JPH0315541A - Multilayer structure - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] A. Industrial Application Field The present invention is directed to an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) which is free from bottle holes, cracks, local thickness unevenness, etc. during heating stretching, particularly during heating high-speed stretching operations, and has excellent gas barrier properties. ) multilayer structure using composite material,
In particular, it relates to heated stretching, and more particularly to heated high-speed stretched multilayer structures.

B. Conventional technology EVOH is currently used in the field of packaging films for food products, especially food products that require barrier properties against oxygen, odors, flavors, etc., and other products that require aroma retention properties. Recognized as effective. EVOH is made by laminating a silent plastic resin layer such as polyethylene, polypropylene, polystyrene, polyester, polyamide, polyvinyl chloride, etc., and various adhesive resin layers represented by ionomer, ethylene-vinyl acetate copolymer, etc. Used in the form of multilayer structures.

When laminating EVOH and polyester, E
During stretch molding at a temperature below the melting point of VOH, polyester has a higher stretching tension than EVOH, so EV
The OH layer is stretched uniformly under the influence of the PET layer, without any voids, cracks or local deflections. However, EVO
When laminating H and polystyrene, etc., polystyrene becomes EV when stretched at a temperature below the melting point of EVOH.
Since the stretching tension is lower than that of OH, the EVOH layer is not affected much by the polystyrene layer. Therefore, when performing secondary processing (stretching processing) of multilayer structures (films, sheets, parisons, etc.) into containers etc. Small poids, cracks, and local uneven thickness occur frequently in the EVOH layer, and as a result,
The oxygen barrier properties of the container will deteriorate significantly. In addition, the appearance of the container is poor and it cannot be used as a container for food or the like.

Therefore, in order to prevent pinholes, cracks, etc. in the EVOH layer that occur during heating and stretching, various plasticizers have been added to the EVOH layer (JP-A-53-88067, JP-A-5
9-20345), blends of polyamide resins (JP-A-52-141785, JP-A-58-36412)
Although these methods have been considered, it has been found that none of them are fully satisfactory in terms of the following points. That is,
In the addition system of various plasticizers, in order to sufficiently improve heat stretchability, it is necessary to add 10 to 20 parts by weight of plasticizer per 100 parts by weight of E V O H. There are many problems such as a large decrease in width and a decrease in interlayer adhesive strength with the EVOH layer, making it unusable.

On the other hand, in the case of a polyamide-based resin-added system, it is not durable for general use, perhaps because of its high chemical reactivity with EVOH, the presence of a large number of gel-like substances in the molded product, and significant coloration. In addition, in the case of polyamide-based resin additive systems with relatively little gel coloring, a seemingly good container can be obtained, perhaps because the compatibility between EVOH and polyamide is not sufficient, but especially when forming by heating and high-speed stretching, slight Possibly due to the presence of holes, the measured values of gas barrier properties vary widely, making it unreliable as a gas barrier container.
It cannot withstand use.

Therefore, it has high gas barrier properties and good reliability (variation) as a gas barrier container, that is,
During heating and high-speed stretching or shaping, minute pinholes may appear in the EVOH layer.
One of the important issues is the development of EVOH that does not cause cracks or deflections.

Furthermore, the special polyester used in this development is described in JP-A-58-167617, but it is possible to blend it with EVOH and to make it into a gas barrier material by heating and high-speed stretching or shaping. There is no mention of any technical idea behind the effect of improving the reliability of the data.

Furthermore, JP-A No. 61-211033 describes that a special polyester used in the present invention is blended with EVOH and laminated directly onto a polyester layer, and that a strong interlayer bond is obtained by doing so. .

However, in this publication, the object of the present invention is
Not only is there no description of improving the stretchability and heat-formability of the EVOH multilayer structure, nor the associated improvement in the reliability of the gas barrier properties, but there is also no idea. The reason for this is that, as described in the publication, a laminate of polyester and EVOH is generally stretched at 80 to 120°C.
This is because it is easy to heat form, so there is no need to particularly improve EVOH in order to improve stretchability and heat formability. Therefore, the EVOHI1 material of the invention is polystyrene,
It was completely unexpected that it was found that the stretchability and aging formability of multilayer bodies with polypropylene and the like can be improved, and the reliability of barrier properties can be improved.

