JP5406069B2 - Degradation evaluation method - Google Patents
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- 238000011156 evaluation Methods 0.000 title claims description 46
- 230000015556 catabolic process Effects 0.000 title description 9
- 238000006731 degradation reaction Methods 0.000 title description 9
- 230000006866 deterioration Effects 0.000 claims description 69
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- 239000011342 resin composition Substances 0.000 claims description 37
- 238000007654 immersion Methods 0.000 claims description 25
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- 238000005160 1H NMR spectroscopy Methods 0.000 claims description 11
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 claims description 10
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 10
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- BYEAHWXPCBROCE-UHFFFAOYSA-N 1,1,1,3,3,3-hexafluoropropan-2-ol Chemical class FC(F)(F)C(O)C(F)(F)F BYEAHWXPCBROCE-UHFFFAOYSA-N 0.000 description 3
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
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- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- XBDQKXXYIPTUBI-UHFFFAOYSA-N dimethylselenoniopropionate Natural products CCC(O)=O XBDQKXXYIPTUBI-UHFFFAOYSA-N 0.000 description 2
- 239000000295 fuel oil Substances 0.000 description 2
- 230000001771 impaired effect Effects 0.000 description 2
- HQKMJHAJHXVSDF-UHFFFAOYSA-L magnesium stearate Chemical compound [Mg+2].CCCCCCCCCCCCCCCCCC([O-])=O.CCCCCCCCCCCCCCCCCC([O-])=O HQKMJHAJHXVSDF-UHFFFAOYSA-L 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
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- 239000000126 substance Substances 0.000 description 2
- CZDYPVPMEAXLPK-UHFFFAOYSA-N tetramethylsilane Chemical compound C[Si](C)(C)C CZDYPVPMEAXLPK-UHFFFAOYSA-N 0.000 description 2
- LMRJHNFECNKDKH-UHFFFAOYSA-N 4-(trifluoromethyl)nicotinic acid Chemical compound OC(=O)C1=CN=CC=C1C(F)(F)F LMRJHNFECNKDKH-UHFFFAOYSA-N 0.000 description 1
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- 229910001860 alkaline earth metal hydroxide Inorganic materials 0.000 description 1
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- 238000010101 extrusion blow moulding Methods 0.000 description 1
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- 229920000578 graft copolymer Polymers 0.000 description 1
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- 229920001903 high density polyethylene Polymers 0.000 description 1
- 239000004700 high-density polyethylene Substances 0.000 description 1
- 238000001746 injection moulding Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 235000019359 magnesium stearate Nutrition 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 229920003229 poly(methyl methacrylate) Polymers 0.000 description 1
- 229920001515 polyalkylene glycol Polymers 0.000 description 1
- 229920001707 polybutylene terephthalate Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
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- 229920000069 polyphenylene sulfide Polymers 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 235000019260 propionic acid Nutrition 0.000 description 1
- IUVKMZGDUIUOCP-BTNSXGMBSA-N quinbolone Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H]([C@]4(C=CC(=O)C=C4CC3)C)CC[C@@]21C)C1=CCCC1 IUVKMZGDUIUOCP-BTNSXGMBSA-N 0.000 description 1
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- 238000001542 size-exclusion chromatography Methods 0.000 description 1
- UYCAUPASBSROMS-AWQJXPNKSA-M sodium;2,2,2-trifluoroacetate Chemical compound [Na+].[O-][13C](=O)[13C](F)(F)F UYCAUPASBSROMS-AWQJXPNKSA-M 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 229920001897 terpolymer Polymers 0.000 description 1
- 238000009757 thermoplastic moulding Methods 0.000 description 1
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- 239000013585 weight reducing agent Substances 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/44—Resins; Plastics; Rubber; Leather
- G01N33/442—Resins; Plastics
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
- G01N1/30—Staining; Impregnating ; Fixation; Dehydration; Multistep processes for preparing samples of tissue, cell or nucleic acid material and the like for analysis
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N24/00—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects
- G01N24/08—Investigating or analyzing materials by the use of nuclear magnetic resonance, electron paramagnetic resonance or other spin effects by using nuclear magnetic resonance
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- Life Sciences & Earth Sciences (AREA)
- Health & Medical Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Pathology (AREA)
- Immunology (AREA)
- General Physics & Mathematics (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- Engineering & Computer Science (AREA)
- High Energy & Nuclear Physics (AREA)
- Food Science & Technology (AREA)
- Medicinal Chemistry (AREA)
- Biomedical Technology (AREA)
- Molecular Biology (AREA)
- Testing Resistance To Weather, Investigating Materials By Mechanical Methods (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Polyoxymethylene Polymers And Polymers With Carbon-To-Carbon Bonds (AREA)
Description
本発明は、炭化水素系液体に浸漬した際のポリアセタール共重合体を含む樹脂成形品の劣化を評価する方法に関する。 The present invention relates to a method for evaluating deterioration of a resin molded article containing a polyacetal copolymer when immersed in a hydrocarbon-based liquid.
世界の自動車市場は、持続的な軽量化及び一体化の推進によって自動車関連部品に適用される素材を金属からプラスチックへと代替している趨勢にあり、適用プラスチックに対して要求される物性もまた漸次厳しくなりつつある。上記のような用途に用いられるプラスチックとしては、例えば、ポリアセタール樹脂、ポリアミド６樹脂、ポリアミド１２樹脂、ポリブチレンテレフタレート樹脂、ポリフェニレンスルフィド樹脂、高密度ポリエチレン等が挙げられる。 The global automobile market is in the trend of replacing materials applied to automobile-related parts from metals to plastics by continuously promoting weight reduction and integration, and the physical properties required for applied plastics are also It is getting stricter. Examples of the plastic used for the above-mentioned applications include polyacetal resin, polyamide 6 resin, polyamide 12 resin, polybutylene terephthalate resin, polyphenylene sulfide resin, and high density polyethylene.
