2005) 0,69 4,120 3,1 >20 ~ 20 26 2001) 2001005) 0.,58 4,1 15 3~0~20 ~20 . 27 2001) 2007o5) 0,60 4,1 15 3J1~20 ~20 ... 28 1oo1 ) 200 2005) 0,59 3,5 12 2,8 720 ~20 .. 29 1001) 1001005) 0,63 4,1 10 3,1~20 ~20 . 30 ~ol ) 5o 1005) 0,65 3,3 10 1~3 15 ~20 .. 31 5506) 1001005) 0,62 3,8 11 2,5~20~20 .. 32 2001) 2401007) 0,57 2,1 12 1,016 ~20 33 1001) 1502008) 0,60 0,9 10 0,8~20>20 ~ 34 2001) Z4013008) 0,60 3,6 10 2,3~20>20 : . 35 160 ) 1001604) 0,58 4~o 11 2,218 ~20 : 36 j20Ql) ~ 200 2509) 0,63 0,8 10 0,9~ 20~20 _ ~3 7 ~398~2 1) Phosphorous acid 2~ Triphenylphosphite ~ .

3) 2-methyl-t-tert-butylphenol

4) 2,6-diisopropylphenol . 5) 4,4'-methylenebis-(2,6-ditert-butylphenol) 6) Trinonylphosphite 7) 2,2'-methylenebis-(4-methyl-6-tert-butylphenol) :
.~ 8) ~-(3,5-ditert-butyl-4-hydroxyphenyl)-propionic acid ester of , pentaerythritol 9) 2,6-ditert-butylphenol Examples 25 to 36 show the superiority of using stabili- ~
zers A, B and C simultaneously, the formation of a skin under ~ :
thermal-oxidizing conditions of the melt being delayed, while the light colour of the product is retained.
If, contrary to the teaching of the known process des-cribed previously, the 2,2-dimethyldihydroxy propane-1,3 in the ..
polyester amides was replaced by an equivalent amount of ethylene - glycol, and the octylene-glycol titanate catalyst was replaced : with 60 mg of GeO2 in view of the known fact that polyesters ~.
containing condensed-in ethylene glycol are generally discoloured to a yellowish brown when catalyst containing titanium are used, it was impossible to obtain, with any of the stabilizer combina-. tions mentioned in Examples 25 to 36, Lovibond Coulour Numbers .. . .
~ (red, yellow, blue) any better than 5/40/3. There was also no .- improvement in the colour numbers when the 2,2-dimenthyldihydroxy . . .
propane-1,3 was replaced, during the manufacture of the polyester .:
amide, by an equivalent amount of 1,4-butane aio.le, thus reducing the polycondensation temperature to 245C; at this temperature, `~

. the thermal decomposition of titanium-catalyzed polyesters of 1,4-butane diole is approximatel~ equal to the thermal decomposi . tion velocity of germ'anium-catalyzed polyesters of ethylene glycol 8 ~

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1~3989Z
at 270C, so tha-t this choice of tempera-ture was unable -to cover up any minor but unwanted effects upon the conditions under .
investigation. It emerges from the tests that stabilizer combi~
nations of A, B and C can be applied only to the polyester amides :
produced according to the known process as described previously.
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Claims (3)

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

1. A method for stabilizing polyester amides, obtained by fusion-condensation of 2,2-dimethyldihydroxy propane-1,3, cyclo-aliphatic and/or aliphatic diprimary diamines, and dicarboxylic acids and/or.omega.-aminocarboxylic acids or lactames, in the presence of catalysts and stabilizers, and containing condensed-in hexa-methylediammonium adipate as the essential amide-group-supplying monomer, against thermal-oxidative decomposition, characterized in that the stabilizer used in a combination of:
A) phosphorous acid and/or an alkyl or aryl ester thereof, B) triphenyl phosphine and, C) sterically hindered phenols, wherein the total weight of stabilizer composition is between 0.1 to 0.5 weight percent, based upon the combined total amount of poly-ester amide-forming starting materials and the weight ratio of the components A:B:C is within the following range: 1-10:1:1-40.

2. A method according to claim 1, wherein the weight ratio of the components A to C is within the following range:
1:1:1 to about 0.5:0.5:2, said ratio based upon the weight ratio calculated as if component A were phosphorous acid.

3. A method according to claim 1, characterized in that the maximum amount of component A, in relation to its phosphorous-acid content, is about 0,16% by weight, in relation to the total amount of polyester-amide-forming initial materials.