JP2001081197A - Drying of saponified ethylene-vinyl acetate copolymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dry a saponified ethylene-vinyl acetate copolymer in high drying efficiency while suppressing the coloring (yellowing) of the copolymer and obtain a dried material useful for foods, pharmaceuticals, etc., by melting and kneading the saponified copolymer having a specific water content. SOLUTION: A saponified ethylene-vinyl acetate copolymer (EVOH) having a water-content of 5-60 wt.% is melted and kneaded to decrease the water content to <5 wt.% The melting and kneading process is preferably carried out by using an extruder under a condition to satisfy the formula 1<=T0/T1<10 (T1 is the cylinder temperature of the extruder at the inlet part of hopper; T0 is the cylinder temperature at the outlet part) or the formula 1<=TM/TF<10 (TF is the feeding zone temperature of the extruder; TM is the metering zone temperature) and the EVOH preferably has an ethylene content of 5-70 mol% and the saponification degree of the vinyl acetate unit of >=85 mol%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for drying a saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH).

[0002]

2. Description of the Related Art Heretofore, EVOH has been widely used in various packaging applications, etc. by making use of characteristics such as transparency, antistatic property, oil resistance, solvent resistance, gas barrier property, and fragrance retention property. In the production of EVOH, usually, a copolymer of ethylene and vinyl acetate is saponified in a solution such as alcohol, and then extruded into a coagulation bath in a strand shape and cut (pelletized). After being subjected to a washing treatment or the like to form water-containing pellets, they are generally dried to obtain a pellet-shaped product.

However, when such drying is insufficient, E
When VOH (pellet) is melt-molded by an extruder or the like, foaming or the like occurs, and a molded article having good appearance and performance cannot be obtained, and drying of such EVOH (pellet) is very important. At present, such drying is usually performed using hot air having a high temperature of about 100 ° C. for more than ten hours (Japanese Patent Application Laid-Open No. 53-119958).

[0004]

However, in the method using hot air described above, EVOH may be colored (yellowed) or the commercial value may be reduced, and the drying efficiency requires long time treatment. Therefore, the method is not always efficient, and a new improvement in a method for drying water-containing EVOH is desired.

[0005]

The inventor of the present invention has conducted intensive studies in view of such circumstances, and as a result, has found that the water content is 5 to 60%.
The present inventors have found that the above-mentioned problems can be solved by melting and kneading EVOH in an amount of 5% by weight to make the water content less than 5% by weight, and have completed the present invention.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The EVOH used in the present invention is not particularly limited, but has an ethylene content of 5 to 70 mol%, preferably 2 to 70 mol%.
0 to 60 mol%, more preferably 25 to 55 mol%, and a vinyl acetate component having a saponification degree of 85 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more, is used. If less than 5 mol%, the water resistance becomes insufficient, while if more than 70 mol%, the gas barrier properties decrease, which is not preferable. On the other hand, when the saponification degree is less than 85 mol%, the water resistance becomes insufficient, which is not preferable.

Further, the intrinsic viscosity of EVOH (phenol 85
(Measured value at 30 ° C. in a mixed solvent of 15% by weight of water and 15% by weight of water) is 0.6 to 1.5 dl / g, preferably 0.7 to 1.5 dl / g.
1.3 dl / g, more preferably 0.8 to 1.2 dl /
g, and those having a viscosity of less than 0.6 dl / g or more than 1.5 dl / g are not preferred because the extrusion moldability may be unstable. The EVOH is obtained by saponification of an ethylene-vinyl acetate copolymer, and the ethylene-vinyl acetate copolymer can be obtained by any known polymerization method,
For example, it is produced by solution polymerization, suspension polymerization, emulsion polymerization, or the like, and saponification of an ethylene-vinyl acetate copolymer can be performed by a known method.

In the present invention, a copolymerizable ethylenically unsaturated monomer may be copolymerized as long as the effects of the present invention are not impaired. Examples of such a monomer include propylene and 1-butene. , Olefins such as isobutene, acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid,
Unsaturated acids such as (anhydride) maleic acid and (anhydride) itaconic acid or salts thereof, mono- or dialkyl esters having 1 to 18 carbon atoms, acrylamide, 1 to 1 carbon atoms
8, acrylamides such as N-alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof, methacrylamide, having 1 to 18 carbon atoms Methacrylamides such as N-alkyl methacrylamide, N, N-dimethyl methacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof, N-vinylpyrrolidone N-vinylamides such as, N-vinylformamide and N-vinylacetamide;
Vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl ethers such as alkyl vinyl ethers having 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers and alkoxyalkyl vinyl ethers; vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride and vinyl bromide And vinylsilanes such as trimethoxyvinylsilane, allyl acetate, allyl chloride, allyl alcohol, dimethylallyl alcohol, trimethyl- (3-acrylamido-3-dimethylpropyl)-
Examples thereof include ammonium chloride and acrylamide-2-methylpropanesulfonic acid. Further, post-modification such as urethanization, acetalization, and cyanoethylation may be performed as long as the gist of the present invention is not impaired.

