CA1188061A - Process for preparation of coated oriented plastic container - Google Patents

Abstract

S P E C I F I C A T I O N
To All Whom It May Concern:

Abstract of the Disclosure Disclosed is a process for the preparation of a coated oriented plastic container,which comprises coating an aqueous latex or organic solvent solution of a vinyli-dene chloride copolymer on at least one surface of a parison, preform or sheet for formation of container which is formed by hot molding of a molecularly orientable thermoplastic resin, drying the coated parison, preform or sheet to form a coating layer, and subjecting the formed coated structure to draw molding such as biaxial draw blow molding or draw forming, wherein the coating layer of the vinylidene chloride copolymer is crystallized at the step of forming the coating layer or the draw molding step.
In the coated oriented plastic container prepared according to this process, the adhesion of the coating layer of the vinylidene chloride copolymer to the plastic container substrate is highly improved, and even under severe conditions, peeling of the coating layer is prevented. Moreover, the gas barrier property, strength and chemical resistance of the container are prominently improved, - 1' -

Description

~8~

Background of the Invention (1) Field of the Invention:
The present invention relates to a process for the pre~aration of a coated oriented plastic container.
More particularly, the present .invention relates to a process for the preparation of a coated oriented plastic container in which the adhesion, gas barrier property, strength and chemical resistance can be i~nproved by crystallizing a coatinr layer of a vinylidene chloride copolymer formed on a plastic container substrate.

(2) Dèscription of the Prior Ar-t:
plastic bottles prepar2d by l~elt-extruding and hollow-molding ( blo~.Y~molding ) thermoplastic plas^tics such as polyolefins are used in various fields instead of glass ~ottles because the plastic bottles have a li~hter weight and a better shock resistance than the glass bottles~
General-purpose plastics such as polyolefins are excellent in ~h~ moisture resistance and sanitary charac~
teristics, but the oxygen perm,eability eoefficient is 20 relatively high ~rld in bottles of these plastics~ pern3ea-tion of oxygen -through bottle walls is not negligible.
Accordingly, bottles of general-purpose plastics are not suitable æs vessels for preserving foods for a long ti~e OI` as vessels for cosmetics and the like where-~ hi~h 25 ~lavor-retaining property is required.
As container in which this defect is overcome) there have been de~eloped and proposed plastic container haYing a wall structure excellent in the oxygen barrier property.
~.,, Among l~elt-ex-trudable ther.rnoplastic resins ~hich are now availablet a saponified ethylene/vinyl ace-tate copolymer ( ethylene/vinyl alcohol copolymer ) is most excellent in the oxygen barrier prQperty. However9 this saponi~ied copoly~er is inferior in the moisture resistance, that is, the steam ~arrier proper-ty, and in this saponified ~opoly-mer, the oxygen permeability coeffieient -tends to increase as increase of the humidity. Accordingly9 ~hen this saponified copoly~ler is act~ally used for formation of plastic conta.iner, it is necessary to adopt a troublesome molding method in which this saponified copolymer is sandwi-tched by moisture resistant resins such as poly-olefins and the resulting laminate is fed to the molding step to form a multi-layer laminate container.
S~mary of the Invention To our surprise, it was found that when a vinylidene chloride copolymer is coa+ed in the form of a~ aqueQus latex or organic solvent solution on the sur~ace of a parison preform or ~heet for a plastic container formed by hot molding and this c~ating layer is cryst~ ed, the adhesion of the coating layer to the ~lastic container ~ubstrate is highly in~roved.
It is therefore a primary object of the present inven-tion to provide a process for the preparation~of a coated oriented plastic container in which the adhesion of a coating layer of a ~inylidene chloride copolymer to a ~olecularly oriented plas~lc containPr substrate is highly improved.

- 3 -6~

Another o;~jec~ of -the present invention is -to proYide a process for th~ preparation of a coated oriented plastic contairler ir. which peeling of a coating layer is prevented even under such severe conditior~ that the content in the con~e ner is frozen or when the container undergoes such an extreme deformation as ~/Jill crush th.e bottle at low -tem~e.atures.
Still another o~ect of the present invention is to provide a process for -the prep~rat iOll of a coated orien-ted plastic co~tainer in which not only the adhesion of a coat1ng layer of a vinylidene chloride copoly~er but also the g~s ~arrier property, strength ~nd chemical resistance are h 7 ~hly i~proved.
More specifically7 in accordance with the present inYention, there is provided a process for the preparation of a coated oriented plastic container~ which comprises coating an aqueous latex or organic solvent solution of a vinylidene chloride copolymer on at least one sur~ace of a parison~ pre~orm or sheet for formation of container, which is fo~rmed by hot ~olding of a molecularly orientable thermoplastlc resin, drying the coated parison~ preform or sheet to form a coating layer, and subjectLng the formed coated structure to ~raw molding such as biaxial draw blow molding or draw forming~ wherein the coati~g layer of -~he vinylidene chloride copolymer is crystallized at the step of forming the coati~g layer or the draw molding step.
~rief 3escription of the Drawings ~8~

Fig. 1 is a partially sectional side view illustra-ting one embodiment of the plac~tic bottle according to the present inventionO
~ ig. 2 ~hows an infrared absorption spectrum of a coated f.ilm formed by coat~ng 2 ~inylidene chloride resin on a polyethylene fllm.
Detailed ~escription o~ the Preferred Em'~3diments Referring to ~ig. 1 illustrating an embodiment of the coated plastic bottle of the p.esent ir.ventionJ this 10 bottle 1 eornprises a peripheral wall 2 having a Gircular or ellipsoidal section 3 a mouth po~tion 3 eonnected inte-gr~lly to the peripheral ~all 2 and a bottom portion 4 co~r,ected to the lower end of the peripheral wall 2. A11 oi' these bottle ~-~alls comprise a plastic hottle substrate 15 5 form,ed from a rllelt-moldable -thern~oplastic resin by bia~cially drawing blow molding or draw form~ng, and a ccating la.yer 6 of 8 ~inylidene chlorlde copoly~er formed on the surface of the substrate 5 . The coating layer 6 may be forlr~ed on both ;the sur~aces of the bottle substrate 20 5 as sho~wn in Fig. 1 or it may be formed on~y on the inner or outer surface ~f the bottle su~str~te 5.
It is known that a vinylidene chloride copolymer ls a resin e~cel' ent in the oxygen barrier property.
However~ hot molding of this vinylidene chloride copolymer is diîficult, and the copolymer should be handled in -the form of an aqueous latex or organic solvent solution.
The critical feature of the present inven-tion resides in the find~ng that 9 as pointed out hereinbefore~

