JPH021670B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF THE INVENTION The present invention relates to a resin laminate container, and more particularly to a resin laminate container that is excellent in various properties such as appearance workability, interlayer adhesion, and gas barrier properties. Prior Art and Technical Issues to be Solved Ethylene 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, ethylene-vinyl alcohol copolymer is known as a thermoformable resin with excellent oxygen barrier properties, and it has been proposed to make a container in the form of a laminated structure of polyester and this ethylene-vinyl alcohol copolymer. has already been proposed, and it is naturally expected that such a laminated structure will have an excellent combination of gas barrier properties, creep resistance, impact resistance, rigidity, etc. However, it has not yet been put to practical use in containers, especially biaxially stretched blow-molded containers. The reason for this seems to be that a strong interlayer bond cannot be obtained between the polyester and the ethylene-vinyl alcohol copolymer. OBJECT OF THE INVENTION An object of the present invention is to provide a container made of a resin laminate structure of copolyester resin and ethylene terephthalate that has excellent gas barrier properties. Another object of the present invention is to have a strong interlayer bond between a layer made of polyethylene terephthalate and a gas barrier layer, and to improve mechanical properties such as moldability, impact resistance, and creep resistance, as well as gas barrier properties. The objective is to provide a resin laminated container with excellent combinations of Structure of the Invention According to the present invention, (A) polyester containing ethylene terephthalate units as a main component is contained as the inner and outer layers, (B) an acid component consisting of terephthalic acid, isophthalic acid, or a combination thereof, and 5% per total diol component.
A copolyester containing in the main chain a diol component consisting of a combination of bis(2-hydroxyethoxy)benzene in an amount of 70 mol% to 70 mol% and other diols mainly consisting of ethylene glycol as an intermediate layer; There is provided a resin laminated container characterized in that the resin laminated container is comprised of laminated plates provided in an adjacent positional relationship. Function The present invention includes a copolyester layer having bis(2-hydroxyethoxy)nenzene as a diol component in its main chain as an intermediate layer, and a layer made of polyethylene terephthalate is laminated in an adjacent positional relationship. , a strong interlayer bond is formed between the layers without the use of special adhesives, and it also improves processability, appearance of the molded container, mechanical properties such as impact resistance, creep resistance, etc., and gas barrier properties. An excellent laminated structure can be obtained by combining the
This is based on the knowledge that various advantages can be obtained by molding containers from this laminated structure. 5 to 5 per total diol component as diol component
The copolyester containing 70 mol% of bis(2-hydroxyethoxy)benzene has excellent gas barrier properties (oxygen gas permeability) as shown in the example below, and also has excellent adhesion to polyethylene terephthalate (PET). It is also excellent. However, like other copolymers, this copolyester also has problems such as lack of rigidity and being easily scratched, surface staining, and poor heat resistance. In the present invention, this copolyester is sandwiched between inner and outer layers of polyethylene terephthalate, which has excellent rigidity, transparency, and impact resistance.
These problems can be solved by creating a structure in which the copolyester is protected. Preferred Embodiment of the Invention Resin Component In the container formed from the resin laminated structure of the present invention, as the copolyester to be laminated to the layer consisting of polyethylene terephthalate, terephthalic acid and isophthalic acid are used as acid components alone or in combination, Further, as a diol component, bis(2-hydroxyethoxy)benzene is used alone or in combination with other diols. As this bis(2-hydroxyethoxy)benzene, 1,3-bis(2-hydroxyethoxy)benzene is particularly used, and this diol having an aromatic group is
It is necessary that the main chain of the polyester contains from 70 mol% to 70 mol%, preferably from 7 to 65 mol%. By including this bis(2-hydroxyethoxy)benzene in the main chain of the polyester, gas barrier properties are dramatically increased, as is clear from the examples described later, and the aromatic group is also present in the main chain. Since the proportion occupied by segments increases, it is thought that a strong interlayer bond is formed between polyethylene terephthalate and polyethylene terephthalate having similar aromatic groups without using a special adhesive. As other diols that can be used in combination with bis(2-hydroxyethoxy)benzene, all diols capable of forming a sugar ester can be used, such as ethylene glycol, propylene glycol, 1,4-butanediol, and neopentyl. glycol, cyclohexanediol,
Examples include xylylene glycol, hexahydroxylylene glycol, and bis(4-β-hydroxyethoxyphenyl) sulfone. This copolyester used in the present invention is
Ester repeating units derived from the aforementioned dibasic acids and diols, i.e., the formula: In the formula, R ₁ is an aromatic group, and R ₂ is mainly formed from repeating units of 5 to 70 mol% of the total R ₂ groups are derived from bis(2-hydroxyethoxy)benzene. 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. If it is lower than 0.3dl/g, the mechanical strength of the molded product will be unsatisfactory;