これらの中でもポリアセタール系樹脂、特にポリアセタール共重合体を含む樹脂組成物は剛性、強度、靭性、耐クリープ寿命、耐疲労性、耐薬品性及び摺動性、耐熱性等のバランスに優れ、且つその加工が容易であることから、エンジニアリングプラスチックスとして、電気機器や電気機器の機構部品、自動車部品及びその他の機構部品を中心に広範囲にわたって用いられている。 Among these, a polyacetal resin, particularly a resin composition containing a polyacetal copolymer, has an excellent balance of rigidity, strength, toughness, creep resistance, fatigue resistance, chemical resistance, slidability, heat resistance, and the like. Since it is easy to process, it is widely used as engineering plastics mainly in electrical equipment, mechanical parts of electrical equipment, automobile parts, and other mechanical parts.
また、ポリアセタール共重合体を含む樹脂組成物は、特に耐燃料油性が高いので、燃料搬送ユニット等の炭化水素系液体に直接接触するような自動車関連部材に好ましく使用されている。使用例としては、ポリオキシメチレンホモポリマー又はポリオキシメチレンコポリマーと、ポリアルキレングリコールと、酸化亜鉛と、を特定の配合で含有する熱可塑性成形組成物が挙げられる（特許文献１）。 In addition, since the resin composition containing the polyacetal copolymer has particularly high fuel oil resistance, it is preferably used for automobile-related members that come into direct contact with hydrocarbon-based liquids such as fuel transfer units. Examples of use include thermoplastic molding compositions containing polyoxymethylene homopolymer or polyoxymethylene copolymer, polyalkylene glycol, and zinc oxide in a specific formulation (Patent Document 1).
また、炭化水素系液体、中でも燃料と直接接触する部品に適用される材料は、機械的物性及び耐燃料耐久性が充足される材料であることが要求され、このような要求を満たすとされている材料として、ポリアセタール系の重合体と、マグネシウムステアレートと、酸化防止剤と、を特定の配合で含有する材料が開発されている（特許文献２）。 In addition, materials applied to hydrocarbon-based liquids, especially parts that are in direct contact with fuel, are required to satisfy the requirements for mechanical properties and fuel durability. As a material, a material containing a polyacetal polymer, magnesium stearate, and an antioxidant in a specific composition has been developed (Patent Document 2).
しかしながら、特許文献１、特許文献２に記載されるような、燃料に直接接触する自動車関連部材に用いるポリアセタール系の重合体を用いて作製した部品は、時として部品表面にクラックが入る等劣化が見られることがある。ところが、上記のような劣化が起こる原因は様々であり、どのような原因でポリアセタール重合体を含む樹脂材料が劣化を起こしやすいものであるかについて評価を行うことができない。特に外観変化や物性変化を基準にすると、劣化が進行しないと判断出来ないため、評価に時間がかかるという理由から劣化初期のわずかな劣化を判別する必要がある。さらに、通常、炭化水素系液体は複雑な組成になっており、このような複雑な組成の炭化水素系液体を用いる場合には、何が原因で劣化したのかは分からず、樹脂材料の劣化評価はさらに困難になる。 However, as described in Patent Document 1 and Patent Document 2, parts manufactured using a polyacetal polymer used for automobile-related members that are in direct contact with fuel sometimes deteriorate such as cracks on the surface of the parts. It may be seen. However, there are various causes for the deterioration as described above, and it is impossible to evaluate what causes the resin material containing the polyacetal polymer to easily deteriorate. In particular, based on changes in appearance and physical properties, it cannot be determined that the deterioration does not proceed. Therefore, it is necessary to determine a slight deterioration at the initial stage of deterioration because the evaluation takes time. In addition, hydrocarbon liquids usually have a complicated composition. When hydrocarbon liquids with such a complex composition are used, it is not known what caused the deterioration, and the deterioration of the resin material is evaluated. Becomes even more difficult.
そこで、最適な樹脂材料の選択、最適な燃料の選択のために、劣化の原因を分析する方法が求められている。特に劣化の分析の際には劣化初期のわずかな劣化を判別することが求められている。 Therefore, a method for analyzing the cause of deterioration is required in order to select an optimal resin material and an optimal fuel. In particular, when analyzing deterioration, it is required to discriminate slight deterioration at the initial stage of deterioration.
本発明は上記のような課題を解決するためになされたものであり、その目的は、ポリアセタール共重合体を含む樹脂組成物を成形してなる樹脂成形品が、炭化水素系液体に浸漬されることよって劣化する原因を分析し、劣化初期のわずかな劣化も評価可能な樹脂成形品の劣化評価する方法を提供することにある。 The present invention has been made in order to solve the above-described problems, and an object of the present invention is to immerse a resin molded product obtained by molding a resin composition containing a polyacetal copolymer in a hydrocarbon-based liquid. It is an object of the present invention to provide a method for evaluating the deterioration of a resin molded product by analyzing the cause of the deterioration and evaluating the slight deterioration at the initial stage of deterioration.
本発明者らは、上記課題を解決するために鋭意研究を重ねた。その結果、上記のようなポリアセタール共重合体を含む樹脂組成物を成形してなる樹脂成形品の炭化水素系液体中での劣化には、炭化水素系液体に起因するラジカル劣化が大きく影響することを見出し、さらに、炭化水素系液体に起因する上記樹脂成形品の劣化の程度は、炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定した時に、テトラメチルシランを基準とした場合のピーク位置が８．０５ｐｐｍ近傍をピークトップとする−ＣＨ２ＣＨ２ＯＣＨＯ末端基のアルデヒドの水素原子に由来するピークの面積から上記ポリアセタール共重合体の分子量の変化を評価することによって評価できることを見出し、本発明を完成するに至った。より具体的には本発明は以下のものを提供する。 The inventors of the present invention have made extensive studies to solve the above problems. As a result, the radical degradation caused by the hydrocarbon liquid greatly affects the deterioration of the resin molded product formed by molding the resin composition containing the polyacetal copolymer as described above in the hydrocarbon liquid. Further, the degree of deterioration of the resin molded product caused by the hydrocarbon-based liquid is 1 for each of the resin compositions containing a plurality of polyacetal copolymers having different immersion times when immersed in the hydrocarbon-based liquid. From the area of the peak derived from the hydrogen atom of the aldehyde of the —CH 2 CH 2 OCHO terminal group having a peak top of about 8.05 ppm when the tetramethylsilane is used as a reference when the H-NMR measurement is performed, the polyacetal The inventors have found that it can be evaluated by evaluating the change in the molecular weight of the copolymer, and have completed the present invention. More specifically, the present invention provides the following.
