JPH059259B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a heat and pressure resistant multilayer container and a method for manufacturing the same, and more particularly, the present invention relates to a heat and pressure resistant multilayer container and a method for manufacturing the same, and more specifically, the container is equipped with an inner and outer layer of polyethylene terephthalate and an intermediate layer of a gas barrier thermoplastic resin, and has gas barrier properties and heat and pressure resistance. This invention relates to a stretch-blow molded container with excellent combinations and a manufacturing method thereof. (Conventional technology) Polyester containers made by stretch blow molding are
With excellent transparency and moderate rigidity, it can be used not only for liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc., but also for containers for carbonated drinks such as beer, cola, cider, and soft drinks such as fruit juice and mineral water. It has come into widespread use. Although this stretched polyester container has superior gas barrier properties compared to general-purpose resin containers such as polyethylene and polypropylene, the gas permeability of cans and bottles is almost zero, while the gas permeability of cans and bottles is almost zero. It has permeability to carbon dioxide and carbon dioxide gas,
The shelf life of the contents is limited to a relatively short period. In order to improve this drawback, the gas barrier properties of the container can be improved by combining polyester with a gas barrier resin such as ethylene-vinyl alcohol copolymer or xylylene group-containing polyamide to create a multilayer structure. Various proposals have been made. 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. It has been known. (Problems to be Solved by the Invention) However, multilayer containers made by conventional injection molding/stretch blow molding methods are still insufficient for use in sterilizing or sterilizing them with hot water after filling with contents that have an autogenous pressure. It wasn't satisfying. In other words, it is extremely difficult to hot-fill contents such as carbonated beverages that have autogenous pressure due to their nature. Therefore, sterilization or sterilization operations to improve the shelf life of the contents are difficult to perform inside the container. Fill the contents,
After sealing, the bottled product is subjected to hot water sterilization, or sterilization, in which the bottled product is showered with hot water in a device called a pasteurizer. However, when a multilayer container made by injection molding/stretch blow molding is subjected to hot water sterilization or sterilization, the container wall is subjected to both heat and internal pressure, causing expansion and deformation, resulting in poor appearance characteristics of the container. This may cause the container to become loose, break the adhesion to the base cup provided for the self-support of the container, or reduce the self-supporting nature of the container itself. Therefore, the object of the present invention is to provide a container that has a combination of excellent gas barrier properties and excellent heat and pressure resistance, and that after filling and sealing the contents with its own pressure, it can be subjected to sterilization or sterilization using hot water. An object of the present invention is to provide a stretch-blow-molded multilayer container and a method for producing the same. (Means for Solving the Problems) According to the present invention, in a multilayer container formed by stretch-blow molding a multilayer preform manufactured by an injection molding method, the center of the mouth and bottom wall is made up of ethylene terephthalate units. The container is made of a single layer of thermoplastic polyester mainly composed of a thermoplastic polyester, and at least the body of the container, excluding the mouth and the center of the bottom wall, has an inner layer and an outer layer made of the thermoplastic polyester, and is located within the inner and outer layers. The center of the mouth and bottom wall is thick and has a crystallinity as determined by the density method.
25% or more, and the portion of the container excluding the mouth and the center of the bottom wall is rapidly stretched and thinned through the stepped portion adjacent to the mouth and bottom wall,
Further, there is provided a heat and pressure resistant multilayer container characterized in that the molecules are oriented so that the orientation crystallinity as measured by X-ray diffraction is 10% or more. According to the present invention, a multilayer preform comprising an inner and outer layer of thermoplastic polyester mainly composed of ethylene terephthalate units and an intermediate layer of gas barrier thermoplastic resin located between the inner and outer layers,
A method for manufacturing a multilayer container comprising stretch blow molding in a blow mold at a temperature that allows stretching,
