JPH0291262A - High-tenacity nonwoven fabric - Google Patents

Abstract

PURPOSE:To provide the subject nonwoven fabric composed of ultrafine fibers and conjugate fibers containing a thermoplastic component having larger average fiber diameter and lower melting point than the ultrafine fiber, having excellent filtering performance, bacteria barrierness, dust-adsorptivity, liquid-absorbing property and heat-insulation and useful for various filters, laps, etc. CONSTITUTION:The objective nonwoven fabric is produced at a reduced cost by randomly mixing (A) ultrafine fibers (e.g., polyethylene terephthalate fiber) with (B) 20-80wt.% of conjugate fibers containing a thermoplastic component having an average fiber diameter larger than that of the ultrafine fiber and a melting point lower than that of the ultrafine fiber by 10-200 deg.C (e.g., copolymerized polyester) and thermally bonding the low-melting thermoplastic components with each other. The fabric has a single-layer structure composed solely of ultrafine fiber without deteriorating the characteristic features of ultrafine fiber web.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high-strength nonwoven fabric containing ultrafine fibers. More specifically, regarding nonwoven fabrics that have excellent filter performance, bacterial barrier properties, dust absorption, liquid absorption, and heat insulation properties, as well as high strength, we will discuss ultrafine fibers that are particularly suitable for various filters, wipers, wraps, insulation materials, etc. Regarding strong nonwoven fabrics.

[Conventional technology]

Nonwoven fabrics made of ultrafine fibers, especially ultrafine fiber nonwoven fabrics obtained by melt blowing, have excellent filter performance, bacterial barrier properties, dust absorption, liquid absorption, and heat insulation properties, and have been used for a variety of applications by taking advantage of these characteristics. .

For melt blowing methods, see Industrial and Engineering Chemistry.
al and Engineering Chemises
try) Volume 48, No. 8 (P, 1342-1346
), 1956, disclosed the basic apparatus and method. Further, Japanese Patent Publication No. 56-33511 and Japanese Patent Application Laid-Open No. 55-142757 disclose methods for producing ultrafine fibers such as polyolefins and polyesters.

On the other hand, the following are known as nonwoven fabrics in which thick short fibers are mixed with ultrafine fibers. In other words, Special Public Interest Publication 1986-
No. 30065 includes 1 ultrafine fiber and a larger diameter)
At least 30c mixed with crimped staple fibers
An elastic fibrous web for thermal insulation having a loft of +fl/g is disclosed.

Also, JP-A-55-30498 and JP-A-591
No. 83723 discloses a wiper containing ultrafine fibers and crimped thick short fibers.

[Problems to be Solved by the Invention] Nonwoven fabrics made only of ultrafine fibers, especially ultrafine fiber webs obtained by melt blowing, are high-quality porous bodies with extremely small pore sizes, so they have excellent filter performance, bacterial barrier properties, It has the advantage of being excellent in dust absorption, liquid absorption, heat insulation, etc., but on the other hand, it has the problem of being low in strength and its uses are greatly limited. For this reason, melt-blown webs are rarely used alone; -1. Generally, they are used in combination with high-strength nonwoven fabrics such as spunbond nonwoven fabrics, or woven or knitted fabrics.
There was a cost problem.

On the other hand, in the above-mentioned Japanese Patent Publication No. 61-30065, the purpose of mixing thick crimped staple fibers with ultra-fine fibers is to increase the bulk of the web (increase porosity), thereby increasing the heat insulation properties. It is something. Also, JP-A-55-304
In Report No. 98 and Japanese Patent No. 59-183723, the purpose of mixing very thick crimped short fibers is to improve the porosity of the web (
The aim was to increase the dust absorption and liquid absorption properties of wipers. in this way,
The aim of mixing short fibers in the known technique is to improve the porosity by increasing the bulk.

Furthermore, in the case of JP-A No. 55-30498, as is clear from the examples, polypropylene, polyethylene, and acrylic polymers are used as the ultra-fine fibers, and polyethylene terephthalate and polyethylene terephthalate are used as the ultra-thick fibers to be mixed.
Not only are different materials such as nylon and nylon 6.6 used, but also extra-thick fibers with a melting point higher than that of extra-fine fibers are used.

