JPS6239088B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a multilayer container with excellent gas permeation resistance and high transparency, and a method for producing the same. The present invention relates to a multilayer container whose outer layer is made of a plastic polyester resin and a metaxylylene group-containing polyamide resin, and whose thin wall portion is oriented in at least one direction, and a method for manufacturing the same. Traditionally, thermoplastic polyester resins, mainly composed of polyethylene phthalate, have been used in various containers, films, and sheets due to their excellent mechanical properties, gas permeability resistance, chemical resistance, fragrance retention, and hygienic properties. It is widely used as packaging material. Especially in recent years, blow molding technology
Thanks to advances in axial stretch blow molding technology, there have been remarkable developments in the use of hollow containers such as bottles and cans. However, biaxially oriented containers made of thermoplastic polyester resin mainly composed of polyethylene terephthalate do not have all the necessary features, especially for food containers whose contents require gas barrier properties. It was unsuitable due to the lack of gas barrier performance against oxygen. So far, saponified ethylene-vinyl acetate copolymer and styrene-acrylonitrile copolymer have been known as thermoplastic resins with high gas barrier properties, but containers made of each single substance lack impact resistance. However, it was difficult to put it into practical use due to the nature and hygiene of children. The present inventors have conducted extensive research in order to provide a container that has oxygen gas barrier properties without impairing the excellent mechanical properties, transparency, chemical resistance, sanitary properties, etc. of thermoplastic polyester resin. As a result, a container precursor molded body (hereinafter referred to as multilayer parison) having a multilayer structure obtained by compounding with metaxylylene group-containing polyamide resin (hereinafter referred to as SM resin) is heated at a specific temperature and in a specific proportion. It was discovered that a container having excellent gas barrier properties and high transparency can be obtained by stretching, and the present invention was achieved based on this finding. That is, the present invention provides a container having a multilayer structure made of two or more types of thermoplastic resins, the innermost layer being a thermoplastic polyester resin containing ethylene terephthalate as a main repeating unit and having an intrinsic viscosity of 0.55 or more, and the outer layer being made of an SM resin. A multilayer container with excellent gas permeability and high transparency, characterized in that the inner thin part of the container is oriented in at least one direction, and the innermost layer has ethylene terephthalate as a main repeating unit. A multilayer parison is formed with polyester resin and the outer layer is SM resin, and then the container precursor molded body is heated until the temperature reaches Tg+ of the polyester resin constituting the innermost layer.
From 15℃ (Tg; glass transition temperature) to 2 (Tg) + 15
Excellent gas permeability and high transparency, characterized by stretching 1 to 4 times in the vertical direction and 2 to 7 times in the horizontal direction (peripheral length magnification in the horizontal direction of the container) in the temperature range up to ℃. The present invention relates to a method for manufacturing a multilayer container. The thermoplastic polyester resin containing ethylene terephthalate as a main repeating unit as used in the present invention usually has 80 mol% or more of the acid component, preferably 90 mol% or more of terephthalic acid, and 80 mol% or more of the glycol component, preferably 90 mol% or more of the acid component. It means a polyester in which 90 mol% or more is ethylene glycol, and the remaining acid components include isophthalic acid, diphenyl ether 4,4'-dicarboxylic acid, naphthalene 1,
4- or 2,6-dicarboxylic acid, adipic acid,
Sebacic acid, decane 1,10-dicarboxylic acid, hexahydroterephthalic acid, and other glycol components such as propylene glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, 2,2
-bis(4-hydroxyphenyl)propane,
It means a polyester resin containing 2,2-bis(4-hydroxyethoxyphenyl)propane, or p-oxybenzoic acid, p-oxyethoxybenzoic acid, etc. as an oxyacid. Alternatively, a blend of two or more types of polyester may be used so that ethylene terephthalate falls within the above range. The polyester resin of the present invention may contain additives such as colorants, ultraviolet absorbers, antistatic agents, thermal oxidative deterioration inhibitors, antibacterial agents, and lubricants in appropriate proportions, if necessary. The thermoplastic polyester resin of the present invention needs to have an intrinsic viscosity of 0.55 or more, more preferably 0.65 to 1.4. If the intrinsic viscosity is less than 0.55, it will be difficult to obtain a parison, which is a precursor molded body of a container, in a transparent amorphous state, and the resulting container will also have insufficient mechanical strength. Furthermore, the SM resin used in the present invention is metaxylylene diamine or a mixed xylylene diamine containing metaxylylene diamine and para-xylylene diamine in an amount of 30% or less of the total amount, and a carbon number of 6 to 6.
