JPS61259943A - Gas barriering multilayer polyester vessel and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to a stretched multilayer psysnack container and a method for producing the same, and more particularly, it relates to a stretched multilayer psysnack container and a method for manufacturing the same. The present invention relates to a biaxially stretched plastic container having a laminated structure, which has the following properties and also has excellent moisture resistance, and a method for manufacturing the same.

Furthermore, the present invention also relates to the reuse of scrap from the manufacture of containers.

1. Polyester containers manufactured using the stretch blow molding method have excellent transparency and moderate rigidity, and can be used in liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc., as well as beer, cola, etc. It has also come to be widely used in containers for soft drinks such as cider grass, carbonated drinks, fruit juices, and mineral water.

Although this stretched poly-23-chill container has superior gas barrier properties compared to general-purpose resin containers such as polyethylene and polypropylene, metal wire and glass bottles have almost zero gas permeability. Therefore, it has a non-negligible permeability to oxygen and carbon dioxide, and the shelf life of the contents is limited to a relatively short period.

In order to overcome this drawback, various proposals have been made to combine polyester with a gas barrier resin such as ethylene-vinyl alcohol copolymer to create a multilayer structure, thereby increasing the gas barrier properties of the container. There is.

In order to manufacture a stretched multilayer plastic container, it is first necessary to manufacture a preform with a multilayer structure. Various types of azure can be used, but when using any of these methods, there is a gap between the gas barrier resin such as ethylene-vinyl alcohol copolymer and the polyester layer! Because adhesiveness cannot be obtained,
There is a tendency for delamination to occur during stretch molding, or even if this is not the case, delamination may occur between the layers due to a falling #, etc., and further problems such as pinholes, cracks, and fractures T occur in the gas barrier layer.

Another problem is that it is difficult to completely enclose a gas barrier resin such as ethylene-vinyl alcohol copolymer in a continuous form in the upper part of the container without exposing it to the inner and outer surfaces of the container. When the ethylene-vinyl alcohol copolymer is exposed on the surface, the copolymer absorbs moisture and the gas barrier performance is significantly reduced.

Furthermore, in the manufacturing of preforms and the stretching process thereof, a certain proportion of defective products are produced, and it is desirable to reuse the scraps of these defective products for containers.

The inventor, Kasa, developed a container by stretch-blow molding a multilayer preform consisting of inner and outer surface layers of polyester resin and an intermediate layer of gas barrier resin such as ethylene-vinyl alcohol copolymer. During production, polyester, gas barrier resin, and scrap resin that is a mixture of polyester and gas barrier resin are used, with polyester as an inner and outer layer, gas barrier resin as an intermediate layer, and scrap resin as an intervening layer between both layers. When making a multilayer preform by co-injecting each layer, it not only becomes possible to reuse the scraps in containers, but also improves the releasability of the polyester and the gas barrier layer.
It was discovered that this scrap layer effectively acts as a moisture barrier layer.

An object of the present invention is to provide a multilayer stretched plastic container having a single layer of polyester gas barrier, which solves the above-mentioned problems, and a method for producing the same.

Another object of the present invention is to provide a multilayer elongated plastic container that can effectively utilize scrap (regrind) made of a mixture of polyester and gas barrier resin in the manufacture of containers, and a method for manufacturing the same.

Still another object of the present invention is to provide a multilayer stretched plastic container with excellent gas barrier properties, moisture resistance, and delamination properties, and a method for producing the same.

According to the present invention, there is provided a multilayer plastic container formed by stretch blow molding of a multilayer plastic preform by co-injection and having a mouth, a molecularly oriented body and a closed bottom, the container comprising: It was provided between inner and outer layers of polyester mainly composed of ethylene terephthalate units, a gas barrier resin intermediate layer, and the polyester layer and the gas barrier resin intermediate layer. and a scrap layer made of a mixture of polyester and gas barrier resin, the gas barrier resin intermediate layer and the scrap layer.

A container is provided which is characterized by complete encapsulation between the inner and outer layers.

Also according to the invention. A multilayer plastic made by co-injecting polyester mainly containing ethylene terephthalate units and a gas barrier resin to produce a multilayer preform, and then blow-stretching the multilayer preform in a blow mold at a temperature that allows stretching. In the container manufacturing method, a part of the required polyester resin is injected into an injection mold that has a cavity corresponding to the plastic form and a gate at a position corresponding to the bottom of the preform. Fill the chain resin; During, after, or for a short time after the primary injection, inject the gas barrier resin intermediate layer into the filled polyester into which the gas barrier resin has been injected; Alternatively, scrap resin consisting of a mixture of polyester and gas barrier resin is then injected, and the gas barrier resin is spread together with the scrap resin toward the tip of the cavity; before the cavity is filled with resin, the scrap resin is injected. There is provided a method characterized in that the injection of the polyester is stopped and the polyester is secondly injected to form a gas barrier intermediate layer and a scrap resin layer in the polyester, thereby forming a multilayer preform. .

i Five standing forks 2 11 The present invention will now be described in detail based on specific examples shown in the accompanying drawings.

