JP2000177067A - Multilayered structure obtained by co-extrusion coating and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayered structure having good appearance by applying a molten multilayered structure, which consists of an EVOH layer reduced in thermal deterioration within an extruder, improved in heat stability (long-run properties) and high speed film forming properties at the time of production and also good in gas barrier properties and the carboxylic acid modified polyolefin resin layer adjacent thereto, to a base material by co-extrusion coating. SOLUTION: A multilayered structure is obtained by applying a molten multilayered structure, which consists of a layer with a thickness of 2-10 μm comprising an ethylene/vinyl alcohol copolymer with an ethylene content of 33-37 mol%, a saponification value of 99% or more and a melt index (190 deg.C, load of 2,160 or lower) of 6-10 g/10 min and the carboxylic acid modified polyolefin resin layer adjacent thereto, to a base material by co-extrusion coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH) having a good balance between thermal stability (long run property), high-speed film forming property and gas barrier property at the time of production. A.) A multilayer structure obtained by co-extrusion coating a molten multilayer body comprising a layer and a carboxylic acid-modified polyolefin resin layer adjacent thereto on a substrate and a method for producing the same.

[0002]

2. Description of the Related Art EVOH is a useful polymer material having excellent oxygen shielding properties, oil resistance, non-charging properties, mechanical strength, etc., and is widely used as various packaging materials such as films, sheets and containers. When EVOH is used for various types of packaging materials, not only performance for the intended purpose, but also slight coloring and holes on the appearance,
Fish eyes, streaks (streaks), rough skin, and transparency are problematic.

[0005] However, EVOH has a problem that coloring, pores, fish eyes, streaks, and rough skin are liable to occur during melt molding. Therefore, conventionally, the following various methods have been proposed as methods for suppressing these problems.

[0004] EVOH is usually obtained by adding a caustic alkali to an ethylene-vinyl acetate copolymer and saponifying it. When the saponified product is melt-formed as it is, it is easily thermally decomposed and the melt viscosity is remarkably lowered. At the same time, it cannot be used because of intense coloring. Many measures have been taken for this improvement. For example, it is known that the operation can be improved to some extent by washing the EVOH sufficiently with water or immersing the EVOH in an acid or an acid solution.
No. 37664, JP-A-48-25048, JP-A-51
No.-88544, JP-A-51-88545, Japanese Patent Publication No. 5
No. 5-19242. Further, it has been proposed to improve the melt moldability by adding a metal salt on the assumption that the heat stabilizing effect of a certain metal salt is remarkable.
No. 54, JP-A-52-955, JP-A-56-4120
No. 4, etc.

Further, by blending an olefin, a vinylsilane compound copolymerized polyolefin, etc.,
Japanese Patent Application Laid-Open No. 3-197138 discloses that the streak-like flow unevenness is improved by the elastic effect.

However, EVO using these processing methods
When H is formed by ordinary melt extrusion (extrusion temperature: about 20 ° C. higher than the melting point), the film formability can be improved to some extent, but severe conditions for EVOH, that is, 50 ° C. higher than the melting point of EVOH used. When the film is formed at a temperature higher than the above, the film is severely deteriorated in the extruder, causing fish eyes and streaks on the film film surface, resulting in poor film appearance, and finally a molded product that can be used cannot be obtained.

In particular, when extrusion coating is performed on a base material at a high speed in order to ensure productivity, the melt viscosity of EVOH is increased in order to increase the amount of resin that can be discharged when the same energy is applied and extruded. Need to be lowered. Therefore, it is necessary to perform melt film formation at a high temperature, and the influence of the above-mentioned deterioration of the resin is great. Among them, EVO on paper substrate
When coating a molten multilayer body containing H, it is necessary to form the EVOH layer thinly and uniformly in order to suppress costs and secure gas barrier properties, and therefore, defects in molded articles due to deterioration of the resin are likely to occur. .

Japanese Patent Application Laid-Open No. 4-234645 describes co-extrusion coating of a molten multilayer body comprising EVOH and an acid-modified polyolefin on a paper substrate. However, the publication discloses a suitable EV
There is no description of the composition of OH.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide an ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH) having a good balance between thermal stability (long run property), high-speed film forming property and gas barrier property at the time of production. It is an object of the present invention to provide a multilayer structure obtained by co-extrusion coating a molten multilayer comprising a layer and a carboxylic acid-modified polyolefin resin layer adjacent thereto on a substrate and a method for producing the same.

[0010]

The object of the present invention is to provide an ethylene content of 33 to 37 mol%, a saponification degree of 99% or more, and a melt index (at 190 ° C. under a load of 2160 g) of 6-1.
Multilayer structure obtained by coextrusion coating a molten multilayer body comprising a layer having a thickness of 2 to 10 μm comprising an ethylene-vinyl alcohol copolymer having a thickness of 0 g / 10 min and a carboxylic acid-modified polyolefin resin layer adjacent thereto. Achieved by providing the body.

At this time, the EVOH converts the carboxylic acid and / or its salt to 100 to 1000 p in terms of carboxylic acid.
pm, 50-300 pp in terms of metal for alkali metal salts
m, the phosphoric acid derivative is 10 to 1 in terms of phosphoric acid (H ₃ PO ₄ ).
It is preferably contained at 00 ppm. Further, the boron compound is converted to boric acid (H ₃ BO ₃ ) in an amount of 100 to 5000 ppm.
It is also preferable to contain. Further, it is preferable that the decomposition start temperature (JIS K 7120) of EVOH is 350 to 400 ° C.

