JPS609739A - Multilayer oriented polyester bottle and manufacture thereof - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a multilayer stretched polyester bottle and a method for manufacturing the same, and more specifically, the present invention relates to a multilayer stretched polyester bottle and a method for manufacturing the same. The present invention relates to a plastic bottle with biaxial molecular orientation and a combination of excellent gas barrier properties and transparency, and a method for producing the same.

Molding of stretched polyester bottles is common today, and the resulting molded containers are used for containers for liquid products such as liquid detergents, shampoos, cosmetics, soy sauce, sauces, etc. due to their excellent transparency and suitable gas barrier properties. In recent years, it has come to be widely used in containers for carbonated drinks such as beer, cola, and cider, as well as soft drinks such as fruit juice and mineral water.

However, since stretched polyester bottles are also made of plastic, gas permeability can be considered to be zero for completely sealed items such as glass bottles and metal cans, whereas stretched polyester bottles are free from oxygen, carbon dioxide, etc. It has a slight permeability to carbon dioxide, making it inferior to cans and glass bottles in terms of food filling and storage stability, especially in the case of carbonated beverages, and in the case of beer, cola, cider, etc. It has clear storage period limits.

As a method for improving the gas barrier properties of stretched polyester bottles, coating polyvinylidene chloride resin on stretched polyester bottles has already been put into practical use, but it is of course possible to improve the gas barrier properties of stretched polyester bottles that have appropriate gas barrier properties. For this reason, it is meaningless to apply laminate II' with a resin with gas barrier properties inferior to polyester, and a resin with gas barrier properties superior to polyester must be used. Therefore, thermoplastic resins such as vinylidene chloride resins, acrylonitrile resins, and vinyl alcohol resins are candidates for gas barrier resins, but in any case, the properties and processability of each resin are different. Must be selected in relation.

The present inventor has developed a pipe forming method using coextrusion when manufacturing a multilayer stretched polyester bottle using polyester as a base and a thermoformable nitrile resin as a gas barrier layer.
By combining the pipe cutting and bottom thermoforming method and then the biaxial stretch blow molding method in this order, a multilayer stretched polyester bottle with excellent interlayer adhesion, gas barrier properties, transparency, and high molecular orientation can be obtained. I found out that it can be done.

According to the present invention, the neck part has an opening at the upper end and a fitting part or a threaded part on the outer periphery, a bottom part formed by fusing and closing the pipe or tube, and a biaxial direction by stretching and blowing the pipe or tube. The pipe or tube has an inner surface made of polyester mainly composed of ethylene terephthalate units, and/or a body with molecular orientation.
or the outer surface base layer and the acrylonitrile unit content are 50
% by weight or more and the oxygen permeability coefficient is 2x1Q"ce・cr
n/cWL" ・see -cmHy (37℃, 0%
A multilayer oriented polyester bottle is provided, characterized in that it consists of a coextrudate with a barrier layer of IJ resin.

According to the present invention, there is further provided a method for producing a multilayer stretched polyester bottle, wherein the gas barrier resin layer has an acrylonitrile unit content of 50% by weight or more and an oxygen permeability coefficient of 2×
Thermoformability smaller than 10"-1lcL-cIrL/儂2.8eC.5-cmHy (37℃, 0%RH) A pipe or tube is formed by co-extrusion using polyester resin as the main material, with an adhesive layer interposed between both side resin layers if necessary, and the pipe or tube is cut to an appropriate length. Then, one end of this pipe or tube is fused and closed to form a bottom part, and the other end is formed into a mouth part having an opening at the top and a fitting part or a threaded part on the outer periphery, to obtain a preformed product. The material is preheated to an appropriate stretching temperature of 85 to 120°C, and then heated in the axial and circumferential directions in a blow molding mold.
A method for producing a multilayer stretched polyester bottle is provided, which comprises axial stretch blow molding.

As already mentioned, the purpose of the present invention is to improve the gas barrier properties of stretched polyester bottles. And the oxygen permeability coefficient is 2×1O-11cc-・cIIL/c
A thermoformable nitrile resin smaller than rrL2.8eC.anHt (37° C., 0% RH) is used. As is known, polyacryloni? IJru (PA7V) is a resin that is difficult to thermoform, and a molding method in the form of a solution is generally employed.