In FIG. 1 showing the overall arrangement of the stretched multilayer plastic container of the present invention and FIG. 2 showing its partial sectional view structure,
This container l has a thick mouth part (nozzle part)2. Thin body part 3
and a closed bottom part 4, and a frustum-shaped shoulder part 5 exists between the body part 3 and the mouth part 2 to connect them.

This container has an inner surface M+6 and an outer surface layer 7 made of a polyester resin having orientation and creep resistance, and a gas barrier resin such as an ethylene-vinyl alcohol copolymer completely encapsulated therebetween. It consists of a combination of an intermediate layer 8 and a scrap resin layer 9 inserted between the intermediate layer 8 and the outer surface layer 7. The intermediate layer 8 and the scrap resin layer 9 are shown in FIG. It is clear from the above (shown as a uniform layer) that there is no mist coming out on the surface of any part of the passer wall, and that there is no mist as an intermediate layer and scrap layer throughout the bottom, body, and shoulders. Existing.

As shown in FIG. 1, the intermediate layer 8 does not exist at the tip of the mouth part 2, but the intermediate layer 8 may be present up to the vicinity of the tip of the "1 part (nozzle part) 2", or the "1 part" 2 may not include the intermediate layer 8.

In the present invention, by providing a scrap layer between the inner and outer polyester layers that have excellent creep resistance and other mechanical properties, and the gas barrier intermediate layer, it is possible to reduce the This means that scraps can be effectively used as container materials without any negative impact.

Moreover, this scrap layer is made of a composition mainly composed of polyester and containing an ethylene-vinyl alcohol copolymer used as a gas barrier.

Therefore, according to the present invention (1f), by interposing this resin composition within the polyester or between the outer layer and the gas barrier intermediate layer, the resin composition can be applied to both the polyester layer and the gas barrier intermediate layer. The effect is that the peeling resistance between the two river resin layers is significantly improved. Furthermore, it is known that the gas permeability of ethylene-vinyl alcohol copolymers to oxygen, carbon dioxide, etc. increases by one order of magnitude under high moisture absorption conditions. For this reason, ethylene-vinyl alcohol copolymer ff (in multilayer containers including a combined layer, it is necessary to take measures to prevent this ethylene-vinyl alcohol copolymer layer from absorbing moisture as much as possible). between the copolymer layer and the polyester layer.

By interposing a scrap layer of a composition containing polyester and an ethylene-vinyl alcohol copolymer, water vapor penetrating through the polyester layer is first transferred to the ethylene-vinyl alcohol dispersed in the scrap composition. It is effectively captured by the combined a component, and the tendency of the gas barrier intermediate layer to deteriorate due to moisture absorption is effectively suppressed.

Furthermore, in the container of the present invention, the intermediate layer 8 and the scrap layer 9 are completely enclosed between the inner and outer surface layers 6 and 7. There is a completely unexpected and novel fact that the state of adhesion with the inner and outer surfaces 6.7 of polyester etc. is completely maintained to an extent unexpected from normal UI bonding. That is,
As long as this container is kept in an integrated state, both resin layers exhibit a completely adhered appearance and behavior, and show no peeling phenomenon even when the container is subjected to a drop impact or is subjected to slight deformation. It was found that complete adhesion was maintained. The reason for this has not yet been elucidated, but
An intermediate layer such as ethylene-vinyl alcohol copolymer is completely encapsulated between the inner and outer surface layers of creep-resistant resin such as polyester to maintain airtightness between the two resin layers;
In connection with this, it has been found that the clamping force of the polyester inner layer and/or outer layer acts on the intermediate layer such as ethylene-vinyl alcohol concentric union, and that there is no adhesive between the thin inner polyester layer and the intermediate layer. ′p due to the molecular orientation of both resin layers.
1. This is thought to be due to the youthful effect.

