JP2915324B2 - Saponified ethylene-vinyl acetate copolymer resin composition and multilayer structure using 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 saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) resin composition and a multilayer structure using the same, and more particularly to a thermoplastic resin such as polypropylene. The present invention relates to an EVOH resin composition having excellent stretchability and gas barrier properties when used for lamination with a resin, and a multilayer structure using the same.

[0002]

2. Description of the Related Art In general, EVOH is excellent in transparency, antistatic property, oil resistance, solvent resistance, gas barrier property, fragrance retention property, etc., but on the other hand, it is inferior in impact resistance to other properties. It is used by laminating with a thermoplastic resin. However, when the multilayer structure is stretched, the EVOH layer breaks, pinholes, cracks, and the like at the time of stretching. As a result, the appearance, transparency, and gas barrier properties are deteriorated. Therefore, in order to improve the stretchability, E
Addition of various plasticizers to VOH (JP-A-53-88067, JP-A-59-20345) and blends of polyamide resins (JP-A-52-141785, JP-A-58-36412) ) Has been proposed.

On the other hand, two or more different EVOHs
, For example, EVOH having an ethylene content of 45 to 60 mol% and an ethylene content of 25 to
Blend with 40 mol% of EVOH (JP-A-63-2
No. 64656), EVO having a degree of saponification of 96 mol% or more.
A blend of H and EVOH having a degree of saponification of less than 96 mol% (JP-A-63-230575) has also been proposed. Furthermore, Japanese Patent Application Laid-Open No. 7-40516 describes that a specific EVOH defined based on a differential calorimeter measurement is excellent in heat stretch moldability.

[0004]

However, in the techniques disclosed in JP-A-53-88067 and JP-A-59-20345, it is necessary to add a large amount of a plasticizer in order to sufficiently improve the stretching properties. Yes, this greatly reduces gas barrier properties. The techniques disclosed in JP-A-52-141785 and JP-A-58-36412 are not preferable because long-run processability remains a problem, a large number of gels are generated in a molded product, and coloring occurs. Also, in the technology disclosed in JP-A-63-264656, a blend of EVOHs having greatly different ethylene contents has poor transparency and gas barrier properties.
No. 30757 discloses an EV having a low saponification degree.
Since OH is used, thermal stability is deteriorated and gel is generated.

Further, in the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-40516, at the time of stretching, the temperature is first raised to a temperature higher by 10 to 30 ° C. than the stretching temperature, and then the film is radiated to the stretching temperature and stretched. Although stretchability (voids, cracks, unevenness) is improved, the stretchability is a stretch ratio enough to be used for container production according to the publication example, and is 20 times in area ratio. It is still unsatisfactory for applications requiring high stretching as described above, for example, for stretch barrier film applications, and there is room for improvement in further stretchability. Therefore, when used for lamination with a thermoplastic resin such as polypropylene, it does not impair the excellent gas barrier properties of EVOH, has excellent transparency, and has excellent stretchability without breaking, pinholes, cracks, and uneven stretching. Development of a good EVOH resin composition is desired.

[0006]

Means for Solving the Problems However, as a result of intensive studies to solve such problems, the present inventors have found that the total area (in the melting curve showing the endothermic peak measured by the differential scanning calorimeter) Total heat) is 45 J / g or more and 1
50 ° C. or more areas (heat) is Ri Der below 55 J / g, or
, Boron compounds, copper compounds, aluminum compounds,
At least one selected from tan compounds and zirconium compounds
An EVOH resin composition containing one compound ,
The inventors have found that such a problem is solved, and have completed the present invention. In addition, about the measurement with a differential scanning calorimeter, 10 degreeC /
After raising the temperature to 230 ° C. in 3 min.
The temperature is lowered to 0 ° C., and a melting curve showing an endothermic peak when the temperature is raised again at 10 ° C./min is obtained, and the total area and the area of 150 ° C. or more are measured.