（１） 炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定した時に、それぞれの測定結果の８．０４ｐｐｍから８．０７ｐｐｍにピークトップを有するピークの合計面積から前記ポリアセタール共重合体の分子量の変化を評価することによって、前記樹脂組成物の劣化を評価する劣化評価方法。 (1) When 1 H-NMR measurement is performed on each of the resin compositions containing a plurality of polyacetal copolymers having different immersion times when immersed in a hydrocarbon-based liquid, each measurement result is 8.04 ppm to 8.07 ppm. The deterioration evaluation method which evaluates deterioration of the said resin composition by evaluating the change of the molecular weight of the said polyacetal copolymer from the total area of the peak which has a peak top.
（２） 炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定した時に、前記ポリアセタール共重合体に含まれる８．０５ｐｐｍ近傍をピークトップとする−ＣＨ２ＣＨ２ＯＣＨＯ末端基のアルデヒドの水素原子に由来するピークの面積から前記ポリアセタール共重合体の分子量の変化を評価することによって、前記樹脂組成物の劣化を評価する劣化評価方法。 (2) When each of the resin compositions containing a plurality of polyacetal copolymers having different immersion times when immersed in a hydrocarbon-based liquid is measured by 1 H-NMR, the vicinity of 8.05 ppm contained in the polyacetal copolymer Degradation for evaluating the degradation of the resin composition by evaluating the change in the molecular weight of the polyacetal copolymer from the area of the peak derived from the hydrogen atom of the aldehyde of the -CH 2 CH 2 OCHO terminal group Evaluation method.
（３） 前記炭化水素系液体が燃料である（１）又は（２）に記載の劣化評価方法。 (3) The deterioration evaluation method according to (1) or (2), wherein the hydrocarbon-based liquid is a fuel.
（４） 前記樹脂組成物が、樹脂成形品の表面から３００μｍ以内の領域から採取した樹脂組成物である（１）から（３）のいずれかに記載の劣化評価方法。 (4) The deterioration evaluation method according to any one of (1) to (3), wherein the resin composition is a resin composition collected from a region within 300 μm from the surface of the resin molded product.
（５） 前記浸漬時間は、５０００時間以内である（１）から（４）のいずれかに記載の劣化評価方法。 (5) The deterioration evaluation method according to any one of (1) to (4), wherein the immersion time is within 5000 hours.
（６） 前記炭化水素系液体が軽油である（１）から（５）のいずれかに記載の劣化評価方法。 (6) The deterioration evaluation method according to any one of (1) to (5), wherein the hydrocarbon-based liquid is light oil.
（７） 前記樹脂組成物が自動車の燃料系部品から採取される樹脂組成物である（１）から（６）のいずれかに記載の劣化評価方法。 (7) The deterioration evaluation method according to any one of (1) to (6), wherein the resin composition is a resin composition collected from a fuel system part of an automobile.
本発明によれば、炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定した時に、それぞれの測定結果の８．０４ｐｐｍから８．０７ｐｐｍにピークトップを有するピークの合計面積から上記ポリアセタール共重合体の分子量の変化を評価することで、炭化水素系液体に直接接触するポリアセタール共重合体を含む樹脂成形品に起こる劣化を評価することができる。特に本発明の評価方法によれば、劣化初期のわずかな劣化も判別することができる。 According to the present invention, when each of the resin compositions containing a plurality of polyacetal copolymers having different immersion times when immersed in a hydrocarbon-based liquid is subjected to 1 H-NMR measurement, from each measurement result of 8.04 ppm. By evaluating the change in the molecular weight of the polyacetal copolymer from the total area of the peak having a peak top at 8.07 ppm, the degradation that occurs in the resin molded product containing the polyacetal copolymer in direct contact with the hydrocarbon-based liquid is evaluated. can do. In particular, according to the evaluation method of the present invention, a slight deterioration at the initial stage of deterioration can be determined.
本発明によれば、炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定した時に、上記ポリアセタール共重合体に含まれる８．０５ｐｐｍ近傍をピークトップとする−ＣＨ２ＣＨ２ＯＣＨＯ末端基のＣＨＯの水素原子に由来するピークの面積から上記ポリアセタール共重合体の分子量の変化を評価することで、炭化水素系液体に直接接触するポリアセタール共重合体を含む樹脂成形品に起こる劣化を評価することができる。 According to the present invention, when each of a resin composition containing a plurality of polyacetal copolymers having different immersion times when immersed in a hydrocarbon-based liquid is subjected to 1 H-NMR measurement, it is included in the polyacetal copolymer. Direct contact with hydrocarbon-based liquid by evaluating the change in molecular weight of the polyacetal copolymer from the area of the peak derived from the hydrogen atom of CHO in the —CH 2 CH 2 OCHO end group having a peak top near 0.05 ppm It is possible to evaluate deterioration that occurs in a resin molded product containing a polyacetal copolymer.
また、炭化水素系液体に浸漬前後でのポリアセタール共重合体の−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量の変化量を評価することで、問題となる劣化が炭化水素系液体による劣化により起こるものかを判断することができる。その結果、本発明の劣化評価方法を用いることで、原因別に対策を立てることができ、問題を解決しやすくなる。 In addition, by evaluating the amount of change in the content of the —CH 2 CH 2 OCHO end group of the polyacetal copolymer before and after being immersed in the hydrocarbon-based liquid, the problem deterioration may be caused by the deterioration due to the hydrocarbon-based liquid. Can be determined. As a result, by using the deterioration evaluation method of the present invention, it is possible to take measures for each cause and to easily solve the problem.