, 6i when a vinylidel~e chloride c~polymer is coated in the form o~ an aqueous latex or organic solvent solution on the sur~ace of a plastic parison, prefor~ or sheet formed by llot molding in advance and the coated structure is sub~
5 jected -to àraw molding to form a composite plastic container, if the CQating layer of the vinylidene chloride copoly~er is crystallized at the step of forming the coa-ting layer or the draw molding step, the adhesion of the coating 7ayer to the plastic ,substrate is highly improved.
In a coated plastic container formed by ordi~arily coating a vinylidene chloride copolymer and drying the coa-ting layer, the adhesion of the coating layer to the substrate seems go~d, However, when this coated container is placed under such severe temperature conditions that the content liquid is frozen or when it is crushed at low temperatures, the c~ating layer of the vi~ylidene chloride oopoly~er is readily peeled from the COntaLner substrate. This pheno~enQn is similarly obse~ed when a 20 parison or the like prcvided with a coating layer o~ a vinylidene chloride copol~mer is subjected to draw mold~
ing.
In the present invention, by positively crys-tall.zi~g the vinylidene chloride copolymer constituting ~he ooating layer formed on a parison, preform or sheet to be subjected to draw molding at the step of forming the coating layer or at the dr~w mQldi~ step, the ad~.esion of the coat ing layer to the plastic bottle substrate is i~proved to ~88~

~ch an extent that under the above-merltioned severe conditions~ peellng is no-t subst~ntially caused. This finding is quite ~mexpected from the co~mon sense in the art o~ coatlng. ~lore specifically~ it has been considered that when a cr~stallizable therrnoplastic resin is used as a coating layer, from the viewpoin~t of the a~hesion of the coa-ting layer, it is impsrtant that the resin should not be crystallized, Accordin~ly, in the conven~
tio~lal raethods~ there ha~e been adopted rapid cooling means for passing the coating layer rapidly through the crystallization temperature r~nge. In contrast~ in the present invention, a parison or the like to be sub~
jected to draw molding i5 coated ~ h a vinylidene chlo~
ride copolymer and the coating layer i s crystallized 15 by a heat treatment at the coating-forming step or ~lra.w molding step, whereby the acUlesion of the coatin~ layer to ~ molecularly oriented plastic container formed by draw molding is prominently improl~red with this cx-ystalli-zation . Thi~ fac t will beco:oe apparent from Exa;2lples 20 given herei~after.
In order to attain the objects of the prese:rlt invention, it is preferred that the coating layer of the vinylidene chloride copolymer be crystallized so that the degree of crystallization of the coating l~yer of the ~inylidene chloride copolymer is at least 0,5) especially a-t least 0.8, as determined according to the in~rared 2bsorption spectrllm method ~escribed hereina~ter.
According to the present invention, by crystallizing 8~6~

the vinylidene chlorlde copolymer constitu-ting the coating layer, the barrier properties to gases suoh as oxygen7 ehrbon dioxide gas and steam can prominen-tly be improved, and mechanical properties sueh as the -tensile strength, impact resistance and abrasion resistance ~
the chemi&al resistance such as the alkali resis-tance and the hot water resistance such as the resistanoe to whi~ening by hot water can also be inpro~red prominently.
Therefore~ a eoated container excellent in vc~r.ious pro-perties can be obtained according to the present in~en~tion.
The parison, preform or sheet that is used in the present inv-ention can be obtained from a molecularly orientable~ hot moldable thermoplastic resin by optional known hot molding means. For example, a parison for : biaxial draw blow molding can be obtained by extruding - the above-mentloned resin in the form of a pipe and cut-t ~ g the pipe. Furthermore, a bo-ttomed parison for bi~xi~l draw blow molding c~n be obta~ned by ex~r~lding the resin in the eylindrical form, pinching off the extrudate by a split mold ~nd subjecting the extrudate to preliminary blow molding. Moreo~er, a bottomed parison for biaxial draw blow mclding can be obtained by injectiQn~molding the above-mentioned resin. ~till further, a sheet for dra~l forming of a wide-mouth container ean be o~-ta.Lned by extruding the resin in the form of a sheet through a T~die or the like.
As preferred examples of the resin used for formation ~138~6~

of the parison, there can be mentioned olefin resins such as isotac-tic polypropylene, crystalline pro~ylene/ethylene copolymers, crystalline propylene/butene-l copolymers 9 crystalline propylene/butene-l/e-thylene copolymers and ethylene/vinyl alcohol copoly~ers, polyesters such as polyethyle~e terephthalate 9 poiybutylene tere~hthalate and polyethylene -terephthalate/isopnthalate, poly~mides such as nylon 6~ nylon 6,6 and nylon ~,lO, polystyrene7 styrenè type copol~ers such as styrene/blltadiene ~lock copolymers, styrene/acrylonitrile copolymers, styrene/
butadiene/ac.rylonitrile copolym~rs ( ABS resins ~ polyvinyl chloride, vinyl chloride type copolym~rs such as vinyl chloride/vinyl acetate copolymers, poly~ethyl ~ethacrylate and acrylic copolymers such as methyl metnacryl~te/ethyl acryl~te copolymers, ~nd polycarbonate, though usahle resins ~re not limited to those exemplified above.
~ These thermoplastic resins may be used singly or in the ; f orm of a blend of ~Yo or more of -them. The plastic parison or ~he like m3y ha~e a single layer structure or a multi-laye.r l~minate structure formed, for exarnple, by simultaneous melt extrusion.
An aqueous latex or organic solvent solution of a vinylidene chloride copolymer is coated on at least one surface of the above--mentioned plastic parlsGn pr the like.
As the vinylidene chloride copolymer, there is used a copoly~er comprising vinylidene chloride as the main c~nstituent monomer and at least one comonomer ~elected ~L~88~36~

