Note: Descriptions are shown in the official language in which they were submitted.
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A PRODUCTION TECHNIQUE FOR 8LOCKS OF HOT MELT ADHESIVES
This invention relates to a method for packaging hot melt adhesives compositions and to the
resulting packaged adhesive compositions.
Hot melt adhesives which are generally applied while in the molten or liquid state are solid at
room te",pe,dlure. Typically, these adhesives are provided in the form of blocks; however, because of
the nature of these n,dle(ials there are p,.~l-. "s asso~ ed with handling and packaging them. The
solid adhesive blocks not only stick or adhere to hands or mechan'~-' handling devices and to each
other, but they also pick up dirt and other contaminants. Additionally, certain a~r' ~ ' -ns require high
tack fommulations which result in blocks that will deform or cold flow unless suppo, led during shipment.
The need and advanldges for providing tackless or non-blocking hot melt adhesives are appar~:nt and
various ways of acco"lpl ~'ning this have been developed.
Japanese Patent 48-103635 published Dece",t,er 26, 1973, cl: ~vloses a granular adhesive which
is tacky at room tt:---pe-dture and coated or enveloped with a non-tacky hot ,.,o't~ ' 'o material that is the
same type or is miscible or mixable with it.
French Patent 2,544,654 published October 26, 1984, ~lisclQses forrning a ~d~,kless hot melt by
adding molten hot melt to a mold containing a preformed support layer having a transfer film thereon
which is co"",dl;ble with the hot melt.
U.S. Patent Nos. 4,748,796 issued June 12, 1988, and 4,755,245 issued July 5, 1988, disclose
fomming a protective coating for an adhesive material by ele~t,usldlically coating a mo!d or cavity with
a powder screen and then pouring hot melt into the mold.
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French Patent 2,601,616 published October 22, 1988, ~ oses forming blocks of hot melt
pressure sensitive adhesives by casting the pressure sensitive adhesive into molds plt:co~led by
spraying with a film of non self-sticking hot melt material thereby forming a fusible non-tacky veil around
the pressure sensitive block.
5In German Patent 22 48 046 the hot melt adhesive is squeeze-cut into pillow-shaped pieces;
the pieces 5''hsequently cooled and s-' ' qe~
Still other patents teach coating or wrapping the formed hot melt block with various types of
plastic films. Thus, German patents DE 31 38 222 and 32 34 065 disclose coating the circumference
of elongdled hot melt portions with a thin polyolefin film. German patent 36 25 358 to Hausdorf teaches
10wrapping the solid hot melt block in a thellllopl~lic, especially copolyamide film with a melting point of
120C to 150C, while EP app' ~ 'icn 0 469 564 and WO 94/01330, both to Rouyer et al. Ilis~loses
v"i~p: ,g the solidified hot melt in a plastic or biodegl_de ''- polymeric packaging material.
All the latter methods have provided some degree of improvement in the pack~g ng and handling
of hot melt adhesives however they have suffered by virtue of either the need to unwrap or otherwise
15u"pachdge the hot melt or, in the cases of coated hot melts which are added directly to the melting pots,
by virtue of the contamination resulting from the build up over time of large quantities of the pa-,hdyi"g
",d~e~;als in the melt pot and app"~ equipment.
In order to overcome the disadvallt~ges inherent in the methods of the prior art, U.S. Patent
5,401,455, issued March 28, 1995, d;,~,loses the finding that when the hot melt adhesive is poured in
20its molten state into a mold or cavity lined with plastic pa '~_ ,9 film and then allowed to solidify, the
adhesive is fused to some extent into the film, resulting in a non-blocking adhesive pachage which will
melt faster in the melt pot and will not cause a sub~ idl build-up of undesi-~' 'e plastic residue even
after extended periods of time.
Since the melting point of the plastic film should be compa,~' 'e to, and p~:r~rably lower than,
25the melting point of the hot melt adl ,esivc in order to provide for s~ ory melting in the melt pot which
does not have a source of agitation, it is necessary that the lined mold be in direct contact with a heat
21S~97
sink so as to remove excess heat from the film as quickly as possible and thereby prevent melting,
buming or charring of the plastic film wrap.
An improvement on that method is described in U.S. Patent 5,373,682, issued December 20,
1994. According to that e" b" ' ~e~l, the molten adhesive is directly pumped or poured into a cy; ~lical
plastic-tube, the cylindrical tube being in di-ect contact with the heat sin~ The resultant adhesive
pa~,hdge is thus provided in a readily handleable cartridge form which may be produced in a continuous
line ope,dlion and which a~ 'i'icnally plossesses all the ad~,a"t~ges ofthe easily p,uc s s ~'e non-blocking
adhesive package of the parent a~ n.
