JPH0446736B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a gas barrier multilayer plastic container, and more specifically, it has a combination of excellent gas barrier properties and delamination resistance, and
The present invention relates to a method of manufacturing a blow-molded multilayer plastic container useful as a sealed storage container. (Prior Art) Blow-molded plastic containers are widely used for various purposes as containers for hermetically storing contents. BACKGROUND OF THE INVENTION Multilayer containers, which are combined into layers, are widely used as containers for hermetically storing cosmetics, various liquids or paste seasonings, various beverages, and the like. To manufacture a 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. Are known. (Problems to be Solved by the Invention) Gas barrier resins such as ethylene-vinyl alcohol copolymers are sensitive to humidity and their gas barrier properties drop significantly when they absorb moisture. It is desirable to seal it between the inner and outer surface layers of the plastic resin. Furthermore, since gaff barrier resins such as ethylene-vinyl alcohol copolymers have almost no thermal adhesiveness to olefin resins, it is necessary to interpose an adhesive resin layer between both resin layers. Otherwise, delamination will easily occur due to drop impact or the like. A method has already been proposed in which a gas barrier resin layer is sandwiched with an adhesive resin layer and then co-injected, but this method not only requires an adhesive resin injection machine but also requires a complicated nozzle and hot tinner structure. Furthermore, it is difficult to match the timing of injection of both resin layers, which may cause significant unevenness in the thickness of both resin layers within a multilayer preform, or in severe cases, may cause cases where both resin layers do not spread throughout the preform. do. Therefore, the present invention does not require an injection machine for adhesive resin, and a preform is formed by injecting between the inner and outer polyolefin layers while the gas barrier resin layer is reliably sandwiched with the adhesive resin layer. As a result, the present invention provides a method for producing a stretched multilayer plastic container that has excellent gas barrier properties and delamination resistance and is useful as a pressure-resistant container. (Means for Solving the Problems) That is, the present invention consists of inner and outer surface layers mainly made of olefin resin, and at least one intermediate layer of gas barrier thermoplastic resin sealed between the inner and outer surface layers. A multilayer plastic preform consisting of
A method for producing a multilayer plastic container comprising blow molding in a blow mold at a moldable temperature, injecting an olefin resin until the cavity in the injection mold is halfway filled with the olefin resin; (A) Vinyl alcohol content is 40 or more
A core of a gas barrier resin selected from the group consisting of 85 mol% ethylene-vinyl alcohol copolymer and xylylene group-containing polyamide, or a blend of the ethylene-vinyl alcohol copolymer and the xylylene group-containing polyamide; , (B) an acid- or acid-anhydride-modified olefin resin, or () having a melting point or refractory point that is at least 3°C lower than the melting point of the gas barrier resin;
A composite pellet consisting of the modified olefin resin and an adhesive resin sheath made of a blend of the olefin resin is melted and then injected into the injection mold to form a pellet between the inner and outer surface layers of the olefin resin. An adhesive resin layer was formed between the gas barrier thermoplastic resin layer and the olefin resin inner and outer layers, and finally the olefin resin was injected to seal the gas barrier layer. The present invention relates to a method for manufacturing a multilayer plastic container, characterized by forming a multilayer preform. (Function) In the present invention, an ellalene-vinyl alcohol copolymer or xylylene group-containing polyamide is used as a gas barrier resin and a specific acid- or acid anhydride-modified polyolefin is used as an adhesive. The remarkable feature is that a composite pellet with a sheath of agent resin is used, and that the composite pellet is melted and then injected between the inner and outer layers of the olefin resin. That is, according to the present invention, a gas barrier thermoplastic resin layer and a gas barrier thermoplastic resin are injected between the inner and outer surface layers of the olefin resin while injecting the gas barrier resin, adhesive resin, etc. with a single injection machine. It becomes possible to form an adhesive resin layer between the layer and the inner and outer olefin resin layers. That is, by forming a distribution structure in advance into pellets with a gas barrier resin as a core and an adhesive resin as a sheath, a melt blend or dry blend of both resins is fed to an extruder and injected. Compared to the case where the gas barrier resin layer and the adhesive resin layer are clearly separated, it is easier to form the gas barrier resin layer and the adhesive resin layer in a sandwiched state. In general, as a measure of the compatibility of multiple resins, for example, "Polymer
The solubility index (SP value) is known as described in "Handbook" Chapter 4 (published by J. Wiley & Sons Inc., 1967). Vinyl alcohol copolymers generally have an SP value of 9.9 to 11.7, and xylylene group-containing polyamides generally have an SP value of 11.5 to 13.6. These resins generally have an SP value of 8.0 to 9.2, and there is a considerable difference in SP value between gas barrier resins and adhesive resins. In addition, as another measure to express the degree of mixing of multiple resin melts, the shear stress τ (Kg/cm ² ) and shear rate γ (sec ^-1 ) for each resin melt are considered to be two factors. Under certain processing conditions, if the apparent melt viscosities of the resins are close to each other, the resin melts tend to mix, and if the two melt viscosities are different, they tend to separate. In the present invention, the acid- or acid anhydride-modified olefin resin used as the adhesive is an ethylene-vinyl alcohol copolymer or xylylene group-containing resin used as the gas barrier resin. Compared to polyamide, it generally has a higher apparent melt viscosity at high shear rates,
Moreover, in the injection method used in the present invention, the shear rate during melt extrusion is generally 50 to 500 sec ^-1 , but it is as high as 700 to 3000 sec ^-1 , and the apparent melt viscosity in such a high shear rate region is This difference is considered to be the second reason why a clearly divided layered distribution structure is formed between the two resins. In the present invention, the melting point or softening point of the acid or acid anhydride-modified olefin resin that is the adhesive resin [in this specification, the melting point or softening point refers to the melting point or softening point of the resin at a heating rate of 10°C/min When it has a clear melting point (here, the temperature corresponding to the melting endothermic peak obtained by the above-mentioned DTA method) as determined by differential thermal analysis (DTA method), it is called the melting point (MP). If not, the softening point (Sof P,
(based on ASTM D-648 or ASTM D-1525)] is limited to a temperature that is at least 3°C closer than the gas barrier resin.