from an acrylic or methacrylic monomer, a vinyl aro.~atic mon~mer such as styrene or vinyl tolue~e, a vinyl ester such as vinyl acetate or vinyl propionate, a diolefin such as butadiene or isoprene, and methyl vinyl etherl glycidyl allyl ether, vinyl chloride, trichloroethylene, tetrachlorcethylene, vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, maleic anhydri~e, fumaric acid, vinyl succinimide and vinylpyrrQlidone As suitable exa~ples of t.he acrylic or methacrylic monomer9 there can De mentioned acrylic acid, acrylonit rile, acrylamide, ~ethyl acrylate, ethyl aorylate, methyl ~chloroacrylate7 propyl acrylate, butyl acrylate, hexyl acrylate, octyl acrylate, cyc~ohexyl acryla-te, glycidyl acrylate, 2-hydro~ethyl acrylate, acrylic acid mono-glyceride, phenyl acrylate, methacrylic acid, methacrylo~
nitrile, methacrylamide~ methyl methacrylate, amyl methacrylate, glyci~yl methacrylate, methacrylic acid monoglyceride~ 2~hydroxypropyl ~ethacrylate9 ~methoxy-ethyl methacrylate, ~-aminoethyl methacrylate and ~-N~N-diethyla~inopropyl methacrylate.
An a~ueous latex of the vinylidene chloride copolymer having a solid conc~ntration of 20 to 65 % and a viscosity of ~ to 500 centipoises is preferably used in the present invention A solution having a solid content of 5 to 60 % in an or~anic solvent such as toluene 7 tetrahydrofuran 3 e~hyl acetate, methylethyl ketone9 cyclohexa~le~ dimethyl-formamide, dimethylsulfoxide or dioxane is used ~s the organic solvent solution.
Coating of the plastic con-tainer substrate with the abo~e`-mentioned copolymer latex or solution may be accomplished by adopting at least vne of known coating methods such as dip coating, spray coating, brush coating, roller coa-ting, electrostatic coating, cen^trifugal coating 9 cast coatLng and electrophoretio coating methods.
The coating operation may be conducted only once or a multiple stage coating method m~y be adop-ted. If desired, the plastie container substrate such as a parison may be sub~ected to a wetting property-improving preliminary treatment such as a pretreatment with an anchorLng agentS
a corona discharge treatment, a sur.ace active agent coating treatment or a chemical etching treatment.
Furthermore, in order to impart an electric conductivity~
the plastic container substrate may be subjected to a G onducting treatment.
In the present invention, it is preferred that the coating layer of the above~mentioned copolymer be formed on ~oth the surfaces of -the plastic container substrate.
However, in order to shu-t gases contained in ~ir, the coating layer ~ay be formed on the outer surface alone, and in order to prevent escape of a gas or perfume fro~
the content of the bottle, the coating layer m~y be formed on the inner surface alone.
As pointed out hereinbefore~ the vinylidene chloride -ccpolymer that is used in the present invention is excel~
lerlt in the combination of the oxygen barrier property ~8~

and water Yapor barrier property ~ld the humidity dependeney of the oxygen barrier property is very low.
Accord ~gly9 when the copolymer is formed on the plastic container subs-tra'e in the form of a very thin layer, excellent barrier properties to various gases can be obtained. More specifically, satisfactory results can ordinarily be obtained if the copolymer is formed in a layer on the c.ontainer having a thiekness of 0.5 ~o 40 especially 1 to 30 ~.
The conditions adopted for drying the coa-ted copol~Tmer layer are ch~nged according to the thickness of the coating layer, but ordinarily, a sufficient drying effect can be attained when dryin~ is carried out at a temperature of 40 to 150C ~cr about 2 seconds to about 100 hours.
In the present invention, if the aqueous latex or crganic solvent solution o~ the vinylidene chloride copolymer is c~ated on a parison, preform or sheet formed by hot molding while the parison, preform or sheet is still hot, drying of the ~oating is accomplished by util~zing heat posse.c~ed by the parison or the li~e simultaneously with eooli~g of the parison or the like.
Accor~ingly, this ~ethod is adva~tageous.
Draw molding of the parison~ preform or sheet coated with the vinylidene chloride copolymer c~n be carried out under kno~n conditions, More specifically~
biaxial draw blow mo1ding or draw forming such as air pressure form~ng or plug assist forming is carried out under such conditions as causing molecular orientati~n ~ 12 :~1!38~6~

by draw ing .
In case of biaxial clraw blo~ molding~ tlle parison or preform is mechanically drawn in the axial direction in a split mold, and si~v.ltarleously, a fluid is blo~
5 lnto the parison or preform to expand and draw the pari~
son or preform in the circl~mferential direction. In case o~ a bottomed parison or preform ~ dra~l~?ing in -the axlal direction may be accompli~hed by pushing a drawing rod i.r~to the bot to?.3;ed p~rison or preIorm9 and in case of a 10 tube 9 drawir~g in the axial direction ~ay be ac~omplished by hold~ng both the ends of the tube by a clamping mechanism or passing the tube between two rolls d.iIfering in the rotation speed. It is preferred that draw blow molding be carried out so ~at the in~plane orienta-~ion 15 coefficient ( ~ + m ) OI the barrel portion of the forrred corltainer is 0.05 to 1.07 especially 0.1 to 0.9~ ~or this purpose s it is preferre~ that the ~ra.w ratio in the axial direction be 1.10 to 207 esp~cially 1,20 to 15, and that the dra~r ratio in the circumferential d:irection be 1,20 to 50~ especlally 1.25 to 30.
In draw .forming of a wide-mouth Gontainer ~ the draw forming oper~ti~n is G~rried ou-t under temperature con-ditions cAuSing molec1l1ar orientation by air pressure forming or plug assist forming so that the draw-~ratio defined by the îollowinO for~nula is 1~10 to 100, espe~
cialty 1,20 to 5C):
thickness of sheet Draw rat i o thickness o:f barrel ~ 13 --8~63L

