JPH05306360A - Thermoplastic resin packaging material - Google Patents

Abstract

PURPOSE:To obtain a packaging material excellent in mechanical characteristics and elevated gas barrier properties, and composed of a composition obtained by blending a specific resin composition with a specific amount of a specific glycidyl containing copolymer. CONSTITUTION:A resin composition made by blending (A) a resin composition composed of (i) 10-90wt.% polyester resin (preferably the resin having 0.6-1.5dl/g intrinsic viscosity at 25 deg.C in a mixed solvent consisting of phenol- tetrachloroethane (weight ratio 6:4) and (ii) 90-10% polyethylene (preferably a low density polyethylene having a melt viscosity given by 0.1-20g/10min. flow rate) and (B) 1-30 parts (preferably 2-20 parts) glycidyl containing copolymer having ethylene and a glycidyl ester of a beta-unsaturated carboxylic acid (preferably glycidyl methacrylate) as essential components is drawn to obtain the objective packaging material.

Description

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

[Problems to be Solved by Conventional Techniques and Inventions]

 Polyolefin resin typified by polyethylene and polypropylene and polyester resin typified by polyethylene terephthalate are often used in packaging materials currently manufactured.

 Packaging materials using polyolefin resins are characterized by inexpensive resin raw materials and easy molding, and are 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, carbon dioxide and the like, it has a drawback that it cannot be used for packaging such as foods which are deteriorated by oxygen.

 On the other hand, polyester resin can be biaxially stretch-molded due to its excellent properties and can be molded into high-strength sheets and thin-walled containers. 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, polyester resins have poorer water vapor barrier properties than polyolefin resins, and could not be used for those that hate moisture or those where the composition change of contents due to water evaporation poses a problem.

 There is also 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 is complicated. Further, Japanese Patent Publication No. 61-39336 discloses a thermoplastic resin container having a metallic luster, which is made of a polyester resin and a polyolefin resin. However, simply mixing the polyester resin and the polyolefin resin does not improve the adhesion between the two resins, and it is necessary to obtain a container with sufficient strength such as the surface of the container easily peeling off with cellophane tape. I can't. Further, JP-A-62-153338 discloses a resin composition containing a polyester resin and a polyophine resin and a glycidyl group-containing copolymer and a fatty acid ester or a partially saponified product thereof. However, this publication is intended to improve the slipperiness of the polyester resin, and the water vapor barrier property of the polyester resin was hardly improved in the resin composition having the described blending ratio.

 As described above, the conventional technology does not provide a well-balanced resin composition packaging material that has both high gas barrier properties and water vapor barrier properties, as well as mechanical properties such as mechanical strength, impact resistance, and surface peeling. I couldn't.

 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 indispensable that it can be molded by a simple molding method and has excellent appearance.

[Means for Solving the Problems]

 As a result of intensive studies in view of the above circumstances, the present inventors have found that polyester resin, polyethylene, and a glycidyl group containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as an essential constituent component. The present invention has been completed by finding that a packaging material molded using a thermoplastic resin composition comprising a contained copolymer can achieve the above object.

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

 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, dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid, and alicyclic dicarbonic acids such as cyclohexanedicarboxylic acid, adipic acid, and sebacic acid. The group dicarboxylic acid may be a single type or a mixture of two or more types. Examples of diol components include aliphatic glycols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,5-pentanediol, and 1,6-hexanediol, and 1,4-cyclohexane. Examples thereof include alicyclic glycols such as diol, and a mixture of two or more kinds. Among the combinations of the above-mentioned reaction components, aromatic polyesters such as polyethylene terephthalate, polybutylene terephthalate, polyethylene isophthalate and polyethylene-2,6-naphthalate are preferred, and among them, polyethylene terephthalate, polyethylene isophthalate or Mixtures thereof are preferred. 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 an acid.

 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, and preferably 0.6 to 1.5 dl. The range of / g is more preferable. If the intrinsic viscosity is less than 0.4 dl / g, the strength of the packaging material is not sufficient, and if it exceeds 1.8 dl / g, 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 obtained by the medium-low pressure method, which is a copolymer of ethylene and α-olefin, and medium -In addition to high and medium density polyethylene obtained by the low pressure method, modified polyethylene composed of a copolymer of ethylene and a vinyl compound can be mentioned.

 Vinyl compounds here include vinyl ethers; vinyl ester acids such as vinyl acetate and vinyl propionate; esters such as methyl, ethyl, propyl and butyl of acrylic acid and methacrylic acid; acrylonitrile, styrene and acrylic acid. And methacrylic acid and metal salts thereof, but does not include glycidyl ester of α, β-unsaturated carboxylic acid.

 Among the above polyethylenes and modified polyethylenes, high / medium density or low density polyethylene is preferable.