Therefore, even if the fibers are thermally bonded, the ultrafine fibers and the thick fibers are not sufficiently bonded, and the ultrafine fibers are essentially thermally bonded to each other. For this reason, not only the characteristics of the ultra-fine fibers were impaired, but also the reinforcing effect of the ultra-thick fibers was hardly exhibited, resulting in an insufficient strength-improving effect. On the other hand, since a relatively high temperature is required to create a thermal bond between the ultra-fine fiber and the thick fiber, in this case, the ultra-fine fiber of the low-melting point material is significantly damaged.
Not only does the performance of ultrafine fibers deteriorate due to hardening and brittleness, but there is also little improvement in strength;
In particular, there was a problem in that the tear strength (tear strength) often decreased. Further, the same problem can be seen in the case of the non-woven fabric 1 disclosed in Japanese Patent Application Laid-Open No. 59-183723.

The present invention provides a single-layer type high-strength micro-fiber nonwoven fabric that does not impair the features of the micro-fiber web described above as much as possible, and does not involve lamination with other high-strength non-woven fabrics such as spunbond. The purpose is to

[Means for Solving the Problems] The object of the present invention is to provide ultrafine fibers having an average fiber diameter larger than the ultrafine fibers, and having an average fiber diameter of 10°C to 2
00'C A nonwoven fabric randomly mixed with conjugate fibers containing a thermoplastic component having a low melting point as a part thereof, wherein the bonding of the constituent fibers in the nonwoven fabric is at least the ultrafine fibers and the conjugate fibers. This is achieved by a high-strength nonwoven fabric that is formed by thermal bonding between low-melting thermoplastic components.

The ultrafine fibers of the present invention include polyolefins such as polypropylene and polyethylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, and nylon 6
, polyamides such as nylon 6.6 and their copolymers, polyvinyl chloride, acrylic and acrylic copolymers, polystyrene, polyarylene sulfide, polysulfone, and inorganic fibers. In the present invention, in order to increase the thermal bonding strength between the ultrafine fibers and the mixed short fibers, it is preferable to select thermoplastic fibers, especially thermoplastic polymer fibers of the same type that are compatible with the low melting point component of the mixed composite fibers. .

The ultrafine fibers referred to in the present invention have an average fiber diameter of 8.
It is good to use fibers of Otn+ or less, preferably those having an average fiber diameter of 0.5 to 6.0 mm, particularly preferably 1.0 to 5.0 mm.
Preferably, the fibers have an average fiber diameter in the range of 0.0 mm. If the average fiber diameter is 0.1 tones or less, it is not preferable because although it is flexible, the fiber strength is low and the fluff may fall off, which limits its uses. On the other hand, when the temperature is 8.0 or more, the strength of the nonwoven fabric increases, but on the other hand, the above-mentioned features of ultrafine fibers such as filter performance, bacterial barrier properties, dust absorption properties, liquid absorption properties, etc.
It is not preferred because its insulation properties are poor.

The fibers mixed with the ultrafine fibers in the nonwoven fabric of the present invention are:
It is a composite fiber containing as a part of a thermoplastic component which has an average fiber diameter larger than that of the ultrafine fiber and has a melting point 10 to 20 Q'C lower than the melting point of the ultrafine fiber.

Such composite fibers are selected from materials such as polyolefin, polyester, polyamide, and polyacrylonitrile, and also include copolymers and blends thereof. As a composite form, parallel type (Side-by-3id
e), Sheath-Core type, and eccentric type, but are not limited to these.Also, the number of material components may be two or more, but at least some of the low melting point components It is necessary to be located on the surface of the fiber. Typical composite fibers include polyolefins,
Combination of polypropylene and polyethylene (product name: ES
Examples of polyester-based materials include, but are not limited to, combinations of polyethylene terephthalate and copolymerized polyester as a low-melting point component (product name: Helcombi 0), and combinations of polyethylene and polyesters such as polyethylene terephthalate. isn't it.

The composite fiber of the present invention may or may not be crimped, but if it is crimped, the ultrafine fiber nonwoven fabric will be bulkier and will have better dust absorption properties.
It has improved liquid absorption and is suitable for wiper applications. In addition, it is also preferable to use the material as a heat insulating material because crimping improves heat insulating properties.

Furthermore, since the pressure loss and the amount of dust retained are improved, it is also preferable to use it as a filter.

The 1441 ratio is preferably 15% or more.

