JP3153437B2 - Polyester-based multilayer sheet, container, and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester-based multilayer sheet and container having excellent gas barrier properties, strength and secondary processability (container moldability) and high transparency, and a method for producing the same.
In particular, the present invention relates to a polyester-based multilayer sheet suitable as a food packaging material and a container using the same.

[0002]

2. Description of the Related Art Conventionally, thermoplastic polyester resins mainly composed of polyethylene terephthalate have been focused on excellent mechanical properties, transparency, secondary workability, chemical resistance, fragrance retention, hygiene, etc. of the material. It is formed into various films, sheets, containers and the like, and is widely used as a packaging material. In particular, in recent years, due to the problem of environmental pollution caused by incineration of waste, attention has been paid to it as a substitute for vinyl chloride resin, and production has been rapidly increasing.

On the other hand, containers such as cups and trays formed by heating and softening a plastic sheet are used for foods, beverages,
Widely used in the field of pharmaceuticals. Some applications of these thermoformed containers require a gas barrier property against oxygen in order to prevent oxidative deterioration of the package contents.

Hitherto, multilayer sheets having a laminated structure have been used to manufacture these containers having gas barrier properties. Most of them use a multilayer sheet in which an ethylene-vinyl alcohol copolymer is used as an intermediate layer for providing gas barrier properties, and a polypropylene layer is formed on both sides of the intermediate layer via an adhesive layer.

[0005] A container molded from the above-mentioned sheet is excellent in gas barrier properties as compared with a transparent container molded from a thermoplastic polyester sheet, but is insufficient in transparency and is not suitable for applications that emphasize contents transparency. . In addition, the energy generated during incineration is about twice that of polyester, and recycling of containers is not easy, which is not preferable from the viewpoint of environmental suitability. As described above, there has been a demand for a material that can be used for a container that uses a thermoplastic polyester resin having good transparency and has excellent gas barrier properties.

Hitherto, as a method for improving the gas barrier properties of thermoplastic polyester, use of a polyester resin comprising isophthalic acid and ethylene glycol has been proposed. However, although a sheet made of this resin has improved gas barrier properties, it cannot be used alone because mechanical properties such as impact resistance are significantly reduced. Attempts have also been made to co-extrude a thermoplastic polyester and an ethylene-vinyl alcohol copolymer to form a multilayer sheet, but this is difficult because the two types of resin processing temperatures are significantly different.

For this reason, a sheet in which a transparent thermoplastic polyester sheet and a multi-layer gas barrier film are bonded together by a method such as dry lamination is currently used.
However, the additional laminating step not only lowers the productivity but also increases the cost. Further, there is a problem that the transparency after the secondary molding is inferior to that of the single-layer thermoplastic polyester sheet, and the gas barrier property is not stable.

Japanese Patent Application Laid-Open No. 62-62749 discloses a three-layer heat-resistant container in which a polyamide formed from metaxylenediamine and adipic acid is used as an intermediate layer, and polyethylene terephthalate is formed on both surfaces thereof. However, the present invention focuses on the crystallization resistance of polyethylene terephthalate, and the container becomes opaque and is based on a concept different from the object of the present invention. Furthermore, Japanese Patent Publication No. 63-59873 discloses a composite film in which a metaxylylene group-containing polyamide resin formed from metaxylene diamine and adipic acid is used as an intermediate layer, and polyethylene terephthalate is formed on both surfaces thereof, and this is stretched. However, when the metaxylylene group-containing polyamide resin is used alone for the intermediate layer, the unstretched film has low strength and is not practical. Further, the stretched film has a disadvantage that the secondary workability, particularly the deep drawability, is reduced.
Further, there is a disadvantage that a stretching step is required in the manufacturing process, and a manufacturing trouble is likely to occur. As described above, conventionally, it is desired to produce a multilayer sheet and a container using a polyester resin, which is excellent in transparency, excellent in gas barrier properties and strength, and economical. , No container has been found.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester-based multilayer sheet and a container which are excellent in gas barrier properties, strength and secondary workability and have high transparency, and a method for producing the same. The present inventors improve the barrier properties against oxygen without impairing the excellent mechanical properties, transparency, secondary processability, chemical resistance, fragrance retention, hygiene properties, etc. of a thermoplastic polyester resin. As a result of intensive studies, a history of heating a resin composition containing a metaxylylene group-containing polyamide resin and nylon in a specific ratio as an intermediate layer of a multilayer sheet to a temperature of 280 ° C or more and less than 320 ° C. Using a resin composition obtained by giving
This problem has been solved by manufacturing by a specific manufacturing method, and the multilayer sheet and the container of the present invention have been found.

