JPS63294342A - Injection-blow molding multilayer container - Google Patents

Abstract

PURPOSE:To enhance an appearance characteristic, by forming a body part into a multilayer structure consisting of inner and outer surface layers composed of thermoplastic polyester and an intermediate layer composed of a gas barrier thermoplastic resin and allowing the intermediate layer to be necessarily present at a container part where the coefficient of interfacial orientation degree of the inner and outer surface layers is a specific value or more but allowing said intermediate layer to be absent at a container part where said coefficient is the specific value or less. CONSTITUTION:Each of the wall thicknesses of a mouth part 1, a shoulder part 2 and a bottom part 4 is larger than that of a body 3. The body part 3 is composed of a multilayer structure consisting of inner and outer surface layers 5, 6 composed of thermoplastic polyester and an intermediate layer 7 composed of a gas barrier thermoplastic resin. The intermediate layer 7 is present at a container part where the coefficient of an interfacial orientation degree (l+m) of the inner and outer surface layers 5, 6 is 0.50 or more but absent at a container part where said coefficient is 0.35 or less. At the container part where the coefficient of interfacial orientation is 0.50 or more, the intermediate layer is made thin, and the generation of a vertical stripe and a yellowing or whitening tendency are eliminated to eliminate appearance inferiority. By providing no gas barrier resin intermediate layer at the container part where the coefficient of the interfacial orientation degree is 0.35 or less, an excellent appearance characteristic is kept, and the generation of the vertical stripe and the yellowing or whitening tendency are prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) No. 21 relates to a plastic injection-blow molded multilayer container, and more particularly to a biaxially oriented injection-blow molded multilayer container with improved appearance characteristics. Regarding.

(Prior art) Polyester containers made by stretch blow molding have excellent transparency and appropriate rigidity, and can be used for liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc., as well as carbonated beverages such as beer, cola, and cider. It has also come to be widely used in containers for soft drinks such as fruit juice and mineral water.

This stretched I polyester container is 71? Compared to general-purpose resin containers such as polyethylene and polypropylene, the gas barrier
Although cans and bottles have almost zero gas permeability, they have a non-negligible permeability to oxygen and carbon dioxide, and the shelf life of the contents is limited. Limited to a relatively short period of time.

In order to improve this drawback, various efforts have been made to improve the gas barrier properties of containers by combining polyester with gas barrier resins such as ethylene-vinyl alcohol copolymers and polyamides containing xylylene groups to create a multilayer structure. Proposed.

To manufacture a stretched multilayer plastic container, it is first necessary to manufacture a multilayer preform, and various methods such as coextrusion, multistage injection molding, and coinjection molding are used to manufacture this multilayer preform. method is known.

(Problems to be Solved by the Invention) When forming a multilayer preform by co-injection molding, a layer structure is generally adopted in which the inner and outer surface layers are thermoplastic polyester and the intermediate layer is a gas barrier resin. It has been recognized that the co-injection molding method (Japanese Patent Application Laid-Open No. 51-2773) suffers from certain drawbacks regarding the thickness distribution of each layer within the multilayer preform.

That is, the thickness of the inner surface layer of polyester is significantly reduced at the bottom of the preform because the thickness direction of the Gasno9 rear layer (intermediate layer) is biased inward at the bottom of the preform. For example, the thickness of the outer surface layer (A) and the thickness of the inner surface layer (B)
The ratio of A:B in the body was 2:1, but in the bottom the ratio was A:B=5:1, and the thickness of the inner surface layer of the bottom was significantly reduced.

The reason for this is that in the injection mold cavity, the dart into which the molten resin flows is provided at the bottom, so other parts of the bottom are at a high temperature, and the resin on the inner surface of the bottom also flows to other parts. This is thought to be due to the pressure that they receive.

When the bottom inner surface layer becomes thinner in this way, the inner surface layer becomes even thinner during stretch blow molding, and in severe cases, there is a tendency for the gas barrier layer to be exposed inside, which prevents moisture absorption from the contents. This may increase the gas permeability of the intermediate layer, or cause separation between the intermediate layer and the polyester layer, or even cause separation, with the exposed gas barrier layer floating in the contents. Hikodo has some drawbacks.

In addition, in injection-blow molded containers, the mouth of the container,
The internal thickness of the shoulders and bottom is thicker than that of the body of the container, and therefore the thickness of the gas barrier intermediate layer is also greater than the thickness of the gas barrier intermediate layer at the mouth, shoulders and bottom. It has been found that the presence of a thick unstretched intermediate layer has a significant negative effect on the appearance characteristics of the container.

For example, ethylene-vinyl alcohol copolymer, which is one of the thermoplastic resins with the best gas barrier properties, tends to have thickness variations in the circumferential direction of the preform during co-injection, and the shoulder area of the container where the degree of stretching is low. At the bottom of the container, this variation in thickness appears as vertical lines, which impairs the appearance characteristics of the container. In addition, when the intermediate layer is made of gas barrier polyester containing an isophthalic acid component as part of the acid component and a bis(2-hydroxyethoxy)benzene component as part of the glycol component, the bottom and shoulders have a yellow appearance. This also impairs the overall appearance of the container. Furthermore, when the intermediate layer is made of metaxylylene group-containing polyamide, the bottom and shoulders become white and have a cloudy appearance, which also tends to impair the overall appearance of the container.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a biaxially oriented injection-blow-molded multilayer container which eliminates the above-mentioned drawbacks of conventional injection-blow-molded multilayer containers and has significantly improved appearance characteristics.

(Means for Solving the Problems) According to the present invention, there is provided a multilayer container manufactured by stretch blow molding a plastic multilayer preform manufactured by an injection molding method. The wall thickness of the bottom part is larger than that of the body part, and at least the body part C has a multilayer structure consisting of inner and outer surface layers made of thermoplastic polyester and a gas barrier-type plastic resin intermediate layer located between both surface layers. Yes, Ul, f Svalier thermoplastic resin intermediate layer is always present in the container part where the in-plane orientation coefficient (l+m) of the inner and outer surface layers is 0.50 or more, but the inner and outer surface layers The in-plane orientation coefficient (l+m
) is absent in the container portion of 0.35 or less.

(Function) In FIG. 1 showing an example of the biaxial molecular orientation injection-blow molded multilayer container of the present invention, this container has a mouth portion 1, a shoulder portion 2,
It consists of a body 3 and a bottom 4.

In this container, the wall thickness of the mouth portion 1, shoulder portion 2 and bottom portion 4 is greater than the wall thickness of the body portion 3. Now, assuming that the thickness at the center of the body of the container is 1, the ratio of the wall thickness of each container part is as shown in Table 1 below. Of course, in the case of the shoulder part 2, the wall thickness distribution is such that the wall thickness is maximum at the connection part with the neck part and the wall thickness is the minimum thickness at the connection part with the torso part, while in the case of the bottom part 4, the thickness distribution is such that the wall thickness is the maximum at the connection part with the neck part, and the thickness distribution is such that the wall thickness is the minimum thickness at the connection part with the body part. A wall thickness distribution is shown in which the thickness is the maximum and the thickness is the minimum at the connection part with the body, but the thickness ratio of the shoulder part 2 and the bottom part 4 is shown as the thickness ratio of the intermediate part.