また、候補となる炭化水素系液体の中から、炭化水素系液体によるポリアセタール共重合体の劣化が少ない炭化水素系液体を容易に選択することができる。同様に使用する候補となるポリアセタール共重合体がいくつかある場合には容易に耐劣化性の高い材料を決めることができる。 In addition, a hydrocarbon liquid with little deterioration of the polyacetal copolymer due to the hydrocarbon liquid can be easily selected from the candidate hydrocarbon liquids. Similarly, when there are several polyacetal copolymers that are candidates for use, a material having high deterioration resistance can be easily determined.
以下、本発明の一実施形態について詳細に説明するが、本発明は、以下の実施形態に何ら限定されるものではなく、本発明の目的の範囲内において、適宜変更を加えて実施することができる。 Hereinafter, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the following embodiment, and may be implemented with appropriate modifications within the scope of the object of the present invention. it can.
本発明の劣化評価方法は、炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定することを特徴としており、それぞれの測定結果の８．０４ｐｐｍから８．０７ｐｐｍにピークトップを有するピークの合計面積又はポリアセタール共重合体に含まれる８．０５ｐｐｍ近傍をピークトップとする−ＣＨ２ＣＨ２ＯＣＨＯ末端基のアルデヒドの水素原子に由来するピークの面積からポリアセタール共重合体の分子量の変化を評価するものであればその他の工程は、特に限定されない。これらのピークの面積の変化から樹脂成形品の劣化を評価することができるからである。 The degradation evaluation method of the present invention is characterized in that 1 H-NMR measurement is performed for each of a resin composition containing a plurality of polyacetal copolymers having different immersion times when immersed in a hydrocarbon-based liquid. Resulting from the total area of peaks having a peak top from 8.04 ppm to 8.07 ppm or the hydrogen atom of the aldehyde of the —CH 2 CH 2 OCHO end group having a peak top in the vicinity of 8.05 ppm contained in the polyacetal copolymer The other steps are not particularly limited as long as the change in the molecular weight of the polyacetal copolymer is evaluated from the area of the peak. This is because the deterioration of the resin molded product can be evaluated from the change in the area of these peaks.
本発明の劣化評価方法としては、例えば、評価準備工程、定量工程、分子量評価工程を備える劣化評価方法が挙げられる。以下、これらの工程を備える劣化評価方法を例に本発明について説明する。 Examples of the deterioration evaluation method of the present invention include a deterioration evaluation method including an evaluation preparation step, a quantitative step, and a molecular weight evaluation step. Hereinafter, the present invention will be described by taking a deterioration evaluation method including these steps as an example.
＜評価準備工程＞
評価準備工程は、評価対象となる樹脂成形品を用意する。炭化水素系液体に浸漬した際の浸漬時間が異なる複数のポリアセタール共重合体を含む樹脂組成物のそれぞれを１Ｈ−ＮＭＲ測定するために樹脂成形品を準備する。なお、樹脂組成物は樹脂成形品から採取する１Ｈ−ＮＭＲ測定用のサンプルである。
<Evaluation preparation process>
In the evaluation preparation step, a resin molded product to be evaluated is prepared. A resin molded article is prepared for 1 H-NMR measurement of each of a resin composition containing a plurality of polyacetal copolymers having different immersion times when immersed in a hydrocarbon-based liquid. The resin composition is a sample for 1 H-NMR measurement collected from a resin molded product.
樹脂成形品は、ポリアセタール共重合体を含む樹脂成形品であれば特に限定されない。ポリアセタール共重合体とは、オキシメチレン基（−ＣＨ２Ｏ−）を主たる構成単位として含む高分子化合物である。ポリアセタール共重合体としては、例えば、オキシメチレンユニットとオキシエチレンユニットとを構成単位として含むポリアセタール共重合体が挙げられる。ポリアセタール共重合体は、オキシメチレン基以外に、コモノマー単位として、炭素数２〜６程度、好ましくは炭素数２〜４程度のオキシアルキレン単位（例えば、オキシエチレン基（−ＣＨ２ＣＨ２Ｏ−）、オキシプロピレン基、オキシテトラメチレン基等）、さらに好ましくはオキシエチレン基を構成単位として含んでいる。炭素数２〜６程度のオキシアルキレン基の割合（コモノマー単位の含有量）は、ポリアセタール樹脂の用途等に応じて適当に選択できる。 The resin molded product is not particularly limited as long as it is a resin molded product containing a polyacetal copolymer. The polyacetal copolymer is a polymer compound containing an oxymethylene group (—CH 2 O—) as a main structural unit. As a polyacetal copolymer, the polyacetal copolymer which contains an oxymethylene unit and an oxyethylene unit as a structural unit is mentioned, for example. In addition to the oxymethylene group, the polyacetal copolymer has, as a comonomer unit, an oxyalkylene unit having about 2 to 6 carbon atoms, preferably about 2 to 4 carbon atoms (for example, an oxyethylene group (—CH 2 CH 2 O—)). Oxypropylene group, oxytetramethylene group, etc.), more preferably oxyethylene group as a structural unit. The proportion of the oxyalkylene group having about 2 to 6 carbon atoms (comonomer unit content) can be appropriately selected depending on the use of the polyacetal resin.
