JP2013010246A - Method of producing polymer pellet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a polymer pellet made of an ionomer of an ethylene-unsaturated carboxylic acid copolymer or a saponification product of an ethylene-unsaturated carboxylic acid ester copolymer, the polymer pellet produced being hard to generate a silver-gray streak called "silver" when used for injection molding and being hard to generate a film break when used for forming an inflation film.SOLUTION: The method of producing the polymer pellet 22 includes steps of: heating the ionomer obtained by neutralizing a part or all of acid groups of the ethylene-unsaturated carboxylic acid copolymer with metal ions or the saponification product obtained by saponifying a part or all of ester groups of the ethylene-unsaturated carboxylic acid ester copolymer with metal ions, and melt-kneading it by a melt-extruder; extruding the kneaded product through a die 1 at a front end of the melt-extruder to form a melt strand 2; supplying the melt strand onto metal belts 3, 4 as metal belt coolers to cool and solidify the metal strand; and fragmenting the solidified metal strand.

Description

  The present invention relates to an ionomer obtained by neutralizing part or all of the acid group of an ethylene / unsaturated carboxylic acid copolymer with a metal (ion), or one of ester groups of an ethylene / unsaturated carboxylic acid ester copolymer. The present invention relates to a method for producing saponified polymer pellets, part or all of which is saponified with a metal (ion), an inflation film using the polymer pellets, and an injection molded article.

  Conventionally, ionomers of ethylene / unsaturated carboxylic acid copolymers exhibit characteristic properties based on ionic crosslinking, and are widely used alone or in combination with other resins (see, for example, Patent Document 1). . In addition, alkali saponified products of ethylene / unsaturated carboxylic acid esters have been attracting attention in recent years because of their excellent miscibility with other resins (for example, Patent Document 2). When these ionomers or alkali saponified products are combined with other resins, it is general to mix polymer pellets of the respective resins and mold them.

Conventionally, a strand cut method and an underwater cut method are known as methods for producing polymer pellets (for example, Patent Document 3).
The strand cut method is a method in which a strand extruded from a die of a melt extruder is solidified by cooling with a water bath, and then the strand is cut to a desired length with a pelletizer or the like to obtain polymer pellets. According to this method, cylindrical polymer pellets are obtained.

  On the other hand, the underwater cut method is a method in which a strand extruded from a die of a melt extruder is cut by a cutter disposed in the vicinity of the die, and the polymer after cutting is immersed in cooling water to obtain polymer pellets. According to this method, approximately spherical polymer pellets are obtained.

JP-A-6-287223 JP 2010-6872 A JP 2004-136661 A

  An ionomer in which part or all of the acid group of the ethylene / unsaturated carboxylic acid copolymer is neutralized with a metal (ion), or part or all of the ester group of the ethylene / unsaturated carboxylic acid ester copolymer When saponified polymer pellets saponified with metal (ions) are produced by the strand cut method or the underwater cut method, so-called silver is formed on the surface of the injection molded body using this polymer pellet as a part of the molding resin raw material. The problem of the occurrence of silver-white streaks called "is easy to occur. In addition, when an inflation film is produced using the polymer pellet as a part of the molding resin raw material, a problem that a film breaks easily occurs during the film molding.

  The ionomer formed by neutralizing some or all of the acid groups of the ethylene / unsaturated carboxylic acid copolymer with silver (ion) is the silver that occurs in the above-mentioned injection-molded product and the film cracking that occurs during the production of an inflation film. Alternatively, it is assumed that a part or all of the ester groups of the ethylene / unsaturated carboxylic acid ester copolymer are generated by moisture contained in a saponified product obtained by saponification with a metal (ion). That is, silver and film cracking are likely to occur in a molded body formed by polymer blend alone or by dry blending the polymer pellet and another resin.