C. Problems to be Solved by the Invention The present invention aims to eliminate cracks, pinholes, and local deviations in the EVOH layer that occur when secondary processing an EVOH multilayer laminate into containers, etc., without impairing the excellent gas barrier properties of EVOH. Prevents the generation of meat, etc., has high gas barrier properties,
The present invention also provides a multilayer structure having highly reliable gas barrier properties.

D. Means for solving the problem
The dicarboxylic acid component is 50 mol% or more of isophthalic acid based on the total dicarboxylic acid component, and the diol content is 0.1 to 30 mol% of 1.3-bis(β-hydroxyethoxy) based on the total diol component. ) A composition (C) consisting of a thermoplastic polyester (B) containing benzene and/or diethylene glycol, in particular (B)
As 120'c! The dynamic viscoelastic coefficient E″ is 10
This problem can be solved by laminating a composite (C) layer obtained using a thermoplastic polyester having a density of 9 dyne/cm2 or less with a thermoplastic resin (D) layer that satisfies the following formula.

110℃≧XA ≧O0C...
(I) Stock XA indicates the melting point of A, and XD indicates the melting point of D or the softening point if there is no melting point.

Here, the melting point refers to the temperature at which an endothermic peak occurs when the temperature is raised at IQ'o/min in a nitrogen (N2) atmosphere using a DSC measuring device (manufactured by Mettler). If there are two or more endothermic peaks, refer to the peak temperature on the maximum endothermic side.

Softening point refers to the softening temperature measured under a load of 1 kg using a Toyo Seiki HDT tester when no melting peak is shown by DSC.

The present inventors produced various multilayer sheets made by blending various plasticizers, polymers, etc. with EVOH and disposing adhesive resins and thermoplastic resins, and obtained cups and bottles by reheating and stretching operations. The appearance and gas barrier properties of the container were measured. As a result, the composition (C) layer and (1)
When thermoplastic resin (D) layers satisfying the formula are laminated and then heated and stretched, a good molded article without cracks, pinholes, local thickness unevenness, etc. in the EVOH composition layer can be obtained. I found out. In particular, the thermoplastic resin (D) can be used at low temperatures (110°C - 140°C) in composite multilayer sheets with resins such as polystyrene that have low heating stretching temperatures.
Possibly due to minute cracks and pinholes occurring in the EVOHm layer during stretching or high-speed heating and stretching, the gas barrier measurement values vary widely, reducing the reliability of the container as a high gas barrier container. There were cases where there was a problem. Therefore, as a result of further intensive study, the present inventors surprisingly found that the above thermoplastic polyester (B), especially the thermoplastic polyester resin blended with E V O H (A), The viscoelastic coefficient E' is lO'dyne/cm2
When the following thermoplastic polyester resin (B) is used, the above problems are greatly improved, and not only is the shapeability good, but there is almost no deterioration of the gas barrier properties, and further,
It was discovered that a highly reliable container with high gas barrier properties with little variation in measured gas barrier values could be obtained, and the present invention was completed.

In the present invention, E V O H (A) is a saponified ethylene-vinyl acetate copolymer, with an ethylene content of 20 to 60 mol%, preferably 25 to 50 mol%, and a saponification degree of the vinyl acetate component of 90. % or more, preferably 95% or more can be used. If the ethylene content is less than 20 mol%, the melting properties will be poor, while if it exceeds 60 mol%, the gas barrier properties will be insufficient. Moreover, if the degree of saponification is less than 90%, gas barrier properties and thermal stability will deteriorate. The EVOH may also contain other comonomers [e.g., propylene, butylene, unsaturated carboxylic acid or its ester, (meth)acrylic acid, (meth)acrylic acid ester, etc.] to the extent that the object of the present invention is not impaired. (methyl, ethyl), etc.}, vinyl silane compounds (vinyltrimethoxysilane, triethoxysilane, etc.), vinylpyrrolidone (N-vinylpyrrolidone, etc.)], and also plasticizers, heat stabilizers, ultraviolet rays, etc. Absorbers, antioxidants, colorants, fillers, and other resins (polyamide, partially saponified ethylene-vinyl acetate copolymer, etc.) may also be blended freely. Further, a suitable melt index (M I ) (190'o, 21
60g load) is 0.1-50g/10min. ,
Optimally 0.5-20g/10min. It is.

