JP2022082179A - Resin composition, molding, and method for disposing of polyamide resin - Google Patents

Abstract

To provide a resin composition excellent in biodegradability, a molding formed from the resin composition, and a method for disposing of a polyamide resin.SOLUTION: The resin composition contains a polyamide resin and a cobalt salt. The polyamide resin contains a xylylenediamine-based polyamide resin containing a diamine-derived constituent unit and a dicarboxylic acid-derived constituent unit, wherein 50 mol% or more of the diamine-derived constituent unit is derived from xylylenediamine and 50 mol% or more of the dicarboxylic acid-derived constituent unit is derived from a C8-22 α,ω-linear aliphatic dicarboxylic acid. Para-xylylenediamine accounts for 0.1 mol% or more of the xylylenediamine.SELECTED DRAWING: None

Description

The present invention relates to a method for disposing of a resin composition, a molded product, and a polyamide resin.

Polyamide resins have excellent physical and chemical properties. Therefore, it is widely used in various applications such as electrical and electronic device parts, packaging materials for foods and pharmaceuticals, and the like. For example, in Patent Document 1, a layer in which a transition metal salt such as cobalt organic acid is mixed with a polyamide resin is provided, and the metaxylylene group-containing polyamide resin is catalytically oxidized to absorb oxygen, thereby absorbing oxygen in addition to gas barrier properties. So-called high barrier containers with added sex are disclosed.

Japanese Unexamined Patent Publication No. 2002-321774

As mentioned above, polyamide resins have been used for various purposes, but as part of recent environmental conservation efforts, it is required that polyamide resins can be biodegraded.
An object of the present invention is to solve such a problem, and to provide a resin composition having excellent biodegradability, a molded product formed from the resin composition, and a method for disposing of a polyamide resin. The purpose is.

As a result of studies by the present inventor based on the above problems, it has been found that the above problems can be solved by blending a cobalt salt with a specific type of polyamide resin.
Specifically, the above problem was solved by the following means.
<1> The polyamide resin contains a polyamide resin and a cobalt salt, the polyamide resin contains a diamine-derived structural unit and a diamine-derived structural unit, and 50 mol% or more of the diamine-derived structural unit is derived from xylylene diamine. However, 50 mol% or more of the constituent unit derived from the dicarboxylic acid contains a xylylene diamine-based polyamide resin derived from an α, ω-linear aliphatic diamine acid having 8 to 22 carbon atoms, and 0. A resin composition in which 1 mol% or more is paraxylylene diamine.
<2> The resin composition according to <1>, wherein the mass ratio of the xylylenediamine structure in the xylylenediamine-based polyamide resin is 20 to 70% by mass; where the mass ratio of the xylylenediamine structure is. , [(Mass of xylylenediamine structure in xylylenediamine-based polyamide resin) / (mass of the entire xylylenediamine-based polyamide resin)] × 100.
<3> The resin composition according to <1> or <2>, wherein the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms contains sebacic acid and / or dodecanedioic acid.
<4> The resin composition according to <1> or <2>, wherein the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms contains a dodecanedioic acid.
<5> The resin composition according to any one of <1> to <4>, wherein 20 mol% or more of the constituent unit derived from the diamine is derived from paraxylylenediamine.
<6> The resin composition according to any one of <1> to <5>, wherein the cobalt salt contains a carboxylic acid salt of cobalt.
<7> The resin composition according to any one of <1> to <5>, wherein the cobalt salt contains cobalt stearate.
<8> The content of the cobalt salt is 10 to 2000 mass ppm with respect to 100 parts by mass of the xylylenediamine-based polyamide resin based on the cobalt atom, to any one of <1> to <7>. The resin composition described.
<9> The resin composition according to any one of <1> to <8>, which is biodegradable.
<10> The resin composition according to any one of <1> to <9>, wherein the degree of biodegradation after storing the resin composition in a compost environment for 90 days is 10% or more: Here. The degree of biodegradation (%) is [(total CO ₂ generation amount during storage for 90 days in a compost environment) / (theoretical carbon dioxide generation amount calculated from the composition formula)] × 100.
<11> A molded product formed from the resin composition according to any one of <1> to <10>.
<12> The molded body according to <11>, which is a fishing net.
<13> A method for disposing of a polyamide resin, which comprises biodegrading the resin composition according to any one of <1> to <10> or the molded product according to <11> or <12>.

INDUSTRIAL APPLICABILITY According to the present invention, it has become possible to provide a resin composition having excellent biodegradability, a molded product formed from the resin composition, and a method for disposing of a polyamide resin.

Hereinafter, embodiments for carrying out the present invention (hereinafter, simply referred to as “the present embodiment”) will be described in detail. The following embodiments are examples for explaining the present invention, and the present invention is not limited to the present embodiment.
In addition, in this specification, "-" is used in the meaning which includes the numerical values described before and after it as the lower limit value and the upper limit value.
In the present specification, various physical property values and characteristic values shall be at 23 ° C. unless otherwise specified.
As used herein, ppm means mass ppm.

