JP5908298B2 - Method for producing desiccant-containing resin composition pellets - Google Patents

Description

  The present invention is an ethylene-vinyl ester copolymer saponified product (hereinafter referred to as “a saponified ethylene-vinyl ester copolymer”) that can exhibit excellent functions such as gas barrier properties without causing poor appearance due to foaming when processed into a film, sheet or the like. The present invention relates to a method for producing a desiccant-containing resin composition pellet capable of efficiently producing a resin composition pellet containing a desiccant as a main component.

  EVOH is excellent in transparency, gas barrier properties against oxygen, solvent resistance, oil resistance, mechanical strength, molded into films, sheets, bottles, etc., food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, agricultural chemicals Widely used as various packaging materials such as packaging materials. And it is known that EVOH will exhibit functions, such as the above-mentioned gas barrier property, more by designing it as close to a dry state as possible. Therefore, in order to ensure the dry state of EVOH, for example, a desiccant is dispersed in a matrix of EVOH (see, for example, Patent Document 1).

  On the other hand, in order to produce pellets of thermoplastic resin compositions such as EVOH, generally, a resin composition compounded by a kneader is extruded into a strand shape, and the extruded strand is cooled with water, and this is converted into a strand. A method of cutting into an appropriate length with a cutter and pelletizing is used.

JP 2008-75084 A

  However, when a resin composition pellet containing EVOH as a main component and containing a desiccant is produced by the above general method, the desiccant absorbs water when the strand is cooled with water. This causes a problem that the water content of the resulting resin composition pellets is increased. When a film or the like is produced using a resin composition pellet having a high moisture content, foaming or the like is produced during production, resulting in a defect such as a poor appearance such as a hole, so this improvement is required.

  Therefore, it is conceivable that the strand is cooled by a method that does not use water, for example, by air cooling. However, in order to sufficiently cool the strand by air cooling, the amount of resin composition extruded from the kneader is extremely reduced. It is necessary to let If it does so, the residence time of the resin composition in a kneading machine will become long, and the new problem that the retained resin composition will adhere to the inside of a kneading machine and will cause thermal degradation will generate | occur | produce. This problem is particularly prominent because EVOH has the property of high adhesion to metal.

  The present invention has been made in view of such circumstances, and has a desiccant-containing resin composition that can efficiently produce resin composition pellets having a low moisture content, EVOH as a main component, and a desiccant. The purpose is to provide a method for producing pellets.

In order to achieve the above object, the present invention is a method for continuously producing resin composition pellets containing EVOH as a main component and containing a desiccant, wherein the resin composition is melt-kneaded with a kneader, A step of extruding into a strand, a step of water-cooling the extruded strand while moving in water, a step of removing water from the surface of the water-cooled strand using at least one of air soccer and an air knife, and A step of cutting the strand into an appropriate length, and the time (T) required for the movement of the strand in the water in the water cooling step is a desiccant-containing resin composition pellet satisfying the following formula (1): The manufacturing method is the gist.
0.45 seconds ≦ T ≦ 1.6 seconds (1)

According to the method for producing a desiccant-containing resin composition pellet of the present invention, the desiccant-containing resin composition extruded in a strand form from a kneader can be cooled by water cooling, so the amount of extrusion from the kneader is extremely small. Therefore, pellets can be produced efficiently. Moreover, in the water cooling step of the strand, the strand moving conditions are limited, and a step of removing water from the water-cooled strand surface using at least one of air soccer and an air knife is provided. Despite this, pellets with low moisture content can be produced. Furthermore, since the desiccant-containing resin composition pellets obtained by the production method of the present invention contain a desiccant and have a low moisture content, films produced using this as a raw material have functions such as gas barrier properties. Excellent appearance and no appearance defects such as perforations.

That is , since the water removal step uses at least one of air soccer and air knife, it is possible to efficiently prevent water from penetrating into the strand, and to produce pellets with a further low water content.

  Furthermore, when the water removal step uses a plurality of at least one of air soccer and air knife, it is possible to prevent water from penetrating into the strands more efficiently and to produce pellets with a lower moisture content. .