[0010]

Means for Solving the Problems A first invention of the present invention is:
A multilayer sheet comprising at least three thermoplastic resin layers, wherein (A) the surface layer contains a thermoplastic polyester resin having ethylene terephthalate as a main repeating unit,
(B) The intermediate layer comprises the following components (a), (b) and (c), wherein the total amount of the components (a) and (b) is 90% by weight or less and the component (c) is 10% by weight. Over 1% by weight
The intermediate layer at a temperature of 160 ° C. has a (A) 1/2 crystallization time of 10 seconds or more, and (B) an induction time of 6 seconds. The above polyester-based multilayer sheet. Component (a): a metaxylylene group-containing polyamide resin Component (b): a thermoplastic polyamide resin other than the component (a) Component (c): 90 to 50% by weight of the component (a) and 10 to 50% by weight of the component (b) Resin composition obtained by giving a history of heating to a temperature of 280 ° C. or more and less than 320 ° C.

The second invention of the present invention is a multilayer sheet comprising at least three thermoplastic resin layers, wherein (A) the surface layer contains a thermoplastic polyester resin containing ethylene terephthalate as a main repeating unit, and (B) ) The intermediate layer comprises the following components (a), (b) and (c);
Extrusion molding using a resin composition obtained by mixing a total of 90% by weight or less of component (a) and component (b) and a content of more than 10% by weight and less than 100% by weight of component (c). It is a manufacturing method of a sheet. Component (a): a metaxylylene group-containing polyamide resin Component (b): a thermoplastic polyamide resin other than the component (a) Component (c): 90 to 50% by weight of the component (a) and 10 to 50% by weight of the component (b) A resin composition obtained by giving a history of heating to a temperature of 280 ° C. or more and less than 320 ° C. to a resin composition of the present invention. The third invention of the present invention is obtained by thermoforming the polyester multilayer sheet of the first invention. Container. A fourth invention of the present invention is a method for producing a container, wherein the method of the second invention is a first step and the step of thermoforming a polyester-based multilayer sheet is a second step.

Hereinafter, the present invention will be described in detail. The thermoplastic polyester resin having ethylene terephthalate as a main repeating unit as referred to in the present invention generally means terephthalic acid in which 80% by mole or more, preferably 90% by mole or more of the acid component, and 80% by mole or preferably 80% by mole of the glycol component. 90
It means a polyester in which at least mol% is ethylene glycol, and the remaining other acidic components are isophthalic acid, orthophthalic acid, diphenyl ether 4,4′-dicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid Succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, sulfoisophthalic acid, hexahydroxyterephthalic acid, and 1,2-
Propylene glycol, 1,4-butanediol, 1,
5-pentanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polytetramethylene glycol, 1,4-dicyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) It means propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, or a polyester resin containing p-oxybenzoic acid, p-hydroxyethoxybenzoic acid, or the like as an oxyacid. Further, a blend in which ethylene terephthalate is in the above range by blending two or more polyesters may be used.

The thermoplastic polyester resin of the present invention has an intrinsic viscosity of 0.55 or more, preferably 0.65 to 1.3. Intrinsic viscosity is 0.
If it is less than 55, whitening due to crystallization tends to occur during sheet molding, it is difficult to obtain a transparent sheet, and the mechanical strength of the obtained container is also insufficient.

