JP2012131912A - Oxygen absorbing resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resin composition that excels in oxygen absorbing performance, resin strength, resin workability and resin color, and is deodorized.SOLUTION: This oxygen absorbing resin composition includes a polyolefin resin, a transition metal catalyst, and a polyamide resin produced by polycondensation of an aromatic diamine and a dicarboxylic acid, wherein the content of a phosphorus atom in the polyamide resin is ≤500 ppm; the terminal amino group concentration in the polyamide resin is ≤30 μeq/g; and the total content of the transition metal catalyst and the polyamide resin is 15-60 mass%.

Description

  The present invention relates to an oxygen-absorbing resin composition that exhibits excellent oxygen-absorbing performance, has no reduction in strength due to oxidative degradation of the resin, is excellent in resin processability, has a good color tone, and does not generate odor.

  Conventionally, containers such as metal cans, glass bottles, and various plastic packages are known as packaging containers, but quality deterioration due to oxygen in the packaging containers is a problem. For this reason, in recent years, as one of the deoxygenation packaging technologies, a container is constituted by a multilayer material in which an oxygen absorption layer composed of an oxygen absorption resin composition in which an iron-based oxygen absorber is blended with a thermoplastic resin is provided. Development of packaging containers in which the gas barrier property is improved and the container itself is provided with an oxygen absorbing function has been performed. For example, an oxygen-absorbing multilayer film is a thermoplastic in which an oxygen absorbent is dispersed between a conventional gas-barrier multilayer film in which a heat seal layer and a gas barrier layer are laminated, and optionally through an intermediate layer made of a thermoplastic resin. It is used as a resin layer with an oxygen absorption layer added to the outside to prevent oxygen permeation, and to absorb oxygen in the container. It is manufactured using a method (see Patent Document 1).

  However, those using oxygen absorbers such as iron powder are detected by metal detectors used for detecting foreign substances such as food, and the internal visibility is insufficient due to the problem of opacity. There was a problem that it cannot be used for beverages such as alcohol whose flavor is impaired. In addition, since the oxidation reaction of iron powder is used, the effect of oxygen absorption can be exhibited only when the material to be preserved is a high moisture type.

  On the other hand, in a composition composed of a polymer and having an oxygen scavenging property, a resin composition comprising a polyamide, particularly a xylylene group-containing polyamide and a transition metal, is known as an oxidizable organic component, and a resin composition having an oxygen scavenging function or There are also examples of oxygen absorbers obtained by molding the resin composition, packaging materials, and multilayer laminated films for packaging (see Patent Documents 2 to 6).

  Properties required for a polymer used as a packaging material include little coloration, transparency, less odor generation, and less foreign matter and gel. For example, in order to obtain a polyamide with less gel in the polymer production process, it is important to advance the polycondensation so as to quickly reach a desired molecular weight while minimizing the heat history in the polyamide production process. As a method for reducing the thermal history in the polyamide production process, it is effective to add a compound having a catalytic effect to the polycondensation system in order to rapidly advance the amidation reaction.

  In a xylylene group-containing polyamide resin, it is widely known that a phosphorus atom-containing compound is added as a compound having a catalytic effect on an amidation reaction during polycondensation, and a resin composition comprising a xylylene group-containing polyamide and a transition metal There is also an example of an oxygen-absorbing resin composition and a packaging material in which the phosphorus atom-containing compound in the xylylene group-containing polyamide resin is less than 150 ppm in terms of phosphorus atom concentration (see Patent Document 7).

  The phosphorus atom-containing compound not only accelerates the amidation reaction in the polycondensation of the xylylene group-containing polyamide resin, but also has an effect as an antioxidant that prevents the polyamide from being colored by oxygen present in the polycondensation system. When there are few phosphorus atom containing compounds, there exists a problem that a xylylene group containing polyamide resin is oxidized and colored by the oxygen which exists in a system at the time of polycondensation, and an odor generate | occur | produces. On the other hand, when there are many phosphorus atom-containing compounds, the xylylene group-containing polyamide is stabilized. Therefore, when the xylylene group-containing polyamide is used as an oxygen-absorbing resin composition in combination with a xylylene group-containing polyamide and a transition metal, oxygen absorption performance is improved. It has the problem of being lowered. For this reason, it is necessary to select an appropriate addition amount of the phosphorus atom-containing compound.

  Furthermore, the resin composition containing a transition metal catalyst and oxidizing the polyamide resin or the like to develop an oxygen absorbing function oxidizes the xylylene group-containing polyamide resin, resulting in a decrease in strength due to oxidative degradation of the resin, and the packaging container itself There is a problem that the strength of the glass is reduced.

  In addition, there is an example of MXD6, which is a polyamide obtained by polycondensation of metaxylylenediamine and adipic acid, which shows an oxidation reaction with a polyamide resin and a transition metal catalyst, but in a system in which transition metal is mixed with MXD6 For use as an oxygen-absorbing resin composition and preserving the material to be stored well, the oxygen-absorbing ability may be low. In addition, a system in which transition metal is mixed with MXD6 usually uses a blend of a polyester resin such as polyethylene terephthalate (hereinafter referred to as PET) or a relatively high melting point resin such as nylon 6.

Japanese Patent Laid-Open No. 9-234832 Japanese Patent Laid-Open No. 5-140555 JP 2001-252560 A JP 2003-341747 A JP 2005-119893 A JP 2001-179090 A JP-A-6-41422

  An object of the present invention is to provide a resin composition that solves the above problems and is excellent in oxygen absorption performance, resin strength, resin processability, and resin color tone, and generates little odor.

  The present inventors blended a specific polyamide, transition metal, and polyolefin resin containing a specific concentration of phosphorus atom-containing compound at a specific ratio to provide excellent oxygen absorption performance and retain the resin strength after storage. Furthermore, it has been found that an oxygen-absorbing resin composition having excellent processability, good color tone and no odor generation is obtained.

