CA2033494A1 - Preform for hot fill pressure container - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

This relates to the packaging of a hot liquid product in a container having little resistance to internal vacuum wherein immediately after the container has been filled, the container is internally pressurized and closed. This particularly relates to an injection molded preform formed of a suitable polyester resin which is of a configuration related to an intended blow mold cavity whereby the desired biaxial orientation is obtained in the various portions of the resultant container and the wall thickness of the container base is increased so as to prevent undue stress enlargement and creep at high internal pressurization. Internal pressurization on the order of 40-45 psig is envisioned.

Description

20~349~

PREFORM FOR I~OT FILL PRESSURE CONTAINE~

rhi~ lnv~ntlon specifically relates to contdlncr~ whlch are filled with a hot liquid product and thereafter lnternally pressurized to a llmited dugree ~o a~ to prevent a vacuum being formed within th~ cont~ln~r wlth a rcsultant container deformatlon.
Mo~t partlcularly thls invention relates to a modified preform for formlng such a required container wherein the ba~e of the contalner is of greater thickness than usual and wherein the container base when heated by the hot liquld product and subject to internal pr~s~urlzation wlll have a minilllum stress deformation and creep.
This invention particularly relates to an l~n~rov~m~nt over the lnvention specifically set forth ln d colr~only a~slgned co-pendlng application of Wayne N. Collette et al entitled PET IIOT FILL PRESSURE
CONTAIN~ , U.S. Application Serial NoO 306,395, filed February 6, 19~9 and now . In USSN 306 395 it is dl~closed that a conventional stretch blow molded col~taln~r formed of P~T and llke polyesters need not be 8peclally heat treated and need not have reinforcing panel~ ln order to to be comJnercially fllled with a hot llquld yroduct. Thls ls accomplished by adding to th~ contalller lmol~dlately dfter ~illlng with the hot ll~u1d product llquld nitrogcn followed by immediate c1O~1ng of the container alld wherein the liquid nltrogen b~colnes nitrogen gas and internally ~re~surlzu~ the container to yrevent a vacuum collapse -` 2~3349~
-- L --~l~ur;-~o~ . , ~ 1~ dccor~d~lce ~1~1) t.ll~ dlsclo~ure of U~SN
3U~,~Y5, L~u loltl~l ~Jru~uru 1~ on tlle or~er of 30 p~ly. rl~ r~uru, in Illost: lilstallces, ls zu~tlcl~tlC tor ~dln~lllln~J Lilu contailler internally pr~ur~u~ tllu llot ll~jul~ ~ro~uct flll cools to r~o~ tu~pur~ture. Ilow~vu~r, the lnternal ~r~url~dLlol~ ls vury low.
lt ~a~ b~un found tllat lnstead of the rulatlv~ly low lnltldl interndl ~ressure of 30 pslg, a ~oru ~lr~lu lnltlal lAt~rnal pressurization would be ol~ th~ or~ur o~ 40-45 ~19. Ilowever, known c~Y~I~tlo~ co~talnur~ lntell~ud for rucelvln~ liqulds ul~ur 1~ lnturn~l ~r~urlz~tlon woul~ have the bases thuruo~ su~uct to too Inucll ~truss alld crecp whereln a r~ult~nt hudd ~l~dCU would not be comlllerc1ally ~cc~$~t~ . Accordln-Jly, ln accorddnce wlth thls lllvuntlol~ t~ru 1~ ~rovl~u~ d ncw ~reforlll for forminq a prloc c~l~ urdtlorl conta111er but whcre1n tlle base of ~uch cont~lnur 1~ thlckura~ o ~
~ ltt~ thu ~bovu ~nd oLIIur ~bJucts ln vi~w that wlll h~r~lndftur ~ypudr, ttlU ndtur~ of the lnventlon su clu~rly ulld~r~tood ~y r~lerence to the tollo~ J d~tdll~d du~crlption, t~e appended cla1ms, and th~ suvur~l vl~ws llluutrdted ln the accompany1ng 9 ~ .
d co~ o~lte ucl~elilatlc vertical ~ctlon~l viuv taken through a ~reform formed in accord~llc~ ~lth thls lnvent1on and shows how the pruform 1~ ~tr~tch blo~ Inolded to match the confl~uratlon of an uxl~tln~ Inold cdvlty to form a ~tl~acto~y contaln~r ln accordance w1th thls lnv~lltlon.
~ . 2 lu a ucileluatic elevat1onal vlew al~o~lnlJ th~ ~roc~u o~ ~lllln~ tll~ corl~alner of 1'19. 1 ~33~4 with d hot f lll liquld product.
~ fer~3nce ls flrst made to l ig. 2 wherein there ls l-lustrated contalners 10 formed in accordance ~lth thls lnventlon mounted on a conveyor 30. I:ach contlln~r lO, ln ue(~uence, ls ~llled with ~I hot liquid product ~IS indicated by the arrow 32, af ter which a ~mall clualltlty of llquid nitroyen, indiciated by the arrow 34, 1~ placed wlthin the container. The thus fllled contalner lO then has a conventional closure dldtuly d~plled thereto a~i indicated by the arrow 36. Flg. 2 corresponds to Fig. 5 of USSN 306, 395.
As polnted out above, the container 10 will not ~lth~tdnd belng filled with a hot liquid product followed by lnternal pressurization and closing with the lnternal pre~sure being on the order of 40-45 psig ln that the base of the container 10 will be unduly ~tressed and su~ject to creep which will result in an undccepta~le lncrease in volume of the base and thus thu Yolum-~ of th~ contalner so a!; to result in an unacceptable h~ad space when the internal pr~ssuri~atlon is on the order of 40-45 psig.
.At thls tline, lt is pointed out that there havl3 b~en recent developlnents relating to improved preforms whlch ar~ stretch blow molded to form contaln~rs lnt~3nded for hlgh internal pressurization.
Such prlor art preforms have been improved by thlckenlng the base portion of the preform as cornpared to the thlcknesa of the body portion of such preform.
Such container~ are primarily lntended to be refillable where durlng washlng in a caustic bath the bases are ~ub~ect to stress cracking.
Thi~ in~entlon particularly relates to an lmproved preform, generally identlf ied by the numeral 12. ~r~e i)rl3forln 12 1~ of an ln~ectlon Inolded con~tructlon of ~'ET and like polyester resins. The 2~33~

