JP7425394B2 - Resin compositions, melt molding materials and multilayer structures - Google Patents

Description

The present invention relates to a resin composition, a melt-molding material, and a multilayer structure using the same, and more specifically, a resin composition with suppressed coloring, a melt-molding material comprising such a resin composition, and The present invention relates to a multilayer structure including a layer made of such a resin composition.

Gas barrier resins such as ethylene-vinyl alcohol copolymers (hereinafter referred to as "EVOH resins") and polyamide resins have abundant functional groups with excellent hydrophilicity, and have strong gas barrier properties through interactions through hydrogen bonds. It is said to express sexuality. These gas barrier resins are thermoplastic and are molded into films, sheets, bottles, etc., and are widely used as various packaging materials such as food packaging materials, pharmaceutical packaging materials, industrial chemical packaging materials, and agricultural chemical packaging materials.

These gas barrier resins are hydrophilic among thermoplastic resins, and their gas barrier properties vary depending on moisture. It is used for various purposes by laminating a gas barrier resin layer (hydrophilic thermoplastic resin layer) made of a thermoplastic resin.

When manufacturing the above-mentioned molded product using a multilayer structure including such a hydrophobic thermoplastic resin layer and a hydrophilic thermoplastic resin layer, it is important to avoid unnecessary parts such as scraps, edges, defective products, or After molded products are used for various purposes, scraps such as garbage are generated. Such scrap amounts to as much as 30-50% (area ratio) of the original multilayer structure. Therefore, this scrap may be collected, melt-molded, and reused as a recycled layer (hereinafter sometimes referred to as a "regrind layer") in at least one layer of the laminate (for example, , see Patent Document 1). Such recycling technology is industrially useful in terms of waste reduction and economic efficiency.

International Publication No. 2009/041440

On the other hand, when a recovered multilayer structure including a hydrophobic thermoplastic resin layer and a hydrophilic thermoplastic resin layer is remelted and reused as a regrind layer, the resin tends to be colored. Furthermore, in recent years, resin flow paths have become more complex with advances in molding technology, and resins tend to be more susceptible to thermal deterioration, and there is a need for technology that can suppress such coloring.

As a result of intensive studies in view of the above circumstances, the present inventors found that when a trace amount of an iron compound (C) is used in combination with a resin composition containing a hydrophilic thermoplastic resin (A) and a hydrophobic thermoplastic resin (B), It has been found that the above problem can be solved.

That is, the present invention provides a resin composition containing a hydrophilic thermoplastic resin (A), a hydrophobic thermoplastic resin (B), and an iron compound (C), wherein the content of the iron compound (C) is higher than that of the resin. The first aspect is a resin composition having a metal content of 0.0001 to 20 ppm per weight of the composition. Moreover, the second gist of the present invention is a melt-molding material made of the above-mentioned resin composition, and the third gist is a multilayer structure including a layer made of the above-mentioned resin composition.

The resin composition of the present invention is a resin composition containing a hydrophilic thermoplastic resin (A), a hydrophobic thermoplastic resin (B), and an iron compound (C), wherein the content of the iron compound (C) is Since the amount is 0.0001 to 20 ppm in terms of metal per weight of the resin composition, coloring can be suppressed.

In addition, the weight ratio of the hydrophilic thermoplastic resin (A) to the hydrophobic thermoplastic resin (B) is hydrophilic thermoplastic resin (A)/hydrophobic thermoplastic resin (B) = 90/10 to 1/ When it is 99, coloring can be further suppressed.

Furthermore, when the hydrophilic thermoplastic resin (A) is an EVOH resin, coloring can be further suppressed.

When the hydrophobic thermoplastic resin (B) is a polyolefin resin, coloring can be further suppressed.

Further, since the melt molding material made of the resin composition of the present invention has suppressed coloring, it can be suitably used as a material for various molded products, for example, as a packaging material for foods, medicines, agricultural chemicals, etc. .

Further, since the multilayer structure including the layer made of the resin composition of the present invention has suppressed coloring, it can be suitably used as various molded products, for example, as packaging materials for foods, medicines, agricultural chemicals, etc.

Next, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited thereto.

Generally, when manufacturing a laminate in which thermoplastic resin layers are laminated, scraps of the product, unnecessary parts such as edges, defective products, and dust after the molded product is used for various purposes are generated. These scraps such as garbage are reused as recovered items. The resin composition of the present invention can be suitably used as a resin composition when recycled as the above-mentioned recovered product.

<Resin composition>
The resin composition of the present invention contains a hydrophilic thermoplastic resin (A), a hydrophobic thermoplastic resin (B), and an iron compound (C). Each component will be explained below.

[Hydrophilic thermoplastic resin (A)]
In the present invention, the hydrophilic thermoplastic resin (A) is, for example, a thermoplastic resin having a hydrophilic group such as a hydroxyl group, an amino group, an amide group, a carboxyl group, and specifically, an EVOH resin, a polyamide resin, Examples include polyvinyl alcohol resin. Among these, EVOH resin is preferred from the viewpoint of suppressing coloring. Hereinafter, EVOH resin, which is a preferable hydrophilic thermoplastic resin of the present invention, will be explained.

[EVOH resin]
The EVOH resin is a water-insoluble thermoplastic resin that is usually obtained by saponifying an ethylene-vinyl ester copolymer, which is a copolymer of ethylene and a vinyl ester monomer. As the vinyl ester monomer, vinyl acetate is generally used from an economical point of view.

The polymerization of ethylene and the vinyl ester monomer can be carried out using any known polymerization method, such as solution polymerization, suspension polymerization, emulsion polymerization, etc., but generally methanol is used as a solvent. Solution polymerization is used. The obtained ethylene-vinyl ester copolymer can also be saponified by a known method.