Further, the metaxylylene group-containing polyamide resin used in the present invention comprises: metaxylylenediamine or a mixed xylylenediamine containing metaxylylenediamine and 80 mol% or less of the total amount of paraxylylenediamine;
Α, ω-aliphatic dicarboxylic acid having 6 to 10 carbon atoms in the molecule at least 70 mol% in the molecule
It is a contained polymer.

Examples of these polymers include homopolymers such as polymetaxylylene adipamide, polymetaxylylene secapamide, polymetaxylylene speramide, etc., and metaxylylene / paraxylylene adipamide copolymer. , A copolymer such as meta-xylylene / para-xylylene pimeramide copolymer, a meta-xylylene / para-xylylene azeramid copolymer, and a component of these homopolymers or copolymers and hexamethylene diamine. Aliphatic diamines, cycloaliphatic diamines such as piperazine,
Aromatic dicarboxylic acids such as para-bis- (2-aminoethyl) benzene, lactams such as ε-caprolactam, ω-aminocarboxylic acids such as γ-aminoheptanoic acid, such as para-aminomethylbenzoic acid A copolymer obtained by copolymerizing an aromatic aminocarboxylic acid and the like can be used.
In the above copolymer, paraxylylenediamine accounts for at most 80 mol% based on the total xylylenediamine, and the structural unit formed from xylylenediamine and aliphatic dicarboxylic acid accounts for at least 70 mol% in the molecular chain. It is.

[0016] The metaxylylene group-containing polyamide resin is
It is necessary that the relative viscosity is 1.5 or more, preferably 2.0 to 4.0. If the relative viscosity is less than 1.5, it is difficult to use because it is brittle in an amorphous state.

The above polyamide resin has high gas barrier properties. That is, the meta-xylylene group-containing polyamide resin has a gas barrier property close to that of the conventionally widely used ethylene-vinyl alcohol copolymer, and more notably, in a high humidity environment, ethylene-vinyl alcohol copolymer It has even higher gas barrier properties than vinyl alcohol copolymers. General nylon 6
Do not have such high gas barrier properties.

Furthermore, (B) used for the intermediate layer (b)
As the thermoplastic polyamide resin other than the component (a), nylon 6, nylon 6,6, nylon 6,10,
Polymers such as nylon 11, nylon 12, nylon 4,6, and nylon 6-6,6 copolymer can be used.

In the present invention, it is essential that the intermediate layer contains the component (c), and the component (c) is composed of 90 to 50% by weight of the component (a) and 10 to 50% by weight of the component (b). The resin composition is obtained by giving a history of heating to a temperature of 280 ° C. or more and less than 320 ° C. to the resulting resin composition. The content of the component (c) in the entire intermediate layer is 1
More than 0% by weight and less than 100% by weight, preferably,
15 to 90% by weight. If it is less than 10% by weight, the secondary workability is inferior, and if it is 100% by weight, the productivity of the multilayer sheet and the container deteriorates, and the cost increases. The total amount of the components (a) and (b) in the entire intermediate layer is 90%.
% By weight or less. The proportion of the component (a) in the total amount of the components (a) and (b) is 5 to 100% by weight, preferably 10 to 90% by weight, particularly preferably 15 to 85% by weight. is there. Furthermore, in the present invention, since a resin that has been given a history of heating to a temperature of 280 ° C. or more and less than 320 ° C. is partially used, the temperature at the time of forming a sheet can be reduced to a low level. It is also preferable from the viewpoint of suppressing thermal deterioration of the entire resin.

If the heat history temperature of the resin composition is lower than 280 ° C., strength and secondary workability are not good, and only a sheet having poor transparency can be obtained. Further, there is a disadvantage that the temperature range in which the sheet can be formed by thermoforming such as vacuum forming becomes extremely narrow, and it is impossible to stably form a container or the like. On the other hand, when the heat history temperature is 320 ° C. or higher, there is a disadvantage that the resin is deteriorated, the mechanical properties are reduced, and the discoloration proceeds by heating. By using the intermediate layer of the present invention, in a constant temperature crystallization at a temperature of 160 ° C., a crystallization time is 10 seconds or more, and an induction time is 6 seconds or more in a measurement method by a depolarization intensity method. A certain multilayer sheet is obtained, whereby a transparent multilayer sheet and a container excellent in gas barrier properties, strength and secondary workability are obtained. By setting the half crystallization time of the sheet to 10 seconds or more and the induction time to 6 seconds or more, particularly preferably to the induction time to 10 seconds or more, the container molding time can be selected appropriately, and the quality can be improved. It is possible to manufacture good products.

