JP2001098080A - Method for production of ethylene/vinyl alcohol copolymer resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To feed water-containing ethylene/vinyl alcohol copolymer (EVOH) resin pellets at good efficiency by adjusting the amount of the water adherent to the surfaces of the pellets to a specified value or below in feeding them into the extruder. SOLUTION: In feeding EVOH resin pellets into the feed port of a twin-screw extruder 20 and melt-kneading them in a hydrated state, the water content of the entire resin pellets is adjusted to a value in the range of 0.5-70 wt.%, and the content of water adherent to their surfaces is adjusted to below 10 wt.%. This prevents bridging in the hopper of the feeder, the generation of a water vapor at the bottom of the hopper, and the fusion of the pellets to stabilize the feed of the pellets into the extruder. As a result, the obtained resin composition is stabilized against fluctuation in the content of an acid, a metal salt or the like coming from the added water and therefore has good heat stability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a resin composition by supplying an ethylene-vinyl alcohol copolymer (hereinafter also referred to as "EVOH") resin pellets in a water-containing state to an extruder.

[0002]

2. Description of the Related Art Ethylene-vinyl alcohol copolymers have been widely used for food packaging because of their high gas barrier properties and excellent oil and organic solvent resistance, fragrance retention and transparency. For food packaging, various molding methods such as a film formed by extrusion, a bottle formed by blow molding, and various packs formed by vacuum forming are employed. In these various processing methods, resin pellets must be supplied to an extruder and the melting temperature must be 200 ° C or higher. If the thermal stability of the polymer is not improved, the polymer will deteriorate during melt molding. However, fish eyes and lumps are generated, which causes the quality of the product to deteriorate. Therefore, it is necessary to remove the saponification catalyst residue contained in the resin production from the polymer or to add a heat stabilizer.

Conventionally, in order to remove saponification catalyst residues contained in resin production from a polymer, resin pellets are put into a washing vessel, contacted with a washing liquid (water) in a solid state, and extracted from the inside of the resin pellets by diffusion. (Japanese Patent Publication No. 55-19242). Further, in order to add a heat stabilizer to the polymer, the resin pellets are placed in an acid treatment vessel, and contacted with an aqueous acid solution in a solid state to impregnate or adsorb the acid inside the resin pellets (Japanese Patent Publication No. 55-55).
-19242).

[0004] However, in the conventional method, a large amount of water adheres to the resin, and in order to remove the water, hot air drying using a dryer for a long time is required, and the operation is complicated.

[0005] EV to which the above-mentioned trace components are added
The OH pellets can be obtained by (1) spraying an aqueous solution of a trace component on the EVOH pellets, mixing them with a Henschel mixer, and then drying (JP-A-55-12108). A method in which a trace component is mixed and dry-blended with a supermixer (JP-A-57-34148). 64-66262), (4)
After adjusting the water content of the EVOH pellets to 20 to 80% by weight, the EVOH pellets are brought into contact with an aqueous solution of at least one compound selected from the group consisting of boron compounds, acetates and phosphate compounds (WO 99/05213). Etc. are known.

[0006] However, in the addition method (1) or (2), the uniformity of the trace components in the EVOH pellets is insufficient and the addition amount is difficult to control, so that a product of stable quality is obtained. It is difficult. The method (3) or (4) has an advantage that the amount of the trace component contained in the EVOH pellet can be easily controlled by adjusting the solution concentration. However, when the EVOH pellets treated by the method are molded by melt extrusion, the motor torque and torque fluctuation of the extruder become large, so that it is usually necessary to add a lubricant to the resin composition composed of EVOH at the time of extrusion. Was. However, since the resin composition composed of EVOH is suitably used for food packaging and the like, the addition of such a lubricant is not always desirable from a sanitary point of view. Therefore, reduction or elimination of the lubricant has been desired.

[0007] The EVOH pellets treated by the method (3) or (4) are usually obtained by precipitating a methanol solution of EVOH after saponification in a coagulation bath comprising a water / methanol mixed solution. Is obtained by cutting However, the ethylene content is 20 mol%
Less than EVOH and / or less than 95% saponification degree
VOH is difficult to precipitate strands in the coagulation bath, and it is difficult to produce pellets stably because cut mistakes and fine powder are liable to occur, and in some cases, strands cannot be precipitated. The paste-like EVOH precipitates as crumbs solidified in an irregular shape. However, when the crumb-like precipitate is treated by the method (3) or (4), it is difficult to uniformly mix the trace components, and a stable quality product cannot be obtained.

On the other hand, even when EVOH has an ethylene content of 20 mol% or more and a saponification degree of 95% or more, if the strand is deposited at a high speed in order to improve production efficiency, the precipitation of the strand becomes unstable. Therefore, it is difficult to stably produce the pellets, and the processing method (3) or (4) cannot obtain a product of stable quality.

Further, from the viewpoint of the manufacturing process, in the case of a conventional method of immersing EVOH pellets in a treatment solution containing an acidic substance and / or a metal salt, a treatment bath for immersing the pellets may be used. A treatment tower is required, and the treatment solution used in such a treatment bath or treatment tower is disposable or collected because acidic substances and / or metal salts are consumed after EVOH treatment. Appropriate amounts of acidic substances and / or metal salts need to be re-added.

It is not preferable to dispose of the treatment liquid from the viewpoint of environmental impact, and the treatment liquid is usually discarded through a wastewater treatment facility. When the processing solution is collected and reused, equipment for re-adding acidic substances and / or metal salts and impurities such as oligomers in the processing solution are used to supply products of stable quality. Removal equipment was required.

As described above, the conventional method has a problem that a large processing apparatus needs to be installed and long-time processing is required, and the manufacturing cost is also high.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present inventors have proposed a method for efficiently removing water from a water-containing and molten ethylene-vinyl alcohol copolymer resin by using an extruder. As a result of studying a method for producing a low-cost ethylene-vinyl alcohol copolymer resin by efficiently adding additives and additives to the resin, when water-containing ethylene-vinyl alcohol copolymer resin pellets are supplied to the extruder, In addition, if the amount of water deposited on the surface of the resin pellets is large, for example, the pellets form a bridge in a hopper, or form a block in a feeder, or water-containing ethylene-vinyl alcohol copolymer is generated by generating steam from an extruder. It has been found that there are various problems such as fusion between resin pellets.

As a specific problem, a bridge is generated in the hopper of the feeder, and the supply of the raw material resin to the extruder becomes defective. Alternatively, surface water separated in the feeder is supplied to the extruder, and steam is generated in the lower part of the hopper, fusion of the raw material pellets occurs, and supply of the raw material resin to the extruder becomes defective. In particular, in the case of water-containing EVOH, the melting point is lowered, so that it is easily affected, and the pellets are easily fused to each other in the lower part of the hopper. In addition, the amount of addition of the acid / metal salt becomes unstable, causing problems such as a decrease in thermal stability.

According to the present invention, in order to solve the above-mentioned conventional problems, when water-containing ethylene-vinyl alcohol copolymer resin pellets are supplied to an extruder, the amount of water deposited on the surface of the resin pellets is controlled to a predetermined value or less. By doing so, it is an object to provide a method for efficiently supplying the extruder.

[0015]

In order to achieve the above object, the ethylene-vinyl alcohol copolymer of the present invention (EVO
H) The method for producing the resin composition is a method in which the EVOH resin is melt-kneaded in a water-containing state, wherein the water content of the entire resin pellets is in the range of 0.5 to 70% by weight and the water content of the surface water of the pellets is The pellets are supplied to an extruder at a rate of less than 10% by weight.