The carboxylic acid-modified polyolefin resin has a density of 0.88 to 0.94 g / cm ³ and a melt index (at 190 ° C. under a load of 2160 g) of 3 to 15 g / 1.
In a preferred embodiment, the carboxylic acid-modified polyethylene resin is 0 minutes, and the base material is paper. In addition, 20
Oxygen permeation at 65 ° C. and 65% relative humidity is 1 to 5 cc
/ M ² · day · atm is preferred.

In the production of the multilayer structure, it is preferable that the take-up speed at the time of co-extrusion coating is 100 m / min or more and the die temperature is 240 ° C. or more.

It is preferable that the water content of the resin for coextrusion coating comprising the ethylene-vinyl alcohol copolymer is 0.02 to 0.15% by weight.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The EVOH used in the present invention is:
It is obtained by saponifying an ethylene-fatty acid vinyl copolymer and has an ethylene content of 33 to 37 mol% and a saponification degree of 99.
% Or more. The ethylene content is at least 33 mol%, preferably at least 34 mol%. If the ethylene content is less than 33 mol%, the thermal stability at the time of melt extrusion decreases, gelation is likely to occur, and streaks and fish eyes occur. In particular, this is remarkable when operating for a long time at a higher temperature and a higher speed than general conditions. The ethylene content is 3
It is at most 7 mol%, preferably at most 36 mol%.
If the ethylene content exceeds 37 mol%, the gas barrier properties are reduced, and it is no longer possible to maintain the inherent characteristics of EVOH. In particular, in the multilayer structure of the present invention, the thickness of the EVOH layer is 2
10 to 10 μm, which is thinner than a normal molded product, and in such a case, the influence of a decrease in gas barrier properties is large. Also,
If the value of the ethylene content is too high, the adhesiveness to the carboxylic acid-modified polyolefin resin layer tends to decrease. The degree of saponification is preferably at least 99%, more preferably 9%.
9.5% or more. When the saponification degree is less than 99%, the gas barrier properties are reduced and the melt stability is also reduced. As described above, the laminated body of the present invention is often operated at a higher temperature and at a higher speed than a general condition for a long time, so this point is important.

The melt index of the EVOH of the present invention (at 190 ° C. under a load of 2160 g) is from 6 to 10 g / 10 minutes. If the melt index exceeds 10 g / 10 minutes, the mechanical strength of the molded product is reduced, and the molded product lacks practicality. In addition, the melt viscosity becomes too low at the time of melt molding at a high temperature, and neck-in occurs, resulting in stable film formation. It becomes difficult to do. Preferably, it is 9 g / 10 minutes or less. 6g / 1
If the time is less than 0 minutes, the melt viscosity becomes too high, and the film may be broken at the time of melt molding, especially when the take-up speed is high, and it becomes difficult to form a melt film. In addition, when it is less than 6 g / 10 minutes, fish eyes and streaks are likely to be generated during long-time operation, and the output, that is, the amount of resin that can be discharged when the same energy is applied and extruded, also decreases. Since the multilayer structure of the present invention is formed by coating a thin EVOH layer at high speed, such a problem is particularly likely to occur. Preferably 4g / 1
It is 0 minutes or more, more preferably 6 g / 10 minutes or more.

The method for adjusting the melt index of EVOH includes (1) a method of adjusting the degree of polymerization by adjusting the amount of polymerization catalyst and polymerization temperature during polymerization, and (2) a method of crosslinking vinyltrimethoxysilane and the like during polymerization. (3) a method of blending a crosslinkable compound such as boric acid after polymerization, (4) a method of blending and adjusting a high polymerization degree EVOH and a low polymerization degree EVOH, and the like. Examples can be given. Also, these methods can be used in combination. Using the above method, the melt index (190
EVO under 2160g load) at 6-10g / 10min
Get H.

In addition, other copolymers (eg, propylene, butylene, unsaturated carboxylic acid or its ester (meth) acrylic acid, (meth) acrylic ester, etc.), vinyl Pyrrolidone (such as N-vinylpyrrolidone) can also be used as a copolymer component. In addition, plasticizers, heat stabilizers, UV absorbers, antioxidants, coloring agents, fillers, thickeners,
Blends with other resins (polyamide, partially saponified ethylene-vinyl acetate copolymer, etc.) are also free as long as the effects of the present invention are not impaired.

Hereinafter, the method for producing EVOH of the present invention will be described in detail. The polymerization of ethylene and vinyl ester may be any of solution polymerization, suspension polymerization, emulsion polymerization and bulk polymerization, and may be any of continuous type and batch type, for example, batch type solution polymerization. The polymerization conditions in this case are as follows.

Solvent: Alcohols are preferable, but other organic solvents (such as dimethyl sulfoxide) that can dissolve ethylene, vinyl ester and ethylene vinyl ester copolymer can also be used. As the alcohols, methyl alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, t-butyl alcohol and the like can be used, and methyl alcohol is particularly preferable.

