CA2199813A1 - Polyamides as remoistenable adhesives - Google Patents

Abstract

The present invention is a novel remoistenable adhesive and an improvement in the bonding method for an envelope, a stamp, a sticker, a packaging tape or a label using a remoistenable adhesive, wherein the remoistenable adhesive is a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelic acid, azelaic acid, suberic acid and sebacic acid, and an alkyleneoxy diamine component consisting of one or more diamine compounds having the formula: H2N-CyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50.

Description

1 ~ 9 8 1 3 P~T/US ~ 5 / O 0 1 2 .
0 ~ OCT 1996 , POLYAMIDES AS REMOISTENABLE ADHES~VES

Back~round of the Invention The present invention pertains to remoistenable hot melt adhesives, and their application to envelopes, stamps, park~ging tape or stickers and labels.

To be water-moistenable, an adhesive composition must be activatable by moi~r~ g with water. The adhesive composition is a bonding agent which may be applied to one surface utili7ing a hot melt technique and to another surface using a water-moietenin~ teçhni~lue, so that the two surfaces are bonded together by means of composition. By way of example, such a composition may be applied by the hot melt t~rhniqlle as glmming for stickers and labels, stamps, I?~rk~gin,~ tapes and envelope flaps at a point of m~nllf~rtllre where the ;..~ e~ required for 15 hot melt application is available, the stickers and labels, stamps, paek~ging tapes and envelope flaps, nltim~tely being applied by the CO~Ulll~,. to other ~ r~res using the much simpler water-moi.etening terhniql-~, e.g. by moi~it~ g the adhesive coating prior to application to the other surface. The hot melt application is utilized where the required e~ .l is available becau~e it i~e a raI?id and econ~mir~l technique, 20 the water-moi~L~ technique is utilized ~ ,cisely because it doesn't require such elaborate eqllirmP!nt Overall, remoistenable adhesives are valued bcc~ e of their superior process speed, and their stre~mlining of process eqllip~-nt by elimin~tion of driers and other auxiliary equipment or the like.

In aU~ g to provide a single adhesive col~lposiLion which is to be applied to one surface using a hot melt technique and another surface using a water-moi~ning tecllniq~e, considerations arise which are not present in the provision of an adhesive composition to be applied by either technique alone. ~or example, most water-moistenable adhesives do not possess the requisite thermoplastic pr()pe~Lies permitting hot melt application of desirably smooth glossy coats thereof. Similarly, 8 ~ 3 P~/US ~ ) / 00 ~ 2 O ~ S
t~r~ifi~ble to form bonds by water-moistening techniques. On the other hand, once the composition has been hot-melt applied to a substrate, it must be able to resist elevated ~ ela~ul~, conditions likely to be found in its en-vi~vlllllc;lll without again becoming t~r~ifi.~l or undel~oil,g other undesirable changes, such as discoloration S (d~h~ g), over a prolonged period of time. Similarly, it must be able to wi~h~ 1 the various humid conditions likely to be found in its cllvi,o~ lclll without becoming tacky until it is actually moistened imm~ tely prior to use.

The tendency of the adhesive to undergo premature sealing is a problem not lQ yet fully re~e~içd by the prior art. Under humid conditions this adhesion is - measured in terms of the hllmi~lity blocking l~_c;!~;.. re at a given relative hllmi-lity ~~ (under a given load at a given l~lll~lalw~, for a given period of time). The blocking le~ r~ is normally l"easu,~,d in terms of the percentage tear O.~
with high levels of blocking producing high level of tear when the a&esive-bearing 15 substrate is remaved from the OppOF7~d surface. It is desirable to have- a remoistenable adhesive that resists blocking in extreme heat and humid col dilivlls.
Traditionally, non-block additives such as petroleum and ~,ylllllclic waxes and fatty amines have been incorporated to pl~Je,nl blocking problems. Typical of these are Acrawax C, a 140Q-143 C melt point aylllL~,Iic wax from Glyco Ch~mir~l~, erucyl20 amide, oleyl amide, N.N ethylenebisole~mi~l~ and the like.

Remoistenable water soluble polymers other than polyamides appear to be deliquescent, that is they tend to undergo gradual dissolution and liquefaction by the attraction and absv-~ion of moisture from the air, causing them to block at high25 hllmi~lity and lelll~alul~,: This can cause a serious problem during storage of products lltili~ing remoistenable adhesives. Blocking can be chalaelt;l~ed as any degree of adhesive bclwc~l~ touching layers of similar or dissimilar m~teri~1, such as occurs under moderate prcs~u~:s during storage or use. To achieve desired ~ro~c,lies prior art polymers require wax and tackifiers to plcvclll blocking and to 30 promote stability. The end result is that remoistenable adhesive products that suffer from blocking are rendered useless when they prematurely seal.

~, . . . ..

