JP2009235365A - Polylactic acid composite molding, manufacturing method for polylactic acid composite molding, and surface member for automobile interior material - Google Patents
Polylactic acid composite molding, manufacturing method for polylactic acid composite molding, and surface member for automobile interior material Download PDFInfo
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本発明は、一体成形が困難なポリ乳酸を複合化することによって曲げ強度に優れ、大型成形物化が可能なポリ乳酸複合成形体及びその製造方法に関する。 The present invention relates to a polylactic acid composite molded body that has excellent bending strength and can be made into a large-sized molded product by compounding polylactic acid that is difficult to be integrally molded, and a method for producing the same.
また、本発明は自動車内装材用表面部材に関し、自動車の内装として用いられる天井、床カーペット、床マット、ドアトリム、シートカバー、パッケージトレイ表装、トランク内装などの表面部材として好適な自動車内装材用表面部材に関する。 The present invention also relates to a surface member for an automobile interior material, and a surface for an automobile interior material suitable as a surface member for a ceiling, floor carpet, floor mat, door trim, seat cover, package tray cover, trunk interior, etc. used as an interior of an automobile. It relates to members.
ポリ乳酸樹脂は、一般的に分子鎖中のエステル結合が加水分解することにより、その分子量が経時的に低下するという問題がある。分子量が低下したポリ乳酸樹脂は、曲げ強度などの力学特性等が低下して使用に耐えられなくなるなど、多くの問題が顕在化する。 A polylactic acid resin generally has a problem that its molecular weight decreases with time due to hydrolysis of an ester bond in a molecular chain. The polylactic acid resin having a reduced molecular weight reveals many problems, such as a decrease in mechanical properties such as bending strength, which makes it unusable.
このため、生分解性であるポリ乳酸樹脂を長期耐久製品に適用しようとする場合、その加水分解性の制御が大きな課題となる。ポリ乳酸樹脂の加水分解抑制には、下記のような手法がとられている。
（１）酸点であるポリ乳酸樹脂の末端ＣＯＯＨ基を、イミド基（＝ＮＨ）を有するモノカルボジイミド類、またはこれの高分子体であるポリカルボジイミド類によって封止する方法
（２）酸点であるポリ乳酸樹脂の末端ＣＯＯＨ基をメチル基などの他の官能基で修飾する手法
（３）酸点であるポリ乳酸樹脂の末端ＣＯＯＨ基をイソシアネート基（＝ＮＣＯ）を有する水性イソシアネート類によって封止する方法
（４）他の樹脂を混合させることにより、樹脂中のＣＯＯＨ基濃度そのものを低減させる方法
For this reason, when it is going to apply the polylactic acid resin which is biodegradable to a long-term durable product, the control of the hydrolyzability becomes a big subject. The following methods are used to suppress hydrolysis of the polylactic acid resin.
(1) A method in which the terminal COOH group of a polylactic acid resin that is an acid point is sealed with monocarbodiimides having an imide group (= NH), or polycarbodiimides that are polymers thereof (2) at an acid point Method of modifying terminal COOH group of polylactic acid resin with other functional groups such as methyl group (3) Sealing terminal COOH group of polylactic acid resin which is acid point with aqueous isocyanate having isocyanate group (= NCO) (4) A method of reducing the COOH group concentration itself in the resin by mixing other resin
（２）の手法は、そもそも樹脂の重合段階から制御する必要があり、汎用性に欠ける。また、現在の樹脂の製造工程自体を見直す必要があり、すぐの実現は難しい。（３）の方法は、ポリ乳酸を有機溶剤中に分散後、水中に分散し、さらにエチルメチルケトンオキシムによってブロックされた水性イソシアネートを用いる方法であり、製法が煩雑な上、水中に分散されたイソシアネートが揮発し、人体に影響を及ぼすことが考えられ、工業化は困難である。（４）の方法は、樹脂全体の酸点は減るが、ポリ乳酸の使用率が下がる。すなわち樹脂中の植物割合が低下し、そもそもの植物由来のコンセプトを否定する。そもそも酸点量の割合を低下させただけなので、根本的な解決ではない。 In the first place, the method (2) needs to be controlled from the polymerization stage of the resin and lacks versatility. In addition, it is necessary to review the current resin manufacturing process itself, which is difficult to realize immediately. The method (3) is a method in which polylactic acid is dispersed in an organic solvent and then dispersed in water, and further, an aqueous isocyanate blocked with ethyl methyl ketone oxime is used. Isocyanate volatilizes and may affect the human body, making industrialization difficult. In the method (4), the acid point of the whole resin is reduced, but the usage rate of polylactic acid is lowered. In other words, the proportion of plants in the resin decreases, denying the concept derived from plants in the first place. In the first place, it is not a fundamental solution because it only reduces the proportion of the acid point amount.