Referring to FIG. 1 in more detail, FIG.
Is a melting curve of a typical example of the EVOH resin composition of the present invention (it is not limited to this), a point at which the peak of the melting curve starts to rise is a, an end point of the peak is b, and 15
Assuming that a point intersecting the curves a and b is d and a point intersecting the straight line ab is d when a straight line is drawn on 0 ° C., the total area referred to in the present invention is the curves a to c and b and the straight line a The area surrounded by −db is (S ₁ + S ₂ ), and the area of 150 ° C. or more is the area (S ₂ ) surrounded by the curves c to b, the straight line bd, and the straight line cd. That is, in the present invention, the area (S ₁ +
The heat quantity represented by S ₂ ) may be 45 J / g or more and the heat quantity represented by the area (S ₂ ) may be 55 J / g or less.

Hereinafter, the present invention will be described in detail. The EVOH of the present invention has a total area (total calorific value) of at least 45 J / g, preferably at least 50 J / g, more preferably at least 53 in a melting curve showing an endothermic peak measured by a differential scanning calorimeter as described above. ~ 80 J / g and 150
The area (heat amount) of not less than 55 ° C. is 55 J / g or less, preferably 5
It is sufficient if the EVOH is 0 J / g or less. In such a melting curve, if the total area (total heat) is less than 45 J / g, the oxygen barrier property becomes poor, and the area (heat) at 150 ° C. or more exceeds 55 J / g. And the stretchability becomes insufficient, and the effect of the present invention is not exhibited.

The method for obtaining the above specific EVOH resin composition is not particularly limited, and a high melting point plasticizer such as a polyalcohol having an alkyl chain having 2 to 20 carbon atoms is added to EVOH in an amount of 100 parts by weight of EVOH. 1 for
A method of adding 10 to 10 parts by weight, preferably 2 to 5 parts by weight,
A specific functional group such as a monocarboxylic acid compound, an epoxy compound and an amino compound is added to
Mol%, preferably 0.5 to 5 mol%, or a method of blending two or more EVOHs having different ethylene contents. Among them, the most simple method for obtaining the above-mentioned specific EVOH resin composition is a method of blending two or more EVOHs having different ethylene contents, and the method will be described in detail below.

The EVOH used is not particularly limited, but has an ethylene content of 20 to 60 mol%, preferably 25 to 50 mol%, more preferably 27 to 45 mol%.
It is desirable that the saponification degree is 96 mol% or more in mol%. If the ethylene content is less than 20 mol%, the gas barrier properties and melt moldability at high humidity are reduced, and if it exceeds 60 mol%, sufficient gas barrier properties cannot be obtained. On the other hand, when the saponification degree is less than 96 mol%, the gas barrier properties, thermal stability and moisture resistance are reduced.

The EVOH is obtained by saponifying an ethylene-vinyl acetate copolymer. The ethylene-vinyl acetate copolymer can be produced by any known polymerization method, for example, suspension polymerization,
It is produced by emulsion polymerization, solution polymerization, or the like, and saponification of an ethylene-vinyl acetate copolymer can be performed by a known method. The EVOH is an α-olefin in a small amount,
It may be "copolymerized and modified" with other comonomers such as unsaturated carboxylic acid compounds, unsaturated sulfonic acid compounds, (meth) acrylonitrile, (meth) acrylamide, vinyl ether, vinyl chloride, and styrene.
Also, "post-modified" such as urethanization, acetalization, and cyanoethylation may be used as long as the gist of the present invention is not impaired.

In the present invention, two or more EVOHs arbitrarily selected from such EVOHs may be blended. In particular, it is preferable to use two or more EVOHs having different ethylene contents. In this blend, the difference in ethylene content between the most blended EVOH (A) and the next most blended EVOH (B) is 3 to 20.
Mol%, preferably 3 to 15 mol%, more preferably 5 mol%.
Preferably, it is 15 mol%. If the difference in the ethylene content is less than 3 mol%, the effect of the present invention is not exhibited, and if it exceeds 20 mol%, the transparency becomes poor and the film-forming stability deteriorates, which is not practically preferable. In addition, the difference in ethylene content means that the ethylene content of EVOH (A) is (a),
Assuming that the ethylene content of EVOH (B) is (b), |
(A)-(b) |

The amount of each EVOH to be blended is appropriately selected depending on the type of EVOH to be blended and the like. The blending method is not particularly limited, and a method of dissolving each EVOH in a water-alcohol solvent and mixing the same, and a method of dissolving an ethylene-vinyl acetate copolymer before saponification of each EVOH in an alcohol solvent such as methanol. A method of mixing and saponifying in a mixed state, or a method of melt-mixing each EVOH can be mentioned, but a method of melt-mixing is usually employed.