The resin composition of the present embodiment contains a polyamide resin and a cobalt salt, and the polyamide resin contains a diamine-derived structural unit and a diamine-derived structural unit, and is 50 mol% or more of the diamine-derived structural unit. Is derived from xylylene diamine, and 50 mol% or more of the constituent unit derived from the dicarboxylic acid contains a xylylene diamine-based polyamide resin derived from α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms. It is characterized in that 0.1 mol% or more of xylylene diamine is paraxylylene diamine. With such a configuration, it becomes possible to provide a resin composition having excellent biodegradability. The reason for this is presumed to be as follows.
In order to biodegrade the resin, for example, when it is left in a compost environment for a long period of time, microorganisms act on the resin to reduce the molecular weight of the resin. As a result, microorganisms are more likely to penetrate into the resin, biodegradation proceeds, and decompositions into oligomers, monomers, and even smaller molecules. However, since the polyamide resin generally has a strong amide bond and is usually a crystalline resin, it is not easily affected by microorganisms and its molecular weight is unlikely to decrease. Therefore, the polyamide resin is less likely to be decomposed by microorganisms. In the present embodiment, by using a predetermined xylylenediamine-based polyamide resin as the polyamide resin, the NH ₂ -CH ₂ -benzene ring moiety of the xylylenediamine is first oxidatively decomposed by cobalt, and the benzyl moiety and NH are used. It was speculated that it would be disconnected between _two . As a result, it is presumed that the decrease in the molecular weight of the xylylenediamine-based polyamide resin was promoted, and subsequently the biodegradation by microorganisms could be promoted.
Hereinafter, the details of the resin composition of the present embodiment will be described.

<Polyamide resin>
The resin composition of the present embodiment contains a xylylenediamine-based polyamide resin. The xylylene diamine-based polyamide resin contains a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, and 50 mol% or more of the diamine-derived structural unit is derived from xylylene diamine and the dicarboxylic acid-derived structural unit. More than 50 mol% of this is a polyamide resin derived from an α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms. By using such a xylylenediamine-based polyamide resin and blending a cobalt salt, a resin composition having excellent biodegradability can be obtained.

In the xylylenediamine-based polyamide resin, 50 mol% or more of the constituent unit derived from diamine is derived from xylylenediamine, but it is preferably 70 mol% or more, and more preferably 90 mol% or more. , 95 mol% or more, more preferably 99 mol% or more. The upper limit may be 100 mol%.

The amount of xylylenediamine is 0.1 mol% or more of paraxylylenediamine. By containing paraxylylenediamine, biodegradability can be improved. It is presumed that one of the reasons for this is that the paraxylylenediamine skeleton tends to be more susceptible to decomposition by microorganisms than the metaxylylenediamine skeleton. It is generally known that the susceptibility to decomposition by microorganisms largely depends on the structure of the molecule, and it is presumed that linear paraxylylenediamine has a structure that is more susceptible to decomposition by microorganisms. To. Therefore, it is presumed that the degree of biodegradation as a resin is improved by replacing methylylenediamine with paraxylylenediamine. In addition to this, it is presumed that the paraxylylene diamine skeleton serves as a starting point for decomposition by microorganisms, further reducing the molecular weight of the resin, and as a result, biodegradation is promoted.
The proportion of paraxylylenediamine in the xylylenediamine is preferably 10 mol% or more, more preferably 20 mol% or more, still more preferably 25 mol% or more. The upper limit is 100 mol%, but may be, for example, 80 mol% or less, further 60 mol% or less, and particularly 45 mol% or less.
In the present embodiment, the xylylenediamine preferably contains 0 to 99.9 mol% of metaxylylenediamine and 0.1 to 100 mol% of paraxylylenediamine, preferably 0 to 80 mol% of meta. More preferably, it contains xylylenediamine and 20-100 mol% paraxylylenediamine. Further, in the xylylenediamine, the total of the metaxylylenediamine and the paraxylylenediamine preferably occupies 95 mol% or more, more preferably 99 mol% or more, still more preferably 100 mol%.
Further, in the present embodiment, the xylylenediamine-based polyamide resin contains a structural unit derived from para-xylylenediamine, which tends to promote the decomposition of the xylylenediamine-based polyamide resin by the cobalt atom.

Diamine components other than xylylenediamine include tetramethylenediamine, pentamethylenediamine, 2-methylpentanediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2, Aliphatic diamines such as 2,4-trimethyl-hexamethylenediamine and 2,4,4-trimethylhexamethylenediamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1, 3-Diaminocyclohexane, 1,4-diaminocyclohexane, bis (4-aminocyclohexyl) methane, 2,2-bis (4-aminocyclohexyl) propane, bis (aminomethyl) decalin, bis (aminomethyl) tricyclodecane, etc. Examples of diamines having an aromatic ring such as alicyclic diamine, bis (4-aminophenyl) ether, paraphenylenediamine, and bis (aminomethyl) naphthalene can be exemplified. Can be used.