When this acrylonitrile is copolymerized or blended with resin components exhibiting rubbery properties, the melting point is lowered and thermoformability is improved as the amount of these components increases. Since this nitrile resin is stretch blown together with the polyester resin, it is thought that it is better to have a low melting point and a low temperature at which it can be stretched. A nitrile resin containing 50% by weight or more and having thermoformability is used. That is, the content of acrylonitrile units is 50% by weight.
If the temperature is lower than that, the gas barrier properties against oxygen and carbon dioxide gas will rapidly decrease, making it difficult to achieve the initial objective of the present invention. In terms of content preservation, this nitrile resin has a rating of 2 x 10-"ct-cm/crIL"
5ttc-cIrLH1 or less, especially 1×10-”cc
:.

should have an oxygen permeability coefficient of less than or equal to 4 x 10-”cc-cm/cm for carbonated beverage container applications.
2・sec-anHy or less, especially 2 X I Q-”
ce I cIrL/cyn' ・sec ・ar
It is desirable to have a carbon dioxide permeability coefficient of tHy or less.

Such a thermoformable nitrile resin includes at least one copolymer of acrylonitrile and an ethylene or diolefin monomer copolymerizable with the acrylonitrile,
It consists of a graft polymer or a polymer blend and is developed using techniques known per se.

Many ethylenically or diolefinically unsaturated comonomers copolymerizable with the above-mentioned acrylonitrile are known, and suitable examples thereof are as follows.

In the formula, each of R, , R, and R is a hydrogen atom and has 4 carbon atoms.
diolefins, such as butadiene, imprene, cloprene, etc., which are an alkyl group or a halogen atom.

Formula % Formula % (2) In the formula, each of R1 and R6 is a hydrogen atom or an alkyl group having up to 4 carbon atoms, monoolefins such as ethylene, propylene, inphthylene, phthene-1, pentene-1,4-methyl Penten-1 etc.

In the formula, R is a hydrogen atom, an alkyl group having up to 4 carbon atoms, or a halogen atom, and R8 is a hydrogen atom, an alkyl group having up to 4 carbon atoms, a halogen atom, an alkoxy group, an amino group, a nitro group, a carboxyl group. Al, nomonohinyl aromatic hydrocarbons such as styrene, 9-α-methylstyrene, vinyltoluene, α-chlorostyrene, o-2m-1p-chlorostyrene, p-ethylstyrene, and the like.

Formula % Formula % (4) In the formula, Ro is a hydrogen atom or an alkyl group having up to 4 carbon atoms, R
, is a hydrogen atom, a hydrocarbon group having up to 12 carbon atoms, or a hydroxyalkyl group; Acrylic monomers such as acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-human tetraxyacrylate, butyl δ-hydroxyacrylate, β-hydroxyethyl methacrylate, etc.

A vinyl ester of the formula CH2=CH"OC#tt (5) 1, where R11 is a hydrogen atom or an alkyl group having 4 or less carbon atoms, such as vinyl formate, vinyl acetate, vinyl propionate etc.

In the formula, R1 is a monovalent hydrocarbon group having up to 12 carbon atoms, vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether, etc.

Thermoformable nitrile resins that can be suitably used in the present invention include 50 to 90% by weight, particularly 60 to 80% by weight of acrylonitrile, and comonomers copolymerizable therewith, preferably conjugated diene hydrocarbons and ethylene non-hydrocarbons. It is obtained by polymerizing 10 to 50% by weight, especially 20 to 40% by weight of at least one comonomer selected from the group consisting of esters of saturated carboxylic acids, vinyl ethers and monovinyl aromatic hydrocarbons.

In addition to so-called random copolymers, the nitride-based thermoplastic resins may be in the form of graft polymers, such as polybutadiene, polyisoprene, butyl rubber, ethylene-propylene copolymers, ethylene-propylene-nonpolymer, etc. For backbone polymers such as conjugated diene copolymer, acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, acrylonitrile-styrene-butadiene copolymer,
an acrylonitrile monomer or a combination of the acrylonitrile monomer and other ethylenically unsaturated comonomers,
The content of acrylonitrile monomer in the final composition is 60
It can also be obtained by graft polymerization in such a manner that the amount is at least % by weight.

Furthermore, the nitrile thermoplastic resin used in the present invention may be in the form of a so-called polymer blend, such as acrylonitrile-butadiene copolymer (NBR) or acrylonitrile-butadiene-styrene copolymer CAB.
It may be a polymer blend in which acrylonitrile (S), etc. and an acrylonitrile-methyl methacrylate copolymer, etc. are blended in a quantitative ratio such that the final composition contains 60% by weight or more of acrylonitrile (IJ). Of course, in this case, when blending multiple types of polymers, there is no problem even if crosslinking or graft polymerization occurs between the multiple types of polymers by heat or the action of a radical initiator.