The first reason is adhesiveness, and the second reason is to facilitate the formation of the core sheath. (Preferred Embodiment of the Invention) Material The olefin resin (hereinafter sometimes simply referred to as polyolefin) used in the present invention is as follows:
Any polyolefin that is conventionally widely used for forming films, sheets, etc. can be used. Such polyolefins include, for example, the formula In the formula, each of R ₁ and R ₂ is a hydrogen atom, an alkyl group having 4 or less carbon atoms, or an aryl group. monoolefins, especially ethylene, propylene,
butene-1, pentene-1,3-methylbutene-
Homopolymers or copolymers of 1,2-methylpentene-1,4-methylpentene-1 and styrene can be used. In order for these olefin polymers or copolymers to have sufficient mechanical strength when formed into a film, it is generally important that they be crystalline. Suitable examples of such polyolefins include low, medium or high density polyethylene (PE), isotactic polypropylene (PP), crystalline ethylene-propylene copolymer (EPC), polybutene-1, polypentene-1,
Mention may be made of poly4-methylpentene-1 (P4MP1). Of course, the polyolefin resin that can be used in the present invention is not limited to a homopolymer of olefin or a copolymer of two or more olefins, and may contain a small amount of other materials as long as the properties of the polyolefin are not essentially lost. Copolymer component, e.g. 15 mol%
It may also contain other ethylenically unsaturated monomers, such as vinyl chloride, vinyl acetate, allylic acid ester, methacrylic ester, etc., within the above range. Suitable examples of such copolymers include ethylene vinyl acetate copolymers, ethylene acrylate copolymers, ionically crosslinked olefin copolymers (ionomers), and the like. The olefin resin used is generally 0.05 to 50, especially
Melt flow rate from 0.1 to 40 (ASTMD-
1238) is desirable. Furthermore, this olefin resin can also contain additives such as coloring agents such as pigments and dyes, ultraviolet absorbers, and antistatic agents. In addition, in order to prevent the barrier property of the barrier resin from deteriorating due to moisture absorption, a drying agent such as calcium chloride disclosed in Japanese Patent Application No. 56-55455, or The vinyl alcohol/acrylic acid (salt) block copolymer and other highly water-absorbing resins described in Publication No. 59-126371 are used as olefin resin
It can be added in an amount up to 50 parts by weight. In one embodiment of the present invention, the gas barrier resin layer has a vinyl alcohol content of 40 to 85%.
It is important to use mol %, especially 50 to 80 mol % of the ethylene-vinyl alcohol copolymer.
That is, the ethylene-vinyl alcohol copolymer is
It is one of the resins with the best gas barrier properties,
Its gas barrier properties and thermoformability depend on the vinyl alcohol unit content. When the vinyl alcohol content is less than 40 mol%, the permeability to oxygen and carbon dioxide gas 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 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-mentioned components, this copolymer may contain, for example, 3
Propylene, butylene, up to mol%
1. An olefin having 3 or more carbon atoms such as isobutylene may be contained as a comonomer component. 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. It is preferable that the intrinsic viscosity [η] is in the range of 0.07 to 0.17/g. In another embodiment of the invention, xylylene group-containing polyamides are used as gas barrier resins. The xylylene group-containing polyamide is a polyamide containing m-xylylene diamine and/or p-xylylene diamine as a diamine component,
More specifically, 35 mol% or more, particularly 50 mol% or more of the diamine component is m-xylylene and/or:-
xylylene diamine, in which the dibasic acid component is an aliphatic dierboxylic acid and/or an aromatic dicarboxylic acid, optionally containing up to 24 mol%, especially up to 20 mol%, of ω-aminocarboxylic acid units per total amide repeating unit. including. Diamine components other than xylylene diamine include aliphatic diamines such as hexamethylene diamine, alicyclic diamines such as piprazine, and examples of aliphatic dicarboxylic acids include:
Adipamic acid, sebacic acid, suberic acid, etc., and aromatic dicarboxylic acids such as terephthalic acid,
Examples include isophthalic acid. In addition, as the ω-aminocarboxylic acid component, ε-caprolactam,
Examples include aminoheptanoic acid and aminooctanoic acid. 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 (ηre) 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. Further, the weight ratio of the above-mentioned ethylene-vinyl alcohol copolymer (a) and the above-mentioned xylylene group-containing polyamide (b) is a:b=95:5 to 5:95, particularly a:b=80:20 to Blends having a composition of 10:90 can also be used as gas barrier resins. Adhesive Resin In the present invention, an olefin resin graft-modified with an ethylenically unsaturated carboxylic acid or its anhydride is used as the adhesive resin. The olefin resins that are the backbone polymers include those mentioned above, especially polyethylene, polypropylene, ethylene-propylene copolymers, and ethylene-propylene copolymers.
Examples include vinyl acetate copolymer, a blend thereof, and the like. Suitable examples of ethylenically unsaturated carboxylic acids include, for example, Japanese Patent Application No. 47-60297.
Suitable examples of acid anhydrides include acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc. as described in Japanese Patent Application No. 47-83157 and others. These include maleic anhydride, itaconic anhydride, and tetrahydrophthalic anhydride. Moreover, after using these ethylenically unsaturated carboxylic acids or acid anhydrides as essential components, it may be further modified with acrylic acid amide, methacrylic acid amide, maleimide, or the like. The acid or acid anhydride is preferably 0.01 to 5% by weight of the olefin resin. Instead of using a graft-modified olefin resin alone,
Graft-modified olefin resin can also be blended with unmodified olefin resin, and even in the case of this blend, it is suitable as long as the amount of modification of acid or acid anhydride per whole is within the above range. results. In addition, in order to prevent the barrier property of the barrier resin from deteriorating due to moisture absorption, a drying agent such as calcium chloride described in the above-mentioned Japanese Patent Application No. 56-55455, or a patent application Vinyl alcohol/acrylic acid (salt) block copolymer and other super absorbent resins disclosed in Publication No. 126371/1984 may be added in an amount of up to 50 parts by weight per 100 parts by weight of adhesive resin. It is possible. Manufacture of composite pellets Except for the fact that the core is made of gas barrier resin and the sheath is made of adhesive resin, composite pellets have the following features:
It can be manufactured by a method known per se. For example, a composite pellet can be produced by coating the surface of a pellet made solely of a gas barrier resin with an adhesive resin solution by dipping or spray coating. Also, the special application 1987-
As described in Japanese Patent No. 190795, composite pellets are produced by coextruding a gas barrier resin as a core and an adhesive resin as a sheath through a multilayer die, and cutting the extruded strands. be able to. Figure 1 shows an example of a composite pellet manufacturing apparatus, in which gas barrier resin is melt-kneaded in a main extruder (core extruder) A, extruded into a strand C through a die B, and then extruded into a strand C through a sub-extruder (core extruder). Sheath extruder) Pass through crosshead die E of D. In the crosshead die E, the adhesive resin melted and kneaded in the extruder D is extruded in the form of a sheath to form a composite strand G. The composite strand G is cooled and solidified in a cooling tank F, and then cut into predetermined dimensions by a cutter H. It becomes composite pellet J. When producing composite pellets, the melting point or softening point of the adhesive resin forming the sheath layer is lower than the melting point of the gas barrier resin forming the core layer, so extrusion using a sub-extruder (sheath extruder) D, for example, is required. At this time, the resin may melt in the feed section (artificial section) of the extruder, and the discharge amount may fluctuate. In order to avoid such troubles, the feeding section (feed zone) of the sub-extruder D screw
It is necessary to take measures to prevent blocking due to melting of the adhesive resin, such as cooling the adhesive internally with hot or cold water, or installing a forced feeder in the material supply section (hopper section) of the sub-extruder D. The apparent melt viscosity of the gas barrier resin and adhesive resin used in the production of such composite pellets is within the range of 10° to 10 ⁷ poise from the above-mentioned perspective. and the ratio of the apparent melt viscosity of the gas barrier resin to the adhesive resin, dηa, is 0.001 to 0.98, especially
0.001~. It is desirable that it be in the range of 095. In this specification, the apparent melt viscosity refers to the viscosity of a melt at a shear rate of γ within the range of 700 to 200 sec ^-1 at a temperature 5°C or more higher than the melting point of the higher of both resins. This is the value obtained from ^{the flow} curve of
This is the value obtained as A in the formula τ=Aγ〓, that is, A=τ/1000. The ratio of gas barrier resin to adhesive resin can vary over a wide range, but is generally between 98:2 and 5:95.