Table 1 General range Preferred range Opening part 2-2 5 3-20 Shoulder part 1.1-15 1.3-10 Body part 1l Bottom part 1.2-30 1.5-25 Among the containers of the present invention, At least the body 3 has an inner surface NI5 and an outer surface layer 6 made of thermoplastic polyester, and an intermediate NI made of a gas barrier-like plastic resin located between these two surfaces.
7, the intermediate layer 7 of the gas barrier plastic resin has an in-plane orientation coefficient (l+m) of the inner surface layer 5 and the outer surface layer 6 of O. Although it is always present in the container portion of SO or higher, it is provided so that it is absent in the container portion where the in-plane orientation coefficient (10 m) of the inner surface layer 5 and outer surface layer 6 is 0.35 or less. A notable feature is that In the specific example shown in FIG. 1, the middle layer 7 of the gas barrier resin is missing at the mouth 1 of the container (the mouth consists only of polyester), and the middle layer 7 at the shoulder 2 and bottom 4 is omitted. 7
It is clear that the area is located in the middle of these areas.

In this specification. The in-plane orientation coefficient (l+m) is a characteristic value that quantitatively indicates the degree of molecular orientation in the direction of the container wall surface determined by polarized fluorescence photometry.

The density of polyester is generally used as a measure to express the molecular orientation of polyester, but since the density of polyester varies greatly depending not only on the degree of molecular orientation but also on the degree of heat fixation (i.e. crystallinity), the present invention In this case, it cannot be used as a measure of molecular orientation.

On the other hand, polarized fluorescence spectroscopy uses the optical anisotropy of fluorescent molecules adsorbed on molecularly oriented polymers to quantitatively measure the molecular orientation of polymers. This allows the degree of molecular orientation to be determined without being affected by heat fixation. The two-dimensional orientation coefficient within the wall of the container obtained by this polarized fluorescence method is expressed by the following formula.

1, (ω) = φ (group s'ω-1-msfn'ω+'n
) -・-ct＞In the above equation, I and (ω) represent the polarization component intensity of fluorescent light emitted from the thermoplastic resin sample, and l indicates that the vibration direction of the incident polarized light and the photometric polarization direction are parallel. where ω indicates the rotation angle of the sample with respect to the vibration direction of the polarized light. is the maximum excitation probability when the vibration direction of the excited fluorescence is parallel to the sample molecular axis, and φ is the molecular fluorescence yield. L is the ratio of molecules oriented in one arbitrary direction within the wall surface of the final molded container, m is the ratio of molecules oriented in the direction perpendicular to t, and the ratio of non-orientation in the aFi plane, L + m + n = 1.

It can be expressed quantitatively.

In this way, ω is changed (0°, 45°, 90°), the polarization component intensity 1,(ω) for this ω is measured, and this 3
The values of l, m, and n can be found as solutions to the two simultaneous equations.

In the present invention, the in-plane orientation coefficient of the inner and outer surface layers of polyester <
In relation to L0m>, the gas barrier properties of the entire container can be improved by making sure that the intermediate layer of the gas-resistance resin is present in specific parts of the container and absent in other specific parts. This is based on the knowledge that it is important to improve the appearance characteristics without substantially reducing them.

That is, the polyester inner and outer surface layers have an in-plane orientation coefficient (l
+m) is 0.50 or more in the container part where the molecules are biaxially oriented in one row? Along with the thinning of the polyester by stretching, the gas barrier resin intermediate layer also becomes thinner, and as a result, the presence of the gas barrier resin intermediate layer causes the above-mentioned vertical streaks, yellowing tendency, whitening tendency, etc. The problem has been resolved to the extent that it cannot be discerned with the naked eye, and the appearance defect has been resolved. Although the entire container wall is thinned in this container portion, the amount of gas permeation is suppressed to a small level due to the presence of the gas barrier resin intermediate layer.

On the other hand, the polyester inner and outer surface layers have an in-plane orientation coefficient (l
-) In the container part where the molecules are oriented only so that -m) is 0.35 or less, the entire container wall is thick, but
By not providing a gas barrier resin intermediate layer in this area, the excellent appearance characteristics of the polyester itself are maintained, and the aforementioned vertical streaks, yellowing tendency, and whitening tendency are prevented.

Furthermore, since this low-orientation or non-orientation portion has a thick vessel wall and occupies a small area ratio to the entire container, the amount of gas permeation through this portion can also be maintained at a small level.

Furthermore, gas barrier resin eyebrows are provided in the portion of the container where the in-plane orientation coefficient (L + m) is greater than 0.35 and less than 0.50 in both or either of the inner and outer surface layers of polyester. It should be understood that it may or may not be provided.

Now, the area of the container part (high degree of orientation part) where the in-plane orientation coefficient (l-)-m) is 0.50 or more is SH1 the thickness is tH.

The oxygen permeability coefficient is PIK, and the area of the container part (low orientation part) where t+m) is 0.35 or less is SL, and the thickness is tL.
, the oxygen permeability coefficient is 9, and t+m) is the area of the intermediate portion (intermediate degree of orientation), SM, the thickness is tM, and the oxygen permeability coefficient is PM, then the oxygen permeation per unit time for the entire container is When the quantity is Q, it is expressed as follows.

In addition, the oxygen permeability coefficient (p, g) of the three-layer structure part, for example, the highly oriented part, the oxygen permeability of the polyester layer is PP,
and the thickness is tP, and the oxygen permeability coefficient of the gas-reactive resin is P. and the thickness is expressed as .

27℃ of polyester layer and various gas barrier resins
, oxygen permeability coefficient (POx
×10”cc”cm/cm2. See-cmHg) is shown in Table 2 below.

Table 2 Polyethylene terephthalate (unstretched) 4.06
(Biaxial stretching) 2.14 Ethylene-vinyl alcohol copolymer (contains vinyl alcohol! 69.9 mol% less than 1.43
Stretched) Biaxial stretching 0.39 Poly-xylylene adipamide (unstretched) 1.04 Same
Biaxial stretching 0.42 is sparring polyester (unstretched) 0.88 Biaxial stretching 0.51 In general, in molecularly oriented injection-blow molded containers, the ratio of each part to the total surface area of the container, SL is S□ is 2 to 100%, and SM is 5 to 200% of SII. Further, the thickness tL of each container portion is 1.5 to 25 times t8, and t
M is the intermediate thickness between tL and tl.

So, for example, tL=4XtH, tM=2Xrice.