  That is, the present invention is an oxygen-absorbing resin composition containing a polyamide resin obtained by polycondensation with a polyolefin resin, a transition metal catalyst and an aromatic diamine and a dicarboxylic acid, and the phosphorus atom content in the polyamide resin is Oxygen absorption, characterized in that it is 500 ppm or less, the terminal amino group concentration of the polyamide resin is 30 μeq / g or less, and the total content of the transition metal catalyst and the polyamide resin is 15 to 60% by mass It is a resin composition.

  According to the present invention, it is possible to provide an oxygen-absorbing resin composition that has high oxygen-absorbing performance, hardly deteriorates in strength due to oxidation of polyamide resin, has excellent color tone, and generates little odor.

  The oxygen-absorbing resin composition of the present invention is a polyamide obtained by polycondensation of an aromatic diamine and a dicarboxylic acid, having a terminal amino group concentration of 30 μeq / g or less and containing a phosphorus atom-containing compound of 500 ppm or less in terms of phosphorus atoms. A resin composition containing a resin (hereinafter, the polyamide resin is specifically referred to as “polyamide resin A”), a transition metal, and a polyolefin resin. Hereinafter, the details of each resin, the phosphorus atom-containing compound, and the transition metal catalyst will be described.

  The polyamide resin A in the present invention is a polyamide resin having a terminal amino group concentration of 30 μeq / g or less obtained by polycondensation of an aromatic diamine and a dicarboxylic acid, and a phosphorus atom content in the polyamide resin of 500 ppm or less. is there. Details of the polyamide resin A will be described.

  The polyamide resin A in the present invention is obtained by polycondensation of an aromatic diamine and a dicarboxylic acid. The polycondensation of the aromatic diamine and the dicarboxylic acid can be carried out by melt polymerization in which the aromatic diamine and dicarboxylic acid are melted, solid phase polymerization in which the polyamide resin pellets are heated under reduced pressure, or the like.

  Examples of the aromatic diamine in obtaining the polyamide resin A include orthoxylylenediamine, paraxylylenediamine, and metaxylylenediamine, but paraxylylenediamine, metaxylylenediamine, or these from the viewpoint of oxygen absorption performance. A mixture is preferably used, and metaxylylenediamine is particularly preferably used. In addition, various aliphatic diamines and aromatic diamines may be incorporated as copolymerization components as long as the performance is not affected.

  Examples of the dicarboxylic acid for obtaining the polyamide resin A include adipic acid, azelaic acid, sebacic acid, dodecanoic acid, isophthalic acid, terephthalic acid, and malonic acid. Among these, from the viewpoint of oxygen absorption performance, adipic acid, sebacic acid, isophthalic acid or a mixture thereof is preferable, and a mixture of adipic acid and sebacic acid or a mixture of adipic acid and isophthalic acid is particularly preferable. The molar ratio in the case of using a mixture of adipic acid and sebacic acid is preferably sebacic acid: adipic acid = 0.3-0.7: 0.7-0.3, and 0.4-0.6: 0.6 -0.4 is particularly preferred. Further, when using a mixture of adipic acid and isophthalic acid, adipic acid: isophthalic acid is preferably 0.7 to 0.97: 0.3 to 0.03, and 0.8 to 0.95: 0.2 to 0 .05 is particularly preferred. In addition, various aliphatic dicarboxylic acids and aromatic dicarboxylic acids may be incorporated as copolymerization components as long as the performance is not affected.

  The polyamide resin A in the present invention is a polyamide resin having a terminal amino group concentration of 30 μeq / g or less obtained by polycondensation of at least an aromatic diamine and a dicarboxylic acid, but has a terminal amino group concentration of 25 μeq / g or less. And oxygen absorption performance are improved, and it is more preferably 20 μeq / g or less because oxygen absorption performance is further improved. Thus, the oxygen absorption performance tends to improve as the terminal amino group concentration decreases, and it is preferable to reduce the concentration as much as possible. However, in consideration of economic rationality, the lower limit is 5 μeq / g or more. It is preferable to do. If the terminal amino group concentration is higher than 30 μeq / g, good oxygen absorption performance cannot be obtained.

In order to reduce the terminal amino group concentration of the polyamide resin to 30 μeq / g or less,
1) Method for carrying out polycondensation by adjusting the molar ratio of aromatic diamine and dicarboxylic acid 2) Method for reacting polyamide resin with carboxylic acid to seal the terminal amino group 3) Method for solid-phase polymerization of polyamide resin These methods are preferably carried out, and these methods can be carried out alone or in combination. In particular, the combination of the methods 1), 3), 2) and 3) is preferable because a polyamide resin having better oxygen absorption performance and moldability at the time of producing a multilayer body can be obtained. The following describes these methods.

  1) In the method of carrying out polycondensation by adjusting the molar ratio of aromatic diamine and dicarboxylic acid, dicarboxylic acid is used excessively with respect to aromatic diamine. Specifically, aromatic diamine and dicarboxylic acid are used. The molar ratio (aromatic diamine / dicarboxylic acid) is preferably 0.985 to 0.997, particularly preferably 0.988 to 0.995. When the molar ratio is less than 0.985, it is difficult to increase the degree of polymerization of the polyamide resin.

  2) In the method of reacting the polyamide resin with carboxylic acid to seal the terminal amino group, the terminal amino group concentration of the polyamide resin is reacted with the carboxylic acid to adjust the terminal amino group concentration. The carboxylic acid to be used is not particularly limited, but a carboxylic anhydride is preferable, and specifically, phthalic anhydride, maleic anhydride, benzoic anhydride, glutaric anhydride, itaconic anhydride, citraconic anhydride, acetic anhydride, anhydrous Examples include butyric acid, isobutyric anhydride, trimellitic anhydride, pyromellitic anhydride, and the like. The polyamide resin and the carboxylic acid can be reacted by, for example, a method of adding at the time of melt polymerization or a method of adding a carboxylic acid to the polyamide resin obtained by melt polymerization and then melt-kneading the polyamide resin. In order to increase the degree of polymerization, melt kneading is preferred.

