JP2003293253A - Particle-including nonwoven fabric - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that, when functional particles are firmly fixed with an increased amount of binder, the air-flow resistance is increased and also the function of the particles cannot be developed fully, and to permit the used nonwoven fabric to be easily disposed of. <P>SOLUTION: The particle-including nonwoven fabric has a layer including 50-500 wt.%, based on the weight of the nonwoven fabric, of particles with an average particle size of 100-1,000 μm in the nonwoven fabric mainly comprising electlet-made aliphatic polyester fiber and the particles are fixed to the fabric by its thermal shrinkage of the nonwoven fabric made mainly of the aliphatic polyester. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-woven fabric having a high content of functional particles therein. For more details,
The present invention relates to a non-woven fabric that is particularly useful as a building material that adsorbs volatile components from an air purifying filter, wallpaper, and building materials, a vehicle ceiling material, protective clothing, and the like.

[0002]

BACKGROUND OF THE INVENTION Nonwoven fabrics containing or holding functional particles such as tourmaline particles, photocatalyst particles, and activated carbon on the surface thereof are used for clothes, protective clothing, filters, ceiling materials, wallpaper, sound absorbing materials and the like. In particular, since the dust removal function is enhanced under low pressure loss, the so-called electret filter and functional particle integrated product has a wide industrial application range. On the other hand, it is also an era where the treatment of used products must be fully considered.
Against this background, how to combine biodegradable materials and functional particles has become an important issue.

Japanese Patent Laid-Open No. 2001-333973 discloses a method of integrating polylactic acid fiber having biodegradability with activated carbon. However, 50% of the total fiber weight is used as the binder, and it cannot be said that the adsorption performance of activated carbon is fully utilized.

Further, Japanese Unexamined Patent Publication No. 2001-226860 discloses a method of filling functional particles in a non-woven fabric and covering both sides with a heat-sealing sheet. In this method, biodegradable fibers are used. Not only is there a problem in disposability after use, but because the functional particles are not firmly held between the sheets, the ventilation resistance and deodorizing performance during use are not stable, and there is a concern that particles may fall off. It was

[0005]

In order to fully exert the function of these functional particle-containing nonwoven fabrics, it is necessary to improve the contact between the fluid and the functional particles in order to exert the function. However, if the fixing of the functional particles is made strong by using a large amount of binder, there is a problem that not only the ventilation resistance increases but also the function of the functional particles is not sufficiently exhibited. We have found a method that solves these problems and is easy to dispose of after use.

[0006]

DISCLOSURE OF THE INVENTION According to the present invention, a layer in which 50 to 500% of particles having an average particle size of 100 to 1000 μm are contained in a nonwoven fabric mainly composed of electretized aliphatic polyester is contained. And a particle-containing non-woven fabric in which the particles are fixed by thermal contraction of the non-woven fabric mainly composed of the aliphatic polyester.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The nonwoven fabric containing the particles used in the present invention is required to have the following properties. First, in the present invention, the material forming the non-woven fabric needs to have an aliphatic polyester as a main component. The aliphatic polyester is preferably polylactic acid and / or a thermoplastic resin mainly composed of polylactic acid. The thermoplastic resin mainly composed of polylactic acid includes lactic acid with ε-
Cyclic lactones such as caprolactone, α-hydroxybutyric acid, α-droxyisobutyric acid, α-oxyacids such as α-hydroxyvaleric acid, ethylene glycol, glycols such as 1,4-butanediol, succinic acid, sepatic acid, etc. It is possible to use a copolymer of dicarboxylic acids of one kind or two or more kinds. A random copolymer and / or a block copolymer can be used for the copolymer. In addition, it is preferable to esterify the polymer molecule end with a compound having a carboxyl group at the molecule end, which can improve the stability during thermoforming.

Although the manufacturing method and the form of the non-woven fabric are not particularly specified, it is possible to treat the ordinary short fibers with a card and further form the non-woven fabric by mechanical entanglement or hydroentanglement. The spunbond method and melt blow method, which are methods for producing long-fiber non-woven fabrics, are also preferable for filter applications in which lint-free property without dropping of fibers is required. It is also possible to use a method in which a pre-charged film-like sheet is split into a non-woven fabric.