以上の点から（１）の手法が、製造工程を変化させることなく、一番汎用性があると考えられる。下記特許文献１には、生分解性プラスチック組成物の耐加水分解性、耐熱性、透明性等の向上の為、脂肪族系ポリエステルに対し、分子中に１個以上のカルボジイミド基を有するカルボジイミド化合物を特定量配合することの開示がある。しかしながら、カルボジイミド化合物は、添加量が多いとゲル化しやすく、添加量を増やすと成形性を悪化させてしまう問題がある。 From the above points, the method (1) is considered to have the most versatility without changing the manufacturing process. The following Patent Document 1 discloses a carbodiimide compound having one or more carbodiimide groups in the molecule for aliphatic polyesters in order to improve hydrolysis resistance, heat resistance, transparency and the like of the biodegradable plastic composition. There is a disclosure of blending a specific amount. However, the carbodiimide compound tends to be gelled when the addition amount is large, and the moldability is deteriorated when the addition amount is increased.
一方、自動車内の天井、カーペット、トリム類、シートカバー等の自動車内装材には、石油系プラスチック短繊維を使用した不織布が使用されていたが、石油系プラスチックは難分解性であるため、ゴミ処理問題等、循環型社会を実践する上で大きな障害となっている。また、焼却時に発生する二酸化炭素は地球温暖化の原因となっている。加えて、原料が石油由来であるため化石資源の枯渇の問題が懸念されている。そのような状況の中、自動車内装材に使用される石油系プラスチック短繊維不織布においても、その代替、使用量低減が検討されている。 On the other hand, non-woven fabrics using petroleum-based plastic short fibers were used for automobile interior materials such as ceilings, carpets, trims, and seat covers in automobiles. This is a major obstacle to practicing a recycling society, such as disposal problems. Carbon dioxide generated during incineration is a cause of global warming. In addition, since the raw material is derived from petroleum, there is a concern about the problem of depletion of fossil resources. Under such circumstances, substitution and reduction of the amount of use of petroleum-based plastic short fiber nonwoven fabrics used for automobile interior materials are being studied.
短繊維不織布に使用する繊維の代替材料として、トウモロコシなどの植物資源を原料とするポリ乳酸成形体の使用が検討されている。ところで、自動車部材は安全上の観点から所定の強度および耐久性を必要とするが、ポリ乳酸単体にて形成された成形体は、その強度や耐久性が従来の合成樹脂製成形体よりも劣っている。このため、従来のポリ乳酸単体にて形成された成形体は、強度および耐久性が要求される自動車内装材用表面部材での使用は限定されているのが現状である。 As an alternative material for fibers used in short fiber nonwoven fabrics, the use of a polylactic acid molded body made of plant resources such as corn is considered. By the way, although automobile members require a predetermined strength and durability from the viewpoint of safety, a molded body formed of polylactic acid alone is inferior in strength and durability to a conventional synthetic resin molded body. ing. For this reason, the present condition that the molded object formed with the conventional polylactic acid single-piece | unit is limited in the surface member for motor vehicle interior materials by which intensity | strength and durability are requested | required.
又、ポリ乳酸は結晶性樹脂であるが、その結晶化速度は遅く、実際には非晶性樹脂に近い挙動を示す。すなわち、ガラス転移温度付近で急激に且つ極度に軟化するため（通常、弾性率１／１００未満）、耐熱性、成形性、離型性、耐衝撃性などの点で十分な特性を得ることが困難であった。特に、大型成形品を得ることが困難であった。 Polylactic acid is a crystalline resin, but its crystallization rate is slow, and actually shows a behavior close to that of an amorphous resin. That is, since it softens rapidly and extremely near the glass transition temperature (usually less than 1/100 elastic modulus), sufficient characteristics can be obtained in terms of heat resistance, moldability, releasability, impact resistance, and the like. It was difficult. In particular, it was difficult to obtain a large molded product.
