Free Talk: Common problems and solutions in the production of soft foam
Common problems and solutions in the production of soft foam
The amount of accidents and problems encountered in the actual production of foam is diverse, and each accident is caused by a variety of factors in the production. In the analysis of accidents caused by complex factors, it is generally difficult to list all the influencing factors and the main factors that really play a role.
A summary of some of the frequently encountered accidents and their causes are as follows.
1, scorched heart (reaction center temperature exceeds the raw material antioxidant temperature)
(1) polyether polyol quality problems: production storage and transportation process so that the product in the water exceeds the standard, peroxide, low boiling point impurity content is too high, metal ion concentration is too high, with the type and concentration of antioxidants improper.
(2) formula: low density formula, TDI index is too high, improper ratio of water to physical blowing agent in the blowing agent, low amount of physical blowing agent, excess water.
(3) climatic influence: high temperature in summer, slow heat dissipation, high material temperature, high air humidity, the reaction center temperature exceeds the antioxidant temperature.
(4) improper storage: when the TDI index rises, the heat energy of the pile increases during post-ripening causing the internal temperature to rise and scorch.
2、Large compression deformation
(1) polyether polyol: the functional degree is less than 2.5, the proportion of ethylene oxide is more than 8%, there are many small molecule components, and the unsaturation is more than 0.05 mol picture.
(2) process conditions: the temperature of the reaction center is too low or too high, the post-ripening is not good, not fully reacted or partially scorched.
(3) process formula: TDI index is too low, silicone oil stannous octanoate is too much, foam aeration is low, and closed pore rate is high.
3、The foam is too soft (hardness decreases under the same density)
(1) polyether polyol: low functional degree, low hydroxyl value, large relative molecular mass.
(2) process formula: low amount of tin octanoate, slow gel reaction speed, less water in the same amount of tin, more physical foaming agent, high silicone oil activity, high dosage, low TDI index.
4、Bubble hole coarse
(1) bad mixing; uneven mixing, short emulsion period.
(2) process formula: silicone oil dosage below the lower limit, low dosage of stannous octanoate and poor activity, slow gel speed.
5, higher than the set density
(1) polyether polyol: low activity, large relative molecular mass.
(2) Process formula: silicone oil dosage below the lower limit, low TDI index and low foaming index.
(3) climatic conditions: low temperature, high air pressure.
6、Collapsing bubble hole (the speed of gas generation is greater than the gel speed)
(1) polyether polyol: acid value seriously exceeds the standard, many impurities, low activity, large relative molecular weight.
(2) process formula: amine dosage more tin dosage less, TDI index low, in the same tin dosage TDI index is too high, the gas speed is greater than the gel speed, the skeleton strength is small and collapse bubbles or local holes.
II.
1、High closed pore rate
(1) polyether polyol: high proportion of ethylene oxide, high activity, mostly occurring in the replacement of polyether polyol with different activity;
(2) process formula: more amount of stannous octanoate, high activity of isocyanate, large cross-linking degree, fast cross-linking speed, too much amine and physical blowing agent cause low internal pressure of foam, foam elasticity can not be opened when the TDI index is too large will also lead to high closed porosity.
2、Shrinkage (gel speed is greater than the speed of foaming)
(1) High closed porosity: shrinkage during cooling.
(2) process conditions: low temperature, low material temperature.
(3) process formula: excessive silicone oil, excessive physical foaming agent, TDI index is too low.
3、Inside crack
(1) Process conditions: low temperature, high temperature of reaction center.
(2) process formula: low TDI index, more tin, high early foaming strength.
(3) high activity of silicone oil: less dosage.
4, top crack (hair aerogel speed imbalance)
(1) process conditions: low temperature, low material temperature.
(2) process formula: insufficient amount of catalyst, low amount of amine, bad quality of silicone oil.
5, bottom corner crack (too much amine dosage, foaming speed is too fast)
Surface macropore: excessive amount of physical foaming agent, poor quality of silicone oil and catalyst.
6, poor low temperature performance of foam: poor intrinsic quality of polyether polyol, in the same hydroxyl value, low functionality, unsaturation, the same amount of tin, TDI index is low.
7、Poor aeration
(1) climatic conditions: low temperature
(2) raw materials: high polyether polyol, high silicone oil activity
(3) process formula: more tin, or the same amount of tin when the water and amine content is less, TDI index is high.
8, poor inverse elasticity
(1) raw materials: high activity of polyether polyol, small relative molecular mass, high activity of silicone oil.
(2) process formula: large amount of silicone oil, more tin, more water in the same amount of tin, high TDI index.
Three
1, poor tensile strength: n52Q-6H
(1) raw materials: too much low-molecular polyether polyol, with low hydroxyl value functionalities.
(2) process formula: less tin gel reaction is not good, in the same amount of tin, TDI index is high, less water cross-linking degree is low.
2, smoke when foaming: excess amine prompted by water and TDI reaction gives off a lot of heat, low boiling point material evaporation and smoke. If not scorched heart, the smoke is mostly composed of TDI; low boiling point substances and monomeric naphthenes in polyether polyol.
3, foam with white tendons: foam and gel reaction speed, slow transfer speed in continuous foaming, local extrusion and generation of dense layer, resulting in the phenomenon of white tendons. Should be timely to improve the transfer speed, or reduce the material temperature, reduce the amount of catalyst.
a
4、Foam crisp: more water in the formula, generate more diurea has not been dissolved in silicone oil, tin catalyst with poor, cross-linking reaction is not sufficient, small relative molecular mass polyether polyol content, reaction temperature is too high, ether bond breakage reduces the foam strength.
5、Foam density is lower than the set value: foam index is too large due to inaccurate measurement, high temperature and low gas pressure.
6、Foam has bottom skin, side skin, bottom step cavitation: tin more amine less, slow foaming speed, fast gel speed, in continuous foaming with temperature too low.
7、Large elongation rate
(1) raw materials: polyether polyol with high activity and small functionalities.
(2) process formula: low TDI index cross-linking deficiency, more tin, more silicone oil.
(3)High temperature