In the present invention, the EVOH as described above is dried by melt-kneading.
It is necessary to use EVOH having a water content of 5 to 60% by weight, and pellets are particularly preferable in terms of easy handling. To obtain such EVOH pellets, there is no particular limitation. It is extruded into a strand and solidified, then cut into pellets, and then washed with water.
During these steps, the moisture content of the EVOH pellets was reduced to 5%.
~ 60% by weight (further 10 ~ 50% by weight, especially 10 ~ 10% by weight
(40% by weight). When the water content is less than 5% by weight, the effect of the drying method of the present invention cannot be sufficiently exerted. On the other hand, when the water content exceeds 60% by weight, a partial separation of the resin and water during the drying treatment (melt kneading) occurs. As a result, the drying treatment becomes unstable and the object of the present invention cannot be achieved. Here, the water content of EVOH before the drying treatment is measured and calculated by the following method.

[Measurement Method of Moisture Content] After weighing EVOH with an electronic balance (W 1: unit g), it is placed in a hot-air oven type drier maintained at 150 ° C., dried for 5 hours, and further placed in a desiccator. The weight after allowing to cool for 30 minutes is similarly weighed (W2: unit g) and calculated from the following equation (3). Water content (%) = {(W1−W2) / W1} × 100 (3)

Hereinafter, the method for obtaining the hydrous EVOH pellets used in the present invention will be described in detail. EVOH used in the present invention is obtained by saponifying an ethylene-vinyl acetate copolymer as described above. Such a saponification reaction is carried out in the presence of an alkali catalyst. A conventionally known catalyst used for a saponification reaction of vinyl or an ethylene-vinyl acetate copolymer with an alkali catalyst can be used as it is. Specifically, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide; alkali metal alcoholates such as sodium methylate and potassium t-butoxy;
-Diazabicyclo [5,4,10] undecene-7 (D
Examples thereof include cobasic amines represented by BU), and alkali metal carbonates and alkali metal hydrogencarbonates. Of these, use of sodium hydroxide is preferred in terms of ease of handling, catalyst cost, and the like. The amount of catalyst used is the required degree of saponification,
Although it depends on the reaction temperature and the like, 0.05 equivalent or less, preferably 0.03 equivalent or less, based on the residual acetic acid groups in the ethylene-vinyl acetate copolymer is used. Further, instead of the alkali catalyst, an acid catalyst such as hydrochloric acid and sulfuric acid can be used.

In the saponification, the ethylene-vinyl acetate copolymer is dissolved in an alcohol or an alcohol-containing medium to a concentration of usually about 20 to 60% by weight, and an alkali catalyst or an acid catalyst is added. 40-1
React at a temperature of 40 ° C. If care is taken not to precipitate the EVOH after the reaction at the solution temperature, the EVOH
Although there is no particular limitation on the concentration of
The content may be 5% by weight, preferably 15 to 50% by weight.

Next, the alcohol solution of EVOH obtained above may be used as it is, but preferably, water is added directly, or the EVOH solution is appropriately concentrated or diluted, and then water is added to obtain a solution for strand production. Adjusted. In the case of the aqueous solution, the mixing weight ratio of water / alcohol is 80/2.
0-5 / 95 and the content A (% by weight) of the alcohol is 2.55E-40.75 ≦ A ≦ 2.55E-
It is preferable to satisfy the relationship of 15.75 (where E is the ethylene content (mol%) of EVOH) from the viewpoint of the stability of the solution, and the amount of EVOH contained in the solution is 20 -55% by weight (furthermore, 25-50% by weight) is preferred in terms of the stability of the subsequent solidification operation.

Next, the EVOH solution obtained above is extruded into a strand and pelletized. At this time, a saturated aliphatic amide (eg, stearic acid amide) or an unsaturated fatty acid amide (eg, oleic acid) is used. Amides), bisfatty acid amides (e.g., ethylene bisstearic acid amide, etc.), fatty acid metal salts (e.g., calcium stearate, etc.), low molecular weight polyolefins (e.g.,
Lubricants such as low molecular weight polyethylene of about 10,000 or low molecular weight polypropylene, etc.), inorganic acids (for example, phosphoric acid, boric acid, etc.), organic acids (acetic acid, stearic acid, etc.),
Inorganic salts (eg, alkali metal / alkaline earth metal salts of phosphoric acid, hydrotalcite, etc.), organic acids (eg, alkali metal / alkaline earth metal salts of acetic acid, etc.), plasticizers (eg, ethylene glycol, glycerin, hexanediol) And antioxidants (for example, IRGANOX10 manufactured by Ciba Specialty Chemicals)
98, etc.), an ultraviolet absorber, a coloring agent, an antibacterial agent, an antiblocking agent (eg, talc fine particles), a slip agent (eg, amorphous silica fine particles), and the like.

Examples of the coagulating liquid to be precipitated include water or a mixed solvent of water / alcohol, aromatic hydrocarbons such as benzene, ketones such as acetone and methyl ethyl ketone, ethers such as dipropyl ether, methyl acetate, ethyl acetate and propionic acid. Organic acid esters such as methyl are used,
Water or a mixed solvent of water / alcohol is preferred in terms of easy handling. As the alcohol, alcohols such as methanol, ethanol, and propanol are used, and methanol is preferably used industrially.

The weight ratio of the coagulating liquid to the EVOH strand (coagulating liquid / EVOH strand) in the coagulating liquid is preferably 50 to 10000, and more preferably 1 to 10,000.
00 to 1000. By setting the weight ratio in this range, it is possible to obtain EVOH pellets having a uniform size distribution.