Further, in the container of the present invention, the gas barrier resin layer made of ethylene-vinyl alcohol copolymer or the like is effectively stretched together with the inner and outer polyester layers, so that the molecules are oriented in the plane direction. The gas barrier of this molecularly oriented, ethylene-vinyl alcohol co-ffi combination is WJ'I! For example, the gas permeability coefficient (Po2) for oxygen becomes a small value of 1/2 to 1/5 of that of the unoriented one. Ethylene-vinyl alcohol copolymer is one of the resins that is difficult to stretch, and it is known that if it is stretched in the form of a single layer, that is, stretched under normal molding conditions, it will break (particularly Publication No. 57-42493), and
It is known that molecular orientation of the ethylene-vinyl alcohol copolymer layer can be achieved by forming a laminate in which an ethylene-vinyl alcohol copolymer is sandwiched between stretchable resin layers and stretching the laminate. However, in this case, it is essential to firmly bond the ethylene-vinyl alcohol copolymer and the stretchable resin layer, otherwise the ethylene-vinyl alcohol copolymer layer may break. In contrast, in the present invention, only the inner surface side is bonded between the ethylene-vinyl alcohol copolymer layer and the polyester layer. Even when the ethylene-vinyl alcohol copolymer layer has molecular orientation,
This was a surprising effect of the present invention. Generally, the ethylene-vinyl alcohol copolymer constituting the trunk intermediate layer is molecularly oriented so that the in-plane orientation coefficient C1+m) measured by fluorescence polarization method is 0.4 or more.

In the present invention, the fact that the ethylene-vinyl alcohol copolymer layer exists as a continuous film layer without defects was confirmed by cutting the 8th base body part in the thickness direction and peeling the copolymer layer from the polyester outer layer. be done. Also,
This separation also confirms the distribution or distribution structure of each layer and the presence or absence of a predetermined molecular orientation.

In the present invention, the scrap layer 9 is provided between the outer layer 7 and the intermediate layer 8 in the specific example shown in FIG. 2, but the scrap layer 9 may also be provided between the inner layer 6 and the intermediate layer 8 Alternatively, a scrap layer 9 may be provided between the inner layer 6 and the outer layer 7 and the intermediate layer 8, respectively, to provide a structure of five layers of three types.

-1 Polyethylene terephthalate (PET) as the inner and outer layers
is preferably used, but copolyesters mainly composed of ethylene terephthalate units and containing other polyester units may also be used as long as the wood quality of polyethylene terephthalate is not impaired. Copolymerization components for forming such a copolyester include isophthalic acid/P-β-oxybenzene, ρ aromatic acid/naphthalene 2,6-dicarboxylic acid and diphenoxyethane-4,4'-dicarboxylic acid Φ5-sodium. Dicarboxylic acid components such as sulfoiphthalic acid, adipic acid, sebacic acid or their alkyl ester derivatives, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, cyclohexanedimetatool, bisphenol A
ethylene oxide adduct, diethylene glycol,
Mention may be made of glycol components such as triethylene glycol.

The thermoplastic polyester used has an intrinsic viscosity [η] of 0.5 or more in terms of the mechanical properties of the vessel wall.

In particular, it is desirable that it be 0.6 or more. Furthermore, this polyester can also contain additives such as coloring agents such as pigments and dyes, ultraviolet absorbers, and antistatic agents.

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

The ethylene-vinyl alcohol copolymer is 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, imbutylene, etc. within a range that does not impair the barrier properties against alcohol, carbon dioxide, etc., for example, within a range of up to 3 mol%. It may contain an olefin having 3 or more carbon atoms as a comonomer component.

Molecules 11 of the ethylene-vinyl alcohol copolymer are sufficient to form a film: There is no particular restriction as long as it is F-kago, but generally a mixed solvent of 85% by weight of phenol and 15% by weight of water is used. Among them, it is preferable that the intrinsic viscosity [η] is in the range of 0.07 to 0.171/g when measured at a temperature of 30°C.

Other examples of gas barrier resins include aliphatic polyamides, aromatic polyamides, unsaturated nitrile resins, polyvinylidene chloride, and gas barrier polyesters.

In the present invention, as will be described in detail later, it is essential to form a clearly differentiated layered flow of polyester and ethylene-vinyl alcohol copolymer within the cavity of the injection mold/mold to achieve gas barrier properties. This is important in that respect. For this purpose, it is preferable to use a combination of polyester and ethylene-vinyl alcohol, in which the difference in structural viscosity index is in the range of 0.01 to 10, particularly 0.05 to 5.

As used herein, structural viscosity index is defined as 5"O above the melting point of the higher force of both resins.
This is the value determined from the flow curve of the melt at a shear rate of 100 sec1 or more, and more specifically.