While the methods desc~ ed in the cope~ " ~9 ~r~ ~ 'iOl~ have proved useful for packaging and
re-melting of most hot melt adhesive formulations, there remain some:,, ' "- 15, for eAdlll, 'e for non-
pressure sensitive adhesives, where ~ FP'-l9 during storage and shipping is unnecess~-y. There are
also other eFF'ic "^ns where even sma~l amounts of unmelted film may create pr~bl? ,~s in the melt tank.
lt is ll,e,~ desirable in a limited number of ~"~ inns to provide hot melt adhesive po,li~ns in the
convenient size and shape produced by the p,~cesses of the copending ap~ n but without any
extemal pacl~ _ ,9 film.
Accor~ , to an aspect of the present invention, a process for the p~ ~ng of molten hot
melt a&esive in a film cavity is provided wherein the a&esive is filled into the cavity at a
lule above the m~ltir~ point of the film and ~.,.e~ the plastic film cavity is in direct
contact with a liquid or gaseous heat sink the ~prvv~melll which co~ .. ;~,s using.as the film,
a heat sealable film at least a portion of wllich is water soluble.
According to an embodiment of the invention the water soluble portion of the film
co~ .ses polyvinyl alcohol, modified starch or cellulose. Accol~ding to an embodiment of the
invention the entire surface of the film co..~l.. ;~; polyvinyl alcohol.
- Accol~ g to a~ ,l embodiment of the present invention the cavity cG.~ es a
cylindrical tube of the heat sealable film. In a pIc~;llcd embodiment molten hot melt a&esive
is filled into the cavity at a molten viscosity of l,OOO cps. to 200,000 cps.
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, .
We have now found that when a heat s- '-' 'o film, at least a portion of which is water soluble,
is utilized as the film, the molten adhesive can be effectively pa-,hdged using the procedures described
previously. The water soluble film or portion thereof will then be slowly d;ssolved in a water bath, after
which the resultant adhesive mass will be fully s.,''J'fied and may be packaged directly or may be
s~hsequently coated with anti-stick ",dlerial~ using III~UIods conventional in the art
The method of the present invention is ada~t ''e to the pac~ 9 of virtually any type of hot
melt adhesive co"lposiuon. As eAdll, 'es the method disclosed herein may be used to pachage hot melt
adhesives p~pal~d from polymers and copolymers of synthetic resins, rubbers, polyethylene,
poly~n~ pjlene, polyurethane, acrylics, vinyl acetate, ethylene vinyl acetate and polyvinyl alcohol. More
specific ~Adlll, 'S include hot melt adhesives pl~:pal~d from the r ":.~i.ly.
3a
2 1 ~ 7
a. rubber polymers such as block copolymers of monovinyl a,u",dtic hydrocarbons and
conjugateddiene,e.g.,styrene-butadiene, styrene-but-" ne-styrene, styrene-isoprene-styrene, styrene-
ethylene-butylene-styrene and styrene-ethylene propylene-styrene;
b. ethylene-vinyl acetate poly~,,ela~ other ethylene esters and copolymers, e.g., ethylene
5 ",etl,ac~ylate, ethylene n-butyl acrylate and ethylene acrylic acid;
c. polyolefins such as polyethylene and poly~,,u~,ylene;
d. polyvinyl acetate and random copolymers thereof;
e. polyacrylates;
f. polyamides;
9. polyesters;
h. polyvinyl alcohols and copolymers thereof;
i. polyurethanes;
j. polystyrenes;
k. polyepu~ides;
I. graft copoly",e,a of vinyl n,ono"~,(s) and polyalkylene ox'lde polymers; and
m. ''hydecontainingresinssuchasphenol-aldehyde,urea-aldehyde,IIIeICA~ c~'~ehyde
and the like.
Most often such adl,esives are formulated with tackifying resins in order to improve adhesion and
introduce tack into the adl.cs.-e. Such resin indude, among other ",dt~rials, (a) natural and ",~ d
20 resins, (b) polyterpene resins, (c) phen~ ",o lified hyd~uca~l on resins, (d) coumarone-indene resins,
(e) aliphatic and 'dl~llldtiC p~t,.' ~ ~n l"rd~-)cd,bon resins, (f) phthdldtt: esters and (g) hyd~gendled
hydlu~,d,l,ons, I.~d~ugendled rosins and hydlugel,dled rosin esters.