The time of the heat history of the resin composition of the intermediate layer is not particularly limited, and it is one-half that of the constant temperature crystallization at 160 ° C.
Any conditions may be used as long as a multilayer sheet having a crystallization time of 10 seconds or longer and an induction time of 6 seconds or longer can be obtained.

The component (c) of the intermediate layer is 280 ° C. or higher and 32
It is necessary to go through at least one heat history at a resin temperature of less than 0 ° C. This is presumed to cause a transamidation reaction. POLYMER, 1991, Volume
No. 32, Number 15 2771, when a blend of polymethaxylylenediamine adipamide and nylon 6 was melt-extruded at 290 ° C., the transamidation reaction (interchange reaction) between the two polyamides was carried out.
ion) occurs, resulting in the formation of a block polymer, which results in a clear homogeneous product. According to this report, it is presumed that the resin composition of the intermediate layer of the present invention undergoes an amide exchange reaction to form a block copolymer.

In the resin or resin composition of (A) the surface layer and (B) the intermediate layer, if necessary, a coloring agent, an ultraviolet absorber, an antistatic agent, a thermal antioxidant, an antibacterial agent, a lubricant, and an antiblocking agent And additives such as stabilizers can be contained in an appropriate ratio.

The multilayer sheet of the present invention comprises: (A) a thermoplastic polyester resin having a surface layer containing ethylene terephthalate as a main repeating unit; (B) an intermediate layer having a component (a);
It is composed of component (b) and component (c), and is a mixture of component (a) and component (b) in a total amount of 90% by weight or less and component (c) of more than 10% by weight and less than 100% by weight. It is manufactured by extrusion molding using a resin composition. Further, the polyester-based multilayer sheet is thermoformed to produce a multilayer container. The method for producing the component (c) of the intermediate layer is not particularly limited, and may be performed by any method. For example, there is a method of premixing with a Henschel mixer, mechanically kneading with a Banbury mixer, a twin-screw extruder, or the like, and giving a history of heating to a temperature of 280 ° C. or more and less than 320 ° C.

The multilayer sheet and the container of the present invention use a thermoplastic polyester resin as the inner and outer (A) surface layers, and (B) an intermediate layer composed of the components (a), (b) and (c). It is composed of a resin composition, but if necessary, an adhesive layer generally used can be formed between the intermediate layer and the surface layer.

The multilayer sheet of the present invention can be manufactured and used as a non-stretched sheet and a stretched sheet, but has an advantage that it can be used as a non-stretched sheet. In the multilayer sheet of the present invention, the thickness of the intermediate layer is preferably from 20 μ to 500 μ from the viewpoint of gas barrier properties, and particularly preferably from 40 μ to 300 μ. The thickness of the polyester resin layer forming the surface layer is preferably 50 μm to 1 mm, and particularly preferably 100 μm to 700 μm.
It is. Further, the thickness of the entire sheet is 120 μ to 2.5 mm
And particularly preferably from 240 μm to 1.
7 mm. In addition, it is preferable that the composition ratio of the sheet is set to be equal to or less than 1/2 that of the polyester resin in terms of oxygen permeability from the viewpoint of protecting the contents.

In order to produce the multilayer sheet of the present invention, a conventional lamination method such as coextrusion, dry lamination and extrusion lamination can be employed. As the co-extrusion method, an apparatus provided with a plurality of extruders and dies is usually used, but a multi-manifold method, a feed block method and the like are generally adopted.

The container of the present invention is formed by ordinary thermoforming using the multilayer sheet obtained by the present invention, for example, vacuum forming, pressure forming, vacuum pressure forming, plug assist forming, press forming and the like.