The values are plotted using the vertical axis as the log value of the shear stress τ (Kg/cm) and the horizontal axis as the log value of the shear velocity f (seci). From the straight line approximated to this curve, the formula l
If the difference in the structural viscosity index is smaller than the above range, it may cause mixing of both phase fat layers during co-injection, which will be described later. This makes it difficult to form a continuous, complete layer of well-defined ethylene-vinyl alcohol copolymer in the preform. Furthermore, if the difference in the structural viscosity index becomes larger than the above range, co-injection itself tends to become difficult.

The structural viscosity index of a melt depends on the molecular weight distribution and chemical structure of the resin. In the present invention, the structural viscosity index can be adjusted by selecting the molecular weight and molecular weight distribution of the polyester and ethylene-vinyl alcohol copolymer used. The difference can be within the ranges described above.

As scrap resin (regrind), used are defective products, scraps, etc. produced in the manufacturing process of multilayer preforms and the stretch blow molding process of multilayer preforms. This scrap resin has a certain composition ratio depending on the layer structure of polyester and ethylene-vinyl alcohol copolymer. The weight ratio is 99:1 to 50:50. especially,? ) is within the range of 20:1 to 30:1.

To reuse scrap resin, crush the scrap and dry the resulting chip. That is, under conditions where the ethylene-vinyl alcohol copolymer in the Mekura+1 resin absorbs moisture, significant deterioration of the copolymer occurs during melt injection of the resin. In order to prevent this, the scrap resin is dried so that the moisture content in the scrap resin is 0.5 l% or less, 0.05% by weight or less.

This scrap resin is used for co-injection in the form of chips or after being pelletized if necessary.

1-Indicates a co-injection device used for manufacturing a single multilayer preform: J
In Figure S3, a cavity 13 corresponding to the preform is formed between the injection mold 11 and the core mold 12. There is a gate 14 at a position corresponding to the bottom of the preform of the mold 11, which passes through a hot runner nozzle 15 and a hot runner block 16 to the main injection machine 17.18.
and 29. The main injection machine 17 is for polyester injection, and is equipped with a barrel 19 and a screw 20 inside it, and the first sub-injection machine 18 is for ethylene injection.
For vinyl alcohol copolymer injection, barrel 21
and a screw 22 therein. The second sub-injection machine 29 is for scrap resin injection, and the barrel 3
0 and a screw 31 therein. The block 16 and pull 15 include a hot runner 23 with an annular cross section for polyester injection, a hot runner 24 for ethylene-vinyl alcohol copolymer injection located at the center, and a hot runner 24 located at the outermost periphery. .

The polyester injection machine has a hot runner 32 for scrap resin injection with a large diameter annular cross section, and these are coaxial and are arranged so as to meet near the tip of the pull 15. 26a to the hot runner 23, -jf ethylene-vinyl alcohol copolymer injection machine 18 sprue bush 2
The scrap resin injection machine 29 is connected to the hot runner 32 via a sprue bush 33 and a sprue 34. The resin to be injected is melted in the barrel 19 (21 or 30) and stored in the barrel 19 (21 or 30) by rotation of the screw 20 (22 or 31), and then the screw 20 (22 or 31) is advanced. Then, pour the molten resin onto the sprue 26a (28 or 34) and the hot runner 23 (23).
According to the present invention, polyester, ethylene-vinyl alcohol copolymer, and scrap resin are injected under the following conditions.

In Fig. 4 showing the relationship between injection time and injection pressure of polyester (PET) ethylene-vinyl alcohol copolymer (EVOH) and scrap resin, alpha vent symbols A-H in the figure refer to 5-A to 5-5. -) This corresponds to the explanatory diagram of Figure I.

First, advance the polyester injection screw 20,
The primary injection is made into the cavity 13 at a constant pressure. 7th
Figure -A shows the state of polyester just before injection, with polyester 35 at the tip of nozzle 15, but ethylene-
The vinyl alcohol copolymer 36 is placed at the tip of the hot runner 24, and the scrap resin 37 is placed at the tip of the hot runner 32.
They remain at the tip of each. As the polyester is injected, the cavity 13 is filled up to the middle with the primary injected polyester 35, as shown in FIG. 5-B.

At the stage when injection of a predetermined star of polyester has been completed (during injection of polyester, immediately after injection, or a short time after injection is completed), screw 22 for injection of ethylene-vinyl alcohol copolymer is turned on. advance,
Ethylene-vinyl alcohol copolymer 36 is injected into cavity 13. In this case, as shown in FIG. 5-C, the primary injection polyester 35 is solidified by contact with the mold on the surface of the cavity 13, or even if it is not solidified, it is in a state of extremely high viscosity IE. Therefore, the injected ethylene-vinyl alcohol copolymer 36 flows toward the tip of the cavity along approximately the central plane of the filled polyester layer, forming an intermediate layer of the copolymer.