Aceording to the present invention~ the coa-tLng layer on the plastic substrate is maintained at the crystallization tem.perature of the vinylidene chloride copolymer at the eoatirlg layer~for~lng step or dr~w molding step, whereby crystallization of the copolymer is accompl~shed. When it is intended to effect crystal~
li2ation at the coating~folming step9 the ~bove-~,entioned heat -trea-tment is carried out si~.ultaneously with or subsequently to tne ~ryirg of the coating layer, In this oase, it is necessary that the coating layer ~hould be maintained at the crystallization temperature in the substantial absence of water or an organic solvent~
because formation o~ a fi~m of the vinylidene chloride copolymer is not substan-tially ad~anc.ed in the presence of water or an organic solvent.
When it is intended to effect crystallixatlon of the coating layer at the draw moldin~ step, the heat trea.;ment of heating the coated parison or ~reform a-t t~e drawing ~emperature and the temperat-ure and time for the draw molding operation can be utilized for crystallization of the coating layer. This crystallization treat~ent is especially effective when the draw molding temperat-~re ef the plastic substrate is relatively hi~h.
The degree of crystallization of the vinyl~dene ohloride copol~er depends on both the temperature and time of the crystallization treat~ent~ Furthermore9 there is a fear oi' t~ermal deterioration Ol the vin~lidene chloride copolymer du~ to the heat treatment for crystallization, _ 14 -36~

In the present in~ention, -the heat treatrnent of the coat.ing layer is carried o~-t so that the following reqv.ire~ents are satisf:ied:

4~3K ~- T '~ K and ~t (T ~ 313) >
500 ~ lim I d logt = 10 (1) a~ o-' a X

~ t (T - 313) especially, 300 _ lim J d logt ~ 3 (2) a--~o a wherein T stands for the te.~lperature (K) ~or the heat trea-tment of the coating layer, t s-tands for the time (seconds) of the heat treatment oonduoted at TK7 and k is a constant deterrnined accordlng -to the kind of the vinylidene chloride copolymer, which is ordinarily in the range of 5 ~ k > 0.5.
If the temperature-time integration ~alue is too small and is below the a~ove range, the crystallization is not sufficient and it is dif~iGUlt to increase the adhesion to a sa-tisfactory level. If this value is too large and exceeds the above range9 the coating layer of the vinylidene chloride copolymer is thermally deteriorated and physical proper-ties are rather degraded.
In t~e present invention~ it is p.referred th~t af-ter the heat trea~tment, the coat~ng layer be ~apidly cooled 50 tha-t the tims--temperature integra-tion va~ue of the heat tre~tment conditions i5 not outside the above~mentioned range. In the case where the final heat treatment i5 draw molding~ it is preferred ;t`~at the plastic container formed by draw molding he rapidly cooled.
In order to protect the above-mentioned coating layer and improve the weatherability, scratch resistance and gas barrier pro-perty thereof, a protecting layer composed of a film-for~ning syn-thetic resin, other than the vinylidene chloride copolymer, may be formed adjacently to the coating layer according to the known and dry-ing procedures.
The present invention will now be described in detail with reference to the following Examples that by no means limit the scope of the invention.
In the Examples, the crystallization degree, freeze peeling degree, low temperature adhesion strength (falling strength), scratch resistancc (pencil hardness), chemical resistance, hot water resist-ance (boiling test) and oxygen permeation rate of each coating layer were determined according to the following methods.
(1) Crystallization Degree:
The crystallization degree was determined according to the method disclosed on page 679 of "Emulsion Latex llandbook" (compiled by Editional Conference of Emulsion Latex llandbook and published by Daisensha). ~lore specifically, the side wall portion was cut out from a coated container and the absorption spectrum of the coated sur-face was determined according to -the total reflection method, trans-mission method or differential spectrum method using an infrarad spectrophotometer (Model A-3 supplied by Nippon Bunko Kogyo). Among absorption bands characteristic of vinylidene chloride, , ~

,,, which appear at 7~3, 8759 1046 and 1071 cm 19 the absorp-t iOIl ~ands at 1045 and lQ71 cm 1 are considered to indi-cate the degree of crystal].i~ation. Accordlngly, the ratio of the absor ~nces at 1046 and 1071 cm ~s designated as the c~-stallization degree. From the results of the X ray diffrac-tometry, it is proved that increase of the above-men-tioned absorbanee ratio means advc~ce of orystall~ zation in the internal st~uc-ture of`
polyvinylide.~e chloride. Ex~m.ple~ of the results of the measurement of +he absorption spec~rum and absorb~nces are shown in Fig. 2. Incidentally, Fig. 2 shows the results obtained with r~spect -to a sample formed by ooatLng a vinylidene chloride latex on a polyethylene film. The absorption bands at 720, 1350~ 1425 and 2goo cm 1 are those characteristic of polyethylene.
~2) Freeze Peeling ~egree:
A coa-ted container~ the weight of which had been measured in advance? was filled with distilled water, and water was frozen and e~pandecl at 15 C. The coa-ting 20 which was observed to ha~e been peeled was remoYed Irom the container, and t~e weight of the empty container was then measured. The peeling degree (%) was calculated by dividing the difference bet~een the weight of said co ntainer and the weight of the container befo~e the f reezing by the total amount 5f the coating according to th e following forrmula:

eight before freezing) -Peeling (weight after freezing)]
degree (%~ total arnount of coating x 10 (3) :Low Te.~peratu~ e hdhesion Strength ( falling strength ):
A coated contailler was ~illed with an aqueous solu-tion of sodium chloride ( the sodium chloride concentra-

5 tion was 10 o,' by weight ) rain-tain~d at - 1C~ and the contai ner was plugged and was let to fall do~n~ on the .~ concrete surface fro;n a height of 1.5 ~ so that the side f.~ce of the container impinged against the concrete surf~ce . For each coating condition ~ five sample container w~re tested. Then, in order to determine whether or not micro-cracks were form~d, the side ~Yall portion of the container subaected to the falling test was cut GUt and was dyed at 50C for 5 ~inutes ln a dyeing aqueous solution o~ Malachite Green, and ~he side ~11 portion was o~serued by a microscope ( 100 magnificatiorls ).
: The falling ~trength was e~aluated according to the fo ll owing scale: ' O: no cracks were formed in any of the ~i~e s~mples.
~: cracks were fo r~ed i n 1 to 4 samples .
X: cracks were formed in all of the five sa~ples.
~4) Scratch Resistance ( pencil hardness ~:
Und~r conditions of a temperat~e of 20C and a relati~e hu~idi-t~,~ of 40 %, a weight of 0,5 Kg was pl`aced . on each of penclls ha~ing a hardness in the range of fro~
: 6B to 6H~ and lines having a length of about 2 cm were drawn on the coated surface of a ~arrel portion cut out ~ 18 --:~8813~;~