In the xylylene diamine-based polyamide resin, the constituent unit derived from the dicarboxylic acid is 70 mol% or more, although 50 mol% or more is derived from the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms. It is preferably 90 mol% or more, more preferably 95 mol% or more, still more preferably 99 mol% or more. The upper limit may be 100 mol%.
The number of carbon atoms in the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms is preferably 10 or more, and more preferably 11 or more. By setting the value to the lower limit or higher, it tends to be more susceptible to biodegradation by microorganisms. Further, the carbon number of the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms is preferably 21 or less, more preferably 20 or less, still more preferably 18 or less. It is more preferably 14 or less. By setting the value to the upper limit or less, the hydrophilicity is improved and it tends to be more susceptible to decomposition by microorganisms. The number of carbon atoms in the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms is particularly preferably 12.
Specific examples of the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms include suberic acid, azelaic acid, sebacic acid, 1,11-undecanedioic acid, 1,12-dodecanedioic acid, and 1,. 13-Tridecaneic acid, 1,14-tetradecanedioic acid, 1,15-pentadecanedioic acid, 1,16-hexadecanoic acid, 1,17-heptadecaneic acid, 1,18-octadecanoic acid, 1,19-nonadecannic acid , 1,20-Eicosandioic acid, 1,21-heneichosandioic acid, 1,22-docosanedioic acid, eg, sebacic acid, 1,12-dodecanedioic acid, 1,14-tetradecanedioic acid, 1,16. -Hexadecanoic acid, 1,18-octadecanoic acid, 1,20-eicosandioic acid, 1,21-heneicosanedioic acid, 1,22-docosanedioic acid, 1,14-tetradecanedioic acid, 1,16-hexadecane Diacid, 1,18-octadecanedioic acid, eicosandioic acid, docosanedioic acid are more preferred, and sevasic acid and / or dodecanedioic acid is even more preferred. When the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms is 1,12-dodecanedioic acid, the above effect is particularly remarkable.

Examples of the dicarboxylic acid component other than the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms include α, ω-linear aliphatic dicarboxylic acid having 7 or less carbon atoms such as adipic acid, isophthalic acid, and terephthalic acid. A phthalic acid compound such as orthophthalic acid, 1,2-naphthalenedicarboxylic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 1, Examples of naphthalenedicarboxylic acids such as 7-naphthalenedicarboxylic acid, 1,8-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, and 2,7-naphthalenedicarboxylic acid can be exemplified. Seeds or a mixture of two or more can be used.

In addition, "including a structural unit derived from a diamine and a structural unit derived from a dicarboxylic acid" means that at least a part of the amide bonds constituting the xylylene diamine-based polyamide resin is formed by the bond between the dicarboxylic acid and the diamine. Further, in addition to the constituent unit derived from a dicarboxylic acid and the constituent unit derived from a diamine, other sites such as a terminal group may be included. In addition, repeating units having an amide bond not derived from the bond between the dicarboxylic acid and the diamine, a trace amount of impurities, and the like may be contained. Specifically, the xylylene diamine-based polyamide resin contains ε-caprolactam and lauro as components constituting the xylylene diamine-based polyamide resin in addition to the diamine component and the dicarboxylic acid component, as long as the effects of the present embodiment are not impaired. Lactams such as lactam and aliphatic aminocarboxylic acids such as aminocaproic acid and aminoundecanoic acid can also be used as the copolymerization component. In the present embodiment, the xylylenediamine-based polyamide resin is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass or more with a diamine-derived structural unit or a dicarboxylic acid-derived structural unit. be.

The xylylenediamine-based polyamide resin used in the present embodiment preferably has a xylylenediamine structure having a mass ratio of 20 to 70% by mass. With such a configuration, biodegradation tends to proceed more easily. Here, the mass ratio of the xylylenediamine structure is a value calculated from [(mass of the xylylenediamine structure in the polyamide resin) / (mass of the entire polyamide resin)] × 100. The xylylenediamine structure refers to a portion represented by "-HN-CH ₂ -benzene ring-CH ₂ -NH-".
The lower limit of the mass ratio of the xylylenediamine structure is preferably 35% by mass or more, and more preferably 40% by mass or more. By setting the value to the lower limit or higher, the starting point of decomposition increases, and low molecular weight components that are more susceptible to biodegradation tend to be easily generated. The upper limit of the mass ratio of the xylylenediamine structure is preferably 60% by mass or less, more preferably 50% by mass or less. By setting the value to the upper limit or less, the xylene skeleton that is less susceptible to biodegradation tends to decrease, and the degree of biodegradation of the resin as a whole tends to be further improved.

The content of the xylylenediamine-based polyamide resin in the resin composition of the present embodiment is preferably 80% by mass or more, more preferably 85% by mass or more, and 90% by mass or more in the resin composition. It is more preferably 95% by mass or more, and even more preferably 99% by mass or more. By setting the value to the lower limit or higher (the performance derived from the xylylenediamine-based polyamide resin such as high gas barrier property and high strength tends to be achieved more effectively. The upper limit is that all components other than the cobalt salt are used. This is the amount of the xylylenediamine-based polyamide resin.
The resin composition of the present embodiment may contain only one kind of xylylenediamine-based polyamide resin, or may contain two or more kinds. When two or more kinds are contained, it is preferable that the total amount is within the above range.