The thermoplastic polyester corresponding to the inner and outer layers and the gas barrier thermoplastic polyester corresponding to the intermediate layer are injected at a later time in the early stage of injection and later in the final stage of injection compared to the injection timing of the thermoplastic polyester. The mouth and bottom of the preform are essentially made of polyester, and the rest of the preform is made of inner and outer layers of polyester and gas barrier thermoplastic. A preform made of a resin laminate is produced, and the mouth and bottom of the preform are crystallized by heat treatment prior to stretch blow molding so that the degree of crystallinity as determined by the density method is 25% or more. A method of making a heat and pressure resistant multilayer container is provided. (Function) The heat-pressure resistant multilayer container of the present invention is manufactured by a combination of co-injection molding and stretch blow molding. During co-injection, thermoplastic polyester is used for the inner and outer layers, and gas barrier properties are used for the intermediate layer. The thermoplastic polyester is co-injected into the injection mold in a parallel manner by controlling the injection timing of the gas barrier thermoplastic resin to be slower at the beginning of the injection and earlier at the end of the injection compared to the injection timing of the thermoplastic polyester. The first feature is that it can be ejected. That is, by using this co-injection method, a preform can be manufactured in which the mouth and bottom of the preform are substantially made of polyester, and the other parts are made of inner and outer layers of polyester and a laminate of a gas barrier thermoplastic resin. becomes possible. Next, the second feature is that the mouth and bottom of this preform are crystallized by heat treatment prior to stretch blow molding so that the degree of crystallinity determined by the density method is 25% or more, particularly 28% or more. By heat-treating the preform prior to stretch-blow molding, it is possible not only to highly crystallize only a limited specific part of the preform, that is, only the mouth and bottom, but also to reduce the crystallization of the mouth and bottom. This makes it possible to achieve a high degree of thinning and a high degree of oriented crystallization by stretching other parts. The heat and pressure resistant multi-layer container of the present invention has a mouth and a center part of the bottom wall made of a single layer of thermoplastic polyester mainly composed of ethylene terephthalate units, and the inside of the container excluding the center part of the mouth and bottom wall. A cross-sectional structural feature in that at least the body portion is made of a laminate of an inner layer and an outer layer made of the thermoplastic polyester, and an intermediate layer made of a gas barrier thermoplastic resin located between the inner and outer layers; a mouth portion and a bottom wall portion; A stepped portion that has a thick center, is crystallized so that the degree of crystallinity determined by the density method is 25% or more, and that the portion other than the center of the mouth and bottom wall of the container is adjacent to the mouth and bottom wall. It has a combination of crystallographic features such as being rapidly thinned by stretching through the film, and molecularly oriented so that the degree of orientation crystallinity as measured by X-ray diffraction is 10% or more. During stretch blow molding of a polyester preform, the neck portion of the preform held by the mold and the center portion of the bottom portion supported by the stretching rod remain unstretched, that is, unoriented, and the adjacent portions also have low orientation. remain in the state. The situation is the same in the case of multilayer containers with polyester as the inner and outer layers and gas barrier resin as the middle layer. The less oriented portions are stretched, causing expansion and deformation of the container. Conventionally, in order to prevent thermal deformation of a stretched blown polyester container, it is already known to thermally crystallize the unstretched neck and bottom center portions. However, it has been found that if this thermal crystallization means is simply applied to a multilayer container, satisfactory heat and pressure resistance cannot be obtained. That is, the gas barrier thermoplastic resin used as the intermediate layer is polyester (PET).
Since it is used as a heat transfer barrier layer, either the inner layer or the multi-layer is not sufficiently crystallized due to poor heat conduction, and therefore the condition where both heat and pressure act on it. Deformation easily occurs at the bottom. Table 1 below shows the thermal conductivity of various resins.

[Table] * Ethylene-vinyl alcohol copolymer According to the present invention, the gas barrier thermoplastic resin layer with low temperature conductivity is removed from the mouth and the center of the bottom, and these parts are formed from a single polyester layer. This allows good heat conduction throughout these parts during heat treatment, making it possible to sufficiently thermally crystallize these parts, and preventing deformation or deformation of these parts during hot water sterilization or sterilization. Expansion can be almost completely suppressed. In addition, by sufficiently thermally crystallizing the mouth and the center of the bottom so that they are not deformed (not stretched), the stretching start point is fixed at a position adjacent to this thermally crystallized area during stretch blow molding. Rapid thinning by stretching and high degree of molecular orientation are possible from the position through the stepped portion, and the occurrence of thermal deformation and expansion due to residual low orientation portions can also be effectively eliminated. (Preferred Embodiment of the Invention) In FIG. 1, which conceptually shows a simplified cross-sectional structure of a multilayer die used in the method of the present invention, the multilayer die 1 includes a polyester solid stream corresponding to the inner surface layer of the multilayer preform. channel 2, an outer annular channel 3 for polyester corresponding to the outer surface layer of the multilayer preform, and an inner annular channel 4 for gas barrier resin corresponding to the middle