CA1316143C - Container closure having improved liner - Google Patents

Abstract

Abstract of the Disclosure A bottle crown cap particularly for beer bottles, comprising a metal shell and a liner of thermoplastic polyurethane. The liner material is completely reacted, then applied directly to the shell by a hot melt process.

Description

~ 3 ~ 3 Baokground of the Invention ,, ~
Thi~ invention relate~ to cont~iner clo~ure~. It h~
partlculnr applica~ion to crown oap~ or bottle~,~ mo~t e~peci~lly to beQr bottle crown~.
A beer conta~ner o~ p~cXage mus~ prot~t the fl~vor of the beer duri"~ tran~poxt ~nd a~orage o~ ~h~ beer. It mu~t exclude all oxygen. It mu~t not oontain any mate~ial~ which CAn be extractad by the beer,~ and ~onv~r~ely it muRt not ~aavenge the ~lavor~nt~ n~turally oaouxring in the beer~ Altho~gh bottled beer h~s popularLy been re~rded a~ well protected~ ~r~w~r~ have long known ~hat bot~le crown~ have not provided altoqether adequate pro~ectiOn of ~h~ ~eer. The proble~ has been found ~o be largely in tho plastic crown liner. A d~us~ion of the proble~s a~ociat~d with polymerle pack~gin~ material~ ( inaluding c~own line~s) in th~ beer induRtry i8 co~tained ln a pap~r entitled "Packaglng M~terial~ and Bee~ Qua~ity" by ~r.,W.A.
Ha~dw~ok, Jr., appe~rln~ a~ chapter 23 in ~r Pac~aginy: A
Manual ~o~ the 8r~wing an~ BeVe~ge Indu~tri~, edited by Harold M. Broderick (Madi~on, Wiscon~ln.l 1982).
The mo~ co~on crow~ liner ma~erl~ polyvlnyl chlorlde (PVC), containing d1octylphthal~te ~ a pla~ticizer, an~
a calcium or zlnc ste~rat~ ant~oxldan~, ~hi~ ~aterial ~ven~e~
30me of th~ ~lavor-giving e~ters ln beo~ and fre~uently contain~
ex~r~ctable impurities.

3~

~ 3 ~

The PVC llner i8 applied elthe~ ~8 ~ creamy pla~ti~ol and spr~ad by ~p~nnlng o ~olding,l or el~e by melting a powde~ed plasti~ol in ~n extruder ~nd extruding the ~olten materl~1 into the crown sh~ll, In the latter p~oaeRs,l a ~ampin~ tool may be UBed to fo~m t~e liner. The llner ~ ~o~etime~ applied ~ a die-cut ~ilm and melted to the crown ~h~ll in eitu. In any o~
these proceq~es, it 1~ important to control tha temperature care~ully to drive off all volat~le material~ without damag~ng the crow~ ~hell or the polymer. The crown liner i~ om~time~
foAmed to give lt more re~ilience,~ but both ~he ioamln~ ayen~ a~d the inc~eased urf ace area of the linar in~re~se the likelihood that the liner will a~ect the flavor of the ba0r.
Oth~r crown llner~ h~ve b~en u3e~ or proposed, but all have ~ r proble~, FoY example, polyethyl~ne And ~thylene vinyl ace~ate liner~ have an even ~reate~ e~ect than PVC, by -~cavengin~ vor co~pone~t~ from the beer. In U.S. Patent 3,799,380 to Ha~him~to et al, a bo~tle crown llner iB formed by reaoting,l in th~ crown ~hell,~ a polyol and an Aromatic i~ocyanate to ~or~ a ~hermo~et po~yureth~ne. This approach require~ new equip~ent to replac~ th~ 6tandard PVC llne~ and re~u~res that the bottle crown manufa~turer maintain the highe~ manufacturing ~tand~r~ to a~sure complete reactlon of the monomer~ ~nd co~plste ~e~ov~l of Bolvent~ and ~taly~t~. Even wh~n t~e proce~ carried out ~ith ~tmost care,l ~he proce~ senerally ~ 3 ~