As a charging treatment for imparting an electrostatic dust collecting force to the non-woven fabric, a normal DC corona treatment can be used. The higher the applied voltage is, the higher the electrostatic force can be applied, but there is a possibility of causing problems such as sparks. It is also possible to electrify before spinning into a non-woven fabric. In addition, as described above, in the method in which the film-like sheet is split and then made into a non-woven fabric, one having a high charge density can be produced if it is charged in the film state. Further, as will be described later, it is naturally possible to sprinkle the functional particles between the non-woven fabrics, form a sheet to some extent, and then charge the particles.

The charging processing time is generally about 5 to 30 seconds, but if the time is too long, there is not much difference in performance, and an appropriate processing time can be selected. It is possible to apply a temperature between room temperature around 20 ° C. and the melting point of the polymer as a normal treatment temperature, but in the case of an aliphatic polyester, the stability of electrostatic force at a high temperature is improved as the temperature is increased. Therefore, it is preferable to perform the treatment at a temperature of about 50 to 130 ° C.

The basis weight of the nonwoven fabric is preferably 5 to 120 g / m ² . If the basis weight is too high, the pressure loss when used as a filter becomes large, and the filter becomes too bulky, which is not preferable.

It is desirable that the non-woven fabric forming the layer containing the particles does not adhere strongly to the particles. That is, the nonwoven fabric of the layer containing the particles of the present invention is used for the purpose of suppressing movement of particles in the nonwoven fabric in the in-plane direction. When the constituent fibers are strongly adhered to the particles, the surfaces of the particles are covered with the fibers and the function expression of the particles is hindered, which is not preferable. On the other hand, if the adhesion is too strong, the texture of the whole non-woven fabric becomes very hard and the use is limited, which is not preferable.

To prevent the functional particles from falling off, the fibers of the non-woven fabric containing the functional particles contract three-dimensionally more firmly and come into contact with the entangled fibers. With this method, the amount of the adhesive fiber or the adhesive polymer particle or the amount of either of them is significantly reduced or eliminated. Even when the adhesive component is used, 20% by weight or less of the total fiber weight or 20% by weight or less with respect to the functional particles is sufficient. Examples of usable adhesive components include core-sheath structure fibers and powdered hot melt binders. When a powder hot melt binder is used, stronger adhesion can be expected if it is mixed with the functional particles in advance.

Next, the thickness of the non-woven fabric needs to be 0.2 to 3.0 mm. If the thickness is less than 0.2 mm, it is impossible to form a space for maintaining a high content of particles, which is not preferable. When the thickness is larger than 3 mm, it is difficult to suppress the movement of the functional particles in the nonwoven fabric, which is not preferable.

Further, the filling rate of the non-woven fabric containing particles is preferably about 0.01 to 0.15 g / cc. More preferably, the packing density is between 0.02 and 0.10 g / cc. The smaller the packing density is, the more particles can be contained, which is preferable. However, the filling rate is 0.0
If it is much smaller than 1 g / cc, the resistance of the nonwoven fabric to compression or tensile deformation against external load becomes small and it becomes difficult to maintain the shape of the nonwoven fabric, which is not preferable. If the packing density is higher than 0.15 g / cc, it is difficult to contain a large amount of particles, and the ventilation resistance becomes high, which is not preferable.

The type of particles contained in the non-woven fabric may be any one having functionality such as activated carbon, photocatalyst particles, tourmaline particles. It is also one of preferred forms to contain non-spherical irregular-shaped particles such as diatomaceous earth in order to increase resistance to compressive deformation. When used for filter applications such as cabin filters and solvent recovery, activated carbon should be 100-600.
It is preferable to contain g / m ² . Also, the particles are
Although not necessarily spherical, the particles contained in the nonwoven fabric preferably have an average particle diameter corresponding to a sphere of 100 to 1000 μm. The sphere-equivalent particle diameter means the diameter of a sphere having the same volume as the particles. If the particle size is smaller than 100 μm, the particles are likely to fall through the openings of the nonwoven fabric, which is not preferable. When the particles are larger than 1000 μm, it is difficult to evenly disperse the particles in the nonwoven fabric, or when the nonwoven fabric is bent, problems such as the particles breaking the nonwoven fabric may occur, which is not preferable.

The particles are preferably contained in an amount of 50 to 600% based on the weight of the nonwoven fabric fiber component. By containing more particles, the function of the particles can be more effectively exhibited. However, if the particle content exceeds 600%, the amount of fibers that restrain the movement of the particles is reduced, so that there is a high possibility that the particles may fall off or the nonwoven fabric is difficult to bend.

The fact that a cover sheet is adhered to at least one surface of the particle-containing nonwoven fabric of the present invention can be carried out for the purpose of preventing particles from falling off and improving moldability.