ポリアセタール共重合体は、二成分で構成されたコポリマー、三成分で構成されたターポリマー等の複数の成分で構成されていてもよい。ポリアセタール共重合体は、一般にランダムコポリマーであるが、ブロックコポリマー、グラフトコポリマー等であってもよい。また、ポリアセタール共重合体は、線状のみならず分岐構造であってもよく、架橋構造を有していてもよい。さらに、ポリアセタール共重合体の末端は、例えば、酢酸、プロピオン酸、酪酸等のカルボン酸とのエステル化等により安定化されていてもよい。ポリアセタール共重合体の重合度、分岐度や架橋度も特に制限はなく、溶融成形可能であればよい。 The polyacetal copolymer may be composed of a plurality of components such as a copolymer composed of two components and a terpolymer composed of three components. The polyacetal copolymer is generally a random copolymer, but may be a block copolymer, a graft copolymer, or the like. In addition, the polyacetal copolymer may have a branched structure as well as a linear structure, and may have a crosslinked structure. Furthermore, the terminal of the polyacetal copolymer may be stabilized, for example, by esterification with a carboxylic acid such as acetic acid, propionic acid or butyric acid. The degree of polymerization, the degree of branching and the degree of crosslinking of the polyacetal copolymer are not particularly limited as long as it can be melt-molded.
上記ポリアセタール共重合体は、本発明の目的を害さない範囲で、上記以外の繰り返し単位を含むものであってもよい。また、上記ポリアセタール共重合体には本発明の目的を害さない範囲で、他の樹脂を含んでいてもよい。 The polyacetal copolymer may contain a repeating unit other than those described above as long as the object of the present invention is not impaired. The polyacetal copolymer may contain other resins as long as the object of the present invention is not impaired.
本発明の劣化評価方法は、様々なポリアセタール共重合体に対して適用することが可能であるが、特に、オキシメチレン単位とオキシエチレン単位とで構成されたポリアセタール共重合体を含む樹脂組成物からなる樹脂成形品に対して適用することが好ましく、上記ポリアセタール共重合体からなる樹脂成形品に対して適用することがさらに好ましい。 The degradation evaluation method of the present invention can be applied to various polyacetal copolymers, and in particular, from a resin composition containing a polyacetal copolymer composed of oxymethylene units and oxyethylene units. It is preferably applied to a resin molded product, and more preferably applied to a resin molded product made of the polyacetal copolymer.
実際に劣化評価の対象となる樹脂組成物は、例えば上記のようなポリアセタール共重合体を含む樹脂成形品から採取する樹脂組成物である。成形方法は特に限定されないが、圧縮成形、トランスファー成形、射出成形、押出成形、ブロー成形等種々の成形方法を挙げることができる。 The resin composition that is actually subject to degradation evaluation is, for example, a resin composition collected from a resin molded product containing the polyacetal copolymer as described above. The molding method is not particularly limited, and examples thereof include various molding methods such as compression molding, transfer molding, injection molding, extrusion molding, and blow molding.
評価の対象となる樹脂成形品は後述する炭化水素系液体に直接又は間接的に接触するものであれば特に限定されず、様々な場面で用いられる樹脂成形品が挙げられる。本発明の劣化評価方法は、上記のようなポリアセタール共重合体を含む自動車部品に対して好ましく適用することができる。自動車部品は炭化水素系液体に接触することが多いからである。なお、「樹脂成形品が間接的に炭化水素系液体に接触する」とは、気化した炭化水素系液体と接触するような樹脂成形品も含まれることを指す。 The resin molded product to be evaluated is not particularly limited as long as it is in direct or indirect contact with the hydrocarbon-based liquid described later, and includes resin molded products used in various situations. The deterioration evaluation method of the present invention can be preferably applied to automobile parts including the polyacetal copolymer as described above. This is because automobile parts often come into contact with hydrocarbon-based liquids. Note that “the resin molded product indirectly contacts the hydrocarbon-based liquid” means that a resin molded product that contacts the vaporized hydrocarbon-based liquid is also included.
評価する対象となる樹脂成形品を炭化水素系液体に浸漬する。炭化水素系液体とは、例えば内燃機関の燃料、潤滑剤等である。炭化水素系液体には複数の炭化水素系液体を混合したものや、炭化水素系液体に安定剤等の添加剤を配合したものも含まれる。内燃機関の燃料に直接接触するような樹脂成形品の評価に本発明の劣化評価方法は好ましく適用することができる。内燃機関の燃料としては、例えば、メタノール、ガソリン、軽油、重油、グリス等が挙げられる。これらの内燃機関の燃料の中でも、特に軽油に直接接触するような樹脂成形品の評価に本発明の劣化評価方法は好ましく適用することができる。 The resin molded product to be evaluated is immersed in a hydrocarbon-based liquid. The hydrocarbon-based liquid is, for example, an internal combustion engine fuel, a lubricant, or the like. The hydrocarbon-based liquid includes a mixture of a plurality of hydrocarbon-based liquids and a mixture of hydrocarbon-based liquids with additives such as stabilizers. The deterioration evaluation method of the present invention can be preferably applied to the evaluation of a resin molded product that comes into direct contact with the fuel of an internal combustion engine. Examples of the fuel for the internal combustion engine include methanol, gasoline, light oil, heavy oil, and grease. Among these internal combustion engine fuels, the deterioration evaluation method of the present invention can be preferably applied to evaluation of resin molded articles that are in direct contact with light oil.
本発明の評価方法において、炭化水素系液体に樹脂成形品を浸漬させる時間は特に限定されないが、浸漬時間が長くなり過ぎると、副反応等が起こり、樹脂成形品の劣化評価が難しくなる。また、浸漬時間には浸漬時間がゼロ、即ち全く浸漬させない場合も含む。評価を行いやすい浸漬時間は使用する炭化水素系液体の種類、ポリアセタール共重合体の種類等によっても異なる場合があるものの、５０００時間以内であることが好ましい。短い時間で炭化水素系液体に浸漬を行うことにより、時間をかけることなく樹脂成形品の劣化評価を行うことができる。短い時間であれば、さらなる反応等の影響が少なく、炭化水素系液体への浸漬前後での樹脂成形品に含まれるポリアセタール共重合体の−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量の炭化水素系液体劣化による変化をより正確に測定でき、その結果、劣化するか否かの評価を正確に行える。 In the evaluation method of the present invention, the time for immersing the resin molded product in the hydrocarbon-based liquid is not particularly limited. However, if the immersion time is too long, side reactions and the like occur, making it difficult to evaluate the deterioration of the resin molded product. In addition, the immersion time includes a case where the immersion time is zero, that is, no immersion is performed. Although the immersion time that allows easy evaluation may vary depending on the type of hydrocarbon-based liquid used, the type of polyacetal copolymer, and the like, it is preferably within 5000 hours. By immersing in a hydrocarbon-based liquid in a short time, it is possible to evaluate the deterioration of the resin molded product without taking time. If it is a short time, there is little influence of the further reaction etc., and the hydrocarbon type of the content of -CH 2 CH 2 OCHO end group of the polyacetal copolymer contained in the resin molded product before and after being immersed in the hydrocarbon type liquid Changes due to liquid deterioration can be measured more accurately, and as a result, it can be accurately evaluated whether or not it deteriorates.