Catalyst: 2,2'-azobisisobutyronitrile, 2,2'-azobis- (2,4-dimethylvaleronitrile), 2,2'-azobis- (4-methyl-2,
4-dimethylvaleronitrile), 2,2'-azobis-
(4-methoxy-2,4-dimethylvaleronitrile),
Azonitrile initiators such as 2,2′-azobis- (2-cyclopropylpropionitrile) and isobutyryl peroxide, cumyl peroxy neodecanoate;
Organic peroxide initiators such as diisopropylperoxycarbonate, di-n-propylperoxydicarbonate, t-butylperoxyneodecanoate, lauroyl peroxide, benzoyl peroxide and t-butyl hydroperoxide. Can be used. Temperature: 20-90 ° C, preferably 40-70 ° C. Time; 2 to 15 hours, preferably 3 to 11 hours. Polymerization rate; 10 to 90% based on the charged vinyl ester;
Preferably 30-80%. Resin content in solution after polymerization; 5 to 85%, preferably 20
~ 70%.

In addition, other than ethylene and vinyl ester, monomers copolymerizable therewith, for example, propylene, butylene, unsaturated carboxylic acid or its ester {(meth)
Acrylic acid, (meth) acrylic acid ester (methyl, ethyl) and the like, and vinylpyrrolidone (N-vinylpyrrolidone and the like)] can also be used as the copolymerization component.

After the polymerization for a predetermined time reaches a predetermined polymerization rate, a polymerization inhibitor is added if necessary, and unreacted ethylene gas is removed by evaporation, and then the unreacted vinyl ester is expelled. As a method of driving out unreacted vinyl ester from the ethylene vinyl ester copolymer from which ethylene has been removed by evaporation, for example, the copolymer solution is continuously supplied at a constant rate from the upper part of a tower filled with Raschig rings, and A method in which an organic solvent vapor such as methanol is blown in, a mixed vapor of an organic solvent such as methanol and unreacted vinyl ester flows out from the top of the tower, and the copolymer solution from which unreacted vinyl ester is removed is taken out from the bottom of the tower. Is done.

An alkali catalyst is added to the copolymer solution from which unreacted vinyl ester has been removed to saponify the vinyl ester component in the copolymer. The saponification method can be either a continuous type or a batch type. As the alkali catalyst, sodium hydroxide, potassium hydroxide, alkali metal alcoholate and the like are used. For example, the saponification conditions in the case of the batch system are as follows. Concentration of the copolymer solution; 10 to 50%. Reaction temperature; Amount of catalyst used: 0.02 to 0.6 equivalent (per vinyl ester component). Time; 1-6 hours.

Since the EVOH after the reaction contains an alkali catalyst, by-product salts, other impurities, etc., these are neutralized if necessary and then removed by washing. E obtained
Various compounds are added to VOH as needed. Above all, in order to exhibit the effects of the present invention more remarkably,
A method in which EVOH is immersed in a solution of the above compound is desirable. This processing can be performed by either a batch method or a continuous method. In this case, the shape of the saponified product may be any shape such as powder, granule, sphere, and columnar chip.

The EVOH of the present invention preferably contains 10 to 50 ppm of a metal salt of Group 2 of the periodic table in terms of metal. Thereby, even in a molten state at a high temperature for a long time, the viscosity does not significantly change, a long-time operation is possible, and a molded article having a good appearance can be obtained.

The metal salt of Group 2 of the periodic table is not particularly limited, and examples thereof include a magnesium salt, a calcium salt, a barium salt and the like. Examples of such metal salts include carboxylate, hydroxycarboxylate, phosphate, borate, etc., but lactate or acetate is preferred, and acetate is particularly preferred. A preferable content of the metal salt of Group 2 of the periodic table is 10 to 50 pp in terms of metal.
m. It is more preferably at least 15 ppm, and most preferably at least 20 ppm. If it is less than 10 ppm, fish eyes tend to increase on the film surface in a long-time melt film formation. Also, more preferably 45 ppm or less,
Optimally, it is 40 ppm or less. If it exceeds 50 ppm, in the case of melt molding at a high temperature (around 280 ° C.), it foams in the extruder die, causing voids and holes.

Further, the EVOH of the present invention can be obtained by converting a carboxylic acid and / or a salt thereof from 100 to 1000 in terms of carboxylic acid.
It is preferable to contain ppm. Thereby, coloring of the melt molded article can be prevented. The carboxylic acid is not particularly limited, and includes acetic acid, propionic acid, lactic acid, glycolic acid, and the like. Particularly, acetic acid and lactic acid are preferable, and acetic acid is most preferable. A carboxylic acid having a plurality of carboxyl groups (polybasic acid) such as adipic acid or phthalic acid in a molecule may crosslink EVOH molecules to deteriorate thermal stability. Preferably, only acids are used. The preferred content of the carboxylic acid and / or its salt is 100 to 1000 ppm. It is more preferably at least 150 ppm, and most preferably 2 ppm.
It is at least 00 ppm. If it is less than 100 ppm, there is no effect in preventing coloring, and the molded article turns yellow. It is more preferably at most 500 ppm, and most preferably at most 400 ppm. If it exceeds 1000 ppm, it tends to gel at the time of melting, which causes fish eyes and gel, resulting in poor appearance.