As polyesters, polyethylene terephthalate, copolyesters mainly composed of ethylene terephthalate units, and also containing a small amount of modifying ester units known per se are used for the purpose of the present invention. This polyester may also have a molecular weight of 8-enough to form a film. In connection with its use in the formation of multilayer tubes by coextrusion, this polyester has a higher molecular weight of 13
- Should have a quantity. That is, while the intrinsic viscosity [η] of polyester used in injection molding is 0.6 to 0.7, in the present invention it should have an intrinsic viscosity of 0.8 or more. Here, the intrinsic viscosity is a value defined by , and C is the concentration expressed in g/100m. If this limiting viscosity is smaller than the above value, uneven thickness will likely occur due to drawdown or the like during coextrusion.

Although not necessary, adhesives known per se can be used to enhance the adhesion between the polyester layer and the nitrile resin layer. As such an adhesive, a copolyester adhesive, a polyester 1-ether adhesive, an epoxy-modified thermoplastic resin, a maleic anhydride-modified polyolefin, an acrylic acid-modified polyolefin, etc. can be used.

Polyester base (PET), thermoformable nitrile resin (
TAN), the adhesive layer (AD) can be used in various layer configurations = 14-, for example with the outer layer on the left and the inner layer on the right: PET/TAN, TAN/PET PET/AD/TAN, TAN/AD /PET.

PET/TAN/PET, PET/AD/TANAD/
It can be used in a layered structure such as PET.

The thickness of the layer can vary, but generally PET:T
AN=2: 1 to 60:1, especially 4:1 to 15:
The thickness ratio is preferably in the range of 1, and when an adhesive layer is used, the thickness ratio is preferably in the range of PET:AD=5:1 to 100:1, particularly 10:1 to 50:1. .

Traditionally, stretch blow molding of plastics such as polyester involves injecting the plastic to form a bottomed parison (preform), then blow-stretching it while axially stretching it with a stretching rod, or shaping the plastic into a pipe shape. Various methods are known, such as extrusion, holding the material between a pair of clamps and stretching it in the axial direction, and then blow-stretching it by blowing fluid into it.

However, these methods, when applied to multilayer parinone of polyester and thermoformable nitrile resin,
It has been found that certain drawbacks arise in terms of stretchability and interlayer adhesion.

First, above a certain temperature, for example 140° C., polyester easily crystallizes, making it difficult to stretch, and tends to whiten and make the container itself opaque. In order to produce multilayer parinone by injection, it is necessary to injection mold the polyester and then injection mold the nitrile resin onto the polyester single mold, but the polyester single mold is heated at a temperature significantly lower than the above temperature. As a result, the degree of thermal adhesion between the two resins at the interface is incomplete, and delamination may occur during stretch blow molding or when sealing carbonated beverages in this multilayer bottle. Alternatively, the nitrile resin layer tends to break at this peeled portion.

2) IJ resin is a resin with a strong degree of hydrogen bonding, and this nitrile resin has a high acrylonitrile content, so nitrile resin has a melting point considerably higher than the crystallization temperature of polyester. It has a softening point, and therefore, during molding of the nitrile resin, the polyester whitens due to crystallization, resulting in the disadvantage that the polyester layer itself becomes opaque or its interlayer adhesion decreases.

In addition, in the latter method, there is a large difference between the melting point of the polyester or nitrile resin and the stretching temperature, so it is difficult to form the fused part at the bottom or the bottle opening by pinching off the mold. However, there is a problem in that this method can only be applied to polyolefins whose melting points and stretching temperatures are close to each other.

The first feature of the present invention is that polyester and thermoformable nitrile resin are first coextruded into a pipe or tube. That is, this coextrusion is carried out by combining the molten polyester and the molten nitrile resin in a die and extruding them through a ring-shaped orifice. The resins are well mixed at the interface between the two, and the thermal adhesion between the two is stronger than in the case of multilayer injection molding. This is exactly the same even when an adhesive resin is interposed between the polyester and the nitrile resin.