layer (gas barrier resin layer) of the multilayer preform between them. are provided, and these channels 2, 3 and 4 open into a single hot runner nozzle 5 which is connected to an injection mold gate (not shown). In the present invention, 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 the injection mold through the channels and gates of the hot runner. In this specification, "translationally injecting" means that each resin is injected simultaneously through each channel in a uniform state, and therefore means that the flow rate ratio between each resin is constant. . Furthermore, in the present invention, the injection timing of the gas barrier resin for the intermediate layer is controlled so that it starts later at the beginning of the injection and ends earlier at the end of the injection compared to the injection timing of the polyester for the inner and outer surface layers. Therefore, according to the present invention, since the injection flow rate of the polyester for the inner surface layer and the injection flow rate of the polyester for the outer surface layer are maintained constant throughout substantially the entire injection process, the formed The ratio of the thicknesses of the outer and inner surface layers of the preform will remain substantially equal wherever the intermediate layer is present. For example, if the thickness of the outer surface layer at the center of the torso is A, the thickness of the outer surface layer at the bottom is A', the thickness of the inner surface layer at the center of the torso is B, and the thickness of the inner surface layer at the bottom is B', The relationship of the formula A/B≒A'/B' holds true, and in particular, it is also possible to set A=B and A'=B'. Of course, since the injection flow rate of the gas barrier resin is constant, the thickness (C) of the intermediate layer is also constant at any part of the preform. In addition, by shifting the injection start point of the gas barrier resin for the intermediate layer slightly later, it is possible to prevent the gas barrier resin from being exposed at the uppermost opening of the preform, and furthermore, the injection end point of the gas barrier resin can be slightly delayed. By shifting the preform quickly, the bottom part of the preform corresponding to the gate can be formed only of polyester, thereby preventing exposure of the gas barrier resin. Note that 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 with either the polyester for the inner surface layer or the polyester for the outer surface layer, or both. You can also go by. As a preferred example, the pre-injection is carried out with polyester for the inner surface layer and the post-injection is carried out with polyester for the outer surface layer. In FIG. 2, which shows the schematic arrangement of the apparatus used to carry out the method of the present invention, an injection machine 6 for the inner layer polyester, an injection machine 7 for the outer layer polyester, and an injection machine 8 for the intermediate layer gas barrier resin are provided. Each of these injection machines is connected via their respective tip nozzle 6a, 7a, 8a to a corresponding runner 6b, 7b and 8b of the hot runner block 9, respectively. The hot runner nozzle 5 has a solid flow path 2 for the inner layer polyester at the center, an annular inner annular flow path 4 for the central layer gas barrier resin around the solid flow path 2, and an outer annular flow path 3 for the outer layer polyester around the outer periphery. are located, and these channels are arranged to merge near the hot runner nozzle tip 10. In the multilayer die shown in FIG. 2, the first solid channel 2 corresponds to the injection of the inner layer of the preform, the inner annular channel 4 corresponds to the injection of the center layer of the preform, and the outer annular channel 3 corresponds to the injection of the outer layer of the preform. be. Although only one hot runner nozzle is shown in the hot runner block 9, it should be understood that a plurality of hot runner nozzles may be provided. A cavity mold 11 is provided above the block 9 and is integrally fastened thereto. The cavity mold 11 has a cavity 12 whose axis extends in the vertical direction, and this cavity 12 is connected via a gate 13 to the hot runner nozzle 5 of the block 9. Naturally, the number of cavities 12 corresponding to the number of hot runner nozzles 5 are provided in parallel. A core 14 that defines the inner surface of the preform during molding and a neck gripping split mold (not shown) that defines the outer periphery of the preform mouth during molding are provided to be combined with this cavity mold 11 during injection molding. In the present invention, polyester terephthalate can be suitably used as the thermoplastic polyester (hereinafter sometimes simply referred to as PET) for the inner and outer layers, but as long as the essence of polyethylene terephthalate is not impaired, the main component is ethylene terephthalate units. However, copolyesters containing other polyester units may also be used. Copolymerization components for forming such a copolyester include isophthalic acid/ρ-β-oxyethoxybenzoic acid, naphthalene-2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5- Dicarboxylic acid components such as sodium sulfoisophthalic acid, adipic acid, sebacic acid or their alkyl ester derivatives, propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-
Glycol components such as hexylene glycol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, diethylene glycol, and triethylene glycol can be mentioned. In terms of the mechanical properties of the vessel wall, the thermoplastic polyester used has an intrinsic viscosity (IV) as described below.