The EVOH of the present invention preferably contains 50 to 300 ppm of an alkali metal salt in terms of a metal. Thereby, the adhesiveness with the adhesive used for coextrusion coating is obtained, and a good coextrusion molded product is obtained. Examples of the alkali metal salt include, but are not particularly limited to, a sodium salt and a potassium salt. Examples of such metal salts include carboxylate, hydroxycarboxylate, phosphate, borate, etc., but lactate or acetate is preferred, and acetate is particularly preferred.

The preferred content of the alkali metal salt is 50 to 300 ppm in terms of metal. More preferably 70p
pm or more, and optimally 90 ppm or more. 50
If it is less than ppm, it may cause poor adhesion during co-extrusion film formation.
It is more preferably at most 250 ppm, and most preferably at most 200 ppm. If it exceeds 300 ppm, coloring due to decomposition occurs and the appearance of the molded article becomes poor.

The EVOH of the present invention preferably contains a phosphoric acid derivative in an amount of 10 to 100 ppm in terms of phosphoric acid (H ₃ PO ₄ ). Thereby, EVOH with less coloring at the time of melt molding and hardly gelling can be obtained. The phosphoric acid derivative is not particularly limited, and phosphoric acid or a salt thereof can be used.
The phosphate may be contained in any form of a first phosphate, a second phosphate, and a third phosphate, and the cation species is not particularly limited. Preferred are alkali metal salts and metal salts of Group 2 of the periodic table.

Examples of the phosphoric acid derivative include sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate and dipotassium hydrogen phosphate, and potassium dihydrogen phosphate is particularly preferred. The preferred content of the phosphoric acid derivatives include phosphoric acid (H ₃ PO ₄₎ is 10~100ppm in terms. It is more preferably at least 10 ppm, and most preferably at least 20 ppm.
ppm or more. If it is less than 10 ppm, the effect of preventing coloring during melt molding cannot be obtained, and the appearance will be poor due to coloring. It is more preferably at most 80 ppm, most preferably at most 60 ppm.
ppm or less. If it exceeds 100 ppm, gelation is promoted at the time of melt molding, resulting in poor appearance due to frequent occurrence of fish eyes and gels.

The EVOH of the present invention preferably contains a boron compound in an amount of from 100 to 5000 ppm in terms of boric acid (H ₃ BO ₃ ), because heat stability, particularly long-run property at high temperatures, can be further improved. As the boron compound used in the present invention, boric acid derivatives such as boric acid, boric acid esters and borates are preferably used. Examples of boric acid include orthoboric acid, metaboric acid, tetraboric acid, and the like.As borate salts, sodium metaborate, sodium tetraborate, sodium pentaborate, borax, lithium borate,
Potassium borate and the like can be mentioned. Examples of the borate ester include triethyl borate and trimethyl borate. Of these, orthoboric acid (simply referred to as boric acid), borax and their derivatives are preferred because they have large effects and are inexpensive.

The preferred content of the boron compound is 100 to 5000 ppm in terms of boric acid (H ₃ BO ₃ ). More preferably, it is 500 ppm or more, and optimally 1000 ppm.
ppm or more. By being in this range, it is possible to obtain EVOH having good melt extrudability in which torque fluctuation during heating and melting is suppressed. In addition, more preferably 3000 ppm
Or less, and optimally 2000 ppm or less. 50
If it exceeds 00 ppm, gelation due to localization of boric acid proceeds, and fish eyes and gels frequently occur during melt molding, resulting in poor molding. If it is less than 100 ppm, it is difficult to obtain such an effect.

The method for incorporating the above various compounds into EVOH is not particularly limited. For example, there are a method of immersing EVOH in a solution in which the compound is dissolved, a method of melting EVOH and mixing the compound, and a method of dissolving EVOH in an appropriate solvent and mixing the compound.

When EVOH is immersed in a solution containing the various compounds, the concentration of the compound in the solution is not particularly limited. The solvent of the solution is not particularly limited, but is preferably an aqueous solution for reasons such as handling. It is desirable that the weight of the solution when the saponified product is immersed is at least three times, preferably at least 20 times the weight of the saponified product when dried. The preferred range of the immersion time varies depending on the form of the EVOH, but in the case of a chip of about 1 to 10 mm, the immersion time is preferably 1 hour or more, preferably 2 hours or more.

It is also preferable that the decomposition start temperature (JIS K 7120) of the EVOH of the present invention is 350 to 400 ° C. By having the decomposition start temperature in such a range, molding failure due to deterioration of the resin hardly occurs even in a long-time operation at a high temperature. The decomposition initiation temperature is more preferably at least 355 ° C, and most preferably at least 360 ° C.

As the EVOH of the present invention, a single EVO
In addition to H, a plurality of EVOHs having different degrees of polymerization, ethylene content or saponification degree can be blended and used. It is preferable that the EVOH of the present invention does not contain any other kind of thermoplastic resin, but a small amount may be added as long as the effects of the present invention are not impaired.
As the thermoplastic resin, various polyolefins (polyethylene, polypropylene, poly 1-butene, poly 4-methyl-1-pentene, ethylene propylene copolymer, copolymer of ethylene and α-olefin having 4 or more carbon atoms, polyolefin and Copolymers with maleic anhydride, ethylene vinyl ester copolymers, ethylene acrylate ester copolymers, or modified polyolefins obtained by graft-modifying these polyolefins with unsaturated carboxylic acids or derivatives thereof, and various nylons (nylon 6 , Nylon 6
6, nylon 6/66 copolymer), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, and modified polyvinyl alcohol resin.

