JPH0242350B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a laminated structure, and more particularly, to a laminated structure that is excellent in various properties such as processability, interlayer adhesion, and gas barrier properties. Conventional technology and technical issues to be solved Polyethylene terephthalate has excellent mechanical properties such as formability and creep resistance, and because it is capable of biaxial molecular orientation, it has excellent creep resistance and impact resistance. It has come to be widely adopted in the field of lightweight plastic containers, which have excellent properties such as toughness, rigidity, gas barrier properties, light weight, and transparency. However, the gas barrier properties of polyester containers are still not negligible compared to, for example, glass bottles, and the shelf life of small polyester bottles of 1 liter or less filled with carbonated drinks such as cola is only 2 months at most. It is said that the degree of On the other hand, olefin-vinyl alcohol copolymers such as saponified ethylene-vinyl acetate copolymers,
This material is well known as a thermoformable resin with excellent oxygen barrier properties, and it is already known that this resin can be combined with an olefin resin with excellent moisture resistance to make unstretched or stretched multilayer plastic containers. There is. It has already been proposed to use a laminated structure of polyester and olefin-vinyl alcohol copolymer as a container, and such a laminated structure has gas barrier properties, creep resistance, impact resistance, Although it is naturally expected that this type of laminated structure is excellent in combination with rigidity, the reason why such laminated structures have not yet been put into practical use for containers, especially biaxially stretched blow-molded containers, is that polyester and olefin
This seems to be because a strong interlayer bond cannot be obtained between the vinyl alcohol copolymer and the vinyl alcohol copolymer. The present inventors used a blend of a specific polyester and an ethylene-vinyl alcohol copolymer described below, and when laminating the blend with a polyester mainly composed of ethylene terephthalate units, blow molding, stretching, etc. Strong interlayer adhesion is obtained that does not disappear even under container forming conditions such as blow molding and drawing, and this laminated structure has various properties such as gas barrier properties, creep resistance, impact resistance, rigidity, and formability. We found that it has excellent characteristics. Purpose of the Invention The purpose of the present invention is to provide a laminated structure that has excellent gas barrier properties, creep resistance, impact resistance, rigidity, delamination properties, moldability, etc., and is useful as a sealed container such as a bottle or cup. It is in. Structure of the Invention According to the present invention, (A) a layer of polyester mainly composed of ethylene terephthalate units, (B) an acid component consisting of (i) terephthalic acid and/or isophthalic acid, and bis(2-hydroxyethoxy). A layer formed from a blend of (ii) an ethylene-vinyl alcohol copolymer and a polyester containing a diol component consisting of benzene or a combination of this and another diol in its main chain are provided in an adjacent positional relationship. A laminated structure is provided. That is, the present invention uses bis(2-
When laminating a layer formed from a blend of a polyester having (hydroxyethoxy)benzene in the main chain and an ethylene vinyl alcohol copolymer with a layer of polyethylene terephthalate, both can be bonded together without using a special adhesive. This is based on the new finding that a laminated structure with strong interlayer bonding and excellent gas barrier properties, creep resistance, and other properties can be obtained. Preferred Embodiment Blend Layer of the Invention The polyester used in the blend layer of the laminated structure of the present invention may contain terephthalic acid and isophthalic acid as acid components, each singly or in combination, but it is preferable that A copolyester having at least 5 mol % of isophthalic acid component in the main chain is used. That is, compared to polyesters derived from terephthalic acid, polyesters derived from isophthalic acid have improved compatibility with the olefin-vinyl alcohol copolymer. This is thought to be due to the fact that isophthalic acid ester units tend to have a bent structure in their polyester polymer side chains compared to p-oriented terephthalic acid units, which improves their compatibility with the olefin-vinyl alcohol copolymer. . As the diol component, bis(2-hydroxyethoxy)benzene is used alone or in combination with other diols. This bis(2-hydroxyethoxy)benzene is particularly suitable for 1,3
-bis(2-hydroxyethoxy)benzene is used, and this diol with aromatic groups is
At least 0.001 mol% based on the total amount of diol components