The EVOH resin produced in this manner is mainly composed of structural units derived from ethylene and vinyl alcohol structural units, and contains a small amount of vinyl ester structural units that remain without being saponified.

As the vinyl ester monomer, vinyl acetate is typically used because of its market availability and good efficiency in treating impurities during production. Examples of other vinyl ester monomers include vinyl formate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, and other fatty acids. Examples include aromatic vinyl esters such as vinyl esters and vinyl benzoate, and aliphatic vinyl esters having usually 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms are used. can. These are usually used alone, but multiple types may be used simultaneously if necessary.

The content of ethylene structural units in the EVOH resin can be controlled by the pressure of ethylene when copolymerizing the vinyl ester monomer and ethylene, and is usually 20 to 60 mol%, preferably 25 to 50 mol%, particularly Preferably it is 25 to 35 mol%. If this content is too low, the gas barrier properties and melt moldability under high humidity tend to decrease, while if it is too high, the gas barrier properties tend to decrease.
Note that the content of such ethylene structural units can be measured based on ISO14663.

The degree of saponification of the vinyl ester component in the EVOH resin depends on the amount of saponification catalyst (usually an alkaline catalyst such as sodium hydroxide is used), temperature, time, etc. when saponifying the ethylene-vinyl ester copolymer. The amount can be controlled by usually 90 to 100 mol%, preferably 95 to 100 mol%, particularly preferably 98 to 100 mol%. If the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance, etc. tend to deteriorate.
The degree of saponification of such EVOH resin can be measured based on JIS K6726 (however, the EVOH resin is used as a solution uniformly dissolved in a water/methanol solvent).

Further, the melt flow rate (MFR) (210°C, load 2160 g) of the EVOH resin is usually 0.5 to 100 g/10 minutes, preferably 1 to 50 g/10 minutes, particularly preferably 3 to 35 g/10 minutes. It's a minute. If the MFR is too large, stability during film formation tends to be impaired, and if it is too small, the viscosity tends to become too high, making melt extrusion difficult.
Such MFR is an index of the degree of polymerization of the EVOH resin, and can be adjusted by the amount of polymerization initiator and the amount of solvent when copolymerizing ethylene and vinyl ester monomer.

The EVOH resin used in the present invention may further contain a structural unit derived from the comonomer shown below within a range that does not impede the effects of the present invention (for example, 20 mol% or less of the EVOH resin). The above comonomers include olefins such as propylene, 1-butene, isobutene, 3-buten-1-ol, 3-buten-1,2-diol, 4-penten-1-ol, 5-hexene-1,2 - Derivatives such as hydroxy group-containing α-olefins such as diols and their esterification products and acylation products; Hydroxyalkylvinylidenes such as 2-methylenepropane-1,3-diol and 3-methylenepentane-1,5-diol; Hydroxyalkyl vinylidene diacetates such as 1,3-diacetoxy-2-methylenepropane, 1,3-dipropionyloxy-2-methylenepropane, 1,3-dibutyryloxy-2-methylenepropane; acrylic acid, methacrylic acid , crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid, and other unsaturated acids or salts thereof, or mono- or dialkyl esters having 1 to 18 carbon atoms; acrylamide, 1 to 18 carbon atoms; Acrylamides such as N-alkylacrylamide, N,N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or its salt, acrylamidepropyldimethylamine or its acid salt or its quaternary salt; methacrylamide, N having 1 to 18 carbon atoms - Methacrylamides such as alkylmethacrylamide, N,N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or its salt, methacrylamidepropyldimethylamine or its acid salt or its quaternary salt; N-vinylpyrrolidone, N - N-vinylamides such as vinylformamide and N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylnitrile; vinyl ethers such as alkyl vinyl ethers having 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers, and alkoxyalkyl vinyl ethers; vinyl chloride , halogenated vinyl compounds such as vinylidene chloride, vinyl fluoride, vinylidene fluoride, and vinyl bromide; vinyl silanes such as trimethoxyvinylsilane; halogenated allyl compounds such as allyl acetate and allyl chloride; allyl alcohol, dimethoxyallyl alcohol and comonomers such as trimethyl-(3-acrylamido-3-dimethylpropyl)-ammonium chloride and acrylamide-2-methylpropanesulfonic acid. These can be used alone or in combination of two or more.

In particular, EVOH resins having a primary hydroxyl group in the side chain are preferable because they maintain gas barrier properties and have good secondary moldability. Among them, EVOH resins copolymerized with hydroxy group-containing α-olefins are preferable. In particular, EVOH resins having a 1,2-diol structure in their side chains are preferred. In particular, when the side chain has a primary hydroxyl group, its content is usually 0.1 to 20 mol%, more preferably 0.5 to 15 mol%, and particularly preferably 1 to 10 mol% of the EVOH resin. .

Furthermore, the EVOH resin may be one that has been "post-modified" such as urethanization, acetalization, cyanoethylation, or oxyalkylenation.

Furthermore, the EVOH resin used in the present invention may be a mixture with other EVOH resins, and such other EVOH resins include those with different contents of ethylene structural units and those with different degrees of saponification. , those with different degrees of polymerization, and those with different copolymerization components.

The content of EVOH resin in the hydrophilic thermoplastic resin (A) is usually 60% by weight or more, preferably 70% by weight or more, particularly preferably 80% by weight or more. If the content of EVOH resin is too low, the effect of inhibiting coloring tends to be insufficient. Note that the upper limit of the content of EVOH resin in the hydrophilic thermoplastic resin (A) is usually 100% by weight.