A weight ratio of 95:5 to 20:80 is desirable in view of the combination of gas barrier properties and delamination resistance. The minimum diameter of composite pellets is 0.1
It is desirable that the thickness be in the range of 15 mm to 15 mm, particularly 0.2 to 10 mm. Manufacturing method for multilayer preform In one aspect of the present invention, in FIG. 2 showing an example of a co-injection apparatus used for manufacturing a multilayer preform, a cavity corresponding to the preform is provided between the injection mold 1 and the core mold 2. 3 is formed. A gate 4 is located at a position corresponding to the bottom of the preform of the mold 1, and is connected to two injection machines 7 and 8 via a hot runner ozzle 5 and a hot runner block 6. The main injection machine 7 is for injection of olefin resin, and is equipped with a barrel 9 and a screw 10 inside it, and the sub-injection machine 8 is for injection of composite pellets, and is equipped with a barrel 11 and a screw 12 inside it. ing. The block 6 and the nozzle 5 include a hot runner 13 with an annular cross section for injection of olefin resin, and a hot runner 1 for injection of composite pellets located at the center of the hot runner 13.
4, which are coaxial and arranged so as to merge near the tip of the nozzle 5. The sprue 15 for olefin resin injection is connected to the hot runner 13 via the sprue bush 16, while the sprue 18 for composite pellet injection is connected to the sprue bush 17.
It is connected to the hot runner 14 via.
The resin to be injected is melted in the barrels 9, 11, and the barrels 9, 11 are melted by the rotation of the screws 10, 12.
According to the present invention, the screws 10 and 12 are advanced to inject the molten resin into the cavity 3 through the sprues 15 and 18, the hot runners 13 and 14, the nozzle 5 and the gate 4. ,
Injection of olefin resin and composite pellets is carried out under the following conditions. FIG. 3 shows the relationship between injection time and injection pressure for olefin resin and composite pellets. First, screw 10 for olefin resin injection
is advanced and primary injection is performed under constant pressure into the cavity 3. The olefin resin 20 is located at the tip of the nozzle 5, while the composite pellet 21 remains at the tip of the hot runner 14. As the olefin resin is injected, as shown in FIG. 4, the primary injection olefin resin 20 is
It is filled with. At the stage where a predetermined amount of the olefin resin has been injected, that is, after the injection time _t1 has elapsed, the screw 12 for composite pellet injection is advanced and the cavity 3 is injected.
A composite pellet 21 is injected into the container. in this case,
As shown in FIG. 4, on the surface of the cavity 3, the primary injection olefin resin 20 is solidified by contact with the mold, or even if it is not solidified, the viscosity is extremely high. Therefore, the injected composite pellet 21 flows toward the tip of the cavity along substantially the center plane of the olefin resin-filled layer, but at this time, the olefin resin inner layer 20a and the olefin resin outer layer 20b and an adhesive resin layer 23a between the gas barrier resin layer 22 and the olefin resin inner and outer layers and the gas barrier resin layer.
and 23b are clearly separated. At time _t2 when the injection of the composite pellets is completed, secondary injection of the remaining olefin resin is performed. The secondary injection olefin resin 24 is applied to the olefin resin layer 2 on the outer surface of the cavity side as shown in FIG.
0b and the intermediate layer 21 containing the gas barrier resin layer, and presses the intermediate layer 21 containing the gas barrier resin toward the inner surface of the cavity, and the secondary injection olefin-based resin 24 flows into the gas barrier resin layer 21. While stretching the intermediate layer containing gas toward the tip of the cavity, the intermediate layer 21 that also contains a gas barrier resin and the primary injection olefin resin outer layer 20b are stretched.
Move forward between the two toward the tip of the cavity. In this way, the olefin resin is secondly injected between the outer surface layer of the first injected olefin resin and the intermediate layer containing the gas barrier resin, and this secondary injection causes the intermediate layer containing the gas barrier resin to form near the tip of the preform. It also becomes possible to completely confine the intermediate layer containing the gas barrier resin between the olefin resins. In the present invention, when the primary injection pressure of the olefin resin is P ₁ , the injection pressure of the composite pellet is P ₂ , and the secondary injection pressure of the olefin resin is P ₃ , these pressure conditions can be varied considerably. It was found that it can be obtained. Generally speaking, the injection pressure P ₂ of composite pellets is:
It is advantageous for the primary injection pressure P ₁ of the olefin resin to be higher than that of the olefin resin in order to mold the gas barrier resin and adhesive layer as a completely continuous phase, while the secondary injection pressure P ₃ of the olefin resin is higher than the olefin resin It has been found that satisfactory results can be obtained even if the primary injection pressure of the resin is considerably lower than P ₁ . _P1 , _P2
It is desirable that and P ₃ have the following relationship. P ₁ =50 to 500Kg/cm ² (gauge pressure). P ₂ = 55 to 550Kg/cm ² (gauge pressure) and P ₁
1.1 to 5.0 times more pressure. P ₃ = 20 to 450Kg/cm ² (gauge pressure) and P ₁
0.2 to 0.9 times the pressure. In another aspect of the invention, No. 6 illustrates another example co-injection apparatus for use in manufacturing multilayer preforms.
In the figure, a cavity 27 corresponding to a preform is formed between an injection mold 25 and a core mold 26. There is a gate 28 at a position corresponding to the bottom of the preform of the mold 25, and a hot runner nozzle 29 and a hot runner block 30.
It is connected to three injection machines 31a, 31b, and 32 via. The main injection machine 31a is for injecting olefin resin that forms the inner layer, and the barrel 33a
and a screw 34a therein,
The other main injection machine 31b is for injecting an olefin resin for forming the outer layer, and is equipped with a barrel 33b and a screw 34b inside the barrel 33b. Further, the sub-injection machine 32 is for injecting composite pellets forming the intermediate layer, and is equipped with a barrel 35 and a screw 36 inside the barrel 35. The block 30 and the nozzle 29 include a hot runner 37 with an annular cross section for injection of olefin resin forming an outer layer, a hot runner 38 having an annular cross section for injection of composite pellets forming an intermediate layer, and a hot runner 38 located at the center thereof. There is a hot runner 39 for injection of olefin resin that forms the inner layer, and these are coaxial and connected to the nozzle 2.
9 so that they merge near the tip.
Sprue 40 for off-in resin injection forming the inner layer
a is connected to the hot runner 39 via a sprue bush 41a, and a sprue 40b for injection of olefin resin forming the outer layer is connected to the sprue bush 41b.
It is connected to the hot runner 37 via.
