Process for preparation of coated oriented plastic container

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 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 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.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to a process for the preparation 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 improved by crystallizing a coating layer of a 
vinylidene chloride copolymer formed on a plastic container substrate. 
(2) Description of the Prior Art 
Plastic bottles prepared by melt-extruding and hollow-molding 
(blow-molding) thermoplastic plastics such as polyolefins are used in 
various fields instead of glass bottles because the plastic bottles have a 
lighter weight and a better shock resistance than the glass bottles. 
General-purpose plastics such as polyolefins are excellent in the moisture 
resistance and sanitary characteristics, but the oxygen permeability 
coefficient is relatively high and in bottles of these plastics, 
permeation of oxygen through bottle walls is not negligible. Accordingly, 
bottles of general-purpose plastics are not suitable as vessels for 
preserving foods for a long time or as vessels for cosmetics and the like 
where a high flavor-retaining property is required. 
As a means to overcome this defect, there have been developed and proposed 
plastic containers having a wall structure excellent in the oxygen barrier 
property. Among melt-extrudable thermoplastic resins which are now 
available, a saponified ethylene/vinyl acetate copolymer (ethylene/vinyl 
alcohol copolymer) is most excellent in the oxygen barrier property. 
However, this saponified copolymer is inferior in the moisture resistance, 
that is, the steam barrier property, and in this saponified copolymer, the 
oxygen permeability coefficient tends to increase as increase of the 
humidity. Accordingly, when this saponified copolymer is actually used for 
formation of plastic container, it is necessary to adopt a troublesome 
molding method in which this saponified copolymer is sandwiched by 
moisture-resistant resins such as polyolefins and the resulting laminate 
is fed to the molding step to form a multi-layer laminate container. 
SUMMARY OF THE INVENTION 
To our surprise, it was found that when a vinylidene chloride copolymer is 
coated in the form of an aqueous latex or organic solvent solution on the 
surface of a parison preform or sheet for a plastic container formed by 
hot molding and this coating layer is crystallized, the adhesion of the 
coating layer to the plastic container substrate is highly improved. 
It is therefore a primary object of the present invention to provide a 
process for the preparation of a coated oriented plastic container in 
which the adhesion of a coating layer of a vinylidene chloride copolymer 
to a molecularly oriented plastic container substrate is highly improved. 
Another object of the present invention is to provide a process for the 
preparation of a coated oriented plastic container in which peeling of a 
coating layer is prevented even under such severe conditions that the 
content in the container is frozen or when the container undergoes such an 
extreme deformation as will crush the bottle at low temperatures. 
Still another object of the present invention is to provide a process for 
the preparation of a coated oriented plastic container in which not only 
the adhesion of a coating layer of a vinylidene chloride copolymer but 
also the gas barrier property, strength and chemical resistance are highly 
improved. 
More specifically, in accordance with the present invention, 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 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.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1 illustrating an embodiment of the coated plastic bottle 
of the present invention, this bottle 1 comprises a peripheral wall 2 
having a circular or ellipsoidal section, a mouth portion 3 connected 
integrally to the peripheral wall 2 and a bottom portion 4 connected to 
the lower end of the peripheral wall 2. All of these bottle walls comprise 
a plastic bottle substrate 5 formed from a melt-moldable thermoplastic 
resin by biaxially drawing blow molding or draw forming, and a coating 
layer 6 of a vinylidene chloride copolymer formed on the surface of the 
substrate 5. The coating layer 6 may be formed on both the surfaces of the 
bottle substrate 5 as shown in FIG. 1 or it may be formed only on the 
inner or outer surface of the bottle substrate 5. 
It is known that a vinylidene chloride copolymer is a resin excellent in 
the oxygen barrier property. However, hot molding of this vinylidene 
chloride copolymer is difficult, and the copolymer should be handled in 
the form of an aqueous latex or organic solvent solution. 
The critical feature of the present invention resides in the finding that, 
as pointed out hereinbefore, when a vinylidene chloride copolymer is 
coated in the form of an aqueous latex or organic solvent solution on the 
surface of a plastic parison, preform or sheet formed by hot molding in 
advance and the coated structure is subjected to draw molding to form a 
composite plastic container, if the coating layer of the vinylidene 
chloride copolymer is crystallized at the step of forming the coating 
layer or the draw molding step, the adhesion of the coating layer to the 
plastic substrate is highly improved. 
In a coated plastic container formed by ordinarily coating a vinylidene 
chloride copolymer and drying the coating layer, the adhesion of the 
coating layer to the substrate seems good. 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 
coating layer of the vinylidene chloride copolymer is readily peeled from 
the container substrate. This phenomenon is similarly observed when a 
parison or the like provided with a coating layer of a vinylidene chloride 
copolymer is subjected to draw molding. 
