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About Solving The Problem Of Uniformity In The Nonwoven Fabric Process
Aug 15, 2018

Non-woven fabric refers to a fabric that is entangled with a plurality of punctured needles or partially adhered together without being woven. The nonwoven fabric is composed of oriented or random fibers. For example, polypropylene (pp material) pellets are used as raw materials, which are produced by high-temperature melting, spinning, laying, and hot-rolling. It is called cloth because it has the appearance and some properties of the cloth. However, they are made on a wet or dry paper machine including chemical fibers and plant fibers under the condition of using water or air as a suspending medium. Although it is a cloth and not a textile, it is called a nonwoven fabric.

First, the production process classification

1, spunlace non-woven fabric

The spunlace process is to spray a high-pressure fine water stream onto one or more layers of the fiber web so that the fibers are entangled with each other, so that the fiber web can be reinforced and has a certain strength.

2, heat sealing non-woven fabric

The thermally bonded non-woven fabric refers to a fibrous or powdery hot-melt adhesive reinforcing material added to the web, and the web is further fused and cooled to form a cloth.

3, pulp airlaid non-woven fabric

Airlaid nonwoven fabric can also be called dust-free paper, dry papermaking non-woven fabric. It uses the air-laid technology to open the wood pulp fiber board into a single fiber state, and then uses a gas flow method to agglomerate the fibers on the mesh curtain, and the fiber web is further reinforced into a cloth.

4, wet non-woven fabric

The wet-laid non-woven fabric is to open the fiber raw material placed in the water medium into a single fiber, and at the same time mix different fiber raw materials to form a fiber suspension slurry, and the suspended pulp is transported to a web forming mechanism, and the fiber is netted in a wet state. Reinforce into a cloth.

5, spunbond non-woven fabric

The spunbonded nonwoven fabric is formed by laminating the filaments after the polymer has been extruded and stretched to form continuous filaments, and the web is subjected to self-bonding, thermal bonding, chemical bonding or mechanical reinforcement. The web becomes a non-woven fabric.

6, meltblown non-woven fabric

The process of melt-blown non-woven fabric: polymer feeding---melt extrusion---fiber formation---fiber cooling---forming into the net---reinforcing into cloth.

7, needle punched non-woven fabric

The needle-punched nonwoven fabric is a kind of dry-laid nonwoven fabric, and the needle-punched nonwoven fabric is a puncturing effect by a lancet, and the fluffy fiber web is reinforced into a cloth.

8, stitching non-woven fabric

The stitchbonded nonwoven fabric is a kind of dry non-woven fabric, and the stitching method is a warp knitting fabric structure, a web, a yarn layer, a non-woven material (for example, a plastic sheet, a plastic thin metal foil, etc.) or a combination thereof. The body is reinforced to form a nonwoven fabric.

Its main uses can be roughly divided into:

(1) Non-woven fabrics for medical and sanitary use: surgical gowns, protective clothing, disinfecting wraps, masks, diapers, civilian rags, wipes, wet wipes, magic towels, soft towel rolls, beauty products, sanitary napkins, sanitary care Pads, disposable sanitary napkins, etc.;

(2) Non-woven fabrics for home decoration: wall coverings, tablecloths, bed sheets, bedspreads, etc.;

(3) Non-woven fabrics for clothing: lining, adhesive lining, flakes, styling cotton, various synthetic leather base fabrics, etc.;

(4) Industrial non-woven fabrics; filter materials, insulating materials, cement bags, geotextiles, coated cloths, etc.;

(5) Non-woven fabrics for agriculture: crop protection cloth, nursery cloth, irrigation cloth, heat preservation curtain, etc.;

(6) Other non-woven fabrics: space cotton, thermal insulation materials, car decoration, oil absorbing felt, smoke filter, bag, tea bag, etc.

1. The manufacturing method is roughly divided into a wet method using water (7% in Japan and 1-2% in the world) and a dry method without water (93% in Japan and 98 to 99% in the world) . Others are hot air or hot press fixing (thermal bonding, wire bonding, etc.) and methods using adhesives (chemical bonding), etc.

2, non-woven fabric has many advantages: 1) air permeability 2) filterability 3) heat preservation 4) water absorption 5) water resistance 6) stretchability 7) not unkempt 8) good hand feeling, softness 9) lightness 10) flexible , can be restored 11) no fabric directionality 12) compared with woven fabrics, high productivity, fast production speed 13) low price, mass production and so on.

3. Disadvantages are: 1) Poor strength and durability compared with woven fabrics 2) Cannot be washed like other fabrics 3) Fibers are arranged in a certain direction, so they are easily split from a right angle direction and the like. Therefore, the recent improvement in production methods has mainly focused on preventing the improvement of division.

