JPS6240051B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the improvement of filter materials such as dust masks, and an object of the present invention is to provide filter materials such as dust masks that use inexpensive nonwoven fabrics made of polypropylene and rayon, have low ventilation resistance, and have extremely high dust collection efficiency. . Traditionally, filter materials such as dust masks are made of expensive wool felt, or a felt material made mostly of wool and mixed with a small amount of synthetic fibers such as polyester or polypropylene, and then coated with phenol resin or styrene resin. After coating or impregnating with a solution dissolved using an organic solvent such as benzene, the excess liquid is squeezed out and a so-called resin processing is applied, which is a process of heating and drying at around 80°C to impart an electrostatic effect. It is a known fact that the method is commonly employed. To be more specific, wool or wool-based felts are used as base materials, and as they are simply a physical overeffect and are difficult to completely capture fine dust, these base materials are Resin processing is applied to give it an electrostatic effect, but organic solvent-based resin liquids tend to adhere to the wool base material, and the wool itself has a large electrostatic effect. Synthetic fibers such as polyester and polypropylene have the advantage of being extremely inexpensive compared to wool, but on the other hand, their smooth surfaces make it difficult to create an electrostatic effect. The drawback is that the resin is difficult to adhere to, and therefore the collection efficiency of fine dust is low. JIS special grade collection is required at work sites where large amounts of metal oxide-based fine dust are generated, such as welding work. In order to achieve an efficiency of 99.5% or higher, conventional methods have had to rely on wool-based felt, which poses major obstacles in terms of material supply and economics. In response to the current situation, the present inventors have previously filed a patent application.
No. 52-34997 ``Method for processing filter materials for dust masks, etc.'' and Japanese Patent Application No. 142798/1982 ``Tanning processing device for filter materials for dust masks, etc.'' After the material is impregnated with resin and dried by known means, it is subsequently mechanically bent, stretched, loosened by hand, or tanned by similar physical means. We have proposed a method and device that can improve the collection efficiency compared to conventional methods that only involve resin impregnation and drying, but this method is particularly suitable for filter materials such as dust masks used in welding departments, which falls under the JIS special grade. A collection efficiency of 99.5% or more is required, and the frequency of use is at least 1 per day.
However, depending on the work environment, it may be necessary to replace as many as two to three filters a day, and there has been a strong desire for a cheaper, higher-performance filter. The present invention was completed as a result of various research in response to such demands, and has polypropylene fibers of 50 to 90%.
%, a nonwoven fabric made of 50 to 10% rayon fiber is impregnated with an emulsified dispersion of a resin liquid whose main component is vinyl acetate, acrylic acid, or acrylic-styrene copolymer, and then squeezed with a squeezing roll. Squeeze out excess liquid and pre-dry at 50-60℃.
Furthermore, after heating and drying at a temperature of about 100°C, the nonwoven fabric is subjected to a processing process in which the steps of bending, stretching, and beating occur at the same time. The feature is that it greatly enhances the electrostatic effect and greatly improves the dust collection efficiency. [Example 1] A nonwoven fabric made of acrylic fiber was used as the base material.
The nonwoven fabric as a base material is immersed in a mixture of 3 parts of vinyl acetate resin, 1 part of surfactant, 0.5 parts of curing accelerator, and the balance is water, in which the vinyl acetate resin is emulsified and dispersed to fully impregnate it, and then squeezed. Squeeze out excess liquid with a roll, pre-dry at 50-60℃, and then dry for another 100℃.
It was heated and dried in a constant temperature bath at ℃. Continue to make 15 rolls of 10mm diameter from this part.
A total of 10 pieces of tanning equipment installed at mm intervals (distance from the center of the roll to the center) were passed 10 times, and some of them were left as they were without passing through the tanning equipment, and both were collected under the following conditions. The results of measuring and comparing efficiency are shown in Table 1. Measurement conditions Dust type: Welding dust Dust concentration: 50 ± 10 mg/m3 Suction speed: 30 m3/min Measuring device: Piezoelectric crystal vibration type dust meter

[Example 2]

According to Example 1, the thickness of the base material was about 3 mm,
The compression degree was adjusted so that the intake resistance value was 3 mmAq or less, and the other treatments were the same, and the collection efficiency was measured and compared before and after passing through the tanning equipment.
As shown in Table 2, the collection efficiency of the fibers passed through the tanning equipment is improved compared to those before passing through, and polypropylene is the best fiber material, but JIS special grade No synthetic fibers other than wool fibers were found that met the standard collection efficiency of 99.5% or higher.