例えば、炭化水素系液体に浸漬後の樹脂成形品及び浸漬させなかった樹脂成形品から、評価を行うためのサンプルを採る。評価を行うためのサンプルを上記樹脂成形品中のどの部分から採るかは、特に限定されないが、本発明の評価の対象となる劣化は、炭化水素系液体が接触する樹脂成形品の表面で主に起こるため、表面から３００μｍ以内の領域のサンプルを採ることが好ましい。より好ましくは表面から２００μｍ以内の領域である。 For example, a sample for evaluation is taken from a resin molded article immersed in a hydrocarbon-based liquid and a resin molded article not immersed. The part from which the sample for evaluation is taken in the above-mentioned resin molded product is not particularly limited, but the deterioration that is the object of the evaluation of the present invention is mainly caused by the surface of the resin molded product in contact with the hydrocarbon-based liquid. Therefore, it is preferable to take a sample in an area within 300 μm from the surface. More preferably, it is an area within 200 μm from the surface.
＜定量工程＞
定量工程は、上記樹脂組成物サンプルに含まれるポリアセタール共重合体の−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量の定量を行う工程である。上記末端基の含有量の定量は、１Ｈ−ＮＭＲスペクトルの測定により行う。
<Quantitative process>
The quantification step is a step of quantifying the content of —CH 2 CH 2 OCHO end groups of the polyacetal copolymer contained in the resin composition sample. The content of the terminal group is quantified by measuring a 1 H-NMR spectrum.
１Ｈ−ＮＭＲスペクトルの測定は、好ましくは２００ＭＨｚ以上の分解能を有する装置を使用して、室温で、必要に応じて精度を上げるために積算して行われる。図１には、−ＣＨ２ＯＣＨＯ末端基に由来するピーク、−ＣＨ２ＣＨ２ＯＣＨＯ末端基に由来するピークを示す。以下、横軸はＴＭＳ基準の化学シフトである。図１から分かるように、−ＣＨ２ＯＣＨＯ末端基に由来するピークのピークトップと、−ＣＨ２ＣＨ２ＯＣＨＯ末端基に由来するピークのピークトップとは非常に近い。これらのピークを区別し、−ＣＨ２ＣＨ２ＯＣＨＯ末端基のアルデヒドの水素原子に由来するピークの面積から−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量を定量することで炭化水素系液体による劣化評価を正確に行うことができる。なお、図１を得た測定条件では、−ＣＨ ２ ＣＨ ２ ＯＣＨＯ末端基に由来するピークのピークトップは、８．０５１ｐｐｍ付近に現れ、−ＣＨ ２ ＯＣＨＯ末端基に由来するピークのピークトップは、８．０６４ｐｐｍ付近に現れている。 The measurement of 1 H-NMR spectrum is preferably performed by using an apparatus having a resolution of 200 MHz or higher at room temperature in order to increase the accuracy as necessary. FIG. 1 shows peaks derived from —CH 2 OCHO end groups and peaks derived from —CH 2 CH 2 OCHO end groups. Hereinafter, the horizontal axis represents the TMS standard chemical shift. As can be seen from FIG. 1, the peak top of the peak derived from the —CH 2 OCHO end group is very close to the peak top of the peak derived from the —CH 2 CH 2 OCHO end group. To distinguish these peaks, the deterioration evaluation by hydrocarbon liquids by quantifying the amount of -CH 2 CH 2 OCHO end groups from the area of a peak derived from a hydrogen atom of an aldehyde of -CH 2 CH 2 OCHO end groups Can be done accurately. In the measurement conditions obtained in FIG. 1, the peak top of the peak derived from —CH 2 CH 2 OCHO end group appears in the vicinity of 8.051 ppm, and the peak top of the peak derived from —CH 2 OCHO end group is It appears in the vicinity of 8.064 ppm.
上記のようにして同定された末端基の定量は、−ＣＨ２ＯＣＨＯ末端基のアルデヒドの水素原子のピーク面積と、−ＣＨ２ＣＨ２ＯＣＨＯ末端基のアルデヒドの水素原子のピーク面積とから求められる。上記定量方法において、ピーク面積の代りに、必要であれば適当な補正を行って、ピークの高さを使用することができる。 The quantification of the end group identified as described above is obtained from the peak area of the hydrogen atom of the aldehyde of the —CH 2 OCHO end group and the peak area of the hydrogen atom of the aldehyde of the —CH 2 CH 2 OCHO end group. . In the above quantification method, instead of the peak area, the peak height can be used with appropriate correction if necessary.
本発明の樹脂成形品の劣化評価方法であれば、上記のように炭化水素系液体への浸漬時間が異なる樹脂成形品に含まれるポリアセタール共重合体に含まれる−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量を定量することで、ポリアセタール共重合体を含む樹脂成形品の劣化を評価することができる。この評価結果を用いることで、原因に応じた対策を立てることができるため、ポリアセタール樹脂を含む樹脂成形品の劣化を容易に解決することができる。また、最適なポリアセタール系樹脂の選択も容易になる。 If it is the degradation evaluation method of the resin molded product of the present invention, as described above, the -CH 2 CH 2 OCHO end group contained in the polyacetal copolymer contained in the resin molded product with different immersion times in hydrocarbon-based liquids. By quantifying the content, it is possible to evaluate the deterioration of the resin molded product containing the polyacetal copolymer. By using this evaluation result, it is possible to take measures according to the cause, so that it is possible to easily solve the deterioration of the resin molded product containing the polyacetal resin. In addition, it is easy to select an optimal polyacetal resin.