  In the present invention, the phrase “main component” means that the component occupies a majority of the whole, and includes that the whole consists of only the main component.

  Further, in the present invention, “removing water from the surface of the strand” means adopting a technique for removing, and means not completely removing.

It is the schematic of the process in one embodiment of this invention. It is the schematic of the process in other embodiment of this invention.

  Next, an embodiment for carrying out the present invention will be described.

  FIG. 1 shows the outline of the manufacturing process of the desiccant-containing resin composition pellet in one embodiment of the present invention. The manufacturing process of the desiccant-containing resin composition pellets can be summarized as follows. First, a resin composition containing EVOH as a main component and containing a desiccant is melt-kneaded with a kneader 1 and pressed into a strand from the die 1a. (Extrusion process) Next, the extruded strand 2 is cooled with water while moving in the water 4 in the water tank 3 (water cooling step). At this time, the time (T) required for the movement of the strand 2 is controlled so as to satisfy a predetermined condition described later. Then, water is immediately removed from the surface of the strand 2 pulled up from the water 4 by the air soccer (5a, 5b) (water removing step), and then the strand 2 is cut to an appropriate length by the cutter roll 10 (cut) Step), pellets 12.

  First, the resin composition used in the present invention contains EVOH as a main component and a desiccant. This resin composition will be described.

[EVOH]
In the present invention, EVOH used as a main component is obtained by saponifying an ethylene-vinyl ester copolymer obtained by copolymerizing a fatty acid vinyl ester and ethylene, and has an ethylene structural unit and a vinyl alcohol structure. It is mainly composed of units and contains a slight amount of vinyl ester structural units remaining without being saponified.

  In addition, the content rate of EVOH in the whole resin composition exceeds 50 weight%. Especially, it exceeds 50 weight% and 99 weight% or less is preferable, More preferably, it is 60 to 95 weight%, More preferably, it is 70 to 90 weight%. This is because if the amount of EVOH is too small, gas barrier properties tend to be insufficient.

〔desiccant〕
The desiccant used in the present invention may be an anhydride of a substance having an equilibrium vapor pressure (equilibrium humidity) and taking water of crystallization, for example, partial dehydration or complete dehydration of polyvalent metal sulfate hydrate. Products, partially dehydrated or completely dehydrated carboxylate hydrates, phosphates that can form hydrates, and the like. In addition, other hydrate-forming salts, for example, salts such as sodium borate and magnesium sulfate, and anhydrides thereof can also be used. Furthermore, other hygroscopic compounds, for example, cobalt chloride, calcium chloride, magnesium chloride, sodium chloride, sodium nitrate, sugar, silica gel, bentonite, molecular sheep, superabsorbent resin, and the like can also be used. Of these, polyvalent metal sulfate hydrates are suitable in terms of dispersibility in resins, moisture absorption efficiency, thermal stability, and the like, and are represented by MgSO ₄ .nH ₂ O (where 0 ≦ n ≦ 3). Magnesium sulfate and anhydrous magnesium sulfate are more suitable.

  And it is preferable that the content rate of the said desiccant in the whole resin composition is less than 50 weight%. Especially, 1 to 40 weight% is preferable, More preferably, it is 5 to 30 weight%. When the ratio of the desiccant is within the above range, a resin composition having good dispersibility in the resin composition of the desiccant, high hygroscopicity and water retention, and excellent moldability can be obtained. It is because it is in a tendency.