2 ~ ~ ~ 8 ~1 ~

Water soluble polymers like polyvinyl alcohol, PeOX, and PVP are known in liL~lalulc for their co~ ullding ability to form adhesives for remoi~e~ -g application. These hot melt adhesives provide several advantages for the envelope and pac~ n~ fl~ S and other related i-,.l--x~ s, including a very fast rate of 5 application, the ability to heat seal when remoi~ g is not required, and the fact that the water solubility of the adhesive will make the products recyclable.
However, these water soluble polymers require water soluble/insoluble t~rl~ifirrs and waxes to achieve the desired remoi~tenin~ properties. Rec~ e of the nature of the polymers and the use of t~r~ifirrs and waxes the adhesives are rendered with low10 blocking re~ re and low thermal stability.

Fl~n~n, U.S. 4,623,688, discloses remoistenable hot melts adhesives which are pl~aled from poly(alkyloxazoline) (having the general formula C3H4NO), a diluent and, optionally, a t~r~ifirr, plasticizer and non-block additive.
15 Like other known remoistenable adhesives, in order to achieve plcr~ d non-blocking, heat and hllmi-1ity re~i~t~nre, and bond strength ~r~e.Lies certain materials are added, such as t~r~ifiers, plasticizers, stabilizers and non-blockadditives.

U.S. patents 4,623,688; 5,053,484; 4,133,803; 5,086,162 all teach the ~yllLlle~is of water soluble polyamides. Polyamides have been produced for many reasons, but not for use as a remoistenable adhesive. Klein, U.S. 4,133,803, discloses poly~y~l~ylene poly~..hR polyamide thermoplastic adhesives. It pertains to a novel thermoplastic a&esive colll~lised of a polyamide product, and 25 can be pl~aled from relatively ine~ re and readily available ~yllLlltLic materials.
This invention was driven by the need for s~ti~f~rtory repl~r~ x for naturally derived materials. It elimin~tr-l the need for employing vegetable or animal-based dimer or trimer fatty acids which are usually in short supply, but did not disclose the use of the polyamides as a remoistenable a&esive.

Speldl~a, U.S. 5,086,162, also disclosed water soluble polyether amides produced by reacting polyaLkylene glycol (li~minP with dicarboxylic acids.
The object of the invention was to provide novel polyether amides with 2 7 ~9~ ~ 3 Wo 96/08538 PCT/US95/00124 Le~ mi-le units having u~ ov~d water absolbell~;y, and/or which are soluble in water. The patent provided a plurality of easily implemrntecl methods for making these novel materials. Uses for these novel polyamides include applications where good water absorption is desired, such as fabrics, where it is known that some 5 incorporation of moisture is useful in l~ducillg tel~y of the fabric to carry an undesirable static cnarge. The patent also teaches that the polyamides can be used for hot-melt a&esives, but the patent does not disclose or suggest the usefumess of the polyamide as a remoistenable adhesive.

Speranza, U.S. 5,053,484, ~ cll~ses polyether amides from ll~ixlUl~s of polyether ~ minrs and dicarboxylic acids. The amides are water soluble, and may also be used for hot melt adhesives. The purpose of the invention was to increase solubility, and provide easily imple~ ed methods of making these polymer materials. This piece of prior art also fails to disclose the polyamide as a 15 valuable remoistenable adhesive.

Sull~ ly of the Invention The invention is directed to remoistenable hot melt adhesives which are the product of a dicarboxylic acid sP1~cte~1 from the group con.~ g of adipic 20 acid, pimelitic acid, azelaic acid and suberic acid, and a polyoxyalkylene .li~",i"~.
This polyamide is characteri7rcl by the propel~ies of a remoistenable a&esive and an ollt~t~nrling balance of non-block chala~;leli~Lics under heat and high hllmitlity conditions combined with excellent bond strength without the aid of wax, t~rkifiers or antioxiti~nt~ and is an improvement over the prior art.
This invention is an improvement over known remoistenable adhesives used in the envelope and pack~ging industry and other related hl lu~Llics, and is also a novel use for known polyamide hot melts. These polyamides, though having water soluble tendencies, are also remoistenable in nature, and provide superior bonding 30 and are resistant to high te~ t;laLule and high hllmi-lity. Unlike prior remoistenable adhesives, the additions of additives such as waxes, t~rkifPrs and antioxidants are not required to prevent blocking and to promote stability in high heat and hnmitlity.
Thus the present invention provides an i ll~ v~ ent to the stability of the WO 96/08538 ~ 9 8 ~ 3 PCT/US95/00124 _5_ remoistenable adhesive in severe con-litioll~, and at the same time provides a new use for polyamides.

In one aspect the invention is an h~provell~ent in the bonding method 5 of an envelope in which an envelope, having a folding closure flap and having a film of remoistenable adhesive applied thereto, is stored for a period of time, after such time the remoistenable adhesive is moistened, and the flap is folded over onto the envelope and pressed against the envelope until bonded, the illllllovc;",c~ COlll~liSillg that the remoistenable adhesive is a hot melt co~ Lhlg of a thermoplastic polyamide 10 prepared from an acid component selPctP~l from the group collsi~lillg of adipic acid, pimelic acid, azelaic acid and suberic acid, and an alkyleneoxy ~ minP co,llpollellt con~i~tin~ of one or more ~ minP compounds having the formula:
H2N-CyH2y~(0C2H4)A~O~C}H2y~NH2 where y is 2 or 3 and x is 1-50.
Brief Des~ ,Lion of the Dlawillg~ ' Fig. 1 is a rear view of an open envelope in accordallce with the present invention illusLla~ g the application of the remoistenable adhesive; and Fig. 2 is a rear view of a closed envelope in accolddllce with the present invention illu~llalhlg the utility of the remoistenable adhesive.

