JPH0715051B2 - Thermoplastic packaging material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermoplastic resin packaging material having excellent mechanical properties, high gas barrier properties, high water vapor barrier properties, and high surface gloss. Is.

[Problems to be Solved by Prior Art and Invention]

Polyolefin resins typified by polyethylene and polypropylene and polyester resins typified by polyethylene terephthalate are often used in packaging materials currently manufactured. A packaging material using a polyolefin resin is characterized in that the resin raw material is inexpensive and can be easily molded, and is now widely used in containers such as liquid detergents.
However, since the polyolefin resin is inferior in strength, its wall thickness cannot be reduced for use in a container.
In addition, since it has a poor gas barrier property against oxygen and carbon dioxide, it has a drawback that it cannot be used for packaging things that deteriorate with oxygen, such as food.

On the other hand, a polyester resin can be biaxially stretch-molded due to its excellent characteristics, and can be molded into a high-strength sheet or a thin container. Polyester resins generally have higher gas barrier properties against oxygen and carbon dioxide than polyolefin resins and are also used as food packaging materials such as soy sauce and carbonated drinks. However, the polyester resin has a poorer water vapor barrier property than the polyolefin resin, and cannot be used for a substance that dislikes moisture and a composition change of contents caused by evaporation of water poses a problem.

Further, there is a method of laminating an aluminum foil or a high barrier resin in order to improve the gas and water vapor barrier properties, but it is generally unavoidable that the manufacturing process becomes complicated. Further, JP-B-61-39336 describes a thermoplastic resin container having a metallic luster, which is made of a polyester resin and a polyolefin resin. However, simply mixing a polyester resin and a polyolefin resin does not provide good adhesion between the two resins, and it is not possible to obtain a container with sufficient strength such as the surface of the container peeling off easily with cellophane tape or the like. . Further, JP-A-62-153338 discloses a resin composition containing a polyester resin and a polyolefin resin, a glycidyl group-containing copolymer and a fatty acid ester or a partially saponified product thereof. However, this publication is for improving the slipperiness of the polyester resin, and the water vapor barrier property of the polyester resin is hardly improved in the resin composition having the compounding ratio described.

As described above, in the conventional technique, it was not possible to obtain a well-balanced resin composition packaging material having both high gas barrier properties and water vapor barrier properties and excellent mechanical properties such as mechanical strength, impact resistance and surface peeling. .

Therefore, there is a demand for a packaging material having mechanical properties equivalent to or better than those of conventional ones, and having excellent gas barrier properties and water vapor barrier properties. In order to industrially manufacture and use this packaging material, it is an essential condition that it can be molded by a simple molding method and has an excellent appearance.

[Means for Solving the Problems]

As a result of intensive studies conducted by the present inventors in view of the above situation,
Polyester resin, polyethylene, and ethylene and α,
It has been found that a packaging material molded using a thermoplastic resin composition comprising a glycidyl group-containing copolymer having a glycidyl ester of β-unsaturated carboxylic acid as an essential component can achieve the above object, and the present invention is achieved. completed.

That is, the present invention is 10 to 90% by weight of the polyester resin (A).
A glycidyl group-containing copolymer containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential constituents with respect to 100 parts by weight of a resin composition composed of 100% by weight of polyethylene and 90% by weight of polyethylene (B). The present invention provides a thermoplastic resin packaging material comprising a resin composition containing 1 to 30 parts by weight of (C).

