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手工皂会比普通肥皂更温和更营养吗?

来源:中国女性网 编辑:璐璐 点击: 次日期:2016-01-15
近年来,一股手工制作肥皂(或称香皂)的风气逐渐风靡起来。手工制作肥皂是一个很有意思的DIY工作,难度适中,条件要求不高,又与日常生活密切相关,喜欢动手的同学不妨尝试一
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手工皂

  近年来,一股手工制作肥皂(或称香皂)的风气逐渐风靡起来。手工制作肥皂是一个很有意思的DIY工作,难度适中,条件要求不高,又与日常生活密切相关,喜欢动手的同学不妨尝试一下。

  不过,网上也有一些文章,声称这种采用冷工艺、手工制作的“冷制皂”,比工业化生产的肥皂对健康更有好处。比如,保留了很多天然有益成分、富含保湿因子、对皮肤更加温和等等,这些说法是不是真的呢?

  肥皂是什么

  要回答这个问题,首先就得说说肥皂到底是什么东西。简单地说,不管是工业还是手工制作的,肥皂都是用“油”和碱发生化学反应后的产物。确切地说,是由脂肪酸与氢氧化钠(NaOH,又称火碱、苛性钠,是一种碱性很强的物质)发生了皂化反应生成的脂肪酸钠。用一个简单的反应式可以表示为:

  脂肪酸甘油三脂+氢氧化钠 → 脂肪酸钠+甘油

 

  这里所说的脂肪酸,其实是一个很大的类别,至少可以分为饱和脂肪酸与不饱和脂肪酸两类,前者诸如猪油、牛油,后者则有橄榄油、椰子油等等。

  肥皂中起到洗去污渍作用的,正是脂肪酸钠。因此,脂肪酸钠的质量,直接关系到肥皂的去污能力。实际生产中,肥皂(香皂)的配方往往是很复杂的,所用到的原料是几种甚至十几种脂肪酸的混合物,以期获得较好的去污效果与皮肤接触感受。

  “冷制皂”和工业皂有何不同

  那么,既然都经过了同样的皂化反应,手工冷制皂与工业皂区别又在哪里呢?不妨先来看一看手工冷制皂的典型制备方法[1]:先称量出一定量的基础油(即脂肪酸酯)、氢氧化钠和水;然后将氢氧化钠缓慢地溶解于水中并搅拌均匀;将基础油加热至60°C后,缓慢地倒入上述氢氧化钠水溶液中,边倒边不停搅拌,倒完之后再搅拌15-20分钟,并在整个搅拌过程中保持温度处于40-50°C之间。随后,将糊状物倒入模具中自然冷却,放置在阴凉通风处,4-6周后即可脱模使用。

  而典型的工业制造肥皂的基本过程[2],则是将脂肪酸酯、氢氧化钠水溶液加入到反应釜(就是一个很大的金属罐子),用蒸汽加热至水沸腾,并在强力的机械搅拌下反应数十分钟到一个小时,所得产物用食盐水洗涤、分层、干燥并冷却后得到皂基(即碎片状的肥皂),将皂基干燥、压片、融化后,加入香料和其他一些成分(如消毒剂、保湿剂等),再浇入模具,脱模、打磨后得到肥皂。

  两个过程相比较,不难看出,最大的差异就在于皂化反应的温度:手工皂是处于60°C以下,工业制皂则往往在90-105°C左右。温度的差异直接影响到反应速率。大多数化学反应,都是温度越高反应越快,大致来说,温度每提高10°C,则反应速率大约提高一倍。也就是说,在手工制皂的过程中,整个反应的速度是很慢的,在二三十分钟内根本无法完成皂化反应,而工业制皂过程则能确保绝大多数原料转化为产品。

  另一个影响反应速率的因素,是反应物的均匀性。不难理解,倒进烧杯里的油和水,一般是会分成上下两层的,这在化学上被称为“非均相”,如果要让这两种物质充分接触并发生反应,就需要强力的搅拌。很显然,手工制皂时用手拿着玻璃棒去搅拌,其效率远不能和工业制皂中电动机带动的机械搅拌桨相比;如果采用电钻作为搅拌器会好些,但在低温下,反应物的粘度较大(呈糊状),其搅拌效果依然没法和反应釜相提并论。

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