The coagulant dipping process of nitrile latex: investigations of former motion effects and coagulant loss into the dipping compound.
The coagulant dipping process of nitrile latex: investigations of former motion effects and coagulant loss into the dipping compound.
复制标题
丁腈乳胶的凝固剂浸渍过程：研究浸渍剂中的运动效果和凝固剂损失。
作者：
Groves R
凝固剂浸渍是薄手套制造中使用的工艺，涉及电解质离子从手形模型的表面扩散到乳胶化合物中，导致存款（湿凝胶）在模型上积累。在这项工作中，两个方面的过程进行了研究，实验和理论。对于实验工作，使用商业丁腈胶乳。通过胶乳浸渍槽的成型器的运动直观地预期影响电解质扩散，从而影响湿凝胶生长。这是在实验室规模的研究与小玻璃成型移动在一米长的浸槽。以前的速度范围从零到几乎0.2 m s-1。没有观察到前侧向移动对湿凝胶厚度的影响。一个明显的解释是，大部分凝结剂扩散发生在湿凝胶存款内，这为扩散通量提供了保护。然而，临界区正好在凝结前沿的前面，其中凝结剂以低于凝结所需水平的浓度存在于液体化合物中。建立了一个流体力学模型，该模型假定流体沿矩形成形器的侧面沿着均匀流动。该模型证实，对于最常用的混凝剂硝酸钙，运动的影响很小。在第二项研究中，通过在重复静态浸渍期间取样，研究了在停留时间期间凝结剂泄漏到主体胶乳化合物中的情况。使用扩散理论对该实验进行建模，重点是在前提取点处湿凝胶外部的临界区。模型和实验一致，都显示了一个小的，但明确的凝结剂泄漏，趋于一个平台浓度。从理论的角度来看，也被认为是从一个移动的前混凝剂泄漏。在这种情况下，机理是凝结剂从临界区平流运动到主体化合物中。在最坏的情况下，所有这些凝结剂都被冲走，该模型表明，平台凝结剂浓度可能达到会导致凝结的量。临界区（边界层）中的流量减少和前形状是减少泄漏的因素。
Coagulant dipping, the process used in thin glove manufacture, involves electrolyte ions diffusing from the surface of a hand-shaped former into latex compound, causing a deposit (wet gel) to accumulate on the former. In this work, two aspects of the process were examined, both experimentally and theoretically. For the experimental work, a commercial nitrile latex was used. The motion of formers through a latex dipping tank is intuitively expected to affect the electrolyte diffusion and hence the wet gel growth. This was investigated at laboratory scale with small glass formers moving in a metre-long dip tank. Former velocities ranged from zero to almost 0.2 m s−1. No effect of former lateral movement on wet gel thickness was observed. One obvious explanation is that most of the coagulant diffusion occurs within the wet gel deposit, which provides protection to the diffusive flux. However, the critical zone is just ahead of the coagulating front, where coagulant is present in the liquid compound at concentrations below the level needed for coagulation. A fluid mechanical model was constructed that assumed a uniform fluid flow along the side face of a rectangular former. The model confirmed that for calcium nitrate, the most commonly used coagulant, the effect of movement is very small. In the second investigation, coagulant leakage into the host latex compound during the dwell time was investigated by taking samples during repeat static dips. This experiment was modelled using diffusion theory, focusing on the critical zone just outside the wet gel at the point of former withdrawal. The model and experiment agreed well, both showing a small but definite coagulant leakage that tended towards a plateau concentration. Coagulant leakage from a moving former was also considered, from a theoretical perspective. In this case, the mechanism is advective movement of coagulant from the critical zone into the host compound. In the worst case, where all of this coagulant is swept away, the model suggested that the plateau coagulant concentration could reach an amount that would cause coagulation. Reduced flow in the critical zone (boundary layer) and former shape are factors that would reduce leakage.