The resin composition of the present embodiment may or may not contain a polyamide resin other than the xylylenediamine-based polyamide resin.
Examples of the other polyamide resin include one or more types such as an aliphatic polyamide resin, an alicyclic polyamide resin, and a semi-aromatic polyamide resin, and an aliphatic polyamide resin and an alicyclic polyamide resin are preferable. Group polyamide resins are more preferred. More specifically, Polyamide 4, Polyamide 6, Polyamide 11, Polyamide 12, Polyamide 46, Polyamide 66, Polyamide 6/66, Polyamide 610, Polyamide 612, Polyamide 6T, Polyamide 6 / 6T, Polyamide 66 / 6T, Polyamide 6I , Polyamide 66 / 6I / 6, Polyamide 66 / 6I, Polyamide 6T / 6I, Polyamide 6T / 12, Polyamide 66 / 6T / 6I, Polyamide 9T, Polyamide 9I, Polyamide 9T, 9I, Polyamide 10T, 1,3-BAC10I ( 1,3-bisaminomethylcyclohexane (polyamide resin composed of sebacic acid and isophthalic acid), 1,4-BAC10I (polyamide resin composed of 1,4-bisaminomethylcyclohexane, sebacic acid and isophthalic acid) The polyamide 6 and / or the polyamide 66 is preferred.
When these other polyamide resins are contained, the content thereof is preferably 5 to 15% by mass in the resin composition.

<Cobalt salt>
The resin composition of the present embodiment contains a cobalt salt. By containing a cobalt salt, biodegradation is promoted when the resin composition of the present embodiment is placed in a compost environment or the like. In particular, since the cobalt salt has almost no adverse effect on the xylylenediamine-based polyamide resin before being placed in a compost environment, the inherent performance (particularly strength) of the resin composition when used is used. ) Is less likely to be inhibited.
The type of cobalt salt is not particularly limited and may be either a divalent salt or a trivalent salt, but a divalent salt is preferable.
The cobalt salt is preferably a cobalt carboxylate. By using the carboxylate, the reduction in molecular weight due to the oxidative decomposition of the benzyl position tends to be promoted more effectively. Then, by reducing the molecular weight of the polyamide resin, biodegradation by microorganisms is promoted thereafter.
In the case of cobalt carboxylic acid salts, the carboxylic acid is preferably an aliphatic carboxylic acid. The aliphatic carboxylic acid is not particularly specified because it does not significantly affect the oxidative decomposition behavior of the resin by cobalt, but either a linear or branched aliphatic carboxylic acid can be preferably adopted, and a linear fat can be used. More preferably, it is a group carboxylic acid. The carbon number of the aliphatic carboxylic acid is not particularly determined because it does not significantly affect the oxidative decomposition behavior of the resin by cobalt, but it is preferably 2 or more, and may be 10 or more, and may be 10 or more. It is preferably 40 or less, more preferably 30 or less, and even more preferably 24 or less. In particular, an aliphatic dicarboxylic acid having an even number of carbon atoms is preferable.
Specific examples of the aliphatic carboxylic acid include acetic acid, neodecanoic acid, lauric acid, neodecanoic acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignosericic acid, cellotic acid, montanic acid and melicic acid. From the viewpoint of physical properties, acetic acid, neodecanoic acid, and stearic acid are preferable, and stearic acid is more preferable.
The cobalt salt in this embodiment is preferably cobalt stearate. The cobalt stearate is preferably (C ₁₇ H ₃₅ COO) ₂ Co.

The content of the cobalt salt (preferably cobalt stearate) in the resin composition of the present embodiment is preferably 10% by mass or more, preferably 10% by mass or more, based on 100 parts by mass of the xylylene diamine-based polyamide resin based on the cobalt atom. It is more preferably mass ppm or more, and even more preferably 80 mass ppm or more. By setting the value to the lower limit or higher, the polyamide resin can be more effectively decomposed to a molecular weight that is susceptible to biodegradation. Further, the content of the cobalt salt in the resin composition of the present embodiment is preferably 2000 mass ppm or less, preferably 1800 mass ppm or less, based on 100 parts by mass of the xylylene diamine-based polyamide resin on a cobalt atomic basis. It is more preferably 1500 mass ppm or less, further preferably 1200 mass ppm or less, further preferably 1000 mass ppm or less, and even more preferably 800 mass ppm or less. .. By setting the value to the upper limit or less, deterioration and poor appearance during preparation of the polyamide resin tend to be effectively suppressed.
The resin composition of the present embodiment may contain only one type of cobalt salt, or may contain two or more types of cobalt salt. When two or more kinds are contained, it is preferable that the total amount is within the above range.