In the above method, it is preferable to supply the pellets quantitatively to the extruder using a quantitative feeder, since the pellets can be supplied stably.

In the above-mentioned method, it is preferable to melt-knead the additives in a water-containing state, since uniform mixing can be achieved.

In the above method, the resin melting temperature in the extruder is preferably in the range of 70 to 170 ° C.

In the above method, the ethylene content of the ethylene-vinyl alcohol copolymer is preferably in the range of 3 to 70 mol%.

In the above method, the degree of saponification of the ethylene-vinyl alcohol copolymer is from 80 mol% to 100 mol%.
Preferably it is in the range of mol%.

In the above method, it is preferable that the water content of the resin immediately after being discharged from the extruder is 5 to 40% by weight.

In the above method, it is preferable to supply insufficient water or remove excess water in the extruder so that the water content of the resin immediately after being discharged from the extruder is 5 to 40% by weight.

Further, in the above method, at least one additive selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is added to the water-containing molten resin in the extruder. preferable.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing a schematic process chart of an embodiment of the method of the present invention. The hydrous EVOH is supplied from the raw material supply unit 1 of the twin-screw extruder 20. The EVOH containing water and in a molten or semi-molten state is sent forward by the full flight screw unit 2, kneaded by the reverse flight screw unit 3, and excess moisture is desorbed and adjusted in the vent cylinder unit 7. Thereafter, the mixture is sent forward by the full flight screw unit 4, and a predetermined amount of the additive is added from the minor component addition unit 8. Thereafter, the mixture is kneaded by the reverse flight screw unit 5, passes through the full flight screw unit 6, and is discharged from the discharge port 11. Pelletized downstream from the discharge port 11. Reference numeral 9 denotes a temperature sensor for detecting and controlling the temperature of the EVOH. Reference numeral 10 denotes a cylinder barrel.

FIG. 2 is a partially cutaway schematic view of a hopper feeder according to an embodiment used in the method of the present invention. The hopper feeder 30 includes a hopper 31 for storing resin pellets and a lid 32 thereof, a level switch 33 for detecting the amount of resin pellets, a stirring device 34 for preventing resin pellets from bridging, and a screw 37 for rotating screws 37. A motor 36, a barrel 38 of the extruder,
It consists of a gantry 35.

The EVOH used in the present invention is preferably obtained by saponifying an ethylene-vinyl ester copolymer. The ethylene content is 3 to 70 mol%, and from the viewpoint of obtaining a molded article having excellent gas barrier properties and melt moldability, preferably 10 to 60 mol%, more preferably 20 to 55 mol%, Is preferably 25 to 55 mol%. Further, the degree of saponification of the vinyl ester component is 80 mol% or more, and from the viewpoint of obtaining a molded article having excellent gas barrier properties, preferably 95 mol%.
The content is particularly preferably at least 99 mol%.

On the other hand, EV having an ethylene content of 3 to 20 mol%
OH is suitably used as EVOH having water solubility, and such EVOH aqueous solution has excellent barrier properties and coating film moldability, and is used as an excellent coating material.

EVO having a saponification degree of 80 to 95 mol%
H is suitably used for improving melt moldability.
Such EVOH can be used alone, but an embodiment in which EVOH is used by blending with EVOH having a degree of saponification of more than 99 mol% is also suitable.

However, from the viewpoint of the production process, both the EVOH having an ethylene content of 3 to 20 mol% and the EVOH having a saponification degree of 80 to 95 mol% can be used in a conventional manner. It was difficult to extrude and precipitate a methanol solution into a coagulation bath in the form of a strand, it was difficult to produce stable pellets, and it was also difficult to uniformly contain an acidic substance and a metal salt in the pellets. For such EVOH,
The present invention is significant from the viewpoint that stable pellet production has become possible.

If the ethylene content of EVOH is less than 3 mol%, melt moldability is poor, and water resistance, hot water resistance, and gas barrier properties under high humidity may decrease. On the other hand, if it exceeds 70 mol%, the barrier properties, printability and the like will be insufficient.
If the degree of saponification is less than 80 mol%, the barrier properties, coloring resistance and moisture resistance will be unsatisfactory.

Hereinafter, the method for producing EVOH will be specifically described. The polymerization of ethylene and vinyl ester is not limited to solution polymerization, but may be any of solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization. Further, either a continuous type or a batch type may be used. One example of polymerization conditions for batch-type solution polymerization is shown below.

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-methoxy-2,4-
Dimethylvaleronitrile), 2,2-azobis- (2-
Azonitrile initiators such as cyclopropylpropionitrile) and isobutyryl peroxide, cumyl peroxy neodecanoate, diisopropyl peroxy carbonate, di-n-propyl peroxy dicarbonate, t-butyl peroxy neodecanoate And organic peroxide-based initiators such as lauroyl peroxide, benzoyl peroxide and t-butyl hydroperoxide.

Vinyl esters; vinyl acetate and fatty acid vinyl esters (such as vinyl propionate and vinyl pivalate) can also be used. EVOH can contain 0.0002 to 0.2 mol% of a vinylsilane compound as a copolymerization component. Here, examples of the vinylsilane-based compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri (β-methoxy-ethoxy) silane, and γ-methacryloxypropylmethoxysilane. Among them, vinyltrimethoxysilane and vinyltriethoxysilane are preferably used. (1) Temperature: 20 to 90 ° C, preferably 40 to 70 ° C. (2) Time: 2 to 15 hours, preferably 3 to 11 hours. (3) Polymerization rate: 10 to 90 based on the charged vinyl ester
%, Preferably 30-80%. (4) Resin content in the solution after polymerization: 5 to 85%, preferably 20 to 70%. (5) Ethylene content in the copolymer: 3 to 70 mol%. Preferably, it is 10 to 60 mol%, more preferably, 20 to 55 mol%, and most preferably, 25 to 55 mol%. In addition to ethylene and vinyl ester, monomers copolymerizable therewith, such as propylene and isobutylene. , Α
Α-olefins such as octene and α-dodecene; unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid and itaconic acid or anhydrides, salts or mono- or dialkyl esters thereof; acrylonitrile, methacrylonitrile Amides such as acrylamide and methacrylamide; olefinsulfonic acids such as ethylenesulfonic acid, allylsulfonic acid and methallylsulfonic acid or salts thereof; alkyl vinyl ethers, vinyl ketone, N-vinylpyrrolidone, vinyl chloride, and chloride It is also possible to coexist a small amount of vinylidene or the like.

After the polymerization for a predetermined time has reached a predetermined polymerization rate, a polymerization inhibitor is added if necessary, and unreacted ethylene gas is removed by evaporation. 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 top of a tower filled with Raschig rings, A method in which an organic solvent vapor such as methanol is blown from a lower portion, a mixed vapor of an organic solvent such as methanol and an unreacted vinyl ester is distilled off from the top of the tower, and the copolymer solution from which the unreacted vinyl ester is removed is removed from the bottom of the tower. Is adopted.

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 is continuous,
Both batch types are possible. 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. (1) Concentration of the copolymer solution; 10 to 50% (2) Reaction temperature; 30 to 65 ° C (3) Amount of catalyst used; 0.02 to 1.0 equivalent (per vinyl ester component) (4) Time; It is preferable to neutralize the EVOH after the reaction for 1 to 6 hours as necessary.