5L=0. IXS, l SM = 0.2 Oxygen permeation rate (Ql
), the ratio of oxygen permeation ff1 (Qz), Q2/Ql, is calculated using the formula (2) when the intermediate layer is provided only in the highly oriented portion.
Calculating from (3), the value of Qz/Qx is 1.02
2, and the gas barrier is
Even if the intermediate resin layer is excluded, the increase in oxygen permeation is approximately 2%.
It becomes clear that it can be almost ignored. In addition, the same calculation was performed for the polyester single-layer container excluding the f-sparring resin intermediate tank, and its oxygen permeation amount (Q3)
, and the Q*/QsO ratio is found to be 0.76.

It can also be seen that the amount of oxygen permeation can be suppressed to a value of about 374.

Thus, according to the invention, the container has an excellent gas barrier.
It becomes clear that the appearance characteristics of the container can be significantly improved while maintaining its properties.

Constituent resin material The resins used in the container described above are as follows.

Polyethylene terephthalate is preferably used as the thermoplastic polyester (hereinafter sometimes simply referred to as PET), but as long as it does not impair the essence of polyethylene terephthalate, polyethylene terephthalate units are the main component,
Copolyesters containing other polyester units may also be used. Copolymerization components for forming such a copolyester include isophthalic acid, p-β-oxyethoxybenzoic acid, Φnaphthalene, 2,6-dicargenic acid, diphenoxyethane-4,4'-dicargen, and 5-sodium sulfonate. Radicals such as isophthalic acid, azobic acid, Φsepacic acid, or their alkyl ester derivatives? Examples of glycol components include propylene glycol, 1,4-butanediol, neopentyl glycol, 1゜6-hexylene glycol, cyclohexane dimetatool, ethylene oxide adduct of bisphenol A, diethylene glycol, triethylene glycol, etc. be able to.

The thermoplastic polyester used is generally in a mixed solvent of phenol and tetrachloroethane in a weight ratio of 60:40 from the viewpoint of the mechanical properties of the vessel wall.

The intrinsic viscosity (IV) when measured at a temperature of 30°C is 0.
It is desirable that it is 5dl19 or more, especially o, 6a/g or more. Furthermore, this polyester can be used as colorants such as pigments and dyes,
It may also contain additives such as ultraviolet absorbers and antistatic agents.

In one aspect of the present invention, it is important to use an ethylene-vinyl alcohol copolymer having a vinyl alcohol content of 40 to 85 mol, particularly 50 to 80 mol, as the intermediate gas barrier resin layer. . That is, the ethylene-vinyl alcohol copolymer is one of the resins with the best gas barrier properties, and its gas barrier properties and thermoformability depend on the vinyl alcohol unit content. When the vinyl alcohol content is less than 40 molar ratios, the permeability to oxygen and carbon dioxide is greater than when it is within the above range, and it is not suitable for the purpose of the present invention, which is to improve gas barrier properties. On the other hand, if the content exceeds 85 mol, the permeability to water vapor increases and the melt moldability decreases, which is not suitable for the purpose of the present invention.

Ethylene-vinyl alcohol copolymer C. Obtained by saponifying a copolymer of ethylene and a vinyl ester such as vinyl acetate so that the degree of saponification is 96% or more, particularly 99% or more, In addition to the above-mentioned components, this copolymer may contain propylene, butylene-1, isobutylene, etc. having a carbon number of 3, within a range that does not impair the barrier properties against oxygen, carbon dioxide, etc., for example, within a range of 3 mol. The above olefin may be contained as a comonomer component.

The molecule it of the ethylene-vinyl alcohol copolymer is not particularly limited as long as it has a molecular weight sufficient to form a film. It is preferable that the intrinsic viscosity (IV) is in the range of 0.07 to 0A71/9 when measured at a temperature of .

In another embodiment of the invention, a xylylene group-containing polyamide is used as the gas barrier resin for the intermediate layer. The xylylene group-containing polyamide is a polyamide containing m-xylylene diamine and/or p-xylylene diamine as a diamine component, and more specifically, 35 mol% or more, especially 50 mol% or more of the diamine component is m- xylylene and/or hp-xylylene diamine, in which the dibasic acid component is an aliphatic dicarboxylic acid and/or an aromatic dicarboxylic acid, optionally containing up to 25 molar units, especially up to 20 molar units per total amide repeating unit. Contains ω-aminocarboxylic acid units.

Diamine components other than xylylene diamine include aliphatic diamines such as hexamethylene diamine, alicyclic diamines such as piperazine, and examples of aliphatic dicarboxylic acids include adipic acid, sepacic acid, and speric acid. Examples of aromatic dicarboxylic acids include terephthalic acid and isophthalic acid. Examples of the ω-aminocarmenic acid component include ε-caprolactam, aminehebutanoic acid, and amineoctane. Examples of xylylene group-containing polyamides include, but are not limited to, -rimetaxylylene azinogumide, polymethaxylylene sepacamide, polymethaxylylene sveramide, m-
Xylylene/p-xylylene adipamide copolymer, m-
xylylene azitzumide/isophthalamide copolymer, m
-xylylene adipamide/isophthalamide/ε-amitsukazolonic acid copolymer, etc.

In another embodiment of the present invention when the polyamide is used, 30 inphthalic acid component units can be used as described in, for example, JP-A No. 60-232952, JP-A No. 60-240452, etc. ~1000
Diamine component units contained in the 0 mol% range are 35 to 50
mol%, 35 to 50 mol% of diamine component units mainly composed of metaxylylenediamine component units, and O to 30 mol% of aminocarmenic acid component units having a carbon number of 5 to 12. Substantially linear co-condensed polyamides can also be used as gas barrier resins for the intermediate layer.

The polyamides used are 0% as measured using 96% sulfuric acid at a concentration of 1.9/100 and a temperature of 25°C.
．． It is desirable to have a relative viscosity (ηrel) of 4 to 4.5.

In yet another aspect of the invention, a gas barrier is used as the intermediate layer.
Use synthetic polyester.

Gas barrier polyester (hereinafter referred to as BP) used in the present invention
It is sometimes written as R. ) contains the terephthalic component (T) and the isophthalic acid component (I) in the polymer chain, T:I = 95:5 to 5:95, especially 7
Contained in a molar ratio of 5:25 to 25nia 5 and an ethylene glycol component (g))
and bis(2-hydroxyethoxy)henmen component (BH
EB) and E:BHEB=99.999: 0.001 to 2.
0: 98.0 especially 99.95: 0.05
It is contained in a molar ratio of 40:60 to 40:60. As BHEB, 1,3-bis(2-hydroxyethoxy)benzene is preferred.

T・I/I used in the present invention: -BHEB co-I polyester (BPR Zheng, exhibits an oxygen permeability coefficient (PO) of the order of about 1/3 to 1/4 compared to polyethylene terephthalate, and has an oxygen permeability coefficient of humidity The advantages are that there is almost no dependence, that thermoforming is more stable than with other gas-based resins, and that the adhesion to polyethylene terephthalate is extremely good.