Desi, ''- opffonal iny,~ r,ts include diluents, e.g., liquid polybutene orpolypropylene, pet,-' ~urn
waxes such as paraffn and microcrystalline waxes, polyethylene greases, I"rd,ugend~ed animal, fish and
25 vegetable fats, mineral oil and synthetic waxes as well as hyd,ucd,~on oils such as napl~U, ~n~ or
pd,drri".~ mineral oils.
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Other optional additives may include stabilizers alllioxiddlll:~ co!ard"l:, and fillers. The selection
of components and amounts as well as the prepa,dlion thereof are well known in the art and described
in the literature.
The heat s,e- - e water soluble film into which the molten adhesive is poured may be any film
which will ~ , its integrity during filling but will suhsequently dissolve in water. Suitable materials
include polyvinyl alcohol n,odi~ied sld~d~es cellulose films and the like. Polyvinyl alcohol hlms are the
most preferred Rather than using the water soluble material as the entire hlm substrate in accordance
with an alternative embodiment of the invention it is p~s- 'E that the film include a non-water soluble
portion with the water soluble portion serving only as the vehicle to effect dissolution and separdtion of
the film from the adhesive mass during the water cooling. In the case of hlms which comprise more than
one material it is only necessary that the portion of the film which will provide the longitudinal lapped
seal around the adhesive mass during the filling ope,dtion be heat see
It may also be desi, e in the case of pressure sensitive adhesives to use a co",posite water
soluble film la" Idted to a non-soluble coating the latter remaining on the adhesive mass and providing
a cori",dtil)le tackless coating after d . ~ ution of the water soluble film. For eAdlllr ~ pressure sensitive
masses may be so pachaged by using a lamination of an ethylene vinyl acetate coating on the polyvinyl
alcohol film.
The tl, k.,ess of the film utilked generally varies between about 0.1 mil to 5 mil pl~ldbly 0.5
mil to 4 mil. The tl, k.,ess of the particular film also varies depending upon the te",perdlure at which
the molten adhesive is pumped or poured into the plastic film cylinder. The particular viscosity at which
the adl,e:,;ve can be introduced into the plastic film cylinder will vary depen~ ,9 on a variety of factors
induding the pumping capacity of the pump the strength of then plastic film and the like. Visco~i~ies in
the range of 1 000 to 200 000 cps pr~f~.dbly 2 000 to 100 000 may be utilized. I IuJ elcr we have
found that the most p,t:fer~ed viscosity of the adhesive which is to be pa l~aged in accordance with the
invention is b~tv een 10 000 and 50 000 cps. It will be l~coylli~ed that the l~",pe,dture at which an
adhesive ~r"pos;tion will exhibit this viscosity range will vary from one adhesive to another. In the case
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of adhesives which obtain their viscosity within the tenlpe,dlure range of 110 to 130C, film thicknesses
of about 1.25 mil are preferred; while for adhesives which exhibit this viscosity at temperatures of 130
to 150C, films of about 1.5 mil are plt:f~ d.
The heat sink may colllplise any means which will effectively and rapidly remove o~ absorb the
5 excess heat from the entire surface of the film which is in contad with the molten hot melt adhesive
colll~.osition so as to prevent the lelll~eldlure of the film from exceeding its melting point even though
the molten hot melt adhesive temperature is higher than the film melting temperature. Suitable heat
sinks are provided by spraying the surface of the cylindrical plastic tube with cooled water or other
~rligel~lll means such as chilled glycol, liquid or g~seous nitrogen, colllpl~:ssed carbon dioxide or the
like. The spraying may be accomr' hed, for exdr,l, 'e, using a series of spray nozzles aimed at the
mandrel or a water or cooling ring or series of rings may be positioned around the mandrel so as to
provide a curtain or ca~cade of water or r~:rliger~lll around the entire circumference of the cylinder.
As ~liscussed above, the molten adhesive is generally poured or pumped into the film cylinder
at a tel I Ipera~ure at which the molten adhesive exhibits a viscosity of 1,000 to 200,000, pr~re, ~tly 10,000
to 50,000 cps. This lellq~er~lure will generally vary from about 110 to about 150C depending upon the
particular adllesive. Since the adhesive is pumped or poured continuously through the mandrel into the
film cylinder, it is possible to void and then cut the continuous filled tube into individual callridges at
virtually any desired length. In general, the individual cal ll idges are produced in a variety of sizes ranging
from about three inches to 18 inches in length and varying in weight, depending upon length, from about
20 0.5 to five pounds.