For example, each EVOH is dry-blended and then melted and blended. Each EVOH is blended in a molten state.
A method in which another EVOH is added to H in a dry state may be used. Above all, a method in which each EVOH is dry-blended and then melted and blended is practical in terms of simplicity of the apparatus, cost of the blended product, and the like.

Thus, according to the above manufacturing method, in the melting curve showing the endothermic peak measured by the differential scanning calorimeter, the total area (total calorific value) is 45 J / g or more and 15
EVO having an area (calorific value) of 0 ° C. or more of 55 J / g or less
H resin composition is obtained.
When the resin composition is prepared, the effects of the present invention are exhibited for the first time. In the present invention, films and sheets having excellent stretchability and gas barrier properties can be obtained by using the EVOH resin composition. In particular, the EVOH resin composition further includes a boron compound, a copper compound, and an aluminum compound. By containing at least one compound selected from the group consisting of a compound, a titanium compound and a zirconium compound, the stretchability is further improved, the thickness accuracy at the time of film formation is improved, no streaks are generated, and there is no stretching unevenness during stretching. A film is obtained.

Among the boron compounds, copper compounds, aluminum compounds, titanium compounds, and zirconium compounds, when used as food packaging materials, boron compounds are preferably employed because of their low toxicity. Examples of the boron compounds include boric acid and boric acid. Acid salts, borate esters, borax, boron halides, trialkylborons, triarylborons and the like. The method for incorporating the boron compound or the like into the EVOH resin composition is not particularly limited, but may be added at the same time as EVOH is blended, may be contained in at least one kind of EVOH in advance, or may be contained after blending. Alternatively, the boron compound may be dissolved in a solvent such as water and mixed with EVOH, or EVOH may be immersed in a boron compound solution. The content of such a boron compound is 0.01 to 5% by weight, preferably 0.01 to 1% by weight, more preferably 0.01 to 0.5% by weight, based on the total weight of EVOH in terms of boron. If less than 0.01% by weight, the effect of containing a boron compound cannot be obtained, while 5% by weight
Exceeding the ratio is undesirable because the boron compound is localized or a gel is generated.

Further, in the present invention, if necessary, a plasticizer,
Additives such as heat stabilizers, ultraviolet absorbers, antioxidants, colorants, fillers, and other resins can also be used.
In particular, a hydrotalcite-based compound, a hindered phenol-based, a hindered amine-based heat stabilizer, and a metal salt of a higher aliphatic carboxylic acid can also be added as a gel generation inhibitor.

The thus obtained EVOH resin composition of the present invention is frequently used for molded articles, and is formed into pellets, films, sheets, containers, fibers, rods, tubes, various molded articles and the like by melt-kneading. These pulverized products (for example, when the recovered products are reused) and pellets are often used for melt molding again. As the melt molding method, an extrusion molding method (T-
Die extrusion, inflation extrusion, blow molding, melt spinning, profile extrusion, etc.) and injection molding are mainly employed.
The melt molding temperature is often selected from the range of 200 to 250 ° C.

The EVOH resin composition obtained according to the present invention comprises:
It can be used for a molded product as described above.
It is preferably used as a multilayer structure obtained by laminating a thermoplastic resin layer on at least one side of a layer made of the OH resin composition, and a multilayer structure suitable for practical use is obtained. Since the multi-layer structure uses the EVOH resin composition of the present invention, the multi-layer structure exhibits a very excellent effect not only in gas barrier properties and transparency but also in stretchability at the time of high stretching.

In producing the multilayer structure, another substrate is laminated on one or both sides of the layer of the resin composition obtained according to the present invention. Method of melt-extruding a thermoplastic resin on a film or sheet of the above, method of melt-extruding the resin composition on a substrate such as a thermoplastic resin, and method of co-extrusion of the resin composition with another thermoplastic resin And a method of laminating a film or sheet of the resin composition obtained in the present invention with a film or sheet of another substrate using a known adhesive such as an organic titanium compound, an isocyanate compound, or a polyester compound. Is mentioned.