It is desirable that it is 0.5 or more, especially 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. Any known gas barrier resin can be used as the gas barrier resin for the intermediate layer. In one embodiment of the present invention, an ethylene-vinyl alcohol copolymer having a vinyl alcohol content of 40 to 85 mol%, particularly 50 to 80 mol% is used as the intermediate gas barrier resin layer. That is,
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. Vinyl alcohol content is 40
When the content is less than mol%, 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. If it exceeds 85 mol%, the water vapor permeability increases and the melt moldability decreases, which is not suitable for the purpose of the present invention. 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, especially 99% or more. In addition to the above components, this copolymer may contain up to 3 mol% of carbon atoms such as propylene, butylene-1, isobutylene, etc., within a range that does not impair the gas barrier properties against oxygen, carbon dioxide, etc. It may contain three or more olefins as comonomer components. The molecular weight of the ethylene-vinyl alcohol copolymer is not particularly limited as long as it has a molecular weight sufficient to form a film, but it is generally used at a temperature of 30°C in a mixed solvent of 85% by weight of phenol and 15% by weight of water. Intrinsic viscosity (IV) is 0.07 to 0.17/g as measured by
It is good that it is within the range of . In another embodiment of the invention, a xylylene group-containing polyamide is used as the gas barrier resin for the intermediate layer. What is xylylene group-containing polyamide?
A polyamide containing m-xylylene diamine and/or p-xylylene diamine as a diamine component, more specifically 35 mol% of the diamine component.
Above, especially 50 mol% or more is m-xylylene and/or
or p-xylylene diamine, in which the dibasic acid component is an aliphatic dicarboxylic acid and/or an aromatic dicarboxylic acid, optionally containing up to 25 mol%, especially up to 20 mol% of ω-aminocarboxylic acid per total amide repeating unit. Contains 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:
Examples of the aromatic dicarboxylic acids include adipic acid, sebacic acid, and suberic acid, and examples of aromatic dicarboxylic acids include terephthalic acid and isophthalic acid. Further, examples of the ω-aminocarboxylic acid component include ε-caprolactam, aminoheptanoic acid, aminooctanoic acid, and the like. Examples of xylylene group-containing polyamides include, but are not limited to, polymethaxylylene adipamide, polymethaxylylene sebacamide, polymethaxylylene sveramide, m-xylylene/p-xylylene adipamide copolymer, These include m-xylylene adipamide/isophthalamide copolymer, m-xylylene adipamide/isophthalamide/ε-aminocaproic acid copolymer, and the like. The xylylene group-containing polyamide used preferably has a relative viscosity (ηrel) of 0.4 to 4.5, measured using 96% by weight sulfuric acid at a concentration of 1 g/100 ml and a temperature of 25°C. Yet another embodiment of the invention uses gas barrier polyesters. This is a type of gas barrier polyester (hereinafter sometimes referred to as BPR).
contains a terephthalic acid component (T) and an isophthalic acid component (I) in the polymer chain in a molar ratio of T:I=95:5 to 5:95, particularly 75:25 to 25:75, and It contains an ethylene glycol component (E) and a bis(2-hydroxyethoxy)benzene component (BHEB) in a molar ratio of E:BHEB=99.999:0.001 to 2.0:98.0, particularly 99.95:0.05 to 40:60. As BHEB, 1,
3-bis(2-hydroxyethoxy)benzene is preferred. The T・I/E・BHEB copolyester (BPR) used in the present invention exhibits an oxygen permeability coefficient (PO ₂ ) on the order of about 1/3 to 1/4 that of polyethylene terephthalate, and the oxygen permeability coefficient The advantages are that there is almost no dependence, thermoforming is more stable than with other gas barrier resins, and the adhesion to polyethylene terephthalate is extremely good. Of course, the gas barrier polyester (BPR) used in the present invention may contain small amounts of other dibasic acid components and other diol components without impairing its essence; for example, p-
Oxycarboxylic acids such as β-oxyethoxybenzoic acid, naphthalene 2,6-dicarboxylic acid, diphenoxyethane-4,4'-dicarboxylic acid, 5-sodium sulfoisophthalic acid, adipic acid, sebacic acid, or these Dicarboxylic acid components such as alkyl ester derivatives, glycol components such as propylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexylene glycol, cyclohexanedimethanol, and ethylene oxide adducts of bisphenol A, etc. May contain. 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 a weight ratio of 60:40. 0.3 to 2.8 dl/g, especially 0.4 to 1.8 dl/g
It is desirable to have an intrinsic viscosity [η] of Among these, those with a relatively low molecular weight are used for injection molding, and those with a relatively high molecular weight are used for extrusion molding. Other examples of gas barrier polyesters include polyethylene naphthalate, particularly those in which the naphthalene dicarboxylic acid component consists of 2,6-naphthalene dicarboxylic acid. The gas barrier resin for the intermediate layer illustrated above is
It can be used alone or in the form of a mixture of two or more. Furthermore, in order to improve the adhesion to the inner and outer polyester layers, the intermediate layer can be injected by supplying a dry blend or melt blend with the adhesive resin to an intermediate layer injection machine.