Further, a carboxylic acid is added to the coagulating solution in an amount of 1 to 10%.
000 ppm and / or metal carboxylate from 1 to 1
5000 ppm and / or 1 carboxylic acid ester
It is also preferable to contain the carboxylic acid at 50 to 5000 ppm and / or the metal carboxylate at 10 to 5000 ppm and / or the carboxylic acid ester at 10 to 10,000 ppm. By containing the carboxylic acids in the above range in the coagulation bath, it is possible to more suitably obtain EVOH pellets having a uniform size distribution.

The carboxylic acid is not particularly restricted but includes formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, crotonic acid,
Maleic acid, itaconic acid and the like can be mentioned, but acetic acid is preferably used.

The metal carboxylate is not particularly limited, but sodium formate, potassium formate, magnesium formate, calcium formate, sodium acetate, potassium acetate, magnesium acetate and the like are used, and preferably, sodium acetate is used.

The carboxylic acid ester is not particularly restricted but includes methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl acetoacetate,
Ethyl acetoacetate or the like is used, but methyl acetate is preferably used.

The temperature at which the EVOH solution is brought into contact with the coagulating liquid is preferably from -10 to 40 ° C from the viewpoint of precipitation, and more preferably from 0 to 40 ° C.
-20 ° C, especially 0-10 ° C. The EVOH solution is extruded in a strand form into the coagulating liquid as described above by a nozzle having an arbitrary shape. The shape of the nozzle is not particularly limited, but a cylindrical shape is industrially preferable, and its length is long. The length is preferably 1 to 100 cm,
It is more preferably 3 to 30 cm, and the inner diameter is preferably 0.1 to 10 cm, and more preferably 0.2 to 5.0 cm. Thus, the EVOH (solution) is extruded from the nozzle in the form of a strand. The number of strands is not necessarily one, and any number between several and several hundreds can be extruded.

Next, the EV extruded in a strand shape
OH is cut after sufficient coagulation proceeds, pelletized, and then washed with water. The shape of such a pellet is 1 to 10 mm in diameter in the case of a columnar shape and 1 to 10 mm in length (furthermore, 2 to 6 mm each), and 1 to 10 mm in the case of a spherical shape (further, Is 2 to 6 mm) in view of the stability of the melt-kneading.

The pellets are washed in a water bath at a temperature of 10 to 40 ° C. (further, 20 to 40 ° C.). By such a water washing treatment, oligomers, impurities, solvents and the like in the EVOH are removed. Further, subsequent to or instead of the water washing treatment, EVOH may be treated with an aqueous solution containing various acids and metal salts to contain the acid and metal salts in the EVOH, and the color tone of the dried EVOH may be used. , Heat stability, long run moldability, interlayer adhesion with the adhesive resin when formed into a laminate, heat stretch moldability, and the like are preferred. Such acid components include acetic acid, propionic acid, butyric acid, and lauryl. Acids, stearic acid, oleic acid, organic acids such as behenic acid, and inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, boric acid, phosphoric acid, and the like.Examples of metal salts include alkali metals, alkaline earth metals, and transition metals of the above acids. Metal salts such as metals, particularly acetic acid, phosphoric acid, boric acid and alkali metal salts thereof,
Alkaline earth metal salts are preferably used because of their excellent effects.

The content of acetic acid is as follows:
5 to 1000 ppm (further 10 to 500 pp
m, particularly preferably 20 to 300 ppm). If the content of acetic acid is less than 5 ppm, the effect of containing acetic acid may not be sufficiently obtained, and if it exceeds 1000 ppm, long-run moldability may be reduced. Not preferred.

The content of phosphoric acid is as follows:
The content of phosphoric acid is preferably 5 to 1000 ppm (more preferably 10 to 500 ppm, particularly 20 to 300 ppm) relative to H. If the content of phosphoric acid is less than 5 ppm, the effect of containing phosphoric acid may not be sufficiently obtained. On the contrary, if it exceeds 1000 ppm, the appearance of the obtained molded product is unfavorably deteriorated.

The content of boric acid is as follows:
10 to 10,000 ppm (furthermore, 20 to 2000 ppm, especially 100 to 1000 pp in terms of boron with respect to H)
m), and the content of boron is preferably 1
If the content is less than 0 ppm, the content effect may not be sufficiently obtained, and if it exceeds 10,000 ppm, the appearance of the obtained molded product is undesirably deteriorated.

The content of the metal salt is 5 to 1000 ppm (more preferably 10 to 500 ppm, particularly 20 to 300 ppm) based on EVOH after drying.
If the content is less than 5 ppm, the effect of the content may not be sufficiently obtained.
If it exceeds 00 ppm, the appearance of the obtained molded product is undesirably deteriorated. When two or more kinds of alkali metal and / or alkaline earth metal salts are contained in the EVOH, the total amount thereof is preferably within the above range.

By the above method, the water-containing E used in the present invention
VOH pellets can be obtained. If necessary, a known drying treatment (hot air drying, dielectric heating drying, microwave irradiation drying, etc.) or the surface of the water-containing pellets can be performed as needed, such as adjusting the water content of EVOH before the drying treatment of the present invention. It is also preferable to carry out the operation of removing adhering water in advance from the viewpoint of the stability of melt-kneading.