Further, the EVOH of the present invention contains various plasticizers,
It is also possible to add an appropriate amount of a stabilizer, a surfactant, a coloring agent, an ultraviolet absorber, a slip agent, an antistatic agent, a drying agent, a crosslinking agent, a metal salt, a filler, a reinforcing agent for various fibers, and the like.

The EVOH of the present invention is used for extrusion coating. In such extrusion coating molding, film formation is often performed at a high speed in order to improve production efficiency. Then, in order to prevent neck-in caused by high-speed film formation, melt film formation is performed at a higher temperature than usual. In such a case, it is preferable to use the EVOH of the present invention which is excellent in thermal stability and high-speed film forming property.

Also, among the extrusion coatings, EV
A method of co-extrusion coating a molten multilayer body containing an OH layer on a substrate is preferred for the following reasons. Above all E
Optimally, a molten multilayer body comprising a VOH layer and a carboxylic acid-modified polyolefin-based resin layer adjacent thereto is co-extruded on a substrate. EVOH resins are generally more expensive than general-purpose resins such as polyolefin resins.
The H layer can be made thinner. In addition, it is also possible to form a laminated structure with an adhesive resin (often a carboxylic acid-modified polyolefin resin) layer for securing adhesiveness to a base material and a hydrophobic resin layer for preventing EVOH from absorbing moisture in a single coating operation. it can. Further, by extruding simultaneously with a resin having good extrusion moldability, such as a polyolefin resin, it is often possible to form a more stable film than coating with a single layer of EVOH.

The carboxylic acid-modified polyolefin to be coextruded with EVOH is a polyolefin having a carboxyl group (or a carboxyl anhydride group) in the molecule, and the polyolefin is converted to an α, β-unsaturated carboxylic acid or an anhydride thereof. And those obtained by random copolymerization of an olefin monomer and an α, β-unsaturated carboxylic acid or an anhydride thereof. Examples of the α, β-unsaturated carboxylic acid or its anhydride include acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride, and maleic anhydride is preferred.

The carboxylic acid-modified polyolefin has a density of 0.88 to 0.94 g / cm ³ , preferably 0.90 to 0.93 g / cm ³ , and more preferably 0.90 to 0.93 g / cm ³ .
Carboxylic acid-modified polyethylene of 5 to 0.92 g / cm ³ is preferred. Representative examples of such carboxylic acid-modified polyethylene include those using low-density polyethylene produced by a high-pressure method or linear low-density polyethylene (LLDPE) produced by a low-pressure method using a Ziegler-type catalyst as a base resin. Of these, those using LLDPE as a base resin are preferred from the viewpoint of film forming properties.

The melt index (at 190 ° C. under a load of 2160 g) of the carboxylic acid-modified polyolefin is 3
１５15 g / 10 min. It is preferably at most 12 g / 10 min, more preferably at most 10 g / 10 min. It is preferably at least 4 g / 10 min, more preferably at least 6 g / 10 min. This is because when there is no difference between the EVOH and the melt index that are coextruded at the same time, unevenness of the interface is less likely to occur, and a molded article with good appearance can be obtained.

The melt molding temperature of the EVOH of the present invention depends on the melting point of the copolymer, the molding method, and the like, and is not particularly limited. However, from the viewpoint of preventing neck-in in high-speed molding, the die temperature is set at 240 ° C. It is preferable that the temperature is not lower than ° C. It is more preferably at least 250 ° C., even more preferably at least 260 ° C. Further, it is preferable that the take-up speed at the time of extrusion coating is 100 m / min or more from the viewpoint of improving production efficiency. It is more preferably at least 120 m / min, even more preferably at 150 m / min.
More than a minute.

The raw material E used for coextrusion coating
The water content of VOH is preferably adjusted to 0.02 to 0.15% by weight. More preferably, the content is 0.10% by weight or less. If the water content exceeds 0.15% by weight, foaming is likely to occur during melt molding at a high temperature, and voids and holes are likely to occur in the molded product. More preferably 0.05% by weight
That is all. If the moisture content is too low to be less than 0.02% by weight, the drying temperature is too high or the drying time is too long, and the resin turns yellow due to thermal deterioration. In order to adjust the moisture content to the above range, a method of drying an EVOH chip in a temperature range of 80 to 110 ° C may be mentioned. The drying time is appropriately adjusted depending on the capacity of the dryer and the amount of the resin to be dried.

The substrate of the multilayer structure manufactured by using the EVOH of the present invention is not particularly limited, and examples thereof include substrates such as paper, plastic film, and metal foil. In particular, a paper substrate cannot be melt-molded per se and is a substrate having no gas barrier properties. Therefore, it is most useful to extrusion-mold the EVOH of the present invention. At this time, as the paper base material, a resin such as low-density polyethylene (hereinafter sometimes abbreviated as LDPE) or the like, which is already coated on both surfaces or one surface thereof, may be used.