<Other ingredients>
The resin composition of the present embodiment may contain components other than the polyamide resin and the cobalt salt as long as the purpose and effect of the present embodiment are not impaired. Specific examples of the other components include thermoplastic resins other than polyamide resins, antioxidants, heat stabilizers, hydrolysis resistance improvers, weather stabilizers, matting agents, ultraviolet absorbers, nucleating agents, and plasticizers. , Dispersant, flame retardant, antistatic agent, anticoloring agent, antigelling agent, coloring agent, mold release agent, surface activator, dyeing agent and the like. For these details, the description in paragraphs 0130 to 0155 of Japanese Patent No. 4894982, the description in paragraph 0021 of Japanese Patent Application Laid-Open No. 2010-281827, and the description in paragraph 0036 of Japanese Patent Application Laid-Open No. 2016-223037 can be referred to. Is incorporated herein.
Examples of thermoplastic resins other than polyamide resins include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polycarbonate resins, polyoxymethylene resins, polyether ketones, polyether sulfones, and thermoplastic polys. Examples thereof include etherimide. The resin composition of the present embodiment can be configured to substantially contain no thermoplastic resin other than the polyamide resin. The term "substantially free" means that, for example, in the resin composition of the present embodiment, the content of the thermoplastic resin other than the polyamide resin is 5% by mass or less of the mass of the polyamide resin.
Further, the resin composition of the present embodiment may contain a filler such as a glass resin composition and carbon fibers, but it is preferable that the resin composition does not substantially contain the filler. The term "substantially free" means that, for example, the blending amount of the filler is 3% by mass or less of the resin composition of the present embodiment.
Further, the resin composition of the present embodiment can be imparted with arbitrary surface properties by subjecting it to plasma treatment. For details, the description of JP-A-06-182195 can be taken into consideration, and the contents thereof are incorporated in the present specification.

<Characteristics and physical characteristics of resin composition>
It is preferable that the resin composition of the present embodiment has a reduced molecular weight when it is placed under a constant temperature condition. Specifically, when stored for 28 days in an environment of 55 ° C. and 90% relative humidity, the rate of decrease in the number average molecular weight of the resin composition ((Mn of polyamide resin after storage / Mn of polyamide resin before storage) × 100) is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less. The lower limit of the reduction rate is ideally 0%, and even if it is 0.01% or more, the required performance is sufficiently satisfied.
The resin composition of the present embodiment is preferably biodegradable. The biodegradability refers to the ability to be finally decomposed into water and carbon dioxide by microorganisms and the like, and includes, for example, those in which a decrease in molecular weight is observed when stored in a compost environment for a certain period of time.
The resin composition of the present embodiment preferably has a biodegradation degree of 10% or more, more preferably 25% or more, and further preferably 30% or more after being stored in a compost environment for 90 days. It is more preferably 35% or more, and even more preferably 40% or more. Ideally, the upper limit of the degree of biodegradation is 100%, but for example, 80% or less, and even 70% or less, sufficiently satisfy the required performance. Here, the degree of biodegradation (%) is [(total CO ₂ generation amount during storage for 90 days in a compost environment) / (theoretical carbon dioxide generation amount calculated from the composition formula)] × 100.
The resin composition of the present embodiment preferably has a number average molecular weight of 8,000 or more, and more preferably 10,000 or more. The upper limit of the number average molecular weight is not particularly specified, but is, for example, 100,000 or less, and further 50,000 or less. The number average molecular weight here is that before biodegradation.

<Manufacturing method of resin composition>
Any method is adopted as the method for producing the resin composition of the present embodiment.
For example, a polyamide resin, a cobalt salt, and other components to be blended as needed are mixed using a mixing means such as a V-type blender to prepare a batch blend product, which is then melt-kneaded in an extruder with a vent. A method of pelletizing can be mentioned.

The heating temperature for melt-kneading can be appropriately selected from the range of usually 180 to 360 ° C. If the temperature is too high, decomposition gas is likely to be generated, which may cause extrusion defects such as broken strands. Therefore, it is desirable to select a screw configuration in consideration of shear heat generation and the like.

<Molded body>
The resin composition of the present embodiment is molded and used as a molded body. The molded product may be a part or a finished product.
The method for producing the molded product in the present embodiment is not particularly limited, and any molding method generally used for the resin composition can be arbitrarily adopted. For example, an injection molding method, an ultra-high speed injection molding method, an injection compression molding method, a two-color molding method, a hollow molding method such as gas assist, a molding method using a heat insulating mold, and a rapid heating mold were used. Molding method, foam molding (including supercritical fluid), insert molding, IMC (in-mold coating molding) molding method, extrusion molding method, sheet molding method, thermal molding method, rotary molding method, laminated molding method, press molding method, Blow molding method and the like can be mentioned. Further, a molding method using a hot runner method can also be used.