In the present invention, the water content is 5 to 5 as described above.
The most characteristic feature is that 60% by weight of EVOH pellets is melt-kneaded to reduce the water content to less than 5% by weight, and such a method will be specifically described. Melt kneading of the EVOH pellets can be performed using a known melt kneading apparatus such as a melt extruder, a kneader ruder, a mixing roll, a Banbury mixer, a plast mill, etc. It is industrially preferable to use an extruder. In particular, a twin-screw extruder is suitably used in view of stability of melt-kneading, and a method using such a twin-screw extruder will be described in further detail.

The twin-screw extruder used is not particularly limited, but has an inner diameter of 20 mm or more (more preferably 30 to 150 m).
m) is preferable, and when the inner diameter is less than 20 mm, productivity is poor, which is not preferable.
To 80 (more preferably 30 to 60), and such L / D
If the diameter is less than 20, the drying ability may be insufficient,
Conversely, if it exceeds 80, the residence time of the resin in the extruder becomes unnecessarily long, which is not preferable since thermal degradation is a concern.
The number of vents may be one or more, particularly preferably two or more, and it is preferable that at least one of them is suctioned under reduced pressure in terms of drying efficiency and quality of the obtained resin. The shape of the die hole is not limited, but is preferably a circle having a diameter of 1 to 7 mm (more preferably 2 to 5 mm) in consideration of obtaining a pellet having an appropriate shape and size, and the number of holes is 3 ~ 100 (and 1
0 to 50) is preferable in production.

Further, it is preferable to provide one or more (especially two or more) mesh screens between the extruder and the entrance of the die in order to remove foreign substances and stabilize the resin pressure (stabilize extrusion). In consideration of extrusion stability, it is also preferable to provide a gear pump, a heat exchanger, and the like.

In carrying out the melt kneading, the temperature of the cylinder (T _I ) at the inlet of the hopper of the extruder and the temperature (T _O ) of the cylinder at the outlet of the extruder are defined by the following formula (1). If T ₀ / T _I is less than 1.1, the drying ability may be insufficient or the extrusion may be unstable. Is unfavorable because the quality of EVOH may be deteriorated (thermal degradation) or the extrusion may be unstable, and further satisfies the condition of the following formula (1 ′), particularly the condition of the following formula (1 ″). Note that the above-mentioned cylinder temperature refers to the actually measured temperature of the cylinder: 1.1 ≦ T ₀ / T _I <10 (1) 1.5 ≦ T ₀ / T _I <8 · ·· (1 ') 1.8 ≦ T 0 / T I <5 ··· (1 ") ( however, T _{0, I} both units ℃)

The heating of the cylinder of the extruder is usually carried out by mounting a plurality of heaters. For example, in the case of eight divisions, the extruder outlet (resin discharge section, die connection section) is connected from the hopper inlet (resin supply section). ), Eight heaters are mounted on the cylinder of the extruder, and the temperature can be set for each of the heaters. In the order of C1, C2, C3... C7, C8, the cylinder at the entrance of the above hopper The temperature is C1 and the cylinder temperature at the extruder outlet is C8.

Further, particularly preferable to set the temperature of the feeding zone of the extruder (T _F) and the metering zone temperature (T _M) so as to satisfy the following condition (2), T _M / When T _F is less than 1.1, the drying ability may be insufficient or the extrusion may be unstable.
In the above case, the quality of the EVOH may deteriorate (thermal deterioration) or the extrusion may become unstable, which is not preferable. Further, the condition of the following formula (2 ′), particularly the condition of the following formula (2 ″) 1.1 ≦ _TM / _TF <10 (2) 1.2 ≦ _TM / _TF <9 (2 ′) 1.3 ≦ _TM / T _F <8 ... (2 ") (However, the unit is ° C for both T _M and T _F )

The term “feeding zone” as used herein refers to a 1/3 portion of the hopper entrance when the cylinder barrel of the extruder is divided into three equal parts in the longitudinal direction. Means each one third of the outlet of the extruder, the temperature of the feeding zone (T _F )
Is the average value of the (measured) temperature of the cylinder of the divided heater part completely contained in the former one-third part, and the temperature (T _M ) of the metering zone in the latter one-third part. It means the average value of (actually measured) temperatures of the cylinders of the divided heater section that are completely included.

The cylinder temperature and the temperatures of the feeding zone and the metering zone may be adjusted as described above. At this time, the cylinder temperature, the temperature of the feeding zone and the temperature of the metering zone are usually from room temperature to 300 ° C.
(More preferably, 50 to 280 ° C.).

Further, the molten EVOH is supplied to the die and extruded by the above-mentioned temperature setting, and the temperature of the EVOH (resin temperature) in the die is 150 °.
It is also preferable to adjust the extrusion conditions (set temperature, screw shape, screw rotation speed, etc.) so that the temperature is up to 300 ° C (more preferably 180 to 280 ° C).
If it is less than 3, extrusion may become unstable, and conversely, 300
If the temperature exceeds ℃, the quality of EVOH may be deteriorated (thermal degradation), which is not preferable.