  The desiccant-containing resin composition contains, in addition to the EVOH, other thermoplastic resins in an amount of 30% by weight or less, preferably 20% by weight or less, more preferably 10% by weight or less, based on EVOH. can do. Examples of the other thermoplastic resins include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-vinyl acetate copolymer, ionomer, ethylene-propylene copolymer, ethylene-acrylic. Acid ester copolymer, polypropylene, propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymer, polybutene, polypentene, or other olefin homopolymer or polycyclic olefin, or of these olefins Broadly defined polyolefin resins such as homo- or copolymers graft-modified with unsaturated carboxylic acids or esters thereof, polystyrene resins, polyesters, polyamides, copolymerized polyamides, polyvinyl chloride, polyvinylidene chloride, acrylic resins, Vinyl ester And thermoplastic resins such as polyester resins, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, and chlorinated polypropylene. In particular, when the desiccant-containing resin composition obtained by the production method of the present invention is used as a food packaging material as a multilayer structure, at the end of the packaging material after hydrothermal treatment of the packaging material It is preferable to blend a polyamide-based resin in that EVOH can be prevented from being eluted. The polyamide-based resin can form a network structure by the interaction of the amide bond with the OH group and / or ester group of EVOH, thereby preventing the elution of EVOH during hydrothermal treatment. . Therefore, in the case of a resin composition used as a packaging material for retort food or boiled food, it is preferable to add a polyamide-based resin.

  In addition to the EVOH and the desiccant, an additive may be appropriately added to the desiccant-containing resin composition. Examples of such additives include plasticizers, stabilizers, lubricants, colorants, surfactants, ultraviolet absorbers, antistatic agents, crosslinking agents, metal salts, fillers, reinforcing agents such as various fibers, and the like. I can give you.

  Below, according to FIG. 1, an example of the manufacturing process of this desiccant containing resin composition pellet is demonstrated in order along each process of an extrusion process, a water cooling process, a water removal process, and a cutting process. In addition, in FIG. 1, a magnitude | size, an external appearance, etc. are shown typically and are different from an actual thing (the same also in FIG. 2).

[Extrusion process]
In this extruding step, the resin composition containing EVOH as a main component and containing a desiccant is melt-kneaded in a kneader 1 as shown in FIG. The product is extruded into a strand shape. In this embodiment, saponified ethylene-vinyl acetate copolymer (ethylene content 29 mol%, saponification degree 99 mol%, MFR 4 g / 10 min) 80 parts by weight, anhydrous magnesium sulfate 10 parts by weight as a desiccant, polyamide A resin composition containing 10 parts by weight of 6 nylon (melting point: 220 ° C.) and containing a desiccant is used as the resin-based resin composition. The kneader 1 has a screw outer diameter of 47 mm and an L / D of 52.5. A twin screw extruder is used. Then, the screw rotation speed of the kneading machine 1 was 380 rpm, the resin composition containing the desiccant was melt-kneaded at a barrel set temperature of 240 ° C. of the extruder, and was coated with Teflon (registered trademark) at 3.8 mmφ 15 holes. Extrusion is performed from the tip of the die 1a to a discharge rate of 200 kg / hour.

[Water cooling process]
This water-cooling step is a step of cooling the strand-shaped resin composition (strand 2) extruded from the die 1a of the kneader 1 while moving in the water 4 in the water tank 3 as shown in FIG. Yes, the strand 2 is immersed in the water 4 by a pressing jig 6 with a roller. The water 4 in the water tank 3 is circulated and the flow rate is adjusted so that the temperature is maintained at about 35 ° C. And the time (T) required for the strand 2 movement in the said water 4 needs to satisfy | fill following formula (1). That is, in the following formula (1), if T deviates from the lower limit value, the strand 2 cannot be sufficiently cooled. Conversely, if deviated from the upper limit value, the cooling can be sufficiently performed. This is because water absorption proceeds to the inside of the strand 2 and the moisture content of the manufactured pellets 12 may be increased. The T is measured for the time required to move from the location where the strand 2 is immersed in the water 4 to the location where the strand 2 is pulled up via the pressing jig 6 with a roller. In this embodiment, 0.61 seconds. In addition, the moving speed (take-off speed) (CT) of the strand 2 at this time is 41 m / min, and the moving distance (WL) of the strand 2 in the water 4 is 42 cm.
0.45 seconds ≦ T ≦ 1.6 seconds (1)