When it is higher than 2.8 dl/g, the moldability of the laminate tends to decrease. Furthermore, from the viewpoint 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 addition, the molecular weight should generally be within a molecular weight range that provides film-forming ability. In the present invention, polyethylene terephthalate (hereinafter sometimes simply referred to as PET) is used for films, sheets, etc., especially when used as containers, from the viewpoint of preventing deformation due to pressure, etc., and from the viewpoint of mechanical strength and water resistance. ) is laminated on the polyester, but it can also be blended with polybutylene terephthalate, polycarbonate, or other thermoplastic resins as long as the excellent moldability and other properties of polyethylene terephthalate are not impaired. 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, the polyester and polyethylene terephthalate containing the above-mentioned specific diol component in the main chain are formed into a laminate structure by a well-known molding method such as coextrusion molding, either as is or after blending with so-called compounding agents. can do.
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, etc. can be blended according to known formulations. Laminated Structure The laminated structure of the present invention contains a copolyester layer containing a specific diol component in its main chain (hereinafter simply referred to as polyester) as an intermediate layer, and inner and outer layers made of polyethylene terephthalate (hereinafter simply referred to as PET layer). It is possible to have various configurations within the range that satisfies the condition that the two (referred to as "the two") are provided in an adjacent positional relationship. For example, the laminated structure of the present invention can have the following cross-sectional arrangement. Three-layer structure PET layer/polyester layer/PET layer Polyester layer/PET layer/polyester layer Five-layer structure PET layer/polyester layer/PET layer/polyester layer/PET layer. Furthermore, a polyester layer is provided, and between these,
Although it is possible to further improve the gas barrier properties by using a multilayer structure such as a seven-layer structure in which PET layers are provided on the inner and outer layers, the objective of the present invention is usually achieved with a three- to five-layer structure. can be fully achieved. Although the thickness of each layer constituting such a laminated structure can be changed arbitrarily depending on the use described below, in order to obtain the optimal combination of gas barrier properties, delamination resistance, impact resistance, etc., the PET layer :Polyester layer=100:1 to 1:2 It is particularly preferable to set the thickness ratio in the range of 50:1 to 1:1. In the polyester layer of the laminated structure of the present invention,
Since polyester containing bis(2-hydroxyethoxy)benzene in the main chain is used as the diol component, this polyester layer should be used as an intermediate layer and laminated so that the polyethylene terephthalate layer and the polyethylene terephthalate layer are adjacent to each other. This makes it possible to obtain significantly higher gas barrier properties than when polyethylene terephthalate is used alone.However, since this polyester contains many aromatic ester segments in its main chain, similar It is possible to maintain a significantly high adhesive bond between polyethylene terephthalate with aromatic ester segments without the use of special adhesives, and excellent moldability,
Mechanical properties such as appearance and impact resistance strength will be developed. Forming method The laminate is preferably formed by multilayer coextrusion. 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, after melt-kneading PET and the aforementioned polyester in their respective extruders,
It is extruded through a multi-layer, high-volume die so as to have the above-mentioned layer structure, and is formed into a film, sheet, bottle pipe, bottle preform, etc. In the case of bottle preforms, the multi-layer co-extruded molten resin parison is professionally 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 preforms. It is obtained by reheating the parts and molding the mouth thread part and the bottom part by means such as compression molding. The laminate can also be formed by a method called Sand-German lamination or extrusion coating. For example, a laminate can be produced by press-bonding a preformed polyethylene terephthalate film and a predetermined polyester film under heat, and then laminating another polyethylene terephthalate film on the surface of the polyester layer. Alternatively, the polyester may be extruded as an intermediate layer between two polyethylene terephthalate films, and the extruded layer may be
A laminated structure can also be obtained by crimping PET film into a sandwich 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 laminate structure of the present invention is particularly useful as a stretch blow-molded container or a stretched sheet-molded container. 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 mandrel of a mold, 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. In addition to obtaining transparency, the presence of the polyester layer containing a specific diol component provides excellent barrier properties against gases such as oxygen, nitrogen, carbon dioxide, and fragrance. Excellent interlayer adhesion is maintained between the layers. In addition, in the sheet forming container, the above-mentioned multilayer film or multilayer sheet is preheated to the above-mentioned stretching temperature, and the heated film or the like 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 temperature was allowed to rise to 250°C for about 1 hour, after which the nitrogen gas supply was stopped and the temperature was increased to 275°C for about 3 minutes under reduced pressure of less than 0.4 mmHg.