The layer structure of the multilayer structure obtained by co-extrusion coating the thus obtained molten multilayer comprising an EVOH layer and a carboxylic acid-modified polyolefin layer on a substrate is not particularly limited, The following configuration is preferable. here,
The carboxylic acid-modified polyolefin layer was indicated as AD, and the thermoplastic resin layer was indicated as TR.

Inner layer: AD / EVOH / AD / substrate: outer layer Inner layer: TR / AD / EVOH / AD / TR / substrate / T
R: outer layer inner layer: TR / AD / EVOH / AD / TR / TR / substrate / TR: outer layer inner layer: EVOH / AD / TR / substrate / TR: outer layer inner layer: TR / AD / EVOH / substrate / TR: Outer layer Inner layer: EVOH / AD / TR / AD / EVOH / AD /
TR / substrate / TR: outer layer Inner layer: TR / AD / EVOH / AD / substrate / TR: outer layer Inner layer: AD / EVOH / AD / substrate / TR: outer layer

The thermoplastic resin represented by TR in the above examples is not particularly limited, and different types of thermoplastic resins may be used in one multilayer structure. The most typical thermoplastic resin is polyolefin, especially polyethylene, especially having a density of 0.88 to 0.94 g / cm.
³ , preferably 0.90 to 0.93 g / cm ³ , more preferably 0.905 to 0.92 g / cm ³ polyethylene is important in the present invention. Such polyethylene is useful in terms of moisture resistance, heat sealability, flexibility, and low cost. Representative examples of such polyethylene include low-density polyethylene produced by a high-pressure method and linear low-density polyethylene (LLDPE) produced by a low-pressure method using a Ziegler-type catalyst.
E is preferred from the viewpoint of film forming properties.

Further, the EVO in the multilayer structure of the present invention
The thickness of the H layer is 2 to 10 μm. If it is less than 2 μm, it is difficult to prevent the generation of pinholes under high-speed film forming conditions. More preferably, it is 3 μm or more. Conversely 1
If it exceeds 0 μm, the material cost increases and the appearance of the surface of the molded product deteriorates. It is more preferably 8 μm or less, and still more preferably 6 μm or less.

The multilayer structure of the present invention has an oxygen transmission rate at 65% relative humidity of 1% at 20 ° C. and 65% relative humidity.
It is preferably 5 cc / m ² · day · atm. If it exceeds 5 cc / m ² · day · atm, the long-term preservability of the contents will decrease. More preferably, 4 cc / m ² · d
ay · atm or less, optimally 3 cc / m ² · da
y · atm or less. On the other hand, 1 cc / m ² · day · a
If it is less than tm, the thickness of the EVOH layer used is too large, which is not preferable from the viewpoint of material cost. It is more preferably at least 1.2 cc / m ² · day · atm, and most preferably at least 1.5 cc / m ² · day · atm.

The multilayer structure thus obtained is processed into the shape of a carton or a cup and used as various paper containers. Such a paper container can store various beverages and the like for a long period of time.

[0054]

Now, the present invention will be described more specifically below with reference to working examples. Hereinafter, “%” and “parts” are based on weight unless otherwise specified. In addition, all the water used ion-exchange water.

(1) Determination of Acetate Ion and Phosphate Ion 10 g of a dry chip as a sample was put into 50 ml of a 0.01 N hydrochloric acid aqueous solution and stirred at 95 ° C. for 6 hours. The aqueous solution after stirring was quantitatively analyzed using ion chromatography, and the amounts of acetate ions and phosphate ions were quantified. The column uses ICS-A23 manufactured by Yokogawa Electric Corporation.
The eluent was an aqueous solution containing 2.5 mM sodium carbonate and 1.0 mM sodium hydrogen carbonate. In the determination, a calibration curve prepared using an aqueous solution of acetic acid and phosphoric acid was used. From the amounts of acetate ion and phosphate ion thus obtained, the content of each acid and / or salt thereof was obtained as a value converted to the weight of each acid.

(2) Determination of Na, K, and Ca Ions 10 g of a dry chip as a sample was put into 50 ml of a 0.01 N hydrochloric acid aqueous solution, and stirred at 95 ° C. for 6 hours. The aqueous solution after stirring was quantitatively analyzed using ion chromatography, and the amounts of Na ions, K ions and Ca ions were quantified. The column used was ICS-C25 manufactured by Yokogawa Electric Corporation, and the eluent was an aqueous solution containing 5.0 mM tartaric acid and 1.0 mM 2,6-pyridinedicarboxylic acid. In the determination, a calibration curve prepared with an aqueous solution of sodium chloride, potassium chloride and calcium chloride was used. The thus obtained Na ion, K ion and C ion
From the amount of a ion, the amount of the alkali metal salt and the metal salt of Group 2 of the periodic table in the dried chip was obtained as a value converted to the metal weight.

(3) Determination of Boron Compound 100 g of a dry chip as a sample was put in a magnetic crucible and ashed in an electric furnace. The obtained ash is dissolved in 200 mL of a 0.01 N nitric acid aqueous solution, the content of the boron element is quantified by atomic absorption spectrometry, and the content thereof is determined as boric acid (H ₃ BO ₃ ).
And the content of the boron compound was obtained.