As mentioned above, it is necessary that 0.01 mol % or more of it be contained in the main chain of the polyester. By including this bis(2-hydroxyethoxy)benzene in the main chain of the polyester, gas barrier properties are dramatically increased, and antistatic properties are also improved, as is clear from the examples described below. It is possible to achieve this. As other diols that can be used in combination with bis(2-hydroxyethoxy)benzene, all diols having ester-forming ability can be used, such as ethylene glycol, propylene glycol, 1,4-butanediol, neopentyl, etc. Examples include glycol, cyclohexanediol, xylylene glycol, hexahydroxylylene glycol, and bis(4-β-hydroxyethoxyphenyl)sulfone. The polyester used in the blend layer in the present invention has ester repeating units derived from the dibasic acid and diol described above, i.e., the formula: In the formula, R ₁ is an aromatic group, and R ₂ is a group in which at least 0.001 mol% of all R ₂ groups is derived from bis(2-hydroxyethoxy)benzene, and is mainly formed from repeating units of However, there is no problem in containing a small amount of other ester repeating units as long as this essence is not impaired. This polyester generally has an intrinsic viscosity of 0.3 to 2.8 dl/g, particularly 0.4 to 1.8 dl/g [η ] It is preferable to have. Furthermore, from the standpoint of thermal bonding workability,
It is preferable to have a ring and ball softening point of 230°C or less, particularly from -30 to 200°C. In the present invention, the ethylene-vinyl alcohol copolymer used as the other component of the blend layer is composed of ethylene units and vinyl alcohol units obtained by saponifying vinyl ester units such as vinyl acetate, and is a gas barrier. From the viewpoint of properties and moisture resistance, the vinyl alcohol unit content should be 20 to 80 mol%, especially 40 to 80 mol%, and the content of residual vinyl ester units should be 4 mol% or less, especially 1 mol% or less. It should be. The molecular weight of this ethylene-vinyl alcohol copolymer is not particularly limited as long as it is within a molecular weight range that generally allows film formation. The viscosity of the ethylene-vinyl alcohol copolymer is generally determined by using a mixed solvent of 85% by weight of phenol and 15% by weight of water and measuring the intrinsic viscosity [η] at a temperature of 30°C from 0.07 to
17/g is preferred. [η]
If [η] is lower than 0.07/g, the mechanical strength when made into a molded product is unsatisfactory;
When it is higher than /g, the moldability of the resin laminate tends to decrease. The blend layer in the laminate structure of the present invention comprises the above-mentioned polyester (a) and ethylene-vinyl alcohol copolymer (b) in a ratio of a:b=1:99 to 99:1, particularly 5:95 to 90:10. It is suitable for obtaining a laminated structure having excellent gas barrier properties and delamination resistance. However, even when a blending ratio outside the above-mentioned preferred range is used, as will be described later, a layer containing polyester in an amount greater than the average value and an ethylene-vinyl alcohol copolymer content greater than the average value may be used. By forming a multilayer structure consisting of a layer containing a large amount of carbon dioxide, uniform and excellent gas barrier properties against all gases and excellent interlayer adhesion can be achieved. Polyester layer In the present invention, the polyester layer to be laminated with the blend layer is made of a film, sheet, etc., especially from the viewpoint of preventing deformation due to pressure when used as a container, and also has mechanical strength, water resistance, etc. From this point of view, polyethylene terephthalate (PET) is used, but it can also be used in blends with polybutylene terephthalate, polycarbonate, or other thermoplastic resins within a range that does not impair its properties. In addition, it is acceptable to include a small amount of comonomer in the main chain in order to improve various properties during thermoforming. For example, in order to improve drawdown properties during molding, a small amount of hexahydroxylylene glycol as a glycol component is acceptable. Modified PET containing PET etc. are used for the purpose of the present invention. The polyester should also generally have a molecular weight sufficient to form a film. In the present invention, a blend of a polyester having a specific diol component and an ethylene-vinyl alcohol copolymer as described above and a polyester made of polyethylene terephthalate can be molded as such by co-extrusion molding or the like, either as is or after blending with so-called compounding agents. It can be made into a laminated structure by known molding means. For example, for use as a food packaging material, it is preferable to directly apply the laminated molding operation without using so-called compounding agents, but if desired, compounding agents that are well known per se, such as ultraviolet absorbers, stabilizers, lubricants, etc. , antioxidants, pigments, dyes,