In the present invention, by positively crystallizing the vinylidene 
chloride copolymer constituting the coating 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 draw molding step, the adhesion of the coating 
layer to the plastic bottle substrate is improved to such an extent that 
under the above-mentioned severe conditions, peeling is not substantially 
caused. This finding is quite unexpected from the common sense in the art 
of coating. More specifically, it has been considered that when a 
crystallizable thermoplastic resin is used as a coating layer, from the 
viewpoint of the adhesion of the coating layer, it is important that the 
resin should not be crystallized. Accordingly, in the conventional 
methods, there have been adopted rapid cooling means for passing the 
coating layer rapidly through the crystallization temperature range. In 
contrast, in the present invention, a parison or the like to be subjected 
to draw molding is coated with a vinylidene chloride copolymer and the 
coating layer is crystallized by a heat treatment at the coating-forming 
step or draw molding step, whereby the adhesion of the coating layer to a 
molecularly oriented plastic container formed by draw molding is 
prominently improved with this crystallization. This fact will become 
apparent from examples given hereinafter. 
In order to attain the objects of the present invention, it is preferred 
that the coating layer of the vinylidene chloride copolymer be 
crystallized so that the degree of crystallization of the coating layer of 
the vinylidene chloride copolymer is at least 0.5, especially at least 
0.8, as determined according to the infrared absorption spectrum method 
described hereinafter. 
According to the present invention, by crystallizing the vinylidene 
chloride copolymer constituting the coating layer, the barrier properties 
to gases such as oxygen, carbon dioxide gas and steam can prominently be 
improved, and mechanical properties such as the tensile strength, impact 
resistance and abrasion resistance, the chemical resistance such as the 
alkali resistance and the hot water resistance such as the resistance to 
whitening by hot water can also be improved prominently. Therefore, a 
coated container excellent in various properties can be obtained according 
to the present invention. 
The parison, preform or sheet that is used in the present invention 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-mentioned resin 
in the form of a pipe and cutting the pipe. Furthermore, a bottomed 
parison for biaxial draw blow molding can be obtained by extruding the 
resin in the cylindrical form, pinching off the extrudate by a split mold 
and subjecting the extrudate to preliminary blow molding. Moreover, a 
bottomed parison for biaxial draw blow molding can be obtained by 
injection-molding the above-mentioned resin. Still further, a sheet for 
draw forming of a wide-mouth container can be obtained 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 of the parison, there 
can be mentioned olefin resins such as isotactic polypropylene, 
crystalline propylene/ethylene copolymers, crystalline propylene/butane-1 
copolymers, crystalline propylene/butene-1/ethylene copolymers and 
ethylene/vinyl alcohol copolymers, polyesters such as polyethylene 
terephthalate, polybutylene terephthalate and polyethylene 
terephthalate/isophthalate, polyamides such as nylon 6, nylon 6,6 and 
nylon 6,10, polystyrene, styrene type copolymers such as styrene/butadiene 
block copolymers, styrene/acrylonitrile copolymers, 
styrene/butadiene/acrylonitrile copolymers (ABS resins), polyvinyl 
chloride, vinyl chloride type copolymers such as vinyl chloride/vinyl 
acetate copolymers, polymethyl methacrylate and acrylic copolymers such as 
methyl methacrylate/ethyl acrylate copolymers, and polycarbonate, though 
usable resins are not limited to those exemplified above. These 
thermoplastic resins may be used singly or in the form of a blend of two 
or more of them. The plastic parison or the like may have a single layer 
structure or a multi-layer laminate structure formed, for example, 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 
parison or the like. 
As the vinylidene chloride copolymer, there is used a copolymer comprising 
vinylidene chloride as the main constituent monomer and at least one 
comonomer selected from an acrylic or methacrylic monomer, a vinyl 
aromatic monomer such as styrene or vinyl toluene, a vinyl ester such as 
vinyl acetate or vinyl propionate, a diolefin such as butadiene or 
isoprene, and methyl vinyl ether, glycidyl allyl ether, vinyl chloride, 
trichloroethylene, tetrachloroethylene, vinyl fluoride, vinylidene 
fluoride, trifluoroethylene, tetrafluoroethylene, maleic anhydride, 
fumaric acid, vinyl succinimide and vinylpyrrolidone. As suitable examples 
of the acrylic or methacrylic monomer, there can be mentioned acrylic 
acid, acrylonitrile, acrylamide, methyl acrylate, ethyl acrylate, methyl 
.alpha.-chloroacrylate, propyl acrylate, butyl acrylate, hexyl acrylate, 
octyl acrylate, cyclohexyl acrylate, glycidyl acrylate, 2-hydroxyethyl 
acrylate, acrylic acid monoglyceride, phenyl acrylate, methacrylic acid, 
methacrylonitrile, methacrylamide, methyl methacrylate, amyl methacrylate, 
glycidyl methacrylate, methacrylic acid monoglyceride, 2-hydroxypropyl 
methacrylate, .beta.-methoxyethyl methacrylate, .beta.-aminoethyl 
methacrylate and .gamma.-N,N-diethylaminopropyl methacrylate. 