Detailed Descliy~ion of the Invention This invention is a novel remoistenable adhesive and a new use of thermoplastic polyamides as remoistenable adhesives for their application in thep~r~gin~ and envelope industry and other related industries, such as application to envelopes, stamps, p~rk~ging tdpe or stickers and labels. Unlike prior remoistenable adhesives, polyamides such as these do not require the use of waxes, t~rl~ifirr~ and antioxidants to prevent blocking and to promote thermal stability in high heat and hllmi~lity. These thermoplastic polyamides are generally ~ alcd using a dicarboxylic acid sel~cte~l from the group con~ g of adipic acid, pimelitic acid, aælaic acid and suberic acid, and alkyleneoxy ~ .llillPS. The typical formula C~lu~l;S~S adipic acid and TTD ~ in exact stoirhiomPtrir ratio. However, , . . i ; ,i s ~, 2 ~ ~9~ ~ 3 ~C~/US 3 5 / ~ O ~
6 ~S ~ OCT 19~6 products made from adipic acid in conjunction with stearic acid, benzoic acid orsebacic acid and the TTD (li~mine also showed the remoi~tenin~ prol~e.ly. Low tohigh viscosity polyarnides can be màde for remoi.~ application by ch~n~inf~ the ratio of the acid and amine. Waxes and/or t~rl~fflers are not l-~ce~.y to show the S remoistenable ~rope,Ly in the present invention as they are in known remoistenable adhesives, but may be used in certain situations to increase the blocking r~si~t~n~e and thermal stability-.

Although certain U.S. patents teach the ~y~ SiS of water soluble 10 poly~mi-lPs, such as the ones that are the subject of the present invention, none describe the remoistenable ~r~ ies of the polyamides. These hot rnelt adhesives provide several advantage~ for envelope a~d p~c~in~ industries and other relatedif.~, incllJ-lin~ a very fast rate of applir~ti~ the ability to heat seal w~en remo;~t~ not ~ dj and the water solubility of the adhesive will make the 15 product recyclable. Water solubl~ polymers known in the prior art require water soluble/insoluble t;-~Lil-;~-:i and waxes to achieve the desired remoi~P~ pn~e.lies.
Reca~l~e of the nature of the pnor a~ polymers and the use ~f ta. L iri..~ and waxes the adhesi~res are ~deLcd with low blockillg I~S;~ e and low thPrrn~l stability.Polyamides show no need of t~ fiers and waxes to achieve high blocking r~si~ u~
20 and high th~rm~l stability, and ca~ be made wi~uu~ the process of form~ tion.
._ . . . . ............ ...
Polyamides ha~ been produced for many reasons, but not for use as a remoistenable adhesive. Some polyamides were created in l~ ol~e to a need for s~ti~f~rtory repl~ for naturally derived materials, and can be plcpar~d from 25 relatively il~ sive and readily available synthetic materials. Water soluble polyether amides produced by reacting polyalkylene glycol ~ minP with dicarboxilic acids were created to provide novel polyether amides w~h-t~h~l.A~Ami~ie units having improved water absoll,e~x;y, and/or which are soluble in wa~er. It also was a purpose of past polyamide inventions to provide a plurality of easily implemented 30 methods for making these novel materials. Still, this product has not been recognized for its usefulness as a remoistenable adhesive. The present inventiontakes all these economic and efficient advantages of polyamides and utilizes them in a novel way as remoistenable adhesives.

~ ~ ~ 9 8 1 3 WO 96108S38 ' PCTIUS95/00124 Figs. 1 & 2 illust ~te an application for the u~ vcment in the bonding method for closing an envelope wL~.e~ the remoistenable adhesive used isa polyamide. In the illustration, an open envelope, generally desi~n~ted 10, as shown in Fig. 1, having a folding closure flap 2, has a film of remoistenable S adhesive 4 applied thereto. The envelope can be stored for a period of time, after which the remoistenable a&esive 4 is moistened, usually by licking the adhesive,and the flap 2 is folded over along the crease point 3 onto the back face 6 of the envelope and pressed against the envelope until a bond 8 is created. The end result is a sealed envelope 20 as shown is Fig. 2. This application is only an example of 10 the use of polyamides as remoistenable adhesives. Other appli~tion~ include applying the adhesive to either the closure flap 2 or the back face 6 of the envelope or both, and/or using other envelope type products. The adhesive can be used in a similar ~ cl in conjull~;Lion with other forms of p~c1f~ging material, such as pac~in~ tape and the like.
Polyamides made from adipic acid and TTD (3, 3 (diethylene trioxy) bi~lv~ylamine) ~ min~ have been described in U.S. patent 3,883,090 for various applications, and several other U.S. patents (patent numbers 4,623,688; 5,053,484;
4,133,803; 5,086,162) describe the synthesis of water soluble polyamides using 20 oxyethylene or o~y~lol,ylene ~ min~s. These patents disclose that polyamides can be used as hot melt adhesives, but they do not describe or infer the remoistenable P~ LY of the polyamide.