On the other hand, a composite pellet injection sprue 42 forming the intermediate layer is connected to the hot runner 38 via a sprue bush 43. After the resin to be injected is melted in each level 35, 33a, 33b and stored in the barrels 35, 33a, 33b by the rotation of each screw 36, 34a, 34b, the screws 36, 34a, 34b are advanced, Sprue 42, 40a, 40b, hot runners 38, 37, 39, nozzle 29 and gate 28
According to the present invention, the olefin resin and composite PET are injected under the following conditions. First, the screw 34a for injection of olefin resin forming the inner layer and the screw 36 for injection of composite pellets forming the intermediate layer are advanced simultaneously or with a slight delay in the screw 36 for injection of composite pellets, and a constant pressure is applied inside the cavity 27. Shoot it below. When the olefin resin 44 and composite pellets 45 forming the inner layer move in translation through the cavity 27 and reach the middle or tip of the cavity 27, the olefin resin injection screw 34a and the composite pellet injection screw 34a forming the inner layer are removed. 36 is stopped, the screw 34b for injecting the olefin resin forming the outer layer is advanced, and the olefin resin 46 for the outer layer is injected into the cavity 27 under constant pressure. At this time, since the core mold 26 has been cooled in advance, the olefin resin 44 and composite pellets 45 that form the inner layer are separated from the core mold 26.
The olefin resin 46 for the outer layer is injected into the composite pellet 4 in the cavity 27.
5 and the injection mold 25. Then, by cooling the injection mold 25, the olefin resin 4
6 is solidified to form the outer layer as shown in FIG. In addition, at this time, as shown in the enlarged view in FIG. 4 described above, an adhesive resin layer is clearly separated and formed between the inner and outer olefin resin layers and the gas barrier resin layer in the composite pellet. . According to this aspect of the present invention, since the olefin resin injection machine 31a for forming the inner layer and the olefin resin injection machine 31a for forming the outer layer are provided separately, the inner layer or the outer layer can be injected by controlling the resin supply amount. It has the characteristic that the thickness can be freely adjusted. Of course, it goes without saying that the thickness of the intermediate layer can be adjusted by controlling the amount of composite pellets supplied. Method for manufacturing a blown multilayer container According to the method of the present invention, the thus obtained multilayer preform having the structure shown in FIG. 5 or 7 is subjected to blow molding. This blow molding can be performed by a method known as so-called in-die extension blow molding or stretch blow molding. In the former case, the multilayer preform is removed from the injection mold while hot, placed in a cooled blow mold, and molded easily by blowing high-pressure fluid into the preform.
Further, when the olefin resin is a resin capable of molecular orientation, such as polypropylene, it is also possible to perform stretch blow molding. In this case, the multilayer preform is taken out of the injection mold in a rapidly cooled state, preheated to a temperature just below the melting point of the olefin resin (generally 15°C to 5°C below the melting point), and then placed in a stretch blow mold. After mounting, it is pulled and stretched in the axial direction and expanded and stretched in the circumferential direction. In FIGS. 8 and 9 for explaining the stretch blow molding operation, a mandrel 48 is inserted into the mouth of a bottomed multilayer preform 47, and the mouth is held between a pair of split molds 49a and 49b. A stretching rod 50 that is vertically movable coaxially with the mandrel 48
is provided, and between the stretching rod 50 and the mandrel 48 there is an annular passage 51 for fluid injection. The tip 52 of the stretching rod 50 is applied to the inside of the bottom of the preform 47, and the stretching rod 50 is moved downward to perform stretching in the axial direction, and at the same time, fluid is blown into the preform 47 through the passage 51. This fluid pressure causes the preform to expand and stretch within the mold. The degree of stretching of the preform is sufficient to impart molecular orientation, but for this purpose, the stretching ratio in the axial direction of the container must be 1.2 to 10 times, especially 1.3 to 5.
It is desirable that the stretching ratio in the circumferential direction of the container be 1.2 to 15 times, particularly 1.5 to 10 times. In FIG. 10 showing the overall arrangement of the multilayer plastic container of the present invention, this container 53 has a thick mouth (nozzle) 54, a thin body 55 and a closed bottom 56. 55 and the mouth 54, there is generally a frustum-shaped shoulder 5 that contacts them.
7 is present in the case of a narrow-mouth container, but in the case of the injection blow molding described above, it is also possible not to provide such a shoulder portion 57, that is, to form a wide-mouth container. This container consists of an inner surface layer and an outer surface layer made of an olefin resin, and an intermediate layer of a gas barrier resin completely encapsulated therebetween and an adhesive sandwiching the layers. That is, this intermediate layer is not exposed to the surface at any part of the vessel wall, and is present as an intermediate layer over all of the bottom, body, and shoulders. Although there is no intermediate layer at the tip of the mouth portion 54, the intermediate layer may be present up to the vicinity of the tip of the mouth portion (nozzle portion), or the intermediate layer may not be present at the mouth portion. . (Operations and Effects of the Invention) According to the present invention described above, adhesive resin can be injected into a multilayer preform without using an injection machine for adhesive resin or requiring troublesome timing adjustment. It becomes possible to form a gas barrier resin layer with a sandwiched structure.
The container made by stretch-blow molding this preform is
It has an excellent combination of gas barrier properties and delamination resistance, and has the advantage of not causing delamination even when subjected to a drop impact, and does not cause delamination even when subjected to a drop impact. have 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. (Example) The present invention will be explained by the following example. In addition, each measurement in each Example was performed according to the following method. (1) Oxygen gas permeability QO ₂ After replacing the inside of the bottle to be measured with nitrogen gas in a vacuum and covering the contact surface between the mouth and the rubber with epoxy adhesive, the bottle was heated to a temperature of 37°C. ,
After storing for a certain period of time in a constant temperature and humidity chamber with a humidity of 20% RH, the concentration of oxygen that permeated into the bottle was determined using a gas chromatograph, and the oxygen gas permeability QO ₂ was calculated according to the following formula. Results are average values of N=3. QO ₂ = [m×Ct/100]/t×OP×A where, m: Amount of nitrogen gas filled into the bottle (ml) t: Storage period in the thermostatic chamber (day) Ct: After t days Oxygen concentration in the bottle (vol.%) A: Effective surface area of the bottle (m ² ) OP: Oxygen gas partial pressure (=0.209) (atm) (2) Drop strength: (2-1) Vertical drop strength. Fv: After filling 10 bottles of each type with a certain weight of saline solution and sealing the mouth with a cap, -2
It was left standing in an atmosphere at ℃ for two days and nights. The bottle was then dropped from a height of 100 cm at a temperature of 5°C so that the ``bottom of the bottle'' hit the concrete surface. The number of falls was repeated up to 10 times. The breakage rate was calculated from the number of bottles that remained undamaged after being dropped 10 times according to the following formula. Breakage rate (Fv) = 100 × (N-n10) / N, (%) where, N: Number of bottles tested (= 10) (bottles) n10: Number of bottles that did not break after being dropped 10 times (bottles) . (2-2) Horizontal drop strength, Fh: The number of measurement pieces, measurement method, measurement conditions, etc. are the same as in the case of "(2-1) Vertical drop strength". However, when dropping the sample, it was dropped from a height of 100 cm so that the "wall part of the bottle" hit the concrete surface. The calculation of the failure rate (in this case, Fh) is the same as in the case of "vertical drop strength" above. (3) Drop impact peeling (dynamic peel test): (3-1) Vertical drop peeling. Dv: When measuring the drop strength mentioned above, after performing the vertical drop test each time, the presence or absence of delamination of the sample bottle was visually observed. The results indicate the number of drops at which delamination was first discovered among N = 10 test pieces. (3-2) Horizontal drop separation. Dh: When measuring the drop strength mentioned above, after performing the horizontal drop test each time, the presence or absence of delamination of the sample bottle was visually observed. The results indicate the number of drops at which delamination was first discovered out of N = 10 test pieces. Example 1 Using an apparatus for manufacturing composite pellets by the sequential extrusion method as shown in Fig. 1, a main extruder (core extruder A) equipped with a full-flight screw with a diameter of 65 mm and an effective length of 1430 mm was used. , the relative viscosity ηREL is
2.24 Solubility index SP is 12.3, melting point MP by DTA method
The apparent melt viscosity A at 243℃ and 250℃ is
Polymethaxylylene adipamide with each characteristic value of 5050 poise was supplied. On the other hand, a sub-extruder (sheath extruder D) equipped with a full-flight screw with a diameter of 40 mm and an effective length of 800 mm was installed using the DTA method (heating rate: 10°C/min).