Second, the problems encountered in the production process of non-woven fabrics

   During the production of polyester cotton, due to the problem of pre-spinning or post-spinning conditions, it is inevitable to cause some abnormal fibers, especially the recycled cotton produced by recycling slicing, which is more likely to produce abnormal fibers; the abnormal fiber outsole can be divided into the following types;

a, single thick: extended incomplete fiber, such fiber is easy to cause abnormal dyeing, less impact on non-woven fabrics, but for water-based cloth or needle cloth for artificial leather fabrics Serious impact.

b. Threading: After stretching, there are two or three fibers sticking together. This kind of fiber is easy to cause abnormal dyeing, and has less influence on non-woven fabrics, but for water-based cloth for artificial leather base fabric. Or acupuncture cloth has a serious impact.

c. Glue: Broken or entangled yarn during extension, so that the fiber does not extend completely to form hard cotton. This product can be divided into first-grade gelatinous, second-grade gelatinous, third-grade gelatinous and the like. Such abnormal fibers are often deposited on the card clothing after the carding process, causing problems such as poor formation of the cotton web or broken net. Such raw materials may cause serious quality defects for most of the non-woven fabrics.

d. Oil-free cotton: During the extension period, there is no oil on the fiber during the driving condition. This fiber usually has a dry feel. In addition to causing static electricity generated in the non-woven fabric production process, it also causes problems in finishing the semi-finished product. .

e. The above four kinds of abnormal fibers, single root and merging are difficult to remove during the production of non-woven fabrics. Colloidal and non-oiled cotton can be removed as long as the production personnel pays little attention to reduce the defects of product quality.

    The reasons for the uneven thickness of the nonwoven fabric under the same processing conditions may be as follows:

a. Low-melting fiber and conventional fiber blending are uneven: different fibers have different cohesion. Generally speaking, low-melting fibers have greater cohesion than conventional fibers and are less likely to disperse. If the low-melting-point fibers are unevenly dispersed, the portion having a low content of the low-melting-point fibers cannot form a sufficient network structure, and the nonwoven fabric is relatively thin, and a relatively thick phenomenon is formed in a place where the content of the low-melting-point fibers is large.

b. Incomplete melting of low-melting fiber: Incomplete melting of low-melting fiber, the main reason is insufficient temperature. For non-woven fabrics with low basis weight, it is usually not easy to produce insufficient temperature, but for high basis weight, high thickness The product needs to pay special attention to whether it is enough. The non-woven fabric at the edge has a thick heat, and the non-woven fabric is usually thick. The non-woven fabric in the middle portion is less likely to form a thinner non-woven fabric because of the heat.

c. High shrinkage of fiber: Whether it is a conventional fiber or a low-melting fiber, if the hot air shrinkage rate of the fiber is high, the problem of uneven thickness is likely to occur due to the shrinkage problem during the production of the nonwoven fabric.

 Third, about autoleveling

In summary, in the production process of non-woven fabrics, how to make the non-woven fabrics become thicker and more uniform, and the weight is consistent, which has become the primary problem faced by many manufacturers. The factors that remove the difference between the equipment itself and the raw materials, a device that is automatically adjusted to achieve uniformity of the nonwoven fabric through human participation, has been successfully launched, and plays a vital role in some non-woven fabric production lines!

  Here are two sets of Wuxi Plett ZNS intelligent non-woven auto-leveling instrument purchased by our company to talk about the experience.

1. Structure: ZNS carding machine self-adjusting leveling instrument, using high-life dedicated PLC as control center, with French-controlled Schneider frequency conversion as vector drive mechanism, and high-precision German brand sensor and controller to ensure reliable system. The operation, external man-machine dialogue touch screen, online working status.

The system can be divided into three parts: the inspection display and control center, the execution drive, and the sampling system.

2, the working principle: the entire carding machine autoleveling system using computer control technology, using the current advanced data acquisition and communication functions, can easily change the setting input. The external input is sampled immediately after a few seconds of self-test after turning the power on. The thickness of the cotton layer is applied to the left and right sensors by feeding the cotton roller pressing arm, and the sensor is fed back to the control center by detecting the volume of the roller cotton layer per unit time, and the control center issues a command to the execution driving device, thereby Control the unevenness and deviation of the surface layer to achieve the same weight. (See the figure) Solve the hysteresis and error phenomenon of electronic weighing autoleveling, and adopt a more scientific and sensitive volume detection method.

3, the customer requirements are strict, the use of the original non-woven equipment weight control is poor, can not meet customer requirements. After a number of comparisons, Wuxi City Plett electromechanical ZNS carding machine auto-leveling instrument was selected and modified in the original carding machine feeding part. The instrument comes with a reverse function and an emergency stop function.

From this calculation: after using the autoleveling instrument, the deviation of the weight per square meter is within plus or minus 2 grams, and the error rate is within 4%. Not only meets the customer's requirements, but also adds the edge material, still does not affect the quality. This saves the raw material and electricity consumption while controlling the weight. The effect of improving the quality is more obvious.

Conclusion: ZNS carding machine self-adjusting device is compact in structure, simple in installation, economical and practical, and it is a solution to solve the problem of thick and thin and cumbersome troubles under the existing non-woven process conditions and improve the quality. The use of ZNS carding machine for autoleveling eliminates the transformation of the process gear, which facilitates the process of the machine, and saves the loss of raw materials and improves the production efficiency to a greater extent.

Hangzhou Hanford Technology Co., Ltd.

Address:Xinjie Industry Zone, Xiaoshan, Hangzhou, Zhejiang, China