Antistatic agents and the like can be added according to known formulations. Furthermore, the laminated structure of the present invention has gas barrier properties,
Other polymers such as polyolefins, olefin copolymers, vinyl polymers, diolefin polymers, olefin-vinyl compound copolymers, etc. may be added to each layer within a range that does not substantially adversely affect properties such as impact resistance. It is possible to add amounts up to 10 parts by weight. Laminated Structure The laminated structure of the present invention includes a blend layer of polyester having a specific diol component and an ethylene-vinyl alcohol copolymer (hereinafter simply referred to as a blend layer), and a polyester layer made of polyethylene elephthalate (hereinafter simply referred to as a blend layer). It is possible to have various configurations within the range that satisfies the condition that the PET layers (referred to as PET layers) are provided in an adjacent positional relationship. For example, the laminated structure of the present invention can have the following cross-sectional arrangement. Two-layer structure (a) PET layer/blend layer Three-layer structure (a) PET layer/blend layer/PET layer (b) Blend layer/PET layer/berend layer Of course, there are more multilayer structures than the three-layer structure described above,
For example, five-layer structure (a) PET layer/blend layer/PET layer/blend layer/PET layer (b) blend layer/PET layer/blend layer//
It can also be used in a form such as a PET layer/blend layer, and it is possible to further improve gas barrier properties with such a multilayer structure, but in normal cases, the present invention uses a two or three layer structure. can fully achieve its objectives. The thickness of each layer constituting such a laminated structure varies depending on the use described below or the blending ratio of polyester and ethylene-vinyl alcohol copolymer in the blend layer, but generally it has gas barrier properties, impact resistance, and resistance. In order to obtain the optimum combination of interlayer peelability, etc., it is preferable that the thickness ratio of PET layer:blend layer is in the range of 500:1 to 1:5, particularly 100:1 to 1:3. The laminated structure of the present invention comprises a polyester having bis(2-hydroxyethoxy)benzene in the main chain as a diol component in the blend layer;
By laminating this blend layer with PET resin due to the inclusion of EVOH,
Significantly higher gas barrier properties can be obtained than when EVOH and PET are used alone. In addition, since the polyester contained in the blend layer contains many aromatic ester segments in its main chain, a special adhesive is used between it and the PET layer, which has similar aromatic ester segments. Significantly higher adhesive bonds are obtained without the need for Furthermore, as is clear from the examples described below, in the case of a layer structure in which the blend layer is used as the inner and outer layers, it has particularly excellent antistatic properties, and when used in applications such as containers, charged fine particles such as dust will not adhere to it. The remarkable effect of being difficult to do is achieved. Furthermore, since the laminated structure of the present invention itself has excellent adhesion with ethylene-vinyl alcohol copolymer, gas barrier properties can be improved by further laminating it with an ethylene-vinyl alcohol copolymer layer. Further improvements are possible. Forming method The formation of the laminate is preferably carried out by co-extrusion. According to this multilayer coextrusion, since both resins are well mixed at the adhesive interface between the resins, a laminated structure with particularly excellent adhesive strength can be obtained. For multilayer coextrusion, PET and the blend of polyester and EVOH described above are melt-kneaded in respective extruders, and then extruded through a multilayer die to form a film, sheet, or bolt having the layer structure described above, for example. It is molded into the shapes of pipes for use, preforms for bottles, etc. In the case of bottle preforms, the multi-layer co-extruded molten resin parison is pre-blow molded in a mold, or the multi-layer co-extruded pipe is cooled and cut to a certain size, and then the upper and lower ends of the pipe are cut into pieces. It is obtained by reheating the parts and molding the mouth thread part and the bottom part by means such as compression molding. In addition, when co-extruding, it is necessary to
Extruding the blend with EVOH under conditions where the difference between the average flow velocity of the polyester melt ( ₁ ) and the average flow velocity of the EVOH melt ( ₂ ) is 1 cm/sec or more and the blend flows in a laminar flow. Molding is preferred. Under such conditions,
In the blend layer, a layer in which polyester is preferentially distributed and a layer in which EVOH is preferentially distributed are formed, and therefore a layer in which polyester is preferentially distributed is formed.