[Hydrophobic thermoplastic resin (B)]
In the present invention, the hydrophobic thermoplastic resin (B) is a thermoplastic resin that does not have a hydrophilic group as the hydrophilic thermoplastic resin (A) has, and specifically includes, for example, a polyolefin-based Resin, polyester resin, polystyrene resin, polyvinyl chloride resin, polycarbonate resin, polyacrylic resin, ionomer, ethylene-acrylic acid copolymer, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid copolymer Examples include polymers, ethylene-methacrylic acid ester copolymers, polyvinylidene chloride, vinyl ester resins, polyester elastomers, polyurethane elastomers, chlorinated polyethylene, and chlorinated polypropylene. These can be used alone or in combination of two or more. Among these, polyolefin resins are preferred from the viewpoint of suppressing coloring. Hereinafter, a polyolefin resin which is a suitable hydrophobic thermoplastic resin of the present invention will be explained.

As the polyolefin resin, known general polyolefin resins can be used, such as linear low density polyethylene, low density polyethylene, ultra low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-propylene (block and random) copolymers, polyethylene resins such as ethylene-α-olefin (α-olefin with 4 to 20 carbon atoms) copolymers, polypropylene, propylene-α-olefin (α-olefin with 4 to 20 carbon atoms) Examples include polypropylene resins such as copolymers, polyolefin resins such as polybutene, polypentene, and polycyclic olefin resins (polymers having a cyclic olefin structure in at least one of the main chain and the side chain). These may be used alone or in combination of two or more, and among them, polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-propylene (block or random) copolymer, polypropylene (PP), and blends thereof. Polyethylene, polypropylene (PP), and ethylene-propylene (block or random) copolymers are preferable in terms of economical efficiency and mechanical properties, and polyethylene, polypropylene (PP), and ethylene-propylene (block or random) copolymers further suppress the coloring of the regrind layer and achieve the effects of the present invention. It is particularly preferable from the viewpoint of increasing the

The melt flow rate (MFR) (230° C., load 2160 g) of the polyolefin resin is usually 0.1 to 50 g/10 minutes, preferably about 0.5 to 30 g/10 minutes.

The content of the polyolefin resin in the hydrophobic thermoplastic resin (B) is usually 50% by weight or more, preferably 60% by weight or more, particularly preferably 70% by weight or more. If the content of the polyolefin resin is too low, the effect of suppressing coloring tends to be insufficient. The upper limit of the content of the polyolefin resin in the hydrophobic thermoplastic resin (B) is usually 100% by weight.

Further, the weight content ratio of the hydrophilic thermoplastic resin (A) to the hydrophobic thermoplastic resin (B) (hydrophilic thermoplastic resin (A)/hydrophobic thermoplastic resin (B)) is 9 0/10 to The ratio is 1/99, preferably 70/30 to 2/98, particularly preferably 50/50 to 3/97. If the weight blending ratio is outside the above range, the effect of inhibiting coloring tends to be insufficient.

[Iron compound (C)]
The resin composition of the present invention contains an iron compound (C) in addition to the hydrophilic thermoplastic resin (A) and the hydrophobic thermoplastic resin (B), and the content of the iron compound (C) is a specific trace amount. It is characterized by Since the resin composition of the present invention has the above configuration, coloring can be suppressed.

Generally, when reusing a recovered multilayer structure having a hydrophilic thermoplastic resin layer and a hydrophobic thermoplastic resin layer as a regrind layer, the resin composition tends to be colored. This is due to the condensation of highly reactive sites such as functional groups of hydrophilic thermoplastic resins (hydroxyl groups and carboxy groups at polymerization terminals of EVOH resins, amide bonds, amino groups, and carboxy groups of polyamide resins) due to heat. It is thought that this is because reactions such as decomposition and decomposition occur, and radicals are generated by such reactions, causing deterioration of the hydrophobic thermoplastic resin.

Furthermore, resin compositions containing iron compounds (C) are thought to cause products to be colored by iron ions, and therefore those skilled in the art would normally avoid them. However, in the present invention, it has been unexpectedly discovered that by incorporating a specific trace amount of the iron compound (C) into the resin composition, a resin composition in which coloring after heating is suppressed can be obtained.

The reason why the above effects can be obtained is that iron, even in small amounts, forms ionic bonds and chelates with multiple functional groups such as hydroxyl groups, carboxyl groups, amide bonds, and amino groups, and has trivalent iron. It is stabilized as an ion. Therefore, it is presumed that the above reaction is suppressed and coloration can be suppressed.

The iron compound (C) may be present in the resin composition, for example, as an oxide, hydroxide, chloride, iron salt, or in an ionized state, or in combination with a resin or other ligands. may exist in the form of a complex due to the interaction of Examples of the above-mentioned oxides include ferric oxide, triiron tetroxide, iron suboxide, and the like. Examples of the chloride include ferrous chloride, ferric chloride, and the like. Examples of the hydroxide include ferrous hydroxide, ferric hydroxide, and the like. Examples of the iron salt include inorganic salts such as iron phosphate and iron sulfate, and organic salts such as iron carboxylic acids (acetic acid, butyric acid, stearic acid, etc.). These may be used alone or in combination of two or more.

The iron compound (C) is preferably water-soluble in terms of dispersibility in the resin composition. Further, from the viewpoint of dispersibility and productivity, the molecular weight is usually 100 to 10,000, preferably 100 to 1,000, particularly preferably 100 to 500.

The resin composition of the present invention usually contains 0.0001 to 20 ppm of iron compound (C) in terms of metal per weight of the resin composition. The content of the iron compound (C) is preferably 0.0005 to 5 ppm, particularly preferably 0.001 to 0.5 ppm, particularly preferably 0.001 to 0.05 ppm. If the content of the iron compound (C) is too small, the effect of suppressing coloring will be insufficient, and if it is too large, the tendency to increase the viscosity over time during melting will become noticeable.