It is a polymer containing at least 70 mol% of structural units formed from 10 α, ω-aliphatic dicarboxylic acids in its molecular chain. Examples of these polymers include polymethaxylylene adipamide, polymethaxylylene sebacamide,
Homopolymers such as polymethaxylylenesperamide, and metaxylylene/paraxylylene adipamide copolymers, metaxylylene/paraxylylene pimeramide copolymers, metaxylylene/paraxylylene azeramide copolymers, etc. copolymers such as, as well as components of these homopolymers or copolymers with aliphatic diamines such as hexamethylene diamine, cycloaliphatic diamines such as piperazine,
Aromatic diamines such as para-bis-(2-aminoethyl)benzene, aromatic dicarboxylic acids such as terephthalic acid, lactams such as ε-caprolactam, ω-aminocarboxylic acids such as γ-aminoheptanoic acid, Examples include copolymers copolymerized with aromatic aminocarboxylic acids such as para-aminomethylbenzoic acid. In the above copolymer, para-xylylene diamine accounts for 80% or less of the total xylylene diamine, and the constituent units formed from xylylene diamine and aliphatic dicarboxylic acid account for at least 70 mol% in the molecular complex. That's all. These polymers include nylon 6, nylon 6-6, nylon 6-10, nylon
11, polymers such as nylon 12, antistatic agents, lubricants,
It may also contain anti-blocking agents, stabilizers, dyes, pigments and the like. Since the SM resin itself is inherently brittle in an amorphous state, it is necessary to have a relative viscosity of 1.5 or more, more preferably 2.0 or more. In the present invention, in order to obtain a container with excellent gas barrier properties and high transparency, it is necessary to maintain considerable transparency in the multilayer parison, which is a container precursor molded product, and in addition, it is necessary to maintain considerable transparency in the thin wall portions that constitute such a container. It is necessary that all of the resin components (mainly the body part) are oriented in at least one axis, and to obtain such a container, it is necessary to stretch the parison in at least one axis. Conventionally, when a saponified ethylene-vinyl acetate copolymer known as a high gas barrier resin is used, since the resin itself is a crystalline resin, devitrification occurs during parison molding, resulting in a significant decrease in transparency. Of course, transparency can be improved by thinning the layer by stretching, but the parts that are not stretched, such as the bottom of the bottle,
Since it remains in a devitrified state, it is unfavorable in terms of appearance. Furthermore, when using a styrene-acrylonitrile copolymer, since it is an amorphous resin itself, it will not devitrify during molding, but its glass transition temperature is high, so it cannot be used under the stretching temperature suitable for polyester resin. It has the disadvantage that it cannot be extended sufficiently. Furthermore, since it is an amorphous resin, it does not induce oriented crystallization even if it is stretched, so it also has the disadvantage that the container deforms due to residual stretching stress. In contrast to these resins, SM resin itself is originally a crystalline resin, but because it has a relatively high Tg, it is easily amorphized by rapid cooling from the molten state, and a parison with good transparency can be obtained. Since Tg is almost equal to the Tg of polyester resin, oriented crystallization is sufficiently induced by stretching under the stretching conditions of polyester resin, and unlike the above-mentioned high gas barrier resins, it has excellent transparency, gas barrier properties, thermal stability, etc. A container with high commercial value can be obtained. The degree of orientation is detected by measuring the difference in refractive index between the thickness direction and the plane direction in the thin wall portion of the container. It is preferably 0.05 or more, and more preferably 0.05 or more. If the difference in refractive index is less than 0.02, sufficient improvement in mechanical properties and gas barrier properties cannot be expected, and the adhesion between the layers also decreases. If it is difficult to measure the degree of orientation based on the refractive index, it can also be detected based on the anisotropy of mechanical properties. Although the container of the present invention can be manufactured according to conventional container manufacturing methods, it is particularly efficiently obtained by biaxial stretch blow molding at a specific temperature. When carrying out the present invention using a biaxial stretch blow molding method, a multilayer parison is heated to a stretching temperature and expanded and stretched by a rod moving in the axial direction within a blow mold and compressed gas blowing to form a container. A multilayer parison is obtained by step-by-step molding starting from the inner layer using a conventional injection molding machine or a molding machine with multiple melt injection devices, or has one end of a pipe with a multilayer structure formed by a multilayer extrusion molding machine. Obtained by bottoming out, etc. The shape of the multilayer parison may be any arbitrary shape as long as it is expandable and rigid. The thickness ratio of the SM resin layer constituting the outer layer to the thickness of the polyester resin layer constituting the innermost layer may be 1 or less. Even if this ratio is made larger than this, it is not possible to expect much improvement in gas permeability resistance, and on the contrary, the adhesive force between both resin layers may decrease, and the stretching stress during blow molding may increase. resulting in disadvantages. When this multilayer parison is obtained by injection molding, the thickness of each resin layer constituting the multilayer parison is usually 0.1 to 5 mm, and the total thickness of the inner layer and outer layer is 1 to 8 mm, preferably 2 to 6 mm. If the wall thickness of each layer is thinner than 0.1 mm, it will be difficult for the resin to flow inside the mold, and the total wall thickness will be 8 mm.