評価対象等により異なるものの、炭化水素系液体への浸漬時間が１０００時間以内であり、上記のような方法で定量される−ＣＨ２ＣＨ２ＯＣＨＯ末端基の増加量が少ないほど、劣化の少ない材料であると評価することができる。燃料への浸漬時間が１０００時間以内であれば、末端基の他の反応による変化がほとんど進んでいないと考えられるため、樹脂組成物の炭化水素系液体による劣化を末端基の含有量から適切に評価することができるからである。なお、上記の通り劣化は、炭化水素系液体と接触する樹脂組成物の表面から起こるため、樹脂成形品表面での末端基の増加量が上記範囲であることが好ましい。 Although it varies depending on the evaluation object, the immersion time in the hydrocarbon-based liquid is 1000 hours or less, and the smaller the amount of —CH 2 CH 2 OCHO end groups quantified by the method as described above, the less the material is deteriorated. Can be evaluated. If the immersion time in the fuel is 1000 hours or less, it is considered that the change due to other reactions of the terminal group is hardly progressed. Therefore, the deterioration of the resin composition due to the hydrocarbon-based liquid is appropriately determined from the content of the terminal group. This is because it can be evaluated. As described above, the deterioration occurs from the surface of the resin composition that comes into contact with the hydrocarbon-based liquid. Therefore, it is preferable that the increase amount of the terminal group on the surface of the resin molded product is in the above range.
また、ポリアセタール共重合体を含む樹脂組成物は、炭化水素系液体による劣化以外に酸により劣化する。酸劣化が原因の樹脂組成物の劣化の場合には、抗酸剤を添加することにより解消することができる。抗酸剤としては従来公知のものを使用することができる。従来公知の抗酸剤としては、例えば、窒素含有化合物、アルカリあるいはアルカリ土類金属の水酸化物、無機塩、カルボン酸塩等を挙げることができる。抗酸剤は、いずれか１種のみを添加してもよいし、２種以上を添加してもよい。 Moreover, the resin composition containing a polyacetal copolymer is deteriorated by an acid in addition to deterioration by a hydrocarbon-based liquid. In the case of deterioration of the resin composition due to acid deterioration, it can be solved by adding an anti-acid agent. A conventionally well-known thing can be used as an anti-acid agent. Examples of conventionally known anti-acid agents include nitrogen-containing compounds, alkali or alkaline earth metal hydroxides, inorganic salts, carboxylates, and the like. Any one of the antiacid agents may be added, or two or more may be added.
したがって、炭化水素系液体の浸漬後で−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量が増加する劣化の方が、解決が難しい材料であることを評価することができる。特に１０００時間の炭化水素系液体浸漬後の樹脂成形品中の−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量の増加量が少ないほど、炭化水素系液体による劣化が小さく通常の自動車部品に対して好ましく使用可能と判断できる。 Therefore, it can be evaluated that the deterioration in which the content of the —CH 2 CH 2 OCHO end group increases after the immersion of the hydrocarbon-based liquid is a more difficult material to solve. In particular, the smaller the increase in the content of —CH 2 CH 2 OCHO end groups in the resin molded product after immersion for 1000 hours in the hydrocarbon-based liquid, the smaller the deterioration due to the hydrocarbon-based liquid, and the more preferable for normal automobile parts. It can be judged that it can be used.
＜分子量評価工程＞
本発明の劣化評価方法においては、例えば、炭化水素系液体への浸漬前後での樹脂組成物に含まれる−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量の変化量を１Ｈ−ＮＭＲ測定で定量することによって、炭化水素系液体浸漬前後での分子量の変化を評価し、樹脂組成物の劣化を評価する。上記末端基の含有量の変化と分子量の変化との関係を導出しておくことでより正確に劣化評価を行うことができる。分子量がどの程度減少するかを具体的に評価できるからである。
<Molecular weight evaluation process>
In the deterioration evaluation method of the present invention, for example, the amount of change in the content of —CH 2 CH 2 OCHO end groups contained in the resin composition before and after immersion in a hydrocarbon-based liquid is quantified by 1 H-NMR measurement. Thus, the change in molecular weight before and after immersion in the hydrocarbon-based liquid is evaluated, and the deterioration of the resin composition is evaluated. Derivation of the relationship between the change in the content of the end group and the change in the molecular weight enables more accurate deterioration evaluation. This is because how much the molecular weight is reduced can be specifically evaluated.
上記末端基の含有量の変化と分子量の変化との関係は、炭化水素系液体への浸漬時間毎に分子量及び末端基の含有量を測定することにより行うことができる。末端基の含有量の測定は上記の末端器の含有量の定量と同様の方法で行うことができる。また、分子量の測定方法は、特に限定されず従来公知の方法で行うことができる。従来公知の分子量の測定方法としては、例えば、サイズ排除クロマトグラフィー法により重量平均分子量又は数平均分子量を求めることができる。 The relationship between the change in the content of the end group and the change in the molecular weight can be performed by measuring the molecular weight and the content of the end group for each immersion time in the hydrocarbon-based liquid. The measurement of the content of the terminal group can be performed by the same method as the determination of the content of the terminal device. Moreover, the measuring method of molecular weight is not specifically limited, It can carry out by a conventionally well-known method. As a conventionally known molecular weight measurement method, for example, a weight average molecular weight or a number average molecular weight can be obtained by a size exclusion chromatography method.