  In addition, an ionomer in which part or all of the acid group of the ethylene / unsaturated carboxylic acid copolymer is neutralized with a metal (ion), or part of the ester group of the ethylene / unsaturated carboxylic acid ester copolymer or A saponified product that is saponified entirely with metal (ions) is easy to absorb moisture, and further has a property that moisture does not easily escape once it absorbs moisture. For this reason, when polymer pellets are produced by the strand cutting method or the underwater cutting method, moisture is taken into the ionomer or saponified product during water cooling, and this moisture is broken by silver or film cracking during the subsequent molding process. It is presumed that it will cause.

  Therefore, it is conceivable to sufficiently dry the polymer pellets obtained by the strand cut method or the underwater cut method with a thermostat before use. However, in this method, it is necessary to dry the polymer pellets in a constant temperature oven for a long time, and there is a problem that time loss and heat energy consumption are large.

  The present invention has been made in view of the above problems, and is an ethylene / unsaturated carboxylic acid copolymer that is unlikely to generate silver when used in injection molding and that is unlikely to cause film cracking during the production of an inflation film. An ionomer in which some or all of the acid groups are neutralized with a metal (ion), or a part or all of the ester groups of an ethylene / unsaturated carboxylic acid ester copolymer are saponified with a metal (ion). It is an object of the present invention to provide a method for producing saponified polymer pellets.

In the case of polymer pellets produced by cooling the above-described molten strand with a metal belt cooler, the present inventors are unlikely to generate silver in an injection-molded product using the same, and when producing an inflation film using the same, It was found that film cracking hardly occurs. In addition, the polymer pellets obtained by this production method do not need to be dried for a long time before use, and have also been found to have advantages such as less time loss and heat energy consumption during injection molding and inflation film production. It was.
The present invention relates to the following method for producing polymer pellets.

[1] An ionomer obtained by neutralizing part or all of the acid group of the ethylene / unsaturated carboxylic acid copolymer with a metal (ion), or part of the ester group of the ethylene / unsaturated carboxylic acid ester copolymer Alternatively, a saponified product entirely saponified with metal (ion) is heated in a melt extruder and melt kneaded, and the kneaded product is extruded from a die at the tip of the melt extruder to form a melt strand. A method for producing polymer pellets, comprising: a step; supplying the molten strand onto a metal belt of a metal belt cooler; cooling the solidified strand to solidify; and fragmenting the solidified molten strand.
[2] The method for producing polymer pellets according to [1], wherein the fragmentation is performed by a crusher.
[3] The method for producing polymer pellets according to [1], wherein the fragmentation is performed by cutting with a cutter.
[4] An inflation film obtained by dry blending a polymer pellet produced by the method for producing a polymer pellet according to any one of [1] to [3] and another resin, or the polymer pellet alone.
[5] Injection molding body of a mixture obtained by dry blending polymer pellets produced by the method for producing polymer pellets according to any one of [1] to [3] and other resin, or the polymer pellet alone .

  According to the present invention, an ionomer in which part or all of the acid groups of an ethylene / unsaturated carboxylic acid copolymer are efficiently neutralized with a metal (ion), or an ethylene / unsaturated carboxylic acid ester copolymer It is possible to produce saponified polymer pellets in which some or all of the ester groups are saponified with a metal (ion). Further, the polymer pellets that are obtained are less likely to cause poor appearance when used in an injection-molded product, and even when used for an inflation film, film cracking of the film is less likely to occur during film formation.

It is a figure which shows an example of the metal belt cooler used for the manufacturing method of the polymer pellet of this invention.

1. Production method of polymer pellets The production method of polymer pellets of the present invention comprises an ionomer in which some or all of the acid groups of an ethylene / unsaturated carboxylic acid copolymer are neutralized with a metal (ion), or ethylene / unsaturation. A step of heating and melt-kneading a saponified product in which part or all of the ester groups of the carboxylic acid ester copolymer are saponified with a metal (ion) in a melt extruder; Extruding from a die at the tip to form a molten strand, supplying the molten strand onto a metal belt of a metal belt cooler, cooling the molten strand to solidify, and fragmenting the solidified molten strand The process of carrying out.