Suitable examples of adhesive resins are aliphatic polyamide resins, especially copolyamides such as nylon 6/nylon 6,6 copolymer. The adhesive resin can be used in an amount of 1 to 100 parts by weight, particularly 5 to 50 parts by weight, per 100 parts by weight of the gas barrier resin. First, during injection molding, each injection machine, hot runner block, and injection mold are in the state shown in FIG. At this position, the screw of the inner layer injection machine 6 moves forward, and a small amount of polyester resin is injected into the cavity 12 through the nozzle 6a, the inner layer resin runner 6b, the solid channel 2 in the hot runner nozzle, and the gate 13. With a slight delay in timing, the screws of the outer layer injection machine 7 and the screws of the middle layer injection machine 8 are advanced. As a result, the outer layer resin is transferred to the nozzle 7a, the runner 7
b. The middle layer resin is supplied to the hot runner nozzle tip 10 through the outer annular flow path 3, and the intermediate layer resin is supplied to the nozzle 8.
a, runner 8b, and is supplied to the hot runner nozzle tip 10 through the inner annular flow path 4. In FIG. 3, which shows the initial stage of injection, only the tip 15 of the resin flow is made of polyester, and consists of a solid polyester flow 2a, an annular flow 4a of gas barrier resin around it, and an annular polyester flow 3a around it. A multilayer resin flow is formed at the nozzle tip. Next, the fourth image shows a state in which injection has progressed.
In the figure, this multilayer resin flow flows into an orifice in the injection mold, and the polyester solid flow 2a forms the preform inner surface layer 16 and the polyester outer annular flow 3.
It can be seen that a represents the outer surface layer 17 and the gas barrier resin inner annular flow 4a represents the preform intermediate layer 18. Furthermore, by finishing the injection of the gas barrier resin before the cavity 12 of the injection mold is filled with resin, the gas barrier resin can be removed from the bottom, and the bottom can be made of a single layer of polyester. . In FIG. 5, which shows the thus obtained multilayer preform and the subsequent crystallization heat treatment process, the multilayer preform 20 has a test tube-like shape as a whole, and includes a mouth portion 21, a cylindrical body portion 22, and a closed bottom portion 2.
Consists of 3. The mouth portion 21 is formed from a single layer of polyester, and is provided with a cap fastening screw 24 and a support ring 25 around the periphery. The body 22 consists of a polyester inner surface layer 16, a gas barrier resin intermediate layer 18, and a polyester outer surface layer 17, and the bottom 23 consists of a single polyester layer. The polyester of the resulting multilayer preform 20 is in a supercooled state and is substantially amorphous. During the crystallization heat treatment of this multilayer preform, the multilayer preform 20 is inserted into a cylindrical shield 26. The mouth 21 projects upward from the upper end 27 of the shield 26 and is exposed, and at least the center of the bottom 23 is exposed through a hole 27 provided in the bottom of the shield 26. A mouth heating heater 28 is provided above the upper end of the shield 26.
A heater 29 for heating the bottom is provided corresponding to the hole 30 provided at the bottom. Thus, the mouth 21 and bottom 23 of the preform 20 are connected to the heater 28.
and 29, and a predetermined thermal crystallization progresses. In the present invention, the thermal crystallization of the mouth part 21 and the bottom part 23 has a crystallinity (X _c ) of 25% or more by the density method,
In particular, thermal crystallization is performed to achieve a concentration of 28 to 60%. The degree of crystallinity is measured as follows. An n-heptane-carbon tetrachloride density gradient tube (manufactured by Ikeda Rika Co., Ltd.) was prepared, and the density of the sample was determined at 20°C. Thereby, the degree of crystallinity is calculated according to the following formula. Crystallinity X _c = ρ _c / ρ・(ρ − ρ _an ) / (ρ _c − ρ _an
)×100 ρ: Measured density (g/cm ³ ) ρ _an : Amorphous density (1.335 g/cm ³ ) ρ _c : Crystal density (1.455 g/cm ³ ) This thermal crystallization is generally carried out at 120 to 230°C, especially
This can be done by heating the mouth and bottom at a temperature of 130 to 210° C. for 5 seconds to 10 minutes, especially 15 seconds to 7 minutes. After thermal crystallization and prior to stretch blow molding, the multilayer preform is first heated to the stretchable temperature of the main resin layer, i.e. the stretching temperature of polyester, generally 80 to 135°C.