Adhesive strength is further improved by positioning it so that it faces the PET layer. Furthermore, since polyester and EVOH, which themselves have gas barrier properties, are distributed in a layered manner in the blend layer, the gas barrier properties are further improved. Such a layered distribution structure was obtained by dividing the blend layer into three layers in the direction perpendicular to the thickness direction, that is, in the direction parallel to the surface direction, and measuring the infrared absorption spectrum of each divided layer ^. This can be confirmed by determining the concentration of ethylene-vinyl alcohol copolymer (EVOH) from the characteristic absorption of hydroxyl groups. Please refer to Japanese Patent Publication No. 43074/1984, etc., for details on the method of providing a multilayer structure in the blend layer. For example, the average flow rate () is expressed by the formula = (Q/3.6d)/S where Q is the discharge rate (Kg/hr) of the resin melt discharged from the die of the blend layer extruder under constant temperature and pressure. ), d is the melt density of the resin (g/cc), and S is the confluence point of each layer (inside the die)
is the cross-sectional area (cm ² ) of the passageway for the blend layer in . Defined by The melt density d of the resin can be determined by calculating the extrusion amount η (cc) at a constant temperature under a constant pressure (for example, 50 Kg/cm ² ) using a constant pressure extrusion viscometer, for example.
The following formula, η=HA−πr ² l In the formula, H is the plunger descent amount (cm),
A is the cross-sectional area of the barrel and r is the orifice radius (cm). and the weight W (g) of the extrudate η (cc)
By actually measuring , it can be determined using the following formula: d=W/η [g/cc]. In order to flow the blend in a laminar flow, a full-flight screw such as a metering screw or a nylon screw may be used as the screw for extruding the blend. By using such extrusion conditions, the multilayer distribution structure described above is formed in the blend layer of the laminated structure. In this case, the aforementioned | ₂ − ₁ |
= Δ value is 1 cm/sec or more, especially 1 to 10 cm/sec
In order to select the extrusion conditions such as Determine the dependence of the Δ
The temperature and pressure are determined so that Δ is 1 cm/sec or more, or Δ
The structure and various dimensions of the extruder may be changed or adjusted so that the value of is 1 cm/sec or more. The laminate can also be formed by a method called Sand-German lamination or extrusion coating. For example, a laminate can be produced by pressing a preformed polyethylene terephthalate film with a film of a blend of a predetermined polyester and an ethylene-vinyl alcohol copolymer under heat. Alternatively,
A laminated structure can be obtained by extruding the blend as an intermediate layer between two polyethylene terephthalate films, and pressing the extruded layer with the PET film in a sandwich-like shape. It is also possible to employ a method of hot pressing or hot rolling preformed various films in a predetermined stacking order. Of course, in addition to the method described above, it is also possible to use a molding machine having a plurality of cylinders and sequentially or co-inject predetermined resins to form the laminated structure of the present invention. Applications The laminated structure of the present invention is particularly useful as a stretch-blow-molded container or a sheet-molded container by stretching. For example, stretch blow molding is carried out by means known per se, except that the multilayer preform described above is used. First, the multilayer preform is preheated to a stretching temperature prior to stretch blowing. This stretching temperature is a temperature lower than the crystallization temperature of the polyester used and at which the multilayer preform can be stretched. used. Stretch blow molding of the preheated preform can be performed by means known per se, such as sequential stretch blow molding or simultaneous stretch blow molding. For example, in the former case, the preform is stretched axially under fluid injection at a relatively low pressure and then stretched by circumferential expansion of the container under fluid injection at a relatively high pressure. In the latter case, stretching in the circumferential direction and stretching in the axial direction are simultaneously performed by blowing fluid at high pressure from the beginning. The preform can be easily stretched in the axial direction by, for example, holding the neck of the preform between a mold and a mandrel, applying a stretching rod to the inner surface of the bottom of the preform, and stretching the stretching rod. The stretching ratios of the preform in the axial direction and the circumferential direction are 1.5 to 2.5 times (axial direction) and