(4) Moisture content of EVOH 20 g of a chip as a sample is placed in a well-dried weighing bottle and heated in a hot air drier at 120 ° C. for 24 hours to obtain a moisture content represented by the following equation from the obtained chip weight. Was. Water content (wt%) = {(weight of sample−weight after drying) / weight of sample} × 100

(5) Decomposition starting temperature The sample was dried in vacuum to adjust the volatile content to 0.1% by weight or less, and a TG-DTA measuring device (Seiko Electronics Co., Ltd.
G-DTA220), the decomposition start temperature was measured at a heating rate of 10 ° C./min under measurement conditions according to JIS K7120.

(6) Oxygen Permeation A part of the obtained multilayer structure was cut out and cut at 20 ° C.-65%
After adjusting the humidity to RH, the oxygen permeation amount (ml / m ² · day · atm) was measured by an oxygen permeation amount measurement device (OX-TRAN-10 / 50A, manufactured by Modern Control).

(7) Melt index (MI) Measured under the conditions of a temperature of 190 ° C. and a load of 2160 g using a melt indexer according to ASTM-D1238. In the present invention, the melting point of E
With respect to VOH, a load of 21
Measure at 60 g and use the value extrapolated to 190 ° C.

(8) Evaluation of Coextrusion Coating Properties Using EVOH, two types and three layers of coextrusion coating were performed on a paper base material. Substrate: Kishu Paper Made "golden sand" (basis weight 80 g / m ^2, thickness 1
(00 μm, width 600 mm)

The equipment used for extrusion coating is as follows.・ Extruder for EVOH; L / D = 26, single screw having a diameter of 50 mmφ ・ Extruder for carboxylic acid-modified polyolefin; L / D = 3
1. Single screw with a diameter of 65mmφ ・ Die shape; width 620mm, lip interval 0.7mm,
Air gap 110mm

The composition of the co-extrusion coating part is an adhesive layer /
EVOH / adhesive layer, thickness configuration is 25/5 / 25μ
m. An extruder for EVOH, an extruder for adhesive layer, and a feed block and a T-die for joining and distributing resins supplied from the respective extruders were used. As the adhesive layer, a linear low-density polyethylene modified with maleic anhydride ("Admer AT1188" manufactured by Mitsui Chemicals, Inc.) was used.
The temperature conditions for coextrusion coating are feed block,
The die was 280 ° C., and the take-off speed was 150 m / min. Co-extrusion coating was performed under the above conditions, and the following evaluation was performed.

Neck-in evaluation The multilayer structure obtained immediately after the start of
The width of the resin portion subjected to coextrusion coating was measured at an interval of 1 m, and a value subtracted from the die width was defined as a neck-in width. Neck-in evaluation criteria; A: less than 50 mm. B: 50 to 100 mm. C: 100 to 200 mm. D: 200 mm or more.

Evaluation of Film Appearance Immediately after the start of the coextrusion coating, 30 minutes and 3 hours later, samples were taken, and the occurrence of fish eyes, streaks, and the state of coloring were visually evaluated. Regarding fish eyes, the number of fish eyes that could be easily confirmed visually was counted in a range of 10 cm × 10 cm. The occurrence of streaks and coloring were evaluated according to the following criteria. -Fish eye evaluation criteria A; less than 5 pieces / 100 cm ² . B: 5 to 20 pieces / 100 cm ² . C: 20 to 50 pieces / 100 cm ² . D: 50 pieces / 100 cm ² or more. Streak evaluation criteria A: No streak was observed. B: A slight streak was observed. C: A clear streak was confirmed. D: Many streaks were confirmed. Coloring evaluation criteria A: colorless. B: slight yellowing. C: Clear yellowing. D: Yellowing is remarkable.

(9) Adhesive force between EVOH / carboxylic acid-modified polyolefin interlayer The “paper / carboxylic acid-modified polyolefin / EVOH / carboxylic acid-modified polyolefin” multilayer structure immediately after the start of co-extrusion coating was applied to the AD / EVOH interlayer on the paper side. The T-peel strength was measured with an autograph (tensile speed 350 mm / m
in)). It was determined as follows based on the value of the obtained peel strength. -Adhesion evaluation criteria A: 600 g / cm or more. B: 600 to 400 g / cm (a level with practically no problem). C: 400 to 200 g / cm (level of practically insufficient adhesion). D: less than 200 g / cm (not reaching a practical level).

Example 1 Withstand pressure 100 kg / cm^Two8630 vinyl acetate
0 parts, methanol 34400 parts, AIBN (azobisui
8.6 parts of sobutyronitrile)
After the element substitution, the temperature is raised and raised to an internal temperature of 60 ° C and ethylene pressure of 3
9.5kg / cm ^TwoWas adjusted. 9.2 hours at that temperature,
After polymerization while maintaining pressure, add 7 parts of hydroquinone
Then, the polymerization tank was returned to normal pressure, and ethylene was removed by evaporation. Pull
Subsequently, this methanol solution was filled with Raschig rings.
The discharge tower continuously flows down from the top of the tower, while the bottom
Methanol vapor was blown in from the unreacted vinyl acetate
Is released from the top of the tower together with methanol vapor.
Unreacted vinyl acetate is removed by removing through a denser.
Of ethylene vinyl acetate copolymer of 0.01% or less
% Methanol solution was obtained. The polymerization rate at this time is
30% based on vinyl, ethylene content is 35mol%
there were.