In the present invention, the thermoplastic polyester (B) essentially contains 50 mol% or more of isophthalic acid based on the total dicarboxylic acid content as a dicarboxylic acid component, and examples of the dicarboxylic acid component that can be used in combination with isophthalic acid include:
Aromatic dicarboxylic acids such as terephthalic acid, orthofucuric acid, naphthalene dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl-4.4 dicarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid,
Examples include aliphatic dicarboxylic acids such as pimelic acid, corkic acid, azelaic acid, and sebacic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. One or more of these dicarboxylic acids can be used simultaneously, and the amount used is less than 50 mol%. Among these, terephthalic acid, nathalene dicarboxylic acid, diphenyl ether dicarboxylic acid, and the like are preferable in terms of heat shaping properties, gas barrier properties, and the like.

On the other hand, as a diol component, 0 for all diol components.
．． It is essential to contain 1 to 30 mol% of 1.3-(β-hydroxyethoxy)benzene and/or diethylene glycol, and the diol component that can be used in combination with 1.3-(β-hydroxyethoxy)benzene and diethylene glycol is , for example ethylene glycol, 1
．． 3-propanediol, l,4-butanediol, l
, 5-pentanediol, l,6-hexanediol,
Examples include aliphatic glycols such as 1,9-nonanediol and triethylene glycol, and alicyclic glycols such as cyclohexanediol and cyclohexanedimethanol. One or more of these diols can be used simultaneously. Among them, ethylene glycol, cyclohexanediol, and the like are preferable in terms of heat-shaping property, impact resistance, and the like.

As the dicarboxylic acid component of the thermoplastic polyester, isophthalic acid is essential in an amount of 50 mol% or more, preferably 50 to 95 mol%, based on the total dicarboxylic acid component. When the amount of isophthalic acid is less than 50 mol %, the effect of improving heat forming property is not sufficient and gas barrier properties are also poor. On the other hand, as a diol fraction, 1.3-
It is essential to contain (β-hydroxyethoxy)benzene and/or diethylene glycol alone or in total in an amount of 0.1 to 30 mol% based on the total diol content, more preferably 0.5 to 25 mol%. be. If it is 30 mol% or more, the effect of improving thermoformability will not be sufficient; on the other hand, if it is 0.
If it is less than 1 mol %, the gas barrier properties are unreliable, probably due to poor compatibility with EVOH.

In the present invention, the next desirable requirement is that the dynamic viscoelastic coefficient E' of the thermoplastic polyester resin (B) is 10 ta dyn.
e/cm2 or less, more preferably 5
x lO'dyne/cm2 or less. E' is IO
If it is larger than 'dyne/cm', there will be slight cracks and unevenness that tend to occur during heating and high-speed stretching operations, especially when stretching operations are carried out at relatively low temperatures (1lO to 140'o), and a decrease in the reliability of gas barrier properties. Abnormalities such as
In order to obtain the following thermoplastic polyester (B), the content ratio of 1.3-(β-hydroxyethoxy)benzene and diethylene glycol as diol components, especially 1.3
The ratio of the combination of (β-hydroxyethoxy)benzene and diethylene glycol is important. That is, from the viewpoint of gas barrier properties of the multilayer structure, the higher the content ratio of isophthalic acid is, the more preferable it is, but if it is too high, E″ will be 10
If it exceeds 9 dyne/Cm2, the reliability of heat forming property and gas barrier property may decrease. 1 as diol fraction. 3-(β-hydroxyethoxy)benzene, using diethylene glycol, especially 1
．． By setting the molar ratio of 3-(β-hydroxyethoxy)benzene/diethylene glycol to 1/99 to 80/20, preferably 2/98 to 50/50, a high isophthalic acid content and a high E' 10 9dyn
e/cm2 or less. the result,
It is possible to obtain a good multilayer structure that has high gas barrier properties and is free from deterioration in reliability of gas barrier properties, which is presumed to be caused by minute cranks and unevenness during heating and high-speed stretching operations.