Other water-dispersable polyamides can be plcpal~d by reacting adipic 25 acid with a ~ ."i~, such as polyethylene glycol ~ min~s, like triethylene glycol F (Jerri1...;..F~ EDR-148) or tetraethylene glycol ~ min~ (Jeff~min~9 ER-192) or a combination of the two ~ min~s. A combination of these higher diacids with adipic acid can produce water-soluble or water-dispersible polyamides. Increasing the amount of higher carbon diacids in CO~ljU" ;Lion with adipic acid results in30 polyamide with decrease in solubility. However, this can be coll~ellsa~ed by increasing the EO (ethylene oxide) content of a portion of the polyethylene glycol ."i,.f component. Jerr~lline'l9 ED 600, ED 900, ED 2000, D-230, D400 and D-2000 are examples of higher EO content polyoxyaLkylene fii~---il~PS which may be 11 9 9 8 ~ 3 ~;Xl~ 9 5 ~ a ~ ~ 2 -8~ S0~0C`r~
employed. Thus, in particular, Dimer Acid can be used in combination with adipicacid when triethylene glycol ~i~min.o or tetraethylene glycol cliqmin~ are employed in combination with the polyoxyallylene ~ Ps Jerr~-"i" ~ ED 600 or D400.

Ihe ~l~f~ .led eleln~ntC in the general reaction are adipic acid and TT~ Diamine. It is most preferable to add stearic acid, benzoic acid or so".~ ",~s sebacic acid, to the leaclion to ~ ase the solubility. The reaction of TTD and adipic acid should be used in equal stoielliom~tric ratio, however, for reactionl~lweell adipic acid, TTD, and sebacic acid the limit of sebacic can be between O-10 25%. For the reaction of TTD, adipic acid, and stearic acid the limit of stearic acid ~~ can be O-l5~
~ ..
The remoi~ adhesives have-many applicatio~c and can be use~
in the envelope industry aC well~ as in the p~ r~ lu~ for paper tapes as 15 remoistenable-paper tapes. In addition, the water solubility of the a&esive provides a completely repulpable tape for p~et~inf~ application and is thus recyclable. The hot melt a&esives used in the inverltion are able t~ adequate bond ~
so that in warm l~ alultiS the-seal is not jeu~ li~i. The pol~id~s display eY~e1lPnt hnmi-lity le~ , high th.o.rm~l stability and showed good blocking 20 lesisL~ce at high ~ e and high l~ ;rlily wi~uul the aid of tfle~ , waxes or formulation. Some of the poly...;~re tend~t~ have slou~ set time, but this can be de.;lease~ by using some fa~t setting wa~es.~ -- - - The present in~,ellliol~ is a~lvallla~us over the prior art/ba~ruulld 25 technologies i~that they resist blocking at high l~...).iAt~y and lelllpeialul~,. The polyamides employed in the invention do not require these additional materials to achieve these desirable pro~lies~ -; n-While the remoistenable adhesives of the invention may be made 30 solely from mixtures of ~i~min~s and mix~ures of diacids which also showedremoistenable propellies, in some cases in order to achieve a particular proL~ ly for certain applications or to reduce the cost of the adhesive the polyamides may beoptionally form~ te~ with waxes, tackifiers, antioxidants, melt viscosity modifiers, ~ ~ ~98 11 3 WO 96/08538 PCT/USg5/00124 g and the like, provided that the additives do not themselves adversely affect the water ~ispçr~hility of the adhesive forrn~ tion.

Although the form~ tP~l products also showed water solubility/di~.,.~ibility S and remoistenability properties, to achieve certain desired levels t~rlrifiPr~, waxes and antioxidants may be used to extend the adhesive ~ lies of the system.
Suitable t~r~ffl1Prs are (l) natural and modified rosins such, for example, as gum rosin, wood rosin, tall-oil resin, tli~tille~l rosin, hydrogenated rosin, ~ d rosin, and polymPri7P~l rosin, (2) poly~ ,e resins having a softening point, as 10 (1~ Pd by ASTM method E28 58T, of from about 60 to 140 C, the latter polyl~.~elle resins generally resulting from the polylll~,li,~Lion of terpene hydrocarbons, such as bicyclic mono-terpene known as pinene in the ~lesel~ce of Friedel-Crafts catalysts at moderately low temperature, (3) phenolic-modified terpene resins such, for example, as the resin product rPsnlting from the conrlens~tion in an 15 acidic mrtlil-m, of a bicyclic terpene and a phenol; (4) aliphatic petroleum hydrocarbon resins having a Ball and Ring softening point of from about 60 to 140C, the latter resins resllltin~ from the polylllc.i~dLion of monomers co~
primarily of olefins and diolefins, (5) glycerol and pentac.~yLl~ ol; (6) esters of rosin or modified rosin; (7) styrene resins and modified styrene resins; (8) hydroabietyl 20 alcohol and the phth~l~te ester thereof; and (9) ~lirh~tir, aromatic and aliphatic/arollldlic copolymers and their hydrogenated CI~U11lel~L~. These tackifying resins are present usually in an amount of about 5 to 40% by weight of the a&esive.