The molded body of the present embodiment includes transport machine parts such as automobiles, general machine parts, precision machine parts, electronic / electrical equipment parts, OA equipment parts, building materials / housing related parts, medical equipment, leisure sports equipment (for example, fishing thread). , Agricultural, forestry and fishery products, play equipment, medical products, food packaging films, daily necessities such as clothing, defense and aerospace products.
In particular, since the resin composition or molded body of the present embodiment is excellent in biodegradability, it is preferably used for food packaging films, filter cloths, and leisure sports equipment (for example, fishing lines and fishing nets, and is preferably used by fishing nets.

The resin composition of the present embodiment and the molded product of the present embodiment can be discarded by biodegrading. The resin composition and the molded product of the present embodiment can be decomposed to the molecular level by the action of microorganisms, and finally become carbon dioxide and water, which can be circulated to the natural world. Therefore, it is advantageous in that it can be disposed of naturally without being destroyed. That is, the present specification also discloses a method for disposing of a polyamide resin, which comprises biodegrading the resin composition or molded product of the present embodiment.

The resin composition of the present embodiment is stored at 55 ° C. and 90% relative humidity for 28 days, so that the number average molecular weight is reduced. The composition after the number average molecular weight is reduced (low Mn composition) contains a decomposition product of a polyamide resin and a cobalt salt, and the polyamide resin contains a constituent unit derived from a diamine and a constituent unit derived from a dicarboxylic acid. 50 mol% or more of the constituent units derived from the diamine are derived from xylylene diamine, and 50 mol% or more of the constituent units derived from the dicarboxylic acid are α, ω-linear aliphatic dicarboxylic acids having 8 to 22 carbon atoms. The composition contains a xylylene diamine-based polyamide resin derived from the above, and 0.1 mol% or more of the xylylene diamine is paraxylylene diamine. The number average molecular weight of the composition is less than 3000 (preferably less than 2000, more preferably less than 1000). ) Is the composition. The number average molecular weight of the low Mn composition is preferably 950 or less, more preferably 900 or less, further preferably 850 or less, and even more preferably 800 or less. The smaller the lower limit of the number average molecular weight, the better, but 150 or more is practical, and even 200 or more sufficiently satisfies the required performance.

Hereinafter, the present invention will be described in more detail with reference to examples. The materials, amounts used, ratios, treatment contents, treatment procedures, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.
When the measuring device or the like used in the examples is difficult to obtain due to a discontinued number or the like, measurement can be performed using another device having the same performance.

1. 1. Raw material <Example of synthesis of MP10>
After heat-dissolving sebacic acid in a reaction can under a nitrogen atmosphere, the molar ratio of metaxylylenediamine (manufactured by Mitsubishi Gas Chemical Company) and paraxylylenediamine (manufactured by Mitsubishi Gas Chemical Company) is adjusted while stirring the contents. The temperature was raised to 235 ° C. by gradually dropping the 7: 3 mixed diamine under pressure (0.35 MPa) so that the molar ratio of diamine to sebacic acid was about 1: 1. After completion of the dropping, the reaction was continued for 60 minutes to adjust the amount of components having a molecular weight of 1,000 or less. After completion of the reaction, the contents were taken out into strands and pelletized with a pelletizer to obtain a polyamide resin (MP10). The melting point of the obtained polyamide was 215 ° C.

<Synthesis example of PXD10>
In a reaction can with a jacket equipped with a stirrer, a splitter, a cooler, a thermometer, a dropping tank and a nitrogen gas introduction tube, 60.00 mol of precisely weighed sebacic acid was placed, sufficiently replaced with nitrogen, and a small amount of nitrogen flow was added. The temperature was raised to 170 ° C. below to dissolve sebacic acid and bring it into a uniform flow state. To this, 60 mol of paraxylylenediamine was added dropwise over 160 minutes with stirring. During this period, the internal pressure of the reaction system was set to normal pressure, the internal temperature was continuously raised to 285 ° C., and the water distilled with the dropping of paraxylylenediamine was removed from the system through a condenser and a cooler. After completion of the addition of paraxylylenediamine, the reaction was continued for 10 minutes while maintaining the liquid temperature of 290 ° C. Then, the internal pressure of the reaction system was continuously reduced to 600 Torr for 10 minutes, and then the reaction was continued for 20 minutes. During this time, the reaction temperature was continuously raised to 305 ° C. After completion of the reaction, a pressure of 0.3 MPa was applied to the inside of the reaction can with nitrogen gas, and the polymer was taken out as a strand from a nozzle at the bottom of the polymerization tank, cooled with water and cut into pellets to obtain pellets of a molten polymer product. The pellet was dried in a vacuum dryer at 150 ° C. for 5 hours. The melting point of the obtained polyamide resin (PXD10) measured according to DSC was 290 ° C.