In this case, it is preferable to inject the ethylene-vinyl alcohol copolymer as a solid stream, so that the ethylene-vinyl alcohol copolymer can be completely continuous as an intermediate layer.

When the injection of the ethylene-vinyl alcohol copolymer is completed or at the same time, the injection of the scrap resin 37 is started. Figure 5-D shows the state in which the injection of ethylene-vinyl alcohol copolymer has been completed and the injection of scrap resin has begun, and Figure 5-E shows the state in which the injection of scrap resin has been carried out into the cavity. This shows the initial state.

The scrap resin 37 is applied to the outer side polyester layer 35 of the cavity, as shown in FIGS. 5-F and 5-0.
The ethylene-vinyl alcohol copolymer layer 36 flows between the EL and the ethylene-vinyl alcohol copolymer 36.
At the same time, this scrap layer 37 stretches the ethylene-vinyl alcohol copolymer layer 36 toward the tip of the cavity, and also connects the ethylene-vinyl alcohol copolymer layer 36 to the outer surface of the next injected polyester. It moves forward between the layer 35a toward the tip of the cavity.

The advancement of the scrap resin 37 and the accompanying stretching of the ethylene-vinyl alcohol copolymer layer 36 are
As shown in the figure, injection of the scrap resin 37 is performed near the tip of the cavity 13, but as shown in Figure 5-0, the injection of the scrap resin 37 is stopped before the cavity 13 is filled with resin, and the injection of the polyester 38 is Secondary injection is performed, and as shown in Figure 15-H, an ethylene-vinyl alcohol copolymer intermediate layer 36 and a scrap resin layer 37 are formed.
The enlargement of the ratio near the tip of the preform is effectively performed, and the vicinity of the gate and the tip of the nozzle are filled with virgin polyester 38, and the ethylene-vinyl alcohol inside the preform! Complete containment of the combined interlayer 36 and scrap layer 37 will occur and virgin polyester will be available in the nozzle 15 for the fifth injection cycle.

In the present invention, in the embodiment shown in FIG. 5-C, the ethylene-vinyl alcohol copolymer 36 is injected alone, but
6 may be injected simultaneously as a solid stream and polyester 35 as an annular stream.

In addition, scrap resin 37 and secondary injection polyester 38
The switching is performed at an arbitrary timing, and when the switching timing is V, the stretching toward the tip of the ethylene-vinyl alcohol copolymer 36 is also performed by the secondary injection polyester.

According to the present invention, scrap resin is injected between the outer surface layer of the primary injection polyester and the ethylene-vinyl alcohol copolymer layer, and finally the polyester is secondary-injected to form the ethylene-vinyl alcohol preform. It becomes possible to spread it to the vicinity of the tip. At this time, the intermediate layer of ethylene-vinyl alcohol copolymer has a preferable distribution structure which is sufficiently thin so as to be suitable for the stretching operation and is biased towards the inner surface side of the vessel wall rather than the center plane. Further, it becomes possible to completely fit the ethylene-vinyl alcohol Jt-1 combined intermediate layer and the scrap layer between the polyesters.

In the embodiment shown in Figures 5-A to 5-H, a scrap resin layer 37 is introduced between the ethylene-vinyl alcohol copolymer layer 36 and the polyester outer layer 35a.
The vinyl alcohol copolymer intermediate layer 36 has a structure biased toward the inner surface, but the scrap resin layer 37 is
It is also possible to have a structure in which the ethylene-vinyl alcohol copolymer intermediate layer 36 is biased toward the outer surface by introducing it between the vinyl alcohol copolymer intermediate layer 36 and the polyester inner layer 35b.

That is, in this case, as shown in FIG. 7-A.

Hot runner for polyester (PET) injection in the center
23a, an annular hot runner 24a for injection of ethylene-vinyl alcohol copolymer (EVOH) on the outermost side and an annular hot runner 32a for injection of scrap polyester (scrap PET) 4% resin between them; Injection molding of @4 resin is performed at the timing shown in FIG. 6 and FIGS. 7-A to 7-H. -A to 7-
1 (the alphabets in the figure also correspond to the alphabets in the injection time chart shown in FIG. 6).

First, at the start of injection, the nozzle tip 15 is filled with virgin polyester as shown in Figure wfJ7-A, and then as shown in Figures 7-8.