The fiber diameter (denier) of the composite fiber is important because it affects the strength of the nonwoven fabric. In the present invention, it is preferable to use fibers with an average fiber diameter of 10μ or more as fibers having an average fiber diameter larger than that of ultrafine fibers, preferably 15 to 60μ, particularly preferably 20μ.
~45-. It has been found that the larger the average fiber diameter, the better the tensile strength and tear strength of the nonwoven fabric when mixed at the same weight ratio, and that sufficient strength can be obtained when the average fiber diameter is 10μ or more. The fiber length of the composite fibers is not particularly limited, and may be short fibers or long fibers. Short fibers are preferable in order to mix randomly and uniformly in the ultrafine fibers, and the length of the fibers is 3 to 100 mm.
, particularly preferably 10 to 80 peng.

The melting point of the thermoplastic component constituting the composite fiber must be 10 to 200"C lower than the melting point of the ultrafine fiber. Preferably 20 to 150"C, particularly preferably 25 to 10
It is 0°C.

If this melting point difference is smaller than 0°C, the melting points of the composite short fibers and the ultrafine fibers are too close, and in the thermal bonding process, there will be a lot of thermal adhesion between the ultrafine fibers in addition to the adhesion by the composite fibers. Not only are the above-mentioned features of the ultrafine fiber web significantly reduced, but the tear strength also decreases and the texture becomes extremely hard.

On the other hand, if the melting point difference exceeds 200°C, the melting point of the low melting point component of the composite fiber will be too low and problems such as peeling will occur depending on the subsequent usage conditions.

In this way, only when the melting point difference is in the range of 10 to 200°C, the filter performance, which is a feature of the ultrafine fiber web, can be improved.
High strength can be achieved with almost no loss in bacterial barrier properties, dust absorption properties, liquid absorption properties, and heat insulation properties.

Although this phenomenon is not necessarily clear, it can be considered as follows. In other words, since the difference in melting point between the low melting point components of the ultrafine fibers and the mixed fibers is 10"C or more, it is possible to thermally bond the ultrafine fibers with each other with almost no heat fusion. In addition, if there is a lot of thermal bonding between these ultrafine fibers, the tear strength of the reinforcing fibers, that is, the parts without composite fibers, will be particularly low, and tears will occur from these parts. Unfavorable.Moreover, since the fibers to be mixed are composite fibers, thermal bonding is possible centering on the intersections of the fibers, and the mixed fibers maintain their fiber shape even after heat fusion bonding, resulting in high strength. can be achieved.

As a combination of the ultrafine fiber (A) and the low melting point component (B) of the composite fiber, for example, A is polyethylene terephthalate (melting point 258°C) and B is a copolymerized polyester (diethylene glycol as the zero component for terephthalic acid and polyethylene). A is polyethylene terephthalate (melting point 258°C), B is polypropylene (melting point 161°C), A is polyethylene terephthalate (melting point 258°C), and A is polyethylene terephthalate (melting point 258°C). ), and B is polyethylene (melting point 13
2°C), A may be polypropylene (melting point 158°C), B may be polyethylene (melting point 132°C), etc.

The melting point in the present invention can generally be measured with a DSC (differential scanning calorimeter), and appears as an endothermic peak. There are some materials with an amorphous structure that do not necessarily have a clearly defined melting point, but in this case, the generally known softening point is used as a substitute. This is because most of these materials exhibit endothermic peaks when measured using the DSC described above.

Further, the softening point can be determined using differential thermal analysis (DTA). The softening point is the temperature at which the slope of the DTA graph changes for the first time.

In the nonwoven fabric of the present invention, the conjugate fibers are randomly mixed in substantially single fibers among the ultrafine fibers. With such a mixed state, high strength can be achieved without substantially impairing the features of the ultrafine fibers described above. The mixing ratio (weight) of the composite fiber to the total fiber amount is 20 to 80%, preferably 30 to 70%,
In particular, 40 to 60% is preferable. If it is less than 20%, the thermal bonding strength is low and it is difficult to obtain sufficient strength. On the other hand, if it is 80% or more, the above-mentioned characteristics of the ultrafine fiber will be impaired, which is not preferable.

Further, it is further preferable that the ultrafine fibers are also randomly dispersed in the form of single fibers, since the above-mentioned various performances are enhanced. Further, the nonwoven fabric of the present invention may be a mixture of a third material, fibers with different fiber diameters, shapes, etc., powder, etc.

In addition, since the ultrafine fibers obtained by the melt-blowing method have an extremely small fiber diameter, it is difficult to estimate the average length of the fibers, but it is 30 mm or more, and in many cases 100 to 100 mm.
Estimated to be 500mm.