Here, the content of the iron compound (C) is determined by ashing 0.5 g of the resin composition in an infrared heating furnace (650°C in an oxygen stream for 1 hour), dissolving the remaining ash with an acid, and fixing it with pure water. It can be determined by measuring with ICP-MS (manufactured by Agilent Technologies, Model 7500CE; standard addition method) using a sample solution.

In addition, the weight ratio of the hydrophilic thermoplastic resin (A) to the iron compound (C) is usually 0.000001 in terms of metal per 100 parts by weight of the hydrophilic thermoplastic resin (A). ~0.002 part by weight, preferably 0.000003 to 0.001 part by weight, particularly preferably 0.000005 to 0.0005 part by weight. If the weight ratio is too small, the effect of inhibiting coloring tends to be insufficient, and if the weight ratio is too large, the molded product tends to be colored.

[Regrind aid]
When producing the resin composition of the present invention from laminate scraps or the like, it may further contain a conventionally known regrind aid. Examples of the above-mentioned regrind aids include ethylene-vinyl acetate copolymers, saponified ethylene-vinyl acetate copolymers with an ethylene content of 70 mol% or more, hydrotalcites, and high-grade polymers having 12 to 30 carbon atoms. Examples include fatty acid metal salts and conjugated polyene compounds. These compounds can be used alone or in combination of two or more.

[Other compounding agents]
The resin composition of the present invention may contain additives that are generally blended into thermoplastic resins within a range that does not impede the effects of the present invention. For example, inorganic double salts, plasticizers (e.g., aliphatic polyhydric alcohols such as ethylene glycol, glycerin, hexanediol, etc.), oxygen absorbers [e.g., inorganic oxygen absorbers such as aluminum powder, potassium sulfite, photocatalytic titanium oxide, etc. Ascorbic acid, its fatty acid esters and metal salts, hydroquinone, gallic acid, polyhydric phenols such as hydroxyl group-containing phenolaldehyde resin, bis-salicylaldehyde-imine cobalt, tetraethylenepentamine cobalt, cobalt-Schiff base complex, Coordination bonds of nitrogen-containing compounds such as porphyrins, macrocyclic polyamine complexes, polyethyleneimine-cobalt complexes and transition metals other than iron, terpene compounds, reaction products of amino acids and hydroxyl group-containing reducing substances, triphenyl Oxygen absorbers based on organic compounds such as methyl compounds; coordination bonds between nitrogen-containing resins and transition metals other than iron (e.g., combinations of meta-xylene diamine (MXD) nylon and cobalt), tertiary hydrogen-containing resins and non-iron blends with transition metals (e.g., a combination of polypropylene and cobalt), blends of carbon-carbon unsaturated bond-containing resins with transition metals other than iron (e.g., a combination of polybutadiene and cobalt), photooxidative degradation resins (e.g., polyketones), anthraquinone polymers (e.g., polyvinylanthraquinone), etc., and these formulations may also contain photoinitiators (e.g., benzophenone), peroxide scavengers (e.g., commercially available antioxidants), and deodorizers. polymeric oxygen absorbers such as those containing additives (activated carbon, etc.)], heat stabilizers, light stabilizers, ultraviolet absorbers, colorants, antistatic agents, surfactants (excluding those used as lubricants) ), an antibacterial agent, an anti-blocking agent, a filler (for example, an inorganic filler, etc.), etc. may be added. These compounds can be used alone or in combination of two or more.

[Manufacture of resin composition]
As a raw material for the resin composition of the present invention, it is preferable to use recovered materials such as scraps of a multilayer structure containing layers consisting of a hydrophilic thermoplastic resin (A) and a hydrophobic thermoplastic resin (B). Depending on the case, it is also possible to utilize the used multilayer structure as various packaging materials. In addition to the layers made of hydrophilic thermoplastic resin (A) and hydrophobic thermoplastic resin (B), multilayer structures that are generally used as packaging materials for foods, etc. also have an adhesive resin layer and a regrind layer. It is included. Therefore, the resin composition of the present invention may contain these adhesive resin layers and regrind layers within a range that does not impede the effects of the present invention (eg, 30% by weight or less in the resin composition). The method for producing the resin composition of the present invention will be described below on the premise that a recovered multilayer structure containing a layer consisting of a hydrophilic thermoplastic resin (A) and a hydrophobic thermoplastic resin (B) is used. do.

Unnecessary parts (scraps) such as scraps and edges generated during the manufacturing of multilayer structure products, and recovered multilayer structure materials collected as waste are usually crushed and then sieved to reduce the particle size as necessary. It is used as a raw material for the resin composition of the present invention.

The above-mentioned recovered material can be pulverized using a known pulverizer. The apparent density of this pulverized product is usually 0.25 to 0.85 g/ml, more preferably 0.3 to 0.7 g/ml, and particularly preferably 0.35 to 0.6 g/ml. If the apparent density is too small, the dispersion of the hydrophilic thermoplastic resin (A) in the resin composition layer will be poor, and the melt moldability and mechanical properties of the resin composition layer of the resulting molded product will tend to deteriorate. If it is too large, there is a tendency that the melt moldability of the regrind layer of the obtained molded product decreases due to the occurrence of feeding defects in the extruder. Note that the above apparent density is a value measured in accordance with the "5.3 Apparent Density" test method of JIS K6891.

The above apparent density can be controlled by arbitrarily adjusting the shape of the crusher's crushing blades, the rotation speed of the crushing blades, the crushing processing speed, the opening size of the mesh used as a sieve, etc. It is. Further, the shape and particle size of the pulverized product can be adjusted using known methods.