  3) In the method of solid-phase polymerization of polyamide resin, the terminal amino group concentration is adjusted by further subjecting the polyamide resin obtained by melt polymerization to a solid-phase polymerization reaction. Solid phase polymerization proceeds by heating polyamide resin pellets under reduced pressure. The pressure during the solid phase polymerization is preferably 100 torr or less, and more preferably 30 torr or less. Further, the temperature at the time of solid phase polymerization needs to be 130 ° C. or higher, more preferably 150 ° C. or higher, and preferably 10 ° C. or higher, more preferably 15 ° C. or lower than the melting point of the polyamide resin. The solid state polymerization time is preferably 3 hours or more. By performing solid phase polymerization, the terminal amino group concentration of the polyamide resin is decreased, the molecular weight is increased, and the viscosity can be adjusted.

  As the polyamide resin A of the present invention, those having low crystallinity are preferably used. Specifically, those having a low crystallinity with a half-crystallization time of 150 seconds or more, or those having no melting point peak when the melting point is measured by DSC are preferable. When the half crystallization time of the polyamide resin A is 150 seconds or more, higher oxygen absorption performance can be obtained.

  Further, the polyamide resin A preferably has a low melting point and glass transition temperature (hereinafter referred to as Tg) in consideration of processability and oxygen absorption performance with a polyolefin resin. The melting point of the polyamide resin A is preferably 200 ° C. or lower, more preferably 190 ° C. or lower or a resin having no melting point. Tg is preferably 90 ° C. or lower, and particularly preferably 80 ° C. or lower.

The oxygen permeability coefficient of the polyamide resin A is preferably 0.2 to 1.5 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH), and 0.3 to 1.0 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH) is more preferable. When the oxygen permeability coefficient is 0.2 to 1.5 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH), when the polyamide resin A and the polyolefin resin are blended, higher oxygen absorption performance is obtained. can get.

  When the polyamide resin A and the polyolefin resin are mixed, considering the processability, the melt flow rate (hereinafter referred to as MFR) of the polyamide resin A is 200 ° C., 3 to 20 g / 10 minutes, 240 ° C., 4 Those having ˜25 g / 10 min are preferably used. In this case, when the resin is processed at a temperature where the difference between the MFR of the polyolefin resin and the MFR of the polyamide resin A is ± 20 g / 10 minutes, preferably ± 10 g / 10 minutes, the kneaded state becomes good, and a film or sheet is obtained. In this case, a processed product having no problem in appearance can be obtained. The MFR of the polyamide resin A can be adjusted by adjusting the molecular weight, for example. Examples of a method for adjusting the molecular weight include a method of adding a phosphorus compound as a polymerization accelerator and a method of solid-phase polymerization after melt polymerization of the polyamide resin A.

  The polyamide resin A obtained by polycondensation of an aromatic diamine and a dicarboxylic acid is preferably synthesized by a method that undergoes two steps of solid phase polymerization after melt polymerization. The number average molecular weight of the polyamide resin A is preferably 18000 to 27000, particularly preferably 20000 to 26000.

  In the present invention, the phosphorus atom added to the polyamide is preferably added to the polyamide in the form of a phosphorus atom-containing compound. Examples of the phosphorus atom-containing compound used in the present invention include inorganic phosphorus compounds such as phosphates, phosphites, and hypophosphites, organic phosphorus compounds, and hydrates thereof. Trisodium phosphate, tripotassium phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, sodium dihydrogen phosphate, potassium dihydrogen phosphate, sodium phosphite, potassium phosphite, disodium hydrogen phosphite , Dipotassium hydrogen phosphite, sodium hypophosphite, potassium hypophosphite, iron phosphate and the like. These phosphorus atom-containing compounds can be used alone or in combination of two or more. Among the phosphorus atom-containing compounds, it is preferable to use trisodium phosphate and sodium hypophosphite in combination from the viewpoint of oxygen absorption, resin color, and odor. The phosphorus atom-containing compounds that can be used in the present invention are not limited to these compounds.

  The addition amount of the phosphorus atom-containing compound of the present invention is preferably 500 ppm or less in terms of phosphorus atom concentration in the polyamide resin A, more preferably 40 to 450 ppm, and still more preferably 60 to 400 ppm. Moreover, when exceeding 500 ppm, since the polyamide resin A is stabilized and oxygen absorption performance falls, it is not preferable.

The polyolefin resin of the present invention includes high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, various polyethylenes such as polyethylene using a metallocene catalyst, polystyrene, polymethylpentene, and propylene homopolymer. Polypropylenes such as polymers, propylene-ethylene block copolymers, and propylene-ethylene random copolymers can be used alone or in combination. Among these polyolefin resins, from the viewpoint of oxygen absorption performance, the oxygen permeability coefficient is preferably 80 to 200 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). When the polyolefin resin is used, good oxygen absorption performance can be obtained. Due to oxygen absorption performance and film processability, polyolefin resins include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, various polyethylenes such as polyethylene using a metallocene catalyst, and propylene-ethylene block copolymers. Various polypropylenes such as propylene-ethylene random copolymer are particularly preferably used. These polyolefin resins include ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, if necessary. A polymer, an ethylene-methyl methacrylate copolymer, or a thermoplastic elastomer may be added.

  In consideration of the miscibility with the polyamide resin A, it is particularly preferable to add a maleic anhydride-modified polyolefin resin. The addition amount of the maleic anhydride-modified polyolefin is preferably 1 to 30 wt%, particularly preferably 3 to 15 wt% with respect to the polyolefin resin.