Of course, one gas barrier polyester (B
PR) may contain small amounts of other dibasic acid components or other diol components within the range that does not impair its essence; for example, oxycarmene such as p-β-oxyethoxybenzoic acid Acids, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5
-Sodium sulfoisophthalic acid, adipic acid, 7-4
Dicarboxylic acid components such as cinic acid or their alkyl ester derivatives, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, cyclohexanedimethanol, ethylene oxide adducts of bisphenol A, etc. It may also contain a glycol component or the like.

This polyester (BPR) should have at least a sufficient molecular weight to form a film, and is generally measured at a temperature of 30°C in a mixed solvent of phenol and tetrachloroethane in an IT ratio of 60:40. , 0.3 to 2
．． It is desirable to have an intrinsic viscosity [η] of 8J/9, special KO, 4 to t, and sdx/9.

The gas barrier resins for the intermediate layer exemplified above can be used alone or in the form of a mixture of two or more. Furthermore, in order to improve the adhesion between the inner and outer polyester layers, the intermediate layer can be injected by supplying a tri-blend or melt blend with an adhesive resin to an injection machine for the intermediate layer.

Suitable examples of adhesive resins are aliphatic polyamide resins, especially copolyamides such as nylon 6/nylon 6.6 copolymers. Adhesive resin is gas barrier resin 10
It can be used in a proportion of 1 to 100 parts by weight, especially 5 to 50 parts by weight per 0 parts by weight.

Manufacture of multilayer preform The injection-blow molded multilayer container of the present invention is manufactured by manufacturing a multilayer preform by a co-injection method and stretch blow molding this multilayer preform. The corresponding thermoplastic polyester is in the solid flow, the thermoplastic polyester corresponding to the outer surface layer is in the outer annular flow, and the gas barrier resin corresponding to the intermediate layer is in the inner annular flow between the solid flow and the outer annular flow. In this co-injection, the injection timing of the gas barrier resin corresponding to the intermediate layer is compared to the injection timing of the thermoplastic polyester. The gas barrier resin intermediate layer is controlled to be slow at the beginning of injection and fast at the end of injection, and the gas barrier resin intermediate layer is absent in the preform parts corresponding to the low or non-oriented parts of the container mouth, shoulders and bottom. Manufactured by

In FIG. 2, which conceptually shows a simplified cross-sectional structure of the multilayer die used in the present invention, the multilayer die 11 includes solid channels 12 for polyester corresponding to the inner surface layer of the multilayer preform. An outer annular channel 13 for polyester corresponding to the outer surface layer of the multilayer preform, and an F corresponding to the intermediate layer (gas barrier resin layer) of the multilayer preform between these.
Inner annular channels 14 for the sparring resin are provided, and each of these channels 12, 13 and 14fl injection mold dart (
a single hot runner nozzle 1 connected to a hot runner (not shown)
It opens at 5.

In the present invention, the polyester for the inner surface layer, the polyester for the outer surface layer, and the gas barrier resin for the intermediate layer are injected translationally into an injection mold through the channels and darts of the hot runner. In this specification, "translationally injected" means that each resin is simultaneously injected in a uniform state through each channel.

The injection of polyester prior to the injection of the gas barrier resin and the injection of the polyester after the injection of the gas barrier resin may be performed using either the polyester for the inner surface layer or the polyester for the outer surface layer, or may be performed using both. It's okay. As a preferred example, a pre-injection is carried out with a d polyester for the inner surface layer and a post-injection is carried out with a polyester for the outer surface layer.

The production of a multilayer preform by the above-mentioned co-injection molding method will be specifically explained using FIGS. 3 to 5 as examples.

Part 3 showing the schematic arrangement of the equipment used to carry out the method of the present invention.
In the figure, an injection machine 16 for inner N polyester, an injection machine 17 for outer layer polyester, and an injection machine 18 for intermediate layer gas barrier resin are provided, respectively. Each of these injection machines injects a corresponding runner 16 of the hot runner block 19 through their respective tip nozzles 15a, 17a, 18m.
b, 17b and 18b, respectively. The hot runner nozzle 15 has a solid flow path 12 for the inner layer polyester at the center, an annular inner annular flow path 14 for the intermediate layer gas barrier resin around the solid flow path 12, and an outer annular flow path for the outer layer polyester around the outer periphery. 13 is located so that these flow paths merge near the hot runner nozzle tip 20. In the multilayer die shown in FIG. 3, the first central channel 12 corresponds to the injection of the inner layer of the preform, the inner annular channel 14 corresponds to the intermediate layer of the preform, and the outer annular channel 13 corresponds to the injection of the outer layer of the preform. be. hot runner
Although only one hot runner nozzle is shown in block 19, it should be understood that multiple hot runner nozzles may be provided. Above the block 19 is a cavity mold 2 which is integrally connected to the block 19.
1 is provided. The cavity mold 21 is provided with a cavity 22 whose axis extends vertically and is connected to the hot runner nozzle 15 of the block 19 via a shaft 23.
As a matter of course, the number of hot runner nozzles 15 corresponds to the number of hot runner nozzles 15 provided in parallel.

A core 24 that defines the inner surface of the preform during molding and a neck grip split mold (not shown) that defines the outer side of the preform bottom during molding are provided to be combined with this cavity mold 21 during injection molding.

First, during injection molding, each injection machine, hot runner block, and injection mold are in the state shown in FIG. 3.

At this position, the screw of the inner layer injection machine 16 advances, and the polyester resin is transferred to the nozzle 16'5FF three-layer resin runner 16b, the solid flow path 12 in the hot runner nozzle,
A certain amount is injected into the cavity 22V3 through the date 23. With a slight delay in timing, the screws of the outer layer injection machine 17 and the intermediate layer injection machine 18 are moved forward. As a result, the outer layer resin passes through the nozzle 17&, the runner 17b, and the outer annular flow path 13.
The intermediate layer resin is supplied to the hot runner nozzle tip 20 through the nozzle 18a, the runner 18b, and the inner annular channel 14.

In FIG. 4, which shows the initial stage of injection, the tip 2 of the resin flow
5 is made of polyester, polyester solid flow 12 &
A multilayer resin flow is formed at the nozzle tip, consisting of a ring-shaped flow of 14 m of sparring resin around it, and a ring-shaped polyester flow of 13 m around its outer periphery. Next, in FIG. 5, which shows a state in which the injection has progressed, this multilayer resin flow flows into the orifice in the injection mold, and the polyester solid flow 12a flows into the preform inner surface layer 26 and the polyester outer annular flow 13.
It can be seen that 1 is the outer surface RfI 27 and the gas barrier resin inner annular flow 14a is the preform intermediate layer 28.

Furthermore, the injection of the gas barrier resin is finished at a certain time before the cavity 22 of the injection mold is filled with the resin.

By the above-described operation, the intermediate Ir128 is located in the part of the preform corresponding to the highly oriented part, and the intermediate layer 2 is located in the part of the preform corresponding to the low oriented or non-oriented part.
A multilayer preform is formed in which 8 is missing.

Stretch Blow Molding The multilayer preform thus obtained is subjected to stretch blow molding into a multilayer container.