If it exceeds mm, it is not preferable because devitrification occurs when molding a multilayer parison or the pressure required for blowing becomes extremely high. When manufacturing a multilayer parison using a multilayer extrusion molding machine, the thickness of each resin layer can be made thinner than when manufacturing using an injection molding method, but in order to maintain the shape of the container after biaxial stretch blow molding, The thickness of each resin layer is usually 0.1~
4mm is required. The thus obtained multilayer parison is heated to a temperature range that allows stretching, and expanded and stretched in a blow mold to produce a container with two-stretch orientation. The temperature is preferably at least (Tg + 15) °C and at most (2Tg + 15) °C of the constituting polyester resin, particularly preferably from 90 to 150 °C. This indicates that the SM resin used in the present invention
This is because the Tg is close to that of the polyester resin, and by heating the parison to the above temperature range, it can be effectively stretched and oriented. At a normal heating rate, stretching is possible if the surface temperature of the parison is within the above temperature range. If the preheating temperature is less than (Tg+15)°C, it is not preferable because micropoid formation due to cold stretching occurs in the container, resulting in a burr-like appearance and devitrification.
Also, if the temperature exceeds (2Tg + 15)℃, the outer layer
This is not preferable because the SM resin causes devitrification due to crystallization, which makes stretching difficult, and also causes poor adhesion between resin layers. When expanding and stretching the multilayer parison, the stretching ratio is 1 to 4 times in the vertical direction and 2 to 7 times in the horizontal direction, especially the area stretching ratio (stretching ratio in the vertical direction x stretching ratio in the horizontal direction). ) is particularly preferably 5 to 18 times from the viewpoint of pressure adhesion between resin layers and transparency. The above is a method for manufacturing a multilayer container with polyester resin as the inner layer and SM resin as the outer layer. In order to further improve the delamination resistance of both layers, modified polyolefin resin containing a carbonyl group (for example, manufactured by Dupont Co., Ltd.) is used. , Surlyn A), etc. can also be formed as an adhesive layer. In addition, the container of the present invention can be further improved in various properties, such as water repellency, oil repellency, abrasion resistance, scratch resistance, antistatic property, and weather resistance. surface coating treatment,
It is also possible to perform spraying treatment or the like to further improve performance. It goes without saying that the surface treatment of the container may be carried out at the parison stage, or may be carried out on the finished container after blow molding. The present invention will be explained below with reference to Examples. Also,
The methods for measuring the main characteristics measured in the present invention are shown below. (1) Intrinsic viscosity of polyester resin [η]; Phenol/tetrachloroethane = 6/4 (weight ratio)
Measurement was performed at 30°C using a mixed solvent. (2) Relative viscosity ηrel of SM resin; 1g of resin is 96% sulfuric acid
It was dissolved in 100 ml and measured at 25°C. (3) Glass transition temperature (Tg): Measured using PerkinElmer's DSC-IB at a heating rate of 20°C/min. (4) Melting point (Tm); same as above (5) Refractive index; attach a polarizing plate to the Atsube refractometer,
Measurements were made using the sodium D line at 25°C. shaft,
The degree of orientation was detected by calculating nx+ny/2−nz=Δn (birefringence), where the refractive index in the circumferential direction (both plane directions) is nx and ny, and the refractive index in the thickness direction is nz. (6) Transparency and haze: Calculated using Hazemeter S manufactured by Toyo Seiki Co., Ltd. according to the following formula according to JIS-K6714. Transparency = (T ₂ / T ₁ ) × 100 (%) Haze = T ₄ - _{T 3}・(T ₂ / T ₁ ) / T ₂ × 100 (
%) T ₁ ; Incident light amount T ₂ ; Total light transmission amount T ₃ ; Scattered light amount by the device T ₄ ; Scattered light amount by the device and sample (7) Oxygen permeation amount; Rika Seiki Kogyo dual-unit gas permeability meter It was measured by pressure change at 30°C using a method according to ASTM-D-1434-58.