<Example of MP12 synthesis>
In a reaction can with a jacket equipped with a stirrer, a splitter, a cooler, a thermometer, a dropping tank and a nitrogen gas introduction tube, 60.00 mol of the precisely weighed 1,12-dodecanedic acid was placed and sufficiently replaced with nitrogen. Further, the temperature was raised to 180 ° C. under a small amount of nitrogen stream to dissolve 1,12-dodecanedic acid to obtain a uniform flow state. To this, 60 mol of para / m-xylylenediamine in which 40 mol% of the diamine component was paraxylylenediamine and 60 mol% was metaxylylenediamine was added dropwise over 160 minutes under stirring. During this period, the internal pressure of the reaction system was set to normal pressure, the internal temperature was continuously raised to 250 ° C., and the water distilled with the dropping of para / m-xylylenediamine was removed from the system through a condenser and a cooler. .. After completion of the addition of para / m-xylylenediamine, the reaction was continued for 10 minutes while maintaining the liquid temperature of 250 ° C. Then, the internal pressure of the reaction system was continuously reduced to 600 Torr for 10 minutes, and then the reaction was continued for 20 minutes. During this time, the reaction temperature was continuously raised to 260 ° C. After completion of the reaction, a pressure of 0.3 MPa was applied to the inside of the reaction can with nitrogen gas, and the polymer was taken out as a strand from a nozzle at the bottom of the polymerization tank, cooled with water and cut into pellets to obtain pellets of a molten polymer product. The obtained pellets were placed in a tumbler (rotary vacuum chamber) having a heat medium heating cloak at room temperature. The inside of the tank was depressurized (0.5 to 10 Torr) while rotating the tumbler, the flow heat medium was heated to 150 ° C., the pellet temperature was raised to 130 ° C., and the temperature was maintained at that temperature for 3 hours. After that, nitrogen was introduced again to bring it to normal pressure, and cooling was started. When the temperature of the pellet became 70 ° C. or lower, the pellet was taken out from the tank to obtain a solid phase polymer product.
The melting point of the obtained polyamide resin (MP12) measured according to DSC was 216 ° C.

<Synthesis of 1,3-BAC6>
In a reaction can with a jacket equipped with a stirrer, a splitter, a cooler, a thermometer, a dropping tank and a nitrogen gas introduction tube, put the precisely weighed adipic acid (50.8 mol) into the reaction can, sufficiently replace it with nitrogen, and then add a small amount. The temperature was raised to 190 ° C. under a nitrogen stream to dissolve adipic acid and bring it into a uniform flow state. It takes 160 minutes with stirring 1,3-bis (aminomethyl) cyclohexane (cis-form / trans-form: 72.7 / 27.3, hereinafter 1,3-BAC) (50.5 mol). And dropped. During this period, the internal pressure of the reaction system was set to normal pressure, the internal temperature was continuously raised to 223 ° C., and the water distilled with the dropping of m-xylylenediamine was removed from the system through a condenser and a cooler. After the addition of m-xylylenediamine was completed, the reaction was continued for 10 minutes while maintaining the liquid temperature of 235 ° C. Then, the internal pressure of the reaction system was continuously reduced to 600 Torr for 10 minutes, and then the reaction was continued for 50 minutes. During this time, the reaction temperature was continuously raised to 250 ° C. After completion of the reaction, a pressure of 0.3 MPa was applied to the inside of the reaction can with nitrogen gas, and the polymer was taken out as a strand from a nozzle at the bottom of the polymerization tank, cooled with water and cut into pellets to obtain pellets of a molten polymer product. The melting point of the obtained polyamide resin (1,3-BAC6) measured according to DSC was 230 ° C. The mass ratio of the xylylenediamine structure is 0% by mass.

Cobalt stearate (StCo): manufactured by Kanto Chemical Co., Inc., product number: 07423-02

2. 2. Examples 1 to 3, Comparative Examples 1 to 4
<Compound>
Polyamide resin and cobalt stearate are weighed, blended with a tumbler, charged from the root of a twin-screw extruder (manufactured by Toshiba Machine Co., Ltd., TEM26SS), melted, and melted so as to have the composition shown in Table 1 described later. Pellets were made. The temperature of the twin-screw extruder was set to a melting point of + 20 ° C. Each component in Table 1 is shown by mass ratio. The content of cobalt stearate (StCo) is the amount of cobalt atoms (mass ppm) with respect to 100 parts by mass of the polyamide resin.

<Reduction of molecular weight after storage at 55 ° C for 28 days>
The obtained polyamide resin pellets were stored at 55 ° C. and a relative humidity of 90% for 28 days. The number average molecular weight and weight average molecular weight before and after storage were measured.
Further, "Mn (%) after 28 days" is an index showing the rate of decrease in the number average molecular weight of the polyamide resin, and is represented by (Mn of the polyamide resin after storage / Mn of the polyamide resin before storage) × 100. Is the value to be.

The number average molecular weight (Mn) was measured below according to the gel permeation chromatography (GPC) method.
GPC measurement was performed by Showa Denko's Shodex GPC SYSTEM-11. Hexafluoroisopropanol (HFIP) was used as a solvent, and 10 mg of the polyamide resin of the sample was dissolved in 10 g of HFIP and used for the measurement. The measurement conditions were as follows: measurement column using two HFIP-806M of the company's GPC standard column (column size 300 x 8.0 mm ID) and two reference columns HFIP-800, column temperature 40 ° C., solvent flow rate 1. It was set to 0 mL / min. PMMA (polymethyl methacrylate) was used as the standard sample, and the data processing software was SIC-480II manufactured by the same company to determine the number average molecular weight (Mn).