(Melting and kneading process)
In the present invention, an ionomer obtained by neutralizing some or all of the acid groups of an ethylene / unsaturated carboxylic acid copolymer with a metal (ion) (hereinafter also simply referred to as “ionomer”), or an ethylene / unsaturated carboxylic acid. A saponified product in which part or all of the ester groups of the acid ester copolymer are saponified with a metal (ion) (hereinafter also simply referred to as “saponified product”) is heated and melt-kneaded in a melt extruder. Only the ionomer or only the saponified product may be melt-kneaded. For example, a mixture of an ionomer or saponified product and another resin may be melt-kneaded.

  The melt extruder used for melt kneading is not particularly limited as long as the ionomer or saponified product can be kneaded in a molten state and the kneaded product can be extruded from a die at the tip of the melt extruder. For example, either a single screw type or a twin screw type melt extruder may be used, but a twin screw type melt extruder is more preferable because kneading can be sufficiently performed. The presence or absence of a vent in the melt extruder is not particularly limited, but a melt extruder having a vent is more preferable because it can remove air, volatile components, and the like contained in the kneaded product.

  The temperature at the time of melt kneading may be a temperature at which the ionomer or saponified material melts, and is preferably 100 ° C to 300 ° C, more preferably 200 ° C to 250 ° C. When the lower limit is exceeded, the ionomer or saponified product can be efficiently kneaded. When the upper limit is not reached, melt kneading is possible without thermally decomposing the ionomer or saponified product.

・ Ionomer of ethylene / unsaturated carboxylic acid copolymer Ionomer of ethylene / unsaturated carboxylic acid copolymer is an ethylene / unsaturated carboxylic acid copolymer obtained by copolymerizing ethylene and unsaturated carboxylic acid. A part or all of the acid group (carboxyl group) of, for example, alkali metals such as lithium, sodium, potassium, rubidium or hydroxides, carbonates, bicarbonates of metals other than alkali metals such as zinc and magnesium Obtained by neutralization with Among these types of metals, alkali metals, particularly those having a large atomic radius such as potassium and rubidium are preferred because the effects of the present invention are more clearly shown. In the following description, potassium will be described as an example, but it goes without saying that other metal species described here can be similarly applied.

  The ionomer used in this step may be an ionomer prepared in advance outside the melt extruder, or obtained by reacting the ethylene / unsaturated carboxylic acid copolymer with the potassium compound in the melt extruder. It may be an ionomer.

  The unsaturated carboxylic acid in the ethylene / unsaturated carboxylic acid copolymer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, maleic anhydride, monomethyl maleate and the like, and acrylic acid or methacrylic acid is particularly preferable.

  The amount of the unsaturated carboxylic acid monomer component relative to the total monomer components contained in the ethylene / unsaturated carboxylic acid copolymer is preferably 5 to 40% by mass, more preferably 10 to 35% by mass. By making unsaturated carboxylic acid content into the said range, the antistatic property and workability of potassium ionomer are excellent, and it becomes possible to use potassium ionomer for a wide use.

The ethylene / unsaturated carboxylic acid copolymer may be a copolymer of only ethylene and unsaturated carboxylic acid, but it is a copolymer of ethylene, unsaturated carboxylic acid, and other monomer components. It may be what you did.
Examples of other monomer components include esters of acrylic acid and methacrylic acid, vinyl acetate, and the like. Specific examples of the esters of acrylic acid and methacrylic acid include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, methyl methacrylate, and isobutyl methacrylate.

  The amount of other monomer components with respect to the total monomer components contained in the ethylene / unsaturated carboxylic acid copolymer is preferably 40% by mass or less, and more preferably 20% by mass or less. If the amount of other monomer components is excessive, the mechanical strength of the ionomer may be reduced.

  Further, the content of potassium ions in the potassium ionomer is preferably 0.4 mmol or more, and particularly preferably 1.0 to 3.0 mmol, per 1 g of ionomer.

  In addition, the potassium ionomer used in this step has a melt flow rate of 0.01 to 100 g / 10 at 190 ° C. and a load of 2,160 g (according to JIS K7120-1999) from the viewpoint of melt extrudability and workability. Minute is preferable, and 0.05 to 10 g / 10 minutes is more preferable.

・ Saponified ethylene / unsaturated carboxylic acid ester copolymer Saponified ethylene / unsaturated carboxylic acid ester copolymer is ethylene / unsaturated carboxylic acid obtained by copolymerizing ethylene and unsaturated carboxylic acid ester. It is obtained by saponifying some or all of the ester groups of the copolymer ester with a metal (ion) using a metal hydroxide such as potassium hydroxide. The kind of metal (ion) can be the same as the alkali metal used for the above-mentioned ionomer. In the following description, potassium is taken as an example, but it goes without saying that other metal species can be similarly applied.

  The saponified product used in this step may be a saponified product prepared in advance outside the melt extruder, and the ethylene / unsaturated carboxylic acid ester copolymer is reacted with potassium hydroxide in the melt extruder. The saponified product obtained may be used.

  Examples of the unsaturated carboxylic acid in the ethylene / unsaturated carboxylic acid ester include acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, fumaric acid, maleic acid, maleic acid, maleic anhydride, itaconic acid, and itaconic anhydride. Acrylic acid or methacrylic acid is particularly preferable.

  The ester group in the unsaturated carboxylic acid ester is preferably an alkyl ester group. The alkyl group in the alkyl ester group is preferably an alkyl group having 1 to 12 carbon atoms. For example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a secondary butyl group, 2- Examples thereof include an ethylhexyl group and isooctyl. In particular, a methyl group, an ethyl group, a normal butyl group, and an isobutyl group are preferable.

  The ethylene / unsaturated carboxylic acid ester copolymer is particularly preferably an ethylene (meth) acrylic acid ester copolymer. Among them, an ethylene / methyl acrylate copolymer, an ethylene / ethyl acrylate copolymer, an ethylene / acrylic acid normal copolymer, and the like. Butyl copolymer, ethylene / isobutyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl methacrylate copolymer, ethylene / normal butyl copolymer, ethylene / methacrylic acid An isobutyl copolymer is preferred.

  5-50 mass% is preferable and, as for the quantity of the monomer component of unsaturated carboxylic acid ester with respect to all the monomer components contained in an ethylene-unsaturated carboxylic acid ester copolymer, 20-35 mass% is more preferable. When the amount of the monomer component of the unsaturated carboxylic acid ester component is within this range, the balance of miscibility between the other resin and the saponified product when mixed with another resin is excellent.

  Further, the potassium ion content in the saponified product is preferably 0.1 to 5.8 mmol per 1 g of saponified product, and particularly preferably 1.0 to 3.0 mmol.

  The saponified product used in this step preferably has a melt flow rate of 0.01 to 100 g / 10 min at 230 ° C. and 10 kg load (conforming to JIS K7120-1999) in terms of melt extrudability and workability. 0.1 to 50 g / 10 min is more preferable.

-Other resin As mentioned above, at this process, it is possible to melt-knead combining the said ionomer or the said saponified material, and another resin. By combining other resins, the melt extrudability of the ionomer or saponified product can be improved.

  Examples of other resins include olefin homopolymers, copolymers of two or more olefins, and copolymers of olefins and unsaturated esters. More specifically, low density polyethylene, linear low density polyethylene, medium density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, 1,2-polybutadiene, ethylene / vinyl acetate copolymer Ethylene / acrylic acid ester copolymer, ethylene / methacrylic acid ester copolymer, and the like.

  As for the usage-amount of other resin, 50 mass parts or more of a minimum is preferable with respect to 100 mass parts of total amounts of other resin, and ionomer or saponified substance, and 99 mass parts or less is preferable for an upper limit.

(Melting strand forming process)
The kneaded material melt-kneaded in the above-described melt-kneading step is continuously extruded from a die at the tip of the melt extruder to form a melt strand. The die may have a single hole or may have a plurality of holes.

  The shape of the hole of the die is appropriately selected according to the cross-sectional shape of the target melt strand, and may be any shape such as a circle, an ellipse, a rhombus, and a rectangle.

(Melting strand solidification process)
The molten strand extruded from the die is supplied onto the metal belt of the metal belt cooler, and is cooled and solidified by the metal belt. The metal belt cooler has a metallic endless transport belt (metal belt), and this endless transport belt is cooled by a cooling mechanism provided on the inner peripheral side. The endless transport belt is covered on the outer peripheral side of the endless transport belt. The cooling object is supplied to cool the object to be cooled.

The type of the metal belt cooler is not particularly limited. For example, as shown in FIG. 1, a molten strand 2 extruded from a die 1 of a melt extruder is sandwiched between two metal belts 3 and 4 and the belt ends. Can be transported. The two metal belts 3 and 4 are cooled by cooling water jetted from the cooling mechanisms 5 and 6. In the metal belt cooler, since the cooling water does not come into contact with the molten strand 2 and the molten strand 2 is cooled via the metal belts 3 and 4, there is no possibility that the molten strand 2 absorbs moisture when the molten strand 2 is cooled.
The metal belt cooler may be provided with a press roller 11 for rolling the molten strand 2 as shown in FIG.

  Further, the metal belt cooler is not limited to the one shown in FIG. 1. For example, a single belt cooler that cools the molten strand by a single metal belt may be used. However, a double cooler system in which the molten strand is sandwiched from two directions and cooled is preferable from the viewpoint of cooling efficiency and the like.

(Fragmentation process)
The molten strand solidified by the above-described molten strand solidification step is cut so as to be the length of the target polymer pellet, or the molten strand is crushed with a crusher and fragmented. FIG. 1 shows an example in which the molten strand 2 is crushed by a crusher 21 to form polymer pellets 22.

  When cutting the molten strand, the molten strand is usually cut so as to be orthogonal to the length direction of the solidified molten strand. According to this method, it is possible to obtain a pellet having a uniform length such as a columnar shape or a prismatic shape. The pellet length is appropriately selected according to the use of the polymer pellet and the like, but is usually about 1 to 10 mm, preferably about 2 to 5 mm.

  The apparatus used for cutting the molten strand is not particularly limited as long as it includes a cutter for cutting the molten strand. Examples thereof include a pelletizer that cuts the molten strand with a rotary blade and a fixed blade.

  On the other hand, when the molten strand is crushed, it is possible to obtain particulate pellets having a desired average particle diameter. The average particle size of the granular polymer pellets obtained by crushing is usually preferably about 1 to 10 mm, more preferably 2 to 5 mm. The average particle diameter is a median diameter when a cumulative distribution is obtained using a sieving method according to JIS K0069.

  Examples of the crusher include a shredder, jaw crusher, cone crusher, hammer crusher, roll crusher, roll mill, stamp mill, hammer mill, cutter mill, rod mill, cascade mill, speed mill, oscillator type granulator, and the like.

(Other)
The polymer pellets produced according to the present invention are preferably stored in a low humidity environment in order to prevent moisture absorption during storage. Examples of the storage method include a method of storing polymer pellets in a moisture-proof bag or container.

2. Inflation film and injection-molded article The inflation film or injection-molded article of the present invention is obtained by subjecting a mixture obtained by dry blending polymer pellets produced by the above-described method for producing polymer pellets and other resins, or the polymer pellets alone to inflation molding. Or obtained by injection molding.

(Other resins)
There is no restriction | limiting in particular as other resin which can be mixed with the above-mentioned polymer pellet. Such resins include high-pressure polyethylene, medium / high density polyethylene, linear low density polyethylene, linear low density polyethylene having a density of 940 kg / m ³ or less, and ethylene homopolymers such as ultra-low density polyethylene. Copolymer of ethylene and α-olefin having 3 to 12 carbon atoms; polypropylene; poly-1-butene; poly-4-methyl-1-pentene; ethylene-vinyl acetate copolymer; ethylene and, for example, acrylic acid; Copolymers with unsaturated carboxylic acids such as methacrylic acid, monoethyl maleate, maleic anhydride; ethylene and, for example, methyl acrylate, ethyl acrylate, isobutyl acrylate, nbutyl acrylate, 2-ethylhexyl acrylate , 1 type or 2 types such as methyl methacrylate, glycidyl methacrylate, dimethyl maleate A copolymer of the above unsaturated carboxylic acid ester; ethylene, a copolymer of the unsaturated carboxylic acid and the unsaturated carboxylic acid ester; ethylene, carbon monoxide, and the unsaturated carboxylic acid ester Copolymerization with vinyl acetate; Olefin polymers such as polyolefin elastomers; Styrene polymers such as polystyrene, high impact polystyrene, ABS resin, rubber reinforced styrene resins; polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate , Polyethylene naphthalate, cyclohexanedimethanol copolymerized polyethylene terephthalate, polyesters such as polyester elastomers, polycarbonates, polymethyl methacrylate, and the like. These may be used alone or in combination of two or more.

  As for the usage-amount of a polymer pellet and other resin, 50 mass parts or more of a minimum is preferable with respect to 100 mass parts of total amounts of other resin and an ionomer, or a saponified material, and 99 mass parts or less is preferable for an upper limit.

(Additive)
In addition to polymer pellets and other resins, optional additives such as antioxidants, weathering stabilizers, light stabilizers, UV absorbers, lubricants, slip agents, pigments, dyes, crosslinkers, as necessary A foaming agent, a tackifier, etc. can be added.

(Inflation film and injection-molded body manufacturing method)
When polymer pellets are mixed with other resins and additives, they are dry blended. The method of dry blending is not particularly limited, and for example, mixing can be performed using a Henschel mixer, a rotary mixer, or the like.

  In addition, the above-described polymer pellets or a mixture thereof can be used without drying with a thermostat or the like.

  The method of forming the inflation film can be the same as the method of forming a general inflation film. For example, the above polymer pellet alone or a mixture thereof is melted and extruded into an annular shape, and the resin extruded into the annular shape is taken from the inside. For example, a method may be used in which air is blown to inflate the resin and wind it up.

  The molding method of the injection molded body can be the same as a general injection molding method. For example, the above-described polymer pellet alone or a mixture thereof is melted, and an injection pressure is applied and pressed into a mold to form the polymer pellet.

(Use of blown film or injection molded product)
There is no restriction | limiting in particular in the film thickness of the inflation film of this invention, According to a use, it selects suitably, Usually, it can be about 10-100 micrometers. The inflation film can be used for a wide range of applications such as various packaging materials such as foods and medicines, and wallpaper.

  Moreover, the injection molded body of the present invention hardly generates silver on the surface, and can be used for a wide range of applications such as containers, building materials, and automobile exterior parts.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. Hereinafter, the raw material used for the Example and the comparative example is shown.

(material)
-Ethylene / methyl acrylate copolymer (EAC): methyl acrylate (MA) content: 30% by mass, MFR (melt flow rate): 15 g / 10 min (190 ° C. × 2160 g load)
-Potassium ionomer (EM-K) of ethylene / methacrylic acid copolymer: methacrylic acid content; 15% by mass, MFR (melt flow rate) 0.1 g / 10 min (190 ° C. × 2160 g load)
・ Low density polyethylene (LDPE); Melt flow rate (MFR): 3.7 g / 10 min (190 ° C. × 2160 g load)

Example 1
10 kg of ethylene / methyl acrylate copolymer (EAC) and 780 g of KOH were fed into a melt extruder and reacted while being melt kneaded in the melt extruder to obtain a saponified ethylene / methyl acrylate copolymer.
The potassium ion concentration present in the form of potassium acrylate in this saponified product was 1.4 mmol / g. The degree of saponification was 40%.

  The molten strand was extruded from the die of the melt extruder onto a metal belt of a double metal belt cooler (manufactured by Nippon Steel Belt Conveyor Co., Ltd .; steel belt double cooler), and the molten strand was cooled by the metal belt cooler. The solidified molten strand was cut by a pelletizer disposed at the end of a double metal belt cooler to obtain cylindrical polymer pellets.

  2 kg of the obtained polymer pellets and 8 kg of low density polyethylene (LPDE) were mixed and subjected to inflation molding with an inflation molding machine to obtain an inflation film having a thickness of 50 μm.

  Further, 2 kg of the obtained polymer pellets and 8 kg of low density polyethylene (LPDE) were mixed and injection molded by an injection molding machine to obtain an injection molded body of 150 mm × 80 mm × thickness 2 mm.

  The presence or absence of film cracking during inflation molding and the obtained injection-molded product were confirmed visually. The results are shown in Table 1.

(Example 2)
Inflation molding and injection molding were performed in the same manner as in Example 1 using an ethylene / methacrylic acid copolymer potassium ionomer (EM-K) having a metal ion concentration of 1.2 mmol / g. The presence or absence of film cracking during inflation molding and the presence or absence of silver in the obtained injection-molded product were confirmed visually. The results are shown in Table 1.

(Comparative Example 1)
Polymer pellets were produced in the same manner as in Example 1 except that the molten strand was cooled in a water bath. Without drying the obtained polymer pellets, the presence or absence of film cracking during inflation molding and the presence or absence of silver in the obtained injection-molded product were visually confirmed. The results are shown in Table 1.

(Reference example)
An inflation film and an injection-molded body were produced in the same manner as in Example 1 using only low-density polyethylene (LDPE). The presence or absence of film cracking during inflation molding and the presence or absence of silver in the obtained injection-molded product were confirmed visually. The results are shown in Table 1.

  In the blown film and the injection molded article using the polymer pellet produced by the production method of the present invention, no film cracking or silver occurred (Examples 1 and 2). On the other hand, in the polymer pellet (Comparative Example 1) produced by a general strand cutting method (melted strand was water-cooled), film cracking occurred during the production of the inflation film, and silver was also produced in the injection molded product. In addition, low density polyethylene is a hydrophobic resin, and film cracking did not occur during the production of an inflation film using the resin, and silver was not generated in the obtained injection-molded product (Reference Example).

  The inflation film using the polymer pellets obtained by the method for producing polymer pellets of the present invention and the injection-molded product are free from film cracking during film molding and the resulting injection-molded product is free of silver and has good appearance. is there. Therefore, it can be used for a wide range of applications such as various packaging materials, containers, building materials, and automobile exterior parts.

DESCRIPTION OF SYMBOLS 1 Dice 2 Molten strand 3, 4 Metal belt 5, 6 Cooling mechanism 11 Press roller 21 Crusher 22 Polymer pellet

Claims (5)

  An ionomer in which part or all of the acid group of the ethylene / unsaturated carboxylic acid copolymer is neutralized with a metal (ion), or part or all of the ester group of the ethylene / unsaturated carboxylic acid ester copolymer A step of heating and melting and kneading a saponified product saponified with a metal (ion) in a melt extruder; a step of extruding the kneaded product from a die at the tip of the melt extruder to form a melt strand; and A method for producing polymer pellets, comprising: supplying the molten strand onto a metal belt of a metal belt cooler; cooling the molten strand to solidify; and fragmenting the solidified molten strand.   The method for producing polymer pellets according to claim 1, wherein the fragmentation is performed by a crusher.   The method for producing polymer pellets according to claim 1, wherein the fragmentation is performed by cutting with a cutter.   The inflation film of the polymer pellet manufactured by the manufacturing method of the polymer pellet as described in any one of Claims 1-3, and the dry blend of the other resin, or the said polymer pellet single-piece | unit.   An injection molding body of a mixture obtained by dry blending a polymer pellet produced by the method for producing a polymer pellet according to any one of claims 1 to 3 and another resin, or the polymer pellet alone.

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