[0029]

The present invention will be described in detail with reference to the following examples. First, methods for measuring sheet properties and container properties will be described. (1) 1/2 crystallization time: The resin composition of the intermediate layer was separated from the multilayer sheet, and the test piece was used to measure the depolarization intensity using a polymer crystallization rate measuring device (model: MK701) manufactured by Kokita Seisakusho. (Polymer Chemistry, (1972), vol. 2)
9, No. 325, 336). The test piece at room temperature was placed in a crystallization bath at 160 ° C., heated, crystallized at 160 ° C., and the time from immersion in the crystallization bath to 結晶 crystallization was determined. (2) Induction time: In the same measurement as in (1), the time from immediately after immersion in the crystallization bath to the start of crystallization was determined.

(3) Total light transmittance and haze: The haze meter MODEL NDH-2D manufactured by Tokyo Denshoku Co., Ltd. was used and calculated according to the following equation in accordance with JIS-K7105. In addition, about the container, the bottom was cut out and measured. Total light transmittance = T2 / T1 × 100 (%) T1: incident light amount T2: total light transmission amount T3: scattered light amount by device T4: scattered light amount by device and sample

(4) Vacuum formability: PLA manufactured by Sanwa Kogyo Co., Ltd.
A VAC FE-36PH vacuum forming machine was equipped with a round cup-shaped mold (container dimensions; 90 mmφ × 70 mm height),
23 ° C x 50
A sheet having an appropriate heating temperature range of 30 ° C. or more when vacuum forming was performed using a sheet stored for 1 week in a% RH environment was rated as good (）), and a sheet with a temperature lower than 30 ° C. was rated as poor (×). (5) Oxygen permeability: US MODERN CONTOR
OX-TRAN10 / 50 Oxygen Permeability Analyzer OX-TRAN
According to A, it measured on condition of the following. Sheet: 23 ° C, 70% relative humidity Container: 23 ° C, 70% internal relative humidity, 50% external relative humidity
% Container shape: Conical shape with mouth diameter 120mm, bottom diameter 110mm and height 90mm

(6) Sheet impact strength: manufactured by Toyo Seiki Co., Ltd.
Using a DuPont impact tester, measure with a punch tip radius of 6.3 mm in accordance with JIS-K7211, and measure 50%
The breaking energy (J) was determined.

(7) 50% breaking height (container impact strength): A container formed by the method of (3) is filled with 350 ml of pure water, the upper surface of the container is heat-sealed, and then dropped on a vinyl chloride floor. 50% according to JIS-K7211
The breaking height (cm) was determined.

(8) Intrinsic viscosity of polyester resin (I
V): The measurement resin was mixed with a phenol / tetrachloroethane (weight ratio; 50/50) mixed solvent having a solution viscosity of 0.5.
g / 10 ml, and shows the viscosity measured using a Ubbelohde viscometer in a thermostat at 30 ° C.

(9) Relative viscosity of polyamide resin (ηrel
): Dissolve 1 g of resin in 100 ml of 96% by weight sulfuric acid.
Relative viscosity measured at 5 ° C.

EXAMPLE 1 50 mol% of terephthalic acid, ethylene glycol 4 as a thermoplastic polyester constituting the surface layer (outer layer and inner layer)
Polyethylene terephthalate (hereinafter abbreviated as PET) having an IV of 0.80 and comprising 7.5 mol% and 1.5 mol% of 1,4-cyclohexanedimethanol was used. As the metaxylylene group-containing polyamide resin of the component (a) of the intermediate layer, 45 parts by weight of polymetaxylylene adipamide (hereinafter abbreviated as MXD6) with η rel = 2.7 was used, and nylon 6 (hereinafter referred to as Ny6) was used as the component (b). Abbreviated.), Ηrel =
Using 5 parts by weight of 3.8, and as a component (c), a mixture in which the ratio of MXD6 / Ny6 is 50% by weight / 50% by weight is kneaded at 290 ° C. with a twin-screw kneader,
50 parts by weight given the heat history were used. These (a)
The mixture composed of the component, the component (b) and the component (c) was used as an intermediate layer. Using these materials, a multilayer sheet molding equipment is used, and a multilayer sheet having a thickness of 1.0 mm, in which the thickness composition ratio of two layers and three layers is outer layer: intermediate layer: inner layer = 3: 1: 3 by coextrusion method. Was molded. The processing temperature (molten resin temperature) for this sheet was 275 ° C. for the intermediate layer and 275 ° C. for the surface layer.
° C. Table 1 shows the mixing ratio of the resin constituting the sheet,
Shows sheet properties and container properties. Examples 2 to 6 In Example 1, the components (a), (b) and (c)
The same procedure was performed except that the mixing ratio of the components was changed. Table 1 shows the mixing ratio of the resin constituting the sheet, the sheet properties and the container properties.