Antioxidants or stabilizers which may be employed in rernoistenable hot melt 25 compositions include phenolics, amines, and quinones or the like. Especially useful are the high molecular weight hindered phenols and multifunctional phenols such as sulfur and pho~phol~,us-co~ g phenols. Hindered phenols are well known to those skilled in the art and may be chdldcL~ d as phenolic compounds which also contain buLky radicals in close proxirnity to the phenolic hydroxyl group thereof. In 30 particular, tertiary butyl groups generally are ~lbl~ rcl onto the be~ e ring in at least one of the other positions relative to the phenolic hydroxy group. The ~,sellce of these ~b~ r~tlir~l~ in the vicinity of the hydlo~yl group serves to W096/08538 2~ ~ ~ 9 8 ~ 3 P~ 3~100124 retard its ~ chillg frequency amd correspondingly, its ~I,ac~ iLy. This steric .~allce thus provides the phenolic compound with its st~hili7in~ ~lo~llies.

The polyamides of the present invention show the ability of abso,l,illg 5 moisture without becoming deliql~escçnt Deli-luesce"l is the tendency to undergo gradual dissolution and liq~ tof~rtion by the attraction of moisture from air.
Although the polyamides absorbed 30% moisture they were not deliqllesrent7 in fact they desorbed after sitting in ambient conditions. Polymers normally used as remoistenable adhesives like PeOX are deliql~escent (tending to undergo gradual 10 dissolution and liquefaction by the attraction of moisture from air) and stays in that form even when they are removed from high hllmi~lity. This chara~ is~ic causes them to block at high hllmi(lity and Lelllp~,ldlUl`e. To 1el~,. ",il-~ if the polyamides are deliqll~scent a moisture absorption test was ~l.ni~ d and is explained below.

Examples:
Typical re~rtion~ that are the subject of the invention are shown below, but the present invention is not limited to these alone, nor does the invention preclude any similar applications or snb~ s:

1) Adipic acid + lYD Diamine = polyamide;
2) Adipic acid + Stearic acid + TTD Diamine = polyamide;

3) Adipic acid + Jeffamine EDR-192 = polyamide;

4) Adipic acid + Jeff~min.o EDR 148 = polyamide;

5) Adipic acid + Jerr~ i ,e EDR 148 + D-230 = polyamide;

6) Adipic acid + Jerr~"il~ EDR 148 + D-230 + sebacic acid = polyamide;

7) Polyamide from equation 1 + wax + tackifiers = formlll~ted polyamide;
and 8) Polyamide from equation 5 + wax = formlll~t~d polyamide.

Compound Desc~ ions:
TTD - H2N-(CH2)3-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2 EDR-192- H2N-CH2-CH2-(O-CH2-CH2)3-NH2 EDR-148- H2N-CH2-CH2-(O-CH2-CH2)2-NH2 Wo 96/08538 2 ~ 3 PCT/US9S/00124 J~rri...-i-.~ D-230 - NH2-CH-CH2-[O-CH2-CHlz~NH2 Adipic acid (hexane dioic acid) - HOOC-(CH2)4-COOH
Sebacic acid - HOOC-(CH2)8-COOH
S Stearic acid (Oct~lP~r-nnic acid) - CH3-(CH2)l6-COOH

The polyamides employed in the invention may be prepal~d as described in Example 1 of U.S. 3,882,090. ~oflifi~tions of the recipe given below for illustrative purposes only, it being understood that ~ose skilled in the art can readily 10 modify the recipes without departing from the invention hereof:

Parts by Wei~ht (lj Adipic Acid 146.14 Triethylene Glycol Diamine 148.0 (2) Adipic Acid 146.14 Tetraethylene Glycol Diamine 192.0 (3) Adipic Acid 146.14 TTDI Diamine 220.3 4,7,10-triox~ lPc~nP-1, 13-1~ P

Polyamide melt viscosity can be controlled by adding small amounts, 25 typically less than 5%, preferably 0.5-2.5% based on total acid weight of monoacids such as stearic or benzoic acid. An example recipe is given below:

(4) Adipic Acid 145.4 Stearic Acid 2.7 TTD Diamine 220.3 FlçmPnt~ such as adipic acid, ~li,.."i"~, stearic acid, benzoic acid, and sebacic acid enh~nre the water solubility of the ad_esive. Non-es~çnti~l c~ such as wax, t~ ifiPr~ and antioxidants co"~ ule p~opel~ies that are lacking in particular ~ ~ 9 ~ 8 ~1 3 wo 96/08538 PCT/USg5/00124 situations. Wax increases setting/lo~l ulg the set time/filler, t~rL-ifiPr~ helpt~rkiness and antioxidants allows use at high temperature without de~lad~Lion.

