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如何解决水性双组分拼板胶的发泡问题？

字体: 小中大 | 打印发表于: 2008-9-13 11:13 作者: jsj125 来源: weldon胶粘在线

用过市场上很多种类的拼板胶，但发泡都很厉害。有的不到20分钟就起泡非常厉害，但是粘度并不是很大，机器涂胶问题不太大，但手工涂胶就很困难了。

之前也看过一些进口的拼板胶几乎不发泡，但价格比较贵。

究竟是什么原因？不知道有什么办法可以解决？望各位专家指教

我也来说两句查看全部回复

最新回复

fghgaoan (2008-9-16 20:02:07)

手动涂胶的话那就需要现配现用，一次不要配多了！

几乎不发泡的胶活性期相对也并不长，没有很多优势的。
auidlangsyne (2008-9-16 21:30:43)

一减少丙烯酸二减少羟基但强度又会略低
admin (2008-9-16 22:17:50)

QUOTE:
原帖由 auidlangsyne 于 2008-9-16 21:30 发表
一减少丙烯酸二减少羟基但强度又会略低
不赞同楼上的观点
wang (2008-9-17 08:36:39)

用VAE乳液做的拼板胶很少起泡。
jsj125 (2008-9-17 11:51:41)

QUOTE:
原帖由 wang 于 2008-9-17 08:36 发表
用VAE乳液做的拼板胶很少起泡。
成本也会高不少吧？
luyan3311 (2008-9-17 21:10:25)

这种情况我也遇到过，用了点消泡剂，但是几乎不起作用，发泡其实就是不好看而已，对性能好像没有什么影响。
uljzy (2008-9-17 23:31:49)

用VAE乳液做的拼板胶很少起泡。-------------我就是用VAE做的，起泡也很厉害。VAE50%左右，还有就是PVA了。是配方的问题么？
jsj125 (2008-9-18 09:16:27)

QUOTE:
原帖由 luyan3311 于 2008-9-17 21:10 发表
这种情况我也遇到过，用了点消泡剂，但是几乎不起作用，发泡其实就是不好看而已，对性能好像没有什么影响。
干性强度问题不大，但是我发现发泡厉害的胶水对耐水性有影响
admin (2008-9-18 11:05:11)

减小发泡量就要想办法避免NCO与水的反应的量。好像有3种途径：
1.加溶剂（二甲苯、甲苯等）或增塑剂（二丁酯、二辛酯等）到固化剂中，隔离异氰酸酯和水，这样就能降低发泡量，大幅度提高耐水性。

2.加能与水反应的物质，如苯甲酰氯等，这样能消耗部分水，降低发泡量。

3.控制体系的ph值，NCO与水在碱性环境下反应很快，酸性环境下反应慢

我自己做拼板胶没有用上面的改进方法，因为客户没有反应发泡量过大的情况。
只是有一次用四川的丙稀酸改性eva来做的时候，发泡量非常大，换回原来的牌号就好了
jsj125 (2008-9-18 13:14:52)

QUOTE:
原帖由 admin 于 2008-9-18 11:05 发表
减小发泡量就要想办法避免NCO与水的反应的量。好像有3种途径：
1.加溶剂（二甲苯、甲苯等）或增塑剂（二丁酯、二辛酯等）到固化剂中，隔离异氰酸酯和水，这样就能降低发泡量，大幅度提高耐水性。

2.加能与水反应 ...
很感谢，非常专业有几个疑问还想继续探讨一下：
1. 加溶剂未必可行，现在拼板胶都要求达到GB18583要求，加人甲苯或二甲苯可能满足不了。增塑剂觉得可以试试
2. 把水反应掉会不会引起粘度上升太快，化学方面我不太了解只是有这个担心
3. 改变pH可能会有帮助
luyan3311 (2008-9-18 20:55:00)

水性双主份胶的成本较高，它的优势就是不含甲醛和苯，二甲苯等VOC，如果加了溶剂就没有这种优势了，就算加了之后不起泡了，我个人觉得也没有什么意义了。
fghgaoan (2008-9-26 17:04:22)

看看下面这篇东西，其实我觉得发泡多少其实没有很大的意义，发泡少的活性期也并不长。

Reducing Undesirable Foaming in a Water-Based Polymer-Isocyanate Adhesive forWood

Japanese Industrial Standards (JIS) defines water-based polymer-isocyanate adhesives for wood as two component systems of a waterbased glue and an isocyanate (NCO) crosslinker. Generally in commercial products, the water-based glue is a mixture of poly vinyl alcohol (PVA) solution, emulsions of styrene-butadiene-co-polymer (SBR) and ethylene-vinylacetate-co-polymer (EVA), and calcium carbonate; the crosslinker is a crude of polymeric methylene bis (phenyl isocyanate) (pMDI). It is known that EVA is more effective than SBR for improving initial bond strengths; however, the addition of EVA sometimes causes undesirable foaming during mixing of the NCO crosslinker with the water-based glue. This foaming results from a release of carbon dioxide from the reaction between NCO groups and water. In this study, we aimed to decrease the gas emission by examining two factors of the constituents: the particle diameter of calcium carbonate and the E/VA molar composition of EVA. Water-based glue used in this study was prepared by mixing 25 parts of PVA 15% solution, 45 parts of EVA emulsion, and 30 parts of calcium carbonate, where three of calcium carbonates with different diameter and three of EVA emulsions were examined. EVA emulsions were different in their ethylene / vinylacetate molar composition, though equal in other properties such as solid content (c.a. 50%), viscosity, pH (at neutral), and both amount and chemical of surfactant; they were specially prepared by Denki Kagaku Kogyo (JAPAN). The NCO crosslinker was a commercial pMDI. The base glue and the crosslinker were mixed in the weight ratio of 100 / 15 by an agitator for 3 min., and cast onto a Teflon sheet. This sheet was immediately placed in a sealed container connected to a gas burette charged with copper sulfate solution.Arising gas from the adhesive was measured by the volume of gas collected into the burette. The film with commercial EVA released about 20 times as much gas as that with commercial SBR: this provides evidence for the undesirable foaming of the adhesive with EVA. All the samples emitted most of their gas within 3 hours, after 24 hours they stopped emitting gas. The volume of emitted gas decreased with an increase of vinylacetate (VA) molar ratio of EVA. It is considered that high VA ratio EVA has an effect on delaying the reaction of NCO in this adhesive system. This was confirmed by FT-IR measurement. As a function of the particle diameter of calcium carbonate, its small diameter resulted in less gas emission and in more unreacted NCO.