An aqueous latex of the vinylidene chloride copolymer having a solid 
concentration of 20 to 65% and a viscosity of 3 to 500 centipoises is 
preferably used in the present invention. 
A solution having a solid content of 5 to 60% in an organic solvent such as 
toluene, tetrahydrofuran, ethyl acetate, methylethyl ketone, cyclohexane, 
dimethylformamide, dimethylsulfoxide or dioxane is used as the organic 
solvent solution. 
Coating of the plastic container subtrate with the above-mentioned 
copolymer latex or solution may be accomplished by adopting at least one 
of known coating methods such as dip coating, spray coating, brush 
coating, roller coating, electrostatic coating, centrifugal coating, cast 
coating and electrophoretic coating methods. The coating operation may be 
conducted only once or a multiple stage coating method may be adopted. If 
desired, the plastic container substrate such as a parison may be 
subjected to a wetting property-improving preliminary treatment such as a 
pretreatment with an anchoring agent, a corona discharge treatment, a 
surface 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 conducting treatment. 
In the present invention, it is preferred that the coating layer of the 
above-mentioned copolymer be formed on both the surfaces of the plastic 
container substrate. However, in order to shut gases contained in air, the 
coating layer may be formed on the outer surface alone, and in order to 
prevent escape of a gas or perfume from the content of the bottle, the 
coating layer may be formed on the inner surface alone. 
As pointed out hereinbefore, the vinylidene chloride copolymer that is used 
in the present invention is excellent in the combination of the oxygen 
barrier property and water vapor barrier property and the humidity 
dependency of the oxygen barrier property is very low. Accordingly, when 
the copolymer is formed on the plastic container substrate in the form of 
a very thin layer, excellent barrier properties to various gases can be 
obtained. More specifically, satisfactory results can oridinarily be 
obtained if the copolymer is formed in a layer on the container having a 
thickness of 0.5 to 40.mu., especially 1 to 30.mu.. 
The conditions adopted for drying the coated copolymer layer are changed 
according to the thickness of the coating layer, but ordinarily, a 
sufficient drying effect can be attained when drying is carried out at a 
temperature of 40.degree. to 150.degree. C. for about 2 seconds to about 
100 hours. 
In the present invention, if the aqueous latex or organic solvent solution 
of the vinylidene chloride copolymer is coated on a parison, preform or 
sheet formed by hot molding while the parison, preform or sheet is still 
hot, drying of the coating is accomplished by utilizing heat possessed by 
the parison or the like simultaneously with cooling of the parison or the 
like. Accordingly, this method is advantageous. 
Draw molding of the parison, preform or sheet coated with the vinylidene 
chloride copolymer can be carried out under known conditions. More 
specifically, biaxial draw blow molding or draw forming such as air 
pressure forming or plug assist forming is carried out under such 
conditions as causing molecular orientation by drawing. 
In case of biaxial draw blow molding, the parison or preform is 
mechanically drawn in the axial direction in a split mold, and 
simultaneously, a fluid is blown into the parison or preform to expand and 
draw the parison or preform in the circumferential direction. In case of a 
bottomed parison or preform, drawing in the axial direction may be 
accomplished by pushing a drawing rod into the bottomed parison or 
preform, and in case of a tube, drawing in the axial direction may be 
accomplished by holding both the ends of the tube by a clamping mechanism 
or passing the tube between two rolls differing in the rotation speed. It 
is preferred that draw blow molding be carried out so that the in-plane 
orientation coefficient (l+m) of the barrel portion of the formed 
container is 0.05 to 1.0, especially 0.1 to 0.9. For this purpose, it is 
preferred that the draw ratio in the axial direction be 1.10 to 20, 
especially 1.20 to 15, and that the draw ratio in the circumferential 
direction be 1.20 to 50, especially 1.25 to 30. 
In draw forming of a wide-mouth container, the draw forming operation is 
carried out under temperature conditions causing molecular orientation by 
air pressure forming or plug assist forming so that the draw ratio defined 
by the following formula is 1.10 to 100, especially 1.20 to 50: 
##EQU1## 
According to the present invention, the coating layer on the plastic 
substrate is maintained at the crystallization temperature of the 
vinylidene chloride copolymer at the coating layer-forming step or draw 
molding step, whereby crystallization of the copolymer is accomplished. 
When it is intended to effect crystallization at the coating-forming step, 
the above-mentioned heat treatment is carried out simultaneously with or 
subsequently to the drying of the coating layer. In this case, it is 
necessary that the coating layer should be maintained at the 
crystallization temperature in the substantial absence of water or an 
organic solvent, because formation of a film of the vinylidene chloride 
copolymer is not substantially advanced in the presence of water or an 
organic solvent. 