The present invention relates to a method of melting and kneading EVOH in a water-containing state, wherein the water content of the resin pellets is in the range of 0.5 to 70% by weight and the surface water content of the pellets is 10% by weight. % And supplying the pellets to the extruder.

The shape of the pellets supplied to the extruder is not particularly limited. The pellets obtained by cutting the strands precipitated in the coagulation bath or the resin in the molten state are cut directly. Go stone-shaped pellets or the like can be used. Usually, the former columnar pellet is suitably used.

The lower limit of the water content of the entire EVOH pellets before being charged into the extruder is 0.5% by weight or more. The water content is more preferably 5% by weight or more, and 7% by weight.
More preferably, it is the above. In addition, the upper limit of the water content of the entire EVOH pellet before being charged into the extruder is 70%.
% By weight or less. The water content is preferably at most 60% by weight, more preferably at most 50% by weight. Since the water content of the entire EVOH pellets before being charged into the extruder is in such a range, in the extruder,
EVOH in a molten state can be obtained at a temperature lower than the melting point of EVOH in a dry state.
It is possible to suppress thermal degradation of VOH and to improve extrusion stability.

If the water content of the entire EVOH pellets before being charged into the extruder is less than 0.5% by weight, the effect of suppressing the thermal deterioration of the EVOH in the extruder may be insufficient. When the water content exceeds 70% by weight,
In a resin composition composed of EVOH, there is a possibility that the resin and water contained in the resin are likely to cause phase separation. If the resin and the water contained in the resin undergo phase separation, the resin surface becomes wet and the friction increases, which may easily cause a bridge in the hopper of the extruder. May adversely affect the productivity of the product pellets.

The method for adjusting the water content of EVOH before being charged into the extruder is not particularly limited. To increase the water content, a method of spraying water on the resin, a method of immersing the resin in water, a method of bringing the resin into contact with water vapor, and the like can be mentioned. When reducing the water content, an appropriate drying method may be used, for example, a method of drying using a fluidized hot air dryer or a stationary hot air dryer, but from the viewpoint of reducing drying spots. It is preferable to use a fluidized hot air dryer. Further, from the viewpoint of suppressing thermal deterioration, the drying temperature is preferably 120 ° C. or less.

In the present invention, the moisture content of the surface water of the pellets fed into the extruder is less than 10% by weight. If the water content of the surface water is 10% by weight or more, the surface water separated by the feeder falls into the extruder, generates steam at the lower part of the hopper, and the fusion of the raw material pellets is likely to occur. In particular, the EVOH of the present invention is problematic in that the melting point of the EVOH is low because the resin contains water in many cases, and it is easier to fuse than ordinary dry EVOH. The surface water is preferably not more than 8% by weight.

A columnar pellet obtained by cutting a strand in which an EVOH solution is precipitated in a coagulation bath usually holds a large amount of surface water, but the method of removing surface water from such a pellet is not particularly limited. Not done. In addition to the method using a centrifugal separator, hot water drying can be performed to remove surface water. Above all, the method using a centrifuge is
This is preferable because deterioration and fusion due to heat can be prevented and moisture can be quickly removed.

The EVOH pellets are fed into the extruder from the hopper. At this time, it is preferable to supply a fixed amount of pellets to the extruder using a quantitative feeder from the lower part of the hopper. Specifically, a quantitative feeder using a single screw is preferable. By supplying it quantitatively, the amount of carboxylic acid, metal salt, or the like is stable even when it is added in the extruder, and as a result, a resin having good thermal stability can be obtained.

The resin temperature in the extruder is 70 to 17
Preferably it is 0 ° C. If the resin temperature is lower than 70 ° C., the EVOH may not completely melt. Also,
When at least one selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is added, the effect of improving the dispersibility may be insufficient. It is preferably at least 80 ° C, more preferably at least 90 ° C. The resin temperature is 170 ° C
If it exceeds, the EVOH may be susceptible to thermal degradation. Further, when at least one selected from the group consisting of a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is added as an aqueous solution, when the resin temperature exceeds 170 ° C., evaporation of water becomes severe. Therefore, it may be difficult to mix EVOH and the aqueous solution at a suitable aqueous solution concentration. Preferably 1
It is 50 ° C. or lower, more preferably 130 ° C. or lower.
The method for adjusting the resin temperature is not particularly limited, but a method for suitably setting the temperature of the cylinder in the extruder is particularly preferable.

In the present invention, the resin temperature refers to a temperature detected by a temperature sensor installed in a cylinder of an extruder, and a detection point indicates a temperature near a discharge port at a tip of the extruder.

In the present invention, saponification catalyst residues contained in the production of EVOH can be removed. Specifically, the EVOH resin can be supplied to the extruder, the cleaning liquid can be injected from at least one point of the extruder, the resin can be washed, and the cleaning liquid can be discharged from at least one point downstream of the injection part.

EVOH to be supplied to an extruder in the present invention
Is preferably an alkali metal ion.

The content of alkali metal ions contained in EVOH supplied to the extruder is preferably in the range of 0.1 to 5% by weight in terms of metal. More preferably, 0.2
% By weight or more, more preferably 0.5% by weight or more. It is more preferably at most 4% by weight, further preferably at most 3% by weight. If the content is less than 0.1% by weight, the conventional cleaning method can be used in a sufficiently space-saving manner, and the use of the manufacturing method of the present invention is not effective. On the other hand, when the content exceeds 5% by weight, an extruder having a large L / D is required to sufficiently perform washing, which is not preferable because the cost is increased.

In the present invention, the alkali metal ion contained in the washed EVOH is preferably 0.05% by weight or less in terms of metal. More preferably 0.04
% By weight, more preferably 0.03% by weight or less. If it exceeds 0.05% by weight, the thermal stability of EVOH deteriorates, which is not preferable.

The washing liquid used in the present invention is not particularly limited as long as it can remove the saponification catalyst residue, but it should be an aqueous solution of an acid having a pKa of 3.5 or more at 25 ° C. Is preferred. PKa at 25 ° C
When an aqueous solution of an acid having a pH of less than 3.5 is used, EVOH
May have unsatisfactory coloring resistance and interlayer adhesion. As such an acid having a pKa of 3.5 or more, carboxylic acid is preferable, and acetic acid is particularly preferably used in view of cost and the like. The acetic acid concentration when the acetic acid aqueous solution is used is preferably 0.01 to 10 g / liter, and more preferably 0.1 to 10 g / liter.
1-2 g / liter.

It is preferable that the injection amount of the cleaning liquid is 0.1 to 100 liter per 1 kg of the charged resin.

The injection of the cleaning liquid is not particularly limited as long as it can inject the cleaning liquid into the extruder, and examples thereof include a method of press-in using a plunger pump or the like. The discharge of the cleaning liquid is not particularly limited as long as it is disposed downstream of the injection section and can discharge the liquid from the extruder, but a dehydration slit or a dehydration hole is preferable. Note that a plurality of injection units or a plurality of discharge units may be arranged.

In the present invention, it is also preferable that after the above-mentioned washing is performed, dehydration or degassing of the EVOH in a water-containing state is performed in the extruder. Specifically, it is preferable to discharge at least one selected from liquid water and steam from at least one location of the extruder. The method of discharging here is not particularly limited, but examples include a method of discharging from a dehydrating slit, a dehydrating hole or a vent provided in a cylinder of the extruder.