  Further, the polyolefin resin of the present invention includes coloring pigments such as titanium oxide, additives such as antioxidants, slip agents, antistatic agents, stabilizers, fillers such as calcium carbonate, clay, mica, silica, and deodorants. An agent or the like may be added. In particular, it is preferable to add an antioxidant in order to recycle and reprocess offcuts generated during production.

  Examples of the transition metal catalyst used in the present invention include compounds of a first transition element such as Fe, Mn, Co, and Cu. Further, transition metal organic acid salts, chlorides, phosphates, phosphites, hypophosphites, nitrates and the like alone or a mixture thereof can be cited as examples of transition metal catalysts. Examples of the organic acid include salts of C2-C22 aliphatic alkyl acids such as acetic acid, propionic acid, octanoic acid, lauric acid, stearic acid, or malonic acid, succinic acid, adipic acid, sebacic acid, hexahydrophthalic acid A salt of a dibasic acid, a salt of a butanetetracarboxylic acid, benzoic acid, toluic acid, o-phthalic acid, isophthalic acid, terephthalic acid, trimesic acid, or the like, or a mixture of aromatic carboxylates alone or in combination. Among the transition metal catalysts, an organic acid salt of Co is preferable from the viewpoint of oxygen absorption, and Co stearate is particularly preferable from the viewpoint of safety and workability.

  The transition metal catalyst is preferably added to the polyamide resin A and then mixed with the polyolefin resin. The transition metal catalyst is preferably added so that the concentration of all transition metals in the catalyst with respect to the polyamide resin A is 10 ppm to 5000 ppm, preferably 50 ppm to 3000 ppm. In this case, compared with the case where the addition amount is out of the above range, the oxygen absorption performance of the polyamide resin A can be improved, and the deterioration of the resin processability due to the decrease in the viscosity can be prevented.

  The total content of the transition metal catalyst and the polyamide resin A in the oxygen-absorbing resin composition is 15 to 60% by mass, preferably 17 to 60% by mass, more preferably 20 to 60% by mass, and 25 to 50% by mass. Is particularly preferred. When the content of the polyamide resin A including the transition metal catalyst in the oxygen-absorbing resin layer is less than 15% by mass or exceeds 60% by mass, the oxygen-absorbing ability is lowered. Moreover, when it exceeds 60 mass%, the resin deterioration by oxidation of the polyamide resin A will arise, and problems, such as a strength fall, will generate | occur | produce.

Another method for producing the oxygen-absorbing resin composition of the present invention is preferably a method for producing an oxygen-absorbing resin composition in which a masterbatch containing a polyolefin resin and a transition metal catalyst and a polyamide resin are melt-kneaded.
The transition metal catalyst is kneaded with the polyolefin resin to produce a master batch, and then melt mixed with the polyamide resin A to obtain an oxygen-absorbing resin composition. The transition metal catalyst is added so that the concentration of all transition metals in the catalyst with respect to the polyolefin resin is preferably 200 ppm to 5000 ppm, more preferably 300 ppm to 3000 ppm. In this case, the oxygen absorption performance of the polyamide resin A can be enhanced as compared with the case where the addition amount is out of the above range. Moreover, when it exceeds 5000 ppm, it may become difficult to manufacture a masterbatch, and it may become impossible to manufacture what has a uniform property. If a transition metal catalyst is added to the polyamide resin A, the resin processability is deteriorated due to a decrease in the viscosity of the polyamide resin A.

  The oxygen-absorbing resin composition of the present invention can be used as an oxygen absorbent material as a resin composition. That is, an oxygen-absorbing resin composition in the form of a pellet or sheet may be filled into a breathable packaging material and used as a sachet-shaped oxygen absorber. When making into pellet form, in order to keep contact with oxygen, it is preferable to grind | pulverize and make into powder form. Moreover, when setting it as a sheet form, it is preferable to extend | stretch and provide a space | gap between the sea-island-like layers of the polyamide resin A and polyolefin resin. As the polyolefin resin for stretching, high-density polyethylene is preferably used.

  In addition, the oxygen-absorbing resin composition of the present invention is a film-like or sheet-like, comprising at least a sealant layer containing a polyolefin resin, an oxygen-absorbing layer containing an oxygen-absorbing resin composition, and a gas barrier layer containing a gas-barrier substance. It is preferable to use it as an oxygen-absorbing multilayer body.

  In this case, the sealant layer containing the polyolefin resin is preferably the same as the polyolefin resin used in the oxygen-absorbing resin composition in consideration of compatibility. Examples of the gas barrier material include various vapor-deposited films such as silica, alumina and aluminum, ethylene-vinyl alcohol copolymer, MXD6, polyvinylidene chloride, amine-epoxy curing agent and other gas barrier resins, aluminum foil and other metal foils, A known gas barrier material is used.

  Although there is no restriction | limiting in particular in the thickness of the oxygen absorption resin composition at the time of using as an oxygen absorption layer, 5-100 micrometers is preferable and 10-50 micrometers is especially preferable. In this case, as compared with the case where the thickness is out of the above range, the oxygen-absorbing resin composition can further improve the performance of absorbing oxygen and can prevent the workability and economy from being impaired. Further, the thickness of the sealant layer is preferably less because the sealant layer becomes an isolation layer from the layer containing the oxygen-absorbing resin composition, but is preferably 2 to 50 μm, particularly preferably 5 to 30 μm. In this case, compared with the case where the thickness is out of the above range, the oxygen absorbing rate of the oxygen absorbing resin composition can be further increased, and the workability can be prevented from being impaired. When processing into a film or sheet, considering the workability, the thickness ratio of the sealant layer and the oxygen absorbing layer is preferably 1: 0.5 to 1: 3, and 1: 1 to 1: 2.5. Particularly preferred.