The rotation speed of the screw is 50 to 300 r.
pm (furthermore, from 80 to 200 rpm). If the number of revolutions is less than 50 rpm, the drying ability may be insufficient. If the number of revolutions exceeds 300 rpm, the quality of the EVOH deteriorates (thermal degradation). It is not preferable because the charging speed of EVOH is 10 to 4
It is selected from the range of 00 kg / hr (more preferably 20 to 300 kg / hr). When the charging speed is less than 10 kg / hr, it is unproductive, and when it exceeds 400 kg / hr, sufficient drying may not be performed. No, EVO
The residence time of H in the extruder is 10 to 600 seconds (further 1 hour).
If the residence time is less than 10 seconds, sufficient drying may not be performed. On the other hand, if the residence time exceeds 600 seconds, the quality of the EVOH deteriorates (thermal degradation).
The pressure (resin pressure) applied to the EVOH is selected from the range of 5 to 300 kg / cm ² (more preferably 10 to 200 kg / cm ² ), and the pressure is less than 5 kg / cm ² and 300 kg. If it exceeds / cm ² , extrusion may be unstable, which is not preferable. It is also preferable to seal the inside of the hopper and around the vent hole with nitrogen in order to prevent thermal deterioration of the EVOH.

Thus, EVOH having a desired water content of less than 5% by weight can be obtained. To achieve such a water content, for example, in the method using the above twin screw extruder, various conditions are required. In particular, it is possible to adjust the resin temperature (set temperature of the extruder, screw shape, etc.) and the discharge amount (screw rotation speed, resin charge amount, etc.), and the like. % By weight or less, particularly preferably 0.5% by weight or less, from the viewpoint that troubles such as foaming during melt molding (extrusion molding, injection molding, etc.) after drying can be reduced.

The water content of the EVOH after the drying treatment is measured and calculated by the following method. [Measurement Method of Volatile Content] After weighing EVOH pellets with an electronic balance (W1: unit g), the EVOH pellets are placed in a hot-air oven type dryer maintained at 150 ° C., dried for 5 hours, and further 30 minutes in a desiccator. The weight after cooling is similarly weighed (W2: unit g) and calculated from the following equation (4). Water content (%) = {(W1−W2) / W1} × 100 (4) The drying method of the present invention is not limited to the production of EVOH (drying of water-containing pellets) as described above, but also to the pellets. Can also be used for drying of a crushed scrap or the like after a molded article mainly composed of EVOH has been absorbed during storage.

Further, after carrying out the drying method of the present invention, EVO
If necessary, known drying treatments (hot air drying, dielectric heating drying, microwave irradiation drying, etc.) can be performed together with the H content adjustment.

Thus, according to the drying method of the present invention, it is possible to obtain EVOH of good quality with suppressed coloring.
Furthermore, according to the drying method of the present invention, a stable and continuous operation can be performed as compared with the conventional hot-air drying, so that an EVOH that has been efficiently dried can be obtained.
Is useful for various packaging materials (films, sheets, containers, etc.) such as foods, pharmaceuticals, industrial chemicals, and agricultural chemicals, as well as fibers, various molded products, and the like.

[0043]

The present invention will be specifically described below with reference to examples. In the examples, “parts” and “%” mean on a weight basis unless otherwise specified.

Example 1 To 1000 parts of a methanol solution containing 40% of an ethylene-vinyl acetate copolymer having an ethylene content of 40 mol%, 40 parts of a methanol solution containing 6% of sodium hydroxide and 2,500 parts of methanol were continuously supplied. A saponification reaction was performed at 110 ° C. for 2.5 hours while distilling off by-product methyl acetate and excess methanol from the system to obtain EVOH having a saponification degree of the vinyl acetate component of 99.0 mol%. Next, the saponification reaction completed solution was mixed with 450 ml of 30% aqueous methanol.
The excess methanol was distilled off while supplying the part at an azeotropic point to obtain a mixed solution of EVOH in water / methanol [water / methanol = 30/70 (weight ratio), resin concentration 40%].
Subsequently, the EVOH solution (liquid temperature 50 ° C.) is extruded in a strand form from a nozzle having a pore diameter of 4 mm into a coagulating liquid (95% water, 5% methanol) tank maintained at 5 ° C.
After solidifying the OH into strands, the strand-like EVOH is guided to a take-off roller attached to the end of the water tank, cut with a cutter, and cut into white porous pellets having a diameter of 4 mm and a length of 4 mm (resin content 30%). %, A water content of 25%, and a methanol content of 45%). Further, the obtained white porous pellets are put into 1000 parts of warm water at 30 ° C. and stirred and washed for about 240 minutes to obtain water-containing EVOH pellets (water content: 60%). Nitrogen gas was brought into contact with the apparatus in an 80 ° C. atmosphere for 40 minutes (superficial velocity 1.6 m / sec) to obtain EVOH pellets having a water content of 25% by weight.

Next, the obtained EVOH pellets are supplied to a twin-screw extruder equipped with a strand die, melt-kneaded under the following conditions, and the strands are passed through a water bath, cooled and then cut with a pelletizer. Thus, EVOH pellets having a water content of 0.15% were obtained. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. Such pellets could be obtained efficiently at a rate of 50 kg / hr. Further, the pelletization was continuously performed for 10 hours, but no occurrence of strand breakage, foreign matter, eye drop, etc. was observed at all, and stable pellet drying was possible.

