How to do melt blown machine commission and adjustment for producing good non wolven fabric for mask.
With the outbreak of the epidemic COVID-19 and the BLOOMING of the mask industry, the melt blown not woven fabric has become the most popular material, and countless bosses have lined up to rob the melt blown machine and adjust the equipment. Ater great money invested, time comsumed, but some machine still can’t adjust well for good non woven fabirc. Some machine can’t even spray a cloth. If you don’t give a good fabric, you’ll lose all your money. We produce modified melt blown materials. We have seen many machines and helped our customers deal with the problems of machines of various sizes. In recent months, we have become a shunting master, and we have dry goods on the bottom.
Melt blown material and machine commissioning.
There are two main reasons for the problem of the melt blown:
1、Melt blown Equipment problems
The design principle and structure of the equipment are not complicated, but the maturity of all the equipment is from raw to mature, and the experts are also from rookie. Although many equipment manufacturers used to make plastic machines, they didn’t make meltblown machines. So the equipment and machines you buy are actually the first generation products of others. Frankly speaking, most people buy 40, 50, 60 and 65 small earth cannons at present, and more than 80 machines are better. A good machine, the difference between a good machine and a bad one is not the function, but the details, the factory experience and production experience!! ……
In fact, melt blown nonwovens technology is very simple. The polymer melt extruded by screw extruder is blown by high-speed hot air to make the melt flow be extremely stretched to form microfiber. These microfiber condenses on the screen or roller to form the fiber net, and then becomes nonwovens by self adhesion.
The technological process is: PP material feeding → melt extrusion → fiber formation → fiber cooling → fabric formation → bonding and reinforcement → edge cutting and winding → finished product. The melt blown equipment is divided into horizontal type and vertical type according to the placement mode
The following is the machine design found on the invention patent cn 105568560. Each boss takes his seat according to the invention patent and compares his own equipment! Now, of course, there are better designs than this patent. Skip.
Machine design schematic
1. Screw extruder 2. Filter 3. Pipeline 4. Metering pump 5. Die 6. High speed hot air 7. Side blowing 8. Forming table net (with electrostatic aid) 9. Front overflow fan 10. Suction fan 11. Rear overflow fan
Does your machine have the above configuration? If you don’t, You can only make up by choosing a good material. The simple way is to find the melt blown materials with special compound formula
Can 95+ level melt blown non woven be produced with the above configuration? If your answer is “yes’, what you think is too simple. Melt blown nonwovens is a non-stationary spinning process, which will be affected by many factors. In the actual production process, it is difficult to achieve the precise control of the melt blown process, and many key technologies have not been fully mastered and disclosed, so the quality of the melt blown products often has problems.
During the machine commissioning and actual debugging process, we found the following common problems:
a. The operator don’t know the characteristics of the own machine
Novice boss does not understand that different machines have different screw length diameter ratio and screw angle, so different machines will have many differences in the heating range of the same raw material. The heating temperature of different working areas is also different (if we add the variable of different raw materials, it will be more troublesome). Adjust the machine blindly according to other people’s experience without any adjustment.
B. The temperature of the machine cannot be controlled
Some machines have inaccurate temperature control, high and low. If the actual temperature of your machine is jumping above 5 degrees, the possibility of good melt blown fabic is extremely low. Of course, the more stable the temperature control, the better for production. Some small machines do not have thermocouples on the spinneret mold/die. The actual temperature of the die can only be guessed. When the die temperature is low, the die will be blocked.
Pay attention to keep the temperature in the workshop relatively stable, high room temperature and unstable room temperature are not conducive to production.
C. Spray dide/mold is poor.
The importance of spinneret to the production line of melt blown cloth is very very very inportant. Many bosses said that I bought this die head at a high price. That is no problem. If there is any problem, just look at the magnifying glass and speak with facts.
Die spinneret
It is claimed that there are many die heads with 0.25 hole diameter and 0.6 hole spacing, but we have to see for real. If possible, get a high-power microscope and look at your spray die/mold head. If your head is under the microscope. The fine hole is smooth and the distance between holes is equal, and the nozzle is polished, so as to ensure that the cloth is fine and even. Most of the small machines that can’t spray out good fabric use waste die heads, with uneven aperture and rough bristle. In addition, we need to pay attention to the design of feeding mode. Most of the die/mold heads bought are generally one or back type uniform flow pipes, which are cheaper but prone to uneven distribution. The spray die/mold head adopts the design of hot runner, which is divided by different paths. This mode can make the feeding pressure more balanced. At the same time, the hot runner plate plus the heating rod can not only keep the temperature of raw materials in a stable state, but also monitor the documents of the nozzle in real time. It can avoid the cumulative plugging problem caused by temperature imbalance in the process of wire injection.
2、 Problems with melt blown PP raw materials:
From the point of view of the manufacturing principle of cloth: the way of melt blown is to form superfine fibers, which can agglomerate on the web curtain or roller to form fiber mesh, and then become nonwovens by self adhesion. In order to form superfine fiber easily, PP material with high fluidity is needed. Other factors remain unchanged. The higher the fusible quality, the finer the ejected wire, and the easier it is to eject products with high filtration level. The higher the fusibility is, the better the cloth is ejected.