  In addition, when considering the processability when forming a multilayer body, it is preferable to interpose an intermediate layer containing a polyolefin resin between a gas barrier layer containing a gas barrier substance and an oxygen absorbing layer containing an oxygen absorbing resin composition. The thickness of the intermediate layer is preferably substantially the same as the thickness of the sealant layer from the viewpoint of workability. In this case, considering variations due to processing, the thickness is the same if the thickness ratio is within ± 10%.

  The obtained oxygen-absorbing multilayer body can be used as an oxygen-absorbing paper container by laminating a paper substrate on the outer layer of the gas barrier layer. The processability of the paper container laminated with the paper base material is preferably 60 μm or less, particularly preferably 50 μm or less, at the inner side of the gas barrier layer. When the internal thickness is larger than that of the gas barrier layer, a problem arises in processability to a container when a paper base material is laminated and formed into a container shape.

  The obtained oxygen-absorbing multilayer body can be prepared as a film, processed into a bag shape and a lid material, and used. The obtained oxygen-absorbing multilayer body can be produced as a sheet and molded into a tray or a cup. Moreover, the obtained bag-shaped container and cup-shaped container can perform 80-100 degreeC boil sterilization process, 100-135 degreeC semi-retort sterilization process, retort sterilization process, and high retort sterilization process. Moreover, it is preferably used for a microwave cooking-compatible pouch that fills a bag-like container with contents such as food, provides an opening, and releases steam from the opening when cooking with a microwave oven. it can.

  Since this oxygen-absorbing resin composition can absorb oxygen regardless of the presence or absence of moisture in the preserved product, dry foods such as powder seasonings, powdered coffee, coffee beans, rice, tea, beans, rice crackers, rice crackers, etc. It can be suitably used for health foods such as pharmaceuticals and vitamins. In addition, the oxygen-absorbing resin composition obtained in the present invention can be suitably used for alcoholic beverages and carbonated beverages that cannot be stored due to the presence of iron, unlike conventional oxygen-absorbing resin compositions using iron powder. .

  Other items to be preserved include processed rice such as polished rice, cooked rice, red rice, and glutinous rice, cooked foods such as soup, stew, and curry, fruits, mutton, pudding, cakes, sweets such as buns, tuna, and fish shellfish Examples include fishery products, processed milk products such as cheese and butter, processed meat products such as meat, salami, sausage and ham, vegetables such as carrots, potatoes, asparagus and shiitake mushrooms, and eggs.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In the examples and comparative examples, various physical property values were measured by the following measuring methods and measuring apparatuses.

(Measurement method of Tg)
Tg was measured according to JIS K7122. The measuring apparatus used was “DSC-60” manufactured by Shimadzu Corporation.

(Measuring method of melting point)
The melting point was determined by measuring the DSC melting peak temperature according to ISO11357. The measuring apparatus used was “DSC-60” manufactured by Shimadzu Corporation.

(Measurement method of number average molecular weight)
The number average molecular weight was measured by GPC-LALLS. As a measuring apparatus, “Shodex GPC-2001” manufactured by Showa Denko KK was used.

(Measurement method of MFR)
The MFR of each resin is measured under a load of 2160 g at a specific temperature using an apparatus in accordance with JIS K7210 (“Melt Indexer” manufactured by Toyo Seiki Seisakusho Co., Ltd.), and the value is described together with the temperature. (Unit: “g / 10 min”). In addition, when MFR was measured based on JISK7210, it was described that much.

(Measurement method of oxygen permeability coefficient)
The oxygen transmission coefficient was measured using “OX-TRAN-2 / 21” manufactured by MOCON under the conditions of 23 ° C., 60% RH and a cell area of 50 cm ² .

(Method for measuring terminal amino group concentration)
0.5 g of sample was dissolved in 30 mL of phenol / ethanol = 4/1 (volume ratio), 5 mL of methanol was added, and an automatic titrator with 0.01 N hydrochloric acid as a titrant (“COM-2000” manufactured by Hiranuma Seisakusho) Titration with The same operation titrated without adding a sample was used as a blank, and the terminal amino group concentration was calculated from the following formula.
Terminal amino group concentration (μeq / g) = (A−B) × f × 10 / C
(A: titer (mL), B: blank titer (mL), f: factor of normal solution, C: sample amount (g)).

(Measurement method of terminal carboxyl group concentration)
0.5 g of a sample was dissolved in 30 mL of benzyl alcohol, 10 mL of methanol was added, and titrated with an automatic titration apparatus (“COM-2000” manufactured by Hiranuma Seisakusho) with 0.01 N sodium hydroxide solution as a titrant. The same operation titrated without adding a sample was used as a blank, and the terminal carboxyl group concentration was calculated from the following formula.
Terminal carboxyl group concentration (μeq / g) = (A−B) × f × 10 / C
(A: titer (mL), B: blank titer (mL), f: factor of normal solution, C: sample amount (g)).

(Measurement method of semi-crystallization time)
When the pellet is melted at each temperature and the resin is crystallized at each temperature, the time for all to crystallize is called the crystallization time, and the time for reaching 50% crystallization is called the semi-crystallization time. The half crystallization time was measured by the depolarized intensity method. That is, when the sample pellets are irradiated with light and the sample pellets are crystallized, the amount of light transmission decreases and becomes stable when the amount of light transmission is stabilized. The time is defined as the crystallization time, and the amount of light transmission is 50%. The time to reach was defined as the half crystallization time. Although the crystallization time and the half crystallization time differ depending on the measurement temperature, in the following description, among the half crystallization times at each temperature, the one with the shortest half crystallization time is referred to as “half crystallization time”. Described. In addition, a “polymer crystallization rate measuring apparatus MK-701 type” manufactured by Kotaki was used to measure the crystallization time and the semi-crystallization time.

(Measurement method of yellowness index)
For the yellowness index (YI), 5 g of pellets were weighed and placed on a round cell having a diameter of 30 mm, and reflection measurement was performed using “ZE-2000” manufactured by Nippon Denshoku Industries Co., Ltd.