下記特許文献２には、カルボジイミド化合物を添加したポリ乳酸系樹脂をバインダとした天然繊維による繊維系ボード及びその製造方法が開示されている。特許文献２には、この繊維系ボードは、高温高湿下での曲げ強度保持率が高いこと、見かけ密度が０．２ｇ／ｃｍ３以上、カルボキシル末端量は１０当量以下、残留ポリマー量が５００ｐｐｍ以下であることも開示されている。 Patent Document 2 below discloses a fiber board made of natural fibers using a polylactic acid resin to which a carbodiimide compound is added as a binder, and a method for producing the same. In Patent Document 2, this fiber board has a high bending strength retention under high temperature and high humidity, an apparent density of 0.2 g / cm 3 or more, a carboxyl end amount of 10 equivalents or less, and a residual polymer amount of 500 ppm. It is also disclosed that:
特許文献２のように、天然繊維にバインダとしてカルボジイミド化合物を添加したポリ乳酸系樹脂を使用した繊維系ボードでは、加水による天然繊維とバインダの膨潤率の違い（カルボジイミド添加量により変化）から、繊維系ボード表面に微小の亀裂が発生し、天然繊維とバインダの界面から水が浸入して、バインダとなるポリ乳酸系樹脂が加水分解し、曲げ強度低下が加速する可能性がある。又、天然繊維は水分を吸収し易いため、バインダであるカルボジイミド化合物を添加したポリ乳酸系樹脂の加水分解を促進させてしまい、高価なカルボジイミドを余分に消費してしまう可能性がある。これは、バインダであるカルボジイミド化合物を添加したポリ乳酸系樹脂の劣化モードが、カルボジイミドの添加量により変化することを考慮したボード構造として設計していないためであり、又、ボード表面側に天然繊維が露出しているため、ボード表面とボード内部にわたって存在する天然繊維は、水分を表面側から内部に輸送するネットワーク（経路）を形成してしまうからである。 As in Patent Document 2, in a fiber board using a polylactic acid resin in which a carbodiimide compound is added to a natural fiber as a binder, the difference in swelling ratio between the natural fiber and the binder due to water (changes depending on the amount of carbodiimide added) There is a possibility that minute cracks are generated on the surface of the system board, water enters from the interface between the natural fibers and the binder, the polylactic acid resin serving as the binder is hydrolyzed, and the decrease in bending strength is accelerated. Moreover, since natural fibers are easy to absorb moisture, hydrolysis of the polylactic acid resin to which a carbodiimide compound as a binder is added may be promoted, and expensive carbodiimide may be consumed excessively. This is because the degradation mode of the polylactic acid-based resin to which the carbodiimide compound as a binder is added is not designed as a board structure considering that the amount of carbodiimide changes depending on the amount of carbodiimide added. This is because the natural fiber existing over the board surface and the inside of the board forms a network (path) for transporting moisture from the surface side to the inside.
本発明は、上記の問題点を解決し、ポリ乳酸を使用した成形体でありながらも曲げ強度および耐湿熱分解性に優れ、このため自動車内装材に好適に使用することが可能な自動車内装材用表面部材を提供しようとするものである。 The present invention solves the above-described problems, and is an automotive interior material that is excellent in bending strength and wet heat decomposition resistance despite being a molded body using polylactic acid, and thus can be suitably used for an automotive interior material. An object surface member is to be provided.
本発明者は、カルボジイミド化合物の添加量を変えた２種以上の材料を複合化することによって、上記の課題が解決されることを見出し、本発明に到達した。 The present inventor has found that the above-mentioned problems can be solved by combining two or more kinds of materials in which the addition amount of the carbodiimide compound is changed, and has reached the present invention.
即ち、第１に、本発明は、カルボジイミド化合物を添加した複数のポリ乳酸成形体を組合せて熱圧着した複合成形体の発明であって、これら複数のポリ乳酸成形体が異なるカルボジイミド化合物量を含有することを特徴とする。 That is, first, the present invention is an invention of a composite molded body obtained by thermocompression bonding of a plurality of polylactic acid molded bodies to which a carbodiimide compound is added, and the plurality of polylactic acid molded bodies contain different amounts of carbodiimide compounds. It is characterized by doing.