When it is intended to effect crystallization of the coating layer at the 
draw molding step, the heat treatment of heating the coated parison or 
preform at the drawing temperature and the temperature and time for the 
draw molding operation can be utilized for crystallization of the coating 
layer. This crystallization treatment is especially effective when the 
draw molding temperature of the plastic substrate is relatively high. 
The degree of crystallization of the vinylidene chloride copolymer depends 
on both the temperature and time of the crystallization treatment. 
Furthermore, there is a fear of thermal deterioration of the vinylidene 
chloride copolymer due to the heat treatment for crystallization. 
In the present invention, the heat treatment of the coating layer is 
carried out so that the following requirements are satisfied: 
##EQU2## 
wherein T stands for the temperature (.degree.K.) for the heat treatment 
of the coating layer, t stands for the time (seconds) of the heat 
treatment conducted at T.degree.K., and k is a constant determined 
according to the kind of the vinylidene chloride copolymer, which is 
ordinarily in the range of 5.ltoreq.k.ltoreq.0.5. 
If the temperature-time integration value is too small and is below the 
above range, the crystallization is not sufficient and it is difficult to 
increase the adhesion to a satisfactory level. If this value is too large 
and exceeds the above range, the coating layer of the vinylidene chloride 
copolymer is thermally deteriorated and physical properties are rather 
degraded. 
In the present invention, it is preferred that after the heat treatment, 
the coating layer be rapidly cooled so that the time-temperature 
integration value of the heat treatment conditions is not outside the 
above-mentioned range. In the case where the final heat treatment is draw 
molding, it is preferred that the plastic container formed by draw molding 
be rapidly cooled. 
In order to protect the above-mentioned coating layer and improve the 
weatherability, scratch resistance and gas barrier property thereof, a 
protecting layer composed of a film-forming synthetic resin, other than 
the vinylidene chloride copolymer, may be formed adjacent to the coating 
layer according to the known and 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 resistance 
(pencil hardness), chemical resistance, hot water resistance (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 Handbook" (compiled by Editional Conference 
of Emulsion Latex Handbook and published by Daisensha). More specifically, 
the side wall portion was cut out from a coated container and the 
absorption spectrum of the coated surface was determined according to the 
total reflection method, transmission method or differential spectrum 
method using an infrared spectrophotometer (Model A-3 supplied by Nippon 
Bunko Kogyo). Among absorption bands characteristic of vinylidene 
chloride, which appear at 743, 875, 1046 and 1071 cm.sup.-1, the 
absorption bands at 1046 and 1071 cm.sup.-1 are considered to indicate the 
degree of crystallization. Accordingly, the ratio of the absorbances at 
1046 and 1071 cm.sup.-1 was designated as the crystallization degree. From 
the results of the X-ray diffractometry, it is proved that increase of the 
above-mentioned absorbance ratio means advance of crystallization in the 
internal structure of polyvinylidene chloride. Examples of the results of 
the measurement of the absorption spectrum and absorbances are shown in 
FIG. 2. Incidentally, FIG. 2 shows the results obtained with respect to a 
sample formed by coating a vinylidene chloride latex on a polyethylene 
film. The absorption bands at 720, 1350, 1425 and 2900 cm.sup.-1 are those 
characteristic of polyethylene. 
(2) Freeze Peeling Degree 
A coated container, the weight of which had been measured in advance, was 
filled with distilled water, and water was frozen and expanded at 
-15.degree. C. The coating which was observed to have been peeled was 
removed from the container, and the weight of the empty container was then 
measured. The peeling degree (%) was calculated by dividing the difference 
between the weight of said container and the weight of the container 
before the freezing by the total amount of the coating according to the 
following formula: 
##EQU3## 
(3) Low Temperature Adhesion Strength (falling strength) 
A coated container was filled with an aqueous solution of sodium chloride 
(the sodium chloride concentration was 10% by weight) maintained at 
-1.degree. C., and the container was plugged and was let to fall down on 
the concrete surface from a height of 1.5 m so that the side face of the 
container impinged against the concrete surface. For each coating 
condition, five sample containers were tested. Then, in order to determine 
whether or not micro-cracks were formed, the side wall portion of the 
container subjected to the falling test was cut out and was dyed at 
50.degree. C. for 5 minutes in a dyeing aqueous solution of Malachite 
Green, and the side wall portion was observed by a microscope (100 
magnifications). 
The falling strength was evaluated according to the following scale: 
O: no cracks were formed in any of the five samples. 
.DELTA.: cracks were formed in 1 to 4 samples. 
X: cracks were formed in all of the five samples. 