fr~m a sa~ple container. Then, pencil dusts left on tne surfaces were st.ept away, and the surf~ce of -the sample container was ~xa.~.lined by a magnifyi7lg glass of 10 magnifications and the scralch resistance was evaluated based on the hardness of the pencil which left a scra-tch on the surface. Accordingly, the pencil ~ardness 6B
indicates the lowest scratch res~stance, and the scratch resistance is increased i~ the order of 5B, 4B~ 3B~ 2B, B, HB, F, H, 2H, ~H, 4H and 5H and the pencil hardness 6H indicates the highest scratch resistance.
(5) Hot Water ~esistance:
A squ~re sample of about 3 cm x ~out 3 cm was cut out from the barrel wall OI the coated container and was ~oiled on a thermQstat hot water tank maintairled at 95C for 30 minutes. Then~ the sampl~ was taken out from the tank and the whitening state was visually ex~mined by a panel of five ex~erts. S~mbols shown in the foll~-ing Ex~mples h~ve the followLng meanings:
O ; ~ive or four experts judged that whiteni~g did not occur.
: two or three expert jud~ed that whitenlng did not occurO
X : one or none of the two experts judged that whitening did not occur.

(6) Chemical Resistance The side wall porti~n of the coated container was cut out and i~mersed in ~n a~ueous solution containin~
10 ~0 by weight of c.austic soda at 25C overnight.

~8~

Before this ~Imerslon treatment, the total transmission of rays having a visible range wavelength of 400 m~ ~,as m e~sured with respect to the san7ple by using an integra-ti,~g ball in a self-recording spectrophotometer ( supplied by Hitac~li ), and the -total transmission was similarl~
measured after the treatment with the ~queous soluti~n of caustic soda. The che~ical resistance was evalllated based on the de~erioration degree ex~ressed by the ratio Tafter/Tbefore, in ~hich Tbefore represents the total transmission of the sample before the caustic soda treat~=
ment and Tafter represents the total transmission of the ~ample after the caustic soda treatment~ A smaller value of the deterioration degree me~ns a larger deterioration.
~7) Gas Barrier Property:
As the ~as ~arrier property, t.~e ox~gen per~eation rate (~2) at a te~..perature of 20C and a relative hu~idity of 0 ~0 was measured according to the following pr~cedures.
A barrel wall of a container to be measured was out into a predetermined size and an obtained sheet-like sample was used ~Dr the measure~ent. A gas permeation tes~er ~nufactured by TQYO Tes-ter Kogyo K.K. was used f or the measu ement. The sample was fixed between two chambers of thls tester, and s~lction was effected in one chamber so that the pressure w~s reduced be~ow 10 2 25 mmHg ( low pressure side ) while in the otiler chamber ( high pressure side ), the atmosphere was replaced by dehumidified oxygen gas so that the o~rgen gas pressure was one atm3sphere. The change of the pressure increase with the lapse time was read on a recorder and the oxygen gas permea-tion rate Q2 was determined from the read values.
The measurement was carried out at 20C and the moisture was removed from the high pressure side chamber so that the relative humidity was 0 %.
Example 1 An anchoring agent (EL-220/EL-200-Ad supplied by Toyo Morton K.K.) was spray-coated on one surface of an isotactic poly-propylene sheet having a width of 30 cm and a thickness of 0.8 mm, and the coating was heated for drying at 80C for 90 seconds. Then, a polyvinylidene chloride latex having a composition comprising 86 %
by weight of vinylidene chloride, 5 % by weight of acrylorlitrile, 3 %
by weight of methyl acrylate and 6 % by weight of glycidyl methacry-late (dispersion medium ~ water, solid concentration = 51 %) was spray-coated on the sheet. The average amount of the vinylidene chloride resin coated on the surface of the sheet (average thickness) was 10 ~. Then, the sheet was subjected to plug assist vacuum form-ing at 135C so that the coated surface was formed into the inner sur-face~ to obtain a square wide-mouth bottle (cup) "A" having a length of 9.7 cm, a width of 9.7 cm~ a height of 3.2 cm and an average thickness of 0.~7 mm. T}le heating time was 30 seconds. The inner surface of a square wide-mouth bottle of isotactic polypropylene formed from an mcoated sheet under the same forming conditions as described above was coatecl with the above-6~

merltloned a~choring agent and then spra~r coated with the ~ ~ /y ~ i ' Y / ~ ~ C c ~ / c, ., ~t /., ,, ~
r^~ abo~e-mentioned ~rin~;lidenc chloric'.e, and the coated bot-tle was dried a-t 80C for 2 minutes. The average amount coated of the vinylidene chloride resin ( aveTage 5 thiel{ness ) was 8 Il. The obtained bottle is deslgna! ed as " bottle B ''0 llhe cryst.alli~ation degree, freeze peeling degree, low temperature adllesion stre~tn ( falling s-trength )~
~oratch resistance ( pencil n~rdness ~ 9 hot water resis~
10 tance, chemical resistance and oxygen permeati on rate Gf each of the bottles A and B were measured according to the abo~e-menti~ned methods~ The obtained results are shown in Table 1, Tabl e Bottle A B
Crystallization Degree 1.02 0-47 Freeze Peeling Degree (%~ 0 8 Falling Strength Q X
Pencil Hard~ess 4~ 2H
~ot Wa-ter Resistance. O X
Chemical Resis-tance 0,90 0,37 Q2 ( cc/m2 day atm,) 18 34 From the results shown in Table 1, it will readily be understood that by the heat treatment at the molding step ~ the degree o~ crystalliza^t ion of the vinylidene chloride resin i.s increased, resulting in improvemen ts of the freeze peeling strength, low temperature adhesion .~B8~61 strength ( f~lling strength ~, scratch resistance i' pencil hardness ) 9 hot water resistance, chemical resistance and gas barrier property.
Example 2 The non~heat treatedt vinylidene chloride resin-coated bottle B described in Exa~ple 1 1.~as heat-treated under the hea-ting conditions for the plug assist vacuum forming, described in Example 1. The obtained bottle is designa-ted as " bottle C ".
The crystallization de~ree, lreeze peeling degree, low temperature adhesion strength ( falling strength ~, scratch resistance ( pencil hardness )~ }lOt water resist,~nce, chemical resistance ~nd oxygen permeation rate of the bottle C were determined according to the above-mentioned methods. The obtained results are shown in T~ble 2.
Table 2 Bottle C
Cry~talli~-ation ~e~ree 0.95 F.reeze Peeling Degree (~) 0 Falling Strength O
Pencil Hardness 4H
Hot Water Resistance O
Che~.ical ResistanCe 0.87 Q0z (cc/m2-day-atm) 22 ~.~hen the results sho~ in Table 2 are cornpared wlth the results shown in Table 1, it will readily be understood :~8~3~6~1L