The polyester resin (A) used in the present invention is a thermoplastic polymer or copolymer obtained by condensation polymerization of dicarboxylic acid (or its derivative) and diol (or its derivative) as main reaction components. Here, as the dicarboxylic acid, an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, phthalic acid, or naphthalenedicarboxylic acid, an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, or an aliphatic dicarboxylic acid such as adipic acid or sebacic acid is used alone. Alternatively, a mixture of two or more kinds may be used. As the diol component, ethylene glycol, 1,3-propanediol, 1,4
Examples include aliphatic glycols such as butanediol, neopentyl glycol, 1,5-pentanediol, and 1,6-hexanediol, and alicyclic glycols such as 1,4-cyclohexanediol, or a mixture of two or more thereof. .
Among the combinations of the above reaction components, aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate and polyethylene-2,6-naphthalate are preferable, and among them, polyethylene terephthalate, polyethylene isophthalate or a mixture thereof is preferable. However, the term "polyethylene isophthalate" as used herein means that 50 mol% or more of the dicarboxylic acid component is isophthalic acid, and the remaining dicarboxylic acid component is one or more compounds selected from the above dicarboxylic acids, preferably terephthalic acid. A polyester composed of

The polyester resin (A) preferably has an intrinsic viscosity (IV) in the range of 0.4 to 1.8 dl / g in a phenol-tetrachloroethane (weight ratio 6: 4) mixed solvent at 25 ° C.,
The range of 0.6 to 1.5 dl / g is more preferable. The intrinsic viscosity
If it is less than 0.4 dl / g, the strength of the packaging material is not sufficient, and 1.8 dl / g
If it exceeds, the melt viscosity is too high and molding is difficult.

The polyethylene (B) used in the present invention includes low density polyethylene obtained by the high pressure method, linear low density polyethylene which is a copolymer of ethylene and α-olefin obtained by the medium and low pressure methods, and medium and low pressure methods. In addition to the high / medium density polyethylene obtained by the above, modified polyethylene composed of a copolymer of ethylene and a vinyl compound can be mentioned.

The vinyl compounds referred to here are vinyl ethers; vinyl esters such as vinyl acetate and vinyl propionate;
Esters of acrylic acid and methacrylic acid such as methyl, ethyl, propyl, and butyl; acrylonitrile, styrene, acrylic acid and methacrylic acid, and metal salts thereof, including glycidyl esters of α, β-unsaturated carboxylic acids Absent.

Among the above polyethylene and modified polyethylene, high
Medium or low density polyethylene is preferred.

The polyethylene (B) used in the present invention preferably has a melt viscosity of 0.01 to 30 g / 10 min in melt flow rate (MFR), and more preferably 0.1 to 20 g / 10 min.

The ethylene in the glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as an essential constituent in the present invention contains 10 mol% of an olefin component copolymerizable with ethylene. Less than may be included. The glycidyl ester of α, β-unsaturated carboxylic acid has the general formula (Wherein R is a hydrogen atom, a lower alkyl group or a lower alkyl group having a substituent such as a carboxyl group or a glycidyl ester group). Specifically, it is glycidyl acrylate, glycidyl methacrylate, glycidyl itaconate, and the like, and glycidyl methacrylate is most preferable. The copolymerization amount of the glycidyl ester of α, β-unsaturated carboxylic acid in the glycidyl group-containing copolymer (C) is 1 to 50% by weight, preferably 2 to 30% by weight. Further, if it is 40% by weight or less, one or more kinds of unsaturated monomers copolymerizable with the monomer may be copolymerized. Examples of unsaturated monomers include vinyl ethers, vinyl acetate, vinyl propionate, and other vinyl esters, methyl, ethyl, propyl, butyl, and other acrylic acid and methacrylic acid esters, acrylonitrile, styrene, carbon monoxide, and the like. Vinyl acetate is most preferred.

Preferred examples of the glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components in the present invention include ethylene / glycidyl methacrylate copolymer and ethylene / Vinyl acetate / glycidyl methacrylate copolymer, ethylene /
Examples thereof include glycidyl acrylate copolymer and ethylene / vinyl acetate / glycidyl acrylate copolymer.

The glycidyl group-containing copolymer (C), which contains ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as an essential component, has good compatibility with the polyester resin (A) and the polyethylene (B). Acts as a compatibilizing agent, the phase structure is kept stable by the interphase adhesive action, and the obtained packaging material has excellent mechanical strength and appearance.