Of these, a dewatering slit or a dewatering hole is preferred. Since these can discharge either liquid water or water vapor, it is possible to efficiently remove water from a resin having a high water content, and in this regard, generally only water vapor is discharged. It is often more effective than a vent that cannot. In addition, when moisture is discharged using the vent port, the resin tends to adhere to the vent port, and the adhered resin may deteriorate and enter the extruder. Is preferred.

As the vent port, a vacuum vent for removing water vapor under reduced pressure or an open vent for removing water vapor at normal pressure can be used.

When a dewatering hole is used, the molten resin may protrude from the hole, and from that point, it is preferable to use a dewatering slit. Suitable examples of such a dewatering slit include a wedge wire type dewatering slit and a screen mesh type dewatering slit.

The above dehydrating means may be used alone, a plurality of the same type may be used, or different types may be used in combination. For example,
After removing a certain amount of water from the resin having a high water content using a dehydrating slit, it is also possible to further remove water from the vent port downstream of the resin.

The water content of the resin composition comprising EVOH immediately after discharge from the extruder is preferably 5 to 40% by weight.
Particularly preferred is 5 to 35% by weight. When the water content of the resin composition composed of EVOH immediately after discharge from the extruder exceeds 40% by weight, in the resin composition composed of EVOH, the resin and water contained in the resin may easily undergo phase separation, As a result, foaming may easily occur after discharge from the extruder. If the water content of the EVOH resin composition immediately after discharge from the extruder is less than 5% by weight, the effect of suppressing the deterioration of the EVOH due to heating in the extruder may be insufficient, and the resulting EVOH pellets May have unsatisfactory coloring resistance.

After washing in an extruder, dehydration or degassing,
At least one selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt can be added alone, but depending on the embodiment, a carboxylic acid, a boron compound, By adding a plurality of types of compounds selected from a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt in the following suitable ranges, it is possible to improve various performances of the resin composition pellets composed of EVOH. It is.

It is preferable to add a carboxylic acid to the resin composition pellets made of EVOH of the present invention from the viewpoint of improving thermal stability. As the carboxylic acid, 25
It is preferred that the pKa at ℃ is 3.5 or more.
When a carboxylic acid having a pKa at 25 ° C. of less than 3.5 is added, it is difficult to control the pH of the resin composition composed of EVOH, which may result in unsatisfactory coloring resistance and interlayer adhesion. Examples of the carboxylic acid include oxalic acid, succinic acid, benzoic acid, citric acid, acetic acid, lactic acid, and the like, but acetic acid or lactic acid is preferably used in terms of cost and the like.

The content of the carboxylic acid in the pellets of the dry resin composition comprising the EVOH of the present invention is 10 to 5000 p.
pm. Carboxylic acid content of 10
If it is less than ppm, coloring may occur during melt molding, and if it exceeds 5000 ppm, interlayer adhesion may be insufficient. The lower limit of the content of the carboxylic acid is preferably 30 ppm or more, more preferably 50 ppm.
pm or more. The upper limit of the content of the carboxylic acid is preferably 1000 ppm or less, more preferably 50 ppm or less.
It is 0 ppm or less.

From the viewpoint of improving thermal stability, it is preferable to add a phosphoric acid compound to the resin composition pellets comprising the EVOH of the present invention. The content of the phosphoric acid compound in the dried resin composition pellets comprising the EVOH of the present invention is preferably from 1 to 1000 ppm in terms of a phosphate group, and by adding the phosphoric acid compound in an appropriate range, the coloring of the molded product is improved. In addition, it is possible to suppress the generation of gel and butter. The above-mentioned improvement effect by the addition of the phosphoric acid compound is particularly remarkable at the time of long run molding using the resin composition pellets made of EVOH and at the time of collecting the molded product. Examples of the phosphate compound include, but are not limited to, various acids such as phosphoric acid and phosphorous acid, and salts thereof. The phosphate may be contained in any form of a first phosphate, a second phosphate, and a third phosphate, and the cationic species thereof is not particularly limited. And alkaline earth metal salts. Among them, it is preferable to add a phosphate compound in the form of sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate, and dipotassium hydrogen phosphate.

The lower limit of the content of the phosphoric acid compound is preferably 10 ppm or more, more preferably 30 ppm in terms of phosphate radical.
pm or more, and the upper limit is preferably 500 ppm or less,
300 ppm or less is more preferable. By containing the phosphoric acid compound in such a range, it is possible to obtain a resin composition pellet made of EVOH, which is less colored and hardly gels. When the content of the phosphoric acid compound is less than 1 ppm, coloring during melt molding may become intense. In particular,
Since the tendency is remarkable when heat histories are repeated, a molded product obtained by molding the resin composition pellets may have poor recoverability. In addition, when the content of the phosphoric acid compound exceeds 1000 ppm, there is a possibility that gels and buttocks of the molded product are easily generated.

The resin composition pellets comprising the EVOH of the present invention can be used from the viewpoints of improving thermal stability and mechanical properties.
It is preferable to include a boron compound (Japanese Patent Publication No. Sho 4
No. 9-20615). When a boron compound is added to a resin composition composed of EVOH, it is considered that a chelate compound is formed between the EVOH and the boron compound. By using such EVOH, improvement in thermal stability compared with ordinary EVOH, mechanical It is possible to improve the properties.

Examples of the boron compound include, but are not limited to, boric acids, borate esters, borates, and borohydrides. Specifically, examples of boric acids include orthoboric acid, metaboric acid, tetraboric acid, and the like.Examples of borate esters include triethyl borate, trimethyl borate, and the like. Alkali metal salts, alkaline earth metal salts of acids,
Borax and the like. Of these compounds, orthoboric acid (hereinafter simply referred to as boric acid) is preferred.

The content of the boron compound in the pellets of the dry resin composition comprising the EVOH of the present invention is 20 in terms of boron.
2,000 ppm, preferably 50-100
More preferably, it is 0 ppm. If it is less than 10 ppm, the effect of improving the thermal stability by adding a boron compound may not be obtained, and if it exceeds 2,000 ppm, gelation is likely to occur and moldability may be poor.

By adding an alkali metal salt to the resin composition pellets comprising EVOH of the present invention,
It is possible to effectively improve the interlayer adhesion and compatibility. The addition amount of the alkali metal salt in the dried resin composition pellets made of EVOH of the present invention is preferably from 5 to 5000 ppm in terms of an alkali metal element. More preferably 20
To 1000 ppm, more preferably 30 to 750 p
pm. Examples of the alkali metal include lithium, sodium, and potassium, and examples of the alkali metal salt include a monovalent metal aliphatic carboxylate, an aromatic carboxylate, a phosphate, and a metal complex. For example, sodium acetate, potassium acetate, sodium phosphate, lithium phosphate, sodium stearate, potassium stearate,
And sodium salts of ethylenediaminetetraacetic acid. Among them, sodium acetate, potassium acetate and sodium phosphate are preferred.

It is also preferable to add an alkaline earth metal salt to the resin composition pellets comprising the EVOH of the present invention. When the alkaline earth metal salt is added, the effect of improving the color resistance is slightly reduced, but the amount of the thermally degraded resin adhered to the die of the molding machine during the melt molding using the resin composition pellets is further reduced. It is possible. The alkaline earth metal salt is not particularly limited, but examples thereof include a magnesium salt, a calcium salt, a barium salt, and a beryllium salt, and a magnesium salt and a calcium salt are particularly preferable. Although the anion species of the alkaline earth metal salt is not particularly limited, acetate anions and phosphate anions are preferred.