本発明のポリ乳酸複合成形体は、湿熱条件などの加水分解が生じやすい場合でも、曲げ強度などの力学物性に優れた耐加水分解性に優れる上に、一体成形が困難な複雑構造や大型構造に対しても、ブロック化した本発明のポリ乳酸複合成形体を組み合わせることで対応できる。 The polylactic acid composite molded body of the present invention has a complex structure or a large-scale structure that is difficult to integrally mold, in addition to being excellent in hydrolysis resistance excellent in mechanical properties such as bending strength, even when hydrolysis such as wet heat conditions is likely to occur. This can be addressed by combining the blocked polylactic acid composite molded body of the present invention.
本発明のポリ乳酸複合成形体では、初期の曲げ強度の６０％以上を確保するためには、カルボジイミド化合物を多量に添加したポリ乳酸成形体が、（１）ＡＴＲによる表面の結晶化度が０．１以下である、及び／又は（２）ＧＰＣによる重量平均分子量が１２５０００以上であり数平均分子量が６００００以上であるように、カルボジイミド化合物量を含有することが好ましい。ここで、結晶化度＝（９２４ｃｍ−１にあるピーク強度）÷（９５５ｃｍ−１にあるピーク強度）で算出される。 In the polylactic acid composite molded body of the present invention, in order to ensure 60% or more of the initial bending strength, the polylactic acid molded body to which a large amount of a carbodiimide compound is added has (1) a surface crystallinity of 0 by ATR. It is preferable that the amount of carbodiimide compound is contained so that the weight average molecular weight by GPC is 125000 or more and the number average molecular weight is 60000 or more. Here, calculated in crystallinity = (924cm peak intensity in -1) ÷ (peak intensity in the 955cm -1).
本発明のポリ乳酸複合成形体は、熱圧着する前のポリ乳酸成形体の枚数、形状、組合せなどにより、多数の変形が可能となる。その中には、更に、鉄材を組合せて熱圧着した複合成形体も含まれる。 The polylactic acid composite molded body of the present invention can be deformed in many ways depending on the number, shape, combination, etc. of the polylactic acid molded body before thermocompression bonding. Among them, a composite molded body obtained by thermocompression combining iron materials is also included.
第２に、本発明は、カルボジイミド化合物を添加した複数のポリ乳酸成形体を組合せ、これらの接合部を溶媒により溶融させた後、熱圧着をする複合成形体の製造方法の発明であって、これら複数のポリ乳酸成形体が異なるカルボジイミド化合物量を含有することを特徴とする。 Secondly, the present invention is an invention of a method for producing a composite molded body in which a plurality of polylactic acid molded bodies to which a carbodiimide compound is added are combined, and these joints are melted with a solvent, followed by thermocompression bonding. These plural polylactic acid molded products contain different amounts of carbodiimide compounds.
ポリ乳酸複合成形体の強度を確保するために、カルボジイミド化合物を多量に添加したポリ乳酸成形体が、（１）ＡＴＲによる表面の結晶化度が０．１以下である、及び／又は（２）ＧＰＣによる重量平均分子量が１２５０００以上であり数平均分子量が６００００以上であるように、カルボジイミド化合物量を含有することが好ましいこと、更に、鉄材を組合せて熱圧着した複合成形体とすることは上述の通りである。 In order to ensure the strength of the polylactic acid composite molded article, the polylactic acid molded article to which a carbodiimide compound is added in a large amount has (1) a crystallinity of the surface by ATR of 0.1 or less and / or (2) It is preferable to contain the amount of carbodiimide compound so that the weight average molecular weight by GPC is 125000 or more and the number average molecular weight is 60000 or more. Street.
本発明のポリ乳酸複合成形体の製造方法に用いる溶媒としては、ポリ乳酸樹脂の表面を溶融させるものであれば特に制限されない。これらの溶媒の中で、１，１，１，３，３，３−ヘキサフルオロ−２−プロパノールが好ましく例示される。 The solvent used in the method for producing the polylactic acid composite molded body of the present invention is not particularly limited as long as it melts the surface of the polylactic acid resin. Among these solvents, 1,1,1,3,3,3-hexafluoro-2-propanol is preferably exemplified.