[Example 3]

Regarding the combination of synthetic fiber and rayon fiber (chemical fiber) in Example 2, the collection efficiency was compared after resin processing and tanning according to Example 1. By combining the main material with rayon fiber at a ratio within a specific range, it is possible to obtain a collection efficiency that exceeds the special grade standard of 99.5% and is superior to any other combination. , the results of various experiments were confirmed. [Example 4] Based on the results of Example 3, and based on the results of Example 3, a base material in which the ratio of polypropylene fibers and rayon fibers was varied in detail was treated in the same manner as in the above example, with other conditions being the same. As a result of measuring and comparing the dust collection efficiency before and after passing through the tanning equipment, as shown in Table 3, compared to polypropylene fiber alone,
When rayon fiber is added, the collection efficiency increases as the amount added increases, and at 50% of the amount added, it exceeds the JIS special grade standard.
It was maintained at 99.5%, and when it exceeded that level, the collection efficiency tended to decrease. The reason for this is not clear in detail, but rayon fiber has better water absorption than other synthetic fibers, and the resin liquid penetrates into the fiber itself, so adding an appropriate amount can reduce the electrostatic effect. This is considered to be a promotion. [Example 5] In order to confirm changes depending on the type of resin impregnated into the base material, the base material used in Example 4 was 80% polypropylene and 20% rayon.
Regarding the type of resin, in addition to vinyl acetate in the above example, most resins such as phenol, alkyd, acrylic, and styrene were used, and the other things were carried out in the same manner as in Example 1. As a result, vinyl acetate, acrylic, For all acrylic-styrene copolymers, collection efficiencies of 99.5% or higher, which meet the JIS special grade standard, were obtained.

[Table] [Example 6] As a means of tanning treatment, instead of the tanning method of Example 1, in which the tanning process involves passing through gaps between a plurality of rolls and repeatedly bending, a slit narrower than the thickness of the base material was used. A tanning method that gives elongation to the base material by passing it through a shaped part, or by pulling one end of the base material while pressing a part of the base material with an appropriate means, or pulling both ends of the base material without pressing it, The above-mentioned tanning method involves placing the base material on a surface plate and pounding it from above using a wooden mallet, or furthermore, by kneading it by hand. In addition to measuring and comparing the collection efficiency in the same manner as in the examples, we also observed the surface of the filters using a microscope, and found that all of the filters that had undergone these tanning treatments had fine cracks in the resin attached to the fibers. At the same time, the fibers themselves became fuzzy, and it can be inferred from the fact that the collection efficiency was improved in proportion to the degree of lint. It is thought that the adsorption area was greatly increased compared to the treated one, and the electrostatic effect was also greatly enhanced. As described in detail in the examples above, the present invention limits the material and blending ratio of fibers, and uses polypropylene fibers in a nonwoven fabric containing 50 to 90% polypropylene fibers, with the remainder being rayon, vinyl acetate, acrylic acid, or acrylic fibers.
After impregnating with a solution of synthetic resin made of styrene copolymer and drying, it is then mechanically bent, stretched, beaten, or manually loosened, or similar operations. It is characterized by tanning processing using physical means based on the conventional methods, and compared to conventionally known products, it has less air intake resistance and has a collection efficiency of over 99.5%, which is extremely superior (JIS
It can provide filter materials such as dust masks (for special grade standards), and is extremely useful industrially.

Claims (1)

[Claims] 1 50-90% polypropylene fiber, rayon fiber
After impregnating a 50-10% nonwoven fabric with an emulsified dispersion of a resin liquid whose main component is vinyl acetate, acrylic acid, or acrylic-styrene copolymer, the excess is removed using a squeezing roll. After squeezing out the liquid and pre-drying it at 50 to 60°C, and further heating and drying it at a constant temperature of about 100°C, the nonwoven fabric is subjected to a processing treatment in which the steps of bending, stretching, and beating occur simultaneously. A filter material for a dust mask, etc., characterized in that the nonwoven fabric generates static electricity.