The blending amount of the polyester resin (A) and polyethylene (B) used in the thermoplastic resin packaging material of the present invention is 10/9 in terms of the weight ratio of the polyester resin (A) and the polyethylene (B).
0 to 90/10. When the polyester resin (A) is less than 10% by weight, the strength of the packaging material is insufficient and the gas barrier property is low, and when it exceeds 90% by weight, the water vapor barrier property is poor. Further, the blending amounts of the polyester resin (A) and polyethylene (B) used in the thermoplastic packaging material of the present invention molded by a molding method involving stretching such as a biaxial stretch blow molding method are the same as those of the polyester resin (A). The weight ratio of polyethylene (B) is preferably 50/50 to 90/10. When the polyester resin (A) is less than 50% by weight, stretchability is poor and molding is difficult.

The amount of the glycidyl group-containing copolymer (C) containing ethylene and the glycidyl ester of α, β-unsaturated carboxylic acid used as the thermoplastic resin packaging material of the present invention as essential components is the polyester resin (A ) And polyethylene (B) in total of 1 to 30 parts by weight, preferably 2 to 20 parts by weight, per 100 parts by weight. When the amount is less than 1 part by weight, the compatibility, interphase adhesion, mechanical strength, impact resistance and the like of the composition are not sufficient, and there is a problem in practical use. On the other hand, if the amount is more than 30 parts by weight, the effect is not improved and the mechanical strength is rather lowered.

One or more kinds of additives can be added to the thermoplastic resin packaging material of the present invention within a range not impairing the object of the present invention. Here, the additive is often used in plastic molded articles, and examples thereof include an antioxidant, a heat stabilizer, an ultraviolet absorber, a dye or pigment, and an antistatic agent.

The thermoplastic resin packaging material of the present invention means a film, a tube, a molding container or the like made of the resin composition having the above-mentioned mixing ratio. Here, the molding container includes a blow molding container such as extrusion blow molding and biaxial stretch blow molding, and a sheet molding container such as vacuum molding and pressure molding.

The thermoplastic resin packaging material of the present invention comprises a polyester resin (A), polyethylene (B), and ethylene and α, β-.
It is an essential condition to include a glycidyl group-containing copolymer (C) containing a glycidyl ester of an unsaturated carboxylic acid as an essential component, and it is necessary to mix these resins during or before molding. As a mixing method, a dry blend of each resin in a predetermined weight ratio may be directly kneaded in an extruder during a melt processing operation at the time of molding, but in that case, extrusion which can be sufficiently kneaded It is necessary to select the screw and / or extrusion conditions. In order to sufficiently knead and obtain a uniform resin packaging material, it is preferable to perform sufficient kneading in advance with a twin-screw extruder or the like and then perform molding using the resin composition in powder or pellet form.

When the packaging material of the present invention is a container, a packaging material having the target sufficient strength, gas / water vapor barrier properties, and weak surface gloss can be obtained by the extrusion blow molding method, but the extrusion or injection molding method can be used. After the reform is made, the packaging material molded by the stretch blow molding method has better performance. It is considered that this is because the stretching of the polyester chains and the polyethylene chains causes the movement of the molecular chains to be suppressed and the diffusion of gas and water vapor in the resin to be suppressed.

Further, the packaging material obtained by stretch blow molding has a pearl-like high gloss appearance stronger than that of extrusion blow molding. It is considered that this is because the polyester and polyethylene phases are oriented in layers by stretching and the incident light is reflected multiple times at the interface between the phases, and the reflected lights interfere with each other.

Examples of the thermoplastic resin packaging material of the present invention include packaging films used for foods and the like, and containers such as bottles and cups used for cosmetics and foods and drinks. In particular,
It is suitable for packaging and filling products that are easily adversely affected by oxygen and water vapor, or for packaging products that require a beautiful appearance.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples, but these Examples do not limit the present invention in any way.

The resin compositions used for molding the packaging materials of Examples and Comparative Examples were all melt-kneaded in advance, pelletized and then dried. PCM45-32 manufactured by Ikegai Tekko Co., Ltd. for kneading
Using a twin-screw extruder, kneading was carried out at a temperature of 280 ° C.