第３に、本発明は、上記のポリ乳酸複合成形体の用途に関するもので、カルボジイミド化合物を添加した複数のポリ乳酸成形体を組合せて熱圧着した複合成形体からなる自動車内装材用表面部材であって、これら複数のポリ乳酸成形体が異なるカルボジイミド化合物量を含有することを特徴とする。 Thirdly, the present invention relates to the use of the above-mentioned polylactic acid composite molded body, and is a surface member for an automotive interior material comprising a composite molded body obtained by thermocompression bonding of a plurality of polylactic acid molded bodies added with a carbodiimide compound. The plurality of polylactic acid molded products contain different amounts of carbodiimide compounds.
本発明の自動車内装材用表面部材は、自動車の内装として、天井、床カーペット、床マット、ドアトリム、シートカバー、パッケージトレイ表装、トランク内装などの表面部材として好適である。 The surface member for automobile interior material according to the present invention is suitable as a surface member for an automobile interior such as a ceiling, floor carpet, floor mat, door trim, seat cover, package tray cover, trunk interior.
本発明のポリ乳酸複合成形体は、曲げ強度などの力学物性に優れ、耐加水分解性に優れる上に、一体成形が困難な複雑構造や大型構造に対しても対応できる。特に、用途に応じて、曲げ強度半減期を調節することが可能であり、自動車内装材用表面部材などの種々の用途に適用できる。 The polylactic acid composite molded body of the present invention is excellent in mechanical properties such as bending strength, is excellent in hydrolysis resistance, and can cope with complex structures and large structures in which integral molding is difficult. In particular, it is possible to adjust the bending strength half-life according to the use, and it can be applied to various uses such as a surface member for automobile interior materials.
図１に、本発明のポリ乳酸複合成形体の概念と原理を示す。カルボジイミド化合物を少量添加したポリ乳酸（ＰＬＡ）成形体は曲げ強度半減期が短い。これに対して、カルボジイミド化合物を多量に添加したポリ乳酸（ＰＬＡ）成形体は曲げ強度半減期が長い。図１に示すように、カルボジイミド化合物を少量添加したポリ乳酸（ＰＬＡ）成形体の両側にカルボジイミド化合物を多量に添加したポリ乳酸（ＰＬＡ）成形体をはさみ、その接合面を溶媒で溶解して熱圧着すると、曲げ強度半減期が所望の値に調節されたポリ乳酸複合成形体が得られる。 FIG. 1 shows the concept and principle of the polylactic acid composite molded article of the present invention. A polylactic acid (PLA) molded body to which a small amount of a carbodiimide compound is added has a short bending strength half-life. On the other hand, a polylactic acid (PLA) molded body to which a large amount of a carbodiimide compound is added has a long bending strength half-life. As shown in FIG. 1, a polylactic acid (PLA) molded body added with a large amount of a carbodiimide compound is sandwiched between both sides of a polylactic acid (PLA) molded body added with a small amount of a carbodiimide compound, and the joint surface is dissolved with a solvent and heated. By pressure bonding, a polylactic acid composite molded body having a flexural strength half-life adjusted to a desired value is obtained.
［ポリ乳酸（ＰＬＡ）成形体の曲げ強度］
ポリ乳酸樹脂にカルボジイミドを添加した樹脂組成物の曲げ強度変化を確認するため、下記の材料を用いて湿熱老化加速試験を実施した。
[Bending strength of molded polylactic acid (PLA)]
In order to confirm the bending strength change of the resin composition obtained by adding carbodiimide to the polylactic acid resin, a wet heat aging acceleration test was performed using the following materials.
本データで、ポリ乳酸（ＰＬＡ）成形体単体の曲げ強度の経年変化が分かるため、単体を組合せた場合の曲げ強度を材料カ学から予測することが可能になる。 With this data, the change over time of the bending strength of the polylactic acid (PLA) molded body alone can be understood, so that the bending strength when the single bodies are combined can be predicted from the material theory.
使用材料として、（１）重量平均分子量が１６万のポリ乳酸樹脂、（２）重量平均分子量が１６万のポリ乳酸樹脂にカルボジイミドを各々０．５、１．０、５．０、１０．０重量部配合した樹脂組成物を用意した。 As materials used, (1) polylactic acid resin having a weight average molecular weight of 160,000, (2) polylactic acid resin having a weight average molecular weight of 160,000, carbodiimide was 0.5, 1.0, 5.0, 10.0, respectively. A resin composition containing parts by weight was prepared.