The content of alkaline earth metal in the pellets of the dry resin composition comprising EVOH of the present invention is 1 in terms of metal.
0 to 1000 ppm is preferred, and more preferably 20 to 1000 ppm.
500 ppm. Alkaline earth metal content of 10
If it is less than ppm, the effect of improving long-run properties may be insufficient, and if it exceeds 1000 ppm, coloring during resin melting may become severe.

The carboxylic acids and boron compounds shown above,
When at least one selected from a phosphate compound, an alkali metal salt and an alkaline earth metal salt is contained in a resin composition pellet made of EVOH, EVOH having an ethylene content of 3 to 70 mol% and a saponification degree of 80 mol% or more is used. Carboxylic acid, boron compound, phosphoric acid compound,
At least one selected from an alkali metal salt and an alkaline earth metal salt can be added. At least one selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt in an extruder;
By adding a seed, at least one selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is blended with EVOH, and a carboxylic acid, a boron compound,
At least one selected from a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt can be kneaded with very good uniformity. By adopting such a configuration, the motor torque of the extruder during melt molding and its torque fluctuation are small, the extrusion stability, the coloring resistance and the long run property are excellent, and the generation of gel / bubbles and the amount of die attached are small from EVOH. It is possible to obtain resin composition pellets. In the present invention, when adding at least one selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt to an EVOH in an extruder, the extruder such as the carboxylic acid is added to the extruder. The feed position is preferably added at a position where EVOH is melted in the extruder in that the effect of the present invention is sufficiently exhibited. In particular, EVOH in a hydrated and molten state
It is preferable to add the above-mentioned additives.

The extruder preferably has a kneading section, and it is particularly preferable that the additive is added at the kneading section of the extruder because the additive is easily homogeneously compounded.

Further, as the metal salts other than the above-mentioned alkali metal salts and alkaline earth metal salts, metal salts described in the fourth period of the periodic table can be used.

The form of addition of at least one selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts is not particularly limited. Examples thereof include a method of adding it as a dry powder in an extruder, a method of adding it as a paste impregnated with a solvent, a method of adding it in a state of being suspended in a liquid, and a method of dissolving it in a solvent and adding it as a solution. From the viewpoint of controlling the amount of addition and uniformly dispersing at least one selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts in EVOH, a carboxylic acid, a boron compound, A method in which at least one selected from a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is dissolved in a solvent and added as a solution is particularly preferable. Such a solvent is not particularly limited, but at least one kind of solubility selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt, cost advantages, ease of handling, and work environment. From the viewpoint of safety and the like, water is preferred.

The method of adding at least one selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts to EVOH is not particularly limited. It is preferable to add at least one selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts to the extruder from one or more places.

When at least one selected from the group consisting of a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is added to EVOH as a solution, the amount of EVOH is preferably 100 parts by weight based on the dry weight of EVOH. hand,
The lower limit of the amount of the solution added is preferably 1 part by weight or more, more preferably 3 parts by weight or more, and particularly preferably 5 parts by weight or more. The upper limit of the amount of the solution is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and more preferably 20 parts by weight or less based on 100 parts by weight of the dry weight of EVOH. Particularly preferred. When the addition amount of the solution is less than 1 part by weight, the concentration of the solution generally increases, so that at least one addition selected from carboxylic acid, boron compound, phosphoric acid compound, alkali metal salt and alkaline earth metal salt is performed. The effect of improving the dispersibility may be reduced. If the amount exceeds 50 parts by weight, it may be difficult to control the water content of the EVOH, and the resin and the water contained in the resin may easily undergo phase separation in the resin composition comprising the EVOH in the extruder. There is.

In the conventional treatment method in which EVOH is impregnated with a solution of an acidic substance and / or a metal salt, it is difficult to obtain a good quality product of the above-described crumb-like precipitate of EVOH. According to the present invention, it is possible to uniformly add at least one selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt even in such a form of EVOH, and to obtain a stable quality. It is possible to obtain a resin composition pellet made of EVOH.

The method for pelletizing the resin composition comprising EVOH discharged from the extruder is not particularly limited.
An example is a method in which the resin composition is extruded from a die into a strand in a coagulation bath and cut into an appropriate length. From the viewpoint of easy handling of the pellet, the diameter of the die is preferably 2 to 5 mmφ (φ is the diameter; the same applies hereinafter), and the strand is preferably cut to a length of about 1 to 5 mm.

The obtained pellet is usually subjected to a drying step. The moisture content of the resin composition pellets made of EVOH after drying is 1% by weight or less, preferably 0.5% by weight or less. The drying method is not particularly limited, but a stationary drying method, a fluidized drying method and the like are mentioned as preferable examples,
It is also possible to employ a multi-stage drying process in which several drying methods are combined. Among them, a method in which drying is performed by a fluidized drying method first, and then drying by a static drying method is preferable.

In the case of the conventional treatment method in which EVOH pellets are immersed in a treatment solution containing an acidic substance and / or a metal salt, the water content of the treated EVOH is usually about 40 to 70% by weight. However, the EVOH of the present invention is melted in an extruder and, if necessary, washed in the extruder, dehydrated or degassed, and then a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt are used. In the case of the treatment method of adding at least one selected from among the following, the water content of the resin composition composed of EVOH immediately after discharge from the extruder can be arbitrarily adjusted, and the water content immediately after discharge from the extruder is preferably 5 ４０40% by weight. Therefore, it is possible to obtain pellets having a smaller moisture content than the conventional method. Such pellets having a small moisture content are preferable from the viewpoint that the energy consumption in the drying process can be reduced.

In particular, pellets having a water content of more than 40% by weight may cause fusion of the pellets when the drying temperature is set to 100 ° C. or higher. From this viewpoint, EVOH pellets having a low moisture content as described above can be obtained.
Is melted in an extruder, washed in the extruder, dehydrated or degassed, and then the present invention comprises adding at least one selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts. Is preferred.

It is also possible to blend EVOH with different degrees of polymerization, ethylene content and saponification degree into resin composition pellets made of EVOH obtained by the above method and melt-mold. Further, other various plasticizers, stabilizers, surfactants, coloring agents, ultraviolet absorbers in the resin composition pellets,
It is also possible to add an appropriate amount of an antistatic agent, a drying agent, a crosslinking agent, a metal salt, a filler, a reinforcing agent such as various fibers, and the like. The resin composition pellets comprising the EVOH of the present invention have a small motor torque of an extruder and a small fluctuation in the torque, and are excellent in extrusion stability. Therefore, depending on the embodiment, the amount of the lubricant used can be significantly reduced, or the lubricant can be used. It is particularly preferred in that it can not be used. However, the use of a lubricant when molding a molded article using the pellets is optional,
Not restricted.

It is also possible to mix a suitable amount of a thermoplastic resin other than EVOH as long as the object of the present invention is 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, copolymer of polyolefin and maleic anhydride,
Ethylene-vinyl ester copolymers, ethylene-acrylate ester copolymers, or modified polyolefins obtained by graft-modifying these with unsaturated carboxylic acids or derivatives thereof, and various nylons (nylon-6, nylon-
6,6, nylon-6 / 6,6 copolymer), polyvinyl chloride, polyvinylidene chloride, polyester, polystyrene, polyacrylonitrile, polyurethane, polyacetal, and modified polyvinyl alcohol resin.