Next, a methanol solution of an ethylene-vinyl acetate copolymer was charged into a saponification reactor, and a caustic soda / methanol solution (80 g / L) was added in an amount of 0.4 equivalent to the vinyl acetate component in the copolymer. Was added, and methanol was added to adjust the copolymer concentration to 20%. The temperature was raised to 60 ° C., and the reaction was carried out for about 4 hours while blowing nitrogen gas into the reactor. After that, the reaction is stopped by neutralizing with acetic acid, extruded into water from a metal plate having a circular opening, precipitated, and cut to obtain a diameter of about 3 mm and a length of about 5 m.
m chips were obtained. The obtained chips were subjected to liquid removal by a centrifugal separator, and a large amount of water was added thereto to repeat washing and liquid removal. The saponification degree of the obtained saponified ethylene-vinyl acetate copolymer was 99.7 mol%.

10 kg of the chip was added to 0.4 g / acetic acid.
L, potassium dihydrogen phosphate 0.05 g / L, calcium acetate 0.1 g / L, and 150 L of an aqueous solution containing sodium acetate 0.1 g / L, and stirred for 4 hours. Then, the obtained pellet was taken out, and after centrifugal dewatering, 80
Hot air drying was performed at 6 ° C. for 6 hours and at 105 ° C. for 24 hours.

The pellet obtained after drying had an MI of 8 g / l.
At 0 min, the calcium salt contained 30 ppm in terms of metal, acetic acid and its salt in 600 ppm in terms of acetic acid, the alkali metal salt contained 150 ppm in terms of metal, and the phosphoric acid derivative contained 35 ppm in terms of phosphoric acid. The moisture content after drying was 0.08% by weight, and the decomposition start temperature was 380 ° C.

Using the obtained EVOH pellets, two types and three layers of co-extrusion coating were carried out on a paper-based substrate, and the results are shown in Table 2.

Examples 2 to 7, Comparative Examples 1 to 6 In place of the EVOH used in Example 1, the EVs shown in Table 1 were used.
A coextrusion coating test was performed and evaluated in the same manner as in Example 1 except that OH was used. The aqueous solution in which the chips were dispersed was prepared by appropriately adjusting the amounts of acetic acid, potassium dihydrogen phosphate, calcium acetate, sodium acetate, and boric acid. The results are summarized in Table 2.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

According to the present invention, an EVOH layer and a carboxylic acid-modified polyolefin adjacent to the EVOH layer having reduced heat deterioration in an extruder, improved thermal stability (long run property) during production, and improved high-speed film forming property. The present invention provides a multilayer structure having good appearance, which is obtained by co-extrusion coating a molten multilayer body composed of a resin layer on a substrate.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 29/04 C08L 29/04 S // B29K 23:00 29:00 B29L 9:00

Claims (10)

[Claims] 1. An ethylene content of 33 to 37 mol%, a saponification degree of 99% or more, and a melt index (190 ° C., 21
(Under a load of 60 g) A co-extrusion of a molten multilayer body consisting of an ethylene-vinyl alcohol copolymer layer having a thickness of 2 to 10 μm and a carboxylic acid-modified polyolefin resin layer adjacent thereto, which is made of an ethylene-vinyl alcohol copolymer of 6 to 10 g / 10 min. Multilayer structure with coating. 2. An ethylene-vinyl alcohol copolymer comprising carboxylic acid and / or a salt thereof in an amount of 100 to 1000 ppm in terms of carboxylic acid, an alkali metal salt in an amount of 50 to 300 ppm in terms of metal, and a phosphoric acid derivative in a phosphate group (PO).
₄ ) The multilayer structure according to claim 1, which contains 10 to 100 ppm in terms of conversion. 3. An ethylene-vinyl alcohol copolymer comprising a boric acid derivative in an amount of 100 to 100% in terms of boric acid (H ₃ BO ₃ ).
The multilayer structure according to claim 1, which contains 5000 ppm. 4. A carboxylic acid-modified polyolefin resin,
5. A carboxylic acid-modified polyethylene resin having a density of 0.88 to 0.94 g / cm < ³ > and a melt index (at 190 [deg.] C. under a load of 2160 g) of 3 to 15 g / 10 minutes.
The multilayer structure according to any one of the above. 5. The multilayer structure according to claim 1, wherein the oxygen permeation amount at 20 ° C. and a relative humidity of 65% is 1 to 5 cc / m ² · day · atm. 6. The multilayer structure according to claim 1, wherein the substrate is paper. 7. The method for producing a multilayer structure according to claim 1, wherein a take-off speed at the time of co-extrusion coating is 100 m / min or more. 8. The method for producing a multilayer structure according to claim 1, wherein the die temperature at the time of coextrusion coating is 240 ° C. or higher. 9. An ethylene content of 33 to 37 mol%, a saponification degree of 99% or more, and a melt index (190 ° C., 21
Coextrusion coating resin consisting of an ethylene-vinyl alcohol copolymer for 6 to 10 g / 10 minutes under a load of 60 g). 10. The resin according to claim 9, wherein the water content is 0.02 to 0.15% by weight.