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

The ethylene in the glycidyl group-containing copolymer (C) containing ethylene and the glycidyl ester of α, β-unsaturated carboxylic acid used in the present invention as essential components is an olefin component which can be copolymerized with ethylene. May be contained in less than 10 mol%. 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. In the glycidyl group-containing copolymer (C), the amount of the glycidyl ester of α, β-unsaturated carboxylic acid copolymerized is appropriately in the range of 1 to 50% by weight, preferably 2 to 30% by weight. One or more unsaturated monomers copolymerizable with the monomer may be copolymerized as long as it is 40% by weight or less.

 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. It can be exemplified, and vinyl acetate is most preferable.

 A preferred example of the glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of α, β-unsaturated carboxylic acid as essential components in the present invention is ethylene / glycidyl methacrylate copolymer. Copolymers, ethylene / vinyl acetate / glycidyl methacrylate copolymers, ethylene / glycidyl acrylate copolymers, ethylene / vinyl acetate / glycidyl acrylate copolymers and the like can be mentioned.

 Glycidyl group-containing copolymer (C), which contains ethylene and glycidyl ester of α, β-unsaturated carboxylic acid as essential constituents, had good compatibility with polyester resin (A) and polyethylene (B). Therefore, it acts as a compatibilizer for both components, and the phase structure is kept stable by the interphase adhesive action, and the resulting packaging material has excellent mechanical strength and appearance.

 The amount of polyester resin (A) and polyethylene (B) used in the thermoplastic resin packaging material of the present invention is 10/90 to 90/10 in terms of the weight ratio of polyester resin (A) and polyethylene (B). .. If 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 if it exceeds 90% by weight, the water vapor barrier property is poor. Further, the blending amount 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, is the same as that of the polyester resin (A And the weight ratio of polyethylene (B) is preferably 50/50 to 90/10. When the polyester resin (A) is less than 50% by weight, the 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 total amount of the resin (A) and polyethylene (B) is 1 to 30 parts by weight, preferably 2 to 20 parts by weight, based on 100 parts by weight. If the amount is less than 1 part by weight, the compatibility, interphase adhesion, mechanical strength, impact resistance, etc. of the composition are not sufficient, and there is a practical problem. 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 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 a plastic molded product, and is, for example, an antioxidant, a heat stabilizer, an ultraviolet absorber, a pigment or a pigment, an antistatic agent and the like.

 The thermoplastic resin packaging material of the present invention refers to 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 blow molding containers such as extrusion blow molding and biaxial stretch blow molding, and sheet molding containers such as vacuum molding and pressure molding.

 The thermoplastic resin packaging material of the present invention comprises a polyester resin (A), polyethylene (B), and a glycidyl group-containing copolymer containing ethylene and a glycidyl ester of an α, β-unsaturated carboxylic acid as essential components. It is an essential condition to include the coalescence (C), and it is necessary to mix these resins at the time of molding or before molding. As a mixing method, dry blending of each resin in a predetermined weight ratio may be directly kneaded in the extruder during the 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 that the resin composition is preferably kneaded in advance with a twin-screw extruder or the like and then molded using the resin composition in powder or pellet form.

 When the packaging material of the present invention is a container, the extrusion blow molding method can also provide a packaging material having the target sufficient strength, gas / water vapor barrier property, and weak surface gloss, but the extrusion or injection molding method can be used. After the preform is made, the packaging material formed by the stretch blow molding method has better performance. This is considered to be because the stretching of the polyester and 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.

 Furthermore, the packaging material obtained by stretch blow molding has a pearly, 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, the incident light is reflected multiple times at the interface of each phase, 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. A PCM45-30 twin-screw extruder manufactured by Ikegai Tekko KK was used for kneading, and the kneading temperature was 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 / g b: Polyethylene terephthalate IV = 0.75 dl / g c: Polyester obtained by condensation polymerization of a mixture of terephthalic acid / isophthalic acid (10/90) and ethylene glycol IV = 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 are essential Glycidyl group-containing copolymer (C) f: Ethylene / glycidyl methacrylate ester (90/10) 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 The oxygen permeability coefficient (unit: cm ³ mm / m ² 24 h atm) was determined according to JIS K7126 Method A.

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

 ○ Bottle buckling strength test A bottle filled with water was capped, and a bottle compression test was performed using UCT-100 type Tensilon manufactured by Orientec Co., Ltd. The primary buckling strength was determined and the average value of 5 containers was calculated.

○ Bottle oxygen permeability test Using a gas permeability tester GPM 250 manufactured by Gaskuro Factory, the oxygen permeability coefficient of the bottle was measured at 23 ° C and atmospheric pressure. In order to compare the measured values of various containers, divide by the surface area of each container, and then multiply by the average value of the wall thickness of each container to obtain the oxygen permeability coefficient (unit: cm ³ mm / m ² 24h atm ).

○ Water vapor permeability test of bottles Bottles with calcium chloride sealed and sealed were left in a room at 40 ° C and 90% relative humidity. The weight of the container was measured every other day to determine the weight increase per day. In order to compare the measured values of various containers, the surface area value of each container was divided, and the value obtained by multiplying the average value of the wall thickness of each container was defined as the water vapor permeability (unit: gmm / m ² 24h).