The method for obtaining the ultrafine fiber nonwoven fabric of the present invention is not particularly limited, such as a melt blow method, a flash spinning method, a super draw method, or a combination of a composite fiber method and a paper making method, but the melt blow method is particularly preferred.

Examples of mixing methods for composite fibers include melt blowing,
In the flash spinning method, a web of crimped composite staple fibers is created, and this web is flown through a group of ultrafine fibers being spun using a Rickerin roll, etc., to create a roll-like object with a number of teeth in the mixture.
There is a method in which a sheet-like material is obtained by defibrating the fibers, flying them, and mixing them in the same manner as described above. In addition, the short fibers mixed with the ultrafine fibers obtained by the super draw method and the sea-island fiber method are
Preferably, there is a method of cutting into pieces of 5 to 10 mm, mixing these two types to prepare a slurry, and forming the slurry into a sheet using a papermaking method. These ultrafine fiber sheets may be subjected to -tan entangling treatment.

Examples of the thermal bonding method include a hot embossing method, a hot Kangoo method, a hot air method, and an ultrasonic bonding method. In particular, the hot air bonding method is preferable because it can thermally bond the nonwoven fabric without pressurizing it, yielding a bulky nonwoven fabric and fully exhibiting the features of the ultrafine fibers described above. The thermal bonding temperature need only be above the temperature at which thermal bonding occurs, and - for boat fishing, it is sufficient to be above the softening point of the low melting point component of the mixed short fibers. On the other hand, if the temperature is increased above the melting point of the ultrafine fibers, the ultrafine fibers will be thermally bonded to a large extent, which is not preferable. Therefore, in the present invention, it is preferable that the softening point of the low melting point component of the mixed fiber is higher than the softening point and lower than the melting point of the ultrafine fiber.

The nonwoven fabric of the present invention can be subjected to various post-treatments. For example, it is possible to further improve the filter performance and dust suction power by converting it into an electret using a corona discharge method or the like.

〔Example〕

The present invention will be explained in more detail with reference to Examples below.

The definitions and measurement methods of various physical properties shown in Examples and Comparative Examples are shown below.

◎Average fiber diameter (distortion) An arbitrary lO location of the sample was examined using an electron microscope at a magnification of 2000.
Take 10 photos at double magnification. Measure the diameter of 10 arbitrary fibers for each photograph, and do this for each of the 10 photographs. A total of 100 fiber diameter measurements are obtained and the average value is calculated.

◎Thickness (mm) Measured using a peacock type thickness meter under a constant load of 130 g/ci.

◎Tensile strength (g/date) A sample with a width of 20 mm and a length of 160 mm was taken, and using a universal tensile test Ja (Tensilon), the grip length was 100.
The cylinder has a load capacity of 100 kg and a tensile speed of 100 mm/min.
) per unit.

◎Tear strength (g/fabric weight) Take a 601u [II width x 65mm length] sample, stop the sample on the sample stand, and make a cut with a knife. Read the maximum vibration using an Elmendorf tear tester. This value was converted into per unit area weight (1 g/rtf).

◎Collection efficiency (%), pressure loss (mm)
Using B), dust of 0.3 tnn or more was measured by the atmospheric suction method under conditions of suction air filO, 5j2/min.

■Collection efficiency Read the number of particles with and without sample (blank) using a vertile counter and calculate using the following formula.

■One member lost pressure Read the differential pressure before and after the sample with a differential pressure gauge.

◎1 Crinkage rate (%) This is the value obtained by dividing the difference between the fiber end shrinkage length and the crimp length by the crimp length and multiplying it by 100.

◎Mixing ratio (%) This is the value obtained by dividing the mixed fiber weight by the total nonwoven fabric weight and multiplying it by 100.

2 and 1" 11,2 polypropylene is spun using the melt blow method to obtain an average fiber diameter of 1.7.
It was made into a group of ceramic microfibers. The melting point of this fiber was 158°C as measured by DSC. Fiber diameter 20m (6d),
Eccentric composite fiber with a length of 64 mm and a crimp rate of 40% [core:
Polypropylene, melting point 161°C1 Sheath: Polyethylene, melting point 132°C1 (Product name: ES fiber, Chisso,
(manufactured by Company K)] was made into a sliver, and a large number of the slivers were defibrated with a combing roll to fly short fibers and mixed into the ultrafine fiber group at the tip. This mixed fiber group was collected on a moving net provided below to obtain a web with a width of 20 stamps. This web had no lumps of crimped conjugate fibers, and was substantially dispersed in the form of single fibers, which were random and uniform. The mixing ratio of crimped short fibers was 50%.