In the case of coextrusion, the mating resin may be a linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene - acrylic ester copolymers, polypropylene, propylene -α- olefin (having 4 to 20 carbon atoms
Α-olefins) copolymers, polyolefins such as polybutenes and polypentenes, or polyolefins in a broad sense, such as homo- or copolymers of these olefins, or graft-modified homo- or copolymers of these olefins with unsaturated carboxylic acids or esters thereof Resin, polyester, polyamide, copolymerized polyamide, polyvinyl chloride, polyvinylidene chloride, acrylic resin, styrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, chlorinated polyethylene, chlorinated polypropylene and the like. Saponified ethylene-vinyl acetate copolymer can also be coextruded. Among the above, polypropylene, polyamide, and polyethylene are preferably used in view of easiness of coextrusion film formation and practicality of film physical properties (particularly strength).

Further, a molded product such as a film or a sheet is once obtained from the resin composition obtained by the present invention, and another substrate is extrusion-coated thereon, or the film or sheet of another substrate is bonded to an adhesive. In the case of laminating using, any substrate (paper, metal foil, uniaxially or biaxially stretched plastic film or sheet, woven fabric, nonwoven fabric, metal flocculent, woody, etc.) other than the above-mentioned thermoplastic resin can be used. is there. The layer structure of the multilayer structure is such that the layer of the resin composition obtained in the present invention is a (a ₁ , a ₂ ,
...), Another base material, for example, a thermoplastic resin layer b
(B ₁ , b ₂ , ...), a film, a sheet,
In the case of a bottle, not only a two-layer structure of a / b but also b /
a / b, a / b / a, a 1 / a 2 / b, a / b 1 / b 2, b
Any combination such as ₂ / b ₁ / a / b ₁ / b ₂ is possible. In the filament form, a and b are bimetal type, core (a) -sheath (b) type, and core (b) -sheath (a). ) Type or eccentric core-sheath type.

In the case of co-extrusion, a may be blended with b and b may be blended with a, or at least one of a and b may be blended with a resin which improves the adhesion between the two layers. In the present invention, the multilayer structure is used as it is in various shapes, but it is preferable to further perform a stretching treatment in order to further improve the physical properties of the multilayer structure. Even in stretching of 20 times or more, breakage, pinhole,
The structure is excellent in stretchability without cracks and the like, and also has excellent effects on gas barrier properties and transparency.

The stretching may be either uniaxial stretching or biaxial stretching, and it is better to perform stretching at the highest possible magnification. In the case of uniaxial stretching, it is 5 times or more, especially 10 times or more, and in the case of biaxial stretching, the area magnification is 5 times.
It is preferable to be at least 20 times, particularly at least 10 times, in terms of physical properties, but in the present invention, the area magnification can be at least 20 times, particularly 24 to 50 times as described above. A stretched film, stretched sheet, or the like free of holes, cracks, stretching unevenness, and the like is obtained.

The stretching method includes a roll stretching method, a tenter stretching method, a tubular stretching method, a stretching blow method, and the like.
Of the deep drawing, vacuum forming and the like, those having a high stretching ratio can be employed. In the case of biaxial stretching, any of a simultaneous biaxial stretching method and a sequential biaxial stretching method can be adopted. Stretching temperature is 80
To 170 ° C, preferably about 100 to 160 ° C.

In the present invention, the EVOH of the present invention
Resin composition, that is, the amount of heat absorbed in the melting of EVOH by using a specific EVOH resin composition,
This is the first time that a multilayer structure can be stretched at a high magnification. After completion of the stretching, heat setting is performed.
The heat setting can be performed by a well-known means, and heat treatment is performed at 80 to 170 ° C., preferably 100 to 160 ° C. for about 2 to 600 seconds while keeping the stretched film in a tensioned state.
In addition, the obtained stretched film should be subjected to cooling, rolling, printing, dry laminating, solution or melt coating, bag making, deep forming, box processing, tube processing, split processing, etc. as necessary. Can be.