ポリアセタール共重合体を含む樹脂組成物が劣化すると、分子量が減少する。この分子量の減少は末端基が増加することを意味する。そこで、上記のＮＭＲ等の方法で測定した結果から求められる−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量の増加量と、を重量平均分子量及び／又は数平均分子量の減少量と併せて考慮することで、劣化の程度をより正確に予測することができる。 When the resin composition containing the polyacetal copolymer deteriorates, the molecular weight decreases. This decrease in molecular weight means an increase in end groups. Therefore, the amount of increase in the content of —CH 2 CH 2 OCHO end groups determined from the result of measurement by the above-described NMR method or the like should be considered together with the amount of decrease in weight average molecular weight and / or number average molecular weight. Thus, the degree of deterioration can be predicted more accurately.
以下に、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらの実施例により限定されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
＜実施例１＞
ポリアセタール系樹脂（ジュラコンＭ９０−４４、ポリプラスチックス株式会社製）からなる試験片を用意した。
<Example 1>
A test piece made of a polyacetal resin (Duracon M90-44, manufactured by Polyplastics Co., Ltd.) was prepared.
試験片と市販の軽油とを耐圧容器に入れた後、この耐圧容器を１１０℃メタルバスにて表１に示す時間加熱した。加熱後、取り出した試験片を洗浄し、表面から２００μｍまでの領域を切削しサンプルとし、末端基分析のためのＮＭＲスペクトル測定・末端基分析、重量平均分子量、数平均分子量測定を下記の条件で行った。末端基の分析結果、重量平均分子量（Ｍｗ）、数平均分子量（Ｍｎ）の結果を表１、２に示した。 After putting a test piece and commercially available light oil in a pressure vessel, the pressure vessel was heated in a 110 ° C. metal bath for the time shown in Table 1. After heating, the taken-out test piece is washed, the region from the surface to 200 μm is cut to make a sample, and NMR spectrum measurement / terminal group analysis, weight average molecular weight, number average molecular weight measurement for end group analysis are performed under the following conditions. went. The results of end group analysis, weight average molecular weight (Mw), and number average molecular weight (Mn) are shown in Tables 1 and 2.
［ＮＭＲ測定条件］
ＮＭＲ装置：ＡＣ４００Ｐ型（ブルカー社製）
パルスフィリップアングル：３０♯
積算繰り返し時間：１０ｓｅｃ
積算回数：１２８回
[NMR measurement conditions]
NMR apparatus: AC400P type (Bruker)
Pulse Philip angle: 30 #
Integration repetition time: 10 sec
Integration count: 128 times
重水素化ヘキサフルオロイソプロピルアルコール（ＨＦＩＰ）を溶媒として濃度５質量％に溶解して、溶液をＮＭＲ用サンプル管に充填し、室温で、ＮＭＲスペクトルを測定した。ピーク面積をもとに、ポリマー主鎖のＨ量を基準に、−ＣＨ２ＯＣＨＯ末端基、−ＣＨ２ＣＨ２ＯＣＨＯ末端基の含有量を定量した。 Deuterated hexafluoroisopropyl alcohol (HFIP) was dissolved as a solvent to a concentration of 5% by mass, the solution was filled in an NMR sample tube, and an NMR spectrum was measured at room temperature. Based on the peak area, the content of —CH 2 OCHO end groups and —CH 2 CH 2 OCHO end groups was quantified based on the amount of H in the polymer main chain.
［分子量測定条件］
装置：ＨＬＣ−８２２０ＧＰＣ（東ソー社製）
カラム：ＴＳＫ−Ｇｅｌ Ｓｕｐｅｒ ＨＭ−Ｈ（日本）
溶媒：ＨＦＩＰ／５ｍＭ ＴＦＮａ（トリフルオロ酢酸ナトリウム）
流速：０．３ｍｌ／ｍｉｎ
検出器：ＲＩ
温度：４０℃
標準試料：ＰｏＬｙｍｅｒ Ｌａｂｏｒａｔｏｒｉｅｓ ＥａｓｉＣａｌ ＰＭ−１ ＰＭＭＡ Ｓｔａｎｄａｒｄｓ（Ｍｗ：１９４４０００〜１０２０）
[Molecular weight measurement conditions]
Apparatus: HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSK-Gel Super HM-H (Japan)
Solvent: HFIP / 5 mM TFNa (sodium trifluoroacetate)
Flow rate: 0.3 ml / min
Detector: RI
Temperature: 40 ° C
Standard sample: PoLymer Laboratories EasiCal PM-1 PMMA Standards (Mw: 1944000-1020)
表１、２から明らかなように本発明の評価方法を用いることで、樹脂成形品の劣化を正確に評価することができる。特に、本発明の評価方法を用いることで、浸漬後５００時間のわずかな劣化も評価することができる。 As is apparent from Tables 1 and 2, the deterioration of the resin molded product can be accurately evaluated by using the evaluation method of the present invention. In particular, by using the evaluation method of the present invention, a slight deterioration of 500 hours after immersion can be evaluated.
＜サンプル採取位置の比較＞
市販の軽油に試験片を（燃料中９０℃×１００時間＋空気中９０℃×４８時間）×１０サイクルの条件で浸漬させた。その後、試験片表面から２００μｍ以内の領域から採取したサンプルと試験片表面を３００μｍ切削した部分から採取した試験片内部のサンプルとについて、重量平均分子量、数平均分子量の測定を行った。測定結果を表３に示した。表３から明らかなように、劣化の程度は成形品表面付近で大きいことが確認された。なお、試験片及び分子量の測定条件は実施例１の条件と同様である。
<Comparison of sampling position>
The test piece was immersed in commercial light oil under the conditions of (90 ° C. in fuel × 100 hours + 90 ° C. in air × 48 hours) × 10 cycles. Then, the weight average molecular weight and the number average molecular weight were measured for a sample collected from a region within 200 μm from the surface of the test piece and a sample inside the test piece taken from a portion obtained by cutting the surface of the test piece by 300 μm. The measurement results are shown in Table 3. As is clear from Table 3, it was confirmed that the degree of deterioration was large near the surface of the molded product. The measurement conditions for the test piece and molecular weight are the same as those in Example 1.
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