樹脂

樹脂 化学特性,用途語,生産方法

• 解説

  樹脂，樹木からにじみでる粘りけのある物質。天然樹脂ともいう。しかし日常用語であるため，かなり広範囲の物質が樹脂とよばれている。天然物ではない石油起源の物質が，合成樹脂(プラスチック)とよばれているのはその一例である。天然樹脂が添加物とともに加熱されると成型品になるので，合成品でも成型品となるものは樹脂とよばれたのであろう。なお，シェラックなど寄生昆虫の分泌物は動物性の天然樹脂といえる。また樹脂の化石がコハクで，しばしば昆虫の化石などを含む。

  株式会社平凡社 世界大百科事典 第２版について　情報
  

• 用途

  天然に，特に植物に生じたやに状物質をいう。樹皮を傷つけると出る樹液が，揮発性分を失ったのちの固体。水に溶けにくいが，アルコールやテレビン油のような有機溶媒に溶けやすく，溶媒の揮発後は薄膜となって残る高分子化合物で，この性質を利用して塗料や充填剤として使われる。

• 化学的特性

  It has no definite melting point and no tendency to crystallize.

• 使用

  resin is used to give gloss, flow, adhesion, and water resistance to cosmetics. This is a brittle substance, usually translucent or transparent, that can be found in nature or synthetically manufactured. Among the natural resins are dammar, elemi, and sandarac, which are formed from the hardened secretions of these plants. Toxicity and allergenicity depend on the source used.

• 定義

  A yellowish insoluble organic compound exuded by trees as a viscous liquid that gradually hardens on exposure to air to form a brittle amorphous solid. Synthetic resins are artificial polymers used in making adhesives, insulators and paints. See also rosin.

• 工業用途

  Originally a category of vegetable substancessoluble in ethanol but insoluble in water, resinin modern technology is generally an organicpolymer of indeterminate molecular weight.The class of flammable, amorphous secretionsof conifers or legumes are considered true resins,and include kauri, copal, dammar, mastic,guaiacum, jalap, colophony, shellac, andnumerous less well-known substances. Waterswellablesecretions of various plants, especiallythe Burseraceae, are called gum resinsand include myrrh and olibanum The officialresins are benzoin, guaiac, mastic, and resin.Other natural resins are copal, dammar,dragon’s blood, elaterium, lac, and sandarac.The natural vegetable resins are largely polyterpenesand their acid derivatives, which find application in the manufacture of lacquers,adhesives, varnishes, and inks.

• 作用機序

  Prior to the introduction of the statins in the mid to late 1980s, the bile acid–sequestering drugs cholestyramine (Questran) and colestipol (Colestid) were primary drugs for lowering plasma cholesterol. Today they are second-line drugs that can safely be given with a statin to enhance cholesterol lowering or as an alternative for patients intolerant to a statin or concerned with statin’s potential for toxicity.Alone, the resins can achieve 20 to 25% reductions in LDL cholesterol, but when used with a statin, such as lovastatin, reductions of 50% and more can be seen.
  These drugs are basically anion exchange resins that remain in the gut, bind intestinal bile acids, and greatly increase their fecal excretion.
  The lowered concentration of bile acids returning to the liver by the enterohepatic circulation results in derepression of 7-α-hydroxylase, the rate-limiting enzyme for conversion of cholesterol to bile acids.This results in increased use of cholesterol to replace the excreted bile acids and lowering of hepatic cholesterol. Thus, similar to the statins, the ultimate actions of the bile acid–sequestering resins are upregulation of transcription of the LDL receptor gene, increased hepatic receptor activity, and lowering of plasma LDL cholesterol.

• 臨床応用

  The bile acid sequestering resins lower elevated LDL cholesterol and therefore are useful in the treatment of type IIa hyperlipoproteinemia. However, because the resins can raise plasma VLDL in some patients, they are not recommended for treatment of combined hyperlipidemias when both LDL cholesterol and VLDL triglycerides are high or in other conditions of elevated triglycerides.

• 副作用

  The resins are interesting drugs because they have profound metabolic effects without truly entering the body. Perhaps for this reason they are relatively safe, with constipation being the chief complaint. Because the resins are given as the chloride salt and the chloride is exchanged for the negatively charged bile salt, bile acid resins can lead to hyperchloremic acidosis in vulnerable patients (children and patients with kidney failure).

樹脂 生産企業

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