(Synthesis conditions by melt polymerization of polyamide resin)
After adipic acid is heated and melted at 170 ° C. in a reaction can, the diamine component is gradually added dropwise continuously so that the molar ratio with adipic acid is about 1: 1 while stirring the contents. And the temperature was raised to 240 ° C. After completion of dropping, the temperature was raised to 260 ° C. and the reaction was continued. After completion of the reaction, the inside of the reaction can was slightly pressurized with nitrogen, the strand was extruded from a die head having holes, and pelletized with a pelletizer.

(Synthesis conditions by solid phase polymerization of polyamide resin)
The pellets obtained by melt polymerization by the above method were charged into a rotary tumbler equipped with a heating device, the pressure inside the tumbler was reduced to 1 torr or less while rotating, and the operation of bringing the pressure to normal pressure with nitrogen was performed three times. Thereafter, the inside of the apparatus was heated while rotating the tumbler to 30 torr or less, the inside of the apparatus was adjusted to 150 ° C. or more, and the reaction was performed at that temperature for a predetermined time. Then, it cooled to 60 degreeC and obtained the polyamide resin.

Example 1
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above synthesis conditions using metaxylylenediamine: sebacic acid: adipic acid in a molar ratio of 0.994: 0.5: 0.5. (Hereinafter, the polyamide resin is referred to as polyamide 1). At this time, sodium hypophosphite monohydrate and trisodium phosphate dodecahydrate were added to 100 ppm in terms of phosphorus atom concentration so that the phosphorus atom concentration in polyamide 1 was 200 ppm. The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 160 ° C., and the polymerization time was 5 hours. Polyamide 1 has a Tg of 65 ° C., a melting point of 174 ° C., a semicrystallization time of 2000 seconds or more, a terminal amino group concentration of 17.8 μeq / g, a terminal carboxyl group concentration of 70.5 μeq / g, a number average molecular weight of 23500, and 240 ° C. The MFR was 10.7 g / 10 min. Moreover, the unstretched film was produced with the obtained polyamide 1 single-piece | unit. The produced polyamide 1 single-piece unstretched film had an oxygen permeability coefficient of 0.58 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

  Cobalt stearate was added to polyamide 1 as a transition metal catalyst by a side feed to molten polyamide 1 with a twin screw extruder so that the cobalt concentration was 400 ppm. Furthermore, linear low density polyethylene (product name: Ube Maruzen Polyethylene Co., Ltd.) “Umerit” is used as a polyolefin resin in a mixture of the obtained polyamide and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 1). 4540F ”, MFR 4 g / 10 min (measured according to JIS K7210), MFR 7.6 g / 10 min at 250 ° C., hereinafter referred to as LLDPE), cobalt stearate-containing polyamide 1: LLDPE = 40: 60 Then, it was melt-kneaded at 240 ° C. to obtain an oxygen-absorbing resin composition. The oxygen-absorbing composition had a YI of 1.5. When the film appearance was confirmed by visual observation, no coloring was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Next, a film made of a single layer oxygen absorbing resin composition having a thickness of 50 μm is obtained using the oxygen absorbing resin composition, the film is made into two 10 × 10 mm films, and the humidity in the bag is set to the film. A gas barrier bag made of an aluminum foil laminated film as 100% was filled and sealed two by 300 cc each with air, stored at 23 ° C., and the total amount of oxygen absorbed for 7 days after sealing was measured. These results are shown in Table 2.

(Example 2)
Polyamide resin was synthesized by using only meta-xylylenediamine: adipic acid at a molar ratio of 0.991: 1 and performing only melt polymerization under the above synthesis conditions. At this time, sodium hypophosphite monohydrate and trisodium phosphate dodecahydrate were added to 90 ppm and 210 ppm in terms of phosphorus atom concentration, respectively, so that the phosphorus atom concentration in the polyamide was 300 ppm. . However, the dropping time was 2 hours, the polymerization temperature after completion of dropping of metaxylylenediamine in melt polymerization was 270 ° C., and the reaction time was 1 hour. After melt polymerization, 0.2 wt% of phthalic anhydride was added to the synthesized polyamide resin, melt kneaded at 270 ° C. with a twin screw extruder, and the terminal amino group was sealed (hereinafter, the polyamide resin is referred to as polyamide 2). To do). Polyamide 2 has a Tg of 83 ° C., a melting point of 238 ° C., a semicrystallization time of 40 seconds, a terminal amino group concentration of 24.2 μeq / g, a terminal carboxyl group concentration of 92.2 μeq / g, a number average molecular weight of 23500, and 240 ° C. Since it was near the melting point, MFR could not be measured, MFR at 250 ° C. was measured, and MFR at 250 ° C. was 14.3 g / 10 min. Moreover, the unstretched film was produced with the obtained polyamide 2 single-piece | unit. The oxygen permeability coefficient of the prepared unstretched film of polyamide 2 alone was 0.07 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

Thereafter, in the same manner as in Example 1, cobalt stearate was added so as to have a cobalt concentration of 400 ppm, and LLDPE was added to the obtained mixture of polyamide 2 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 2). Was melt-kneaded at a weight ratio of cobalt stearate-containing polyamide 2: LLDPE = 18: 82 at 280 ° C. to obtain an oxygen-absorbing resin composition. YI of the oxygen-absorbing composition was 1.1. When the film appearance was confirmed by visual observation, coloring was not recognized. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.
Example 3
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above synthesis conditions using metaxylylenediamine: adipic acid: isophthalic acid in a molar ratio of 0.989: 0.9: 0.1. (Hereinafter, the polyamide resin is referred to as polyamide 3). At this time, sodium hypophosphite monohydrate and trisodium phosphate dodecahydrate are added so as to be 70 ppm and 30 ppm in terms of phosphorus atom concentration, respectively, so that the phosphorus atom concentration in polyamide 3 is 100 ppm. did. The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 205 ° C., and the polymerization time was 5 hours. Polyamide 3 has a Tg of 91 ° C., a melting point of 234 ° C., a semicrystallization time of 200 seconds, a terminal amino group concentration of 15.1 μeq / g, a terminal carboxyl group concentration of 89.3 μeq / g, a number average molecular weight of 25000, and 240 ° C. Since it was near the melting point, MFR could not be measured, MFR at 250 ° C. was measured, and MFR at 250 ° C. was 14.8 g / 10 min. Moreover, the unstretched film was produced with the obtained polyamide 2 single-piece | unit. The oxygen permeability coefficient of the prepared unstretched film of polyamide 2 alone was 0.09 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