require~ the u~ oE an exce~3 of toxic i~ocyanate~v whi~h are rea~ted after the main po~ymer1za~i~n ~eaotion hs~ been coupleted. Moreover, a ~ub~a~tial curlng period i~ r~quired, pref~r~bly at elevated te~p~rature. T~e r~s~lting t~moset polyurethane l~ner m~y h~ve physloal and c~Qmlcal p~operti~
lJ~ ~;
wh~ch are not altogether ~eairable. An e~rl~er~patent to Mahoney, ~o. 3,~42,411, diaclo~e~ a ~i~ilar approach, with a foamed polyureth~ne.
Summa~y of the Inventio~
One of the ob~ects o~ this lnventlon 1~ to prov~d~ a bottl~ crown which proviAes b~tter ~lavor prot~ction than crown~
known heretofor~, pa~ticula~ly when use~ on beer bot~les, Anothe~ objeat i8 to provide ~uch a crown whose liner lacks extract~bLe addltlves and doe~ not ~caven~e ~lavor compone~ts ~rDm beer, Another ob~ct 18 to provide ~uch a crown which m~y be manu~ctured us1ng exiutin~ equipment;~ ~ncl~ding extrud~rs.
A~other ob~ect iB to provide ~uch ~ crown wh~ch i~
e~ler to a~emble and ha~ bro~der manuf~c~uring para~stex~, including liner mold~ng temper~ture~.
A~oth~r ob~ect iu ~o provid~ ~uch a orown who e llner ha~ ~ high degree of memory. and therefv~e maintai~ a ~eal ~ven after it ha~ be~n compre~ed for long p~rlod~.
Another ob~ct i3 to provlde ~uch ~ crown who~e li~r is highly adh~ive to the crown sh~ll.

1 3~

Other ob~e~t~ ~ill o~aur to tho~e ~kllled in th~ ar~ in ligh~ of the following ~e~ription and a~com~anying dr~wlng~.
In ac~ordance with one a~pect vf thls invention, ge~er~ ated, a con~iner clo~lure 1~ provided whlch lnclu~e~
a ~hell ~nd ~ liner, the liner being ~ormed of ther~opl~ti~
polyurethane eLa~to~er. ~he polyurethane~ which are u~e~ul ln the pra~en~ ~nYantion mu~t be thermopla~ic ~a~her ~han thermosetting, but thelr exaat chemlcal co~po~ition h~ not been ~ound to be critical ~o thelr u~efulne~e in the lnventi~n.
~ he clo3ure ~hell i8 made of a material which provid~
the required strength to hold the closure ~o the contalner, and i8 pr~exably made of ~et~l. In ~h~ pr~erred e~odimen~, the cl08ure iB a bo~tle crown ~p, most pre~erably ~or A beer bottle.
The ~he~mopla~tic polyurethane elastomer iB applled to the bottle ~rown ~hell a~ a co~pletely reacted poly~er~

conta1ning neither pla~ticizer nor non-reacted mono~er~. The ther~opla3tic polyuret?lane~ have a wide ran~e of hardness, and do not change that hardne~s app~ci~bly ove~ a wids temperature range. They have good low ~emperature ~l~xibility. high abra~ion re~ ance, good ela~ticity~ snd good memory propert~e~ caus~
these ou~andlng qu~7ltie~ ~re bu11t into the b~ckbone of ~h~
pDlym~r, and are no~ produced by additiv~, they r~ain ~t~ble when the liner ii expos~d to ~eer or oth~r conte~t~ o~ the ~ontainer. ~he ther~Qpl~tlc Rolyur~than~s ~re meltabl~ without a~fecting thei~ chemio~l prope~ti~, and the mol~en polymer i~
ea~ily ~olded. I ha~e ~oun~ th~t the mater1a~ ~ function well in all resp~ts a~ crown liners, ~itho~t r~uirln~ the addition of plastlcizers, ~o:Etsning a~ent3 or ~ntioxidant~.

~ 3 ~

Many of the propertia~ o~ thermopla~tic polyurethan~
ar~ well known ~nd are a~t o~t, ~or example, in the K~rX~O~h~sr Encyclope~a o~ Chemlcal Ta~nology, Thtrd Editlon, parti~ularly at volu~e 8, page~ 6~-40, e~pecially page~ 632-35, volu~e 10, page~ 216-24~, e~pealally page ~32, and volume 23, page3 ~76-608, The use o~ thermopla~tl~ polyurethane ela~tomer~ a~
liners for beer bottle crown cap~ f~lls a long-~elt n~ed ln the beer lndu~try. Pro~bly bec~uue o the p~rceived danger in u~lng a material baq~d o~ l~ocyannte~ ar~d because Of the di~f iculties atten~an~ upon th~ previou~ly proposed thermvset polyurethaneq, ~he ~e of ther~oplastic polyurethanas ~8 clo~ur~ liners h~s not been heretofore prop~sed. Nonetheless, the thermopla~tic polyuretha~e ela~to~erq axe fully rea~ted and cur~d before ~eing formed l~to pellet~ of flakes7 and are thereoYe inert. Any slight t~a~e of free isocy~n~te which mlght happen to be in ~he ~a~erl~ls i~ driven off w~en the ~ateri~lQ are he~ted and extrud~d. The ~hor~opl~ti~ poly~rethanes h~v~ been found to produce no ~h~ng~ in the fl~vor of beer ~tore~ ln bot~les closed with the bo~tle ~rown of the invention, elther by ext~actton of ~aterial3 ~rom the polymer~ or by absorp~ion of flavorant~ ~rom the b~er. Be~u~e the ther~opla3ti~ polyureth~ne ~evelop~ a memory when it i~ melted and cooled, it tend~ to ret~i~ lt~ shape and return~ to 1~, even ~fter ~elng compre~ed. It ther~fo~e has ~upertor ~e~ling capab~ltty. ~he thermopla~tic polyurethAne is known for it~ adh~sive qu~l~ti~, and adhere~ ten~iously to the metal crown ~hell, ~ut the coolsd poly~r ~oe~ n~t stlck to the glas~ bottle.