After filling, the adhesive cdll~idges, either individually orin a connected series, are further cooled
in a water bath to ambient t~lllpelal-Jre so as to dissolve the film and solidify the adhesive. Depending
upon the water soluble material used in the film, the film may begin to sepdldt~ from the adhesive and
dissolve within about fifteen minutes after being placed in the water bath in which case any residual film
25 remaining after cooling can be removed by placing the adhesive cdlllidge in water of about 60C prior
to bulk packaging. Some films may not be soluble in the cold water bath and, in such cases, when
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removal of the plastic film is desired the s ' ~ ed packages are submerged in room temperature of
slightly heated water until ~iss~ tion of the film occurs. In either case any residual amounts of film
which remain may be readîly removed by passing the pa._hdges through a series of rotating brushes or
using other scrubbing me.;l,ani;",ls. In the e",bodil"enl wherein the film co",prises a non-water soluble
5 component the It:fll_ ,9 film may be readily removed from the chilled water bath and may if desired
be recycled. This emba 'i ~e~l has the additional advantage in that less of the water soluble polymer
is present in the water bath thus pr~!an~' ,g the useful life thereof and producing less dissolved matter
in the water when it is d:~rosed of. The pa- l~ges are then dried either under ambient condilions or
using hot air knives or the like.
In the case of non-pressure sensitive adhesives the resultant ii~dividually packaged hot melt
adhesive cd,llidges can be stored handled and used directly. In the case of pressure sensitive
adhesives the s 'i~'i'ied adhesive ca,llidge may be treated with an anti-stick agent such for eAc",l~'e
as by dipping or spraying with molten wax or other non-tacky cor"pdlible coating.
The resultant hot melt adhesive ~,l,idge may be pa._kaged in a conbiner to reduce its exposure
15 to the env;.on",enl moisture or other contaminants. The container or other v~"~pp ,gs would then be
removed by conventional procedures prior to utilkation of the hot melt adhesive.
A prer~"ed e",L~ ' "ent of the method of the invention described herein is illustrated in Figure
1. In the Figure the water soluble film (1) is passed through a series of idler rollers (2) which smoothes
the film and controls the tension across the web. The film is then ll"~aded into a film folder (3) which
20 folds the film and forms a lap seal around a one to four inch d;d",~ler fill pipe or mandrel (4). The lap
seal is sealed with hot air (5) induction sealing or ultrasonic welding and then may be further sprayed
with cooling air to set the seal.
After the seal has set the tubular film is carried along the exterior of the fill pipe p~rerdbly using
a series of spreader rings (6) film guide(s) (7) and drive wheels (8) until it reaches the end of the fill
25 pipe at which point the molten hot melt adhesive pumped from a remote holding container through the
mandrel enters the cylindrical tube (9). If desired in order to maintain the desired molten viscosity the
2151~97
.
hll pipe may be insulated or jacketed as with double walls and filled with inlet and outlet ports (10)
through which heated water, steam or mixtures thereof may be circulated, so as to prevent premature
cooling of the molten adhesive in the mandrel and melting of the plastic film on the mandrel. The double
wall construction also ~ s con~r'~' ~ deaning and purging of the mandrel after the filling operation
is completed.
During filling, the tubular package is in contact with cooling water (11) or other refrigerant
medium. This water contact may be acco,l, ' hed using a series of water 3ets positioned around the
circumference of the cylind-ical tube. Altematively, a water or cooling ring (12) or series of water or
cooling rings may be positioned around the mandrel. It will be recognized that while the term
"spraying with coolant" is utilked herein, the invention also cort~"lpldles carrying out the entire filling
opeldlion in a cooled env;.onllælll as in the pl~:sence of liquid nitrogen.
Suhsequently, the adhesive filled tube is passed through voider rolls (13) which crimp or pinch
the continuous filled cylinder into smaller cd,(,idge sked seyllæn(s and which are set so as to assure
the proper Cdl Uidge length. Spraying with coolant is continued through additional spray nozles (14) until
the pa-,hage is sufficiently cooled so that the pa~ ged adhesive forms a self-seal formed at the voided
porbons. The cdlt,idge pa~ ges may then be cut at the voided area using conventional means, e.g.,
"e.,han - ' scissor (15), laser cutter, water jet or a heated knife or wire and subsequently cooled to room
telllpe.d(ure in a water bath. Altematively, the voided but uncut call,idge segments, still attached in
serial form may be cooled and cut Uleredrl~r.