 〇Cellotape surface peeling test: Nichiban Co., Ltd. cellophane tape (width 18 mm) 20 cm was attached to the top and bottom of the container left overnight at 20 ° C. and relative humidity 65% so that air bubbles would not be trapped, and the tape was sharpened from the top. The extent of peeling was evaluated by the area ratio of the surface of the container that was peeled off and peeled off 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 copolymer containing ethylene and glycidyl ester of α, β-unsaturated carboxylic acid as essential components The thermoplastic resin composition containing the combination (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 low oxygen permeability and water vapor permeability, and have a better balance of barrier properties than films made of polyethylene terephthalate or high density polyethylene (Comparative Example 1 or 2). It is a film. Further, even a film made of a resin composition having a low proportion of polyethylene (Comparative Example 3) has insufficient steam 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 not possible.

 Examples 7 to 12, Comparative Examples 5 to 7 Polyester resin (A), polyethylene (B), glycidyl group-containing copolymer containing ethylene and glycidyl ester of α, β-unsaturated carboxylic acid as essential constituents The thermoplastic resin composition containing the combination (C) in the proportion shown in Table 1 was subjected to extrusion blow molding. A flat bottle with a capacity of 600 ml, a body width of 96 mm, a body depth of 52 mm, a height of 235 mm, and a mouth diameter of 27 mm was molded. Ta-70, Ltd. Bu-7054M-P molding machine was used with a 70φ extrusion screw at a melting temperature of 280 ° C and a mold temperature of 20-40 ° C.

 The test results of these containers are shown in Table 3.

 As a comparative example, a bottle made of polyethylene or a resin composition containing no glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of α, β-unsaturated carboxylic acid as essential components was 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 glycidyl ester of α, β-unsaturated carboxylic acid were essential constituents. The bottles (Comparative Examples 5 and 6) made of a resin composition containing no glycidyl group-containing copolymer (C) as a component were extremely weak and could not be practically used. Further, the polyethylene bottle (Comparative Example 7) showed a large oxygen permeability. In addition, regarding the appearance of the container, a weak pearly luster was seen in the examples and the comparative examples 5 and 6.

 Examples 13 to 18 and Comparative Examples 8 to 11 Polyester resin (A), polyethylene (B), glycidyl group-containing copolymer containing ethylene and glycidyl ester of α, β-unsaturated carboxylic acid as essential components The thermoplastic resin composition in which the united product (C) was mixed 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 an outer diameter of 27 mm, a length of 115 mm, and a wall thickness of 3 mm. The preform was molded. Subsequently, the preform was stretched axially with a stretching rod at 100 ° C, and at the same time, 5 to 15 atm of compressed air was blown into the preform to perform biaxial stretch blow molding. A cylindrical bottle with a capacity of 600 ml, a body diameter of 62 mm, a height of 220 mm and a mouth diameter of 27 mm was formed. An injection blow molding machine manufactured by Nisshin AB Machinery Co., Ltd. was used as the 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 α, β-unsaturated carboxylic acid as an essential component, polyethylene terephthalate alone or Table 4 also shows the results of testing by molding a bottle made of a resin composition having a low proportion of polyethylene.

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 bottle comprising a resin composition containing only 0.5 part by weight of a glycidyl group-containing copolymer (C) containing ethylene and a glycidyl ester of α, β-unsaturated carboxylic acid as essential components (Comparative Example 8 , 9) was extremely 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 containing a small amount of polyethylene (Comparative Example 11) had a large water vapor permeability, was translucent in appearance, and was milky white, which was not preferable.

Claims (4)

[Claims] 1. An ethylene and an α, β-unsaturated carboxylic acid based on 100 parts by weight of a resin composition consisting of 10 to 90% by weight of a polyester resin (A) and 90 to 10% by weight of a polyethylene (B). A thermoplastic resin encapsulating material comprising a resin composition containing 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) having the glycidyl ester as an essential component. 2. Ethylene and α, β-unsaturated carboxylic acid based on 100 parts by weight of a resin composition consisting of 10 to 90% by weight of polyester resin (A) and 90 to 10% by weight of polyethylene (B). A thermoplastic resin container comprising a resin composition containing 1 to 30 parts by weight of a glycidyl group-containing copolymer (C), which is an essential constituent component of the glycidyl ester. 3. Ethylene and α, β-unsaturated carboxylic acid based on 100 parts by weight of a resin composition consisting of 50 to 90% by weight of polyester resin (A) and 50 to 10% by weight of polyethylene (B). A thermoplastic resin packaging material, comprising a stretched resin composition containing 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) containing the glycidyl ester as an essential component. 4. Ethylene and α, β-unsaturated carboxylic acid based on 100 parts by weight of a resin composition consisting of 50 to 90% by weight of polyester resin (A) and 50 to 10% by weight of polyethylene (B). A glycidyl ester of 1 to 30 parts by weight of a glycidyl group-containing copolymer (C) as an essential constituent and a resin composition molded by a stretch blow molding method. container.