(4) Scratch Resistance (pencil hardness) 
Under conditions of a temperature of 20.degree. C. and a relative humidity 
of 40%, a weight of 0.5 Kg was placed on each of pencils having a hardness 
in the range of from 6B to 6H, and lines having a length of about 2 cm 
were drawn on the coated surface of a barrel portion cut out from a sample 
container. Then, pencil dusts left on the surfaces were swept away, and 
the surface of the sample container was examined by a magnifying glass of 
10 magnifications and the scratch resistance was evaluated based on the 
hardness of the pencil which left a scratch on the surface. Accordingly, 
the pencil hardness 6B indicates the lowest scratch resistance, and the 
scratch resistance is increased in the order of 5B, 4B, 3B, 2B, B, HB, F, 
H, 2H, 3H, 4H and 5H and the pencil hardness 6H indicates the highest 
scratch resistance. 
(5) Hot Water Resistance 
A square sample of about 3 cm.times.about 3 cm was cut out from the barrel 
wall of the coated container and was boiled on a thermostat hot water tank 
maintained at 95.degree. C. for 30 minutes. Then, the sample was taken out 
from the tank and the whitening state was visually examined by a panel of 
five experts. Symbols shown in the following examples have the following 
meanings: 
O: five or four experts on the panel judged that whitening did not occur. 
.DELTA.: two or three of the fine experts judged that whitening did not 
occur. 
X: one or none of the fine experts judged that whitening did not occur. 
(6) Chemical Resistance 
The side wall portion of the coated container was cut out and immersed in 
an aqueous solution containing 10% by weight of caustic soda at 25.degree. 
C. overnight. Before this immersion treatment, the total transmission of 
rays having a visible range wavelength of 400 m.mu. was measured with 
respect to the sample by using an integrating ball in a self-recording 
spectrophotometer (supplied by Hitachi), and the total transmission was 
similarly measured after the treatment with the aqueous solution of 
caustic soda. The chemical resistance was evaluated based on the 
deterioration degree expressed by the ratio Tafter/Tbefore, in which 
Tbefore represents the total transmission of the sample before the caustic 
soda treatment and Tafter represents the total transmission of the sample 
after the caustic soda treatment. A smaller value of the deterioration 
degree means a larger deterioration. 
(7) Gas Barrier Property 
As the gas barrier property, the oxygen permeation rate (QO.sub.2) at a 
temperature of 20.degree. C. and a relative humidity of 0% was measured 
according to the following procedures. 
A barrel wall of a container to be measured was cut into a predetermined 
size and an obtained sheet-like sample was used for the measurement. A gas 
permeation tester manufactured by Toyo Tester Kogyo K.K. was used for the 
measurement. The sample was fixed between two chambers of this tester, and 
suction was effectd in one chamber so that the pressure was reduced below 
10.sup.-2 mmHg (low pressure side) while in the other chamber (high 
pressure side), the atmosphere was replaced by dehumidified oxygen gas so 
that the oxygen gas pressure was one atmosphere. The change of the 
pressure increase with the lapse of time was read on a recorder and the 
oxygen gas permeation rate QO.sub.2 was determined from the read values. 
The measurement was carried out at 20.degree. C. 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 polypropylene sheet having a 
width of 30 cm and a thickness of 0.8 mm the coating was heated for drying 
at 80.degree. C. for 90 seconds. Then, a polyvinylidene chloride latex 
having a composition comprising 86% by weight of vinylidene chloride, 5% 
by weight of acrylonitrile, 3% by weight of methyl acrylate and 6% by 
weight of glycidyl methacrylate (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.mu.. Then, the sheet was subjected to plug assist vacuum 
forming at 135.degree. C. so that the coated surface was formed into the 
inner surface, 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 0.47 mm. The heating time was 30 seconds. The inner surface 
of a square wide-mouth bottle of isotactic polypropylene formed from an 
uncoated sheet under the same forming conditions as described above was 
coated with the above-mentioned anchoring agent and then spray-coated with 
the above-mentioned polyvinylidene chloride latex, and the coated bottle 
was dried at 80.degree. C. for 2 minutes. The average amount coated of the 
vinylidene chloride resin (average thickness) was 8.mu.. The obtained 
bottle is designated as "bottle B". 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistance (pencil hardness), hot 
water resistance, chemical resistance and oxygen permeation rate of each 
of the bottles A and B were measured according to the above-mentioned 
methods. The obtained results are shown in Table 1. 
TABLE 1 
______________________________________ 
Bottle A B 
______________________________________ 
Crystallization Degree 
1.02 0.47 
Freeze Peeling Degree (%) 
0 8 
Falling Strength .circle. 
X 
Pencil Hardness 4H 2H 
Hot Water Resistance .circle. 
X 
Chemical Resistance 0.90 0.37 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. 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 of crystallization of 
the vinylidene chloride resin is increased, resulting in improvements of 
the freeze peeling strength, low temperature adhesion strength (falling 
strength), scratch resistance (pencil hardness), hot water resistance, 
chemical resistance and gas barrier property. 