~ 3 ~ 3 Pre~rably, ~he polyurethane line~ h~ a h~rdne~ o~ the order of Shore 60A ~o 7SD, mo~t prefer~bly in the range of 6~A to lOOA. The polyureth~ne ~hould nb~ be t~cky ~t nor~al ~emperatures (under 100 ~,). For convenience in Porming th~
liner, it should have a m~lting po1nt below abvut 450~F ~3$~C), sOth polye~her a"d polye~ter polyurethane~ are uaeful~ an4 blendu of the~e ~ypa~ ~re par~icularly de~rable to impart the high degres of ~ydrolytlc ~tabllity of the polyether polyurethane ~nd tho ga~ imper~eAbility o~ ~he polye~ter polyurethane.
EitheY ~romatic or aliphatl~ polyur~thane~ ~8y be utili2ed a~ the llner.
~ n the method o~ th~ invention, a completaly reacted th~rmopla~tic polyureth~ne 19 ~elted and appllea to the ln~ld~ o~
a bot~le crown ~hell to form a liner~ Ths polyurethan~ i~
cooled. T~ cap i~ then ~ppll~d to a ~ontal~e~. The container iB prefer~bly a beer bottle, but the inv~ntion ~ay ~l~o be ~ed with other container~ ~illed with other ~aterl~ or ~x~mple other bevera~a~ ~u~h aB carbona~od 80~t drinX~ or wine.
Pr~f~rably~ the thermopl~ polyurethane liner 1 applied as ~ ~llm, and iB no~ ~oa~d or blown in any way.
Other aspects of the inventlon will be better ~nd~r~tood in v~ew of the ollowing de~cription o~ the preferred e~bodiment and th~ appended ~laim~
Brief D~s~lp~Lon o~ th~ D~awin~
~ n t~e dr~wings, F~¢UR~ 1 i8 ~ View in C~O~B s~ction of a bottle crown cap having a the moplastic p~lyuret~ne llner in ao~ord~nce with the present inventio~.
FIG~E 2 i~ a pl~n view of the crown cap of ~IGURE lo ~ 13 ~

~ 3 ~
FIGURE 3 is a view in cross section of the crown cap of ~IGURES 1 and 2 applied to a bottle, Description of the Preferred Embodiment Referring to the drawings, reference numeral 1 indicates a bottle crown cap in accordance with the present invention. The crown 1 includes a shell 3, made of steel, and a liner 5 made of a thermoplastic polyurethane elastomer. An example of a suitable polyurethane is a commercially available material sold under the trademark ~-THANE PN-03 by K.J. Quinn & Co,., Inc. o~ Malden, Massachusetts, This material is a thermoplastic aliphatic polyurethane and is described in a brochure published by K.J.
Quinn & Co. entitled "Introduction and General Information to Q-THANE Thermoplastic Polyurethane Resins."
Other preferred thermoplastic polyurethane resins include a variety of extrusion grade thermoplastic polyurethane elastomers. Q-THANE resins, such as Q-THANE
P-455, all sold by K.J. Quinn ~ Co., may be used. Extrusion grade resins sold under the name Pellethane* by the Upjohn ~0 Company are described in Upjohn's "Pellethane* Processing Guide" and in "DSG Reports" 16, 17 and 20. Examples of these resins are Pellethane* 2102-80AE and Pellethane* 2103-80PF.
Extrusion grade resins sold under the name LIBE~AN* by Nippon Elastollan Industries Ltd., Tokyo, Japan may also he used.
These polymers are described in a brochure entitled "Thermoplastic Polyurethane LIBERAN." Examples of suitable materials are LIBERAN E-380 and E-390. These products, as a group, cover a wide range of chemical compositions and a range of hardnesses from Shore 60A to 75D. The extrusion grade * Trade Marks materials have a hardness of from Shore 60 A to 100A. Aromatic and aliphatic polyurethanes, of both the polyester and polyether types, are included.