Thereafter, in the same manner as in Example 1, cobalt stearate was added so as to have a cobalt concentration of 400 ppm, and LLDPE was added to the obtained mixture of polyamide 3 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 3). Was melt-kneaded at a weight ratio of cobalt stearate-containing polyamide 3: LLDPE = 50: 50 at 280 ° C. to obtain an oxygen-absorbing resin composition. The oxygen-absorbing composition had a YI of 2.1. When the film appearance was confirmed by visual observation, no coloring was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.
Example 4
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above-mentioned synthesis conditions using metaxylylenediamine: sebacic acid: adipic acid in a molar ratio of 0.994: 0.4: 0.6. (Hereinafter, the polyamide resin is referred to as polyamide 4). At this time, sodium dihydrogen phosphate monohydrate was added so as to be 460 ppm in terms of phosphorus atom concentration so that the phosphorus atom concentration in polyamide 4 was 460 ppm. Melt polymerization and solid phase polymerization were carried out under the same conditions as in Example 1. Polyamide 4 has a Tg of 68 ° C., a melting point of 185 ° C., a semicrystallization time of 2000 seconds or more, a terminal amino group concentration of 19.7 μeq / g, a terminal carboxyl group concentration of 73.6 μeq / g, a number average molecular weight of 24500, and an MFR of 240 ° C. It was 9.9 g / 10 minutes. Moreover, the unstretched film was produced with the obtained polyamide 4 single-piece | unit. The oxygen permeability coefficient of the prepared unstretched film of polyamide 4 alone was 0.61 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

Thereafter, in the same manner as in Example 1, cobalt stearate was added so as to have a cobalt concentration of 400 ppm, and LLDPE was added to the obtained mixture of polyamide 4 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 4). Was melt-kneaded at 240 ° C. in a weight ratio of cobalt stearate-containing polyamide 4: LLDPE = 30: 70 to obtain an oxygen-absorbing resin composition. YI of the oxygen absorbing composition was 3.8, and when the film appearance was confirmed by visual observation, slight coloration was confirmed. Moreover, when the odor was confirmed, it was confirmed that a slight odor was generated. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.
(Example 5)
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above-mentioned synthesis conditions using metaxylylenediamine: adipic acid: isophthalic acid in a molar ratio of 0.995: 0.85: 0.15. (Hereinafter, the polyamide resin is referred to as polyamide 5). At this time, disodium hydrogen phosphite pentahydrate was added so that the phosphorus atom concentration in the polyamide 5 was 50 ppm in terms of phosphorus atom concentration so that the phosphorus atom concentration was 50 ppm. Melt polymerization and solid phase polymerization were carried out under the same conditions as in Example 3. Polyamide 5 has a Tg of 96 ° C., a melting point of 229 ° C., a half crystallization time of 230 seconds, a terminal amino group concentration of 18.7 μeq / g, a terminal carboxyl group concentration of 68.8 μeq / g, a number average molecular weight of 24200, and 240 ° C. Since it was near the melting point, MFR could not be measured, MFR at 250 ° C. was measured, and MFR at 250 ° C. was 15.1 g / 10 min. Moreover, the unstretched film was produced with the obtained polyamide 5 simple substance. The oxygen permeability coefficient of the prepared unstretched film of polyamide 5 alone was 0.12 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

  Thereafter, in the same manner as in Example 1, cobalt stearate was added so as to have a cobalt concentration of 400 ppm, and LLDPE was added to the obtained mixture of polyamide 5 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 5). Was melt-kneaded at a weight ratio of cobalt stearate-containing polyamide 5: LLDPE = 35: 65 at 280 ° C. to obtain an oxygen-absorbing resin composition. YI of the oxygen-absorbing composition was 4.2. When the film appearance was confirmed by visual observation, a slight coloration was confirmed. Moreover, when the odor was confirmed, it was confirmed that a slight odor was generated. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.

(Example 6)
Cobalt stearate was added to LLDPE by side feed to the melted LLDPE with a twin screw extruder so that the cobalt concentration was 600 ppm. Furthermore, polyamide 1 was melt kneaded at 240 ° C. in a weight ratio of polyamide 1: cobalt stearate-containing LLDPE = 35: 65 to the obtained mixture of LLDPE and cobalt stearate to obtain an oxygen-absorbing resin composition. . The oxygen-absorbing composition had a YI of 1.8. When the film appearance was confirmed by visual observation, no coloring was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.