EXAMPLE 2 
The non-heat-treated, vinylidene chloride resin-coated bottle B described 
in Example 1 was heat-treated under the heating conditions for the plug 
assist vacuum forming, described in Example 1. The obtained bottle is 
designated at "bottle C". 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistance (pencil hardness), hot 
water resistance, chemical resistance and oxygen permeation rate of the 
bottle C were determined according to the above-mentioned methods. The 
obtained results are shown in Table 2. 
TABLE 2 
______________________________________ 
Bottle C 
______________________________________ 
Crystallization Degree 
0.95 
Freeze Peeling Degree (%) 
0 
Falling Strength .circle. 
Pencil Hardness 4H 
Hot Water Resistance .circle. 
Chemical Resistance 0.87 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
22 
______________________________________ 
When the results shown in Table 2 are compared with the results shown in 
table 1, it will readily be understood 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, pencil 
hardness, not water resistance, chemical resistance and oxygen barrier 
property. 
EXAMPLE 3 
The inner surface of a preform (bottomed parison) of amorphous polyethylene 
terephthalate having an outer surface area of 130 cm.sup.2, a weight of 63 
g and an average thickness of 3.6 mm was dip-coated (slush-coated) with a 
polyvinylidene chloride resin emulsion having a composition comprising 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 hot air maintained at 100.degree. C. for 1 minute. 
The amount coated of the vinylidene chloride resin was 0.23 g. The preform 
was heated at 120.degree. C. for 25 seconds and biaxially draw-blow-molded 
by using a known biaxial draw blow molding machine to obtain 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 average 
thickness of the coating layer was 1.5.mu.). 
The uncoated preform was biaxially draw-blow-molded under the 
above-mentioned conditions and the resulting biaxially drawn polyethylene 
terephthalate bottle was dip-coated (slush-coated) with the 
above-mentioned vinylidene chloride resin emulsion. The coated bottle was 
dried by blowing hot air maintained at 100.degree. C. for 2 minutes. The 
average coated amount (average thickness) of the vinylidene chloride resin 
was 3.mu.. This bottle 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 (pencil 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 .circle. X .circle. 
Pencil Hardness 4H 2H 4H 
Hot Water Resistance 
.circle. X .circle. 
Chemical Resistance 
0.93 0.61 0.91 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
6.3 6.8 6.4 
______________________________________ 
From the results shown in Table 3, it will readily be understood that the 
heat treatment effect 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 
therefore, 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 resin is oriented by biaxial draw blow 
molding. 
EXAMPLE 4 
The outer surface of an amorphous polyethylene terephthalate preform as 
described in Example 3 was spray-coated with a vinylidene chloride 
copolymer solution having a composition comprising 90% by weight of 
vinylidene chloride, 5% by weight of acrylonitrile and 5% by weight of 
glycidyl acrylate (solvent=65% of tetrahydrofuran and 35% of toluene; 
solid concentration=20%) in the state where the preform was still hot (the 
surface temperature was 80.degree. C.) just after injection molding. Then, 
the coated preform was heated at 100.degree. 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 polyvinylidene 
chloride resin (the average thickness of the coating layer was 2.0.mu.). 
When the above-mentioned preform prepared by injection molding was cooled 
to room temerature, the preform was spray-coated with the above-mentioned 
vinylidene chlorde copolymer solution, and the coated preform was dried at 
80.degree. C. for 90 seconds in an air circulating oven and was then 
biaxially draw-blow-molded under the same conditions as described above to 
obtain a biaxially drawn polyethylene terephthalate bottle "H" having a 
coating layer thickness of 1.8.mu.. 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistane (pencil hardness), hot 
water resistance, chemical strength and oxygen permeation rate of each of 
the bottles G and H were determined according to the above-mentioned 
methods. The obtained results are shown in Table 4. 
TABLE 4 
______________________________________ 
Bottle G H 
______________________________________ 
Crystallization Degree 
1.32 1.10 
Freeze Peeling Degree (%) 
0 10 
Falling Strength .circle. 
.DELTA. 
Pencil Hardness 4H 2H 
Hot Water Resistance .circle. 
X 
Chemical Resistance 0.93 0.76 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
6.1 7.3 
______________________________________ 
From the results shown in Table 4, it is seen that the degree of 
crystallization of the bottle G is higher than that of the bottle H and 
the bottle G is excellent over the bottle H in the freeze peel stength, 
falling strength, pencil hardness, hot water resistance and gas barrier 
property. It is considered that the reason is that since the preform which 
has not been cooled is coated, the heat treatment effect is attained at 
the step of heating the coating layer. 