[Melting Pelletizing Condition by Twin Screw Extruder] Screw outer diameter 57 mmΦ L / D 44 Strand die shape 12 hole 3.5 mmΦ diameter Screen mesh 90/120 / 90mesh vent C5 part and C8 part are opened, C11 part Vacuum suction Nitrogen sealing in hopper Screw rotation speed 100 rpm Cylinder set temperature C1: 100 ° C (100 ° C) (): Actual measured temperature C2: 100 ° C (100 ° C) C3: 100 ° C (100 ° C) C4: 150 C (146 C) C5: 200 C (199 C) C6: 200 C (178 C) C7: 200 C (191 C) C8: 200 C (185 C) C9: 200 C (198 C) C10: 200 C ( 198 ° C) C11: 200 ° C (196 ° C) C12: 200 ° C (202 ° C) C13: 200 ° C (204 ° C) AD: 20 ℃ (200 ℃) D: 200 ℃ (199 ℃) screw load 110Amp resin pressure 13 kg / cm ³

As described above, the seal at the entrance of the hopper of the extruder is
The temperature of the cylinder C1 (T_I) At 100 ° C.
Temperature of cylinder C13 at the mouth (T_O) At 204 ° C. and T₀
/ T _I= 2.04, which satisfies the condition of equation (1) in the text.
And the feeding zone of the extruder.
Temperature (T_F) Is 111.5 ° C. on average of C1 to C4
And the temperature of the metering zone (T_M) Is for C10-C13
On average at 200 ° C, T_M/ T_F= 200 / 111.5 =
1.79, which satisfies the condition of equation (2) in the text.
It was.

Example 2 In Example 1, EVOH pellets having a water content of 50% by weight were obtained by changing the drying conditions using a tower-type fluidized bed drier, and the same operation was performed to obtain an EVOH pellet having a water content of 0.25%. EVOH pellets were obtained. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. Such pellets could be obtained efficiently at a rate of 50 kg / hr. Further, the pelletization is continuously performed for 10 minutes.
After running for hours, no breaks in the strands, no foreign matters, and no dents were observed, and the pellets could be dried stably.

Example 3 In Example 1, EVOH pellets having a water content of 10% by weight were obtained by changing the drying conditions using a tower-type fluidized bed drier, and the same operation was performed to obtain an EVOH pellet having a water content of 0.20%. EVOH pellets were obtained. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. Such pellets could be obtained efficiently at a rate of 70 kg / hr. Further, the pelletization is continuously performed for 10 minutes.
After running for hours, no breaks in the strands, no foreign matters, and no dents were observed, and the pellets could be dried stably.

Example 4 EVOH pellets having a water content of 0.22% were obtained in the same manner as in Example 1 except that the extrusion temperature under the melt-kneading conditions by the twin-screw extruder was changed as follows.

Cylinder set temperature C1: 50 ° C. (50 ° C.) (): Measured temperature C2: 100 ° C. (100 ° C.) C3: 150 ° C. (145 ° C.) C4: 200 ° C. (197 ° C.) C5: 230 ° C. C6: 230 ° C (227 ° C) C7: 230 ° C (227 ° C) C8: 230 ° C (224 ° C) C9: 230 ° C (229 ° C) C10: 230 ° C (230 ° C) C11: 230 ° C (230 ° C) ) C12: 230 ° C (232 ° C) C13: 230 ° C (232 ° C) AD: 230 ° C (230 ° C) D: 230 ° C (229 ° C)

As described above, the temperature (T _I ) of the cylinder C1 at the inlet of the hopper of the extruder is 50 ° C., the temperature (T _O ) of the cylinder C13 at the outlet of the extruder is 232 ° C., and T ₀ /
T _I = 4.64, which satisfies the condition of formula (1) in the text, and the temperature ( _TF ) of the feeding zone of the extruder is 123 ° C. on average of C1 to C4, The temperature (T _M ) of the metering zone is 231 ° C. on the average of C 10 to C 13, and T _M / T _F = 231/123 = 1.88, which satisfies the condition of the expression (2) in the text. there were.
The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. Such pellets could be obtained efficiently at a rate of 70 kg / hr. Further, the pelletization was continuously performed for 10 hours,
No occurrence of strand breakage, foreign matter, eye drop, etc. was observed at all, and stable drying of the pellets was achieved.

Example 5 An EVOH pellet having a water content of 0.20% was obtained in the same manner as in Example 1, except that the extrusion temperature under the melt-kneading conditions by the twin-screw extruder was changed as follows.

Cylinder set temperature C1: 0 ° C. (31 ° C.) (): Actual measured temperature C2: 50 ° C. (50 ° C.) C3: 50 ° C. (62 ° C.) C4: 100 ° C. (97 ° C.) C5: 250 ° C. C6: 250 ° C (249 ° C) C7: 250 ° C (248 ° C) C9: 250 ° C (250 ° C) C10: 250 ° C (250 ° C) C11: 250 ° C (251 ° C) C12: 250 ° C (251 ° C) C13: 250 ° C (252 ° C) AD: 250 ° C (250 ° C) D: 250 ° C (250 ° C)

As described above, the temperature (T _I ) of the cylinder C1 at the inlet of the hopper of the extruder was 31 ° C., the temperature (T _O ) of the cylinder C13 at the outlet of the extruder was 252 ° C., and T ₀ /
T _I = 252/31 = 8.13, and (1) in the text
Is intended to satisfy the equation of condition, also, the extruder feeding zone temperature (T _F) is at 60 ° C. the average of C1 -C4, metering zone temperature (T _M) is C10～
At an average of 251 ° C. for C13, T _M / T _F = 251/60 =
4.18 was achieved, thereby satisfying the condition of the expression (2) in the text. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. Such pellets could be obtained efficiently at a rate of 70 kg / hr. Further, the pelletization is continuously performed for 10 minutes.
After running for hours, no breaks in the strands, no foreign matters, and no dents were observed, and the pellets could be dried stably.