Comparative Examples 1 to 3 In Example 1, the components (a), (b) and (c)
The same procedure was performed except that the mixing ratio of the components was changed. Table 2 shows the mixing ratio of the resin constituting the sheet, the sheet properties and the container properties. Comparative Example 4 In Example 1, the components (a), (b) and
MXD6 / Ny using component (d) instead of component (c)
6 is 50% by weight / 50% by weight
The same operation was performed except that 50 parts by weight kneaded at 270 ° C. with a shaft kneader was used. Table 2 shows the mixing ratio of the resin constituting the sheet, the sheet properties and the container properties.

[0038]

[Table 1] (Note 1) The unit is cc / pkg ・ day ・ atm (one container)

[0039]

[Table 2] (Note 1) The unit is cc / pkg ・ day ・ atm

[0040]

As described above, the polyester-based multilayer sheet of the present invention and its container are excellent in gas barrier properties, strength and secondary workability (container moldability) and have high transparency. Yes, this is a multilayer sheet and container particularly suitable as a food packaging material.

Continuation of the front page (56) References JP-A-7-223305 (JP, A) JP-A-9-156058 (JP, A) JP-A-8-300584 (JP, A) JP-A-4-103348 (JP) , A) JP-A-4-198329 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 51/00-51/46

Claims (4)

(57) [Claims] 1. A multilayer sheet comprising at least three thermoplastic resin layers, (A) a surface layer containing a thermoplastic polyester resin having ethylene terephthalate as a main repeating unit, and (B) an intermediate layer having the following ( a) components,
A resin composition comprising component (b) and component (c), wherein the total amount of component (a) and component (b) is 90% by weight or less and component (c) is more than 10% by weight and less than 100% by weight. (A) the crystallization time at 160 ° C. of the resin composition of the intermediate layer is not less than 10 seconds, and
(B) A polyester multilayer sheet, wherein the induction time is 6 seconds or more. Component (a): a metaxylylene group-containing polyamide resin Component (b): a thermoplastic polyamide resin other than the component (a) Component (c): 90 to 50% by weight of the component (a) and 10 to 50% by weight of the component (b) Resin composition obtained by giving a history of heating to a temperature of 280 ° C. or more and less than 320 ° C. 2. A multilayer sheet comprising at least three thermoplastic resin layers, wherein (A) the surface layer contains a thermoplastic polyester resin containing ethylene terephthalate as a main repeating unit, and (B) the intermediate layer has the following ( a) components,
It is composed of component (b) and component (c), and is a mixture of component (a) and component (b) in a total amount of 90% by weight or less and component (c) of more than 10% by weight and less than 100% by weight. A method for producing a polyester-based multilayer sheet, which is extruded using a resin composition. Component (a): a metaxylylene group-containing polyamide resin Component (b): a thermoplastic polyamide resin other than the component (a) Component (c): 90 to 50% by weight of the component (a) and 10 to 50% by weight of the component (b) Resin composition obtained by giving a history of heating to a temperature of 280 ° C. or more and less than 320 ° C. 3. A container obtained by thermoforming the polyester-based multilayer sheet according to claim 1. 4. A method for producing a container, wherein the method according to claim 2 is the first step, and the step of thermoforming the polyester multilayer sheet is the second step.