EXAMPLE 5 
A pipe having a three-layer structure comprising an outer layer of 
isotactic polypropylene, an intermediate layer of an adhesive (maleic 
anhydride-modified polypropylene) and an inner layer of an ethylene/vinyl 
alcohol copolymer, in which the outer layer/intermediate layer/inner layer 
thickness ratio was 20:0.1:1, was formed by extrusion molding, and just 
after extrusion molding, the inner surface of the pipe was dip-coated with 
a polyvinylidene chloride latex having a composition comprising 90% by 
weight of vinylidene chloride, 5% by weight of methyl methacrylate and 5% 
by weight of methyl methacrylate (dispersion medium=water, solid 
concentration=50%). Also the cooling effect was attained by this coating 
operation. By using a known biaxial draw molding machine, the coated pipe 
was heated at 150.degree. C. for 5 minutes and biaxially draw-blow-molded 
to obtain a biaxially drawn laminated bottle "I" having an inner volume of 
500 cc and an average thickness of 500.mu., the inner surface of which was 
coated with the polyvinylidene chloride resin (the average thickness of 
the coating layer was 3.mu.). 
An uncoated three-layer pipe having the above-mentioned layer structure was 
biaxially draw-blow-molded in the same manner as described above, and the 
inner surface of the uncoated, biaxially drawn, laminated bottle was 
dip-coated (slush-coated) with the above-mentioned vinylidene chloride 
resin latex and the coated bottle was dried by blowing hot air maintained 
at 110.degree. C. into the bottle for 90 seconds. The so-obtained, 
biaxially drawn, laminated bottle having the inner surface coated with the 
vinylidene chloride resin (the average thickness of the coating layer was 
4.mu.) is designated as "bottle J". 
The crystallization degree, freeze peeling degree, low temperature adhesion 
(falling strength), scratch resistance (pencil hardness), chemical 
resistance and oxygen permeation rate of each of the bottles I and J were 
determined according to the above-mentioned methods. The obtained results 
are shown in Table 5. 
TABLE 5 
______________________________________ 
Bottle I J 
______________________________________ 
Crystallization Degree 
1.41 0.83 
Freeze Peeling Degree (%) 
0 30 
Falling Strength .circle. 
X 
Pencil Hardness 4H 2H 
Hot Water Resistance .circle. 
X 
Chemical Resistance 0.89 0.62 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
0.63 0.96 
______________________________________ 
From the results shown in Table 5, it will readily be understood that by 
the heat treatment effect attained at the molding step, the degree of 
crystallization of the vinylidene chloride resin is increased, resulting 
in improvements of the freeze peel strength, low temperature adhesion 
strength, scratch resistance, chemical resistance and gas barrier 
property. 
EXAMPLE 6 
The outer surface of a preform (bottomed parison) of amorphous polyethylene 
terephthalate as described in Example 3 was dip-coated with the same 
vinylidene chloride resin emulsion as used in Example 3. Just after the 
coating operation, in the state where the preform was not yet dried, in a 
heating zone of a known biaxial draw blow molding machine, the preform was 
heated at 115.degree. C. for 30 seconds and was then biaxially 
draw-blow-molded to obtain a biaxially drawn polyethylene terephthalate 
bottle "K" having the outer surface coated with the same vinylidene 
chloride resin as used in Example 3 (the average thickness of the coating 
layer was 1.6.mu.). 
The outer surface of the above-mentioned preform was dip-coated with the 
above-mentioned vinylidene chloride resin emulsion, and the coated preform 
was dried at 80.degree. C. for 90 seconds in a perfect oven 
(explosion-proof type). Then, the coated preform was heated under the 
above-mentioned heating conditions and was biaxially draw-blow-molded to 
obtain a biaxially drawn polyethylene terephthalate bottle "L" having the 
outer surface coated with the above-mentioned vinylidene chloride resin 
(the average thickness of the coating layer was 1.5.mu.). 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistance (pencil hardness), hot 
water resistance, chemical resistance and gas barrier property (oxygen 
permeation rate) of each of the bottles K and L were determined according 
to the above-mentioned 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 .circle. 
.circle. 
Pencil Hardness 4H 4H 
Hot Water Resistance .circle. 
.circle. 
Chemical Resistance 0.92 0.92 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
6.5 6.4 
______________________________________ 
From the results shown in Table 6, it is seen that even when the drying of 
the coated vinylidene chloride resin emulsion and the heat treatment are 
subsequently carried out at the heating step of the biaxial draw blow 
molding process, the degree of crystallization comparable to the degree of 
crystallization obtainable when the drying of the coated vinylidene 
chloride resin emulsion is carried out in advance and the heat treatment 
is independently effected at the heating step can be obtained, and 
therefore, the freeze peel strength, low temperature adhesion strength 
(falling strength), scratch resistance (pencil hardness), hot water 
resistance, chemical resistance and gas barrier property (oxygen 
permeation rate) can similarly be improved. 
EXAMPLE 7 
Just after an amorphous polyethylene terephthalate sheet having a thickness 
of 0.5 mm was prepared by extrusion, 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 110.degree. C for 15 minutes and 
subjected to air pressure forming to obtain a square wide-mouth bottle 
(cup) "M" having a length of 9.7 cm, a width of 9.7 cm, a height of 3.2 cm 
and an average thickness of 0.30 mm, the inner and outer surfaces of which 
were coated with the vinylidene chloride resin. The average coated amount 
(average thickness) of the vinylidene chloride resin coated on both the 
surfaces of the bottle was 25.mu. (the total amount on both the surfaces). 