The resins used in Examples and Comparative Examples and their abbreviations are as follows.

Polyester resin (A) a: Polyethylene terephthalate IV = 1.4 dl / gb: Polyethylene terephthalate IV = 0.75 dl / gc: Polyester IV obtained by condensation polymerization of a terephthalic acid / isophthalic acid (10/90) mixture and ethylene glycol 0.85dl / g Polyethylene (B) d: High-density polyethylene MFR = 0.3g / 10min e: Low-density polyethylene MFR = 1.0g / 10min Ethylene and α, β-glycidyl ester of unsaturated carboxylic acid as essential constituents Glycidyl group-containing copolymer (C) f: ethylene / methacrylic acid glycidyl ester (90/1
0) Copolymer g: ethylene / vinyl acetate / methacrylic acid glycidyl ester (90/5/5) copolymer The test methods used in Examples and Comparative Examples are as follows.

Oxygen permeability test of film According to JIS K7126 A method, oxygen permeability coefficient (unit: cm ³ mm / m
² 24h atm).

Water vapor permeability test of film According to JIS Z0208, moisture permeability was determined. The value obtained by multiplying the thickness of the film was used as the water vapor permeability (unit: gmm / m ² 24h) in order to correct for the thickness.

Buckling strength test of bottles Bottles filled with water were capped and subjected to a compression test of bottles using UCT-100 type Tensilon manufactured by Orientec Co., Ltd. The primary buckling strength was calculated and the average value of 5 containers was calculated.

Oxygen Permeability Test of Bottle Using a gas permeability tester GPM250 manufactured by Gas Black Industry Co., Ltd., the oxygen permeability coefficient of the bottle at 23 ° C. and normal pressure was measured. In order to compare the measured values of various containers, divide by the surface area of each container, and multiply the average value of the wall thickness of each container with the oxygen permeability coefficient (unit: cm ³ mm / m ² 24h atm) did.

Water vapor permeability test of bottles Bottles with calcium chloride sealed and sealed at 40 ° C and relative humidity of 90
% Indoors. Weigh the container every other day,
The weight gain per day was determined. To compare the measured values of various containers, divide by the surface area value of each container, and then multiply the average value of the wall thickness of each container by the water vapor permeability (unit: gmm / m ² 2
4h).

Cellotape surface peeling test Relative humidity 65%, in the vertical direction of the container left overnight at 20 ℃,
A cellophane tape (width: 18 mm) 20 cm manufactured by Nichiban Co., Ltd. was attached so as not to entrap air bubbles, and was peeled off abruptly from the upper part, and the degree of peeling was evaluated by the area ratio of the container surface peeled together with the tape.

◎: No peeling at all ○: 1/10 or less peeling ×: 1/10 to 1/2 peeling × ×: 1/2 or more peeling Appearance The presence or absence of pearly luster was evaluated.

Examples 1 to 6 and Comparative Examples 1 to 4 Polyester resin (A), polyethylene (B), glycidyl group-containing copolymers containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential constituent components ( The thermoplastic resin composition containing C) in the proportion shown in Table 1 was press-molded to form a film having a thickness of about 0.1 mm. The test results of these films are shown in Table 2.

The films shown in Examples 1 to 6 have a low oxygen permeability and a low water vapor permeability, and have a better balance of barrier properties than the film made of polyethylene terephthalate or high-density polyethylene alone (Comparative Example 1 or 2). Even a film made of a resin composition containing a small amount of polyethylene (Comparative Example 3) does not have sufficient water vapor barrier properties. Further, a film made of a resin composition containing no glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components was molded (Comparative Example 4). It was very brittle and a permeability test was impossible.