This web was thermally bonded by passing through a 30 cm medium heat embossing roll with a diagonal (45°) grid pattern. At this time, the temperature of the hot roll was 130°C, the press pressure was 10 kg/c, and the G1 processing speed was 6 m/min.

Table 1 shows the weight and physical properties of this nonwoven fabric. As a comparison,
A thermally bonded nonwoven fabric made only of ultrafine fibers without mixing crimped short fibers (
The values of comparative product 1) and the nonwoven fabric (comparative product 2) obtained in exactly the same manner as described in Example 1 except that polyethylene terephthalate fibers were used as the crimped short fibers to be mixed are also shown in Table 1. .

Table 1 As is clear from this table, the strength of the product of the present invention was significantly improved and it was possible to use it alone. Surprisingly, however, it was found that even the filter performance improved, and the oil absorption was also disappointing.

Fusenmasu I Polyethylene terephthalate was spun using a melt blow method to obtain a group of ultrafine fibers with an average fiber diameter of 2.5 mm. The melting point of this fiber was 258°C. Fiber diameter 16jM (4d)
, length 30 mm, parallel type composite fiber with crimp rate 60% (polypropylene melting point 161°C; polyethylene, melting point 132
°C) is made into a 1.5 m wide sheet using a card method, this sheet is defibrated with a Rickerin roll, and the fibers are uniformly mixed into the flying ultrafine fibers on the moving net surface. A randomly mixed web of 1.5 ml was obtained. The mixing ratio of crimped short fibers was 70%.

This web was thermally bonded at 100'C using a hot embossing roll with a discontinuous circular pattern.

The fabric weight of the obtained nonwoven fabric is 100 g/rd, and the thickness is 0.6
2mm, tensile strength is 20.4 g/date, tear strength is 14.8 g/rr? The filter performance was also excellent.

Polyethylene terephthalate, mainly polyethylene terephthalate, was melt-blown to obtain a group of ultrafine fibers (melting point: 258°C) with an average fiber diameter of 0.9-.

A crimped sheath-core composite fiber with a diameter of 20 mm (4 d) and a length of 51 mm [core: polyethylene terephthalate, melting point 257°
C3 sheath: copolymerized polyester, melting point (softening point) 110
°C1 (trade name: Bell Combi, manufactured by Kanebo Co., Ltd.)] was uniformly mixed in the same manner as in Example 1. Mixing rate is 30%
Met.

This web was thermally bonded using hot air at 120'C.

The obtained nonwoven fabric has a basis weight of 80 g/rd and a thickness of 1.0 m.
m, tensile strength 16.7 g / fabric weight, tear-resistant cuff, 8 g
/ basis weight, and had excellent filter performance and heat insulation properties.

Comparison Main Example 2. A nonwoven fabric was obtained in exactly the same manner as in Example 2, except that the fiber diameter of the composite fibers mixed in step was 9n.

The basis weight of this nonwoven fabric is 100g/rd, and the thickness is 0.54m.
m, the tensile strength was 10.9 g/fabric weight, and the tensile strength was as low as 3.2 g/fabric weight, so it was difficult to use it alone.

〔Effect of the invention〕

Since the nonwoven fabric of the present invention is configured as described above, it has almost all of the excellent features of the ultrafine fiber nonwoven fabric, such as filter performance, bacterial barrier properties, dust absorption properties, liquid absorption properties, and heat insulation properties (without forming shells). On the contrary, it is possible to improve the strength of the filter, and the strength is significantly improved, so it can be used alone without reinforcement such as pasting with other high-strength sheets.For this reason, various filters can be used. It can now be used not only as wiper wraps and insulation materials, but also as civil engineering materials such as roofing materials and wall materials, medical materials and sanitary materials such as surgical gowns, sheets, diapers, and napkins. This invention does not require pasting together sheet-like materials and is advantageous in terms of process, and is therefore excellent in terms of cost. Therefore, the present invention has great industrial significance.

Claims (1)

[Claims] having ultrafine fibers and an average fiber diameter larger than the ultrafine fibers,
A nonwoven fabric randomly mixed with composite fibers containing a thermoplastic component having a melting point 10°C to 200°C lower than the melting point of the ultrafine fibers, wherein the bonding of the constituent fibers in the nonwoven fabric is A high-strength nonwoven fabric formed by thermal bonding between at least the ultrafine fiber and the low melting point thermoplastic component of the composite fiber.