(Comparative Example 1)
Polyamide resin was synthesized by performing melt polymerization and solid phase polymerization under the above synthesis conditions using metaxylylenediamine: adipic acid: isophthalic acid in a molar ratio of 0.990: 0.80: 0.20. (Hereinafter, the polyamide resin is referred to as polyamide 6). At this time, disodium hydrogen phosphite pentahydrate and disodium hydrogen phosphate were added to 300 ppm in terms of phosphorus atom concentration so that the phosphorus atom concentration in polyamide 6 was 600 ppm. Melt polymerization and solid phase polymerization were carried out under the same conditions as in Example 3. Polyamide 6 has a Tg of 102 ° C., a melting point of 220 ° C., a half crystallization time of 310 seconds, a terminal amino group concentration of 16.0 μeq / g, a terminal carboxyl group concentration of 87.5 μeq / g, a number average molecular weight of 24,000, and at 240 ° C. Since it was near the melting point, MFR could not be measured, MFR at 250 ° C. was measured, and MFR at 250 ° C. was 15.1 g / 10 min. Moreover, the unstretched film was produced with the obtained polyamide 6 simple substance. The oxygen permeability coefficient of the prepared unstretched film of polyamide 6 was 0.14 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

  Thereafter, in the same manner as in Example 1, cobalt stearate was added to a cobalt concentration of 400 ppm, and LLDPE was added to the obtained mixture of polyamide 6 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 6). Was melt-kneaded at a weight ratio of cobalt stearate-containing polyamide 6: LLDPE = 45: 55 at 280 ° C. to obtain an oxygen-absorbing resin composition. The oxygen-absorbing composition had a YI of 1.9. When the appearance of the film was visually confirmed, no coloration was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.

(Comparative Example 2)
A polyamide resin was synthesized by performing melt polymerization and solid-phase polymerization under the above-mentioned synthesis conditions using metaxylylenediamine: adipic acid in a molar ratio of 1: 1 (hereinafter, the polyamide resin is referred to as polyamide 7). To do). At this time, sodium hypophosphite monohydrate and trisodium phosphate dodecahydrate were added so as to be 100 ppm in terms of phosphorus atom concentration so that the phosphorus atom concentration in polyamide 7 would be 200 ppm. The dropping time was 2 hours, the reaction time for melt polymerization was 1 hour, the pressure in the apparatus during solid phase polymerization was 1 torr or less, the polymerization temperature was 205 ° C., and the polymerization time was 8 hours. Polyamide 7 has a Tg of 83 ° C., a melting point of 238 ° C., a semicrystallization time of 40 seconds, a terminal amino group concentration of 38.7 μeq / g, a terminal carboxyl group concentration of 40.5 μeq / g, a number average molecular weight of 24500, and 240 ° C. Since it was near the melting point, MFR could not be measured, MFR at 250 ° C. was measured, and MFR at 250 ° C. was 13.8 g / 10 min. Moreover, the unstretched film was produced with the obtained polyamide 7 single-piece | unit. The oxygen permeability coefficient of the prepared unstretched film of polyamide 7 alone was 0.07 cc · mm / (m ² · day · atm) (23 ° C. · 60% RH). These results are shown in Table 1.

  Thereafter, in the same manner as in Example 1, cobalt stearate was added so as to have a cobalt concentration of 400 ppm, and LLDPE was added to the obtained mixture of polyamide 7 and cobalt stearate (hereinafter referred to as cobalt stearate-containing polyamide 7). Was melt-kneaded at a weight ratio of cobalt stearate-containing polyamide 7: LLDPE = 45: 55 at 280 ° C. to obtain an oxygen-absorbing resin composition. The oxygen-absorbing composition had a YI of 2.2. When the film appearance was confirmed by visual observation, no coloring was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.

(Comparative Example 3)
An oxygen-absorbing resin composition was obtained in the same manner as in Example 1 except that the weight ratio at the time of melt kneading was changed to cobalt stearate-containing polyamide 1: LLDPE = 10: 90. The oxygen absorbing composition had a YI of 1.4. When the film appearance was confirmed by visual observation, no coloring was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.

(Comparative Example 4)
An oxygen-absorbing resin composition was obtained in the same manner as in Example 1 except that the weight ratio during melt-kneading was changed to cobalt stearate-containing polyamide 1: LLDPE = 80: 20. The oxygen-absorbing composition had a YI of 2.0. When the film appearance was visually confirmed, no coloration was observed. Moreover, when odor was confirmed, it confirmed that there was no odor. Further, a film was produced in the same manner as in Example 1, and the oxygen absorption amount of the film was measured. These results are shown in Table 2.

  As is clear from Examples 1 to 6, the oxygen-absorbing resin composition of the present invention was a resin composition that exhibited good oxygen-absorbing performance, good color tone, and almost no odor generation. On the other hand, in Comparative Example 1 in which the phosphorus atom concentration of the polyamide resin exceeded 500 ppm, although the color tone of the oxygen-absorbing resin composition was good and no odor generation was observed, the oxygen absorption amount decreased.

Compared to Example 2, in Comparative Example 2 in which the molar ratio of MXDA to adipic acid was increased, the terminal amino group concentration of the polyamide resin exceeded 30 μeq / g, and the oxygen absorption amount decreased.

On the other hand, the total content of the transition metal catalyst and the polyamide resin A in the oxygen-absorbing resin layer was less than 15% by mass, and the content of the transition metal catalyst and the polyamide resin A in the oxygen-absorbing resin composition was as follows. In Comparative Example 4 exceeding 60% by mass, the oxygen absorption amount decreased.

  The present invention blends a specific polyamide, transition metal and polyolefin resin containing a specific concentration of a phosphorus atom-containing compound at a specific ratio, so that the oxygen absorption performance is excellent and the resin strength after storage is maintained. Furthermore, it was an oxygen-absorbing resin composition having excellent processability, good color tone and no odor generation.

Claims (2)

An oxygen-absorbing resin composition containing a polyolefin resin, a transition metal catalyst, and a polyamide resin obtained by polycondensation with an aromatic diamine and a dicarboxylic acid, wherein the phosphorus atom content in the polyamide resin is 500 ppm or less, and An oxygen-absorbing resin composition, wherein the polyamide resin has a terminal amino group concentration of 30 μeq / g or less, and a total content of the transition metal catalyst and the polyamide resin is 15 to 60% by mass. The oxygen-absorbing resin according to claim 1, wherein the phosphorus atom is contained in one or more compounds selected from alkali metal or alkaline earth metal hypophosphites, phosphites, and phosphates. Composition.