図２に、曲げ強度を測定する試験手順を示す。（１）ＩＳＯ・Ａ型試験片を１軸射出成形器で成形する。（２）成形品を耐候試験槽に整置する。（３）８０％、９５ＲＨ雰囲気下（耐候試験槽内）で成形品を処理する。（４）成形品を取り出す。（５）曲げ強度を測定する。 FIG. 2 shows a test procedure for measuring the bending strength. (1) An ISO / A type test piece is molded with a single-screw injection molding machine. (2) Place the molded product in a weathering test tank. (3) Treat the molded product in an 80%, 95RH atmosphere (in the weathering test tank). (4) Take out the molded product. (5) Measure the bending strength.
図３に、各試料の処理時間と曲げ強度の関係を示す。図３の結果より、カルボジイミドの添加量が多いほど、曲げ強度の低下率が小さいことが分かる。 FIG. 3 shows the relationship between the processing time and bending strength of each sample. From the results of FIG. 3, it can be seen that the greater the amount of carbodiimide added, the smaller the rate of decrease in bending strength.
［結晶化度と曲げ強度の関係］
各試料表面のＡＴＲ（全反射（吸収）分光法）スペクトルを求め、結晶化度と曲げ強度の関係、及び、試験時間と曲げ強度の関係を求めた。その結果、初期の曲げ強度の６０％以上を得るためには、結晶化度（９２４ｃｍ‐１にあるピーク強度／９５５‐１ｃｍにあるピーク強度。アルファ型を反映）が０．１０以下であることが必要なことが分かった。また、試験時間が長いほど、結晶化度が大きくなることが分かった。
[Relationship between crystallinity and bending strength]
The ATR (total reflection (absorption) spectroscopy) spectrum of each sample surface was determined, and the relationship between crystallinity and bending strength, and the relationship between test time and bending strength were determined. As a result, in order to obtain more than 60% of the initial bending strength, crystallinity (peak intensity at the peak intensity / 955 -1 cm in the 924cm -1. Reflecting alpha form) is 0.10 or less I found that it was necessary. It was also found that the longer the test time, the greater the crystallinity.
［分子量と曲げ強度の関係］
各試料の表面と内部のＧＰＣ（ゲル浸透クロマトグラフ法）により重量平均分子量と数平均分子量を求め、重量平均分子量と曲げ強度の関係、及び、数平均分子量と曲げ強度の関係を求めた。実験条件は、
溶媒：クロロホルム
サンプル濃度：約０．４ｗｔ％
注入量：２０μＬ
カラム：ＴＳＫｇｅｌ ＧＭＨＨＲ‐Ｍ（排除限界４００００００）
流量：１．０ｍＬ／ｍｉｎ
オーブン温度：４０℃
検出器（ＩＲ）温度：４０℃
であった、検出部位は、表面部位が表面から深さ０〜０．５ｍｍの範囲、内部部位が深さ０．５ｍｍ以上である。
[Relationship between molecular weight and bending strength]
The weight average molecular weight and the number average molecular weight were determined by GPC (gel permeation chromatography) on the surface and inside of each sample, and the relationship between the weight average molecular weight and the bending strength and the relationship between the number average molecular weight and the bending strength were determined. Experimental conditions are
Solvent: Chloroform Sample concentration: About 0.4 wt%
Injection volume: 20 μL
Column: TSKgel GMH HR- M (exclusion limit 4000000)
Flow rate: 1.0 mL / min
Oven temperature: 40 ° C
Detector (IR) temperature: 40 ° C
As for the detection site, the surface site has a depth of 0 to 0.5 mm from the surface, and the internal site has a depth of 0.5 mm or more.
その結果、重量平均分子量と曲げ強度には正の相関が、数平均分子量と曲げ強度にも正の相関があることが分かった。初期の曲げ強度の６０％以上を得るためには、重量平均分子量が１２５０００以上、数平均分子量が６００００以上の樹脂組成物であればよいことが分かった。 As a result, it was found that there was a positive correlation between the weight average molecular weight and the bending strength, and a positive correlation between the number average molecular weight and the bending strength. It was found that a resin composition having a weight average molecular weight of 125,000 or more and a number average molecular weight of 60000 or more was sufficient to obtain 60% or more of the initial bending strength.