At present, there are many PP modified materials. At present, regardless of the size of the modification plant, the melt quality of PP material is 1500. But this is only one of the indicators. The flexibility and processing versatility of the materials are not included in the indicators. And I can only try it myself. Many manufacturers do not know the adjustment data of their own melt blown materials on different machines.
Our team summerized some common problems in helping customers solve problems:
1. the same material was OK for melt blown, but it cannot be sprayed againt after few days
Some materials become low in melting quality after being placed for a few days. We have seen that the melting quality of many products is about 1500 before leaving the factory, and 1000 after arriving at the customer’s factory a few days later. This will cause that the starting materials are still in good use. In a few days, the machine will not be able to spray cloth. The processing temperature of different fusible materials is different. This is caused by improper processing technology in the production and processing of melt blown materials. The stability of the material is very important.
2. The toughness quality of the cloth is not good, it is brittle and easy to break
This is the problem most people encounter at present. Considering that the melt quality of the material is 1500, it is normal that the sprayed cloth is brittle and easy to break. Therefore, it is necessary to have relevant ingredients in the production formula of melt blown materials, and use different proportions to solve this problem. In addition, some materials must be added in the production stage, and problems such as uneven processing and plug are often encountered when they are added in the later stage. The problem of poor resilience is so common that I can help you solve it. Compound formula, imported ingredients.
3. The sprayed non woven fabric has peculiar smell
The complexity is that the VOC of the cloth is not up to the standard. In short, the non woven fabric has smell. Although the filter grade of thefabric may be up to the standard, it has peculiar smell, which is harmful to human body. This is mainly due to the problems of the ingredients used in the modification process, especially the use of some small factory produced initiators. Part of the reason is that there is no vacuum filtration or insufficient filtration.
4. Using non melt blown material
Many small factories use non melt blown material to do non woven at the beginning, such as SECCO 2040. This filtering level is not up to standard. And it can’t be used in medical products.
5. The meltblown materials in large factories can’t produce good fabric
In other words, your machine doesn’t “eat” this material. After the material production test is finalized, the formula ratio will not be changed. It has its processing range, but your machine can find it very well. In the face of this problem, either to change the machine, or to add ingredients in the melt spraying, both of which have to be constantly tested. The best thing is to refuel decisively
On the premise that there is no problem with the machine and materials, it is the transfer of the machine. Adjusting the machine is to find the most suitable processing tempreture range between the melt blown material and the machine. Without good skill in the machine is commissioning, no matter how good the material it’s useless. Here are some aspects to be adjusted:
A、 Receiving distance
The receiving distance from the outlet of the die/mold head spinneret to the receiving conveyor or round roller was called the receiving distance of the melt blown process. When the receiving distance decreases, the fiber size decreases obviously; when the receiving distance decreases to a certain extent, the fiber size decreases slowly; when the receiving distance is too small, the fiber size increases again. This is because the stretch thinning area of the melt blown fiber under the action of hot air mainly occurs in the short distance from the spinneret hole. The fiber size has a significant impact on the tensile property. The fiber is thin and has many winding nodes. The force on the fiber is uniform and the strength increases, but when it reaches a certain degree, the stretch property will decline. The receiving distance also affects the fluffy degree of the melt blown fiber mesh and the degree of adhesion between the fibers.
In general, the decrease of receiving distance, the insufficient cooling and diffusion of hot air flow, the strong thermal bonding effect between fibers lead to the decrease of product fluidness, the increase of fiber mesh volume density and the decrease of product elongation. When the receiving distance increases, the fluffy property of the fiber increases, and the fiber size increases. At the same time, the porosity of the product increases, the filtration efficiency decreases, the resistance decreases, and the elongation of the product also increases. When the receiving distance is too small, the fibers in the fiber mesh will be curly and agglomerated together, and the product’s fluffy degree will be reduced, which will affect the air absorption efficiency of the mesh bottom, and there will be “flying flower” defects; in serious cases, the fibers are not completely cooled, which will cause ice wire.
B. Hot air speed and temperature
Under the same process conditions, the fiber size will decrease with the increase of hot air speed. This is due to the increase of hot air speed and the increase of its tractive force on the fibers ejected from the spinneret hole, so the fiber size becomes smaller; however, when the air pressure reaches a certain value, the decrease of the fiber size will gradually slow down, and the fiber size CV value will decrease accordingly. This is due to the increase of the hot air flow per unit time, the increase of the tensile force on the fiber, and the full tensile effect on the fiber, so all the fiber sizes are decreasing, and the size CV value will naturally decrease.