that when the bottle B is heat-treated under the above-mentioned conditions, the degree of crystallization of the coating layer of the bottle is increased, resulting in improvements of the freeze peel strength, falling strength, penc.il hardness, hot water resistance9 chemical resistance and oxygen barrier property.
Examlple ~
The inner surface of a preform ( bottomed parison ) of amorphous polye-~ylene terephthalate having an outer surface area of 130 cm2, a weight of 63 g and an average thickness of ~.6 mm was dip~coated ~ slush-coated ) with a polyvinylidene chloride resin emulsion having a compo sition compris ing 90 % by weight of vinylidene chloride and 10 % by weight of acrylonitrile ( dispersion medium ~ water, solid concentration ~ 45 % ), and the coated preform was dried by blowing h~t air maintained at 100C for 1 minute. The amount coated of the vinylidene chloride resin was 0.23 g~ The preform was heated at 120C for 25 seconds an~ biaxially draw-blow-molded by using a known biaxial draw blow molding machine to ob~ain a biaxially drawn polyethylene terephthalate bottle D
having an inner volume of 2000 cc and an average total thickness of about 0,50 mm, the inner surface of which was coated with the polyvinylidene chloride resin ~ the : 25 a~erage thickness of the coating layer was 1.5 ~
The uncoated preform was biaxially draw-blow-molded under the above-mentioned conditions and the resulting biaxially drawn polyethylene terephthalate bottle was 6~

dip-coated ( slush-coa-ted ) with -the above-mentioned vinylidene chlori~de resin emulsion. The coated bottle was dried by blowing hot air maintained at 100C for 2 minutes. The average coated amount ( average thickness ) of the vinylidene chloride resin was 3 ~. This bo-ttle is designated as " bottle E ". The bottle E was heat-treated in an air~circulating oven under the above-mentioned conditions adopted for the biaxial draw blow molding machine. The heat-treated bottle is designated as " bottle F ".
The crystallization degree, freeze peeling degree, low temperature adhesion strength ( falling strength ), scratch resistance ( pencll hardness ), hot water resistance, chemical resistance and oxygen permeation rate of each of the bottles D, E, and F were determined according to the above-mentioned methods~ The obtained results are shown in Table 3.
Table 3 Bottle , D E F
Crystallization Degree 1.38 0.70 1.22 Freeze Peeling Degree (~) 0 32 0 Falling Strength O X O
Penci1 Hardness 4H 2H 4H
Hot Water Resistance O -X O
Chemical Resistance 0 93 0.61 0.91 Q2 (cc/m2-day-atm) 6.3 6.8 6.4 From the results shown in Table 3, it will readily 6~l be ~mderstood that the heat treatment efEect can also be attained by the heating at the biaxial draw-blow-molding step. It will also be seen that the degree of crystallization in the bottle D is higher than in the bottle E and there-fore, the bottle D is excellent over the bottle E. in the chemical resistance and gas barrier property. It is considered that the reason is that also the vinylidene chloride re-sin is oriented by biaxial draw blow molding.
Example 4 The outer surface of an amorphous polyethylene terephtha-late preform as described in Example 3 was spray-coated with a vinylidene chloride copolymer solution having a composition compris-ing 90 % by weight of vinylidene chloride, 5 % by weight of acrylo-nitrile and 5 % by weight of glycidyl acrylate (solvent = 65 % of tetrahydrofuran and 35 % of toluene; solid concentra-tion = 20 %) in the state where the preform was still llot (the surface temperature was 80C) just after injection molding. Then, the coated preform was heated at 100 C for 2 minutes and biaxially draw-blow-molded by using a known biaxial draw blow molding machine to obtain a biaxially drawn polyethylene terephthalate bottle "G" having an inner volume of 2000 cc and an average total thickness of about 0.50 mm, the outer surface of which was coated with the polyvinylidelle chloride resin (the aver-age thickness of the coating layer was 2.0 ~).

~hen t~le ab~ . ~."enti or ed pr efGrrn prepared by inJec-tio.r~ 1.ding ~as ccoled -to r~om tenperature, tk.e preforrn was spray~c~ated ~ the above-mentioned vinyl~de~e chloride copolymer solution, and the coated preform w~s dri-d at 80C f3r 90 seconds in 2n air circulati~g o~en and was -then b.axiall.y dra~ blc~ r~olded under the same conditions as described above t~ obtain a biaxially drawn polyethylerle tereph+.h~la-te bot-t:l e " H "
having a coa ting layeI thickness of 1.8 ~I
The crystalli~ation degree, freeze peeling degree, low temperature adhesion strength ( falling strength ), scratch resistance ~ pencil hardness ) ~ hot water resis~
-ta~lCe, chemi cal strer~gth ar d oY.ygen perrneation rate OI
each of the botlles G and H were determined according -to 15 the above-rnen-tioned .~ethods, The ob~ined results are shown in Table 4.
Table 4 Bo ttle G H
Crystallization ::)egree1.32 1.10 Freeze Peeling Degree (~o) 0 10 Falling Streng th , 0 Pencil Hardness 4H 2H
Hot Water Resistance O X
Chemical Resistance 0 93 0~76 Q2 (cc/m2.day.a-tm) 6.1 7.3 From the results shown ir~ Table 4J it is seen that the degree of crystallization of t;he bottle G is ; ~ 20 higher than that of the bottle ~ and ~he bottle G is ex-cellent over the bot~le H in the freeze peel strength, 27 ~