ExpPrimPnt~ were run to lçterminP and verify the herein asserted S chara~:Le~i~lics and nature of polyamides as remoistenable adhesives. The results are shown below and in-lir~tP that polyamides, when used as remoistenable adhesives,display an ~ .l;,,g balance of non-block characteristics under high heat and high hllmi-lity conditions combined with excellent bond strength without the aid of wax, tackifiers or antioxidants.
In the moisture absorption test of NP-2068 (parts by weight: adipic acid 145.4; stearic acid 2.7; and TTD Diamine 220.3), the batch of NP-2068 was drawn to film for the test. Four strips of paper were cut and weighed and placed in a ~l~p-sirç~tor at 55-60% hllmirlity and room lelllpeldLu~ of 70-75F. A second set 15 were placed at room ~ e.a~u~e in a desiccator with water at the bottom at 70-75F
with a relative hllmirlity at 95-98%. After 16 hours, the samples were weighed and left out in ambient conditions. There was an initial l;~rL i~lPS.S, but after 24 hours, they were weighed and displayed a lower weight, thus evidencing desorbing of llloi~Lul~. This desorbing quality helps the sample to resist blocking. The results of 20 the absorbency testing are shown below in Table #1:

9 8 ~ 3 Table #1: Water absorption/desorption data NP-2068 Sample Wt. after % Water Wt. in g. % Water % Water wt. in g. 16 hrs. absorp- at RT in sample desorbed in tion and 50-RT/90- 55% RH
95% RH for 24 hrs.
Sample 0.589 0.769 30.6 0.604 1.5 29.1 A

Sample 0.451 0.597 32.4 0.459 1.7 30.7 B

RT = Room Te~ aLul~ RH = Relative ~umillity NP-2068 = parts by weight: adipic acid 145.4; stearic acid 2.7; and TTD
Diamine 220.3 (samples A & B are sepal~le samples of NP-2068).

To .l~l~. ",;".o the polyamides non-blocking ca~abilities and its thermal 15 stability, three test were run on 9 dirr~ samples of various mixtures of polyamides: (1) A remoistenability test 24 hrs; (2) A blocking test at 140 for 24 hrs; and (3) A 84% or 93% hllmi~lity rcs~ re test for 24 hrs. The results of these tests were employed to distinguish polyamides from formerly used remoistenable adhesives, illll~l".l;..~ polyamides improvement over the prior art.
The test to delp~ .--i.~P the remoistenability of hot melt adhesives is used to ~le~ wL~lller a l~,llloi~ able hot melt adhesive, after initial application, gives ~deql-~tt~. bonding when remoistened and mated to a particular substrate. In this particular test, t_e sample is heated to 300F. A sheet of paper is 25 taped down on which the adhesive is drawn down with a metal draw down bar. The adhesive is allowed to cool. After which the paper is cut into 1/2" strips with a l~.ick..loss of beLweell .6 mil. and 1 mil. These strips are allowed to sit at low hllmi(1ity (50%) for two hours. The strips are moi~ed with room tel.lpe-~lu~c;
water and imm~ tPly pressed onto a second piece of bond paper with m~.f1ium 30 finger pl`eS~ul~ as if you were sealing an envelope. This test is done with various levels of moisture applied for each adhesive, noting the amount applied as little, m.or1illm, or heavy moisture on each strip. The sealed strips are placed in low wo 96,0853g ~ ~ ~ 9 8 ~ 3 PCTrUS9S/00124 hllmitlity (50%) eIlvilo~lell~ for 24 hours. After which the strips are pulled from the bond paper I-,coldillg fiber tear observed. A side by side COIll~dliSOll done by ~c~roIlllillg a test within adhesive lot showed to have excellent remoistenability along with the test sample is . ~IL~IL. Also be sure to ~ltrrn~tr the test and known 5 sample strips with moi~tç~ing and bonding to the substrate to insure coIll~dldble amount of moisture is applied to each adhesive type. The percent of ~Iber tear is rated as excellent (40% or more), good (10% - 40%), or poor (less than 10%). An adhesive has passed if at least one third of the heavily or moderately moistenedstrips have e~r~qllent or good fiber tear ratings. The test sample must peIroll~l as 10 well or better than the controlled to pass this test. The results of this test as applied to the nine samples are illustrated in Table #2.