Next, the second feature is that this coextruded multilayer pipe or tube is cut to a certain length, and one end thereof is fused and closed to form a bottom part. That is, by using this bottomed preform, blow stretching can be performed simultaneously or almost simultaneously with axial stretching while pressing a stretching rod against the preheated preform, and in the case of sequential stretching. □ Fig. 1 shows a multilayer pipe particularly suitable for the purpose of the present invention, and this multilayer pipe 1 has a polyester inner layer 2. and an outer layer 6, thermoformable 2) an intermediate gas barrier layer 4 of IJ resin, and an adhesive layer 5α, 5 interposed between them;
It consists of b.

-18= It has already been pointed out that it is important to manufacture pipes and tubes by coextrusion, but in order to prevent polyester crystallization (whitening), extruded pipes should be immersed in water, etc. It is important to cool down quickly.

After cutting this pipe to a certain size, one end of the pipe is heated and melted, and then pressed with a male and female mold having a capity and a protrusion corresponding to an arbitrary bottom shape, such as a semi-circular shape, as shown in Fig. 2. A bottom portion 6 is formed as shown.

Next, the other end of this pipe 1 is also heated and subjected to pressing, stretching, blow molding, etc. in a desired mold, and as shown in FIG. A preform 10 having a fitting part, a screwing part, and a locking part with a lid such as a P neck ring (support ring) 9 is molded.

The order of forming these preforms does not matter, and they may be carried out in the above order or in the reverse order, or may be carried out simultaneously.

The method described above has the characteristic that no excess resin is generated when a preformed product is obtained from a multilayer pipe or tube.

Next, in the third step, the preform is preheated using hot air, an infrared heater, high frequency dielectric heating, etc. to a temperature appropriate for stretching the multilayer preform. In this case the temperature range is 85-12
The polyester resin is preheated to a stretching temperature of 0°C, preferably between 95°C and 110°C.

4 and 5 for explaining the stretch blow molding operation, a mandrel 11 is inserted into the mouth of a preform 10, and the mouth is inserted into a pair of split molds 12α, 12b.
Hold it between the two. A vertically movable stretching rod 13 is provided coaxially with the mandrel 11, and between this stretching rod 16 and the mandrel 11 there is an annular channel 14 for the injection of fluid.

In the present invention, the tip 15 of this stretching rod 16 is applied to the inside of the bottom part 6 of the preform 10, and this stretching rod 16
is moved downward to stretch it in the axial direction, and at the same time, fluid is blown into the preform 10 through the passage 14, and the fluid pressure causes the preform to expand and stretch in the circumferential direction.

According to the present invention, by performing axial stretching and circumferential stretching at the same time or almost simultaneously, even if the nitrile resin layer has a high content of nitrile units, it can be stretched at a relatively low temperature. This was discovered.

The reason for this is that co-stretching is performed with the nitrile resin layer placed on the polyester layer, and that delamination of both phase resin layers is suppressed during co-stretching, and that biaxial stretching is performed simultaneously and in a well-balanced manner. It is estimated that the

The thus obtained multilayer stretched polyester bottle 16 shown in FIG. 6 has not only excellent transparency but also extremely high gas barrier properties compared to a single polyester (stretched PET) bottle, which is superior to other plastic bottles. The gas barrier properties can be adjusted according to the needs, and the bottle is also pressure resistant, making it extremely easy to fill and store carbonated beverages, such as beer, cola, and cider.The container is hygienic, and is made of glass. Transparent 21 comparable to a bottle
- Provides an ideal container that is lightweight and wave resistant while having excellent gas barrier properties and pressure resistance.

Example 1 Diameter is 651! ll, effective length is 1 t 430 mm
An extruder for the inner and outer layers with a built-in full-flight screw of 50 mus in diameter and an extruder for the adhesive layer with a built-in full-flight screw with an effective length of 1.100 mm, 5-ring type Using a die, the inner and outer layers were polyethylene terephthalate with an intrinsic viscosity of 1.0, the middle layer was an acrylonitrile-styrene copolymer containing 70% by weight of acrylonitrile, and the adhesive layer was epoxidized octyl oleate io, oo.

A laminated pipe of 6 m and 5 layers made of maleic anhydride-grafted modified high-density polyethylene (grafting rate: 0.9% by weight) containing p-tone is extruded through a gouer into water and cooled. The outer diameter of this pipe is 30 mm, the inner diameter is 22 mm, and the thickness of each layer is 1.4 gm for the inner layer, 2.0 gm for the outer layer, 0.05 gm each for the adhesive layer, and 0.5 gm for the middle layer. It is a dragon, and this pipe is cut into a certain length (length 126, weight 56 g),
One end of the pipe 22- is heated to about 220°C to form a closed semi-spherical bottom, and the other end is heated to 150°C to promote neck crystallization to form a threaded part and neck ring to form a preliminary pipe with a total height of 145mm. Molding(
Preform) was obtained.