Prior to this stretch blow molding, the multilayer preform is first maintained at the stretchable temperature of the main resin layer, ie the stretching temperature of the polyester, generally from 80 to 135°C, particularly from 90 to 125°C. In this temperature control process, the polyester resin layer of the multilayer preform is supercooled so as to be maintained in a substantially non-crystalline state (amorphous state), and then heated using a heating mechanism known per se such as hot air, an infrared heater, or a high-frequency dielectric heating. This can be carried out by heating the multilayer preform to the above temperature, or by cooling or releasing the multilayer preform in the injection mold or the mold until the temperature of the multilayer preform reaches the above temperature. This can also be done by cooling.

6 and 7 for explaining the stretch blow molding operation, a mandrel 31 is inserted into the mouth of a bottomed multilayer preform 30, and the mouth is inserted into a pair of split molds 32.
Clamp with a and 32b. A vertically movable stretching rod 33 is provided coaxially with the mandrel 31, and this stretching $33
An annular passage 3 for fluid suction is provided between the mandrel 31 and the mandrel 31.
There are 4.

The tip 35 of the stretching rod 33 is applied to the inside of the bottom @ 36 of the preform 30 and the stretching rod 33 is moved downward to perform tensile stretching in the axial direction.
A fluid is blown into the preform 30 through the pressure of the fluid, and the preform is expanded and stretched within the mold to form a container 37.
to form.

The degree of stretching of the preform is sufficient to give at least the above-mentioned molecular orientation to the body, but for this purpose, the stretching ratio should be 1.5 to 5 times in the axial direction of the container, and 2 to 5 times in the circumferential direction. It is desirable to make it 7 times.

After stretch-blow molding the container, the polyester constituting the container can be heat-treated, for example, at 110 to 230° C. to heat-set the oriented polyester.

The shape of the injection-blow molded multilayer container thus obtained is as follows:
In addition to a simple cylindrical shape, for the purpose of imparting heat resistance to the container, for example, as described in Japanese Patent Application No. 62-23491, a pillar-shaped convex part and a panel-shaped concave part are provided in the core body. It may be prepared.

Similarly, in order to impart heat resistance to the container, the multilayer preform described above or the mouth and neck portion may be crystallized and whitened by heat treatment after completion of molding of the container.

(Effects of the Invention) According to the present invention, it was possible to significantly improve the appearance characteristics of a molecularly oriented injection-blow molded multilayer container while maintaining its excellent gas barrier properties.

(Example) The invention will be explained in more detail in the following examples.

Example 1゜Injection machines for inner layer and outer layer are H3 manufactured by Husky Co., Ltd.
The injection machines for the 8SPH type and the intermediate J- are the FS-17ON type injection machines made by Nissei Jushi Kogyo Co., Ltd., and the prototype co-injection mold (co-injection goo) made by Gifu Husky Co., Ltd. Using an injection device, polyethylene terephthalate (pE'r, each oxygen permeability coefficient is listed in Table 2)'! i-1 Also, the relative viscosity (ηR
Poly m-xylerin anopamide (EL) of 2,24 (
Nylon ■6. Each oxygen permeability coefficient is listed in Table 2) was supplied.

And, ■Setting temperature of injection machine for inner layer and outer layer: Rear; 280℃
, Middle part: 280°C, Nozzle part: 285°C ■ Setting temperature of the injection machine for the middle layer: Rear part: 250°C.

Intermediate part: 250°C, nozzle part: 260°C ■Hot runner nozzle part temperature i: 285°C Under each temperature condition, a part of molten PET was injected into the cavity from the inner layer injection machine at the initial stage of injection, Subsequently, the molten PET is melted from the injection machine for the inner layer and the injection machine for the outer layer, and the melted PET is melted from the injection machine for the middle layer.
were simultaneously injected, the inner layer injection machine and the intermediate layer injection machine were stopped at the end of the injection, and the molten PET was injected only from the outer layer injection machine, and the weight was 32.89 mm and the overall average wall thickness was 3.5 mm.
A multilayer preform of 2 types and 3 layers was molded.

The obtained nine glyphomes were processed using OB manufactured by Toyo Food Machinery Co., Ltd.
Using an M-1 biaxial stretch blow molding machine, the inner diameter of the mouth was 3.
01m, dripping internal volume is 102:3LA! (The weight is 32
．． 81 cylindrical bottles were molded.

The bottle molding conditions are a preform temperature of 100℃ and a
After heating for 6 seconds, blow molding was performed in the mold for 4 seconds.

&Tor's stretching ratio is 2.3 times in the vertical (axial) direction, and 2.3 times in the horizontal (circumferential) direction.
The direction was 3.5 times, the total average wall thickness of the entire tettle excluding the mouth was about 0.415 m, and the thickness ratio of inner layer: middle RA: outer layer was 521:5. Below, this multi-layered
'

For comparison, using the above-mentioned co-injection apparatus and the above-mentioned biaxial stretch blow molding machine, a conventional co-injection molding method such as that described in JP-A No. 51-2773 was carried out. It has a shape, wall thickness, internal volume, and weight, and the middle layer (seat 6) is present over the entire area of the mouth, shoulders, body, and bottom of the door. A ff4 hotol was molded. Hereinafter, this multilayer bottle will be referred to as "@A-B".

Furthermore, for comparison, the molten PET was injected using only the inner layer injection machine among the co-injection apparatuses described above;
After molding a single-layer glyform having a weight of 32.89 mm and an overall average wall thickness of 3.35 m, a single-layer PETylS mold was molded using the above biaxial stretch blow molding machine under the same molding conditions as above. Below, this PET single-layer bottle will be described as “A-C”.
”.

Among these three types of PET multi-layer and PET single-layer bottles, A-A, 3? ), 4 locations in the axial direction of the shoulder excluding the mouth, 5 locations on the body, and 3 locations on the bottom.
In the circumferential direction of &), if compared to a clock face, there are four locations at 12 o'clock, 3 o'clock, 6 o'clock, and 9 o'clock, that is, a total of 48
Eight portions were cut out, and the in-plane orientation coefficient (l+m) of the PET inner layer and outer layer (however, if the intermediate layer was omitted, the entire PET layer) was measured according to the method described above.

The results are shown in Table 3. Further, the total surface area of the shoulder, body, and bottom of the bottle excluding the mouth is approximately 570 crn2,
When the area ssH' of the highly oriented part (in-plane orientation coefficient is 0.50 or more) was measured using graph paper, it was found to be about 75% of the whole (the average thickness of the whole part, tH is 0.5%).
28 m), intermediate degree of orientation (in-plane orientation coefficient is 0.3
5 and 0.50), the area of the part, SM is also about 16
% (the overall average thickness of the part, tl is 0.62 tt
m ), and the area of the low orientation degree (in-plane orientation coefficient is 0.35 or less) portion.

SL is also about 9 inches (the overall average thickness of the part.

tL was 1.19 tm).

Next, we measured the "oxygen gas permeability" of the 38 class metres of @A-A", "A-B" and @A-C". For the two types of &) bottles, tests were conducted on the appearance of the container and the state of peeling at the bottom of the container.