The test to deterTninr the blocking potential of hot melt adhesives is used to cle~ wL~LlI~l remoistenable hot melt adhesive, after initial application, 15 will have undesirable blocking characteristics under ~les~ule and heat. The procedure for this test is the same as the remoistenability test up to the point where the strips of paper are allowed to stand in low hl-mitlity for two hours. After this step, the strips of the control and the strips of the test adhesive are placed on a tray, adhesive side up. A strip of dried bond paper is placed on top of each adhesive strip. A 100 gram weight is placed on top of each strip, and the tray is placed in a 120 oven for 24 hours. Another tray of specimens is placed in room ~eIllpcl~Lule for 24 hours also. After the 24 hours, the strips are observed noting the degree of a&esive stirking or picking to the plain bond paper that was placed on top of the adhesive area. A side by side co~ a.ison is done by peIrol~ g a test with an adhesive lot shown to have exrçllPnt blocking resi~t~nre. The degree of picking is rated as excellent (no picking, paper falls away without having to pull the paper), good (very slight picking), okay (~ignifir~nt picking but no fiber tear) or poor (fiber tear of the bond paper is in evidence). When the adhesive has passed at least five or six strips of excellent or good pick rates. The adhesive fails if there are any 30 specimens with a "poor". The test sample must pclrOIlll as well or better than the controlled to pass the test. The results of this test as applied to the nine samples are trated in Table #2.

w096/08538 ~ ~ ~ 9 8 ~ 3 ~l".~3~100l24 The hllmitiity ~ e test is set up exactly like the blocking test, where one set of strips is placed in 84% hllmi-lity for 24 hours and one set of strips is placed in 94% hllmir1ity for 96 hours. The results of this test as applied to t_e nine samples are i~ rd in Table #2.

PCT/US ~ ~ / O O 1 2 C ~tUS O 2 OCT 1996 C~ ~ ~
ca A

~ x e~- _i ~ ~ 3 ~

~ x ~ æ Z , ~ A ~ A

A ~ ~ A

~0 ~ z ~ o ~d æ~

o ~ o ~ ~ " Cz~

2 ~ ~ ~ _ 3 ~

~ - .

8 ~ 3 wo 96/08538 PCTIUS9S/00124 4577-76 = 36.31% Adipic acid, 58.04% TTD Diamine, 4.16% Stearic acid & 1.49% Irganox 1098 (antioxidant).
4358-74 = 42.97% Adipic acid, 21.75% EDR 148, 33.81% J~;rr~ r D-230 & 1.47% Irganox 1098 (antioxidant).
4358-68 = 44.71% Adipic acid, 29.89% EDR 148, 23.93% Jt;rr~ -i"P D-230 & 1.47% Irganox 1098 (antioxidant).

While this invention may be embodied in many dirrel~ellL forms, there are described in detail herein specific plcrtll~d embo~limp-nts of the invention. This description is an exemplification of the principles of the invention and is not inten(1e~1 to limit the invention to the particular emborlimPnts illllstr~t?~l, W O 96/08538 ~ ~ PC~rrUS95/00124 What is cl~imP-d is as follows:
1. An illl~)lVVt;lll~ in the adhesive bonding method for a first substrate, which is an envelope portion, a stamp, a sticker, a pac~in~ tape or a label, in which said first substrate has a film of remoistenable adhesive applied thereto, said first5 substrate is stored for a period of time, after such time the~emoistenable adhesive is moistened, the substrate is joined to a second ~ub~ e and ~C~UlC is applied thereto until bonded, the improvement coll.plisillg tha~ the remoistenable adhesive is a hot melt Co~ of a thermoplastic polyamide~epared from an acid component selectç<l from the group consisting of adipic aci,d~,pimelic acid, azelaic acid, suberic 10 acid and sebacic acid, and an aLkyleneoxy fli7~n~ com~ol~e"l consi~ g of one or more tli~minP compounds having the formul~a.
H2N-CyH2y-(0C2~ -0-CyH2y-NH2 where y is 2 or 3 and x is 1-50.

15 2. A method as in claim 1 whe~l the remoistenable adhesive co~i~
essçnti~lly of the ~,~llll~lastic poyamide.

3. A method as in claim 1~herein the acid component consists es.s~nti~lly of adipic acid and stearic acid, ap the aL~yleneoxy .li~...i..P component has the 20 formula: /
H2N-(CH2)lr-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2.

4. A method as in c~ .im 1 wherein the acid component co"ll,lises adipic acid.

25 5. A method as i~, claim 4 wherein the alkyleneoxy ~ minr component has the formula:
H2~-(CH2)3-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2-6. A method ~!s in claim 5 wll.,lcin the acid colllponelll further cc""~lises a 30 monofilnrtic)n~l clrboxylic acid.

7. A metho~ as in claim 6 whelciul the monofunctional carboxylic acid is chosen from a group 7bl~i~ g of stearic acid and benzoic acid.

Claims (34)

-18-What is claimed is as follows:

1. An improvement in the adhesive bonding method for a first substrate, which is an envelope portion, a stamp, a sticker, a packaging tape or a label, in which said first substrate has a film of remoistenable adhesive applied thereto, said firstsubstrate is stored for a period of time, after such time the remoistenable adhesive is moistened, the substrate is joined to a second substrate and pressure is appliedthereto until bonded, the improvement comprising that the remoistenable adhesive is a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and an alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-CyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.

2. A method as in claim 1 wherein the remoistenable adhesive consists essentially of the thermoplastic polyamide.

3. A method as in claim 1 wherein the acid component consists essentially of adipic acid and stearic acid, and the alkyleneoxy diamine component has the formula:
H2N-(CH2)3-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2-

4. A method as in claim 1 wherein the acid component comprises adipic acid.

5. A method as in claim 4 Wherein the alkyleneoxy diamine component has the formula:
H2N-(CH2)3-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2-

6. A method as in claim 5 wherein the acid component further comprises a monofunctional carboxylic acid.

7. A method as in claim 6 wherein the monofunctional carboxylic acid is chosen from a group consisting of stearic acid and benzoic acid.