In particular, maintain the temperature between 90 and 125°C. In this temperature control process, the polyester resin layer in the body of the multilayer preform is supercooled to maintain a substantially non-crystalline state (amorphous state), the mouth and bottom are thermally crystallized, and then heated using hot air and infrared rays. This can be done by heating the multilayer preform to the above temperature using a heating mechanism known per se, such as a heater or high-frequency dielectric heating. In FIGS. 6 and 7 for explaining the stretch blow molding operation, a mandrel 21 is inserted into the mouth of a bottomed multilayer preform 20, and the mouth is held between a pair of split molds 32a and 32b. A stretching rod 33 that is vertically movable coaxially with the mandrel 31
is provided, and between this stretching rod 33 and the mandrel 31 there is an annular passage 34 for fluid suction. The tip 35 of the stretching rod 33 is applied to the inside of the bottom part 23 of the preform 20 and the stretching rod 33 is moved downward to perform tension stretching in the axial direction and to blow fluid into the preform 20 through the passage 34. The container 40 is formed by expanding and stretching the preform within the mold using this fluid pressure. The degree of stretching of the preform is sufficient to impart molecular orientation to at least the main resin layer,
For this purpose, it is desirable that the stretching ratio in the axial direction of the container be 1.2 to 10 times, particularly 1.5 to 5 times. FIGS. 8 and 9 show an example of the multilayer container of the present invention.
In the figure, the container 40 includes a mouth portion 41, a shoulder portion 42,
Consists of a trunk wall part 43 and a bottom wall part 44, and a mouth part 41
The thickness of the center portion 45 of the bottom wall portion 44 is the same as that of the body wall portion 43.
The thickness of the preform 20 is larger than that of the preform 20, and is generally approximately the same as the thickness of the preform 20. Torso wall part 43
An inner surface layer 46 and an outer surface layer 47 made of thermoplastic polyester having a substantially uniform thickness ratio, and an intermediate layer made of a gas barrier thermoplastic resin located between the inner surface layer 46 and the outer surface layer 47. 48 are laminated to form a multilayer structure. The mouth part 41 has a single-layer structure consisting only of thermoplastic polyester, and is thermally crystallized so that the density method crystallinity (X _c ) is 25% or more, and its crystal structure is spherulite-like. (lamellar).
The center portion 45 of the bottom wall portion 44 also has a single layer structure made of only thermoplastic polyester, and has a crystallinity _Xc of 25.
% or more, it is also thermally crystallized.
The fact that the mouth portion 41 and the center portion 45 are thermally crystallized and has a spherulite shape can be confirmed by the whitening of these portions, and the fact that they are substantially unoriented can be confirmed by X-rays. This can be confirmed by the appearance of a halo using diffraction techniques. In the container of the present invention, the portions of the container other than the mouth 41 and the bottom center 45 are rapidly stretched and thinned through the step 49 adjacent to the mouth and the step 50 adjacent to the bottom center, respectively. In addition, the molecules are oriented so that the orientation crystallinity as measured by X-ray diffraction is 10% or more, particularly 13% or more. Note that the upper and lower ends 51 of the gas barrier resin intermediate layer 48 provided on at least the body wall portion 43, excluding the mouth portion 41 and the bottom center portion 45, are located above the stepped portion 4.
9, 50, or may be adjacent to the stepped portion 4.
It may be slightly away from 9.50. The thickness of the body wall portion 43 varies depending on the polyester and gas barrier resin used, but is generally 0.3 to 0.8 mm, and the thickness of the intermediate layer 48 of the body wall portion 43 varies depending on the polyester and gas barrier resin used.