It is desirable to set it to 1.7 to 4.0 times (circumferential direction). In the body of the container formed by stretch blow molding in this way, the polyethylene terephthalate layer is molecularly oriented so that its density is in the range of 1.350 to 1.402 g/cc, providing the desired impact resistance and rigidity for bottle-shaped containers. , transparency, etc., as well as excellent barrier properties against gases such as enzymes, nitrogen, carbon dioxide, and fragrance due to the presence of a blend layer containing an olefin-vinyl alcohol copolymer and a polyester having a specified diol component. is obtained, and excellent interlayer adhesion is maintained due to the presence of polyester in the blend layer described above. In addition, in the case of a sheet-formed container, the above-mentioned multilayer film or multilayer sheet is preheated to the above-mentioned stretching temperature, and this heated film etc. is formed into a cup shape by means such as vacuum forming, pressure forming, plug assist forming, or press forming. Form into. The invention is illustrated by the following example. Synthesis of polyester A specified acid component and diol component are charged into a glass reactor together with a small amount of a catalyst such as titanyl acetylacetonate, heated to 200℃ under a nitrogen gas atmosphere, and heated to about 100℃ while removing methanol generated.
The reaction was continued for a minute, and then the reaction temperature was raised to 250°C and maintained for about 1 hour, then the nitrogen gas supply was stopped and the temperature was raised to 275°C for about 3 minutes under reduced pressure of 0.4 mmHg or less.
Time polymerization was carried out. Table 1 shows the compositions of the acid component and diol component for each of the polyester samples obtained. The final composition of the sample was confirmed by proton NMR and gas chromatography.

[Table] is shown below.
Example 1 Using each polyester in Table 1, this polyester and an ethylene-vinyl alcohol copolymer (softening temperature 182°C) having a vinyl alcohol content of 69 mol% and an ethyl acetate residue of 0.4 mol%, The mixture was mixed at room temperature for 10 minutes using a Henschel type dry blender with various mixing ratios. Each of these mixtures has a diameter of 50 mm and an effective length of 1100 mm.
Using a mm extruder, the width is 150 mm with a T-die.
A sheet with a wall thickness of 0.5 mm was formed using the following methods. Further, polyethylene terephthalate resin (PET) having an intrinsic viscosity of 0.91 dl/g at 30°C was molded into a 1.5 mm thick sheet by extrusion in a mixed solvent of phenol/tetrachloroethane in a weight ratio of 50/50. These two sheets were overlapped and held in a hot press maintained at approximately 260°C for 120 seconds without pressure, then pressurized to 5 kg/cm ² and held for 60 seconds to obtain a two-layered laminate. Ta. Furthermore, a part of this laminate was stretched twice in the uniaxial direction at a stretching temperature of 120° C. using a research biaxial stretching device BISTRON BT-1 manufactured by Iwamoto Seisakusho to create a stretched sheet. A test piece of 100 mm in length and 10 mm in width was cut out from the unstretched sheet and stretched sheet immediately after adhesion (for the latter, the stretching axis was aligned with the longitudinal direction), and tested using a tensile tester at room temperature. , tensile speed
A T-peel test was conducted at 100 mm/min. Measurements were performed five times under each condition, and the arithmetic mean value was taken as the peel strength. The results obtained are shown in Table 2. In addition, for stretched sheets, the ones immediately after stretching were tested at 27℃ and 60%RH using a gas permeation tester.