This preform was heated to 105°C, and a multilayer stretched bottle with an internal volume of 1500 cc was molded using a biaxial stretch blow molding method in which it was stretched in the vertical axis direction and blown in the horizontal axis direction in a blow mold. The oxygen permeability of this bottle is approximately 2.5
QC/m”・24H-atm (57℃),
There was no damage when it was dropped onto concrete from a height of 120α, and no peeling occurred between the layers. Further, more than 40% of the polyethylene terephthalate in the neck of this bottle was crystallized, and the neck did not deform even when filled with liquid at 96° C. and sealed.

Example 2゜Using the same equipment as Example 1, the inner and outer layers had an intrinsic viscosity of 0.9.
polyethylene terephthalate, the middle layer is 75% by weight acrylonitrile, the middle layer is acrylonitrile-butadiene-methyl acrylate copolymer, and the adhesive layer is maleic anhydride-grafted modified linear low-density polyethylene (graph il, 0% by weight) 6 A five-layer laminated pipe is extruded and cooled in water. This pipe has an inner diameter of 16 mm, a thickness of 61 mm, and has an inner layer: an adhesive layer: an intermediate layer:
Adhesive layer: outer layer ratio is 10:0.5:2:
It was 0.5:15. Cut this pipe into a certain size (length: 85 mm, weight: 20 g), and cut one end of the pipe into approximately 2.
The temperature was controlled to 30°C, the bottom of the semicircular sphere was closed and the other end was preheated to about 110°C to prevent neck crystallization, and a screw and neck ring were formed to obtain a preformed product.

This preformed product was heated to 100°C and subjected to almost simultaneous biaxial stretching blow molding in both the vertical and horizontal directions.
A multilayer stretched bottle was obtained.

The oxygen permeability of this bottle is 2.8cc-7m2・24H
- ATM (37°C), and no damage occurred when it was dropped onto concrete from a height of 120 cm.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a multilayer pipe used in the present invention, Figure 2 is a cross-sectional view of a multilayer pipe used in the present invention;
Figures 4 and 6 are cross-sectional views of the preform with the bottom and neck formed, and Figures 4 and 5 are cross-sectional views of the preform held in the blow mold before blow molding and after blow molding. A cross-sectional view of FIG. 6 shows a multilayer stretched bottle molded according to the present invention. 1... Pipe, 6... Bottom, 7... Open end, 1
0...Preformed product, 16...Multilayer stretched bottle. Patent applicant: Toyo Seikan Co., Ltd. 25- Figure 1

Claims (2)

[Claims] (1) A neck part with an opening at the upper end and a fitting part or threaded part on the outer periphery, a bottom part formed by fusion closure of the pipe or tube, and molecular orientation in biaxial directions by stretching and blowing the pipe or tube. The pipe or tube has an inner and/or outer surface base layer made of polyester mainly containing ethylene terephthalate units, an acrylonide IJ unit content of 50% by weight or more, and an oxygen permeable material. The coefficient is 2 x 1Q-”cc ・cR
/ate” saa・caHt (57℃, 0%RH)
A multilayer oriented polyester bottle characterized in that it consists of a coextrusion with a barrier layer of a thermoformable nitrile resin smaller than . (2) A method for manufacturing a multilayer stretched polyester bottle, comprising:
Acrylic nitrile unit content in gas barrier resin layer is 5
0% by weight or more and an oxygen permeability coefficient of 2 x 10-”c
c 6 crrL/cm" sec ・cmHy (3
7°C, 0% RH) 2) Use polyester resin mainly composed of ethylene terephthalate units for the inner layer and/or outer layer of the IJ resin to form the base, and if necessary, combine both resin layers. A pipe or tube is formed by coextrusion with an adhesive layer interposed between the two, the pipe or tube is cut to an appropriate length, one end of the pipe or tube is fused and closed, and the bottom is formed. At the same time, the other end is molded into a neck part having an opening at the upper end and a fitting part or a threaded part on the outer periphery, and the obtained preformed product is preheated to a suitable stretching temperature of 85 to 120°C, and then molded into a blow molded metal. 2 in the axial and circumferential directions within the mold.
A method for producing a multilayer stretched polyester bottle, which comprises axially stretched polyester bottle p-molding.