Chapter VI LINK3">LINK1">Resin Explanation
一：树脂质量的LINK4">影响因素
I. LINK5">Influencing Factors on Resin Quality
（1）甲醛与苯酚的比例
(1) LINK12">Ratio of LINK13">formaldehyde to phenol
LINK30">LINK9">缩聚反应**初生成LINK6">LINK7">预聚物的LINK144">性质取决于甲醛与苯酚的LINK26">克分子用量比。当克分子比F/P﹤1时，反应的初期生成产物为LINK37">LINK38">LINK31">邻-羟甲基苯酚与LINK34">对-羟甲基苯酚的混合物。其中以邻-羟甲基苯酚的含量LINK40">较多，羟甲基苯酚中的羟甲基能与苯酚反应生成各种衍生物。若F/P﹥2，则反应初期生成LINK41">LINK42">多元羟甲基苯酚，经进一步的缩聚，则LINK44">交联形成不溶、不熔的树脂。因此P/F的值应在1-2之间。
The properties of prepolymer initially generated by the LINK25">polycondensation reaction depend on LINK27">molar ratio of formaldehyde to phenol. If the LINK28">F/P molar ratio is smaller than 1, the product primarily formed by the reaction will be the mixture of o-(hydroxymethyl)phenol and p-LINK35">LINK36">(LINK39">hydroxymethyl)phenol, of which the o-(hydroxymethyl)phenol is relatively more and the hydroxymethyl and the phenol in the (hydroxymethyl)phenol can generate a variety of derivatives. If the F/P ratio is greater than 2, LINK43">multi-hydroxymethyl phenol will be generated at the beginning of the reaction, and will be cross-
（2）反应介质的pH值及LINK32">碱用量的影响
(2) Influence of pH value of reaction medium and alkali content
苯酚与甲醛反应时反应介质的pH值对反应过程有很大的影响。在酸性或中性介质中，苯酚与甲醛所生成的羟甲基苯酚很不稳定，彼此间与苯酚很快地产生缩聚反应。在碱性介质中，羟甲基苯酚是稳定的，只有升高温度或加入酸性催化剂时，LINK11">缩聚反应才能继续进行。在碱性介质中，即使苯酚与甲醛的用量比有很大变化时，也只能生成热塑性树脂。
实验中，采用在碱性条件下进行反应，甲醛过量，碱的用量为1.5%。
The pH value of reaction medium during the reaction of phenol and formaldehyde has a significant influence on the reaction process. With an acidic or neutral medium, the hydroxymethyl phenol generated by phenol and formaldehyde is very unstable and will LINK10">induce the polycondensation reaction with phenol quickly. With an alkaline medium, the hydroxymethyl phenol is stable, and the polycondensation reaction may proceed only when temperature rises or acid catalyst is added. Thermoplastic resins are only generated with the alkaline medium even if the ratio of formaldehyde to phenol has a great change. In the experiment, the reaction takes place under the alkaline condition with excess formaldehyde and 1.5% LINK148">alkali.
（3）LINK33">反应时间的影响
(3) Influence of reaction time
苯酚与甲醛在催化剂的作用下进行缩聚反应，反应时间过长，所得LINK14">LINK15">高聚物粘度过大，以致影响脱水反应，并使贮存期缩短。若聚合时间过短，LINK16">反应不完全，产品中游离酚和游离醛的含量增加，收率降低。我们选择首先在72℃左右反应3.25小时，使苯酚与甲醛反应形成羟甲基酚，达到要求的分子量及粘度。
LINK18">Phenol and formaldehyde undergo the polycondensation reaction under the action of catalyst. If the reaction time is too long, the viscosity of the high polymer generated will be too high. As a result, the dehydration reaction will be affected and the storage period will be shortened. If the polymerization time is too short, LINK17">the reaction will be inadequate, free phenol and free formaldehyde in the product will increase and the yield will decrease. It is chosen to induce the reaction for 3.25 hours at
二：树脂的性能