Polyester CPET) 3 up to the middle of cavity 13-
Then, EVOH and rib mouth PET are simultaneously injected. At this time, as shown in Figure 7-C and Figure 7-D, the lip I"ET37 is solid flow and EVO) (
36 is injected into the cavity in an annular flow, and introduced along the center plane of the virgin PET filled layer so that the repro-PET layer 37 is on the inner surface layer side and on the six outer sides of the EVOH layer 36. The injection of the lip port PET 37 is stopped before the cavity 13 is completely filled with resin, and thereafter
VOH3B injection continues, which results in E'10H
36 is in a continuous state near the gate or the introduction part of the cavity 13 connected to it (Fig. t57-E).Finally, as shown in Fig. 7-F, secondary injection of virgin PE738 is performed and the preform is injected. Confinement with PET and filling of the nozzle tip with PET takes place.

In the present invention, the primary injection pressure of polyester is P1, the injection pressure of ethylene-vinyl alcohol copolymer is P2,
When the injection pressure of the scrap resin is Pz and the secondary injection pressure of the polyester is P4, these pressure conditions can be varied quite widely.

Generally speaking, the injection pressure P2 of ethylene-vinyl alcohol copolymer is higher than the primary injection pressure P1 of polyester.
advantageous in forming a complete continuous phase;
On the other hand, it is clear that the scrap resin injection pressure Pal and the polyester secondary injection pressure P4 are much lower than the polyester primary injection pressure P1, and this is advantageous in order to form a continuous intermediate layer.

It is desirable that P + *P 2 , P 3 , and P a have the following relationship.

P+=80 to 80Kg/c layer? (gauge pressure).

P2 = 80 to 11 (1.2 to 1.8 times the pressure of 1 P in IKs/c Peng2 (gauge pressure).

P3 Pa = 20 to 50Kg/c pus? (gauge pressure) and 0.3 to 0.8 times the PI.

In the present invention, it was a particularly surprising new finding that the injection of scrap resin and the secondary injection of polyester proceed smoothly with a pressure lower than that of the primary injection. The exact reason for this is unknown, but the scrap resin and secondary injection polyester pass through the molten resin with low resistance, and the molten ethylene-vinyl alcohol copolymer comes into contact with the scrap resin and secondary injection polyester. It is thought that this acts as a lubricant to facilitate the flow of the secondary injection polyester.

In the co-injection molding method used in the present invention, it is natural that the injection amount of the ethylene-vinyl alcohol copolymer is related to the thickness of the intermediate layer of the ethylene-vinyl alcohol copolymer. is related to the thickness of the inner surface layer of polyester, and the amount of scrap resin injection and the amount of secondary injection of polyester are related to the degree of deviation of the ethylene-vinyl alcohol copolymer intermediate layer from the center in the thickness direction of the preform toward the inner surface side. closely related to

In the present invention, since the ethylene-vinyl alcohol copolymer intermediate layer is quite thin compared to the overall thickness, the cavity volume is V, the primary injection capacity of the polyester is vl, and the secondary injection capacity of the polyester is V2,
vs injection capacity of ethylene-vinyl alcohol copolymer
, when the injection capacity of scrap resin is v4, VC is 1 to 20% of V, especially 5 to 10%, and Vl is 5.
30%, especially 10 to 20%, v3 1 to 5
0%, especially 4-8%, v4 10-70%, especially 2
It is desirable to set it to 0 to 40%.

That is, when the value of vs is smaller than the above range, it tends to be difficult to significantly improve the gas barrier properties of the container, and when the value of v3 is larger than the range L, the stretching of the preform tends to be difficult. If the eVl ratio is smaller than the above range, which causes the disadvantages of reduced blowing characteristics and increased container costs, the fatal disadvantage of exposing the ethylene-vinyl alcohol copolymer to the preform surface occurs. On the other hand, if the ratio of 1/1 is larger than the above range, it becomes difficult to spread the ethylene-vinyl alcohol copolymer as an intermediate layer over substantially most of the area of the preform. If the value of v2 is smaller than the above range, it will likely become difficult to fit the ethylene-vinyl alcohol copolymer layer and the scrap resin layer.