The oxygen gas permeability coefficient was determined in the atmosphere of The results are also shown in Table 2.

【table】

[Table] Example 2 Each blend of polyester and EVOH used in Example 1 was used as an intermediate layer resin, and Example 1
An extruder for the inner and outer layers with a built-in full-flight screw with a diameter of 65 mm and an effective length of 1430 mm was used, using the PET resin used in the above as the resin for the inner and outer layers.
PET/blend/PET three-layer pipe is made using an extrusion molding device that combines a middle layer extruder with a built-in full-flight screw with an effective length of 950 mm, a feed pipe, and a three-layer triple die. Melt extrusion, pre-blow molding in a split mold, inner diameter 27.7mm, length 138mm, average wall thickness 3.5mm
A preform with a bottom of mm was molded. The thickness ratio of the outer layer: middle layer: inner layer of this preform is 10:
Extrusion conditions were set so that the ratio was 1:10. Each of these bottomed preforms was heated with an infrared heater and then stretch-blow-molded using a sequential biaxial stretch blow-molding method so that the axial stretch ratio was 2.0 times and the circumferential stretch ratio was 3.0 times. is about 0.40mm,
A total of nine types of three-layer bottles with an internal volume of approximately 1 were manufactured. For comparison, a bottomed preform with the same dimensions as above was molded using only polyethylene terephthalate (PET), and then a biaxially stretched blow bottle with the same dimensions was manufactured in the same manner as above. The enzyme gas permeability (Qo ₂ ) and drop strength (f ₁₀ ) of these sample bottles were measured, and the results are shown in Table 3. The above test was conducted according to the following measurement method. (i) Oxygen gas permeability, Qo ₂ ; The inside of the bottle to be measured is replaced with nitrogen gas in a vacuum, the mouth of the bottle is sealed with a rubber stopper, and the contact surface between the mouth and the rubber stopper is sealed with epoxy. After covering with adhesive, the bottle was placed at a temperature of 37℃ and humidity.
After being stored in a constant temperature and humidity chamber at 15% RH for a certain period of time, the concentration of the enzyme 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 [cc/m ²・day・atm] where m: Amount of nitrogen gas filled into the bottle [ml], t: Storage period in the hot tank [day], Ct: Enzyme concentration in the bottle after t days [Vol%], A: Effective surface area of the bottle [m ² ], Op: Oxygen gas partial pressure (=0.209) [atm], (ii) Drop strength, f ₁₀ ; After filling 10 bottles of each type with a certain weight of saline solution and sealing the mouth with a cap,
It was left standing in an atmosphere at 2°C for two days and nights. The bottle was then dropped from a height of 120 cm at a temperature of 20°C so that the bottom of the bottle hit the concrete surface. The number of falls was repeated up to 10 times. The drop strength, _f10 , was calculated from the number of bottles that remained undamaged after being dropped 10 times according to the following formula. f ₁₀ = 100×N−n ₁₀ /N [%] Where, N: Number of bottles tested (= 10) [bottles] n ₁₀ : Number of bottles that were not damaged after being dropped up to 10 times [bottles].

【table】

【table】

Claims (1)

[Scope of Claims] 1 (A) a layer of polyester mainly composed of ethylene terephthalate units, (B) (i) an acid component consisting of terephthalic acid and/or isophthalic acid, and bis(2-hydroxyethoxy)benzene or A layer formed from a blend of (ii) an ethylene-vinyl alcohol copolymer and a polyester containing in its main chain a diol component consisting of a combination of this and another diol are provided in an adjacent positional relationship. A laminated structure characterized by: