JP5748489B2 - Method for producing resin composition - Google Patents

Description

The present invention relates to a method for producing a resin composition, and in particular, a system comprising a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 60 mol% as a main component having a small ethylene content of 70 mol% or more. The present invention relates to a method for producing a resin composition in which an ethylene-vinyl acetate copolymer saponified product (B) is melt-kneaded with a large discharge amount extruder.
In particular, the present invention relates to a method for producing a resin composition for silage film.

In general, saponified ethylene-vinyl acetate copolymer (hereinafter abbreviated as EVOH) is excellent in transparency, antistatic properties, oil resistance, solvent resistance, gas barrier properties, fragrance retention, etc. , Bending fatigue resistance, stretchability, thermoformability, heat sealability, moisture absorption or gas barrier properties at the time of water absorption are low.
For this reason, various resins and additives are blended depending on the purpose, and while maintaining EVOH characteristics such as gas barrier properties, fragrance retention, and food discoloration prevention properties, bending fatigue resistance, thermoformability, heat sealing In some cases, it is used in various packaging applications to compensate for the drawbacks of EVOH such as safety and moisture resistance.

For example, a resin composition that can maintain excellent gas barrier properties against severe bending fatigue, vibration fatigue, and drop impact at low temperatures, and is effective as a laminated packaging material to prevent deterioration of the package The resin composition has a specific laminate structure including a physical layer, and the resin composition is an olefin-carboxylic acid vinyl ester copolymer and / or a saponified product 1 to 100 parts by weight of a saponified ethylene-vinyl acetate copolymer. A laminated packaging material containing 100 parts by weight is known (for example, see Patent Document 1).
Such ethylene-vinyl acetate copolymer saponified products are described with an ethylene content of 20 to 60 mol%, and the olefin-carboxylic acid vinyl ester copolymer and / or saponified products thereof have an ethylene content of 70 mol. % Of ethylene-vinyl acetate copolymer saponified product is described.

Japanese Patent Laid-Open No. 2001-79999

However, an ethylene-vinyl acetate copolymer saponified product (A) having an ethylene content of 20 to 60 mol% (hereinafter sometimes referred to as EVOH resin (A)) and an ethylene-acetic acid having an ethylene content of 70 mol% or more. Since the vinyl copolymer saponified product (B) (hereinafter sometimes referred to as EVA saponified product (B)) is not sufficiently compatible, there is a tendency that a uniform mixture cannot be obtained when both are mixed. .
Therefore, it is difficult to find a problem when using a small extruder (low discharge amount extruder) in which resins are mechanically kneaded well, but a large industrial extruder (large discharge amount extruder). In the case of mass production, the surging occurs because the resins are hardly kneaded mechanically, and the strands are broken, resulting in a decrease in productivity. When extrusion is performed using an extruder, pulsation may occur in the flow of molten resin in the system, and the operation of the extruder may become unstable. Such behavior is generally called surging.

As a result of intensive studies in view of the above circumstances, the present invention has revealed that an ethylene-vinyl acetate copolymer saponified product (A) having an ethylene content of 20 to 60 mol% and an ethylene-vinyl acetate copolymer having an ethylene content of 70 mol% or more. Including a saponified coal (B) and a carboxyl group-containing ethylene-vinyl acetate copolymer (C) (hereinafter sometimes referred to as acid-modified EVA (C)), with respect to 100 parts by weight of the EVOH resin (A) By adopting a resin composition containing 2 to 5 parts by weight of acid-modified EVA (C), even when melt-kneading with an extruder having a large discharge rate of 100 to 500 kg / hr Surging is suppressed, strand breakage does not occur, and industrial production can be performed with excellent productivity.

  The EVA saponified product (B) is obtained by saponifying a vinyl acetate component of an ethylene-vinyl acetate copolymer having an ethylene content as high as 70 mol% or more. The EVOH resin (A) As in the case of EVOH resin (A), it does not have a high gas barrier property due to its high ethylene content. Accordingly, the EVA saponified product (B) is recognized as a completely different resin from the EVOH resin (A) by those skilled in the art.

  The EVA saponified product (B) is also clearly different from the ethylene-vinyl acetate copolymer (generally called EVA resin, which is a flexible resin) in terms of the presence or absence of hydroxyl groups. Since EVA saponified product (B) has a hydroxyl group, it has a higher polarity than EVA resin not having a hydroxyl group, while it is characterized by poor flexibility. For those skilled in the art, EVA resin and EVA saponified product (B) It is recognized as a completely different resin.

  The carboxyl group-containing ethylene-vinyl acetate copolymer (C) is obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an ethylene-vinyl acetate copolymer having an ethylene content of 70 mol% or more. It is obtained. Such acid-modified EVA (C) has no hydroxyl group, does not have a high gas barrier property, and is recognized as a resin completely different from the EVOH resin (A) and the EVA saponified product (B).

That is, the gist of the present invention is that an ethylene-vinyl acetate copolymer saponified product (A) having an ethylene content of 20 to 60 mol% and an ethylene-vinyl acetate copolymer saponified product having an ethylene content of 70 mol% or more ( In melt-kneading B) with an extruder having a discharge rate of 100 to 500 kg / hr, 2 to 5 parts by weight of the carboxyl group-containing ethylene-vinyl acetate copolymer (C) with respect to 100 parts by weight of (A) above. It exists in the manufacturing method of the resin composition characterized by containing.

  In the resin composition in which the EVA saponification product (B) is blended with the main component EVOH resin (A), the presence of a specific amount of acid-modified EVA (C) makes the EVA saponification product (B) uniform in the EVOH resin. Can be dispersed. Since the unevenness of the resin composition is thereby eliminated, surging during production and strand breakage are eliminated, and molded articles such as pellets and films having good shapes can be obtained with excellent productivity even during mass production. .

  Further, when EVA saponified product (B) is blended to give flexibility to EVOH resin (A), EVA saponified product (B) tended to be not uniformly dispersed in EVOH resin (A). By containing an ethylene-vinyl acetate copolymer (C) containing a specific amount of carboxyl group in the resin composition, an EVA saponification product (EV) in the EVOH resin (A) (through acid-modified EVA (C)) ( A resin composition having a good melt flow rate (MFR) for melt molding may be obtained because the dispersion state of B) is good.

Hereinafter, although it demonstrates in detail about the structure of this invention, these show an example of a desirable embodiment.
First, the resin composition used in the present invention will be described.

<Resin composition>
The resin composition of the present invention comprises an ethylene-vinyl acetate copolymer saponified product (A) having an ethylene content of 20 to 60 mol% and an ethylene-vinyl acetate copolymer saponified product having an ethylene content of 70 mol% or more ( B) and a carboxyl group-containing ethylene-vinyl acetate copolymer (C), and a resin composition containing 2 to 5 parts by weight of (C) with respect to 100 parts by weight of (A).
Hereinafter, each component will be described in order.

[EVOH resin (A)]
The EVOH resin (A) as the main component of the resin composition is a water-insoluble resin, and can be obtained by saponifying a copolymer of ethylene and vinyl acetate. The ethylene-vinyl acetate copolymer is produced by any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, etc., and saponification of the ethylene-vinyl acetate copolymer can also be performed by a known method.

  The ethylene content of the EVOH resin (A) used in the resin composition of the present invention means the content of ethylene structural units measured based on ISO 14663, and is 20 to 60 mol%. And preferably it is 25-55 mol%, More preferably, it is 35-50 mol%, Most preferably, it is 38-48 mol%. When there is too little content of an ethylene structural unit, it exists in the tendency for the softness | flexibility of a film to fall. On the other hand, when the content of the ethylene structural unit is too high, the gas barrier property tends to be insufficient.

  Further, the saponification degree of the vinyl acetate component is a value measured based on JIS K6726 (however, EVOH resin is a solution uniformly dissolved in water / methanol solvent) and is usually 95 mol% or more, more preferably. Is 95 to 100 mol%, more preferably 98 to 100 mol%, particularly preferably 99 to 100 mol%. This is because as the saponification degree decreases, the gas barrier property tends to decrease.

  Further, the melt flow rate (MFR) of the EVOH resin (A) is usually 0.1 to 100 g / 10 minutes, preferably 0.5 to 50 g / 10 minutes under the conditions of 210 ° C. and a load of 2160 g. Particularly preferably, it is 1 to 20 g / 10 min. If the MFR value is too small, the screw torque or resin pressure tends to be too high during extrusion molding, or vertical streaks tend to occur in the resulting film. On the other hand, if the MFR value is too large, the extrusion moldability is low. There is a tendency that the film becomes unstable or the film thickness of the obtained film varies.

As the EVOH resin (A) used in the resin composition of the present invention, two or more kinds different in ethylene content, saponification degree, and MFR may be mixed and used as long as the EVOH resin satisfies the above requirements. .
In addition, the EVOH resin used in the present invention includes a small amount of α-olefin such as propylene, isobutene, α-octene, α-dodecene, α-octadecene, 3-buten-1-ol, 4 in the copolymer. -Hydroxy group-containing α-olefins such as penten-1-ol, 3-butene-1,2-diol, etc., hydroxy group-containing α-olefin derivatives such as esterified products, acylated products, unsaturated carboxylic acids or salts thereof Copolymers of partially alkyl esters, fully alkyl esters, nitriles, amides, anhydrides, unsaturated sulfonic acids or salts thereof, vinyl silane compounds, vinyl chloride, styrene, etc. may be used. Furthermore, it may be “post-modified” such as urethanization, acetalization, cyanoethylation, oxyalkyleneation, and epoxidation.
In particular, an EVOH resin copolymerized with a hydroxy group-containing α-olefin is preferable in terms of good moldability and stretchability, and among them, an EVOH resin having a 1,2-diol in the side chain is preferable.

  The EVOH resin (A) used in the present invention may contain a heat stabilizer generally blended with the EVOH resin as long as the effects of the present invention are not hindered. Organic acids such as acetic acid, propionic acid, butyric acid, lauric acid, stearic acid, oleic acid, behenic acid or alkali metal salts thereof (sodium, potassium, etc.) for the purpose of improving various physical properties such as thermal stability during molding , Salts of alkaline earth metal salts (calcium, magnesium, etc.), zinc group metal salts (zinc, etc.); or inorganic acids such as sulfuric acid, sulfurous acid, carbonic acid, phosphoric acid, boric acid, or alkali metal salts thereof ( Sodium, potassium, etc.), alkaline earth metal salts (calcium, magnesium, etc.), zinc group metal salts (zinc, etc.) and other additives may be added. Among these, it is particularly preferable to add boron compounds, acetates, and phosphates including acetic acid, phosphoric acid, boric acid and salts thereof.

  When acetic acid is added, the amount added is usually 0.001 to 1 part by weight, preferably 0.005 to 0.2 part by weight, particularly preferably 0.01 to 100 parts by weight of EVOH resin (A). 0.1 parts by weight. If the amount of acetic acid added is too small, the effect of acetic acid content tends not to be sufficiently obtained, and conversely if too large, it tends to be difficult to obtain a film having a uniform thickness and appearance.

  When phosphoric acid is added, the amount added is usually 0.0005 to 0.1 with respect to 100 parts by weight of EVOH resin (A) (analyzed by thermal decomposition with sulfuric acid and nitric acid and analyzing phosphate groups by atomic absorption method). Parts by weight, preferably 0.001 to 0.05 parts by weight, particularly preferably 0.002 to 0.03 parts by weight. If the amount of phosphoric acid added is too small, the phosphoric acid-containing effect tends to be insufficient, and conversely if too large, it tends to be difficult to obtain a film having a uniform thickness and appearance.

  Moreover, when adding a boron compound, the addition amount is 0.001-1 weight part normally by boron conversion (after ashing and analyzing by ICP emission spectrometry) with respect to 100 weight part of EVOH resin (A). Yes, preferably 0.002 to 0.2 parts by weight, particularly preferably 0.005 to 0.1 parts by weight. If the addition amount of the boron compound is too small, the effect of adding the boron compound may not be sufficiently obtained. Conversely, if the addition amount is too large, it tends to be difficult to obtain a film having a uniform thickness and appearance.

  The amount of acetate and phosphate (including hydrogen phosphate) added is 100% by weight of EVOH resin (A) in metal conversion (after ashing and analyzed by ICP emission spectrometry). Usually 0.0005 to 0.1 parts by weight, preferably 0.001 to 0.05 parts by weight, particularly preferably 0.002 to 0.03 parts by weight. If the added amount is too small, the content effect may not be sufficiently obtained. Conversely, if the added amount is too large, the resulting film tends to be colored or odorous. In addition, when adding 2 or more types of salts to EVOH type resin (A), it is preferable that the total amount exists in the range of said addition amount.

The method of adding acetic acid, phosphoric acid, boron compound, acetate, and phosphate to EVOH resin (A) is not particularly limited, and i) Porosity of EVOH resin (A) having a water content of 20 to 80% by weight A method in which the precipitate is brought into contact with an aqueous solution of the additive to contain the additive and then dried; ii) After the additive is contained in a uniform solution (water / alcohol solution, etc.) of the EVOH resin (A), A method of extruding into a coagulating liquid in a strand shape, and then cutting the obtained strand into a cylindrical pellet or a spherical pellet by an underwater cut method, followed by a drying treatment; iii) EVOH resin ( A) A method in which additives and additives are mixed together and then melt-kneaded with an extruder or the like; iv) The alkali (sodium hydroxide) used in the saponification step during the production of EVOH resin (A) , May be mentioned potassium hydroxide, etc.) is neutralized with an organic acid such as acetic acid, a method in which to adjust the water washing treatment the amount of salt to organic acid and by-products such as acetic acid remaining.
In order to obtain the effects of the present invention more remarkably, the method i) and ii), which are excellent in the dispersibility of the additive, and the method iv) are preferred when an organic acid and a salt thereof are contained.

[EVA saponified product (B)]
The second essential component of the resin composition of the present invention is a saponified product (B) of an ethylene-vinyl acetate copolymer having an ethylene content of 70 mol% or more.
Such an EVA saponified product (B) is obtained by saponifying a vinyl acetate component of an ethylene-vinyl acetate copolymer having an ethylene content of 70 mol% or more. The EVOH resin (A) has an ethylene content. Is different.

  The EVA saponified product (B) is prepared by producing ethylene and vinyl acetate by any known polymerization method, for example, solution polymerization, suspension polymerization, emulsion polymerization, etc., and saponifying by a known method. The ethylene content of the EVA saponified product (B) is required to be 70 mol% or more, and the upper limit is usually 98 mol% or less, as measured based on ISO14663. The ethylene content is preferably 75 to 95 mol%, more preferably 80 to 95 mol%. When the ethylene content is too small, the effect of improving the piercing strength and tensile break elongation tends to be insufficient when a film-like molded product is obtained.

  The saponification degree of the EVA saponification product (B) is a value measured based on JIS K6726, and is usually 20 mol% or more, preferably 40 to 100 mol%, particularly preferably 80 to 100 mol%. It is. When the saponification degree is too low, the affinity with the EVOH resin (A) is insufficient and the dispersibility tends to decrease.

  The melt flow rate (MFR) (190 ° C., load 2160 g) of the EVA saponified product (B) is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, more preferably 2 to 2 g. 30 g / 10 min is preferable in terms of excellent dispersibility and excellent effects of the present invention.

The density of the EVA saponified product (B) is usually 500 to 1500 kg / m ³ , preferably 800 to 1200 kg / m ³ , and particularly preferably 900 to 1100 kg / m ³ .

  The EVA saponified product (B) may be copolymerized with another copolymerizable monomer similar to the EVOH resin (A) within a range not impairing the gist of the present invention.

  The EVA saponified product (B) is a modified product containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or an anhydride thereof by an addition reaction, a graft reaction or the like within a range not inhibiting the gist of the present invention. It may be. For example, the amount of modification is preferably 10 mol% or less. Examples of the unsaturated carboxylic acid or anhydride thereof include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, and crotonic acid, fumaric acid, itaconic acid, citraconic acid, maleic acid, and maleic acid. Examples thereof include ethylenically unsaturated dicarboxylic acids such as monomethyl, monoethyl maleate, and maleic anhydride, anhydrides thereof, half esters, etc. Among them, maleic anhydride is preferably used.

  The EVA saponified product (B) can be used in combination of two or more EVA saponified products having different ethylene contents, degree of saponification, molecular weight, MFR, density, modified group and modified amount within the above range. .

[Acid-modified EVA (C)]
The third essential component of the resin composition of the present invention is a carboxyl group-containing ethylene-vinyl acetate copolymer (C).
Such modified EVA (C) is obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an ethylene-vinyl acetate copolymer having an ethylene content of 70 mol% or more, and does not saponify. Therefore, the resin does not have a hydroxyl group, does not have a high gas barrier property, and is completely different from the EVOH resin (A) and the EVA saponified product (B).

  Such acid-modified EVA (C) is obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to an ethylene-vinyl acetate copolymer by an addition reaction, a graft reaction or the like. Examples of such unsaturated carboxylic acids or anhydrides thereof include maleic acid, maleic anhydride, fumaric acid, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, citraconic acid, hexahydrophthalic anhydride, and the like. An acid is preferably used. Specifically, maleic anhydride modified polyethylene, maleic anhydride modified polypropylene, maleic anhydride modified ethylene-propylene copolymer, maleic anhydride modified ethylene-methyl acrylate copolymer, maleic anhydride modified ethylene-ethyl acrylate One or a mixture of two or more selected from a copolymer, a maleic anhydride-modified ethylene-vinyl acetate copolymer, and the like are preferred.

  The amount of modification of the unsaturated carboxylic acid or anhydride thereof contained in the acid-modified EVA (C) is 0.001 to 3% by weight, more preferably 0.01 to 1% by weight, and particularly 0.03 to 0.5%. The weight percent is preferable, and if the modification amount is small, the effect of improving the compatibility is poor. On the other hand, if the amount is large, the thermal stability of the resin composition may be deteriorated.

  The acid-modified EVA (C) melt flow rate (MFR) (190 ° C., load 2160 g) is usually 0.5 to 100 g / 10 minutes, preferably 1 to 50 g / 10 minutes, more preferably 2 to 2 g. 30 g / 10 minutes.

The density of the acid-modified EVA (C) is usually 500 to 1500 kg / m ³ , preferably 800 to 1200 kg / m ³ , more preferably 900 to 1000 kg / m ³ .

  As the acid-modified EVA (C), two or more kinds of acid-modified EVA (C) having different ethylene content, molecular weight, MFR, density, modified group and modified amount within the above range can be used in combination.

[Combination ratio]
The compounding ratio of each component of the resin composition of the present invention is 2 to 5 parts by weight of acid-modified EVA (C) with respect to 100 parts by weight of the EVOH resin (A).
The EVA saponification product (B) is usually preferably blended in an amount of 10 to 40 parts by weight, more preferably more than 15 parts by weight, particularly preferably more than 15 parts by weight, 25 parts by weight with respect to 100 parts by weight of the EVOH resin (A). Is less than.
Mixing ratio (weight basis) of EVA saponified product (B) and acid-modified EVA (C), EVA saponified product (B) / acid-modified EVA (C) is usually 1 to 400, preferably 2 to 100, more preferably Is from 3 to 50, particularly preferably from 4 to 20.
When the three components are expressed by the blending ratio (weight basis), usually EVOH resin (A) / EVA saponified product (B) / acid-modified EVA (C) = 90.8 / 9.11 / 0.09 to 67/27 / 6, preferably EVOH resin (A) / EVA saponified product (B) / acid-modified EVA (C) = 80 / 19.5 / 0.5 to 80/16/4.

  In the present invention, in the resin composition in which the EVA saponified product (B) is blended with the main component EVOH resin (A), the presence of a specific amount of acid-modified EVA (C) allows the EVA saponified product to be contained in the EVOH resin. It is considered that can be uniformly dispersed. Since the unevenness of the resin composition is thereby eliminated, surging during production and strand breakage are eliminated, and molded articles such as pellets and films having good shapes can be obtained with excellent productivity. Furthermore, the presence of a specific amount of acid-modified EVA (C) causes the EVA saponification product (B) in the EVOH resin (A) to be appropriately dispersed, so that the resin composition is very suitable for melt molding. Has MFR. As a preferable MFR of the resin composition, when the load is 2160 g at 210 ° C., 2.5 to 4.5 g / 10 minutes, more preferably 3.0 to 4.3 g / 10 minutes, particularly preferably 3.5 to 4.3 g / 10 min.

[Other ingredients]
In the resin composition, the EVOH resin (A) and EVA saponified product (B) are within a range that does not impair the effects of the present invention (for example, usually less than 20% by weight, preferably less than 10% by weight of the resin composition). In addition to the acid-modified EVA (C), if necessary, it may contain a thermoplastic resin or an additive other than the EVOH resin (A), the EVA saponified product (B), or the acid-modified EVA (C). .
Examples of the thermoplastic resin other than the EVA saponified product (B) include polyolefin resin; ethylene-vinyl acetate copolymer resin; vinyl ester resin; polyester resin; polyamide resin; polystyrene resin; A carboxyl group-containing resin obtained by addition reaction or graft reaction of an unsaturated carboxylic acid such as maleic acid to a polyolefin resin, an ethylene-vinyl acetate copolymer resin, or a vinyl ester resin.
Examples of the additive include an antioxidant, a lubricant, an antistatic agent, a colorant, an ultraviolet absorber, a plasticizer, a heat stabilizer, a light stabilizer, a surfactant, an antibacterial agent, a desiccant, an antiblocking agent, and a difficult agent. Examples include a flame retardant, a crosslinking agent, a curing agent, a foaming agent, a crystal nucleating agent, an antifogging agent, a biodegradation additive, a silane coupling agent, and an oxygen absorber. These additives may be added to the components (A) to (C) in advance.
That is, the total amount of the component (A), the component (B), and the component (C) in the resin composition is usually 80 to 100% by weight, preferably 90 to 100% by weight.

(Preparation of resin composition)
The resin composition is prepared by mixing each component. Examples of such a mixing method include a melt mixing method, a solution mixing method, and a mechanical mixing method (for example, pellet dry blend).
The melt mixing method is a method of mixing each component in a molten state, for example, it can be performed using a known melt kneading apparatus such as a kneader ruder, an extruder, a mixing roll, a Banbury mixer, a plast mill, In general, it is industrially preferable to use a single-screw or twin-screw extruder, and in particular, a twin-screw extruder having an excellent kneading effect is preferable. If necessary, a vent suction device, a gear pump device, a screen device, etc. are provided. Is also preferable. It is also preferable to seal the inside of the hopper with an inert gas such as nitrogen for the purpose of suppressing thermal oxidative degradation of the resin.
Examples of the solution mixing method include a method in which each component is dissolved and mixed in a common good solvent and precipitated in a common poor solvent.
The resin mixed by the melt mixing method or the solution mixing method can be used, for example, in a powder form, a spherical or cylindrical pellet form, a flake form, or the like.
The mechanical mixing method is a method in which the resin is dry-blended in advance before being supplied to an extruder for product manufacture such as a film and is supplied to the extruder for product manufacture in a lump.

The order of mixing the components is not particularly limited,
<1> A method in which components (A) to (C) are mixed together and then melt-kneaded <2> A method in which some components are previously melt-kneaded and then the remaining components are added to further melt-knead <3> (4) A method in which the components (A) to (C) are uniformly dissolved and mixed in a solvent that can be dissolved and then the solvent is removed <4> (A) to (C) a part of the solvent in which the components can be dissolved A method for removing the solvent by adding the remaining components after dissolving the components of <5> and mixing the components in advance using a common good solvent, and then removing the solvent. Examples include a method of melt-mixing the composition and the remaining components.
Among these, the method <1> is practical and preferable in terms of simplicity of the apparatus and cost.

  Therefore, the most preferable mixing method is a method in which the EVOH resin (A), the EVA saponified product (B), and the acid-modified EVA (C) are dry-blended all at once before being supplied to the extruder and melt-kneaded in the extruder. .

When the resin composition of the present invention is obtained, the discharge rate of the extruder is 100 to 500 kg / hr, preferably 150 to 450 kg / hr, more preferably 200 to 400 kg / hr. If the discharge amount is too large, surging occurs and strand breakage tends to occur frequently.
The set temperature of the extruder is usually 100 to 300 ° C, preferably 150 to 270 ° C.
The diameter of the screw is usually 35 mm to 75 mm, and the length is generally 20 to 60 times the diameter.
As the shape of the screw to be used, in the case of a twin screw extruder, it is preferable to provide several kneading blocks.

<Film>
The film of the present invention has at least one resin composition layer. That is, you may use as a single layer film only of the said resin composition, and may be used as a multilayer structure which has at least 1 layer of resin composition layers. As described above, the resin composition of the present invention can usually contain other thermoplastic resins and additives at less than 20% by weight.
In the present invention, the resin composition layer, which is a gas barrier layer, is protected from moisture and mechanical impact, and a film having excellent piercing strength and tensile elongation at break is obtained. A multilayer structure having one layer is preferable.

Although it does not specifically limit as resin used as layers other than the resin composition layer which comprises the said multilayered structure, A hydrophobic thermoplastic resin is mentioned in order to prevent the fall of the gas barrier performance of the resin composition by a water | moisture content.
For example, specifically, polyolefin resins: linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, ultra-low-density linear polyethylene, medium-density polyethylene, high-density polyethylene, and the like (each made of metallocene catalyst) ), And polyethylene resins such as ethylene-α olefin copolymers, polypropylene, ethylene-propylene (block and random) copolymers, propylene-α-olefin (α-olefins having 4 to 20 carbon atoms) copolymer Polypropylene resins such as coalescence, polybutene, polypentene, etc .; grafted polyolefins obtained by graft-modifying these polyolefins with unsaturated carboxylic acids or their esters, cyclic polyolefin resins; ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylics Copolymer, ethylene-acrylic ester copolymer, polyester resin, polyamide resin (including copolymer polyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene, vinyl ester resin, polyester elastomer, Examples include polyurethane elastomers, halogenated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, and aromatic or aliphatic polyketones.
Among these, polyolefin resins are preferable from the viewpoint of mechanical strength and moldability, and polyethylene and polypropylene are particularly preferable.

  In particular, in order to improve the piercing strength and tensile breaking strength of the film, use at least one kind of ultra-low density linear polyethylene, low density linear polyethylene made of metallocene catalyst, polyolefin plastomer together with low density polyethylene. Is preferred.

  In addition, it is preferable to mix | blend an ultraviolet-resistant agent and an adhesive component with said hydrophobic thermoplastic resin. Examples of UV-resistant agents include UV absorbers (specifically, benzotriazole-based UV absorbers, benzophenone-based UV absorbers, salicylate-based UV absorbers, cyanoacrylate-based UV absorbers, and oxanilide-based UV absorbers). Agents (specifically, hindered amine light stabilizers, nickel light stabilizers, benzoate light stabilizers), colorants, etc., and the use of UV absorbers in combination with light stabilizers inhibits chain initiation. Since a synergistic effect as an agent and a radical scavenger is obtained, it is preferable.

  The blending amount of the UV-resistant agent is usually 0.01 to 10% by weight, preferably 0.05 to 5% by weight, particularly preferably 0.1 to 1% by weight, based on the hydrophobic thermoplastic resin. When the blending amount is too small, the hydrophobic thermoplastic resin is likely to be deteriorated by ultraviolet rays, but as the blending amount is increased, the ultraviolet resistance effect is not necessarily improved in proportion.

  Examples of the adhesive component include aliphatic saturated hydrocarbon resins such as polyisobutene, alicyclic saturated hydrocarbon resins, and the like, and usually 1 to 30% by weight, preferably based on the hydrophobic thermoplastic resin. It is 2 to 22% by weight, particularly preferably 5 to 20% by weight. When such a blending amount is appropriate, the films are pressure-bonded when the silage is covered with the film of the present invention, and are easily sealed, and the films are hardly peeled off. If the amount is too small, the film peels off and a gap is generated, and there is a high risk of air flowing in.

The melt flow rate (MFR) of the hydrophobic thermoplastic resin layer is usually 0.1 to 100 g / 10 minutes, preferably 0.5 to 50 g / 10 minutes under the conditions of 210 ° C. and a load of 2160 g. Most preferably, it is 0.5-20 g / 10min. If the MFR value is too small, the torque tends to be too high during extrusion molding, or vertical streaks tend to occur in the resulting film. On the other hand, if the MFR value is too large, the extrusion moldability becomes unstable. Or the film thickness of the resulting film tends to vary. Moreover, the one where the difference with MFR of EVOH resin composition is smaller is preferable.
The melting point of the hydrophobic thermoplastic resin layer is usually 100 to 300 ° C.

  In addition to these resins, a multilayer structure combined with paper, metal foil, uniaxial or biaxially stretched plastic film or sheet, woven fabric, non-woven fabric, metal cotton, wood surface, aluminum or silica deposition Good.

  Of these, a multilayer structure having a structure in which a hydrophobic thermoplastic resin layer excellent in water barrier property is used as an outer surface layer and a resin composition layer is used as an intermediate layer is preferably used.

The method for producing the multilayer structure is roughly divided into a method in which the resin composition is melted (melt molding method), a method in which the resin composition is dissolved in a solvent (for example, solution coating method), and the like. Is done. Among these, the melt molding method is preferable from the viewpoint of productivity.
Specifically, for example, a method of melt-extruding a hydrophobic thermoplastic resin to a molded article (for example, a film or sheet) of an EVOH resin composition, a resin composition layer is melt-extruded to a substrate such as a hydrophobic thermoplastic resin Examples thereof include a method of co-extrusion of a resin composition layer and a hydrophobic thermoplastic resin layer. Specifically, T-die extrusion, inflation extrusion, blow molding, profile extrusion, and the like are employed. In particular, when the inflation extrusion method is employed, the blow-up ratio is usually 1 to 10 and preferably 2 to 8 from the viewpoint of the mechanical strength of the silage film.
In the same manner as described above, the extruder used for the melt molding is 100 to 500 kg / hr, preferably 110 to 400 kg / hr, more preferably 120 to 300 kg / hr. hr. If it is too large, surging occurs and the thickness and appearance of the film tend to be non-uniform.
The set temperature of the extruder is usually 100 to 300 ° C, preferably 150 to 280 ° C.
The shape of the screw used is preferably a full flight type. The diameter of the screw is generally 40 mm to 65 mm, and the length is generally 20 to 45 times the diameter.
In general, it is industrially preferable to use a single-screw or twin-screw extruder as described above, but it is general to use a single-screw extruder when forming a film.

  Further, the resin composition film and a substrate such as a hydrophobic thermoplastic resin film are dried using a known adhesive such as an organic titanium compound, an isocyanate compound, a polyethyleneimine compound, a polyester compound, or a polyurethane compound. A laminating method, a heat laminating method without an adhesive, a laminating method with an adhesive resin layer interposed, and the like are employed.

  The adhesive resin constituting the adhesive resin layer is not particularly limited, and various resins can be used. Generally, an unsaturated carboxylic acid or an anhydride thereof is an olefin polymer (the above-mentioned broad sense). And a modified olefin polymer containing a carboxyl group obtained by chemically bonding to a polyolefin resin) by an addition reaction or a graft reaction. Specifically, maleic anhydride graft-modified polyethylene, anhydrous Suitable examples include one or a mixture of two or more selected from maleic acid graft-modified polypropylene, maleic anhydride graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, and the like. .

The layer structure of the multilayer structure is usually such that the resin composition layer is a (a1, a2,...) And the hydrophobic thermoplastic resin layer other than EVOH resin is b (b1, b2,...). 3 to 20 layers, preferably 3 to 15 layers, particularly preferably 3 to 10 layers. For example, specifically, b / a / b, a / b / a, a1 / a2 / b, a / b1 / b2, b2 / b1 / a / b1 / b2, b2 / b1 / a / b1 / a / Arbitrary combinations such as b1 / b2 are possible.
Also, R represents a recycled layer containing a mixture of a resin composition and a hydrophobic thermoplastic resin other than EVOH, which is obtained by remelt molding an end portion or defective product generated in the process of producing the multilayer structure. B / a / R, R / b / a, b / R / a / b, b / R / a / R / b, b / a / R / a / b, b / R / a / R / It is also possible to use a / R / b or the like.
Further, a known adhesive resin as described above may be used between the layers of the multilayer structure described above.

Among them, in order to prevent the gas barrier performance of the resin composition layer from deteriorating, the resin composition layer is an intermediate layer and the hydrophobic thermoplastic resin layers are both outer layers so as to prevent moisture permeation into the resin composition layer. A multilayer structure such that For example, specifically, hydrophobic thermoplastic resin layer / resin composition layer / hydrophobic thermoplastic resin layer, or hydrophobic thermoplastic resin layer / adhesive resin layer / resin composition layer / adhesive resin layer / Hydrophobic thermoplastic resin layer, hydrophobic thermoplastic resin layer / hydrophobic thermoplastic resin layer / adhesive resin layer / resin composition layer / adhesive resin layer / hydrophobic thermoplastic resin layer / hydrophobic thermoplastic resin layer Etc.
Among the above, the structural unit is hydrophobic thermoplastic resin layer / hydrophobic thermoplastic resin layer / adhesive resin layer / resin composition layer / adhesive resin layer / hydrophobic thermoplastic resin layer / hydrophobic thermoplastic resin layer. A multilayer structure is most preferred.

The thickness of the multilayer structure of the present invention is generally 5 to 500 μm, preferably 10 to 300 μm, more preferably 20 to 200 μm, and particularly preferably 20 to 50 μm.
The thickness of the hydrophobic thermoplastic resin layer in the multilayer structure is not particularly limited, but is usually 0.5 to 200 μm, preferably 1 to 100 μm, particularly preferably 1 to 10 μm. Although the thickness of a resin composition layer is not specifically limited, Usually, 0.1-100 micrometers, Preferably it is 0.5-50 micrometers, Most preferably, it is 0.5-5 micrometers. Although the thickness of an adhesive resin layer is not specifically limited, Usually, 0.5-50 micrometers, Preferably it is 1-30 micrometers, Most preferably, it is 1-5 micrometers.
In addition, in each layer, when there are a plurality of layers, it means that the thickness of each layer becomes the above-mentioned thickness.

  In addition, the thickness ratio of the hydrophobic thermoplastic resin layer / resin composition layer is preferably thicker than the hydrophobic thermoplastic resin layer for the purpose of suppressing moisture mixing into the hydrophobic thermoplastic resin. In the case, the ratio of the thickest layers is usually more than 1 to 30, preferably 2 to 10. The thickness ratio of the adhesive resin layer / resin composition layer is usually 0.1 to 2, preferably 0.2 to 1.

  As described above, the multilayer structure of the present invention is a multilayer structure which is only laminated with another hydrophobic thermoplastic resin or a base material (not subjected to stretching treatment), but is subjected to stretching treatment as necessary. May be.

In addition, about extending | stretching, a well-known extending | stretching method may be sufficient, for example, uniaxial stretching, biaxial stretching, etc. are mentioned. In the case of biaxial stretching, both a simultaneous biaxial stretching method and a sequential biaxial stretching method can be employed. Examples of the stretching method include tenter stretching and double bubble stretching. The stretching temperature is the temperature of the multilayer structure (the temperature in the vicinity of the multilayer structure) and is usually selected from the range of about 50 to 200 ° C., preferably about 80 to 160 ° C.
When using the resin composition of the present invention as a silage film, which will be described later, the film may be stretched at room temperature when the silage is sealed. It is better to stay.

<How to create silage>
The film of the present invention is preferably used as a silage film. The method for producing silage using the silage film of the present invention is not particularly limited.
As the silage raw material, a commonly used raw material is appropriately used, and usually grass. For example, specifically, grasses such as orchardgrass, timothy, perennial ryegrass, italian ryegrass, kentucky bluegrass, tall fescue, sudangrass, straw, etc .; legumes such as white clover, red clover, alfalfa; corn; Other examples include rape grass, wild grass, and vegetable scraps. These may be used alone or in combination of two or more.
In addition, as in all-in silage, concentrated feed such as cereals, bran, soybeans, soybean meal, beer meal, etc., and unused / low-use feed resources such as cereals, bran, soybeans, soybean meal, beer meal, etc. It is also possible to mix the secondary materials together to make silage.
The silage film of the present invention is preferably used for grass silage, and particularly preferably used as a film for packaging silage containing 70 to 99.9% by weight of grass.

As a silage method, a normal silage method is adopted. For example, if necessary, the raw material is dried to an appropriate water content (usually 30 to 70% by weight), and this is subjected to sealing conditions according to various silo shapes.
At this time, if the silage raw material is shredded or stepped on to increase the density of the silage raw material to reduce the amount of oxygen remaining in the film, the activity of aerobic bacteria and the generation of mold are suppressed, which is good. There is a tendency to obtain silage.
The silage may be sealed in various silos as described above, stored under anaerobic conditions, and fermented. Such storage period is usually 1 to 36 months, and further 2 to 24 months.

  The form of the silo using the silage film of the present invention is not particularly limited. For example, a bunker silo, an underground type (or semi-underground type) silo, a bag silo, a tube silo, a stack silo, and a wrap silo. Etc., various forms.

In particular, when creating a wrap silo, the grass is first shaped to a desired capacity (for example, 0.1 to 50 m ³ , preferably 1 to 30 m ³ ). For example, in the case of a cylindrical roll bale silo, the size is usually 0.5 to 3 m, preferably 1 to 2 m, and the height is usually 0.5 to 3 m, preferably 1 to 2 m.
Then, the silage film of the present invention is wrapped around the shaped grass using an ordinary wrap wrapping machine, and the silage is sealed. At the time of winding the film, it is preferable to reduce the air remaining in the silage as much as possible. Therefore, it is preferable to wind the film while stretching it so that the film is closely attached to the silage.
Such a draw ratio is usually 1.1 to 5 times, preferably 1.3 to 3 times, and particularly preferably 1.5 to 2 times.

  The number of windings of the film is usually 2 to 10 times, preferably 2 to 8 times, particularly preferably 2 to 5 times.

  When the resin composition of the present invention is made into a silage film, it is excellent in gas barrier properties, piercing strength and tensile elongation, and is particularly useful for wrap silo applications that are greatly influenced by the performance of the silage film.

  The silaged feed may be fed as it is, or may be adjusted as a mixed feed by adding a concentrated feed with a high protein content such as cereals, bran and soybeans.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the description of the examples unless it exceeds the gist.
In the examples, “parts” means weight basis unless otherwise specified.

Example 1
(Manufacture of resin composition pellets)
As the EVOH resin (A), a saponified ethylene-vinyl acetate copolymer [“SOANOL AT4403” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., ethylene content: 44 mol%, saponification degree: 99.7 mol%, MFR (210 ° C. 2160 g) 3.5 g / 10 min], EVA saponified product (B), saponified ethylene-vinyl acetate copolymer [“Mersen H0051K” manufactured by Tosoh Corporation, ethylene content 89 mol%, saponification degree 99 Mol%, MFR (190 ° C., 2160 g) 6.5 g / 10 min], acid-modified EVA (C), maleic anhydride-modified ethylene-vinyl acetate copolymer [“Fusabondo C MC190D” manufactured by DuPont Co., Ltd., ethylene Content 89 mol%, MFR (190 ° C., 2160 g) 16 g / 10 min, density 950 kg / m ³ ] as a weight ratio (A) / (B) / (C) = 80/17/3 was used. That is, 21 parts by weight of EVA saponified product (B) and 4 parts by weight of acid-modified EVA (C) with respect to 100 parts by weight of the EVOH resin (A).

The resin was dry blended, melted and kneaded under the following conditions, and extruded into a strand. The strand was cut with a pelletizer to obtain a cylindrical pellet-shaped resin composition.
Extruder: Diameter (D) 44 mm, twin screw extruder, L / D = 52, JSW TEX44
Screw shape: 2 kneading blocks Location of C10 and C13 Screen pack: 2 layers of 50 mesh Screw rotation speed: 550rpm
Nitrogen gas sealing from C6 and vacuum drawing from C14 Setting temperature: C2 / C3 / C4 / C5 / C6 / C7 / C8 / C9 / C10 / C11 / C12 / C13 / C14 / C15 / D = 50/80/100 / 100/100/100/150/180/220/220/220/220/220/220/240 ° C.
Discharge rate: 250 kg / hr

〔Evaluation method〕
(1) Observation of strands Table 1 shows the results of observing the strands extruded after the melt kneading and observing the surging state. In addition, when the strand was broken, the operation of cutting the end of the broken strand with a scissors and then introducing it again to the pelletizer was continued for pelletization.
(2) MFR
Table 1 shows the measurement results of MFR under the conditions of 210 ° C. and a load of 2160 g.

Comparative Example 3
In Example 1, a cylindrical pellet-shaped resin composition was obtained in the same manner except that the blend ratio of the resin composition was used as a weight ratio (A) / (B) / (C) = 80/19/1. ,evaluated. That is, 24 parts by weight of EVA saponification product (B) and 1 part by weight of acid-modified EVA (C) with respect to 100 parts by weight of EVOH resin (A).

Reference example 1
In Example 1, (A) / (B) / (C) = 80 with the blending ratio of the resin composition as the weight ratio.
/ 15/5. That is, EVA is 100 parts by weight of EVOH resin (A).
19 parts by weight of saponified product (B) and 6 parts by weight of acid-modified EVA (C).
The resin was dry blended, melted and kneaded under the following conditions, and extruded into a strand. The strand is cut with a pelletizer to obtain a cylindrical pellet-shaped resin composition, and MF
R was evaluated.
Extruder: Diameter (D) 30 mm, twin screw extruder, L / D = 44, manufactured by Plastic Engineering Laboratory Co., Ltd. Screw shape: 2 kneading blocks Screen pack: 2 layers of 90 mesh Screw rotation speed: 150 rpm
Set temperature: C1 / C2 / C3 / C4 / C5 / C6 / C7 / D = 150/170/190
/ 200/200/200/200/200 ° C
Discharge rate: 20kg / hr

Reference example 2
In Reference Example 1 , a pellet-like resin composition was similarly obtained except that the resin composition was used in a weight ratio of (A) / (B) / (C) = 80/12/8, and MFR was obtained. Evaluated.
That is, it is 15 parts by weight of EVA saponified product (B) and 10 parts by weight of acid-modified EVA (C) with respect to 100 parts by weight of EVOH resin (A).

Comparative Example 1
In Example 1, a cylindrical pellet-shaped resin composition is obtained in the same manner except that the blending ratio of the resin composition is set to (A) / (B) / (C) = 80/20/0. ,evaluated. That is, 25 parts by weight of EVA saponification product (B) and 0 parts by weight of acid-modified EVA (C) with respect to 100 parts by weight of EVOH resin (A).

Reference example 3
In Reference Example 1 , a pellet-shaped resin composition was similarly obtained except that the resin composition was used in a weight ratio of (A) / (B) / (C) = 80/9/11. Evaluated.
That is, it is 11 parts by weight of EVA saponified product (B) and 14 parts by weight of acid-modified EVA (C) with respect to 100 parts by weight of EVOH resin (A).

From the above results, in Comparative Example 1 where only the EVOH resin (A) and the EVA saponified product (B) were not blended with the acid-modified EVA (C), surging was considerably observed, and the shape of the obtained pellet was It was uneven. In addition, strand breakage occurred frequently and restoration work was frequently performed, resulting in very low production efficiency.
In contrast, in Example 1 in which 4 parts by weight of acid-modified EVA (C) was blended with 100 parts by weight of EVOH resin (A) in the presence of EVOH resin (A) and EVA saponified product (B). In this case, the generation of surging was suppressed, a pellet having a uniform shape was obtained, and the strand breakage was suppressed, so that the production efficiency was very good .

On the other hand, in Reference Example 3 in which 14 parts by weight of acid-modified EVA (C) was blended with 100 parts by weight of EVOH resin (A) in the presence of EVOH resin (A) and EVA saponified product (B), acid modification Because EVA (C), EVOH resin (A) and EVA saponified product (B) reacted too much, MFR becomes very high viscosity of 2.1 g / 10 min, resulting in difficult handling as a melt-molded resin. It was.

From the above results, in the presence of the EVOH resin (A) and the EVA saponified product (B), the acid-modified EVA (C) is contained in an amount of 2 to 5 parts by weight with respect to 100 parts by weight of the EVOH resin (A). It can be seen that the resin composition can be produced with excellent productivity even in a high discharge amount extruder, and that the obtained resin composition has a remarkable effect that MFR is very suitable for melt molding.

  In addition, when using the resin composition in Example 1 in which 21 parts by weight of EVA saponified product (B) and 4 parts by weight of acid-modified EVA (C) are used with respect to 100 parts by weight of EVOH resin (A), strands are produced during production. Without cutting, MFR was in the most preferable range, and the best results were obtained.

The method for producing a resin composition of the present invention is useful because it can eliminate unevenness of the resin composition, eliminate surging and strand breakage during production, and increase productivity. Furthermore, the resin composition of the present invention is a resin composition having a melt flow rate optimum for melt molding.
Accordingly, when the method for producing a resin composition and the resin composition of the present invention are used, a melt-formed product such as a pellet or film having a good shape can be obtained with high productivity, and particularly preferably used as a silage film. it can.

Claims (2)

  An ethylene-vinyl acetate copolymer saponified product (A) having an ethylene content of 20 to 60 mol% and an ethylene-vinyl acetate copolymer saponified product (B) having an ethylene content of 70 mol% or more are discharged in an amount of 100 to When melt-kneading with a 500 kg / hr extruder, 2 to 5 parts by weight of the carboxyl group-containing ethylene-vinyl acetate copolymer (C) is contained with respect to 100 parts by weight of the above (A). A method for producing a resin composition.   Saponified ethylene-vinyl acetate copolymer (B) having an ethylene content of 70 mol% or more with respect to 100 parts by weight of ethylene-vinyl acetate copolymer saponified product (A) having an ethylene content of 20-60 mol% (A). The manufacturing method of the resin composition of Claim 1 containing 10-40 weight part.