melting point, MP is 131℃, melt flow rate (ASTM D-1238), MFR is 0.3g/10min, apparent viscosity as mentioned above, A is 24500poise, density (ASTM D-1505), d is 0.942g/cc, anhydrous Maleic acid concentration, MAA is 1.04%, solubility index, SP is
12.3 maleic anhydride modified high density polyethylene was supplied. Then, composite pellets were prepared in which the core layer was made of the polymethaxylylene adipamide, the sheath layer was made of the maleic anhydride-modified high-density polyethylene, the minimum diameter was 3.5 mm, and the weight ratio of the core resin to the sheath resin was 90:10. Manufactured. The manufacturing conditions at this time are that the screw rotation speed of the main extruder (core extruder A) is
60RPM.The set temperature is 150℃ for the material supply section, 240℃ for the screw compression section, and 250℃ for the screw tip.
The screw rotation speed of the sub-extruder (sheath extruder D) was 15 RPM.The set temperatures were 130°C for the material supply section, 160°C for the screw compression section, and 160°C for the screw tip. Also, the set temperature of crosshead die E is 150.
It was warm at ℃. Next, as shown in Figure 2, the main injection machine is the FS-170N model manufactured by Nissei Jushi Kogyo Co., Ltd., and the sub-injection machine is manufactured by the same company.
Using a co-injection device consisting of each FS-75N injection machine and a prototype co-injection mold (co-injection die) manufactured by the company, the main injection machine is equipped with melt flow rate (ASTM D-1238) and MFR. High-density polyethylene (hereinafter referred to as HDPE) having a density of 0.5 g/10 min, density (ASTM D-1505), and d of 0.954 g/cc, and the above-mentioned composite pellets were respectively supplied to the sub-injection machine. As shown in Figures 3 and 4, the main injection machine temperature settings are: rear: 200°C, middle: 200°C, nozzle: 205°C. Secondary injection machine settings: Rear: 200℃, middle: 250
℃, nozzle part; 260℃. Hot runner nozzle temperature 225℃. HDPE primary injection pressure (gauge pressure): 355Kg/
cm ² , composite pellet injection pressure (gauge pressure): 460Kg/
cm ² , HDPE secondary injection pressure (gauge pressure): 240Kg/
A multilayer preform as shown in FIG. 5, weighing 35 g and having a thickness ratio of inner and outer layers to intermediate layer of 10:1, was injection molded under conditions of .cm ² . Immediately after molding, the multilayer preform was transferred to a prototype direct blow molding machine manufactured by Nissei Jushi Kogyo Co., Ltd., and blow molding was performed to obtain a full volume.
A 455ml cylindrical bottle was molded. Hereinafter, the multilayer bottle according to the present invention will be described as “ML-
1". For comparison,] a bottle made of HDPE alone (hereinafter referred to as HDPE), and a bottle made of polymethaxylylene adipamide alone as an intermediate layer (the thickness ratio between the inner and outer layers and the intermediate layer is 10). :1.Denoted as ML-X1),
and] the polymethaxylylene adipamide;
and the maleic anhydride-modified high-density polyethylene.
A bottle with an intermediate layer made of a composition dry blended at a weight ratio of 90:10 (the thickness ratio between the inner and outer layers and the intermediate layer is
10:1. It is written as ML-DB1. ) was also molded under the same conditions as before. For the four types of bottles thus obtained, oxygen gas permeability, _QO2 [cc/ ^m2・day・atm], vertical drop strength,
Fv [%], horizontal drop strength, Fh [%], vertical drop peeling,
Dv [times], horizontal drop peeling, and Dh [times] were measured. The results are shown in Table 1. As is clear from this table, the multilayer bottle ML-1 according to the present invention has a higher oxygen gas permeability and QO than the bottles made of ]HDPE, ]ML-X1, and ]ML-DB1, which were molded for comparison. _2. It is known to have particularly excellent performance in vertical drop peeling, Dv, and horizontal drop peeling, Dh.

[Table] Example 2 The main extruder (core extruder A) of the composite pellet manufacturing apparatus using the sequential extrusion method described in Example 1 had a vinyl alcohol content of 50.2 mol% and a degree of saponification.
An ethylene-vinyl alcohol copolymer having characteristic values of 99.2%, intrinsic viscosity [η] of 0.08/g, solubility index SP of 10.3, melting point MP of 160° C. by DTA method, and apparent viscosity A of 2900 poise was supplied. On the other hand, in the sub-extruder (sheath extruder D) of the composite pellet manufacturing apparatus, the MP was
MFR is 0.8g/10min, A is 18700poise, d is 0.922g/cc, MAA is 0.39%, SP is
Maleic anhydride-modified low-density polyethylene having each characteristic value of 8.1 was supplied. The core layer is made of the ethylene-vinyl alcohol copolymer, the sheath layer is made of the maleic anhydride-modified low-density polyethylene, and the minimum diameter is 1.5 mm.
Composite pellets with a weight ratio of core resin to sheath resin of 20:80 were produced. The manufacturing conditions at this time are that the screw rotation speed of the main extruder (core extruder A) is
15PRM.The set temperature is 135℃ for the material supply section, 170℃ for the screw compression section, and 165℃ for the screw tip.
The screw rotation speed of the sub-extruder (sheath extruder D) was 75 RPM.The set temperatures were 110°C for the material supply section, 140°C for the screw compression section, and 130°C for the screw tip. Also, the set temperature of crosshead die E is 130.