The resin composition of the present invention is a pulverized product (hereinafter referred to as "pulverized product") of a recovered multilayer structure containing a hydrophilic thermoplastic resin (A) and a hydrophobic thermoplastic resin (B). It is obtained by adjusting the iron compound (C) component to be contained within a predetermined range. From the viewpoint of productivity, it is preferable to blend unrecycled hydrophobic thermoplastic resin (B) into such a pulverized product. Examples of methods for producing such resin compositions include known methods such as dry blending, melt kneading, solution mixing, and impregnation.

Examples of the dry blending method include (i) a method of dry blending the pulverized product, the iron compound (C), and optionally an unrecycled hydrophobic thermoplastic resin (B) using a tumbler or the like. It will be done.

Examples of the above-mentioned melt-mixing method include (ii) a method of melt-kneading the dry blend of (i) above, and (iii) a method of melt-kneading the above-mentioned pulverized product in a molten state and optionally an unrecycled hydrophobic thermoplastic resin (B). ) and melt-kneading the iron compound (C).

The above solution mixing method includes, for example, (iv) preparing a solution using the above pulverized product and optionally unrecycled hydrophobic thermoplastic resin (B), blending the iron compound (C) therein, and solidifying the solution. Examples include a method of solid-liquid separation and drying after molding.

The above-mentioned impregnation method includes, for example, (v) bringing the above-mentioned pulverized product and optionally unregenerated hydrophobic thermoplastic resin (B) into contact with an aqueous solution containing the iron compound (C); Examples include a method of incorporating an iron compound (C) into an unrecycled hydrophobic thermoplastic resin (B) and then drying it.

In addition, as another method, for example (vi) blending the iron compound (C) with the regrind aid and melt-kneading the regrind aid and the above-mentioned pulverized product, the hydrophilic thermoplastic resin (A ), a method for obtaining a resin composition containing a hydrophobic thermoplastic resin (B) and an iron compound (C), and the like.

In the present invention, it is possible to combine the different methods described above. Among these, the melt-mixing method is preferred, and the method (ii) is particularly preferred, since a resin composition with more remarkable productivity and the effects of the present invention can be obtained.

Further, as the iron compound (C) used in each of the above methods, as mentioned above, preferably a water-soluble iron compound is used, such as ferric oxide, triferric tetroxide, iron suboxide, etc. oxides, chlorides such as ferrous chloride and ferric chloride, hydroxides such as ferrous hydroxide and ferric hydroxide, inorganic salts such as iron phosphate and iron sulfate, and carboxylic acids (acetic acid, Examples include iron salts such as organic salts of iron (butyric acid, stearic acid, etc.). In addition, as mentioned above, in addition to being present in the resin composition as the above-mentioned salt, the iron compound may be present in an ionized state or in a complex state due to interaction with the resin or other ligands. You can leave it there.

Furthermore, as the aqueous solution containing the iron compound (C) used in the method (v) above, iron ions can be eluted by immersing the iron compound (C) aqueous solution or steel material in water containing various chemicals. You can use the one that has been prepared. In that case, the content (metal equivalent) of the iron compound (C) in the resin composition is controlled by the concentration of the iron compound (C) in the aqueous solution in which the pulverized product is immersed, the immersion temperature, the immersion time, etc. Is possible. The immersion temperature and time are usually 0.5 to 48 hours, preferably 1 to 36 hours, and the immersion temperature is usually 10 to 40°C, preferably 20 to 35°C. After such immersion, the pulverized product is subjected to solid-liquid separation using a known method and dried using a known drying method. Various drying methods can be employed as such a drying method, and either stationary drying or fluidized drying may be used. Moreover, these can also be performed in combination.

In addition, if the content of iron compound (C) in the resin composition containing the above-mentioned pulverized product already exceeds 20 ppm in terms of metal per weight of the resin composition, the iron compound (C) can be removed by the following method. The resin composition of the present invention can be obtained by adjusting the content.

As a method for adjusting the content of the iron compound (C), (I) the above-mentioned pulverized product is brought into contact with an extraction agent that does not contain the iron compound (C) or from which the iron compound (C) has been removed; A method of drying after eluting the iron compound (C) inside, (II) A method of making the above-mentioned pulverized product into a homogeneous solution and capturing and separating the iron compound (C) using a chelating agent, (III) A method of not recycling. Examples include a method of blending a commercially available hydrophilic thermoplastic resin (A) or an unrecycled hydrophobic thermoplastic resin (B) into a resin composition.
Among them, method (III) is usually used because the process is simple.

The resin composition of the present invention is not limited to the case where recovered products of multilayer structures are used as a raw material, and the resin composition of the present invention can be prepared by a known general method such as a dry blending method, a melt mixing method, etc. so as to have the formulation specified in the present invention. An unrecycled resin composition may be prepared using a method such as a method, a solution mixing method, an impregnation method, etc., and resin compositions prepared in such a manner are also included in the present invention.

The water content of the resin composition of the present invention is usually 0.01 to 0.5% by weight, preferably 0.05 to 0.35% by weight, particularly preferably 0.1 to 0.3% by weight. be.

In addition, the water content of the resin composition in the present invention is measured and calculated by the following method.
The weight (W1) of the resin composition before drying was weighed using an electronic balance, dried in a hot air dryer at 150°C for 5 hours, and the weight (W2) after being left to cool in a desiccator for 30 minutes was weighed, and the following formula was obtained. Calculate from
Moisture content (wt%) = [(W1-W2)/W1] x 100

Although the resin composition thus obtained can be subjected to melt molding as it is, it is also preferable to include a known lubricant in order to stabilize the feedability during melt molding. Examples of the types of lubricants include higher fatty acids having 12 or more carbon atoms (e.g., lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, etc.), higher fatty acid esters (e.g., methyl esters of higher fatty acids). , isopropyl ester, butyl ester, octyl ester, etc.), higher fatty acid amides (e.g., lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, etc.); saturated higher fatty acid amides such as oleic acid amide; amide, unsaturated higher fatty acid amide such as erucic acid amide, bis higher fatty acid amide such as ethylene bis stearic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, ethylene bis lauric acid amide, etc.), low molecular weight polyolefin (e.g. , low molecular weight polyethylene with a molecular weight of about 500 to 10,000, or low molecular weight polypropylene, or acid-modified products thereof), higher alcohols having 6 or more carbon atoms, ester oligomers, fluorinated ethylene resins, etc. These compounds can be used alone or in combination of two or more. Further, the content of such a lubricant is usually 5% by weight or less, preferably 1% by weight or less of the resin composition.