(1) Oxygen gas permeability: Put a small amount of water in the AAI bottle to be measured and replace it with nitrogen gas in a vacuum (nitrogen concentration is 99.99% or more)
1. Furthermore, after treating the contact area 11fi between the gotrud and the rubber stopper with epoxy adhesive, the bottle was heated to a temperature of 3.
It was stored for 5 weeks in a constant temperature and humidity chamber set at 0°C and relative humidity of 80% RHK.

After that, the concentration of oxygen that permeated into each bottle was measured using a gas chromatograph, and the oxygen gas permeability of the container (QO2, unit: e(27m2・day-a
tm ) was calculated: Qo* = (mXCt /10
0]/t
Storage period in constant temperature and humidity chamber (=35) (day), C
After tHt days, the oxygen concentration in Toru (Maof%), 0p;
Oxygen gas partial pressure (=0.209) (atm), A; Effective area of bottle (m2).

Oxygen gas permeability #QO2 was measured for 10 meters of each type.

Table 4 shows the arithmetic mean value and standard deviation value of the oxygen permeability obtained for each bottle AA, AB, and AC.

From Table 3 and Table ig4, the middle layer (W2O layer) is approximately 25
% missing multilayer yjf) le [A-A] and intermediate layer (W
O2 layer) is yl? ) There is no significant difference in oxygen barrier properties from the arithmetic mean value and standard deviation value of oxygen gas permeability between the multilayer bottle [A-B] which exists over the entire area of the bottle, and these yj? ) is known to have clearly superior oxygen barrier properties than the PET single layer yN).

(2) Appearance of the container: A panel of 11 people said that both @A-A" and -A-13'
l? ) (however, all are empty). Good or bad condition of the shoulders and body (degree of whitening, degree of yellowing, vertical streaks, etc.)
They were asked to compare and judge visually.

As a result, all 11 people agreed that the "A-B"&)ru (comparative example) in which the middle layer was present over the entire area of the bottle was better than the @A-A''&toru according to the present invention. The degree of whitening is clearly large (part defective).''

(3) Peeling condition at the bottom of the container: @A-A” and “A-B” whose empty weight was measured in advance
50 of the injected volume into each of the 5 bottles of each yf?
After filling the bottle with 80% tap water, add citric acid (21.8.9) and sodium bicarbonate (26.2.9), and immediately after filling the bottle with tap water and dripping, Using an M401A-PN sealing machine manufactured by Shokuhin Kikai Co., Ltd., the mouth of the bottle was sealed with an aluminum cap with a septum. Each sample meter thus obtained was incubated at 30'C.

After storing it for a day and night in a constant temperature and humidity chamber set at 80% RH, insert a pressure gauge with a three-way cock through the septum of the cap, open the drain valve, and check the equilibrium pressure inside the bottle (
Gas was vented until the gauge pressure became 3.95 kl/cm2 (4.0 gas olium). and,
The sample bottles were placed again in a constant temperature and humidity chamber at 30°C and 80% RH, and each sample bottle (5 bottles of each type) was visually observed at a fixed time every day. , &) The number of days during which delamination (peeling) occurred near the gate at the bottom of the mold was investigated.

Regarding @A-A”&)le according to the present invention.

Observation for 35 days revealed that no delamination (peeling) occurred on the bottom of all the pieces (5 pieces), while “A”
-B″yf) (comparative example), bottom peeling occurred in the first one after 4 days, and bottom peeling occurred in all the samples after 35 days.

Example 2 ASB-65ONTH manufactured by Nissei NSP Machinery Co., Ltd.
Using an improved co-injection/biaxial stretching molding machine, the polyethylene terephthalate (PET) described in Example 1 was supplied to the inner layer and outer layer injection machines of the same machine, and the intermediate The vinyl alcohol content in the layer injection machine is 69
．． An ethylene-vinyl alcohol copolymer (EVOH, whose oxygen permeability coefficients are listed in Table 2) with a 9 molt and an intrinsic viscosity of 0.1 st and 7 gtv was supplied. And, ■Setting temperature of injection machine for inner layer and outer layer: Rear; 280℃
, middle part: 280°C, nozzle part: 285°C.

■Setting temperature of the injection machine for the middle layer: Rear; 230℃.

Middle part: 230°C, nozzle part: 225°C.

■Hot runner nozzle temperature: 285℃.

Under each temperature condition, a part of the bath melted PET is injected into the cavity from the inner layer injection machine at the initial stage of injection, and then the bath melted PET and the middle layer injection machine are injected from the inner layer injection machine and the outer layer injection machine. At the end of the injection, the inner layer injection machine and the intermediate layer injection machine were stopped, and the molten PET was injected only from the outer layer injection machine.
In step 1, a multilayer glyform consisting of 2 types and 3 layers with an overall average thickness of 4.00 mm was molded, and then in a blow zone: (1) Heating temperature of the multi-no preform: 130°C.

Under these conditions, biaxial stretch blow molding was performed with a longitudinal (axial) direction stretch ratio of 2.5 times and a transverse (circumferential) direction stretch ratio of 3.4 times. 1517
(heavy weight is so, 1g), and excluding the mouth part.
A cylindrical multi-layered bottle was molded with a total average wall thickness of about 0.473 mm and a 2-type, 3-layer structure with an inner layer: intermediate layer: outer layer thickness ratio of 5:1:15.

Hereinafter, this multilayer &) layer will be referred to as °B-A''.

For comparison, the same shape and thickness as above were obtained by using the above-mentioned co-injection/, :axial stretch blow molding machine and the conventional co-injection molding method as described in JP-A No. 51-2773. thickness, internal volume and weight, and an intermediate layer (EVOH
) is present throughout the mouth, shoulder, body, and bottom of the bottle, and a multilayer bottle with two types and three layers was molded. Hereinafter, this multilayer bottle will be referred to as "BB".

Furthermore, for comparison, the molten PET was injected using only the outer layer injection machine among the above-mentioned co-injection/biaxial stretch blow molding machines, and the same shape, wall thickness, internal volume, and weight as above were obtained. A single layer of PET was molded. Is this PET single layer below? Tor is written as "B-C".

Among these three types of PET multi-layer and PET single-layer bottles, the B-A bottle was prepared according to the method described in Example 1, and the PET inner and outer layers of each part of the bottle (however,
The in-plane orientation coefficient (l+m) of the entire PET layer (in the case where the intermediate layer was omitted) was measured. The results are shown in Table 5. In addition, the total surface area of the shoulder, body, and bottom excluding the mouth of the glass is approximately 770 crn2, of which the highly oriented (
The area of the portion (with an in-plane orientation coefficient of 0.50 or more), SH is approximately 82 cm (the average thickness of the entire portion, tH) is 0.
35 m), the area of the intermediate degree of orientation (in-plane orientation coefficient between 0.35 and 0.50), and the SM are also approximately 11% (
The overall average thickness of the part, tM, is 0.69 ms)
The area of the low-orientation (in-plane orientation coefficient is 0.35 or less) portion, SL, is approximately 7% (the average thickness of the entire portion).

tL was 1.61 m).