Separately, the above-mentioned polyethylene terephthalate sheet was first 
cooled to room temperature and was then dip-coated with the 
above-mentioned vinylidene chloride resin latex. The coated sheet was 
dried at 70.degree. C. for 2 minutes in an air-circulating oven and 
subjected to air pressure forming under the same heating and molding 
conditions as described above to obtain a similar square wide-mouth bottle 
(cup) "N" in which the average coated amount was 20.mu. (the total amount 
on both the surfaces). 
An uncoated bottle obtained under the same molding conditions as described 
above was dip-coated with the above-mentioned vinylidene chloride resin 
latex and was dried at 70.degree. C. for 2 minutes in an air-circulating 
oven. The resulting bottle which had not been heat-treated is designated 
as "bottle O". The average coated amount was 20.mu. (the total amount on 
both the surfaces). 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistance (pencil hardness), hot 
water resistance, chemical resistance and oxygen permeation rate of each 
of the bottles M, N and O were determined according to the above-mentioned 
results. The obtained results are shown in Table 7. 
TABLE 7 
______________________________________ 
Bottle M N O 
______________________________________ 
Crystallization Degree 
1.02 1.01 0.47 
Freeze Peeling Degree (%) 
0 0 10 
Falling Strength .circle. .circle. 
X 
Pencil Hardness 4H 4H 2H 
Hot Water Resistance 
.circle. .circle. 
X 
Chemical Resistance 
0.91 0.90 0.40 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
2.3 3.5 3.9 
______________________________________ 
From the results shown in Table 7, it is seen that by the heat treatment 
effect attained at the heating step of the air pressure forming process, 
the degree of crystallization of the vinylidene chloride resin is 
increased, resulting in improvements of the freeze peel strength, low 
temperature adhesion, scratch resistance, hot water resistance and 
chemical resistance. 
COMATIVE EXAMPLE 1 
The crystallization degree (lowest film-forming temperature) of the 
vinylidene chloride resin latex described in Example 1 was increased 
(raised) in advance, and in the same manner as described in Example 1, the 
resin latex was coated on an anchoring agent-coated isotactic 
polypropylene sheet as described in Example 1 and the coated sheet was 
dried. The average coated amount (average thickness) of the vinylidene 
chloride resin coated on the surface of the sheet was 10.mu. as in Example 
1. Under the same conditions as described in Example 1, the coated sheet 
was subjected to plug assist vacuum forming so that the coated surface was 
formed into the inner surface to obtain a square wide-mouth bottle "A'" 
similar to the bottle obtained in Example 1. 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistance (pencil hardness), hot 
water resistance, chemical resistance and gas barrier property (oxygen 
permeation rate) of the bottle A' were determined according to the 
above-mentioned methods. The obtained results are shown in Table 8. 
TABLE 8 
______________________________________ 
Bottle A' 
______________________________________ 
Crystallization Degree 
1.04 
Freeze Peeling Degree (%) 
81 
Falling Strength X 
Pencil Hardness B 
Hot Water Resistance X 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. 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 bottle A' is higher than that of the bottle A, the 
bottle A' is apparently inferior to the bottle A in the freeze peel 
strength, low temperature adhesion strength, scratch resistance, hot water 
strength and gas barrier property. Accordingly, it will readily be 
understood that in order to improve the properties, it is necessary to 
increase the degree of crystallization of the vinylidene chloride by 
giving a heat history while a bottle is being formed. 
COMATIVE EXAMPLE 2 
When the isotactic polypropylene sheet coated with the vinylidene chloride 
resin latex was subjected to plug assist vacuum forming in Example 1, the 
heating conditions were changed to 150.degree. C. and 2 minutes. The 
obtained square wide-mouth bottle (cup) similar to the bottle obtained in 
Example 1 is designated as "bottle P". 
The crystallization degree, freeze peeling degree, low temperature adhesion 
strength (falling strength), scratch resistance (pencil hardness), hot 
water resistance, chemical resistance and oxygen permeation rate of the 
bottle P were determined according to the above-mentioned methods. The 
obtained results are shown in Table 9. 
TABLE 9 
______________________________________ 
Bottle P 
______________________________________ 
Crystallization Degree 
0.86 
Freeze Peeling Degree (%) 
10 
Falling Strength X 
Pencil Hardness H 
Hot Water Resistance X 
Chemical Resistance 0.53 
QO.sub.2 (cc/m.sup.2 .multidot. day .multidot. atm) 
28 
______________________________________ 
When the results shown in Table 9 are compared with the results shown in 
Table 1, it is seen that if the heat treatment conditions are outside the 
range defined by the formula (2), the intended improvements cannot be 
attained.