It was warm at ℃. Next, using the co-injection apparatus described in Example 1, low-density polyethylene (referred to as LDPE) with the MFR of 1.5 g/10 min and d of 0.919 g/cc was injected into the main injection machine, and The composite pellets were respectively supplied to the sub-injection machines. As shown in Figures 3 and 4, the set temperatures of the main injection machine are: rear: 160°C, middle: 160°C, nozzle: 165°C. Setting temperature of sub-injection machine: Rear part: 130℃, middle part: 230℃, nozzle part: 225℃. Hot runner nozzle temperature 225℃. LDPE primary injection pressure (gauge pressure): 200Kg/
cm ² , Composite pellet injection pressure (gauge pressure): 310Kg/
cm ² , LDPE secondary injection pressure (gauge pressure): 100Kg/
A multilayer preform as shown in FIG. 5 was injection molded under conditions of .cm ² , 33 g and a thickness ratio of 1:1 between the inner and outer layers and the intermediate layer. Immediately after molding, the multilayer preform was transferred to the direct blow molding machine described in Example 1, and blow molding was performed to mold a cylindrical bottle with a full fill volume of 455 ml. Hereinafter, the multilayer bottle according to the present invention will be described as “ML-
For comparison, ] the bottle made of the LDPE alone (denoted as LDPE), ] the bolt with the ethylene-vinyl alcohol copolymer as the intermediate layer (the thickness ratio between the inner and outer layers and the intermediate layer is 1). :1.ML-EV2) and] A bottle with an intermediate layer made of a composition prepared by driving the ethylene-vinyl alcohol copolymer and the maleic anhydride-modified low-density polyethylene at a weight ratio of 20:80. The thickness ratio of the inner and outer layers to the middle layer was 1:1. (Denoted as ML-DB2) was also molded under the same conditions as before. The four types of bottles obtained in this way are described in the specification. According to the method, oxygen gas permeability, QO ₂ [cc/m ²・day・atm], vertical drop strength,
Fv [%], horizontal drop strength, Fv [%], vertical drop peeling,
Dv [times], horizontal drop peeling, and Dh [times] were measured. The results are shown in Table 2. As is clear from this table, the multilayer bottle KL-2 according to the present invention is different from the molded ]LDPE, ]ML-EV2,
It is known that the performance is particularly superior to each bottle made of ML-DB2 in terms of oxygen gas permeability, QO ₂ , vertical drop peeling, Dv, horizontal drop peeling, and Dh.

[Table] Example 3 The main extruder (core extruder A) of the composite pellet manufacturing apparatus using the sequential extruder described in Example 1 had a vinyl alcohol content of 70.3 mol% and a degree of saponification.
We supplied an ethylene-vinyl alcohol copolymer having the following characteristic values: 99.6%, intrinsic viscosity [η] of 0.15/g, solubility index SP of 11.4, melting point MP of 182°C by DTA method, and apparent melt viscosity of 4500 poise. . On the other hand, the sub-extruder (sheath extruder D) of the composite pellet manufacturing equipment has a melting point MP of
159℃, melt flow rate MFR 4.5g/
10min, apparent melt viscosity is 8950poise, density d is
Maleic anhydride-modified polypropylene having characteristic values of 0.91 g/cc, maleic anhydride concentration MAA of 3.1, and solubility index SP of 8.7 was supplied. The core layer is made of the ethylene-vinyl alcohol copolymer, the sheath layer is made of the maleic anhydride-modified polypropylene, and the weight ratio of the core resin to the sheath resin is 70:30 (minimum pellet diameter: 5 mm) and 30:3, respectively. 70 (minimum diameter: 3mm), 2
Various types of composite pellets were produced. The manufacturing conditions at this time are that the screw rotation speed of the main extruder (core extruder A) is 60 RPM and 15 RPM, respectively, and the set temperature is 130 °C for the material supply section and 200 °C for the screw compression section.
℃, the temperature at the tip is 185℃, the screw rotation speed of the sub-extruder (sheath extruder D) is 40RPM, the set temperature is 140℃ for the material supply section, and the screw compression section
The temperature at the tip was 170°C. Further, the set temperature of crosshead die E was 165°C. Next, using the co-injection device described in Example 1, the melt flow rate MFR was set in the main injection machine.
An ethylene-propylene copolymer (hereinafter referred to as EPC) having a temperature of 3.0 g/10 min, a density d of 0.90 g/cc, and an ethylene content of 2 wt%, and the above-mentioned composite pellets were respectively supplied to the sub-injection machine of the same machine. As shown in Figures 3 and 4, the main injection machine setting temperature: rear: 200℃, middle part;
200℃, nozzle part; 205℃. Sub-injection machine setting temperature: Rear; 130℃, middle part;
230℃, nozzle part: 225℃. Hot runner nozzle temperature setting: 220℃. EPC primary injection pressure (gauge pressure): 220Kg/cm ² , composite pellet injection pressure (gauge pressure): 260Kg/cm ² and 280Kg/cm ² respectively, PET secondary injection pressure (gauge pressure): 190Kg/cm A multilayer preform as shown in FIG ^. 5 was molded under the following conditions: 32 g in weight and a thickness ratio of 5:1 between the inner and outer layers and the intermediate layer. Immediately after molding, the multilayer preform was transferred to the direct blow molding machine described in Example 1, and blow molding was performed to mold a cylindrical bottle with a full fill volume of 455 ml. Below, a multilayer bottle with a core/sheath resin weight ratio of 70:30 is referred to as "ML-3", and the same weight ratio is
The bulk bottle with a ratio of 30:70 is designated as "ML-4". For comparison,] a single bottle of the EPC (hereinafter referred to as EPC), a cylindrical bottle with a full fill volume of 455 ml, with the ethylene-vinyl alcohol copolymer as the middle layer (inner and outer layers and middle layer). The thickness ratio with the layer is 5:1.It is written as ML-EV1.), and]
A cylindrical shape with a full filling volume of 455 ml, with an intermediate layer made of a composition obtained by dry blending the ethylene-vinyl alcohol copolymer and the maleic anhydride-modified polypropylene at weight ratios of 70:30 and 30:70, respectively. bottles (the thickness ratio of the inner and outer layers and the middle layer are both 5:1.ML-DB3 and ML-, respectively)
It is written as DB4. ) was also molded under the same conditions as before. For the six types of bottles thus obtained, oxygen gas permeability, QO ₂ [cc/m ²・day・atm], vertical drop strength,
Fv [%], horizontal drop strength, Fh [%], vertical drop peeling,
Dv [times], horizontal drop peeling, and Dh [times] were measured. The results are shown in Table 3 (Example) and Table 4 (Comparative Example)
are shown respectively. As is clear from these tables, the multilayer bottles ML-3 and ML-4 according to the present invention
is EPC, ML-EV1, molded for comparison.
And than each bottle of ML-DB3 and ML-DB4,
It is known that the performance is particularly excellent in terms of oxygen gas permeability, QO ₂ , vertical drop peeling Dv, horizontal drop peeling, and Dh.

【table】

【table】

[Table] Example 4 The polymethaxylylene adipamide described in Example 1 was supplied to the main extruder (core extruder A) of the composite pellet manufacturing apparatus using the sequential extrusion method described in Example 1. On the other hand, in the sub-extruder (sheath extruder D) of the composite pellet production equipment, melting point
is 87℃, melt flow rate MFR is 10.1g/
10min, apparent melt viscosity A is 7650poise, density d
is 0.94g/cc, maleic anhydride concentration MAA is 7.8%,
A maleic anhydride-modified ethylene-vinyl acetate copolymer (vinyl acetate concentration: 5wt%) having a solubility index SP of 9.6 and a melting point MP of 110.