Example 6 The same procedure as in Example 1 was carried out except that the conditions for melt-kneading with the twin-screw extruder were changed as follows, and the water content was 0.1%.
20% EVOH pellets were obtained.

Screw outer diameter 83 mmΦ L / D 30 Strand die shape 20 holes with 4.5 mmΦ diameter Screen mesh 90/120/90 mesh Vent C3 is opened, C5 is vacuum suctioned Nitrogen sealing in hopper Screw rotation speed 200 rpm Cylinder setting Temperature C1: 100 ° C (100 ° C) (): Actual measured temperature C2: 100 ° C (100 ° C) C3: 100 ° C (100 ° C) C4: 150 ° C (163 ° C) C5: 200 ° C (220 ° C) C6: 200 ° C (222 ° C) AD: 200 ° C (220 ° C) D: 200 ° C (220 ° C) Screw load 150 Amp Resin pressure 100 kg / cm ³

As described above, the seal at the entrance of the hopper of the extruder was
The temperature of the cylinder C1 (T_I) At 100 ° C.
Temperature of the cylinder C6 at the mouth (T_O) At 222 ° C. and T₀
/ T _I= 2.22, which satisfies the condition of equation (1) in the text.
And the feeding zone of the extruder.
Temperature (T_F) Is an average of C1 to C2 at 100 ° C.,
Temperature of metering zone (T_M) Is the average of C5 to C6
At 221 ° C, T_M/ T _F= 221/100 = 2.21
It satisfies the condition of equation (2) in the text.
Was. The obtained EVOH pellets were visually observed and found to be colorless.
-Transparent and no yellow coloring was observed. Also take
Pellets must be obtained efficiently at a rate of 150 kg / hr
Was completed. Further, the pelletization was continuously performed for 10 hours.
However, the occurrence of broken strands, foreign matter, eye stains, etc.
The pellets were dried stably.

Example 7 The same procedure as in Example 1 was carried out except that the conditions for melt-kneading with the twin-screw extruder were changed as follows, and the water content was reduced to 0.1.
25% EVOH pellets were obtained.

Screw outer diameter 30mmΦ L / D 42 Strand die shape 3.5mmΦ 2 holes Screen mesh 90 / 90mesh Vent C4 is opened, C6 is vacuum suctioned Nitrogen sealing in hopper Screw rotation speed 120rpm Cylinder set temperature C1 C: 100 ° C (99 ° C) C3: 100 ° C (100 ° C) C4: 150 ° C (143 ° C) C5: 200 ° C (198 ° C) C6: 200 ° C ( 195 ° C) C7: 200 ° C (200 ° C) AD: 200 ° C (200 ° C) D: 200 ° C (200 ° C) Screw load 20 Amp Resin pressure 75 kg / cm ³

As described above, the seal at the entrance of the hopper of the extruder was
The temperature of the cylinder C1 (T_I) At 100 ° C.
Temperature of cylinder C7 at the mouth (T_O) At 200 ° C. and T₀
/ T _I= 2, which satisfies the condition of equation (1) in the text
And the temperature of the feeding zone of the extruder.
Degree (T_F) Is an average of C1 to C2 of 99.5 ° C.
Ring zone temperature (T_M) Is 1 on average for C6 to C7
At 97.5 ° C, T_M/ T _F= 197.5 / 99.5 = 1.
98, which satisfies the condition of equation (2) in the text.
there were. The obtained EVOH pellets were visually observed,
It was colorless and transparent, and no yellow coloring was observed. again
Such pellets can be obtained efficiently at a rate of 10 kg / hr.
I was able to. Further, the pelletization was continuously performed for 10 hours.
However, the occurrence of broken strands, foreign matter, eye stains, etc.
It was not recognized and stable pellets could be dried.

Example 8 EVOH pellets having a water content of 0.28% were obtained in the same manner as in Example 1 except that the melt-kneading conditions were changed as follows using a single screw extruder. .

Screw outer diameter 75 mmΦ L / D 36 Strand die shape 24 holes of 4.5 mmΦ diameter Screen mesh 90 / 90mesh Vent C3 is opened, C6 is vacuum suctioned Nitrogen sealing in hopper Screw rotation speed 200rpm Cylinder set temperature C1 C: 100 ° C (99 ° C) C3: 100 ° C (99 ° C) C4: 150 ° C (158 ° C) C5: 200 ° C (218 ° C) C6: 300 ° C ( 275 ° C) C7: 300 ° C (275 ° C) AD: 200 ° C (270 ° C) D: 200 ° C (270 ° C) Screw load 125 Amp Resin pressure 75 kg / cm ³

As described above, the temperature (T _I ) of the cylinder C1 at the inlet of the hopper of the extruder is 97 ° C., the temperature (T _O ) of the cylinder C7 at the outlet of the extruder is 275 ° C., and T ₀ /
T _I = 2.84, which satisfies the condition of the expression (1) in the text, and the temperature (T _F ) of the feeding zone of the extruder is 98 ° C. on average of C1 to C2, The temperature (T _M ) of the metering zone is 2 on average for C6 to C7.
At 75 ° C., T _M / T _F = 275/98 = 2.81.
The condition of the expression (2) in the text was also satisfied. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. Such pellets could be obtained efficiently at a rate of 100 kg / hr. Further, the pelletization was continuously performed for 10 hours,
No occurrence of strand breakage, foreign matter, eye drop, etc. was observed at all, and stable drying of the pellets was achieved.