~8~

fallina strength, pencil ha.rdness, hot ~ater resis-t~nce and aas barrier pr~per-ty. It is considered that the reason is that since the prefor~n which has not ~een cooled is coa-tedS the hea~t treat~.,ent effeGt is a-ttained at the s-tep of heati.1g the coating layer Example 5 A pipe having a three~layer structure co~prising an outer layer of isotactic polypropylene, an in-terrnediate layer of an adhesi~e ( maleic anhydride~ odified poly-propylene ) and an inner layer of an ethylene/vinylalcohol copoly~ler, in which the outer layer/intermediate layer/inner layer t~ickness ratio was 20:0 1:1, was formed by extrusion molding, and just after extrusion molding, the inner surface of the pipe was dip~coa-ted with a polyvinylidene chloride latex having a cornposition com~
prising 90 ~ by weight of vinylidene chloride, 5 % by weight of me ~yl methacrylate and 5 ~ by ~eight of methyl : methacrylate ( dispersion medium = water, solid concen--tration = 50 % ). Also,the cooling effect was attained by this coa~ing operation. By using a known biaxial draw molding machine, the coated pipe was heated at 150C for 5 minutes ~Id biaxially draw blow-molded to obtain a biaxially d~awn la~inated bo-ttle " I " havLrg an i~ner volume o 500 cc and an average thickness of 500 ~, the inner suriace of which was coated with the polyvinylidene chl3ride resin ( the average thickness of the coating layer was 3 ~ ).
An uncoated ~lree-layer pipe having the abcve-- 28 ~

8~

mentiolîed la~er s-tructure was biaxially draw-b]o~;-r.)olded in the s~.~e mal~ner as dese,ribed abo-~e, and the inner surface of the uncoated 9 biaxially dra~ln, laminated bot-tle ~7as di~-coated ( slush-coated ) with the above-mentioned vinylidene chloride resin latex and the coatedbottle was dried by blowi.ng hot air maintained a-t 110C
into the bot-tle for 9C seconds. The so~obtained, biaxially drawn~ la~inated bot-tle having -the inner surface coated with the ~.nylidene chloride resin ( ~he average thickness of the coating layer was 4 ~ ) is designated as " bottle J ''0 The crystallization degree, f'reeze peeling degree9 low te~pera ~re adhesicn ( falling streng-th ), scratch resistance ( pencll hardness ), chemical resistance and oxygen permeation rate of each of the bottles I and J were de-termined according -to the abo~e~mentione~
methods~ The obtained results are shown in Table 5.
Table 5 Bo-ttle , I J_ Crys-talliza-tion Degree 1.41 0,83 Freeze Peeling Degree ('~) 0 30 Falli,ng Strength O X
Pencil HaI~dness 4H 2;~
Hot Water Resistance O ~'X
' Chemical Resistance 0089 0,62 ; Q2 (cc~m day-at.~) 0c63 0.96 From the results shown in Table 5, it will readily ~ 29 -be u~e7st~od that by the hea-t treatmen-t effect attained at the ~olding step, the degree of crystal~ization of the vinylidene chloride resin is increased, resulting in irnprove~rients of the f`reeze peel strength, low temperature adhesion strength, scratch resist~nce, chemical resis-tance and ~as barr.ier property.
Exarnple 6 ~ne outer surface of a preform ( bottomed parison) of a~orphous polyethylene tereph ~lalate as described in Example 3 was dip~coated wi-th the same vinylidene chloride resin emulsion as used in Exa~ple 3. Just after the coating operati~n, in -the state where the prefor~ was not yet dried, in a heating zone of a knot~n biaxial draw blow molding machine, the preform was heated at 115C
for 30 seconds and was then biaxially dratr-blow~molded to obtain a biaxially drawn polyethylene terephthalate bot-tle " K " having the outer surface coated with the same vinylidene chloride resin as used in Example 3 ( the average t.hickness of the~coating layer was 1.6 ~ ).
Tne outer surface of the above~mentioned preform was A-p-coated with -the above-merltioned vinylidene chloride res:in emulsion, and the coated preform was dried at 80C for 90 seconds in a perfect oven ( explosion-proof t~pe ). Then, the cQated preform was heated under the a~o~e-men~ioned heating conditions and t~l.as biaxially draw ~low-molded to ob~ain a biaxially drawn pol~ethylene terephthalate bo-ttle li L " having the outer surface coated with the above-mentioned vinylidene chloride -- ~0 ~

resin ( the average thickness of the coating layer was 1.5 ~
The crystalli~ation degree, freeze peeling de~ree, low te.~lperature adhesion strength ( fa~.ling strength ), scratch resistance.( pencil har~ness ), hot water resistance, chemical resis-tance and ~as barrier property ( oxygen permeation rate ) of each of the bottles K and were determi~ed according to the above~men-tioned methods~
The obtained results are shown in Table 6.
Table 6 Bottle K L
Crystallization Degree 1.36 1,37 Freeze Peeling Degree (~) 0 0 Falling Strength 0 0 Pencil Hardness 4H ~
Hot Water Resistance 0 0 Chemical Resistance 0092 Oog2 Q2 (cc/m2~day~atm) 6.5 6,4 From the resul-ts shown i.n Table 6, it is seen that even when the drying of the coated vinylidene chloride resin emulsion ~nd the heat treatment are subsequently carried out at the heating step of the biaxial draw blow molding process, the degree o~ crystal-lization comparable to the degree of crystallization o~tainable when the drying of the coated vinylidene chloride resin emulsion is carried out in advance and the heat treatment is independently effected at the heat~
ing step can be obtained, and therefore~ the freeze peel ~ ~1 ~

~8~

strength, low tem~erature adhesion strength ( falling strength ), scratch resistance ( pencil hardness ), hot wat2r resistance, chemical resistance and ~as barri2r property ( oxygen permeation rate ) can similarly be improved.
Example 7 Jus-t af-ter an a~orphous polyethylene terephthalate sheet having a thickness of 0.5 mm was prepared by extru~
sion, the sheet was dip~coated with the same vinylidene chloride resin latex as described in Example 1. Also the cooling effect was attained by the coating operation.
The coated sheet was dried. Then, the sheet was heated at 110C for 15 seconds and subjected to air pressure forming to obtain a square wide~rnouth bottle ( cup ) " M " having a length of 9.7 cm, a width of 9.7 crn, a height of 3,2 cm and an average thickness of 0.30 rnm, the inner and outer surfaces of which were co~ted wi-th the vinylidene ohloride resin. The average coated amounL
( average thickness ) of the vinylidene chloride resin coated on both the surf~ces of the bottle was 25 ~ he total amount on both the surfaces ), Separately, the above-mentioned polyethylene tere-phthalate sheet was first cooled to room ternperature and ~as then dip-coated wi-th the abo~e-mentio~ed vinylidene chloride resin latex~ The coated sheet was dried at 70C
for 2 minutes in an air-circulatin~ oven and subjected to air pressure for~ing under the same heating and mold rg conditions as described above to obtain a similar sq~are ~ 32 -~38~96~