Next, according to each measurement method described in Example 1, three types of y, "B-A", "B-B", and "B-C" were measured.
l? ) for "Oxygen gas permeability" +1111 constant 1
-! 2s type bottles of 'B-A' and -B-B' were subjected to tests on the appearance of the container and the state of peeling at the bottom of the container.

(1) Oxygen gas permeability: Table 6 shows the arithmetic mean and standard deviation values of the oxygen gas permeability obtained for the three types of bottles mentioned above.

From Tables 5 and 6, the middle layer (EVOH layer) is approximately 18
% missing multilayer bottle [B-A] and middle layer (EVO
There is no significant difference in oxygen barrier properties from the arithmetic mean value and standard deviation value of oxygen gas permeability between the multilayer bottle [B-B] in which the H layer) exists over the entire area of the bottle. is known to have clearly superior oxygen barrier properties than the PET single-layer bottle (B-C).

(2) Appearance of the container: All 11 panel members agreed that the "B-B" bottle (comparative example) in which the middle layer exists over the entire area was better than the "B-A" bottle according to the present invention. "There are clearly many vertical streaks (that is, defective)," was the answer.

(3) Peeling condition at the bottom of the container: Regarding the "B-A" bottles according to the present invention, during observation for 35 days, no delamination (peeling) occurred at the bottom of all the containers (5 bottles). , "B-B"& Tor (comparative example), bottom peeling occurred in the first one after 2 days, and bottom peeling occurred in all the samples after 35 days.

Example 3 Using the co-injection/biaxial stretch blow molding machine described in Example 2, the polyethylene terephthalate (PET) described in Example 1 was injected into the same inner layer and outer layer injection machines, respectively. The polymer chain contains a terephthalic acid component and an inphthalic acid component in a molar ratio of 70:30, and an ethylene glycol component and bis(2-hydroxyethoxy)benzene. Ingredient Tora 95
: Contained at a molar ratio of 5, with an intrinsic viscosity (Equation y of 0.69d
1/g of thermoplastic polyester (I3PR, oxygen permeability coefficients listed in Table 2) was supplied. And, ■Setting temperature of injection machine for inner layer and outer layer: Rear; 280
°C, middle part: 280 °C, nozzle part: 285 °C ■ Setting temperature of the injection machine for the middle layer: rear part: 130 °C.

Middle part: 200°C, nozzle part: 225°C ■Hot runner nozzle temperature: 285°C Under each temperature condition, a part of molten PET was injected from the inner layer injection machine into the cavity at the initial stage of injection, and then The molten PET is simultaneously injected from the inner layer injection machine and the outer layer injection machine, and the molten BPR is simultaneously injected from the middle layer injection machine, and at the end of the injection, the inner layer injection machine and the middle layer injection machine are stopped, and the above molten PET is injected only from the outer layer injection machine. Molten PET is injected, the weight is 58.8g, and the overall average wall thickness is 4.20g.
A multilayer preform with two types and three layers of M is molded, and then in a blow zone, the longitudinal (axial) direction stretching ratio is 1.9 times under the conditions of (1) Heating temperature of the multilayer preform: 130°C. , by performing biaxial stretch blow molding with a lateral (circumferential) direction stretch ratio of 4.0 times,
The inner diameter of the mouth is 36 m, the internal volume of the dripper is 1526 m (the weight is 5 m)
8.89), and the total average wall thickness of the entire tettle excluding the mouth part is approximately 0.549 shoulders, and the thickness ratio of the inner layer: intermediate layer: outer layer is 2:1:3, which is a two-layer, three-layer structure. A cylindrical multilayer bottle was molded. Hereinafter, this multilayer &tor will be referred to as "C-A'."

For comparison, using the above-mentioned co-injection/biaxial stretch blow molding machine, the same shape as above,
A multi-layer bottle of two types and three layers that has wall thickness, internal volume, and weight, and the middle layer (BPR) is present throughout the mouth, shoulder, body, and bottom of the bottle. ) was molded. Hereinafter, this multilayer structure will be referred to as "C-B".

Furthermore, for comparison, the molten PET was injected using only the inner layer injection machine among the co-injection/biaxial stretch blow molding machines described above, and the same shape, wall thickness internal volume, and weight as above were obtained. A PET single) fI bottle was molded. Is this PET single layer below? Tor is written as "C-C".

Among these 3N type PET multi-layer and PET single-layer bottles, C-A-JL was prepared using the PET inner and outer layers of each part of the &)L (however, the middle layer was missing) according to the method described in Example 1. In the case where PET was used, the in-plane orientation coefficient (10 m2) of the entire PET layer was measured. The results are shown in Table 7. In addition, the total surface area of the shoulder, body, and bottom of the bottle excluding the mouth is approximately 865 crR2, of which the area of the high degree of orientation (in-plane orientation coefficient of 0.50 or more) is Sf
i is about 80% of the whole (the average thickness of the whole part, t8
is 0.41m+), intermediate degree of orientation (in-plane orientation degree coefficient is 0.41m+),
35 and 0.50), the area of the part, SM is also about 1
3% (average thickness of the entire part, tM is 0.80■)
The area of the hard and low orientation (in-plane orientation coefficient is 0.35 or less) portion, SL is approximately 7% (the average thickness of the entire portion).

tL was 1.74 fights).

Next, according to each measurement method described in Example 1, three types of y, "C-A", "C-B', and "C-C", were measured.
j? ) measurement of oxygen gas permeability,
For two types of bottles "C-A" and "C-B"
Tests were conducted on the appearance of the container and the state of peeling at the bottom of the container.

(1) Oxygen gas permeability: Table 8 shows the arithmetic mean value and standard deviation value of the oxygen gas permeability obtained for the three types of gases mentioned above.

From Tables 7 and 8, the bottle (C-A) is a multilayer in which the middle layer (BPR layer) is missing by about 20 inches, and the multilayer in which the middle layer (BPR layer) is present over the entire area of the bottle. Bottle (C
-B), there is no significant difference in oxygen barrier properties from the arithmetic mean value and standard deviation value of oxygen gas permeability, and these bottles clearly have a higher oxygen barrier property than the PET single-layer bottle [:C-C). It is known to have excellent barrier properties.

(2) Appearance of the container: All 11 mothers agreed that the "C-B" bottle (comparative example) in which the middle layer exists over the entire area was better than the "C-A" bottle according to the present invention. ``The degree of yellowing is clearly large (that is, defective).''

(3) Peeling condition at the bottom of the container: "C-, A'&)le according to the present invention and "C-" of the comparative example
Regarding B" bottles, during observation over 35 days, all (5 bottles) had delamination (peeled 1I) on the bottom.
I) did not occur. However, in the @C-B' bottle (comparative example), the deformation (expansion) of the bottle due to the creep phenomenon was greater than in the C-A'' bottle of the present invention.