A steel bottle crown shell 3 is cleaned and degreased i n accordance with good manufacturing practice. The shell B is placed at the outlet of an extruder to which is added Q-THANE
PN-03 in flake form. The flake material is dried in accordance with good manufacturing practice. The extruder has a barrel temperature of 390°-410°F (200°-210°C), sufficient to melt the thermoplastic polyurethane polymer. The melted polymer is applied as a ring to the inside of the shell to a thickness of about 10 mils, to form a a liner 5. The polymer is allowed to cool to room temperature. The cap 1 is then placed on a filler beer bottle. Maximum strength is obtained if the cap is maintained at about 110°C for ten hours prior to cooling. This period of elevated heat is not, however, essential to proper functioning of the cap 1.

A thin sheet of Q-THANE PN-03 thermoplastic polyurethane is extruded as in the preceding example. A 3/4 inch square of the materials placed in a beer bottle, and the bottle is filled on conventional filling equipment, crowned, and pasteurized. The bottles were stored for two weeks at 85°F., then cooled and opened. A panel of tasters could detect no flavor change. The square of material was analyzed and found to have extracted no significant flavorants from the beer. By way of comparison, the best previously known crown liner material also produced no aeteotable ~lavor c~ange and e~racted no significant flavorant~
from the beec. ~he amoun~ o~ ~1AVOrant~ ex~acted ~y the thermopla~ic polyurethane, however, was half th~t ~x~rac~ed by the prior art m~te~
The bottle o~ ~x~mple 1 showed excellen~ oh~ac~eri~tic~
in standard ~tack test ~nd leak te~ts.
~ umerous vari~tion~ in the co~tainer ~10BULe and method of the pre~ent invention, within the ~cope o~ the appended cLaim~, will OCCUL to tho~e skil~ed in the art in light o~ the ~oregoing di~¢los~re. ~erely by way of ex~ple, tne ~hell 3 ~y be made of other me~als or of other mate~ial~ s~oh as ridgid pla~tio~ which have the req~i~ed strength ohaxao~ri~tics. The thermoplastic polyurethane ~ay be applied by di~er~nt me~-hod~.
The e v~riations a~e merely illustrative.

Claims (20)

1. A bottle crown comprising a shell and a liner, the liner being formed of completely reacted thermoplastic polyurethane elastomer having a Shore hardness of from about 60A to about 100A.

2. The closure of claim 1 wherein the polyurethane elastomer is an extrusion grade polyurethane.

3. The closure of claim 1 wherein the polyurethane elastomer comprises a polyether polyurethane.

4. The closure of claim 3 wherein the polyurethane elastomer consists essentially of a polyether polyurethane.

5. The closure of claim 3 wherein the polyurethane elastomer comprises a blend of a polyester polyurethane and a polyether polyurethane.

6. The closure of claim 1 wherein the polyurethane elastomer comprises a polyester polyurethane.

7. In a beer bottle filled with beer and closed with a bottle crown comprising a shell and a liner, the improvement wherein the liner is formed of a completely reacted thermoplastic polyurethane elastomer.

8. The beer bottle of claim 7 wherein the liner has a Shore hardness of from about 60A to about 100A.

9. The beer bottle of claim 8 wherein the polyurethane elastomer is an extrusion grade polyurethane.

10. The beer bottle of claim 8 wherein the polyurethane elastomer comprises a polyether polyurethane.

11. The beer bottle of claim 8 wherein the polyurethane elastomer comprises a polyester polyurethane.

12. The beer bottle of claim 8 wherein the polyurethane elastomer comprises an aliphatic polyurethane.

13 13. The method of making a container closure comprising melting a completely reacted thermoplastic polyurethane, applying the melted polyurethane to the inside of a closure shell to form a liner, and thereafter cooling the polyurethane.

14. The method of claim 13 wherein the container closure is a bottle crown and including a further step of applying the crown to a bottle.

15. The method of claim 14 wherein the bottle is filled with a carbonated beverage.

16. The method of claim 15 wherein the beverage is beer.

17. The method of claim 14 wherein the bottle is filed with an alcoholic beverage.

18. The method of claim 13 wherein the thermoplastic polyurethane is an extrusion grade polyurethane, and wherein the step of melting the polyurethane includes placing the polyurethane in an extruder.

19. A method of sealing a beer bottle without influencing the flavor of beer contained within the bottle, said method comprising melting a completely reacted thermoplastic polyurethane, applying the melted fully reacted polyurethane to the inside of a bottle crown shell to form a liner, thereafter cooling the polyurethane, thereafter filling the bottle with beer, and thereafter applying the crown to the bottle to seal the beer in the bottle.

20. The method of claim 19 wherein the fully reacted polyurethane is a polyester polyurethane having a Shore hardness of from 60A to 100A.