Time polymerization was carried out. Table 1 shows the compositions of the acid component and diol component of each of the polyester samples obtained. The final composition of the sample was confirmed by proton NMR and gas chromatography.

[Table] Example 1 Each of the polyester samples shown in Table 1 was sandwiched between two Teflon sheets and molded using a hot press at a temperature 20 to 30°C higher than the melting point or softening point of each resin to a thickness of about 200 mm. A film-like sheet of ~300 μm was prepared. Next, polyethylene terephthalate (intrinsic viscosity 0.91 dl/g in a mixed solvent with a weight ratio of phenol/tetrachloroethane of 50/50) was extruded into a sheet with a thickness of 1.5 mm. The polyester film sheets were inserted between two of the polyethylene terephthalate sheets, stacked one on top of the other, and held in a hot press kept at about 250°C for 120 seconds under no pressure ^.
A laminate with a three-layer structure was created by applying pressure to and holding it for 60 seconds. Further, a part of this laminate was uniaxially stretched twice in the uniaxial direction using a research biaxial stretching device BISTRON BT-1 model manufactured by Iwamoto Seisakusho at a stretching temperature of 120°C. A test piece of 100 mm in length and 10 mm in width was cut out from the obtained sheet immediately after mounting and the sheet further stretched (with the latter so that the stretching axis coincides with the longitudinal direction), and tested at room temperature using a tensile tester. Below, a T-peel test was conducted at a tensile speed of 100 mm/min. Further, the above test piece was stored in an atmosphere of 37°C and 97% relative humidity for one month, and then a similar test was conducted.
Measurements were carried out five times under each condition, and for the sample immediately after preparation and the sample stored for one month in an atmosphere at a temperature of 37°C and a relative humidity of 97%, none of the samples could be peeled off (the intermediate layer, i.e., the polyester layer). cohesive failure). Example 2 Each polyester sample shown in Table 1 was used as the intermediate layer resin, and the polyethylene terephthalate (PET) used in Example 1 was used as the inner and outer layer resin.
An extruder for inner and outer layers with a built-in full-flight screw with a diameter of 38 mm and an effective length of 1430 mm, an extruder for the middle layer with a built-in full-flight screw with a diameter of 38 mm and an effective length of 950 mm, a feed pipe and a triple layer for three layers. Using an extrusion molding device that combines a die, a three-layer pipe of PET/each of the above polyesters/PET is melt-extruded and pre-blow molded in a split mold to produce a pipe with an inner diameter of 27.7 mm, a length of 138 mm, and an average wall thickness. is 3.5
A preform with a bottom of mm was molded. The wall thickness ratio of this preform outer layer: middle layer: inner layer is 2:1:
The extrusion conditions were set so that 2. 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 direction stretch ratio was 3.0 times. Approximately 0.40mm,
A total of 13 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 oxygen gas permeability (Qo ₂ ) and falling velocity (f ₁₀ ) of these sample bottles were measured, and the results are shown in Table 2. 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 storing it in a constant temperature bath at 15% RH for a certain period of time, 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 [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: Oxygen 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】

Claims (1)

[Scope of Claims] 1 (A) Contains polyester mainly composed of ethylene terephthalate units as the inner and outer layers, (B) An acid component consisting of terephthalic acid, isophthalic acid, or a combination thereof, and 5% per total diol component
A copolyester containing in the main chain a diol component consisting of a combination of bis(2-hydroxyethoxy)benzene in an amount of 70 mol% to 70 mol% and other diols mainly consisting of ethylene glycol as an intermediate layer; 1. A resin laminated container characterized by comprising a laminated body provided in an adjacent positional relationship.