(cc/m ²・24hr・atm) (8) Water vapor permeation rate; 40℃ according to JIS-Z-0208,
It was measured from the weight increase by the Cupp method at 90% RH. (g/m ²・24hr) (9) Tensile properties: Using a strip-shaped specimen with a width of 10 mm, the yield strength and rupture were measured using a Toyo Baldwin Tensilon with a chuck distance of 50 mm and a tensile speed of 50 mm/min. Strength and elongation were measured (23°C). Examples 1 to 4 and Comparative Examples 1 to 3 As polyester resin constituting the inner layer [η]
Polyethylene terephthalate with = 0.72, Tm = 257°C, Tg = 70°C is used, and polymethaxylylene adipamide (metaxylylene/
Using paraxylylene (99/1 weight ratio) (referred to as SM-1), multilayer parisons having various dimensions were molded. In either case, the thickness of each resin layer is inner layer: outer layer = 3.5 mm: 1.5 mm. The parison was formed using an N-95 injection molding machine manufactured by Memoto Steel Works, and the biaxial stretch blow molding was performed using a molding machine prototyped at the Toyobo Co., Ltd. Research Institute. The shapes of the obtained hollow containers were all beer bottle-shaped in Examples 1 to 4, and Comparative Examples 1 to 2 had a total length of 265 mm, a body outer diameter of 80 mm, and an internal volume of 1000 ml; The total length is 200mm, body outer diameter
It is an 80mm container with an internal volume of 700ml. The forming conditions for each example are shown in Table 1, and the performance of the resulting containers is shown in Table 2.

【table】

[Table] As is clear from the table, Example 1 according to the present invention
All of the containers obtained in Examples 1 to 4 had high transparency, excellent gas permeability, and mechanical properties. On the other hand, in Comparative Example 1, where the stretching temperature is too low, the stress required for stretching is extremely large, and the parison may break during the stretching blowing process, or the bolt may not be shaped as per the pattern, or even if it is shaped, the appearance of the bolt may be poor. However, it exhibited a remarkable pearlescent appearance and could not be put to practical use. In addition, in Comparative Example 2, in which the stretching temperature was too high, the surface layer of the parison devitrified due to crystallization during the heating process of the parison, and furthermore, a sufficient orientation effect could not be obtained, resulting in insufficient physical properties such as drop impact strength. It had drawbacks. Furthermore, Comparative Example 3, in which the areal stretching ratio was 5 times or less, had the disadvantage that the pressure bonding force of each resin layer was insufficient and delamination occurred due to drop impact. When the stretching ratio is small like this, polyester resin
By providing an adhesive layer between the SM resin layer and the SM resin layer, the problem of delamination can be solved. In this case, improvement in mechanical properties can also be expected due to improvement in pressure bonding properties. Examples 5 to 8 and Comparative Examples 4 to 6 As the SM resin constituting the outer layer, ηrel=2.35, Tm=235°C, obtained by copolymerizing 2.5% by weight of polyethylene glycol with a molecular weight of 4000 to the SM-1 composition.
Polymethaxylylene adipamide (SM
Hollow containers were obtained in the same manner as in Examples 1 to 4 and Comparative Examples 1 to 3, except that the sample (referred to as -2) was used. In addition,
The molding conditions performed in Examples 5 to 8 and Comparative Examples 4 to 6 were those of Examples 1 to 4 and Comparative Examples 1 to 3, respectively.
It corresponds to , and is as shown in Table 1. Table 3 shows the performance of the obtained container.

【table】

[Table] Examples 5 to 8 and Comparative Examples 4 to 6 gave substantially the same results as the corresponding Examples 1 to 4 and Comparative Examples 1 to 3, respectively. That is, in Examples 5 to 8, containers with high transparency, excellent gas barrier properties, and mechanical properties were obtained, but in Comparative Examples 4 to 6, containers with commercial value that met the objectives of the present invention were not found. I couldn't get it. An unsaturated monomer mainly composed of an unsaturated silane compound can be coated on the surface of the obtained container and cured, a polymer composed of an unsaturated monomer mainly composed of an unsaturated silane can be coated, or an epoxy silane can be applied. Water resistance and scratch resistance can be improved by applying compounds such as alkoxysilane compounds, organic titanium compounds, silicone resins, and fluororesins.

Claims (1)

[Scope of Claims] 1. A container having a multilayer structure made of two or more types of thermoplastic resin, wherein the innermost layer has ethylene terephthalate as a main repeating unit and has an intrinsic viscosity of 0.55.
A multilayer container with excellent gas permeability resistance, characterized in that the outer layer is composed of the above thermoplastic polyester resin and a metaxylylene group-containing polyamide resin, and the thin wall portion of the container is oriented in at least one direction. 2. Form a container precursor molded body having a multilayer structure in which the innermost layer is a polyester resin containing ethylene terephthalate as a main repeating unit and the outer layer is a metaxylylene group-containing polyamide resin. In the temperature range from Tg + 15℃ (Tg: glass transition temperature) of the polyester resin constituting the inner layer to 2 (Tg) + 15℃, it is 1 to 4 times the vertical direction and 2 to 7 times the horizontal direction (the A method for producing a multilayer container with excellent gas permeation resistance, which is characterized by stretching (perimeter magnification). 3. The manufacturing method according to claim 2, wherein the stretching is carried out by biaxial stretching blow molding. 4. The manufacturing method according to claim 2 or 3, wherein the container precursor molded body is stretched at an area magnification (stretching ratio in the vertical direction x stretching ratio in the horizontal direction) of 5 times or more.