The shape of the multilayer structure thus obtained may be arbitrary, and examples thereof include a film, a sheet, a tape, a bottle, a pipe, a filament, and an extrudate having a modified cross section. In addition, the obtained multilayer structure is required,
Heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making processing, deep staking processing, box processing, tube processing, split processing, and the like can be performed. The films, sheets, containers and the like obtained as described above are useful as various packaging materials for foods, pharmaceuticals, industrial chemicals, agricultural chemicals and the like.

[0028]

[Action] EVOH resin composition of the present invention shows a specific melting curve measured by differential scanning calorimetry, further boron compound
Material, copper compound, aluminum compound, titanium compound, di
At least one compound selected from ruconium compounds
Because of containing , gas barrier properties, transparency, of course, when subjected to lamination with a thermoplastic resin such as polypropylene, excellent in stretchability without breaking, pinholes, cracks, stretch unevenness and the like Films and sheets can be obtained.

[0029]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” are based on weight unless otherwise specified. Example 1 Production of EVOH Resin Composition EVOH (A) having an ethylene content of 45 mol% and a saponification degree of 97.0 mol%, and an EVOH (B) having an ethylene content of 30 mol% and a saponification degree of 99.5 mol% ) Is 6
The mixture was fed to a single screw extruder at 0:40, melt-mixed at 220 ° C., and pelletized. The pellets were put into a 1% boric acid aqueous solution, and stirred at 80 ° C. for 12 hours.
After washing with pure water at 15 ° C. and drying at 110 ° C. for 8 hours,
An EVOH resin composition of the present invention was obtained. The total area (total heat) of the melting curve of the EVOH resin composition showing the endothermic peak measured by the differential scanning calorimeter was 53 J / g, and the area (heat) at 150 ° C. or higher was 35 J / g. Was. The differential scanning calorimeter is DSC7 manufactured by PerkinElmer.
Was used.

Production of Multilayer Structure Using the above EVOH resin composition, feed block 5 was prepared.
By layer T die, polypropylene layer / adhesive resin layer / EV
Films were formed so as to have a layer structure of an OH resin composition layer / adhesive resin layer / polypropylene layer to prepare a multilayer laminated film. The structure of the film is such that both outer polypropylene layers (polypropylene MI is 1.2 g / 10 min) are 100 μm,
The adhesive resin layer (the adhesive resin is a maleic anhydride-modified polypropylene, and its MI is 2.6 g / 10 min) is 25 μm,
The thickness of the EVOH resin composition layer of the intermediate layer is 50 μm. About such a multilayer structure, stretchability, stretch unevenness, oxygen permeability,
Transparency was evaluated as follows.

(Stretchability) The above multilayer structure is 8 cm × 8 c
m, preheat the sample at 150 ° C. for 1 minute, and stretch at 4 mm in the longitudinal direction at a stretching speed of 100 mm / sec.
The film was successively biaxially stretched in the order of 1 × and 6 times in the lateral direction (stretching ratio: 24 ×), and the appearance of the obtained stretched film was evaluated according to the following criteria.・ ・ ・: A smooth film is obtained even after stretching. X: After stretching, the film is whitened or fibrilized.

(Stretch Unevenness) The appearance change of the stretched film obtained in the same manner as above was evaluated according to the following criteria.・ ・ ・: No streak occurred. Δ: One or two lines were generated. ×: Three or more streaks occurred.

(Oxygen Permeability) The oxygen permeability of the stretched film obtained in the same manner as above was measured using MODERN-CONT.
20 using OX-TRAN10-50 of OROL
° C, 65% RH (cc / m ² · da
y · atm). (Transparency) Reflection transmittance meter RM manufactured by Murakami Color Research Laboratory
Using -15A, the haze value of the stretched film obtained in the same manner as above was measured.