8. A method as in claim 4 wherein the alkyleneoxy diamine component has the formula H2N-CH2-CH2-(O-CH2-CH2)X-NH2 where X ranges from 2 to 3.

9. A method as in claim 8 wherein X is 2, and wherein the alkyleneoxy diamine component further comprises a compound having the formula NH2-CH-CH2-[O-CH2-CH]2-NH2 where Z ranges from 2 to 6.

10. A method as in claim 9 wherein the acid component further comprises sebacic acid.

11. A method as in claim 1 wherein the remoistenable adhesive further comprises at least one of a wax, an antioxidant and a tackifier.

12. A method as in claim 1 wherein the remoistenable adhesive further comprises at least two of a wax, an antioxidant and a tackifier.

13. A method as in claim 1 wherein the remoistenable adhesive further comprises a wax, an antioxidant and a tackifier.

14. A method as in claim 1 wherein said first substrate is the stamp.

15. A method as in claim 1 wherein said first substrate is the packaging tape.

16. A method as in claim 1 wherein said first substrate is the sticker or label.

17. An envelope, stamp, packaging tape, label or sticker having a film of remoistenable adhesive applied thereto, wherein the remoistenable adhesive comprises a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and a alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-CyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.

18. An envelope, stamp, packaging tape, label or sticker as in claim 17 wherein the remoistenable adhesive consists essentially of the thermoplastic polyamide.

19. An envelope, stamp, packaging tape, label or sticker as in claim 17 wherein the acid component consists essentially of adipic acid and stearic acid, and thealkyleneoxy diamine component has the formula:
H2N-(CH2)3-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2-

20. An envelope, stamp, packaging tape, label or sticker as in claim 17 wherein the acid component is adipic acid.

21. An envelope, stamp, packaging tape, label or sticker as in claim 20 wherein the alkyleneoxy diamine component has the formula H2N-(CH2)3-O-CH2-CH2-O-CH2-CH2-O-(CH2)3-NH2-

22. An envelope, stamp, packaging tape, label or sticker as in claim 21 wherein the thermoplastic polyamide further a monofunctional carboxylic acid.

23. An envelope, stamp, packaging tape, label or sticker as in claim 22 wherein the monofunctional carboxylic acid is chosen from a group consisting of stearic acid and benzoic acid.

24. An envelope, stamp, packaging tape, label or sticker as in claim 20 wherein.the alkyleneoxy diamine component has the formula H2N-CH2-CH2-(O-CH2-CH2)x-NH2 where X ranges from 2 to 3.

25. An envelope, stamp, packaging tape, label or sticker as in claim 24 wherein X is 2, and wherein the thermoplastic polyamide further comprises a compound having the formula NH2-CH-CH2-[O-CH2-CH]z-NH2 where Z ranges from 2 to 6.

26. An envelope, stamp, packaging tape, label or sticker as in claim 25 wherein the remoistenable adhesive further comprises sebacic acid.

27. An envelope, stamp, packaging tape, label or sticker as in claim 17 wherein the remoistenable adhesive further comprises at least one of a wax, an antioxidant and a tackifier.

28. An envelope, stamp packaging tape, label or sticker as in claim 17 wherein the remoistenable adhesive further comprises at least two of a wax, an antioxidant and a tackifier.

29. An envelope, stamp, packaging tape, label or sticker as in claim 17 wherein the remoistenable adhesive further comprises a wax, an antioxidant and a tackifier.

30. An envelope having a folding adhesively bondable closure flap, and having a film of remoistenable adhesive applied thereto, wherein the remoistenable adhesive comprises a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and a alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-CyH2y-OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.

31. A stamp having a film of remoistenable adhesive applied thereto, wherein theremoistenable adhesive comprises a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and a alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-cyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.

32. A packaging tape having a film of remoistenable adhesive applied thereto, wherein the remoistenable adhesive comprises a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and a alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-CyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.

33. A sticker or label having a film of remoistenable adhesive applied thereto, wherein the remoistenable adhesive comprises a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and a alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-CyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.

34. An improvement in the bonding method for closing an envelope in which an envelope, having a folding closure flap and having a film of remoistenable adhesive applied thereto, is stored for a period of time, after such time the remoistenable adhesive is moistened, and the flap is folded over onto the envelope and pressed against the envelope until bonded, the improvement comprising that the remoistenable adhesive is a hot melt consisting of a thermoplastic polyamide prepared from an acid component selected from the group consisting of adipic acid, pimelitic acid, azelaic acid and suberic acid, and an alkyleneoxy diamine component consisting of one or more diamine compounds having the formula:
H2N-CyH2y-(OC2H4)x-O-CyH2y-NH2 where y is 2 or 3 and x is 1-50, the remoistenable adhesive being further characterized in that it resists blocking at a humidity of 84% or more.