The resin composition of the present invention is prepared as a resin composition in various forms such as powder and liquid, and provided as a material for melt molding of various molded products. In particular, in the present invention, it is preferable to provide the material as a material for melt molding, since the effects of the present invention tend to be more efficiently obtained. The resin composition of the present invention may also include a resin composition obtained by mixing resins other than the hydrophilic thermoplastic resin (A) and the hydrophobic thermoplastic resin (B) used in the resin composition of the present invention. included.

Such molded products can be put into practical use as single-layer films molded using the resin composition of the present invention, as well as multilayer structures having layers molded using the resin composition of the present invention. Can be done.

[Multilayer structure]
The multilayer structure of the present invention includes a layer made of the resin composition of the present invention. A layer made of the resin composition of the present invention (hereinafter referred to as a "resin composition layer") may be formed on another base material (hereinafter referred to as a "base material") containing a thermoplastic resin as a main component other than the resin composition of the present invention. (referred to as "resin"), it is possible to provide further strength and other functions.

Examples of the base resin include linear low-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene (block and random) copolymers, and ethylene-α-olefin. Polyethylene resins such as (α-olefin having 4 to 20 carbon atoms) copolymers, polypropylene, polypropylene resins such as propylene-α-olefin (α-olefin having 4 to 20 carbon atoms) copolymers, polybutene, polypentene , (unmodified) polyolefin resins such as polycyclic olefin resins (polymer having a cyclic olefin structure in at least one of the main chain and side chain), and graft modification of these polyolefins with unsaturated carboxylic acids or their esters. Broadly defined polyolefin resins including modified olefin resins such as unsaturated carboxylic acid-modified polyolefin resins, ionomers, ethylene-vinyl acetate copolymers, ethylene-acrylic acid copolymers, ethylene-acrylic acid ester copolymers, Polyester resin, polyamide resin (including copolyamide polyamide), polyvinyl chloride, polyvinylidene chloride, acrylic resin, polystyrene resin, vinyl ester resin, polyester elastomer, polyurethane elastomer, polystyrene elastomer, chlorinated Examples include halogenated polyolefins such as polyethylene and chlorinated polypropylene, aromatic or aliphatic polyketones, and the like. These may be used alone or in combination of two or more.

Among these, polyamide resins, polyolefin resins, polyester resins, and polystyrene resins are preferred in terms of economy and productivity, and polyethylene resins, polypropylene resins, polycyclic olefin resins, and these resins are more preferred. It is a polyolefin resin such as an unsaturated carboxylic acid-modified polyolefin resin.

The layer structure of the multilayer structure is that the resin composition layer of the present invention is R, the hydrophilic thermoplastic resin (A) layer is a (a1, a2,...), and the base resin layer is b (b1, b2,...). ), b/R/a, b/R/a/b, b/R/a/R/b, b/a/R/a/b, b/R/a/R/ It is also possible to set it as a/R/b etc. Furthermore, it is possible to provide a recycled layer containing a mixture of the resin composition of the present invention and a base resin, which is obtained by remelting and molding the edges and defective products generated in the process of manufacturing the multilayer structure. be. The total number of layers in the multilayer structure is usually 2 to 15, preferably 3 to 10. In the above layered structure, an adhesive resin layer containing an adhesive resin may be interposed between each layer, if necessary.

As the adhesive resin, known adhesive resins can be used, and may be appropriately selected depending on the type of thermoplastic resin used for the base resin layer "b". A typical example is a modified polyolefin polymer containing a carboxyl group obtained by chemically bonding an unsaturated carboxylic acid or its anhydride to a polyolefin resin by an addition reaction, a graft reaction, or the like. Examples of the modified polyolefin polymers containing carboxyl groups include maleic anhydride graft-modified polyethylene, maleic anhydride graft-modified polypropylene, maleic anhydride graft-modified ethylene-propylene (block and random) copolymers, and maleic anhydride graft-modified polypropylene. Examples include graft-modified ethylene-ethyl acrylate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, maleic anhydride-modified polycyclic olefin resin, maleic anhydride graft-modified polyolefin resin, and the like. One kind or a mixture of two or more kinds selected from these can be used.

In a multilayer structure, when an adhesive resin layer is used between the resin composition layer of the present invention and the base resin layer, since the adhesive resin layer is located on both sides of the resin composition layer, the hydrophobicity It is preferable to use a resin with excellent adhesive properties.

The above-mentioned base resin and adhesive resin may contain conventionally known plasticizers within a range that does not impede the purpose of the present invention (for example, 30% by weight or less, preferably 10% by weight or less based on the entire resin). It may contain additives, fillers, clays (such as montmorillonite), colorants, antioxidants, antistatic agents, lubricants, core materials, antiblocking agents, waxes, and the like. These may be used alone or in combination of two or more.