[Water removal process]
This water removal step is to remove water from the surface of the strand 2 pulled up from the water 4, and in this embodiment (example shown in FIG. 1), as a method of removing water, two air soccer (5a , 5b) to suck water. Further, it is preferable to remove water from the surface immediately after the strand 2 is pulled up from the water 4. In this embodiment, the strand 2 reaches the air soccer 5 a in 0.5 seconds after being pulled up from the water 4. However, water is removed from the surface. In this embodiment, the second-stage air soccer 5b is arranged at a higher position than the first-stage air soccer 5a. The air soccer suction condition at this time is set to a reduced pressure at which moisture can be sucked into all the strands. In the present invention, the term “immediately” means performing continuously. In addition, the “air soccer” in the present invention has a dent that can hold the strand 2, and by constantly reducing the pressure of the dent part, the moisture present on the surface of the strand 2 is sucked and the moisture is removed from the surface. Refers to a device that can remove

  In this embodiment, the blower 8 is installed on the downstream side of the water tank 3 (upper left side in FIG. 1) so that the relative humidity of the atmosphere surrounding the strand 2 becomes lower. The relative humidity of the atmosphere surrounding the strand 2 can be measured, for example, by installing a portable catalytic temperature and humidity meter at the upper end of the water tank 4.

  Subsequently, the strand 2 from which moisture has been removed from the surface is sent to the cutter roll 10 for pelletization. In this embodiment, the temperature of the strand 2 after passing through the air soccer 5b is approximately 120 ° C., and the strand 2 passes through the presser jig 9 with a roller while maintaining the temperature, and the cutter roll 10 Sent to. In this embodiment, the temperature of the strand 2 near the entrance of the cutter roll 10 is also about 120 ° C.

[Cut process]
In this cutting step, the strand 2 from which water has been removed in the water removal step is cut into an appropriate length while being drawn into the cutter roll 10. In this embodiment, in order to prevent winding of the strand 2 around the cutter roll 10 and fusion of the strands 2, a blower (not shown) is provided in the vicinity of the entrance of the cutter roll 10, and the cutter roll 10 is cooled. I try to cut it. Through this step, the strand 2 is cut into an appropriate length to become pellets 12, which are collected via the shooter 11.

  According to this method, the desiccant-containing resin composition extruded in a strand form from the kneader 1 can be cooled by water cooling, and the pellets 12 can be efficiently produced. And while controlling the time (T) required for the movement of the strand 2 in the water 4 in a water cooling process so that the said Formula (1) may be satisfy | filled, the process of removing water from the surface is followed by the said water cooling process. Since the process is performed immediately, the pellet 12 having a low water content can be produced even though the resin composition containing the desiccant is cooled by water cooling. And the pellet 12 obtained by this method has a low moisture content and contains a desiccant. For this reason, when a film or the like is produced using this, the produced film or the like is excellent in functions such as gas barrier properties, and does not cause foaming or the like during production, and does not cause appearance defects such as perforations. .

  Further, in the water cooling step, since the temperature of the water 4 used for water cooling of the strand 2 is 35 ° C., the strand 2 can be sufficiently cooled, and excessive moisture absorption can be effectively prevented. Can be manufactured. In the water removal step, a plurality of air soccer footballs are provided (5a, 5b), and the position of the second air soccer football 5b is higher than the first air soccer football 5a. Water can be removed from the surface, and penetration of water into the strand 2 can be prevented. Further, in the water removal step, since the blower 8 is installed and the relative humidity of the atmosphere surrounding the strand 2 is lowered, moisture absorption from the atmosphere is suppressed, and water is removed from the surface of the strand 2 more efficiently. can do. Furthermore, in the cutting process, a blower (not shown) is provided in the vicinity of the entrance of the cutter roll 10, and the strand 2 is cut to an appropriate length while cooling the cutter roll 10, so that the winding of the strand 2 The fusion between the strands 2 can be effectively prevented, and efficient production can be performed.