Note that the dynamic viscoelastic coefficient E' refers to Rheovibron (DD V-n) manufactured by Orientik Co., Ltd. using a 20 to 500 μm single layer sheet of the thermoplastic polyester resin (B).
E P ) type measuring device (frequency 110Hz, temperature 1
20'o).

Furthermore, since the molecular weight of the thermoplastic polyester (B) greatly affects the shape of the sheet or the physical properties of the container, the intrinsic viscosity of the thermoplastic polyester (B) is 0.60 dQ/g or more, preferably 0.70 dQ/g.
It is desirable that it be more than g. What is the intrinsic viscosity here?
This is a value measured at 30°C in a mixed solvent of 7 enol/tetrachloroethanone (l:1 weight ratio). Further, heat stabilizers, plasticizers, lubricants, colorants, ultraviolet absorbers, antistatic agents, etc. may be used in the thermoplastic polyester (B) within a range that does not impede the effects of the present invention.

In addition, the thermoplastic polyester (B) to EVOH (A)
) is added in an amount of 5 to 50% by weight, preferably 7 to 35% by weight based on the total amount of (A) and (B).

If the amount added is less than 5% by weight, the effect of improving appearance is not sufficient, and cracks and unevenness are likely to occur. On the other hand, 50% by weight
If it exceeds this, the gas barrier properties will be significantly reduced and it will not be possible to use it as a high gas barrier container.

E V O H (A) and the thermoplastic polyester (B
) are not particularly limited, but (A) and (B) may be dry blended and used as is, or more preferably, using a Banbury mixer, single screw or twin screw There are methods such as pelletizing using an extruder and drying. If the blend is non-uniform, or if gels or lumps are generated or mixed during the blend pelletizing operation, there is a high possibility that the EVOH composite layer will break, crack, or become uneven during heat-stretch forming. Therefore, during the blend pelletizing operation, it is desirable to use an extruder with a high degree of kneading, seal Hotsuparo with nitrogen, and extrude at a low temperature. In addition, when blending and pelletizing, other additives (plasticizers, heat stabilizers, ultraviolet absorbers, antioxidants, colorants, fillers, other resins, etc.) may be used within the range that does not impede the purpose of the present invention. You are free to do whatever you want. In particular, as a measure to prevent gel formation, hydrotalcite compounds,
Contains 0.01 to 1% by weight of one or more of a hindered phenol type heat stabilizer, a hindered amine type heat stabilizer, and a metal salt of a higher fat l5 16 group carboxylic acid (for example, calcium stearate, etc.).
It is suitable to add it.

Next, the composition (C) layer consisting of (A) and (B) thus obtained is laminated on the thermoplastic resin (D) layer,
Obtaining a multilayer structure, particularly a heat-stretched multilayer structure, will be explained. It is important that the thermoplastic resin (D) to be laminated on at least one side of the composition (C) layer of the present invention is a resin that satisfies the above-mentioned formula (I), and satisfies the following formula ('). Resins are suitable.

110゜C≧xA-XD≧10℃...- (
I') When xA - It is bad and cannot be used.

Furthermore, when xA-XD is below 0°C, EVOH generally softens and melts during heating, stretching or shaping, so stretching or shaping is possible, and the composition (C) used in the present invention is particularly difficult to use. In addition, as mentioned above, polyester has good co-stretching shapeability with EVOH even at temperatures below the melting point of EVOH, so the composition used in the present invention There is no reason to use (C) in particular.

Suitable materials for the thermoplastic resin (D) include polyolefin resins {polyethylene, polypropylene, ethylene-hinyl acetate copolymer, ethylene-(meth)acrylic acid ester (menal ester or ethyl ester) copolymer, etc.}, polystyrene resin (Boristyrene, styrene-butadiene copolymer, styrene-butadiene-acrylonitrile copolymer, impact-resistant styrenic resin, etc.)
, polyamide resin, polyvinyl chloride resin, polymethacrylic resin, etc. Among these, polyolefin resins (especially polypropylene) and polystyrene resins are particularly suitable.