Example 9 The white porous pellets obtained in Example 1 were
After washing with a 0.5% acetic acid aqueous solution, 0.1% acetic acid, 0.1% acetic acid was added.
It was poured into an aqueous solution containing 03% magnesium acetate and 0.02% calcium acetate, and stirred at 30 ° C. for 5 hours to obtain a wet EVOH pellet [after drying, acetic acid 1 was added to EVOH.
00 ppm, magnesium acetate 35 ppm (calculated as magnesium), and calcium acetate 20 ppm (calculated as calcium)].
A 15% EVOH pellet was obtained. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. In addition, such pellets are 50 kg / h.
It could be obtained efficiently at the rate of r. Further, the pelletization was continuously performed for 10 hours, but no occurrence of strand breakage, foreign matter, eye drop, etc. was observed at all, and stable pellet drying was possible.

Example 10 In Example 1, the obtained white porous pellets were
After washing with warm water, throw it into an aqueous solution containing 0.08% boric acid and stir at 30 ° C. for 5 hours to obtain water-containing EVOH pellets [380 ppm (boron equivalent) of boric acid in EVOH after drying]. Except that the water content was 0.1%.
A 15% EVOH pellet was obtained. The obtained EVOH pellets were visually observed, but were colorless and transparent, and no yellow coloring was observed. In addition, such pellets are 50 kg / h.
It could be obtained efficiently at the rate of r. Further, the pelletization was continuously performed for 10 hours, but no occurrence of strand breakage, foreign matter, eye drop, etc. was observed at all, and stable pellet drying was possible.

Comparative Example 1 In Example 1, 60 kg of water-containing EVOH pellets were charged into a 200 liter hot air dryer, and the water content was 30%.
Up to 65 ° C, up to 85 ° C up to a water content of 30-10%,
Thereafter, each was dried in an air stream at 110 ° C. for 16 hours to obtain EVOH pellets having a water content of 0.15%. The obtained EVOH pellets were visually observed, but were colored (yellowing).
And the amount of EVOH pellets obtained was about 1
The efficiency was poor at kg / hr.

[0068]

According to the present invention, since the EVOH is dried by melting and kneading, the coloring (yellowing) of the EVOH can be suppressed, the EVOH (dry) production efficiency is high, and the EVOH can be obtained by the method of the present invention. EVOH is very useful as a packaging material for foods, pharmaceuticals, agricultural chemicals, industrial chemicals, etc., fibers, and various molded products.

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[Procedure amendment]

[Submission date] July 19, 2000 (2007.1)
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction contents]

[Melting Pelletizing Condition by Twin Screw Extruder] Screw outer diameter 57 mmΦ L / D 44 Strand die shape 12 hole 3.5 mmΦ diameter Screen mesh 90/120 / 90mesh vent C5 part and C8 part are opened, C11 part Vacuum suction Nitrogen sealing in hopper Screw rotation speed 100 rpm Cylinder set temperature C1: 100 ° C (100 ° C) (): Actual measured temperature C2: 100 ° C (100 ° C) C3: 100 ° C (100 ° C) C4: 150 C (146 C) C5: 200 C (199 C) C6: 200 C (178 C) C7: 200 C (191 C) C8: 200 C (185 C) C9: 200 C (198 C) C10: 200 C ( 198 ° C) C11: 200 ° C (196 ° C) C12: 200 ° C (202 ° C) C13: 200 ° C (204 ° C) AD: 20 ℃ (200 ℃) D: 200 ℃ (199 ℃) screw load 110Amp resin pressure 13 kg / cm ²

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0057

[Correction method] Change

[Correction contents]

[0057]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0060

[Correction method] Change

[Correction contents]

[0060]

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0063

[Correction method] Change

[Correction contents]

[0063]

Continued on the front page F term (reference) 4F070 AA13 AA26 BA01 BB08 4J002 BE03 FD020 FD070 FD090 FD170 FD180

Claims (4)

[Claims] 1. A saponified ethylene-vinyl acetate copolymer having a water content of less than 5% by weight by melting and kneading a saponified ethylene-vinyl acetate copolymer having a water content of 5 to 60% by weight. Drying method. 2. An extruder is used for melt-kneading, and the temperature of the cylinder at the entrance of the hopper (T _I ) and the temperature of the cylinder at the exit of the extruder (T _O ) are as follows: The method for drying a saponified ethylene-vinyl acetate copolymer according to claim 1, wherein the conditions of the formula are satisfied. 1.1 ≦ T ₀ / T _I <10 (1) (However, both T ₀ and T _I are in ° C.) 3. An extruder is used for melt-kneading, and the temperature ( _TF ) of a feeding zone of the extruder is used.
2. The method for drying a saponified ethylene-vinyl acetate copolymer according to claim 1, wherein the temperature ( _TM ) of the metallizing zone satisfies the condition of the following formula (2). 1.1 ≦ T _M / T _F <10 (2) (however, both T _M and T _F are in ° C.) 4. The saponified ethylene-vinyl acetate copolymer according to claim 1, wherein the ethylene content is 5 to 70 mol% and the saponification degree of the vinyl acetate component is 85 mol% or more. A method for drying a saponified ethylene-vinyl acetate copolymer according to the above.