The performance of melt blown nonwovens is that the hand feel changes from hard to soft, the fiber tangles increase, and the thermal bonding effect increases, the fabric surface changes from rough to dense and smooth, the tensile breaking strength increases with it, but the tensile breaking elongation decreases because the fiber node slip path increases; when the hot air speed is too high, it will appear “Flying flower” defect, tensile breaking strength will also be reduced. Under the same process conditions, with the increase of hot air temperature, the fiber size will become smaller, and the size CV value will also decrease; when the hot air temperature rises to a certain range, the fiber size changes slowly, and the size CV value will obviously decrease; when the temperature continues to rise, the fiber size will obviously decrease.
This is because in the spinning process, the hot air draft the fiber, the temperature rise can delay the cooling and curing of the fiber, the draft function is enhanced, the fiber size and CV value are reduced, the tensile breaking strength of the melt blown material is increased, and the tensile breaking elongation is reduced. Reducing the hot air speed or temperature will increase the size of melt blown fiber, increase the porosity, reduce the resistance and decrease the filtration efficiency; increasing the hot air speed or temperature will reduce the size of melt blown fiber, reduce the porosity, improve the catching ability of the fiber net, increase the filtration efficiency, but decrease the filtration resistance.
C. The machine Working area temperature
Temperature is one of the important parameters of polymer processing technology, which has an important influence on the rheological behavior of polymer . Fhopepack team Pointed out that when the melt is extruded from the spinneret hole, the extrusion swell occurs at the outlet of the spinneret hole due to its viscoelasticity, resulting in the increase of fiber size; and the increase of processing temperature will reduce the extrusion swell ratio, thus reducing the fiber size. This is because the viscoelasticity of the polymer itself affects the extrusion swell ratio. The higher the temperature is, the stronger the running ability of the polymer molecular chain is. The viscosity dissipation of the deformation energy stored in the melt in the flow increases, resulting in the weakening of the elastic properties. Therefore, the extrusion swell ratio decreases, and the fiber size decreases.
On the other hand, in the process of melt blown spinning, the temperature of the fiber in the molten state is gradually decreased by the action of the outside air, and the increase of the temperature is conducive to prolonging the time of the fiber in the molten state, making more fibers stretch by the high-speed hot air, thus reducing the fiber size. Therefore, on the premise that the melt blown raw material does not degrade excessively, the temperature of die head and other areas can be properly increased to make the fiber thin, so as to improve the tensile breaking strength and filtration efficiency of the melt blown product, but also reduce the resistance; with the increase of temperature, the fracture elongation rate of the melt blown product will be reduced. When the temperature of each working area is too high, “flying flower” defect will be formed due to too many broken fibers.
D. Net bottom suction
After being drawn by high-speed hot air, the melt blown fiber is laid on the receiver (net curtain) to form a fiber net, and the remaining high-speed hot air needs to be absorbed under the receiver (net curtain) smoothly, otherwise, the fiber cannot be fully absorbed on the net curtain, and it will appear defects such as “flying flowers”, thin net, turning over net, etc. In order to absorb the remaining high-speed hot air smoothly, a net bottom suction device needs to be installed under the receiver (net curtain). The size of air suction at the bottom of the mesh is very important for the quality of forming the melt blown fiber mesh. Especially when producing the melt blown material with large area density, increasing the air suction at the bottom of the mesh will effectively improve the tensile strength and elongation at break of the product, making the melt blown fiber mesh from fluffy to dense, porosity smaller, filtration resistance reduced, and filtration efficiency increased.
The following is a summary of the combined methods to improve the performance of the melt blown cloth in the commission:
In the production of melt blown products, the methods that can not only reduce the filtration resistance, but also improve the filtration efficiency are as follows: when the receiving distance increases, increase the hot air speed or temperature appropriately, and reduce the suction at the bottom of the mesh, the fiber size will be smaller, and the product will be more fluffy. When the spinning environment temperature is too high and the melt index of raw material is too high, the elongation can be increased, Reduce the hot air flow or temperature properly, reduce the receiving distance, and slightly increase the suction at the bottom of the mesh; or when the spinning environment temperature is too low and the melting index of raw materials is too low, increase the hot air flow or temperature appropriately, increase the receiving distance, and slightly reduce the suction at the bottom of the mesh.
There are also related mechanisms to test the fiber fineness, mechanical properties, air permeability, filtration efficiency and hydrophilicity of the melt blown nonwovens, and analyze the influence of hot air temperature, pressure, receiving distance and other melt blown process parameters on the product performance. The results show that the fiber diameter increases with the hot air temperature, It decreases first and then increases; it decreases with the increase of hot air pressure; its strength increases with the increase of hot air pressure and decreases with the increase of receiving distance; its permeability increases with the increase of hot air temperature, its filtration efficiency increases with the increase of hot air pressure and its liquid absorption rate increases with the increase of receiving distance
Anyone want to have a good melt blown non woven, please do it according to the above information i commissioning. Of course, the problems are far more than those mentioned above. If you have any problems with the machine and materials, you can find us and our team will help to resolve your problem.
Use our materials info@fhopepack.com www.fhopepack.com
Following is the non woven roll packing machine.
Non woven fabric roll packing machine
The article resource is from https://www.fhopepack.com