As cliscussed above, the film may be dissolved in the cooling water bath itself or may be
subsequently dissolved in a sepaldle water bath prior to final pa-,h~ 9.
~ 215~497
` While the invention has been specifically described with respect to the continuous hlling of
adhesive cartridges claimed in U.S.-ar~ n Serial No. 07/993,890, it is equally adapt ''e to the
method described in pending f~rP'~ n Serial No. 07/883,994, wherein a mold, preferably a mesh
screen mold, is lined with the water soluble film and the molten adhesive poured therein all the while
,l ,la;" ,9 the mold in contact with a heat sink.
In accordance with the latter embodiment, the mold into which the the""oplaalic film is placed
and into which the molten adhesive is to be poured may comprise any rigid, self-supporting material
The molds are generally forrned from rigid plastic, e.g., acrylonitrile/butadiene/styrene polymers or
polypropylene orfrom metallic s(Jbslldles. Since it is desirable to keep the film in direct contact with the
water bath after filling, the use of pe,tu,dled or otherwise apertured molds is desired. A particularly
preferred mold is formed from steel mesh. The size of the mold varies according to the size of the
desired hot melt adhesive block. In general each mold is app,uxi",dl~ly 3" x 3" x 11" in di",ension and
often a series of molds are formed from one contiguous plastic m -'lulosic or metal sheet.
Fur~er details of the pl~,f~l~d çmbotlimP.nt~ of the invention are ;llustrated in the
follo~nng F,Y~mples. The Exarnples are p~so~ d for the ~ ose of illusl~ation of the invention
and are not intPn-lP, i to be l;...;l;~ of the invention as defined in the appended claims.
EXAMPLE 1
A conve~ltiohal pressure sensitilc hot melt adhesive co",position suitable for dispcs.''e
ar F ' - 'i~ ns was p~ ~:pared using a ta ,hilied and pl ~ ; ed blend of ethylene vinyl acetate copobmer and
wax.
A continuous supported cylindrical tube was formed by vnat~,~ ,g a plastic film co~prising a 1.2
mil p olyvinyl alcohol film around a 1.5 inch d;d",t:ler insulated mandrel or fill pipe. After the lap seam was
formed, it was sealed using hot air and then set by spraying with ambient l~llq)eldlure air.
The molten hot melt adhesive, at a viscosity of 10,û00-15,000 cps. (120-130C) was pumped
therein through a nozle while the entire surface of the film was sprayed with chilled water (5-1 0C). The
filled tubes were voided at lengths of 6 inches and then cut to form individual cartridges. The resultant
ca,l,idges were allowed to cool in a chilled water bath until they had co"., '~t ~y s 3 '~e~l
The resultant cd,l-idges were lldllat~ d to a hot water bath (about 65C.) where the film was
dii,solved and the blocks then removed, dried and packed in dp~JIuplidle shipping co"l~ 1e,a.
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.,
EXAMPLE 2
The procedure of Example 1 was repeated to package a pressure sensitive hot melt adhesive
composition suitable for can/bottle labelling app'i~ ns.
After transfer to the hot water bath, the film was d;ssolved, the adhesive removed, dried and then
5 passed to a tank COIlbdi~ 9 a molten COlllr ~ !e wax material. The block was dipped into the tank, the
surplus material allowed to run off, dried and packed to the shipping container. The outer coating thus
fommed a non-tacky wax coating co"lF "' !e with the adhesive.
EXAMPLE 3
The procedure of Example I may also be repeated using film which consi~ts of low density
10 polyethylene film with a strip of polyvinyl alcohol film adhered to one side wherein the polyvinyl alcohol
strip co",prises about 20% of the surface area of the film. After, ~;~ sn'ution of the polyvinyl alcohol
portion of the film, the remaining low density polyethylene may be readily peeled off the caill idge.
Testing of the resultant ca,l,i~ges indicates that the adhesive properties of the adhesive blocks
are ~"drr~l~d by the filling and pac~ "9 process. Similar results would also be obtained when
15 packaging other hot melt adhesive forrnulations.
Although prGrG~ d embo~ x of the invention have been described herein, it w~ll be
lm-l.orstood by those skilled in the art that variations, modifications, and equ;valents may be made
thereto wi~ ul departing from the sp~r~t of the invention or the scope of the appended claims.