The obtained resin composition pellets comprising the EVOH of the present invention are formed into various molded articles such as films, sheets, containers, pipes, fibers and the like by melt molding. These molded products can be crushed and molded again for the purpose of reuse. It is also possible to uniaxially or biaxially stretch films, sheets, fibers and the like. Examples of the melt molding method include extrusion molding, inflation extrusion, blow molding, melt spinning, and injection molding. The melting temperature varies depending on the melting point of the copolymer and the like, but is preferably about 150 to 270 ° C.

The resin composition pellets comprising the EVOH of the present invention may be formed by molding at least a molded product such as a film or sheet of the composition of the present invention, in addition to the production of a resin molded product having only the resin composition as a single layer as described above. It is often used practically as a multilayer structure having one layer. As the layer constitution of the multilayer structure, E represents a resin composition comprising EVOH of the present invention, Ad represents an adhesive resin, and T represents a thermoplastic resin.
E / Ad / T, T / Ad / E / Ad / T, and the like, but are not limited thereto. Each layer may be a single layer or may be a multilayer in some cases.

As the thermoplastic resin used, linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, polypropylene, propylene-α -Olefin copolymer (carbon number 4
Α-olefins), polybutene, polypentene and other olefins alone or copolymers thereof, polyesters such as polyethylene terephthalate, polyester elastomers, polyamide resins such as nylon-6, nylon-6,6, polystyrene, polyvinyl chloride , Polyvinylidene chloride, acrylic resin, vinyl ester resin, polyurethane elastomer, polycarbonate, chlorinated polyethylene, chlorinated polypropylene and the like.
Among them, polypropylene, polyethylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyamide, polystyrene, and polyester are preferably used.

In laminating the EVOH and the thermoplastic resin, an adhesive resin may be used, and in this case, an adhesive resin composed of a carboxylic acid-modified polyolefin is preferable. The carboxylic acid-modified polyolefin is a modified olefin polymer containing a carboxyl group obtained by chemically (eg, by addition reaction or graft reaction) bonding an ethylenically unsaturated carboxylic acid or an anhydride thereof to an olefin polymer. It is suitable. Here, the olefin polymer refers to polyethylene (low pressure, medium pressure, high pressure), linear low density polyethylene, polypropylene, polyolefin such as boribene, a comonomer (vinyl ester, vinyl ester,
And unsaturated carboxylic acid esters, etc.), for example, ethylene-vinyl acetate copolymer, ethylene-acrylic acid ethyl ester copolymer and the like. Among them, linear low-density polyethylene, ethylene-vinyl acetate copolymer (vinyl acetate content of 5 to 55% by weight), ethylene-
Ethyl acrylate copolymer (content of ethyl acrylate of 8 to 35% by weight) is preferred, and linear low density polyethylene and ethylene-vinyl acetate copolymer are particularly preferred. Ethylenically unsaturated carboxylic acids or anhydrides include ethylenically unsaturated monocarboxylic acids, esters thereof, ethylenically unsaturated dicarboxylic acids, mono or diesters thereof, and anhydrides thereof, and among them, ethylenically unsaturated dicarboxylic acids Anhydrides are preferred. Specific examples include maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride, monomethyl maleate, monoethyl maleate, diethyl maleate, monomethyl fumarate, among others, maleic anhydride Acids are preferred.

The amount of addition or grafting (degree of modification) of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer is 0.01 to 15 with respect to the olefin polymer.
%, Preferably 0.02 to 10% by weight. The addition reaction and graft reaction of the ethylenically unsaturated carboxylic acid or its anhydride to the olefin polymer can be obtained by, for example, a radical polymerization method in the presence of a solvent (such as xylene) and a catalyst (such as peroxide). ASTM-D12 of the carboxylic acid-modified polyolefin thus obtained
The melt index (MI) measured at 190 ° C. by D-1238-65T according to No. 38 is 0.2 to 30 g /
It is preferably 10 minutes, more preferably 0.5 to
10 g / 10 min. These adhesive resins may be used alone or as a mixture of two or more layers.

In the present invention, the above-mentioned multilayer structure can be used as it is in various shapes. However, in order to improve the physical properties of the multilayer structure, it is preferable to carry out a stretching treatment. A stretched film, a stretched sheet, or the like free from stretching unevenness and delamination can be obtained.

The stretching may be either uniaxial stretching or biaxial stretching, and it is better to perform stretching at as high a magnification as possible in terms of physical properties. In the present invention, a stretched film or a stretched sheet free from pinholes, cracks, stretch unevenness, delamination and the like during stretching can be 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.

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. The obtained stretched film can be subjected to a cooling treatment, a printing treatment, a dry lamination treatment, a solution or melt coating treatment, a bag making process, a box process, a tube process, a split process, and the like, if necessary.

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, rolling, printing, dry laminating, solution or melt coating, bag making, deep drawing, 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.

In producing the above-mentioned multilayer structure, another substrate is laminated on one or both sides of a layer of a molded product such as a film or a sheet obtained from the resin composition comprising EVOH of the present invention. However, as a laminating method, for example, a method of melt-extruding a thermoplastic resin on the molded product (film, sheet, etc.), and conversely, a method of laminating the resin composition and another thermoplastic resin on a base material such as a thermoplastic resin. , A method of co-injecting a resin composition comprising a thermoplastic resin and EVOH, and a method wherein a molded product obtained from the resin composition comprising EVOH and a film or sheet of another base material are combined with an organic titanium compound. , Isocyanate compound, a method of laminating using a known adhesive such as a polyester-based compound, and the like. Among them, a method of co-extrusion with another thermoplastic resin is preferable. It is needed. The resin composition comprising the EVOH of the present invention is very excellent in interlayer adhesion, and thus is suitable for a resin composition for coextrusion molding and a coextruded multilayer structure using the same.

The method of coextrusion of the composition of the present invention with a thermoplastic resin may be any of a multi-manifold merging T-die method, a feed block merging T-die method, and an inflation method.

By subjecting the co-extruded multilayer structure thus obtained to secondary processing, various molded products (films, sheets, tubes, bottles, etc.) can be obtained. Can be (1) Multi-layer co-stretched sheet or film by uniaxially or biaxially stretching or biaxially stretching or heat-treating a multi-layered structure (sheet or film) (2) Multi-layered structure (sheet or film) (3) Multi-layered structure (sheet or film, etc.) Multi-layer tray cup-shaped container formed by vacuum forming, air-pressure forming, vacuum-pressure forming, etc. (4) Multi-layered structure Bottles and cup-shaped containers obtained by stretch blow molding from pipes (such as pipes). Such secondary processing methods are not particularly limited, and known secondary processing methods (such as blow molding) other than those described above can also be employed.

The co-extruded multilayer structure and the co-injected multilayer structure thus obtained have less occurrence of gel and butter and less occurrence of fish eyes and streaks during film forming. For example, it is suitably used as a material for deep drawing containers, cup-shaped containers, bottles and the like.