prc~orm 12 l~ ~rovided with ~ custolnary neck finish 14 bulow whlch ther~ l~ d custon~ary capping flange 16.
Imm~dlat~ly below the capping flange 16, the pr~form 12 has a cylindrlcal portion 1B and thereafter ~ ru~b~ in wdll thick~ s in a shoulder forming portlon 20. ~elow the shoulder forlniny portion is a body portlon 22 of a substantially uniform wall thlckness. ~elow the body portion 22 is a base for~lng portlon 24 whlch terminates in a rounded g~nurally humlapherlcdl end 26.
The pr~form 12 i~ stretch blow molded in a conventional mold 40 of a split construction utilizing a ~trutch rod 42. The mold 40 has a cavity 42 of a conflguratlon for forming the container 10.
It ls to b~ understood th~t the proportions of tho Inold cavlty 42 dnd those of the ~reform 12 are crltlcal. It wlll be s~n that the shoulder forming portlon 20 19 stretched both so as to be axially ulongated and of an lncreased dialneter to form a tap~red ~houlder 44 on the container 10. Next, it wlll be seen that the preform body portion 22 has a thlcknu~s t and a length corresponding to an intended length of a contalner body 46. The specific wall thlckn~s dnd length ratio between the preform body portlon 22 dnd the container body 46 is one whereln the contalner body 46 ls provided with a stretch ratio on the order of 9 to 12. The stretch ratio in the hoop dlructlon ls ln the range of 3.2 to 3.7 while the ~tretch ratlo ln the axial direction is in the range of 2.8 to 3.2. The thus forlned container body 46, belng biaxldlly orlented, has a high resistance to lnturnal ~r~urlzation of the container 10 whlle havlng vury llttl~ r~istdnce to radially inwardly col l~u Wh~ uru lu a nu~J~tlvu L~ru~sur~ or vacuum ~lthln th~ cont~inur 10.