  In the above-described embodiment, a twin screw extruder is used as the kneader 1 in the extrusion step, but a single screw extruder may be used. However, it is more preferable to use a twin screw extruder in that sufficient kneading can be obtained by moderate shearing, and in the point that sufficient kneading can be obtained by moderate shearing, twin screw extrusion in which the screw rotation direction is the same direction. More preferably, a machine is used. Moreover, in said embodiment, although the screw outer diameter of the kneading machine 1 is 47 mm, arbitrary sizes can be set not only according to balance with a production amount and discharge amount. Especially, it is preferable to make the said screw outer diameter into the range of 30-110 mm, The range of 35-80 mm is used suitably, Furthermore, the thing of the range of 40-70 mm is used suitably. And in the said embodiment, although L / D of the said kneader 1 is set to 52.5, the thing of another specification can be used. L / D of the kneader 1 is usually 20 to 100, preferably 25 to 80, and more preferably 30 to 70. That is, if the L / D is too small, there is a risk that problems such as melt kneading become impossible, poor drying agent dispersion, insufficient degassing, unstable discharge, etc. If it is too large, the residence time becomes too long, and the resin composition may be deteriorated, or there may be problems such as mixing of metal powder due to screw distortion.

  In the above embodiment, in the extrusion step, the screw speed of the kneading machine 1 is 380 rpm, the desiccant-containing resin composition is melt-kneaded at about 240 ° C., and the discharge amount from the die 1a is 200 kg / Although it is extruded to be time, it may be extruded under other conditions. Especially, although the said screw rotation speed changes with the magnitude | sizes of an axis | shaft, it is preferable to set it as the range of 100-1000 rpm, and the range of 150-700 rpm and also 250-500 rpm is used suitably. When the number of rotations is too small, the required discharge rate cannot be secured or the discharge rate tends to become unstable. On the other hand, when the rotation rate is too high, undesirable shearing heat is generated, causing deterioration of the resin. Because there is.

  Moreover, it is preferable that the barrel preset temperature of the extruder at the time of melt-mixing the resin composition containing the desiccant is in the range of 160 ° C to 280 ° C, more preferably 200 ° C to 250 ° C, and further 220 ° C to 220 ° C. It is preferable to set it as the range of 240 degreeC. This is because if the temperature is too high, the resin composition tends to be deteriorated and colored. In the present invention, the barrel temperature of the extruder means a set temperature of the barrel of the extruder. Moreover, when the barrel of the extruder has a plurality of sections and each section is set to a different temperature, the highest set temperature is set as the barrel temperature.

  And the set temperature of the die part, head part, and die head part of the extruder when melt-mixing the resin composition containing the desiccant is preferably in the range of 160 ° C. to 280 ° C., more preferably. It is preferable that the temperature is in the range of 200 ° C to 250 ° C, more preferably in the range of 220 ° C to 240 ° C. This is because if the temperature is too high, the resin composition tends to be deteriorated and colored.

  Further, the discharge amount from the die 1a is preferably in the range of 50 to 700 kg / hour, more preferably in the range of 150 to 500 kg / hour, and more preferably in the range of 200 to 350 kg / hour. If the discharge amount is too large, the strand 2 may not be sufficiently cooled in the next water-cooling step. Conversely, if the discharge amount is too small, the residence time of the resin composition in the kneader 1 increases, and the kneading is performed. This is because it may adhere to the inside of the machine 1 and cause thermal deterioration.

  In the above embodiment, in the water cooling step, the water 4 in the water tank 3 is circulated in flowing water, but it is not necessarily required to circulate in flowing water. However, it is preferable to circulate with running water because the water temperature can be kept constant easily. Moreover, in the said embodiment, although the temperature of the said water 4 is set to about 35 degreeC, it can set to arbitrary temperature irrespective of this. Especially, it is preferable to make the temperature of the said water 4 into the range of 0-40 degreeC. If the temperature is too high, a sufficient cooling effect cannot be obtained. Conversely, if the temperature is too low, the water 4 becomes ice and normal cooling cannot be performed, and excessive moisture absorption may occur.