[0098]

EXAMPLES Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. Hereinafter, “%” and “parts” are based on weight unless otherwise specified. In addition, all the water used ion-exchange water. (1) Moisture content of surface water The above-mentioned EVOH pellets were used with an upper discharge centrifuge H-130M manufactured by Domestic Centrifuge Co., Ltd. having the following specifications. EV
10 kg of the OH pellet was subjected to a centrifugal separator having the following specifications for 5 minutes. From the weight change of the EVOH before and after the centrifugation, the moisture content of the surface water of the EVOH was determined using the following equation (Equation 1). <Specification of centrifuge> Model: H-130M Name: Upper discharge type centrifuge Capacity: 107 L (diameter 914 mm x depth 430 mm) Material: SUS304 Number of revolutions: 1000 rpm (510 G) <Moisture percentage of surface water>

(Equation 1) Moisture percentage of surface water (% by weight) = (weight before centrifugation−weight after centrifugation) / weight before centrifugation × 100 (2) Measurement of water content 20 g of water-containing EVOH as a sample In a well-dried weighing bin, and dried at 120 ° C. for 24 hours with a hot air drier. From the change in weight of EVOH before and after drying, the following formula (Equation 2) is obtained.
Was used to determine the water content of EVOH.

(Equation 2) Moisture content (% by weight) = (weight before drying−weight after drying) / weight before drying × 100 (4) Quantification of added trace components Quantification was performed according to the following method. In addition, the following "dry pellet" refers to E added with at least one selected from carboxylic acid, boron compound, phosphoric acid compound, alkali metal salt and alkaline earth metal salt in an extruder.
It is obtained by drying a resin composition pellet made of VOH at 100 ° C. for 15 hours using a fluidized hot air dryer and subsequently drying at 100 ° C. for 15 hours using a stationary hot air dryer. . (2-a) Quantification of Carboxylic Acid Content 20 g of dry pellets as a sample were put in 100 m of ion-exchanged water.
and extracted by heating at 95 ° C. for 6 hours. 1 / 50N Na using phenolphthalein as an indicator
Neutralization titration was performed with OH to determine the carboxylic acid content. (2-b) Determination of Alkali Metal Ion and Alkaline Earth Metal Ion 10 g of a dry pellet 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. The column is ICS-C25 manufactured by Yokogawa Electric Corporation.
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 each metal chloride aqueous solution was used. Thus, the amount of the alkali metal salt and the amount of the alkaline earth metal in the dried pellets were obtained in terms of metal. (2-c) Determination of Boron Compound An aqueous solution of Na ₂ CO ₃ was added to a pellet as a sample, and the pellet was incinerated at 600 ° C. in a platinum crucible. Hydrochloric acid was added to the obtained sample to dissolve it, and the content of the boron compound was quantified in terms of boron by ICP emission spectroscopy. (2-d) Determination of Phosphate Ion 10 g of a dry pellet 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 to determine the amount of phosphate ions. Column, Inc.
Use ICS-A23 manufactured by Yokogawa Electric Corp.
An aqueous solution containing mM mM sodium carbonate and 1.0 mM sodium hydrogen carbonate was used. In the determination, a calibration curve prepared with a phosphoric acid aqueous solution was used. From the amount of the phosphate ions thus obtained, the content of the phosphorus compound was obtained in terms of phosphate groups. (3) Continuous raw material supply test A continuous raw material supply test was performed using the following capacity type feeder shown in FIG. The continuous test was performed for 8 hours, and the time from the start of the test to the occurrence of poor extrusion was measured. <Quantitative single-axis feeder> Specifications: SVF-25 manufactured by Japan Steel Works, Ltd. Throughput: 10 kg / hr (capacity: 4 to 20 kg / hr) Hopper:
30 L drive: 0.4 KW (3) Melt index (MI) Measured under the conditions of temperature 190 ° C. and load 2160 g using a melt indexer according to ASTM-D1238. (4) Single-layer film-forming test A single-layer film of a resin composition comprising EVOH was formed using an extruder having the following specifications, and a film-forming sample of a resin composition pellet comprising EVOH was prepared. The coloring was evaluated.

The specifications of the extruder are as follows.

Extruder GT-40-A Model manufactured by Plastic Engineering Laboratory Co., Ltd. Model Single screw extruder (non-vented type) L / D 26 CR 3.5 Caliber 40mmφ Screw Single full flight type, surface nitrided steel Revolution 40rpm Driving machine Sumitomo Heavy Industries, Ltd. DC motor SCR-DC218B Motor capacity DC7.5KW (Rated 45A) Heater 4-split type Die width 300mm Die resin temperature 240 ° C Picking speed 10m / min. (4-b) Gel / Bull A single-layer film formation of EVOH was carried out using the dried pellets as a sample, and the gel-like bump of the film 1 hour after the start of film formation.
(Approximately 100 μm or more that can be confirmed with the naked eye)
It was converted to around 1.0 m ² . Judgment was made as follows based on the number of spots. A: less than 20 B: 20 to 40 C: 40 to 60 D: 60 or more (4-c) Coloring Single-layer film formation of EVOH was performed using dried pellets as samples, and from the start of film formation. One hour later, the film was wound around a paper tube, and the degree of coloring on the end face of the film was visually determined and determined as follows. A: No coloring B: Slightly yellowing C: Yellowing D: Intense coloring

[0103]

Example 1 A 45% methanol solution of an ethylene-vinyl acetate copolymer having an ethylene content of 32 mol% was charged into a saponification reactor, and a sodium hydroxide / methanol solution (80 g /
L) was added so as to be 0.4 equivalent to the vinyl acetate component in the copolymer, 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 4 hours, the reaction was stopped by neutralization with acetic acid, and water corresponding to 55% by weight of the total amount of methanol in the reactor was added.
EV with an ethylene content of 32 mol% and a saponification degree of 99.5%
A solution of OH in methanol and water was obtained. The EVOH solution was extruded from a metal plate having a circular opening into water to precipitate a strand, and cut to obtain a pellet having a diameter of about 3 mm and a length of about 5 mm. The operation of adding a large amount of water to the obtained pellets and removing the liquid was repeated. Surface water was removed from 10 kg of the dewatered pellet using a centrifuge. The surface moisture content of the obtained pellets was 0% by weight.

EVOH having ethylene of 32 mol%, a saponification degree of 99.5 mol%, and a water content of 33% by weight was charged into the twin-screw extruder shown in FIG. 1, and the resin temperature at the discharge port was set to 100 ° C.
A treatment solution consisting of acetic acid / boric acid / sodium acetate / magnesium acetate / potassium dihydrogen phosphate aqueous solution was added from the trace component addition section (8) shown in FIG. The input amount of EVOH per unit time is 10 kg / h
r (including the weight of the contained water), the amount of the processing solution charged per unit time is 0.67 L / hr, the composition of the processing solution is 4.3 g / L of acetic acid, 15 g / L of boric acid, 4.6 g / L of sodium acetate and 3.0 g / L of magnesium acetate
L, an aqueous solution containing 1.4 g / L of potassium dihydrogen phosphate. The specifications of the twin screw extruder are shown below. As a result of the raw material supply continuous test, no defective extrusion was observed after 8 hours of continuous operation. <Raw material feeder> Capacity type single screw feeder Processing amount: 10 kg / hr (capacity: 4 to 20 kg / hr) Hopper: 30 L, drive: 0.4 KW <Extruder> Type Twin screw extruder L / D 45.5 Diameter 30mmφ Screw Same direction complete meshing type Number of rotations 300rpm Motor capacity DC22KW Heater 13 division type Number of dice holes 5 holes (3mmφ) Resin temperature in die 105 ° C Pickup speed 5m / min Resin composition pellets made of EVOH after extruder discharge Had a water content of 20% by weight. The obtained pellets were dried at 100 ° C. for 15 hours using a fluidized drier, and subsequently dried at 100 ° C. for 15 hours using a stationary drier.
The water content was 0.3% by weight. MI is 1.5g
/ 10 min.