These thermoplastic resins may be used alone or in combination of two or more. Furthermore, in the present invention, these thermoplastic resins are mixed with a small amount of thermoplastic resin that does not satisfy formula (I), for example, 50% by weight or less, particularly 40% by weight or less, and even 30% by weight or less. You can also do that. As such a mixture, scraps of the multilayer structure (film, sheet, parison container) of the present invention are preferably used.

In the present invention, in order to form a multilayer composition of composition (C) and thermoplastic resin (D), the adhesive resin used is E
It is not particularly limited as long as it firmly adheres the VOH composite layer and the thermoplastic resin layer, but unsaturated carboxylic acid or its anhydride (maleic anhydride, etc.) may be used in a polyolefin-based resin. Resin [polyethylene {low density polyethylene (LDPE), linear low density polyethylene (LLDP)
E), ultra-low density polyethylene (SLDPE), ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester (methyl ester or ethyl ester) copolymer] are preferably used.

As a method for obtaining a multilayer structure, the composition (C) and the thermoplastic resin (D) are often bonded via an adhesive resin by an extrusion lamination method, a dry lamination method, a coextrusion lamination method, or a coextrusion lamination method. A laminate (film, sheet, ballin) is obtained by a forming method, a coextrusion pipe shaping method, a co-injection molding method, a solution coating method, etc., and then the laminate is stretched under conditions satisfying the following formula (II). (Uniaxial or Biaxial Stretching) Examples include methods of heating and stretching by slicing, vacuum-pressure deep drawing, biaxial stretching blow shaping, and the like.

XA 10゜C≧Y≧XA-+10゜c ・-・
(n) (However, Y indicates the heating and stretching temperature (°C).) Furthermore, the thickness structure of the multilayer structure is not particularly limited, but when considering the formability and cost, The thickness ratio of the composition (C) layer to the total thickness is 2 to 2
Approximately 0% is suitable. In addition, the structure of the multilayer structure is as follows: Kumikaimono (C) layer/adhesive resin layer/thermoplastic resin (D
) layer, thermoplastic resin (D) layer/adhesive resin layer/Kumikaimono (
Typical examples include layer C)/adhesive resin layer/thermoplastic resin (D) layer. Thermoplastic resin (D) on both outer layers
A layered structure with layers is best, but in that case the resins of both outer layers may be 19 20 different or may be the same.

By the way, an interesting point of the present invention is that the coextruded multilayer sheet molded product has a thickness distribution not only in the MD direction (discharge direction) but also in the TD direction (direction perpendicular to the discharge direction) {thickness of the composition (C) layer distribution} is uniform. Therefore, the multilayer structure of the present invention has the advantage that not only the variation (R) of the gas barrier property in the MD (discharge direction) is small, but also that in the TD direction.

In the present invention, the multilayer structure obtained by heating and stretching refers to containers such as cups and bottles, sheets, and film-like objects obtained by heating and stretching, and heating refers to the multilayer structure obtained by heating and stretching. This refers to an operation in which the structure is left at the temperature required for heating and stretching for a predetermined period of time, and the multilayer structure becomes almost thermally uniform.Considering operability, various heaters are used to heat the structure and make it uniform. A method of doing so is preferred.

The heating operation may be performed simultaneously with the stretching or before the stretching. Stretching refers to the operation of uniformly shaping a thermally uniformly heated multilayer structure into a container, cup, bottle, or film using a chuck, grug, vacuum force, or pneumatic force. Either stretching or biaxial stretching (simultaneous or sequential) can be employed. Further, although the stretching ratio and the stretching speed can be appropriately selected depending on the purpose, in the present invention, the stretching speed is 5X 109%/min. The method of uniformly stretching at the above-mentioned high speed is suitable. Although it may be preferable that each layer of the multilayer structure is oriented after being stretched and shaped, it is not necessary that the layers be oriented.

In addition, in the present invention, regarding the water content of EVOH,
Although not particularly limited, it is preferably within 0.001 to 10% by weight. Generally, in the process of making a combination of EVOH and thermoplastic polyester, or in the process of melting or shaping the composition into a multilayer structure, EVOH
It is desirable that the water content is as low as 0.001 to 1% by weight. On the other hand, when molding a multilayer structure, EVO
}The moisture content of the I composition layer is 0.01 to 10% by weight, and the EV
OH, [1] It is preferable that the water content be as high as possible within a range that does not cause foaming in the nitrous layer.