Examples 2 and 3 , Comparative Examples 1 to 5 EVOH shown in Table 1 was used and EVOH was used.
A resin composition was obtained. With respect to the EVOH resin composition, a multilayer structure was prepared in the same manner as in Example 1, and each physical property was evaluated. Note that in Example 3, EVOH (A) and EOH (A) were used.
Et: 4 as EVOH (C) in addition to VOH (B)
5 mol%, Sv: 97.0 mol%, using A / B
Three types of EVOH were mixed so that / C = 40/30/30. Table 2 shows the evaluation results of the examples and the comparative examples.
Shown in

[0035]

Table 1 EVOH (A) EVOH (B) Boron content Compounding ratio Et Sv Et Sv (%) A / B Example 1 45 97.0 30 99.5 0.02 60/40 〃 2 40 99.5 45 97.0 0.03 70/30 ３3 30 99.5 40 98.5 0.03 40/30 Comparative Example 1 40 99.5 − − 0.02 − 〃 2 45 97.0 − − 0.02 − ３ 3 30 99.5 50 99.5 0.02 85/15 ４ 4 32 99.5 44 99.5 0 50/50 〃 5 40 99.5 45 97.0 0.03 90/10

Note) Et: ethylene content (mol%) Sv: saponification degree (mol%) The boron content was determined by an atomic absorption method.

[0037]

[Table 2] Stretchability of total area of 150 ° C or more Stretching unevenness Oxygen permeability Transparency (total calorific value) Area (calorific value) (cc / m ² · day · atm) (J / g) (J / g) Example 1 5335 ○ ○ 23 2.1 〃 26 648 ○ ○ 10 1.9 〃 35 940 ○ ○ 18 1.9 Comparative Example 17 163 ×-over 31.5 〃 236 14 ○ ○ 75 2.1 37766 ×-over 42.3 〃 47769 ×-over 35.4 ５ 57 266 ×-over 32.5 Note)-: The number of streaks is measured because the film whitened and fibrillated. I couldn't do that. over: Oxygen permeability could not be measured because it exceeded the measurable range of the measuring device.

[0038]

EVOH resin composition of the present invention exhibits, shows a specific melting curve measured by differential scanning calorimetry, further boric
Elemental compounds, copper compounds, aluminum compounds, titanium compounds
Product, at least one selected from zirconium compounds
Since it contains a compound, it has excellent gas barrier properties and transparency, as well as excellent stretchability without breakage, pinholes, cracks, uneven stretch, etc. when used for lamination with a thermoplastic resin such as polypropylene. Effect.

[Brief description of the drawings]

FIG. 1 is a melting curve of a saponified ethylene-vinyl acetate copolymer resin composition of the present invention measured by a differential scanning calorimeter.

[Explanation of symbols]

a: the point at which the peak of the melting curve starts to rise b: the end point of the peak of the melting curve c: the point at which a straight line is drawn at 150 ° C., which intersects with the curves a and b d: the line is drawn at 150 ° C. S ₁ : Area surrounded by curves a to c, straight lines ad and cd, and S ₂ : surrounded by curves c and b, straight lines bd and cd. area

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C08L 23/00-23/36 B32B 27/28

Claims (6)

(57) [Claims] 1. In a melting curve showing an endothermic peak measured by a differential scanning calorimeter, the total area (total calorific value) is 45%.
J / g or more, the area (caloric value) of 150 ° C. or more is 55 J /
g, and at least one compound selected from a boron compound, a copper compound, an aluminum compound, a titanium compound, and a zirconium compound, wherein the saponified ethylene-vinyl acetate copolymer composition comprises: . 2. The saponified ethylene-vinyl acetate copolymer resin according to claim 1, wherein two or more saponified ethylene-vinyl acetate copolymers having different ethylene contents are blended. Composition. 3. The difference in ethylene content between the saponified ethylene-vinyl acetate copolymer (A) having the largest blending amount and the saponified ethylene-vinyl acetate copolymer (B) having the second largest blending amount. 3 to 20 mol% of the saponified ethylene-vinyl acetate copolymer resin composition according to claim 2. 4. The ethylene according to claim 1, wherein
A multilayer structure comprising a layer made of a saponified vinyl acetate resin composition and a thermoplastic resin layer laminated on at least one surface of the layer. 5. The multilayer structure according to claim 4, wherein the multilayer structure is stretched in at least one direction. 6. The multilayer structure according to claim 4, wherein the thermoplastic resin is a polyolefin resin.