Using the obtained dried pellets, a single-layer film formation of EVOH was carried out, and gel / bubble and coloring tests were carried out.

As a result of the single-layer film formation under the above conditions, the gel and spot test and the color fastness test were all A.

Also, there is no occurrence of bridges in the hopper of the feeder, and the raw material resin can be stably supplied to the extruder.
Since the surface moisture content of the pellets is small, no water vapor is generated in the lower part of the hopper, no fusion of the raw material pellets occurs, and the supply of the raw material pellets to the extruder is stable.
The addition amounts of metal salts and the like were stable, and the thermal stability did not decrease. Table 1 shows the conditions at the time of extrusion, Table 2 shows the composition of the treatment liquid, and Table 3 shows the evaluation results.

[0108]

Example 2 The ethylene content of EVOH, the degree of saponification, the resin temperature in the extruder, the water content before feeding into the extruder and the water content immediately after discharging from the extruder were changed as shown in Table 1,
Table 2 shows the charged amount per unit time of EVOH and the charged amount and composition per unit time of at least one solution selected from carboxylic acids, boron compounds, phosphoric acid compounds, alkali metal salts and alkaline earth metal salts. An EVOH pellet was prepared in the same manner as in Example 1 except for the above changes. Table 1 shows the conditions at the time of extrusion and Table 2 shows the composition of the processing solution.
Table 3 shows the evaluation results.

Further, there is no generation of bridges in the hopper of the feeder, and the raw material resin can be stably supplied to the extruder.
Since the surface moisture content of the pellets is small, no water vapor is generated in the lower part of the hopper, no fusion of the raw material pellets occurs, and the supply of the raw material pellets to the extruder is stable.
The addition amounts of metal salts and the like were stable, and the thermal stability did not decrease.

[0110]

Comparative Example 1 A 45% methanol solution of an ethylene-vinyl acetate copolymer having an ethylene content of 32 mol% was charged into a saponification reactor, and a sodium hydroxide / methanol solution (80 g /
L) was added so as to be 0.4 equivalent to the vinyl acetate component in the copolymer, 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 4 hours, the reaction was stopped by neutralization with acetic acid, and water corresponding to 55% by weight of the total amount of methanol in the reactor was added.
EV with an ethylene content of 32 mol% and a saponification degree of 99.5%
A solution of OH in methanol and water was obtained. The EVOH solution was extruded from a metal plate having a circular opening into water to precipitate a strand, and cut to obtain a pellet having a diameter of about 3 mm and a length of about 5 mm. The operation of removing the obtained pellets, adding a large amount of water, and removing the liquid was repeated. The surface water content of the obtained pellets was 30% by weight, and the water content was 65% by weight.

As a result of a continuous raw material supply test of the obtained pellets, after 0.5 hour, a bridge was generated at the lower part of the hopper,
The operation was stopped. In addition, the obtained pellets were formed into a film,
The gel and butter occurred frequently, the coloring was severe, and the appearance was extremely poor. Table 1 shows the conditions at the time of extrusion and Table 2 shows the composition of the processing solution.
Table 3 shows the evaluation results.

[0112]

[Table 1]

[0113]

[Table 2]

[0114]

[Table 3] As described above, according to the present invention, the following advantages can be obtained. (1) The occurrence of bridges in the hopper of the feeder is prevented, and the raw material resin can be stably supplied to the extruder. (2) Since the surface moisture content of the pellets is small, no water vapor is generated at the lower part of the hopper, and no fusion of the raw material pellets occurs. (3) Since the supply of the raw material pellets to the extruder is stable, the amount of the acid or metal salt added is stable, and the thermal stability does not decrease.

[0115]

As described above, the method for producing the ethylene-vinyl alcohol copolymer (EVOH) resin composition of the present invention is a method in which an EVOH resin is melt-kneaded in a water-containing state. Of 0.5 to 70
Wt% and the moisture content of the surface water of the pellets is 10
By supplying the pellets to the extruder at less than% by weight, the pellets can be efficiently supplied to the extruder.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a schematic process chart of an embodiment of the method of the present invention.

FIG. 2 is a partially cutaway schematic view of a hopper feeder of one embodiment used in the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Raw material supply part 2,4,6 Full flight screw part 3,5 Reverse flight screw part 7 Vent cylinder part 8 Trace component addition part 9 Temperature sensor 10 Cylinder barrel 11 Discharge port 20 Twin screw extruder 30 Hopper feeder 31 Hopper 32 Lid 33 Level switch 34 Stirrer 35 Mount 36 Motor 37 Screw 38 Barrel

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F070 AA13 AA26 AB01 AB13 AC12 AE02 FA03 FC05 4F201 AA04E AA19E AB00 AB16 AB19 AR06 AR20 BA01 BC01 BC12 BC33 BK02 BK13 BK26 BQ16 BQ54 4F207 AA04E AA19E AB00 AR16 AB01 KB02 BB221 DE026 DH027 DH047 DK007 EF037 EF097 EG027 EG037 EY007

Claims (9)

[Claims] 1. A method for melt-kneading an ethylene-vinyl alcohol copolymer resin in a water-containing state, wherein the water content of the resin pellets is in the range of 0.5 to 70% by weight and the surface water of the pellets is A method for producing an ethylene-vinyl alcohol copolymer resin composition, wherein the pellets are supplied to an extruder with a water content of less than 10% by weight. 2. The method for producing an ethylene-vinyl alcohol copolymer resin composition according to claim 1, wherein the method for supplying the pellets is a method for quantitatively supplying the pellets to an extruder using a quantitative feeder. 3. The method for producing an ethylene-vinyl alcohol copolymer resin composition according to claim 1, wherein the additive is melt-kneaded in a water-containing state. 4. The resin melting temperature in the extruder is 70 to 170.
The method for producing an ethylene-vinyl alcohol copolymer resin composition according to any one of claims 1 to 3, which is in the range of ° C. 5. The ethylene-vinyl alcohol copolymer according to claim 1, wherein the ethylene content is in the range of 3 to 70 mol%.
5. The method for producing an ethylene-vinyl alcohol copolymer resin composition according to any one of items 1 to 4. 6. The ethylene-vinyl alcohol copolymer resin composition according to claim 1, wherein the degree of saponification of the ethylene-vinyl alcohol copolymer ranges from 80 mol% to 100 mol%. Production method. 7. The method for producing an ethylene-vinyl alcohol copolymer resin composition according to claim 1, wherein the water content of the resin immediately after being discharged from the extruder is 5 to 40% by weight. 8. The ethylene-vinyl according to claim 7, wherein the insufficient water is supplied or excess water is removed in the extruder so that the water content of the resin immediately after being discharged from the extruder is 5 to 40% by weight. A method for producing an alcohol copolymer resin composition. 9. The extruder according to claim 1, wherein at least one additive selected from a carboxylic acid, a boron compound, a phosphoric acid compound, an alkali metal salt and an alkaline earth metal salt is added to the hydrated molten resin. A method for producing the ethylene-vinyl alcohol copolymer resin composition according to any one of the above.