  In the above embodiment, in the water cooling step, the CT (moving speed of the strand 2, that is, the take-up speed of the strand 2) is set to 41 m / min, but may be set to other speeds. . The CT depends on WL (travel distance of the strand 2 in water 4), but is preferably in the range of 10 to 80 m / min, more preferably in the range of 25 to 60 m / min. preferable. Moreover, in the said embodiment, although WL is set to 42 cm, it can also be set to another distance. The WL depends on the CT, but is preferably in the range of 20 to 100 cm, and more preferably in the range of 30 to 60 cm.

  Furthermore, in the said embodiment, although the time (T) required for the movement of the strand 2 in the water 4 in the water cooling step is set to 0.61 seconds, 0.45 seconds ≦ T ≦ 1.6 seconds. It is also possible to set the time to satisfy other conditions. Among these, T is preferably in a range satisfying the condition of 0.5 seconds ≦ T ≦ 1.2 seconds, and more preferably in a range satisfying the condition of 0.6 seconds ≦ T ≦ 0.8 seconds. That is. If the time is too short, a sufficient cooling effect cannot be obtained. On the other hand, if the time is too long, water may not be sufficiently removed from the surface of the strand 2 in the subsequent water removal step such as air soccer. is there.

  In the above embodiment, water is sucked by two air soccers (5a, 5b) in the water removing step. However, in some cases, one may be used. An air knife may be used instead of the air soccer (5a, 5b). In the above embodiment, in the water removal step, the strand 2 is pulled up from the water 4 and then reaches the air soccer 5a in 0.5 seconds so that the water is removed from the surface. However, it is not necessarily limited to this number of seconds. However, it is preferable to perform the operation of removing water from the surface of the strand 2 within 1 second, more preferably within 0.5 second after the strand 2 is pulled up from the water 4.

  The “air knife” in the present invention refers to a device that ejects compressed air through a thin slit. As shown in FIG. 2, the compressed air is uniformly blown from the thin slit to the strand 2, and the strand 2 is drained 14. The moisture adhering to the surface of the strand 2 is blown off, the moisture is easily transferred to the draining plate 14, and the moisture of the draining plate 14 is also blown away, thereby promoting the drying of the strand 2. is there.

  In the above embodiment, in the water removal step, the second stage air soccer 5b is arranged at a higher position than the first stage air soccer 5a, but it is not always necessary to arrange in this manner. However, this arrangement is preferable because water can be removed from the surface of the strand 2 more efficiently. Furthermore, the suction of air soccer may be set to the same condition for the first stage and the second stage, but if the first stage is set to be performed under conditions stronger than the second stage, the surface of the strand 2 can be more efficiently removed. This is preferable because water can be removed.

  Moreover, in the said embodiment, although the air blower 8 is installed in the downstream of the water tank 3 (left upper part in FIG. 1) in the water removal step, the relative humidity of the atmosphere surrounding the strand 2 is not high, and others If the relative humidity is not high by adopting the above method, it may not be provided. However, it is preferable to reduce the relative humidity of the atmosphere surrounding the strand 2 because moisture absorption is suppressed from the atmosphere and water can be more efficiently removed from the surface of the strand 2. Specifically, the relative humidity of the atmosphere surrounding the strand 2 is preferably 80% or less, and more preferably 60% or less. Furthermore, the temperature of the atmosphere surrounding the strand 2 is preferably in the range of 0 ° C to 50 ° C, and more preferably in the range of 20 ° C to 40 ° C. That is, if the temperature is too low, the amount of water that can be evaporated decreases, so the effect of removing moisture tends to be low. On the other hand, if the temperature is too high, condensation tends to occur in other ancillary equipment. In some cases, the condensed water wets the strand again, which may hinder the removal of moisture.

  In the above embodiment, in the water removal step, the temperature of the strand 2 is kept at about 120 ° C. even after passing through the air soccer 5b, and the temperature of the strand 2 near the entrance of the cutter roll 10 is also about. Although it is 120 degreeC, other temperature may be sufficient. However, it is preferable to maintain a temperature of 90 ° C. or higher in that both can prevent re-adhesion of moisture to the strand 2 and obtain a resin composition pellet having a lower moisture content. More preferably, the above temperature is maintained.