Lamination of the resin composition of the present invention and the above-mentioned base resin (including the case where an adhesive resin layer is interposed) can be performed by a known method. For example, a method of melt-extrusion laminating a base resin on a film, sheet, etc. of the resin composition of the present invention, a method of melt-extrusion laminating a resin composition of the present invention on a base resin layer, a method of melt-extrusion laminating a resin composition of the present invention on a film, a sheet, etc. A method of co-extruding a resin composition layer and a base resin layer, a method of dry laminating a resin composition layer and a base resin layer using a known adhesive such as an organic titanium compound, an isocyanate compound, a polyester compound, a polyurethane compound, etc. Examples include a method of applying a solution of the composition and then removing the solvent. Among these, coextrusion is preferred from the viewpoint of cost and environment.

The multilayer structure as described above is then subjected to (heating) stretching treatment as required. The stretching treatment may be either uniaxial stretching or biaxial stretching, and in the case of biaxial stretching, simultaneous stretching or sequential stretching may be performed. Further, as the stretching method, a method with a high stretching ratio among roll stretching methods, tenter stretching methods, tubular stretching methods, stretch blowing methods, vacuum-pressure forming, etc. can be adopted. The stretching temperature is selected from the range of usually 40 to 170°C, preferably about 60 to 160°C, near the melting point of the multilayer structure. If the stretching temperature is too low, the stretchability will be poor, and if it is too high, it will be difficult to maintain a stable stretched state.

Note that heat setting may be performed subsequently for the purpose of imparting dimensional stability after stretching. Heat setting can be carried out by a well-known method, for example, the stretched film is heat-treated usually at 80 to 180°C, preferably 100 to 165°C, for about 2 to 600 seconds while maintaining the stretched film in a tensioned state. In addition, when the multilayer stretched film obtained from the resin composition of the present invention is used as a shrink film, in order to impart heat shrinkability, the above-mentioned heat setting is not performed, and the stretched film is, for example, blown with cold air. What is necessary is to carry out processing such as cooling and fixing.

Further, depending on the case, it is also possible to obtain a multilayer container in the form of a cup or a tray using the multilayer structure of the present invention. In that case, a draw forming method is usually employed, and specific examples thereof include a vacuum forming method, a pressure forming method, a vacuum pressure forming method, a plug-assisted vacuum pressure forming method, and the like. Furthermore, when obtaining a tube- or bottle-shaped multilayer container (laminate structure) from a multilayer parison (a hollow tubular preform before blowing), a blow molding method is employed. Specifically, extrusion blow molding methods (double-head type, moving mold type, parison shift type, rotary type, accumulator type, horizontal parison type, etc.), cold parison blow molding, injection blow molding, biaxial stretching Examples include blow molding methods (extrusion type cold parison biaxial stretch blow molding method, injection type cold parison biaxial stretch blow molding method, injection molding inline type biaxial stretch blow molding method, etc.). The obtained laminate may be subjected to heat treatment, cooling treatment, rolling treatment, printing treatment, dry lamination treatment, solution or melt coating treatment, bag making processing, deep drawing processing, box processing, tube processing, split processing, etc. as necessary. Can be done.

The thickness of the multilayer structure (including stretched ones) and the thicknesses of the resin composition layer, base resin layer, and adhesive resin layer that make up the multilayer structure depend on the layer structure, type of base resin, and adhesiveness. The thickness of the multilayer structure (including stretched ones) is usually 10 to 5,000 μm, preferably 30 to 3,000 μm, particularly preferably 50 μm, although it cannot be said in general depending on the type of resin, application, packaging form, required physical properties, etc. ~2000μm. The resin composition layer is usually 1 to 500 μm, preferably 3 to 300 μm, particularly preferably 5 to 200 μm, and the base resin layer is usually 5 to 3000 μm, preferably 10 to 2000 μm, particularly preferably 20 to 1000 μm, The adhesive resin layer usually has a thickness of 0.5 to 250 μm, preferably 1 to 150 μm, particularly preferably 3 to 100 μm.

Furthermore, in a multilayer structure, the thickness ratio of the resin composition layer to the base resin layer (resin composition layer/base resin layer) is usually determined by the ratio of the thickest layers when there are multiple layers. The ratio is 1/99 to 50/50, preferably 5/95 to 45/55, particularly preferably 10/90 to 40/60. In addition, the thickness ratio of the resin composition layer to the adhesive resin layer in the multilayer structure (resin composition layer/adhesive resin layer) is usually 10 when there are multiple layers, the ratio between the thickest layers. /90 to 99/1, preferably 20/80 to 95/5, particularly preferably 50/50 to 90/10.

Bags made of films, sheets, and stretched films obtained as described above, and containers and lids made of cups, trays, tubes, bottles, etc., can be used not only for general foods but also for seasonings such as mayonnaise and dressing, and miso. It is useful as a variety of packaging material containers for fermented foods, oil and fat foods such as salad oil, beverages, cosmetics, pharmaceuticals, etc. In particular, the layer made of the resin composition of the present invention is particularly useful as a packaging material for hot water sterilization of foods, medicines, agricultural chemicals, etc., since coloration is suppressed.

Hereinafter, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the description of the examples unless it exceeds the gist thereof.
In addition, "part" in the examples means a weight basis unless otherwise specified. Further, among the Examples, "Example 3" is a "Reference Example".

Prior to Examples, pellets of the following hydrophilic thermoplastic resin (A) and hydrophobic thermoplastic resin (B) were prepared, and the content of iron compound (C) contained in each pellet was measured.
・Hydrophilic thermoplastic resin (A): Ethylene-vinyl alcohol copolymer with an ethylene structural unit content of 29 mol%, saponification degree of 99.6 mol%, MFR 3.9 g/10 minutes (210°C, load 2160 g)・Hydrophobic thermoplastic resin (B): Polypropylene (manufactured by Mitsubishi Chemical Corporation, "Novatec EA9")

[Measurement of content of iron compound (C)]
A 0.5 g sample of each pellet of the hydrophilic thermoplastic resin (A) and hydrophobic thermoplastic resin (B) was ashed in an infrared heating furnace (650°C in an oxygen stream for 1 hour) to remove the ash content. A sample solution was prepared by dissolving the solution in an acid and adding pure water to a constant volume. This solution was measured by the standard addition method using the following ICP-MS (manufactured by Agilent Technologies, ICP mass spectrometer model 7500ce). As a result, the content of iron compound (C) in both cases was 0 ppm in terms of metal.