According to the method of the present invention, the thus obtained multilayer preform having the structure shown in FIG. 5-H or FIG. 7-F is subjected to stretch blow molding. Prior to this stretch blow molding, the multilayer preform is first maintained at the temperature at which polyester can be stretched, generally from 80 to 135°C, particularly from 90 to 125°C. This temperature control process involves supercooling the polyester layer of the multilayer preform so that it is maintained in a substantially non-crystalline state (amorphous state), and then using a heating mechanism known per se such as hot air, an infrared heater, and a high-frequency dielectric heated grass. The multilayer preform can be heated to the above temperature, or the multilayer preform may be cooled or allowed to cool in the injection mold or within the mold until the temperature of the multilayer preform reaches the above temperature. It can also be done by

8 and 9 for explaining the stretch blow molding operation, a mandrel 41 is inserted into the mouth of a bottomed multilayer preform 40, and the mouth is inserted into a pair of split molds 42.
It is held between a and 42b. A vertically movable stretching rod 43 is provided coaxially with the mandrel 41, and this stretching rod 43
An annular passage 4 for fluid injection is provided between the mandrel 41 and the mandrel 41.
There are 4.

The tip 39 of the stretching rod 43 is placed inside the bottom of the preform 45, and by moving the stretching rod 43 downward, the stretching is performed in the axial direction, and the Nifi body inside the preform 40 is drawn through the passage 44. is sucked in, and the preform is stretched 11 degrees in the mold by this fluid pressure.

The degree of stretching of the preform is sufficient to impart molecular orientation, which will be described in detail later, but for this purpose, the stretching ratio in the axial direction of the container must be 1.2 to 10 times, particularly 1.5 to 10 times. It is desirable to increase the number by 5 times.

The molecular orientation of the polyester layer can be easily confirmed by a fluorescence polarization method, a birefringence method, a density method, etc., and can be easily evaluated by a density method. Generally speaking, the density of preester at 20°C in the thinnest part of the body is 1.34 to 1.39.
g/cm3, especially 1.35 to 1.38 g/c113
If it is within the range of , it can be concluded that the molecular orientation is being carried out effectively.

Since the container of the present invention has the above-mentioned excellent properties, it is useful as a container for various contents, especially as a lightweight container that blocks the permeation of oxygen, carbon dioxide gas, or fragrance components, such as beer, cola.

As a container for cider, carbonated fruit juice drinks, carbonated alcoholic beverages, etc., it has the advantage of significantly less carponation loss compared to known containers.

and-1 The invention is illustrated by the following example.

Example 1 Using the injection molding machine shown in Fig. 3,
Co-injection molding of multilayer preforms was performed at the injection timings shown in Figures 5-5 to 5-H.

First, dried virgin polyethylene terephthalate (PET) with an intrinsic viscosity of 1.0 is supplied to the main injection machine 17, and dried virgin polyethylene terephthalate (PET) with an ethylene content of 70 mol% is supplied to the first sub-injection machine 18. Pellets of ethylene-vinyl alcohol copolymer (CEVOH) were supplied.

Scrap material from multilayer preforms and stretched bottles containing an average of 97% polyethylene terephthalate and 3% by weight ethylene-vinyl alcohol copolymer was chipped to an average chip size of 2". The chips were dried to a moisture content of Q,01% or less, and then supplied to a second sub-injection molding machine.

A bottomed preform having a multilayer structure of 3 types and 4 layers with a wall thickness of 3.51 layers was manufactured using the injection pressure and injection time as shown below.

PET primary injection pressure 100 Kg/cm2 hours 6 seconds EVOH injection pressure 120 Kg/cm2 hours 4 seconds Scrap resin injection pressure 100 Kg/cm2 hours 3 seconds PET primary injection pressure 60 Kg/cm2 hours 0.5 seconds.

The obtained multilayer preform was preheated to a temperature of about 11.0° C. and biaxially stretched blow molded to double the length and quadruple the circumferential direction to produce a multilayer bottle with an internal volume of 1500 c.

The resulting multilayer bottle has a body, bottom and shoulders made of PET.
It has a layer structure of outer layer/scrap resin/EVOH intermediate layer/PET inner layer, and from the results of an iodine adsorption test on the inner and outer surfaces of the bottle, the EVOH layer and scrap resin layer are
It was confirmed that no mist was emitted from the inside and outside of the bottle, and that the bottle was completely encapsulated.

Furthermore, the volume fraction of the scrap resin layer in this multilayer preform, and hence the multilayer bottle, was 40%, indicating that the scrap resin can be effectively used for manufacturing the multilayer bottle.

The results of filling this bottle with tap water and subjecting it to a drop impact test from a height of 1.5 volumes, as well as the results of filling it with carbonated water at a pressure of 4 kg/cra2 and storing it for 14 days, showed no tendency to peel off at all. There wasn't.