図４に、推定されるポリ乳酸が劣化するメカニズムを示す。ポリ乳酸樹脂のＣＯＯＨ基による劣化には、（１）初期段階で既に存在するポリ乳酸末端基ＣＯＯＨ基による分子鎖切断、（２）劣化（＝分子鎖切断）によって生じるＣＯＯＨ基による分子鎖切断の２つのモードがあるが、高温高湿初期では、カルボジイミドを添加することにより、ＣＯＯＨ基を封鎖する反応と水を吸水する反応が進むため、ポリ乳酸の加水分解反応を抑制することが可能である。しかし、高温高湿条件が長くなると、脱水触媒としても作用するカルボジイミドが減少し、封鎖されたＣＯＯＨ基も加水分解反応して、樹脂組成物の劣化が進む。この際、劣化は表面側からバルク側への水拡散に伴う化学反応に依存するため、高温高湿条件でカルボジイミド量が少ないと、加水分解反応速度が大きくなり、急激な曲げ強度変化となってしまう。本発明により、表面側からバルク側への水拡散に伴う化学反応を制御することが可能であるため、曲げ強度半減期を制御（急激に減少させない等）することが可能である。 FIG. 4 shows a mechanism by which the estimated polylactic acid deteriorates. Degradation due to COOH groups of polylactic acid resin includes (1) molecular chain cleavage by polylactic acid end group COOH groups already present in the initial stage, and (2) molecular chain cleavage by COOH groups caused by degradation (= molecular chain cleavage). There are two modes, but at the beginning of high temperature and high humidity, by adding carbodiimide, the reaction of blocking the COOH group and the reaction of absorbing water proceed, so it is possible to suppress the hydrolysis reaction of polylactic acid. . However, when the high-temperature and high-humidity conditions become longer, the carbodiimide that also acts as a dehydration catalyst decreases, and the blocked COOH group also undergoes a hydrolysis reaction, leading to deterioration of the resin composition. At this time, since the deterioration depends on the chemical reaction accompanying water diffusion from the surface side to the bulk side, if the amount of carbodiimide is small under high temperature and high humidity conditions, the hydrolysis reaction rate increases, resulting in a sudden bending strength change. End up. According to the present invention, it is possible to control the chemical reaction accompanying the water diffusion from the surface side to the bulk side, and therefore it is possible to control the bending strength half-life (not to reduce it rapidly).
又、カルボジイミド化合物は、（１）高価、（２）添加量が多いとゲル化して成形性を悪化、（３）人体に皮膚炎症などの悪影響を及ぼす。本発明では、余分なカルボジイミド化合物の添加量を減らすことにより、（１）〜（３）を改善することができる。 In addition, the carbodiimide compound (1) is expensive, (2) if it is added in a large amount, the carbodiimide compound gels and deteriorates moldability, and (3) adversely affects the human body such as skin inflammation. In the present invention, (1) to (3) can be improved by reducing the amount of extra carbodiimide compound added.
ポリ乳酸にカルボジイミドを０．５ｗｔ％添加した材料、ポリ乳酸にカルボジイミドを５ｗｔ％添加した材料、ポリ乳酸にカルボジイミドを０．５ｗｔ％添加した材料の両側にポリ乳酸にカルボジイミドを５ｗｔ％添加した材料を挟んだ試料を用意し、それぞれＪＩＳ Ｋ７１７１（１９９４、ＩＳＯ １７８）に基づき、１０×４ｍｍ２の試料を作製した。 A material obtained by adding 0.5 wt% of carbodiimide to polylactic acid, a material obtained by adding 5 wt% of carbodiimide to polylactic acid, and a material obtained by adding 5 wt% of carbodiimide to polylactic acid on both sides of a material obtained by adding 0.5 wt% of carbodiimide to polylactic acid. A sandwiched sample was prepared, and a 10 × 4 mm 2 sample was prepared based on JIS K7171 (1994, ISO 178).
各試料を８０℃、９５％で９６時間の耐久試験を行った後、曲げ強度を測定した。その結果、ポリ乳酸にカルボジイミドを０．５ｗｔ％添加した材料は１４．４９ＭＰａ、ポリ乳酸にカルボジイミドを５ｗｔ％添加した材料は７２．０５ＭＰａ、ポリ乳酸にカルボジイミドを０．５ｗｔ％添加した材料の両側にポリ乳酸にカルボジイミドを５ｗｔ％添加した材料を挟んだ試料は４７．５７ＭＰａであった。 Each sample was subjected to an endurance test at 80 ° C. and 95% for 96 hours, and then the bending strength was measured. As a result, a material obtained by adding 0.5 wt% of carbodiimide to polylactic acid is 14.49 MPa, a material obtained by adding 5 wt% of carbodiimide to polylactic acid, and 72.05 MPa of material obtained by adding 0.5 wt% of carbodiimide to polylactic acid. A sample sandwiching a material obtained by adding 5 wt% of carbodiimide to polylactic acid was 47.57 MPa.