wide~mouth bottle ( cup ) " N " in which tlle average coated aLlount was 20 ~ ( the total amount on both the surfaces ).
An uncoated bottle obtained under the same moldjng conditions as described above was dip-coated with the above~mentioned vinylidene chloride resin latex and ~as dried at 70C for 2 rninutes in an air-circula-ting oven.
The resulting bottle which had not been heat-treated is designated as " bottle 0 ll. The average coated amo-mt was 20 ~ ( ffhe total amOunt on both the surfaces ).
The crystallization degree, freeze peeling degree, low tenlperature a~hesion streng~h ( falling strength ), scratch resistance ( pencil hardness ), hot water resis-tance, chemical resistance and oxygen permea-tion rate of each of the bottles M, N 2nd 0 were deterrnined according to the above-mentioned results. The obtained results are shown in Table 70 Table 7 Bottle , M N 0 _ Crystallization ~egree 1002 1.01 0.47 Freeze Peeling ~egree ~%) 0 0 10 Falling Strength O O X
Pencil`Hardness 4H 4H 2H
Hot Water Resistænce 0 0 X
Chemical Resistance 0,91 0.90 0 4Q
Q0~ (cc/m2.day.a-tm) 2~3 ~.5 3 9 From the results sho.m in Table 7, i-t is seen that 6~L

by the heat treat!lent effec-t attained at the heating s-tep of the air pre.~sllre forming process, the degree of c:rystal-l.ization of the vinylidene chloride resin is increased, resulting in irLpro-iements of the freeze peel s-treng~h, low te~peratuIe adhesion, scratch resistance, hot water resistance and chemical resistance.

ComDarative Exalr!Dle 1 The crystallization degree ( lowest film~orming temperature 3 of the vlnylidene chloride resin latex ~n~rcose.~(r/se~f.) ~-described in Exa~lple 1 was inc-c~scd in advance, and in the same manner as described in Example 1, the resin latex was coated on an anchoring agent~coated isctactic polypropylene sheet as described in Example 1 and the coated sheet was dried The average coated arnount ~ aver-age thickness ) of the vinylidene chloride resin coatedon the surface of the shee-t was 10 ~ as in Example 1.
Under the same conditions as described in Example 1, the coated sheet was subJected to plug assist vacuurn forming so that the coated sur~ace was formed into the inner sur-face b obtain a square wide-mouth bottle " A"' similar to the bottle obtained in Example 1 The crystallization degree, freeze peeling degree, low ~ernperature a~hesion strength ( falling strength ~, scratch resistance ( pencil hardness ), hot water resis tance, chemical resistance and gas barrier property ( oxygen per~.eat on rate ) of the bottle A' ~ere deter-mined according to the above~mentioned methods, The obtained results are shown in Table 8.

8~

Table 8 Bottle ~ A' Crystallizati Oll ~egree 1.04 Fr~eze Peeling Degree (%) 81 Falling Strength X
Pencil Hardness B
Hot ~'ater Resistance X
Q2 (cc/m oday~atm) 107 When the results shown in Table 8 are compared with the results of the bottle A shown in Table 1, it is seen that although the degree of crystallization of the bot-tle A' is hi~her than that of the bottle A, the bottle A' is apparently inferior to the bottle A in the freeze ; peel strength? low terrlperature adhesion strength, scratch re~istance~ hot water strength and gas barrier property.
Accordingly, it will readily be understood that in o~er to improve the properties, it is necessary to increa_e the degree of crystalli~ation of the vinylidene chlorlde by giving a heat history while a bo~tle is being ~ormed, Comparative Example 2 l~hen -the isotactic polypropylene sheet coated with the vinylidene chloride resin latex was sub~ected to plug assist vacuum forming in Example l, the heating conditions were ch~lged to 150 C ~nd 2 minutes The obtained square ; wid~-mouth bottle ( cup ) sinilar to the bottle obtained in Example 1 is designated as " bottle P "0 ~ 35 -~.~8~

The crys-talliz2tion degree, freeze peeling de~ree, low temperature adhesion strength ( falling .strength ), scratch resistance ( pencil ha~dness ~, hot ~ater resis-tance, chemical resistance and oxygen per~leation rate o the bo-ttle P were determined according to the above~
mentioned methods, ~rhe obtained results are sho~n in Tabl~ 9, Table 9 Bottle P _ Crystallization Degree 0.86 Freeze Peeling ~egree (~) 10 Falling Strength X
Pencil Hardness H
Hot Water Resistance X
Chem.ical Resistance 0.53 Q2 (cc/m2-day-atm) 28 1,~en the results sho-wn in Table 9 are compared with -the results sho~n in Ta,ble 1, it is seen that if the heat treatment conditions are outside the range defined by the formula (2), the intended improvemen-ts cannot be a-ttained.

,1

Claims (4)

What Is Claimed Is

1. A process for the preparation of a coated oriented plastic container, which comprises coating an aqueous latex or organic solvent solution of a vinylidene chloride copolymer on at least one surface of a parison, preform or sheet for formation of container, which is formed by hot molding of a molecularly orientable thermo-plastic resin, drying the coated parison, preform or sheet to form a coating layer, and subjecting the formed coated structure to draw molding such as biaxial draw blow molding or draw forming, wherein the coating layer of the vinylidene chloride copolymer is crystallized at the step of forming the coating layer or the draw molding step.

2. A process according to claim 1, wherein the coating of the vinylidene chlorlde copolymer is crystallized so that the degree of crystallization is at least 0.5 as measured according to the infrared absorption spectrum method.

3. A process according to claim 1, wherein the formed coating is heat-treated so that the following requirements are satisfied, thereby to effect crystalli-zation:
wherein T stands for the temperature (°K) for the heat treatment of the coating layer, t stands for the the (seconds) of the heat treatment conducted at T°K, and k is a constant determined according to the kind of the vinylidene chloride copolymer, which is ordinarily in the range of 5 ? k ? 0.5.

4. A process according to claim 1, wherein while the parison, preform or sheet formed by hot molding is still hot, the aqueous latex or organic solvent solution of the vinylidene chloride copolymer is coated and drying of the coating layer is performed simultaneously with cooling of the parison, preform or sheet.