  In the above embodiment, a blower (not shown) is provided in the vicinity of the entrance of the cutter roll 10 in the cutting process, and the cutter roll 10 is cut while being cooled. However, the cutter roll 10 itself has a cooling function. This fan is not necessary in the case where is provided or when other cooling means is provided.

  Next, examples will be described together with comparative examples. However, the present invention is not limited to the following examples.

[Example 1]
Saponified ethylene-vinyl acetate copolymer (ethylene content 29 mol%, saponification degree 99 mol%, MFR 4 g / 10 min) 80 parts by weight, anhydrous magnesium sulfate 10 parts by weight as a desiccant, polyamide-based resin composition 6 Using a resin composition containing 10 parts by weight of nylon (melting point: 220 ° C.), a desiccant-containing resin composition pellet was produced by the apparatus used in the above embodiment (see FIG. 1). In addition, the conditions in each process are as follows.
(Extrusion process)
・ Kneading machine: Nippon Steel Works, TEX44αII (Twin screw extruder)
-Die: 3.8 mm diameter x 15 holes Teflon (registered trademark) processed strand die-Melt kneading [barrel portion (C1 to C15) divided sequentially from hopper to screw tip portion (C1 to C15) (C1 in order from the portion closer to the hopper) To C15) and the die head portion (DH) at a total of 16 locations, the temperature was set as follows. C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / C10 / C11 / C12 / C13 / C14 / C15 / DH = cooling only / 50 ° C./80° C./170° C./230° C./240° C. / 230 ° C / 230 ° C / 230 ° C / 230 ° C / 240 ° C / 240 ° C / 240 ° C / 230 ° C / 230 ° C / 220 ° C]
-Screw rotation speed: 380 rpm
・ Discharge rate: 200 kg / hour (water cooling process)
-Time required for movement of the strand 2 in the water 4 (T): 0.61 seconds-Movement speed (CT) of the strand 2: 41 m / min-Movement distance (WL) of the strand 2 in water 4: 42 cm
・ Water tank: running water circulation, water temperature: 35 ℃
(Water removal process)
-Time until the strand pulled up from the water 4 reaches the first air soccer 5a: 0.5 seconds-The strand 2 that reaches the first air soccer 5a reaches the second air soccer 5b Time: 1 second. Install a blower 8 to lower the relative humidity of the atmosphere surrounding the strand 2.
-Temperature of the strand 2 at the inlet of the cutter roll 10: 118 ° C
(Cut process)
-A blower (not shown) is installed at the entrance of the cutter roll 10 and operates while cooling the cutter roll 10.
・ Pellet size: (2.8mmφ 2.8mmL cylinder)

[Example 2]
The composition of the resin composition was saponified ethylene-vinyl acetate copolymer (ethylene content 29 mol%, saponification degree 99 mol%, MFR 4 g / 10 min) 90 parts by weight, and anhydrous magnesium sulfate 10 parts by weight as a desiccant. The desiccant-containing resin composition pellets were produced in the same manner as in Example 1.