~3~

t~ lly Cllu ~su ~rnlln~ iJort10ll 24 of tl~e urlo lu ~Lrutcllud to for~ b~s~ ~ of tlle cont~ er 10, WIllCl~ bdL~U COrrt~ ond:i to tll:lt :i~lOWI~ ln ~ . 2 and lnclu~ lur~llty o~ s 50 whlcil ~re c ~ u~D ~ u r u l ~ t ~ y Ll ~ c ~ w ~ r o ~ ~ c t ~ r olll ~1 y~ r.~lly h~ pl~{-rlcal ~-ortloll 52 11~v1ng d recessed c~ r 5~ ~o tl~t tll~ conc~ or Seat!j on feet 56 u~ y t~\~ lu~Ju SO.
~ y lncruaslll~ tl~o w~ll thlckncss of the base ~rt~otl 2~ of tl~ ur~forul 12, tl~ se 48 1s of a ~r~at~r tlllchl~u~. turttlur, lt wlll bc seen that as tl)~ u l~rtloll 2~ of tllo ~)reLorul 12 1s ax1ally ~r~tcllu~, ~u w~ll dU belll9 ~tretcl~ed in tl~e hoop dlr~ctlon, Cllu gr~C~r w~ll thlckness glves a hlgher ~ o~uluY wlllcll lowur~ tl~ )lied stresses.
Tl~u co~ln~tlon of tlllckor wulls and incr~ased orluntatlol~ lrl tll~ ~d9~ 4~ ~erlllit~ the desired higher nltldl lnt~rn~l ~r~url~atlon of the container 10.
~ urt~l~r, ln ds~oclatlon with the improved cont~lllur ~t~u constructloll, the stloulder 44 and the ~o~y ~6 ~ru for~ud ~ltll d ll~oder~tely lligll degree of blaxl~l orl~ntatloll wltll tile orientation lnduced cry-Lalllnlty 1l~ ~h~U portlons of tlle container onh~nclny ~oLh tl~ tl~r~Dal ~t~lllty an~ th~ reslstance ~o cr~o~ d~orm~tlol~ ~t ~l~v~t~d teln~eratures.
~ L tl~lu tl~u, lt ls l)ollltL~ out that the lslv~nLlo~ lot ru~trlctud Lo tll~ ~peclflc base contl~uratlotl, ~ut tndy lncor~orat~ other avallable base contl~ur~tlunt~ cludlu~ tllo~e u~d ln Inoderate ~r~ uru colltalllurt~
In addltloll, wl~llu thu collt~lner body 46 has ~u~n ~ro~ly ~crl~d, lt ls to be understood that the cont~ln~r b~ly ~6 n~y lnclude .1 p~n~ ctlon 60 wlth a tly ruducu~l dl~ tt~r for ruce1vlng a label.
~ ltllou~h only ~ I)referred elnbodllnent of the S~ 3 ~

~r~form ~nd the contalner which ls stretch blow molded thurufrom hav~ bucn si~ecifically illustrated and d~crlbed hereln, it ls to be understood that minor vdrldtloll~ Indy ~e Inade both in the preform ~onf ltl~ratlon ~nd the container confi~3uration without dcparting fro~ the spirit and scope of the invention as def lned by the appended clalllls.

Claims (5)

1. A plastic preform for forming by stretch blow molding a plastic container specifically intended for receiving a hot liquid product at atmospheric pressure followed by temporary internal pressurization of said container as opposed to a similar plastic container intended for packaging of a liquid at a high internal pressure, said preform being of an injection molded construction and including a neck finish, a capping flange, a body portion for forming a container shoulder and body, and a bottom portion for forming a container base, said preform body portion for forming a container body being of a thickness and length for effecting a thickness reduction on the order of 9 to 12, and said preform bottom portion including a cylindrical extension of said preform body portion of an increased wall thickness as compared to the wall thickness of said preform body portion.

2. A preform according to claim 1 wherein the intended stretch in the hoop direction is in the range of 3.2 to 3.7 and in the axial direction in the range of 2.8 to 3.2.

3. A container for an initial pressurized filling with a hot liquid formed from the preform of claim 1.

4. A package comprising a stretch blow molded plastic container having a neck finish closed by a closure, a shoulder portion, a body portion and a base, said container having the appearance of being stretched blow molded from an injection molded preform of a wall thickness wherein said body portion has a stretch ratio of from 9 to 12 with said body portion having little resistance to external pressure, said base being of a greater than customary thickness, said container being initially filled with a hot liquid product at a temperature on the order of 185 to 190°F and internally pressurized to a pressure of 40-45 psig, and closed by said closure, the thickness of said base being one wherein said base heated by said hot liquid product and subject to said internal pressurization has acceptable creep deformation.

5. A package according to claim 4 wherein said increased base thickness is obtained by the preform from which said container is formed having a base of a wall thickness greater than the thickness of that preform portion from which said container body portion is formed.