It is also preferable to further laminate the electretized non-woven fabric on one surface of the non-woven fabric of the present invention to further enhance the dust removing function when it is used for air filters or protective clothing. Further, the effect of collecting particles from the non-woven fabric or the worn or cracked particles to prevent the particles from falling off can be expected. The following method is mentioned as one of the preferable modes for producing the nonwoven fabric of the present invention. First, the average diameter of 100 to
Fine particles of 1000 μm are 50 to 60 with respect to the weight of the nonwoven fabric.
After dropping a certain amount of 0% weight, shake or shear,
It is preferable to apply an external force such as stretching to permeate the particles into the inside of the nonwoven fabric, and then heat-shrink the fibers to integrate them.

With respect to the method of supplying particles, it is possible to disperse the particles evenly inside the nonwoven fabric by applying appropriate vibration or deforming deformation to the nonwoven fabric. The method of dropping particles is not particularly specified, but it is efficient to apply them with a rotary feeder or the like.

An infrared heater or a far infrared heater is preferably used as one of means for preheating the non-woven fabric or melting the heat-bonded fiber. By using an infrared heater or a far infrared heater, it is possible to uniformly heat the nonwoven fabric, and it is possible to obtain a laminate that is less likely to cause a peeling problem. The temperature near the surface of the non-woven fabric must be at least the glass transition point of the aliphatic polyester fiber used. For example, in the case of polylactic acid, heating at 70 ° C or higher is a standard. When the above-mentioned binder is used, it is preferable to perform heat treatment at the melting point of the binder component or higher. By doing so, the aliphatic polyester fiber component is heat-shrinked, and the functional particle component can be firmly held. When using a pre-charged non-woven fabric, the heat shrinkage must be such that the electretized charge is not lost. In any case, if the degree of shrinkage is raised too much, the ventilation resistance becomes too large for practical use, and the strength becomes unstable, so it is preferable to keep the shrinkage rate within 10%.

The present invention will be described in more detail with reference to the following examples, but the following examples are not intended to limit the present invention, and any modification of the design in accordance with the spirit of the preceding and the following will be applied to the present invention. It is included in the technical scope.

The numerical values in the examples are values measured by the following method. Example (Reduced Specific Viscosity) Chloroform was used as the solvent, 0.5 g / dl of the sample polymer was weighed, and the dissolved sample solution was used.
It measured using the Ubbelohde viscometer. (Acid value) The sample polymer was dissolved in a mixed solvent of chloroform / methanol (volume ratio 1: 1), and the solution was titrated with a sodium methoxide / methanol solution for measurement. (Basis weight) A non-woven fabric was cut into squares of 30 cm each, and the weight was measured, and then converted per 1 m ² . (Average fiber diameter) The surface image of the non-woven fabric is 1 with a scanning electron microscope.
It was photographed at a magnification of 500 times. Assuming that the fiber cross section was circular, the distance between the ends of each fiber side surface was measured and used as the fiber diameter. 100 fibers were randomly selected and measured, and the arithmetically averaged value was defined as the average fiber diameter (μm). (Dust removal efficiency) Air at room temperature is passed through the non-woven fabric at 10 cm / sec, and 0.3-0.5 μm air dust on the inlet side and the outlet side is measured as a dust particle concentration (pieces / cc) by a light scattering type particle concentration meter. The dust removal efficiency was measured by the following formula. Dust removal efficiency (%) = (1-((outlet concentration) / (inlet concentration))) × 100 (thickness) value when a load of 180 gf / cm ² is applied (sheet filling rate, bulk density) sheet filling density (G / cc) = sheet weight / sheet thickness [sheet thickness is a value under a load of 180 gf / cm ² ] (biodegradation test) A sample was subjected to a soil burying test. As a test method, the sample was buried at a depth of 10 cm for 6 months, and then the decomposition state was evaluated by appearance.