°C, melt flow rate MFR is 0.5g/10min,
The mixing ratio with unmodified low density polyethylene having the following characteristic values: apparent viscosity A of 22,000 poise, maleic anhydride concentration of 0%, and solubility index SP of 7.9 is:=
A 50:50 (weight ratio) dry blend was supplied, respectively. The core layer is made of the above-mentioned polymethaxylylene adipamide, and the sheath layer is made of a mixture of the above-mentioned and the above-mentioned, and the weight ratio of the core resin and the sheath resin is respectively
Two types of composite pellets were produced: 70:30 (minimum pellet diameter: 6 mm) and 30:70 (minimum pellet diameter: 4 mm). The manufacturing conditions at this time are that the screw rotation speed of the main extruder (core extruder A) is 70 RPM and 25 RPM, respectively, and the set temperature is 150 °C for the material supply section, 250 °C for the screw compression section, and 245 °C for the screw tip. ℃, the screw rotation speed of the sub-extruder (sheath extruder D) is 50 EPM, and the set temperature of the material supply section is 115℃.
The temperature at the compressed part of the screw was 130°C, and the temperature at the tip was 130°C. Also, the set temperature of crosshead die E is
It was 140℃. Next, in the system shown in Figure 6, the injection machines for the inner layer and the outer layer are the FS-170N model manufactured by Nissei Jushi Kogyo Co., Ltd., and the injection machine for the middle layer is the FS-75N model manufactured by the same company. Using a co-injection device consisting of a mold and a prototype co-injection mold (co-injection die) made by the same company, each injection machine for the inner layer and outer layer has a melt flow rate MFR of 5.0 g/10 min and a density d. but
A dry blend of 0.91 g/cc of isotactic polypropylene and the high-density polyethylene described in Example 1 in a weight ratio of 70:30 (denoted as PO) was also put into an injection machine for the intermediate layer. The composite pellets were each fed. And, each main injection machine setting temperature for inner layer and outer layer: Rear;
160°C, middle part: 180°C, nozzle part: 200°C Injection machine setting temperature for middle layer: rear part: 200°C, middle part: 250°C, nozzle part 260°C. Hot runner nozzle temperature setting: 255℃. PO inner layer injection pressure (gauge pressure): 150Kg/cm ² , composite pellet injection pressure (gauge pressure): 180Kg/cm ² and 200Kg/cm ² respectively, PO outer layer injection pressure (gauge pressure): 110Kg/cm ² , a multilayer preform as shown in FIG. 7 was molded, weighing 34 g and having a thickness ratio of 5:1 between the inner and outer layers and the intermediate layer. Immediately after molding, the multilayer preform was transferred to the direct blow molding machine described in Example 1, and blow molding was performed to mold a cylindrical bottle with a full fill volume of 455 ml. Below, a multilayer bottle with a core/sheath resin weight ratio of 70:30 is referred to as "ML-5", and the same weight ratio is
A multi-layer bottle with a ratio of 30:70 is designated as "ML-6". For comparison, a blend bottle of the above PP and HDPE (denoted as PO), a cylindrical bottle with a full fill volume of 455 ml, with the polymethaxylylene adipamide alone as the middle layer (inner and outer layers and middle layer). The thickness ratio of the polymethaxylylene adipamide and the above layer is 5:1 (denoted as ML-X2), and the mixture of the polymethaxylylene adipamide and the above in a weight ratio of 50:50, respectively, is 70:1.
A cylindrical bottle with a full filling volume of 455 ml, with an intermediate layer composed of a composition dry blended at a weight ratio of 30 and 30:70 (thickness ratio of the inner and outer layers and the intermediate layer is 5:1. Each ML -DB5 and ML-DB6) were also molded under the same conditions as before. For the six types of bottles thus obtained, oxygen gas permeability, QO ₂ [cc/m ²・day・atm], vertical drop strength,
Fv [%], horizontal drop strength, Fh [%], vertical drop peeling,
Dv [times], horizontal drop peeling, and Dh [times] were measured. The results are shown in Table 5 (Example) and Table 6 (Comparative Example)
are shown respectively. As is clear from these tables, the multilayer bottles ML-5 and ML-6 according to the present invention
were found to have better oxygen gas permeability, QO ₂ , vertical drop peeling, Dv, horizontal drop peeling, and Dh than the PO, ML-X2, ML-DB5, and ML-DB6 bottles molded for comparison. Known for its excellent performance.

【table】

【table】

[Table] Example 5 Using the apparatus for producing composite pellets by the coextrusion method described in Japanese Patent Application No. 57-190795,
The ethylene-vinyl alcohol copolymer described in Example 3 was fed to a core extruder (main extruder) equipped with a full-flight screw saw having a length of 65 mm and an effective length of 143 mm. On the other hand, a sheath extruder (sub-extruder) equipped with a full-flight screw with a diameter of 40 mm and an effective length of 800 mm has a melting point MP of 122°C by the DTA method, a melt flow rate MER of 2.0 g/10 min, and an apparent Melt viscosity A is 13600 poise, density d is 0.925 g/cc,
Maleic anhydride concentration MAA is 1.2%, solubility index
Maleic anhydride-modified linear low-density polyethylene (L-LDPE) having SP of 8.4 was supplied. The core layer is made of the ethylene-vinyl alcohol copolymer, the sheath layer is made of the maleic anhydride-modified linear low-density polyethylene, and the minimum diameter is 3.
mm, and the weight ratio of core resin to sheath resin was 50:50. The manufacturing conditions at this time were that the screw rotation speed of the core extruder (main extruder) was 30 RPM, the set temperature of the material supply section was 130°C,
The temperature of the screw compression section is 200℃, the tip of the screw is 200℃, the screw rotation speed of the sheath extruder (sub-extruder) is 50RPM, and the set temperature is 110℃ of the material supply section.
The temperature at the screw compression part was 160°C, and the temperature at the tip was 170°C. Further, the set temperature of the multilayer multi-die was 190°C. Next, using a prototype co-injection/biaxial stretch blow molding machine manufactured by Nissei ASB Machinery Co., Ltd., the injection machine had a melt flow rate MFR of 5.0 g/10 min.
Isotactic polypropylene (referred to as PP) having a density d of 0.91 g/cc was supplied to the sub-injection machine of the same machine, and the composite pellets were respectively supplied to the sub-injection machine of the same machine. As shown in Fig. 3 and Fig. 4, the main injection machine setting temperature: rear: 180°C, middle part;
180℃, nozzle part; 185℃. Sub-injection machine setting temperature: Rear; 130℃, middle part;
230℃, nozzle part; 225℃. Hot runner nozzle temperature setting: 225℃. Primary injection pressure (gauge pressure) for PP: 120Kg/ ^cm2 , Injection pressure (gauge pressure) for composite pellets: 150Kg/cm2
cm ² , PP secondary injection pressure (gauge pressure): 90 Kg/cm ² , the weight is 43 g, the thickness ratio of the inner and outer layers to the middle layer is 5:1, as shown in Figure 5. A multilayer preform is molded, and then in a blow zone, the multilayer preform is heated at a temperature of 156°C, with a longitudinal (axial) direction stretching ratio of 1.6 times and a transverse (circumferential) direction stretching ratio of 3.1 times. Axial stretch blowing was performed to obtain a cylindrical multilayer bottle with a full fill volume of 1020 ml. Below, this multilayer bottle will be described as “ML-
7". For comparison, the full volume of the PP single bottle (hereinafter referred to as PP) with the ethylene-vinyl alcohol copolymer alone as the middle layer is
A 1020ml cylindrical bottle (the thickness ratio of the inner and outer layers to the middle layer is 5:1. It is written as ML-EV1), and]
The ethylene-vinyl alcohol copolymer and the maleic anhydride-modified linear low-density polyethylene
A cylindrical bottle with a full fill volume of 1020 ml, with an intermediate layer made of a composition dry blended at a weight ratio of 50:50 (thickness ratio between the inner and outer layers and the intermediate layer is 5:1. ML-
It is written as DB7. ) was also molded under the same conditions as before. For the four types of bottles thus obtained, oxygen gas permeability, QO ₂ [cc/m ²・day・atm], vertical drop strength,
Fv [%], horizontal drop strength, Fh [%], vertical drop peeling,
Dv [times], horizontal drop peeling, and Dh [times] were measured. The results are shown in Table 7. As is clear from this table, the multilayer bottle ML-7 according to the present invention has a higher oxygen gas permeability and QO ₂ , Vertical drop peeling, Dv, Horizontal drop peeling,
It is known that the performance of Dh is particularly excellent.