The thus obtained multilayer structure of the present invention, especially the hot-stretched multilayer structure, has no holes, cranks, or uneven thickness in the composite (C) layer, so it has extremely good gas barrier properties and is bulk-resistant. This is effective for very good food packaging containers or containers that require aroma retention.

The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

E. Examples Example 1 Ethylene content 31 mol%, saponification degree 99.4%, melt index (MI) (190°C!, 216
0g load) 1.3g/lOmin. , melting point 181'0
80 parts by weight of EVOH (EVAL ■ manufactured by Kuraray), 90 mol% of isophthalic acid and lO as dicarboxylic acid components.
mol% terephthalic acid, while lO mol% 1,3-bis(β-hydroxyethoxy)benzene (BHB) and 15 mol% diethylene glycol (DEC) and 75 mol% ethylene glycol as diol components. 20 parts by weight of the thermoplastic polyester contained was placed in a twin screw type, vent type 40Φ extruder, and under nitrogen,
Extrusion pelletization was performed at 200°C. By the way, the dynamic viscoelastic coefficient E' of thermoplastic polyester at 120°C is 4x l08dyne/cm2, and the melt viscosity index (Ml) is 30g/10min. (190
°C under a load of 2160 g).

Using this pellet, a multilayer sheet was produced by applying it to a three-type, five-layer coextrusion device. The structure of the sheet is that both outermost layers of polystyrene resin (Idemitsu Styrene ET-61 from Idemitsu Petrochemicals, softening point 89°C) are 800μ, and adhesive resin layers (Mersen M-5420 from Toso, maleic anhydride-modified ethylene- Each layer (vinyl acetate copolymer) had a thickness of 50 μm, and the intermediate layer had a thickness of 50 μm of the EVOH Mi layer. The obtained sheet was passed through a vacuum-compressed air heating machine (stretching speed 9X 105
%/min. ), molding was carried out at 140°C.

The resulting cup had no cracks, unevenness, or uneven thickness, and had a good appearance. The humidity of this container was adjusted to 20°C and 65% RH, and the gas barrier properties were measured (model 10/50 manufactured by Mocon 23 24): 0.5cc・20μ/m2・2
Not only does it exhibit very good gas barrier properties of 4h+"atm, but the variation in measured values (R = maximum value minimum value) when measuring 20 samples is extremely small at 0.1, making it a highly reliable gas barrier. It was a barrier container.

Examples 2 to 5, Comparative Examples 1 to 7 The same conditions as in Example 1 were used except as shown in Table 1. The results are shown in Table 1.

(Left below) F. Effects of the Invention The multilayer structure of the present invention has no pinholes, cracks, unevenness, or local thickness deviations during heating stretching, particularly during heating high-speed stretching, and has excellent gas barrier properties and reliability.

Claims (3)

[Claims] (1) Ethylene-vinyl alcohol copolymer (A) with an ethylene content of 20 to 60 mol%, 50 to 95% by weight, isophthalic acid of 50 mol% or more based on the total dicarboxylic acid component, and diol As a component, 0.1 to 30 mol% of 1, based on the total diol component.
3-bis(β-hydroxyethoxy)benzene and/
Or a composition (C) consisting of 5 to 50% by weight of a thermoplastic polyester resin (B) containing diethylene glycol
It consists of at least two layers: a layer and a thermoplastic resin (D) layer,
and (A) and (D) are multilayer structures satisfying the following formula (I). 110℃≧X_A-X_D≧0℃...(I) (However, X_A is the melting point of A, and X_D is the melting point of D or the softening point if there is no melting point.) (2) The thermoplastic polyester resin (B) has a dynamic viscoelastic coefficient E' of 10^9 dyne/cm^ at 120°C.
2. The multilayer structure according to claim 1, wherein the number of layers is 2 or less. (3) The multilayer structure according to claim 1, wherein the thermoplastic resin (D) satisfies the following formula (I'). 110℃≧X_A-X_D≧10℃...(I')(
4) The multilayer structure according to claim 1, wherein the composition (C) layer and the thermoplastic resin (D) layer are laminated via an olefin resin modified with an unsaturated carboxylic acid or its anhydride.