Example 1 The reduced specific viscosity obtained by the melt blow method was 1.52,
A basis weight of 35 g / m ² , a thickness of 1.2 mm, and a filling rate of 0.1, which is made of polylactic acid obtained by esterifying a terminal carboxyl group of a molecule having an acid value of 16 (eq / 10 3 kg) with lauryl alcohol.
03, an electric field of 20 KV was applied to a nonwoven fabric having an average fiber diameter of 10 μm to obtain a charged nonwoven fabric. Activated carbon particles having an average particle size of 0.4 mm were dropped onto the non-woven fabric by a rotary feeder so as to have an average particle size of 200 g / m ² . Then, it was pressed with a felt calender at 80 ° C. and a linear pressure of 1.5 kg / cm for about 15 seconds. A sample for measuring ventilation resistance was cut out from this nonwoven fabric, but almost no particles fell off from the cross section. In particular, what is generally called a binder is not used, but the adhesiveness is at a level where there is no problem in practical use. In addition, when the dust removal characteristics of the completed sheet were investigated, it was found that the dust removal function was hardly deteriorated from the characteristics of the electretized nonwoven fabric before spraying activated carbon. As a matter of course, the adsorption characteristic of the activated carbon was also examined by the JIS 1474 method using toluene gas, but it was confirmed that the adsorption characteristic was hardly deteriorated. Further, as a result of carrying out an embedding test of the used non-woven fabric in soil, it was found that the decomposition rate was very fast because polylactic acid had biodegradation.

Example 2 A reduced specific viscosity of 1.52 and an acid value of 16 (eq / 10 3 k)
30 g of a 40 g / m ² web of polylactic acid fiber (fineness: 3 dtex, fiber length: 64 mm) obtained by esterifying the terminal carboxyl group of g) with lauryl alcohol.
It was entangled with a water jet on a mesh screen to obtain a nonwoven fabric having a thickness of 1.0 mm. This non-woven fabric has a sufficient amount of oil removed during hydroentangling, and the amount of residual oil attached is 0.0
It was 1% or less. An electric field of 20 KV was applied to this non-woven fabric to obtain a charged non-woven fabric. Activated carbon was sprayed on this sheet by the same formulation as described in Example 1 to form a three-dimensional structure so that the activated carbon was entangled in the nonwoven fabric. Then, it was pressed with a felt calender at 80 ° C. and a linear pressure of 1.5 kg / cm for about 15 seconds. A sample for measuring ventilation resistance was cut out from this nonwoven fabric, but almost no particles fell off from the cross section. In particular, what is generally called a binder is not used, but the adhesiveness is at a level where there is no problem in practical use. Here again, when the dust removal characteristics of the completed sheet were investigated, it was also found that the dust removal function was not substantially deteriorated due to the characteristics of the electretized non-woven fabric before spraying activated carbon. As a matter of course, the adsorption characteristic of the activated carbon was also examined by the JIS 1474 method using toluene gas, but it was confirmed that the adsorption characteristic was hardly deteriorated. Further, as a result of carrying out an embedding test of the non-woven fabric after use in soil, it was found that polylactic acid was biodegradable and thus the decomposition rate was very fast.

Comparative Example 1 Polypropylene fiber (fineness: 3 dtex, fiber length: 64
A web of 40 g / m ^{2 made} of (mm) was entangled with a water jet on a 30 mesh screen to obtain a nonwoven fabric having a thickness of 1.0 mm. This non-woven fabric had the oil agent sufficiently removed during hydroentangling, and the residual oil agent adhesion amount was 0.01% or less. An electric field of 20 KV was applied to this non-woven fabric to obtain a charged non-woven fabric. Activated carbon was sprayed on this sheet by the same formulation as described in Example 1 to form a three-dimensional structure so that the activated carbon was entangled in the nonwoven fabric. Then, it was pressed with a felt calender at 80 ° C. and a linear pressure of 1.5 kg / cm for about 15 seconds. A sample for measuring ventilation resistance was cut out from this non-woven fabric, but the number of particles falling off from the cross section was considerably large. It is of a level that cannot be practically used. In addition, as a result of carrying out an embedding test of the used non-woven fabric in the soil, it was found that the non-decomposed non-decomposed non-woven fabric had very poor disposability.

[0027]

[Table 1]

[0028]

As described above, the nonwoven fabric of the present invention has the functional particles adhered to the electretized nonwoven fabric,
In addition, it is possible to provide a particle that does not fall off in practical use. Further, it is extremely excellent in disposability and has a great industrial applicability as compared with the prior art.

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Claims (2)

[Claims] 1. An average particle diameter of 100 to 1000 in a non-woven fabric mainly composed of electretized aliphatic polyester.
A particle-containing non-woven fabric having a layer in which 50 to 500% of the particles of μm are contained in the weight of the non-woven fabric. 2. The particle-containing nonwoven fabric according to claim 1, wherein the particles are fixed by heat shrinkage of the nonwoven fabric mainly composed of the aliphatic polyester.