Example 3
A desiccant-containing resin composition pellet was produced in the same manner as in Example 1 except that the conditions in each step were changed as follows using the apparatus shown in FIG. That is, in this example, the kneader 1 of the apparatus shown in FIG. 1 and the conditions in the water cooling process are changed, and an air knife 13 and a draining plate 14 are used instead of the air soccer 5a of the apparatus shown in FIG.
(Extrusion process)
-Kneader: Toshiba Machine, 75φ twin screw extruder TEM75SS L / D = 42
-Die: 4.5 mm diameter x 21 holes Teflon (registered trademark) processed strand die-Melt kneading [Barrel parts (C1 to C9) sequentially divided from hopper to screw tip part (C1 to C9) (C1 in order from the part close to the hopper) To C9), the head (H1), and the dice portions (D1, D2), the temperature was set as follows. C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / H1 / D1 / D2 = 80 ° C / 130 ° C / 240 ° C / 240 ° C / 240 ° C / 240 ° C / 240 ° C / 240 ° C / 230 ° C / 240 ° C / 240 ° C / 240 ° C]
・ Screw rotation speed: 150rpm
・ Discharge rate: 300 kg / hour (water cooling process)
-Time required for movement of strand 2 in water 4 (T): 0.76 seconds-Movement speed of strand 2 (CT): 45 m / min-Movement distance of strand 2 in water 4 (WL): 57 cm
・ Water tank: running water circulation, water temperature: 30 ℃
(Water removal process)
Time required for the strand 2 pulled up from the water 4 to reach the draining plate 14: 0.5 seconds. An air knife 13 installed so as to spray air uniformly on the portion of the draining plate 14 where the strand 2 contacts. use.
Time required for the strand 2 reaching the draining plate 14 to reach the air soccer 5b: 1 second. Temperature of the strand 2 at the inlet of the cutter roll 10: 123 ° C.

[Comparative Example 1]
A desiccant-containing resin composition pellet was produced in the same manner as in Example 1 except that the air soccer (5a, 5b) was not used.

[Comparative Example 2]
Except that the movement distance (WL) of the strand 2 in the water 4 was 134 cm and the time (T) required for the movement of the strand 2 in the water 4 was 1.96 seconds, the same as in Example 1, A desiccant-containing resin composition pellet was produced.

[Comparative Example 3]
Except that the movement distance (WL) of the strand 2 in the water 4 was 28 cm and the time (T) required for the movement of the strand 2 in the water 4 was 0.41 second, as in Example 1, A desiccant-containing resin composition pellet was produced.

  For the pellets of Examples 1 to 3 and Comparative Examples 1 to 3, the pellet moisture content was calculated according to the following procedure, and the film appearance obtained by forming the pellet was evaluated. Also shown.

<Pellet moisture content>
Twenty pellets of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared, dried in an oven heated to 150 ° C. for 5 hours, and then allowed to cool in a desiccator for 1 hour. The pellet weight before and after drying was measured to determine the difference, and the moisture content (%) of the pellet was calculated. The average of the moisture content (%) is shown in Table 1.

<Film appearance>
The pellets of Examples 1 to 3 and Comparative Examples 1 to 3 were each formed into a film having a thickness of 30 μm. The appearance of the obtained film was visually observed and evaluated according to the following items.
(Appearance evaluation)
○: No perforation ×: Perforation −: Unevaluable (cannot be pelletized)

  As a result of the above measurement and observation, the average pellet moisture content in Examples 1 to 3 was 0.2% or less, and no defects such as perforations were observed in the appearance of the film. On the other hand, in Comparative Examples 1 and 2, the average pellet moisture content exceeded 0.2%, and defects such as hole opening occurred in the film when the film was formed. Further, in Comparative Example 3, the strand 2 after passing through the air soccer 5b was greatly swelled and could not be pelletized.

  The method for producing a desiccant-containing resin composition pellet of the present invention can efficiently produce resin composition pellets having EVOH as a main component and containing a desiccant and having a low water content.

1 Kneading machine 2 Strand 4 Water 5a, 5b Air soccer

Claims (2)

A method for continuously producing resin composition pellets containing a saponified ethylene-vinyl ester copolymer as a main component and containing a desiccant, wherein the resin composition is melt-kneaded with a kneader and pressed into a strand shape. A step of taking out, a step of water-cooling the extruded strand while moving in water, a step of removing water from the surface of the water-cooled strand using at least one of air soccer and an air knife , A desiccant-containing resin composition pellet characterized in that the time (T) required for movement of the strand in water in the water cooling step satisfies the following formula (1): Manufacturing method.
0.45 seconds ≦ T ≦ 1.6 seconds (1)   The method for producing a desiccant-containing resin composition pellet according to claim 1, wherein the water removing step uses a plurality of at least one of air soccer and air knife.

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