<Biodegradation>
The degree of biodegradation was measured according to JIS K 6953-1 (aerobic compost system biodegradation test method). The pellet (resin composition) was mixed with 10 g of powder after freeze-grinding and compost having a dry mass of 60 g, and the water content was 45 to 50% by mass. The mixture was placed in a composting environment at 58 ± 2 ° C. and 100% relative humidity, the air was saturated with water to aerate a gas excluding carbon dioxide, and a biodegradation test was conducted for 90 days. The amount of carbon dioxide generated was measured, and the degree of biodegradation was calculated from the total amount of theoretical carbon dioxide generated according to the following formula.
Biodegradation degree (%) = [(total CO ₂ generation amount during storage for 90 days in compost environment) / (theoretical carbon dioxide generation amount calculated from the composition formula)] × 100
The theoretical carbon dioxide generation amount calculated from the composition formula was calculated according to the following formula from the total organic carbon amount (TOC) of the test material and the sample amount of 10 g previously measured by the CHN analyzer.
Theoretical carbon dioxide generation (g) = [(total organic carbon amount (TOC) of test material / 100] × 3.67 × 10
As the compost, YK-11 manufactured by Yawata Corporation was used. A non-dispersive infrared analyzer (LI-830 manufactured by LI-COR) was used to measure the amount of carbon dioxide. A PE2400 series II manufactured by PerkinElmer was used as the CHN analyzer.

As is clear from Table 1 above, the resin compositions of the present invention (Examples 1 to 3) are stored at 55 ° C. and a relative humidity of 90% for 28 days, on which a cobalt salt acts and the number average molecular weight of the polyamide resin is increased. Was effectively reduced. Further, by storing in a compost environment for 90 days, in addition to the action of oxidative decomposition by the cobalt salt, the decomposition of the polyamide resin proceeded more effectively by biodegradation.
On the other hand, when the cobalt salt was not contained (Comparative Examples 1 to 3), no decrease in the number average molecular weight of the polyamide resin was observed even when the polyamide resin was stored at 55 ° C. and a relative humidity of 90% for 28 days. In addition, biodegradation did not progress.
On the other hand, even if a cobalt salt is blended, when the polyamide resin is not a predetermined polyamide resin (Comparative Example 4), even if the polyamide resin is stored at 55 ° C. and a relative humidity of 90% for 28 days, the number average molecular weight of the polyamide resin does not decrease. I was not able to admit. In addition, biodegradation did not progress.

Claims (13)

Contains polyamide resin and cobalt salt,
The polyamide resin contains a diamine-derived structural unit and a dicarboxylic acid-derived structural unit, and 50 mol% or more of the diamine-derived structural unit is derived from xylylene diamine and 50 mol% of the dicarboxylic acid-derived structural unit. The above contains a xylylene diamine-based polyamide resin derived from an α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms.
More than 0.1 mol% of the xylylenediamine is paraxylylenediamine.
Resin composition. The resin composition according to claim 1, wherein the mass ratio of the xylylenediamine structure in the xylylenediamine-based polyamide resin is 20 to 70% by mass; where the mass ratio of the xylylenediamine structure is [(. It is a value calculated from (mass of the xylylenediamine structure in the xylylenediamine-based polyamide resin) / (mass of the entire xylylenediamine-based polyamide resin)] × 100. The resin composition according to claim 1 or 2, wherein the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms contains sebacic acid and / or dodecanedioic acid. The resin composition according to claim 1 or 2, wherein the α, ω-linear aliphatic dicarboxylic acid having 8 to 22 carbon atoms contains a dodecanedioic acid. The resin composition according to any one of claims 1 to 4, wherein 20 mol% or more of the constituent units derived from the diamine are derived from paraxylylenediamine. The resin composition according to any one of claims 1 to 5, wherein the cobalt salt contains a carboxylic acid salt of cobalt. The resin composition according to any one of claims 1 to 5, wherein the cobalt salt contains cobalt stearate. The resin composition according to any one of claims 1 to 7, wherein the content of the cobalt salt is 10 to 2000 mass ppm with respect to 100 parts by mass of the xylylenediamine-based polyamide resin based on the cobalt atom. .. The resin composition according to any one of claims 1 to 8, which is biodegradable. The resin composition according to any one of claims 1 to 9, wherein the resin composition has a biodegradability of 10% or more after being stored in a compost environment for 90 days: Here, the degree of biodegradation ( %) Is [(CO ₂ generation amount when stored in a compost environment) / (theoretical carbon dioxide generation amount calculated from the composition formula)] × 100. A molded product formed from the resin composition according to any one of claims 1 to 10. The molded body according to claim 11, which is a fishing net. A method for disposing of a polyamide resin, which comprises biodegrading the resin composition according to any one of claims 1 to 10 or the molded product according to claim 11 or 12.