[Table] Example 6 Stop the sub-extruder (sheath extruder D) in Fig. 1, and add UNISTOL [trade name] R-120 manufactured by Mitsui Chemicals, Ltd. (Toluene with a solid content concentration of 15 wt% of acid-modified polypropylene)
(dispersion). Then, by the main extruder (core extruder A),
The ethylene-vinyl alcohol copolymer described in Example 2 was heated at a temperature of 135°C at the material supply section, 170°C at the screw compression section, and 165°C at the screw tip.
The strand of the ethylene-vinyl alcohol copolymer is extruded at a screw rotation speed of 15 rpm, and the strand of the ethylene-vinyl alcohol copolymer is introduced into a cooling tank containing the UNISTOL R-120, and the surface of the strand is coated with the acid-modified polypropylene while also cooling the strand. I did this. And after pelleting the said strands, 80
The pellets were dried under vacuum at a temperature of .degree. C. to obtain composite pellets in which the core resin was the ethylene-vinyl alcohol copolymer and the sheath resin was the acid-modified polypropylene. The composite pellet thus obtained had a weight ratio of core resin to sheath resin of 92:8, and the minimum diameter of the pellet was about 3.8 mm. Next, using the co-injection device described in Example 1, the melt flow rate MFR was set in the main injection machine.
High-impact polystyrene (referred to as HIPS) with a density d of 2.4 g/10 min and a density d of 1.02 g/cc was supplied, and the above-mentioned composite pellets were respectively supplied to the sub-injection machine of the same apparatus. As shown in Figures 3 and 4, the main injection machine temperature settings are: rear: 150°C, middle: 170°C, nozzle: 220°C. Setting temperature of sub-injection machine: Rear part: 130℃, middle part: 230℃, nozzle part: 230℃. Hot runner nozzle temperature 225℃. Primary injection pressure (gauge pressure) for PET: 300Kg/ ^cm2 , injection pressure (gauge pressure) for composite pellets: 390Kg/cm2
cm ² , PET secondary injection pressure (gauge pressure): 180 Kg/cm ² , the weight is 36 g, the thickness ratio of the inner and outer layers to the middle layer is 20:1, as shown in Figure 5. A multilayer preform was injection molded. Immediately after molding, the multilayer preform was transferred to the direct blow molding machine described in Example 1, and blow molding was performed to mold a cylindrical bottle with a full fill volume of 455 ml. Hereinafter, the multilayer bottle according to the present invention will be described as “ML-
8". For comparison, the bottle with the HIPS alone (hereinafter referred to as HIPS) and the bottle with the intermediate layer made of the ethylene-vinyl alcohol copolymer (the thickness ratio between the inner and outer layers and the intermediate layer is 20:1, ML-
It is written as EV3. ) was also molded under the same conditions as before. For the three types of bottles thus obtained, oxygen gas permeability, QO ₂ [cc/m ²・day・atm], vertical drop strength,
Fv [%], horizontal drop strength, Fh [%], vertical drop peeling,
Dv [times], horizontal drop peeling, and Dh [times] were measured. The results are shown in Table 8. As is clear from this table, the multilayer bottle according to the present invention, ML-8, was molded for comparison with ]HIPS and ]ML-8.
It is known that the performance is particularly superior to each EV3 bottle in terms of oxygen gas permeability QO ₂ , vertical drop peeling, Dv, horizontal drop peeling, and Dh.

【table】 [Brief explanation of the drawing]

FIG. 1 shows an example of a composite pellet manufacturing apparatus. FIG. 2 shows an example of a co-injection apparatus used for manufacturing a multilayer preform. FIG. 3 shows the relationship between injection time and injection pressure for olefin resin and composite pellets. FIGS. 4 and 5 are diagrams for explaining the injection molding operation of a multilayer preform, FIG. 6 shows another example of a co-injection apparatus used for manufacturing a multilayer preform, and FIG. FIG. 10 is a diagram for explaining an injection molding operation of another example of a multilayer preform, FIGS. 8 to 9 are diagrams for explaining a stretch blow molding operation, and FIG. 10 is a diagram for explaining an entire multilayer plastic container. shows the arrangement. 1... Injection mold, 2... Core mold, 3... Cavity, 6... Hot runner block, 7...
Main injection machine, 8... Sub-injection machine, 16, 17... Sprue bush, 20... Olefin resin layer, 21
... Composite pellet, 22 ... Gas barrier resin layer, 23 ... Adhesive resin layer, 47 ... Bottomed multilayer preform, 48 ... Mandrel, 49 ... Split mold, 50 ... Stretching rod, 53 ... ... Container, 54 ... Thick mouth, 55 ... Body, 56 ... Closed bottom, 57
...Shoulder.

Claims (1)

[Scope of Claims] 1. A multilayer plastic preform consisting of inner and outer surface layers mainly made of olefin resin and at least one intermediate layer of gas barrier thermoplastic resin sealed between the inner and outer surface layers is prepared by blow molding. A method for manufacturing a multilayer plastic container comprising blow molding in a mold and at a moldable temperature,
The olefin resin is injected until the cavity in the injection mold is filled with the olefin resin, and (A) an ethylene-vinyl alcohol copolymer with a vinyl alcohol content of 40 to 85 mol% and a xylylene group-containing a core of a gas barrier resin selected from the group consisting of polyamides or a blend of the ethylene-vinyl alcohol copolymer and the xylylene group-containing polyamide; A composite pellet comprising () an acid- or acid anhydride-modified olefin-based resin having a low melting point or softening point at °C, or () a sheath of an adhesive resin made of a blend of the modified olefin-based resin and an olefin-based resin. After melting, the mixture is injected into the injection mold to form a gas barrier thermoplastic resin layer between the inner and outer olefin resin surface layers, and an adhesive between the gas barrier thermoplastic resin layer and the olefin resin inner and outer layers. A method for manufacturing a multilayer plastic container, which comprises forming a resin layer and finally injecting an olefin resin to form a multilayer preform in which a gas barrier layer is sealed.