これにより、カルボジイミド化合物の添加量が異なる材料を組み合わせることで曲げ応力の制御が可能であることが分かる。
＜実施例：適用例＞
Thereby, it turns out that control of a bending stress is possible by combining the material from which the addition amount of a carbodiimide compound differs.
<Example: Application example>
図５に、本発明のポリ乳酸複合成形体を自動車内装部材に適用した例を示す。図５中、接合部とは、カルボジイミド化合物を少量添加したポリ乳酸成形体とカルボジイミド化合物を多量に添加したポリ乳酸成形体とを熱圧着した際に生成した両者が溶融混合した部分である。本発明の自動車内装部材は、車内側にカルボジイミド化合物を多量に添加したポリ乳酸成形体を備え、車外側にカルボジイミド化合物を少量添加したポリ乳酸成形体を備えている。 FIG. 5 shows an example in which the polylactic acid composite molded body of the present invention is applied to an automobile interior member. In FIG. 5, the bonded portion is a portion where both of the polylactic acid molded body added with a small amount of carbodiimide compound and the polylactic acid molded body added with a large amount of carbodiimide compound are melt mixed. The automobile interior member of the present invention includes a polylactic acid molded body in which a large amount of a carbodiimide compound is added to the inside of a vehicle, and a polylactic acid molded body in which a small amount of a carbodiimide compound is added to the outside of the vehicle.
生分解性であるポリ乳酸樹脂をその用途に応じて、曲げ強度半減期を調節することを可能とし、一体成形が困難な複雑構造や大型構造に対しても対応できる。これにより、ポリ乳酸樹脂を自動車内装材用表面部材などの種々の用途に適用できる。 The polylactic acid resin, which is biodegradable, can be adjusted in flexural strength half-life according to its use, and can cope with complicated structures and large structures where integral molding is difficult. Thereby, polylactic acid resin is applicable to various uses, such as a surface member for automobile interior materials.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120231256A1 (en) * | 2010-03-15 | 2012-09-13 | Lg Hausys, Ltd. | Chip through flooring material using pla resin |
| US20130004751A1 (en) * | 2010-03-15 | 2013-01-03 | Lg Hausys, Ltd. | Floor material using pla resin |
| JP2014100859A (en) * | 2012-11-21 | 2014-06-05 | Jfe Steel Corp | Polylactic acid-based resin coated metal sheet for container |
| JP2016180660A (en) * | 2015-03-24 | 2016-10-13 | 日本電信電話株式会社 | Estimation method and estimation device |
| US9499481B2 (en) | 2008-05-26 | 2016-11-22 | Arkema France | Method for preparing lactames, comprising a photonitrosation step, followed by a Beckmann transposition step |
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- 2008-03-28 JP JP2008086993A patent/JP2009235365A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9499481B2 (en) | 2008-05-26 | 2016-11-22 | Arkema France | Method for preparing lactames, comprising a photonitrosation step, followed by a Beckmann transposition step |
| US20120231256A1 (en) * | 2010-03-15 | 2012-09-13 | Lg Hausys, Ltd. | Chip through flooring material using pla resin |
| US20130004751A1 (en) * | 2010-03-15 | 2013-01-03 | Lg Hausys, Ltd. | Floor material using pla resin |
| US9517612B2 (en) * | 2010-03-15 | 2016-12-13 | Lg Hausys, Ltd. | Floor material using PLA resin |
| US9623635B2 (en) * | 2010-03-15 | 2017-04-18 | Lg Hausys, Ltd. | Chip through flooring material using PLA resin |
| JP2014100859A (en) * | 2012-11-21 | 2014-06-05 | Jfe Steel Corp | Polylactic acid-based resin coated metal sheet for container |
| JP2016180660A (en) * | 2015-03-24 | 2016-10-13 | 日本電信電話株式会社 | Estimation method and estimation device |
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