The thickness of the inner surface layer 46 is 0.03 to 0.1 mm, and is 5 to 15% of the thickness of the body wall 43, and the ratio of the thickness of the inner surface layer 46 to the outer surface layer 47 is 1:0.5 to 2. It is preferable that The thickness of the bottom wall portion 44 is greater at the center than at its periphery, and preferably the thickness at the center is 3 to 10 times the thickness of the body wall 43. In addition, in FIGS. 8 and 9, the bottom wall portion 4
4 shows a shape that bulges outward, but the center part may be recessed inside the container 40,
It may also have a flat shape. The container of the present invention can be used as a filling container for carbonated alcoholic beverages such as beer, cider, sparkling wine, and wine coolers, carbonated beverages containing fruit juice; carbonated dairy drinks, nitrogen-filled fruit juice drinks, and nitrogen-filled refreshing or recreational drinks. can. Hot water sterilization or sterilization treatment is
This can be carried out by immersion in hot water or by showering with hot water using hot water at a temperature of 100°C. (Effects of the Invention) According to the present invention, the gas barrier thermoplastic resin layer with low temperature conductivity is removed from the center of the mouth and the bottom, and these parts are formed from a single polyester layer, so that the heat treatment is easy. Heat conduction is good throughout these parts, making it possible to sufficiently thermally crystallize these parts, and almost completely suppressing deformation and expansion of these parts during hot water sterilization or sterilization. can do. In addition, by sufficiently thermally crystallizing the mouth and the center of the bottom so that they are not deformed (not stretched), the stretching start point is fixed at a position adjacent to this thermally crystallized area during stretch blow molding. Rapid thinning by stretching and high degree of molecular orientation are possible from the position through the stepped portion, and the occurrence of thermal deformation and expansion due to residual low orientation portions can also be effectively eliminated. Furthermore, due to the presence of the gas barrier resin layer in the thin body, which occupies most of the container surface, gas permeation through the container wall can be suppressed to an extremely low level. (Example) Intrinsic viscosity 0.8 for inner layer injection machine and outer layer injection machine
Polyethylene terephthalate (PET) will be supplied to the intermediate layer injection machine, and polymethaxylylene adipamide (PMR) will be supplied as a gas barrier resin to the injection machine for the intermediate layer. At the beginning of injection, a part of molten PET is injected into the cavity from the inner layer injection machine, then molten PET is simultaneously injected from the inner layer injection machine and outer layer injection machine, and molten PMR is simultaneously injected from the middle layer injection machine. At the final stage, molten PET is injected from the inner layer injection machine and the outer layer injection machine to form a 4 mm thick product whose mouth and bottom are made only of polyethylene terephthalate, whose inner and outer layers of the body are the PET, and whose middle layer is the PMR. A multilayer preform with two types and three layers was molded. The mouth of the preform thus obtained was heated for about 3 minutes at a mouth crystallization device using a far-infrared heater at a mouth surface temperature of 160°C, and then allowed to cool naturally to crystallize. I went there. Next, using a bottom wall center crystallization device using a far-infrared heater, the bottom wall center was heated for about 2 minutes at a surface temperature of 160° C., and then allowed to cool naturally to effect crystallization. This multilayer preform was heated to approximately 100℃ and biaxially stretched blow molded to double the length and four times the width, resulting in a weight of 52.
A multilayer bottle with an internal volume of about 1500 c.c. was obtained (hereinafter, this bottle will be referred to as A). For comparison, the multilayer preform, in which only the mouth part was crystallized under the above conditions and the center part of the bottom wall was not crystallized, was subjected to two-time stretch blowing under the above conditions, and the weight was 52 g and the internal volume was approximately A 1500 c.c. multilayer bottle was obtained (hereinafter this bottle will be referred to as B). The inner layer of the body of these two types of bottles, A and B:
The middle layer:outer layer thickness ratio is 4.5 at the top of the bottle body.
0.9:4.6, 4.5:1:4.5 in the middle of the torso, and 4.5 in the lower part of the torso.
The ratio was 4.4:0.8:4.6, and the position and thickness ratio of the intermediate layer were almost uniform in each part of the bottle. Further, the degree of crystallinity of the mouth of bottle A determined by the density method was 39.5% (wall thickness 2.13 mm), and the crystallinity degree of the center of the bottom wall was 37.0% (wall thickness 2.0 mm).
On the other hand, the mouth crystallinity for bottle B is 37.0%.
(thickness: 2.15mm), crystallinity at the center of the bottom wall is 2.7%
(wall thickness 3.72mm). Furthermore, the degree of oriented crystallinity at a position approximately 10 mm upward from the crystallized end in the center of the low wall portion, determined by X-ray diffraction, was 17.4% for bottle A (wall thickness
0.4mm), 1.6% for B bottle (wall thickness 2.85mm)
It was hot. In addition, the degree of oriented crystallinity at a position 5 mm downward from the crystallized end of the neck determined by the above X-ray diffraction method is 21.9% for bottle A (wall thickness 0.41 mm).