Comparative Example 1 For comparison, a three-layer multilayer bottle was manufactured in the same manner as in Example 1 except that PET was secondarily injected instead of the scrap resin.

For each multilayer bottle of Example 1 and Comparative Example 1 obtained, 3
Oxygen permeability at 7°C, RHO%, 37°C, 100
The oxygen permeability was measured under the condition of %RH, and the obtained results are shown in Table 1. In addition, in a drop impact test of containers filled with tap water from a height of 1.5 m, the number of containers that suffered damage or delamination was compared.

Furthermore, 20 panelists were used to judge the appearance characteristics, and the number of people who judged the appearance to be good was expressed.

The results are shown in Table 1.

Table 1

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a plastic container according to the present invention, FIG. 2 is an enlarged sectional view of the container of FIG. 1, and FIG. 3 is a co-injection machine used in the manufacturing method of the present invention. This is a sectional view of main parts. Fig. 4 is a time chart of co-injection, and Fig. 5-, Fig. 5-A, Fig. 5-B, Fig. 5-C, Fig. 5-I), Fig. 5-E, Fig. 5-F, FIG. 5-0, FIG. 5-H, and an explanatory diagram illustrating the state of injection of each resin into the cavity in relation to FIG. 4, and a time chart showing another aspect of co-injection in FIG. can be. Figure 7-A, Figure 7-B, Figure 7-C, Figure 7-D, Figure 7-E, and Figure 7-F are related to Figure 6. FIG. 3 is an explanatory diagram showing an injection state. FIGS. 8 and 9 are explanatory diagrams of a stretch blow molding process of a multilayer preform. l is the plastic container, 2 is the neck, 3 is the body, 4 is the bottom,
5 layer parts, 6 is a polyester inner layer, 7 is a polyester outer layer, 8 is an ethylene-vinyl alcohol copolymer intermediate layer, 9
is the scrap resin layer. 11 is an injection mold, 12 is a core mold, 17.18°29 is an injection machine, 23.24.32 is a hot runner-135,3
9 is a polyester, 36 is an ethylene-vinyl alcohol copolymer, 37 is a scrap resin, 40 is a preform, 42&, 42b is a blow mold. Figure 4 Figure 8 Figure 9

Claims (8)

[Claims] (1) A multilayer plastic container formed by stretch blow molding of a multilayer plastic preform by co-injection and having a mouth, a molecularly oriented body, and a closed bottom, the container being made of polyester mainly containing ethylene terephthalate units. a gas barrier resin intermediate layer,
A scrap layer made of a mixture of polyester and gas barrier resin is provided between the polyester layer and the gas barrier resin intermediate layer, and the gas barrier resin intermediate layer and the scrap layer are provided between the inner and outer layers. A container characterized by being completely enclosed. (2) Claim 1, wherein the scrap layer is provided between the polyester outer layer and the gas barrier intermediate layer.
Containers listed in section. (3) Claim 1, wherein the scrap layer is provided between the polyester inner layer and the gas barrier intermediate layer.
Containers listed in section. (4) The container according to claim 1, wherein the gas barrier resin is an ethylene-vinyl alcohol copolymer. (5) The container according to claim 1, wherein the scrap layer comprises a composition containing polyester and gas barrier resin in a weight ratio of 50:50 to 99:1. (6) Manufacturing a multilayer preform by co-injecting a polyester mainly composed of ethylene terephthalate units and a gas barrier resin, and blow stretch-molding this multilayer preform in a blow mold at a temperature that allows stretching. In the method for manufacturing a multilayer plastic container, an injection mold having a cavity corresponding to the plastic form and a gate at a position corresponding to the bottom of the preform,
A part of the required polyester resin is injected to fill the cavity halfway with the resin; during, after, or a short time after the primary injection, the filled polyester resin is injected with a gas barrier resin. A gas barrier resin is injected into the cavity; at the same time or subsequently, a scrap resin made of a mixture of polyester and a gas barrier resin is injected, and the gas barrier resin is spread together with the scrap resin toward the tip of the cavity. stop the scrap resin injection before the cavity is filled with resin, and perform a secondary injection of the polyester to encapsulate the gas barrier intermediate layer and the scrap resin layer in the polyester, thereby forming the multilayer preform. A method characterized by forming. (7) The method according to claim 6, wherein the gas barrier resin is injected in the form of a solid stream, and the polyester and the scrap resin are each injected in the form of annular streams. (8) The method of claim 6, wherein the polyester is injected in the form of a solid stream and the ethylene-vinyl alcohol copolymer and the scrap resin are injected in the form of an annular stream.