Examples 7 to 12 and Comparative Examples 5 to 7 Polyester resin (A), polyethylene (B), glycidyl group-containing copolymer containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components ( The thermoplastic resin composition containing C) in the proportion shown in Table 1 was subjected to extrusion blow molding, and the capacity was 600 ml, the width of the body was about 96 mm, the depth of the body was about 52 mm, the height was 235 mm, and the diameter of the mouth was 27 m.
An m flat bottle was molded. Tahara Seisakusho Co., Ltd. Bu-7054M-
Using a 70φ extrusion screw in the P molding machine, melt temperature 280
C., the mold temperature was 20 to 40.degree. The test results of these containers are shown in Table 3.

As a comparative example, a bottle made of only a polyethylene or a resin composition not containing a glycidyl group-containing copolymer (C) having ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components is molded, The test results are also shown in Table 3.

The bottles of the present invention obtained in Examples 7 to 12 were good in terms of buckling strength, oxygen permeability and water vapor permeability, but ethylene and an α, β-unsaturated carboxylic acid glycidyl ester were essential components. Glycidyl group-containing copolymer (C) as a component
Bottles made of a resin composition not containing (Comparative Examples 5 and 6) were very weak and could not be practically used. Further, the polyethylene bottle (Comparative Example 7) showed a large oxygen permeability. Regarding the appearance of the container, weak pearly luster was observed in the examples and Comparative examples 5 and 6.

Examples 13 to 18 and Comparative Examples 8 to 11 Polyester resins (A), polyethylene (B), glycidyl group-containing copolymers containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential constituents ( A thermoplastic resin composition containing C) in the proportions shown in Table 1 was injection-molded at a melting temperature of 280 ° C and a mold temperature of 20 to 40 ° C to obtain a preform having an outer diameter of 27 mm, a length of 115 mm and a wall thickness of 3 mm. Was molded. Subsequently, the preform is stretched axially with a stretching rod at 100 ° C., and at the same time, biaxial stretch blow molding is performed in which compressed air of 5 to 15 atm is blown into the preform to expand it, and the capacity is 600 ml, the diameter of the body part is 62 mm, 220m height
A cylindrical bottle having m and a mouth diameter of 27 mm was molded. An injection blow molding machine manufactured by Nissei ASB Machine Co., Ltd. was used as a molding machine. The test results of these containers are shown in Table 4.

As a comparative example, a resin composition containing only a small amount of a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components, polyethylene terephthalate alone, or a proportion of polyethylene Table 4 also shows the results of a test conducted by molding a bottle made of a resin composition having a low content.

The bottles of the present invention obtained in Examples 13 to 18 had good buckling strength, oxygen permeability and water vapor permeability, and had a beautiful appearance with strong pearly luster. On the other hand, a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components is
Bottles made of a resin composition containing only 0.5 part by weight (Comparative Examples 8 and 9) were very weak and could not be put to practical use. Polyethylene terephthalate bin (Comparative Example 10) showed a large water vapor permeability. Furthermore, a bottle made of a resin composition having a lower proportion of polyethylene (Comparative Example 11)
Showed a large water vapor permeability, and the appearance was translucent and milky white, which was not preferable.

Claims (4)

[Claims] 1. A resin composition 10 comprising 10 to 90% by weight of a polyester resin (A) and 90 to 10% by weight of a polyethylene (B).
A resin composition in which 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components is blended with 0 part by weight. A thermoplastic resin packaging material characterized by the above. 2. A resin composition 10 comprising 10 to 90% by weight of a polyester resin (A) and 90 to 10% by weight of a polyethylene (B).
A resin composition in which 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components is blended with 0 part by weight. A thermoplastic resin container characterized by the above. 3. A resin composition 10 comprising 50 to 90% by weight of a polyester resin (A) and 50 to 10% by weight of a polyethylene (B).
A resin composition containing 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as an essential component is stretched with respect to 0 part by weight. A thermoplastic resin packaging material characterized by being formed. 4. A resin composition 10 comprising 50 to 90% by weight of a polyester resin (A) and 50 to 10% by weight of a polyethylene (B).
A resin composition containing 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as an essential component is stretched with respect to 0 part by weight. A thermoplastic resin container, characterized by being formed by a blow molding method.