Example 4 Using the co-injection apparatus described in Example 1, the polyethylene terephthalate (PET) described in Example 1 was injected into the inner layer and outer layer injection machines, and the polyethylene terephthalate (PET) described in Example 1 was injected into the intermediate layer injection machine.
Same <f described in Example 1! J-m-xylylene adipamide (Nu 6) was supplied respectively. And, ■Setting temperature of injection machine for inner layer and outer layer: Rear; 280℃
, Middle part: 280°C, Nozzle part: 285°C ■ Setting temperature of the injection machine for the middle layer: Rear part: 250°C.

Middle part: 250℃, nozzle part: 260℃■ Hot runner nozzle part temperature = 285℃ Under each temperature condition, a part of molten PET is injected into the cavity from the inner layer injection machine at the initial stage of injection, and then The molten PET is injected from the injection machine for the inner layer and the injection machine for the outer layer, and the molten M is injected from the injection machine for the middle layer.
XD 6 was simultaneously injected, the inner layer injection machine and the intermediate layer injection machine were stopped at the end of the injection, and the molten PET was injected only from the outer layer injection machine, so that the weight was 60.39 and the overall average wall thickness was A 3.855w+ multilayer silicone foam with two types and three layers was molded.

The obtained multilayer preform was crystallized using the biaxial stretch blow molding machine described in Example 1.
．． 9) A multilayer bottle was molded.

The shape of the tor includes a pillar-shaped convex part and a groove-shaped concave part in the strength part, as shown in Figures 1 to 3 of Japanese Patent Application No. 62-23491, and a grooved part in the bottom part. had a star-shaped concavity.

The bottle molding conditions are: glyphome temperature is 100℃ and
After heating for 0 seconds, the inner surface of the cavity was biaxially stretched in a blow mold heated to 160°C and heat set for 9 seconds. After switching the raw fluid to an internal cooling fluid (air adjusted to +5°C) and applying fluid pressure again for 10 seconds, the molding material was immediately taken out and left to cool. The stretching ratio of the meter is 2 in the longitudinal (axial) direction.
．． 2 times, and 3.3 times in the lateral (circumferential) direction, the total average wall thickness of the entire bottle excluding the mouth is approximately 0.528 m, and the thickness ratio of inner layer: middle layer: outer layer is 5:1:5 Met.

Hereinafter, this multilayer will be referred to as "D-A".

For comparison, the above-mentioned co-injection device and biaxial stretch blow molding machine were used, and JP-A-Sho! By using the conventional co-injection molding method as described in Japanese Patent No. 51-2773, a material having the same shape, wall thickness, internal volume and weight as above, and an intermediate layer (N06 layer) formed at the mouth of the bottle. , a multi-layer structure consisting of two types and three layers existing over the entire area of the shoulder, body and bottom was molded.

Hereinafter, this multilayer bottle will be referred to as "D-B".

Furthermore, for comparison, the molten PET was injected using only the inner layer injection machine of the above-mentioned co-injection apparatus, and the same shape as above was formed using the above-mentioned biaxial stretch blow molding machine. yN of PET single layer with wall thickness, internal volume and weight M)
molded. Below, the PET single layer &)le with “D-C
'

Among these three types of PET multi-layer and PET single-layer &) bottles, the PET inner layer and outer no.
However, when the intermediate layer was omitted, the in-plane orientation coefficient (L x m ) of the entire PET layer was measured. The results are shown in Table 9. The total surface area of the shoulder, body, and bottom of the bottle excluding the mouth is approximately 85012, of which the area of the highly oriented portion (in-plane orientation coefficient of 0.50 or more) is S
8 is about 80% of the whole (the average thickness of the whole part, tH
is 0.37 m), intermediate degree of orientation (in-plane orientation coefficient is 0.3
5 and 0.50) area, SM is also about 13
% (total average thickness of the part, tM is 0.85 m
), and has a low degree of orientation (in-plane orientation coefficient is 0.35 or less)
The area of the part, SL, is approximately 7 inches (the overall average thickness of the part).

1L was 1.79-).

Next, the "oxygen gas permeability" was measured for three types of bottles: "D-A", @D-B', and @D-C" according to each measurement method described in Example 1. , also 'D
A "container appearance" test was conducted on two types of bottles: -A'' and @D-B'. Furthermore, a test for the "peeling state of the bottom of the container" was conducted according to the method described below.

(1) Oxygen gas permeability: 3f above! Table 10 shows the arithmetic mean value and standard deviation value of the oxygen gas permeability obtained for &)l of class jl.

From Tables 9 and 10, middle class (MXD 6 f threat)
The multilayer &)ru [D-A], in which approximately 20% of the , there was no significant difference in oxygen barrier properties from the arithmetic mean value and standard deviation value of oxygen gas permeability, and these bottles were
It is known that it has clearly superior mA barrier properties.

(2) Appearance of the container: All 11 panelists agreed that the ``D-B'' D-B bottle, in which the middle layer exists over the entire area, was better than the ``D-A'' bottle according to the present invention. also answered, ``The degree of whitening is clearly large (i.e., defective).''

(3) Peeling condition at the bottom of the container: @D-A" and "D-B" are 65 bottles each, 85
℃ hot water was added dropwise, capped and held for 5 minutes, and then cooled with water until the tap water inside returned to room temperature (20 ℃). And those sample bottles, 3
0℃.

Leave it standing in a constant temperature and humidity chamber set at 80% RH, visually observe each sample yf bottle (5 bottles of each type) at a certain time every day, and place it near the date part at the bottom of the bottle. The number of days during which delamination (peeling) occurred was investigated.

In the @D-A' bottles according to the present invention, when observed for 35 days after being left in the constant temperature and humidity chamber, it was found that all the bottles (5
In contrast to the case of "D-B" (comparative example), delamination occurred on the bottom of the first one after 5 days, and after 35 days. , bottom peeling occurred in three out of the remaining four.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of a multilayer container of the present invention, FIG. 2 is a sectional view of a multilayer die, FIG. 3 is a sectional view of main parts of a co-injection device, and FIGS. FIG. 5 is an explanatory view showing the initial stage of injection and the middle of injection, and FIGS. 6 and 7 are explanatory views showing the operation of stretch blow molding.

Claims (1)

[Claims] (1) A multilayer container manufactured by stretch-blow molding a multilayer plastic preform manufactured by an injection molding method, in which the wall thickness of the mouth, shoulders, and bottom is greater than the wall thickness of the body; At least the body has a multilayer structure consisting of a circular outer surface layer made of thermoplastic polyester and a gas barrier thermoplastic resin intermediate layer located between both surface layers, and the gas barrier thermoplastic resin intermediate layer is an inner layer. The in-plane orientation coefficient (l+m) of the inner and outer surface layers is always present in the container part where the in-plane orientation coefficient (l+m) of the outer surface layer is 0.50 or more.
1. A biaxially oriented injection-blow molded multilayer container with improved appearance characteristics, characterized in that 0.35 or less is absent in the container portion.