<Example 1>
5 parts of the pellets of the hydrophilic thermoplastic resin (A), 95 parts of the pellets of the hydrophobic thermoplastic resin (B), and iron(III) phosphate n-hydrate (Wako Pure Chemical Industries, Ltd.) as the iron compound (C). 0.000034 parts (manufactured by Kogyo Co., Ltd., loss on drying 20.9% by weight when heated at 230°C) (0.1 ppm in terms of metal per weight of the resin composition) was heated at 230°C using a Plastograph (manufactured by Brabender Co., Ltd.). After preheating for 5 minutes, the mixture was melt-kneaded for 5 minutes to obtain the resin composition of Example 1. The obtained resin composition was pulverized at 650 rpm using a pulverizer (manufactured by Sometani Sangyo Co., Ltd., SKR16-240) to obtain a pulverized product. The pulverized material was small pieces of 1 to 5 mm square.

<Example 2>
The procedure was carried out in the same manner as in Example 1, except that the amount of iron (III) phosphate n hydrate was changed to 0.00034 parts (1 ppm in terms of metal per weight of the resin composition). The resin composition of Example 2 and its pulverized product were obtained.

<Example 3>
Example 1 was carried out in the same manner as in Example 1, except that the amount of iron (III) phosphate n hydrate was changed to 0.0034 parts (10 ppm in terms of metal per weight of the resin composition). The resin composition of Example 3 and its pulverized product were obtained.

<Example 4>
Example 1 was carried out in the same manner as in Example 1, except that the amount of iron (III) phosphate n hydrate was changed to 0.0000017 parts (0.005 ppm in terms of metal per weight of the resin composition). The resin composition of Example 4 and its pulverized product were obtained.

<Comparative example 1>
A resin composition of Comparative Example 1 and its pulverized product were obtained in the same manner as in Example 1, except that iron (III) phosphate n-hydrate was not blended in Example 1.

The resin compositions of Examples 1 to 4 and Comparative Example 1 were evaluated for coloring by the method shown below. The results are shown in Table 1 below.

[Coloring evaluation]
Using the pulverized product of the resin composition as a sample, the YI value was measured using a spectrophotometer (SE6000) manufactured by Nippon Denshoku Kogyo Co., Ltd. At this time, the sample was filled into a cylinder with an inner diameter of 32 mm and a height of 30 mm, and the sample was rubbed completely before being subjected to measurement. In addition, a sample obtained by heat-treating the sample at 150° C. for 5 hours in an oven under an air atmosphere was similarly measured. A low YI value means that the resin composition is not colored, and a lower YI value is more preferable.

The resin compositions obtained in Examples 1 to 4 containing the iron compound (C) had a lower YI value than Comparative Example 1 not containing the iron compound (C), and coloration was suppressed. In addition, regarding the colorability after heating the resin composition, Examples 1 to 4 had lower YI values than Comparative Example 1, and coloration was suppressed.

Since the resin composition of the present invention is suppressed from discoloration due to thermal deterioration, it can be used in various foods, seasonings such as mayonnaise and dressings, fermented foods such as miso, oil and fat foods such as salad oil, beverages, cosmetics, and pharmaceuticals. It is particularly useful as a variety of packaging materials.

Claims (6)

A resin composition containing a hydrophilic thermoplastic resin (A), a hydrophobic thermoplastic resin (B), and an iron compound (C), wherein the hydrophilic thermoplastic resin (A) is an ethylene-vinyl alcohol copolymer. The content of ethylene structural units in the ethylene-vinyl alcohol copolymer is 20 to 60 mol%, the hydrophobic thermoplastic resin (B) is a polyolefin resin, and the hydrophobic thermoplastic resin (B) is a polyolefin resin. The weight content ratio of the hydrophilic thermoplastic resin (A) to the resin (B) is hydrophilic thermoplastic resin (A)/hydrophobic thermoplastic resin (B) = 50/50 to 1/99, and the iron The content of the compound (C) is 0.0001 to 1 ppm in terms of metal per weight of the resin composition , and the weight ratio of the hydrophilic thermoplastic resin (A) and the iron compound (C) is A resin composition characterized in that the iron compound (C) is contained in an amount of 0.000001 to 0.002 parts by weight in terms of metal based on 100 parts by weight of the hydrophilic thermoplastic resin (A) . The resin composition according to claim 1, wherein the content of the iron compound (C) is 0.0001 to 0.5 ppm in terms of metal per weight of the resin composition. The weight content ratio of the hydrophilic thermoplastic resin (A) to the hydrophobic thermoplastic resin (B) is hydrophilic thermoplastic resin (A)/hydrophobic thermoplastic resin (B) = 50/50 to 2/98 . The resin composition according to claim 1 or 2, characterized in that: The weight ratio of the hydrophilic thermoplastic resin (A) to the hydrophobic thermoplastic resin (B) is hydrophilic thermoplastic resin (A)/hydrophobic thermoplastic resin (B) = 50/50 to 3/97. The resin composition according to any one of claims 1 to 3, characterized in that: A melt-molding material comprising the resin composition according to any one of claims 1 to 4. A multilayer structure comprising a layer made of the resin composition according to any one of claims 1 to 4.