The B bottle was 24.1% (wall thickness 0.43mm). On the other hand, the degree of orientational crystallinity in the center of the body is 22.6% for the outer layer and 22.9% for the inner layer in bottle A;
In bottles, the outer layer is 24.1% and the inner layer is 24.4%.
It was hot. After filling the two types of bottles A and B with fruit juice-containing carbonated drinks (gas volume = 2.5) with a mouth head space of 25 c.c., they were sterilized using a pasteurizer. The sterilization conditions in the pasteurizer are as follows: The first tank is at 40℃ for 3 minutes, the second tank is at 72℃ for 25 minutes, and the third tank is at 72℃ for 25 minutes.
66℃ for 10 minutes, 4th tank at 40℃ for 3 minutes, 5th bath at 20℃
It is 10 minutes. The highest temperature reached at the lowest point of the liquid temperature of the filled product in the pasteurizer was 71°C, and the temperature was maintained at 65°C or higher at the same position for 13 minutes. When the two types of bottles, A and B, were examined for deformation after the pasteurization, the total height of the bottles was found to be +2.0 mm for A and +8.0 mm for B than the height before treatment. Regarding the independence of the bottles, all 10 bottles of A were good, while 8 out of 10 bottles of B were poor. As is clear from the above results, by crystallizing the center of the bottom wall, the mouth, etc., the deformation of the bottle, especially the bottom of the bottle, due to pasteurization treatment is extremely small, and the deformation of the bottle after pasteurization treatment is Good results were obtained in terms of the upward elongation of the bottle and the self-supporting nature of the bottle.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the multilayer die, Fig. 2 is a sectional view of main parts of the co-injection device, Figs. 3 and 4 are explanatory diagrams showing the initial stage and middle of injection, and Fig. 5 is the preform. 6 and 7 are explanatory diagrams showing the stretch blow molding operation. FIG. 8 is a sectional view of the container.
The figure is a partially enlarged sectional view of the bottom of the container of FIG. 8. 1... Multilayer die, 2... Solid channel, 3... Outer annular channel, 4... Inner annular channel, 5... Hot runner nozzle, 6... Injection machine for inner layer, 7... For outer layer Injection machine, 8... Injection machine for intermediate layer, 11... Cavity type, 13... Gate, 14... Core, 20...
Preform, 26... Shielding plate, 28, 29...
Heating heater, 40... Container, 41... Mouth part,
44...bottom.

Claims (1)

[Scope of Claims] 1. A multilayer container formed by stretch-blow molding a multilayer preform manufactured by an injection molding method, wherein the mouth and the center of the bottom wall are made of a single layer of thermoplastic polyester mainly composed of ethylene terephthalate units. At least the body of the container, excluding the mouth and the center of the bottom wall, is composed of an inner layer and an outer layer made of the thermoplastic polyester, and an intermediate layer made of a gas barrier thermoplastic resin located in the inner and outer layers. The center of the mouth and bottom wall of the container is thick and crystallized to have a crystallinity of 25% or more according to the density method. The parts other than the part are rapidly thinned by stretching through the step part adjacent to the mouth part and the bottom wall part, and the molecules are oriented so that the orientation crystallinity as measured by X-ray diffraction is 10% or more. A heat and pressure resistant multilayer container characterized by: 2. A multilayer preform consisting of an inner and outer layer of thermoplastic polyester mainly composed of ethylene terephthalate units and an intermediate layer of gas barrier thermoplastic resin located between the inner and outer layers is stretch-blown in a blow mold at a temperature that allows stretching. In the manufacturing method of a multilayer container, which involves molding, thermoplastic polyesters corresponding to the inner and outer layers and gas barrier thermoplastic polyesters corresponding to the intermediate layer are formed, and the injection timing of the gas barrier thermoplastic resin and the injection timing of the thermoplastic polyester are adjusted. The preform is co-injected into the injection mold in parallel so that it is slow at the beginning of the injection and fast at the end of the injection, so that the mouth and bottom of the preform are substantially made of polyester, and the other parts are made of polyester. A preform is produced, which consists of inner and outer layers of polyester and a laminate of a gas barrier thermoplastic resin, and the mouth and bottom of the preform are stretch blow molded so that the degree of crystallinity as determined by the density method is 25% or more. A method for producing a heat-pressure-resistant multilayer container, characterized by crystallizing it by prior heat treatment.