JPH02191759A - High-tenacity sheet - Google Patents

Abstract

PURPOSE:To obtain the subject sheet, excellent in filter performance, heat insulating properties, etc., and useful as a heat insulating material, diapers, etc., by randomly mixing two specific kinds of fibers therein and partially and thermally binding the fibers. CONSTITUTION:The objective sheet obtained by randomly mixing ultrafine fibers (e.g. a thermoplastic polymer, such as polyester or polyolefin) having 0.1-8.0mum average fiber diameter in 20-80wt.% (based on the total amount of the fibers) mixed fibers (the same fibers as those of the ultrafine fibers are used) having compatibility with the above-mentioned ultrafine fibers, >=1.5 denier and >=30mm average fiber length, partially and thermally binding the fibers according to a thermal embossing method, etc.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a high-strength sheet material containing ultrafine thermal fibers.

More specifically, regarding sheets that are highly strong and have excellent filter performance, bacterial barrier properties, dust absorption, liquid absorption, and heat insulation properties, we will discuss ultrafine fiber sheets that are particularly suitable for various filters, wipers, wraps, insulation materials, etc. Regarding strong sheets. However, since the sheet referred to in this specification substantially corresponds to a nonwoven fabric, the following description will be made using a nonwoven fabric.

[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 properties, liquid absorption properties, heat insulation properties, etc., and have been used for a variety of applications by taking advantage of these characteristics. .

Regarding the melt blowing method, please refer to Industrial and Engineering Chemistry (10dusLri).
al and Engineering Chesi
stry) Volume 48, No. 8 (P, 1342-134
6), 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 iut is mixed with ultrafine fibers. In other words, the special public service in 1986
Publication No. 30065 discloses that at least three fibers are a mixture of ultrafine fibers and crimped staple fibers with a larger diameter.
An elastic fibrous web for thermal insulation having a loft of 0 d/g is disclosed.

Also, JP-A-55-30498 and JP-A-59
Japanese Patent Publication No. 183723 discloses a wiper containing extremely at fibers and crimped thick short fibers.

[Problem to be solved by the invention]

Nonwoven fabrics made only of ultrafine fibers, especially ultrafine fiber webs obtained by the melt-blowing method, are high-quality porous bodies with extremely small pore sizes, so they have excellent filter performance, bacterial barrier properties, dust absorption, liquid absorption, and heat insulation properties. However, on the other hand, it has the problem of low strength, which greatly limits its applications. For this reason, it is extremely rare for Mel I/Blowweb to be used alone; in terms of -a, it is used in combination with high-strength nonwoven fabrics such as spunbond nonwoven fabrics, or woven or knitted fabrics, etc.
There was a cost problem.

On the other hand, in the aforementioned Japanese Patent Publication No. 61-30065,
The purpose of mixing thick I with compressed stable fibers and ultrafine fibers is to increase the bulk of the web (higher porosity), thereby increasing the heat insulation properties. Also, JP-A-55-3
In both Publication No. 0498 and especially Publication No. 183723/1986, the purpose of mixing thick crimped short fibers is to improve the porosity (increase in bulk) of the web, thereby improving the dust absorption and absorption characteristics of the wiper. The purpose was to increase the liquid properties. As described above, the aim of mixing short fibers in the known technique is to increase the porosity by increasing the bulk.

In addition, in the case of the nonwoven fabric of JP-A No. 55-30498,
As is clear from the examples, polypropylene, polyethylene, and acrylic polymers were used as the ultrafine fibers,
Different materials such as polyethylene terephthalate, nylon, and nylon 6.6 are used as the thick fibers to be mixed. Since these two types of fibers are not compatible with each other, even if they 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 features of the ultra-fine fibers were lost, but also the reinforcing effect of the ultra-thick fibers was hardly exhibited, resulting in insufficient strength-enhancing effects.

In addition, when the thermal bonding between the ultrafine fibers is the main one, there is a problem that not only the performance of the ultrafine fibers deteriorates, but also the ultrafine fibers become hardened or brittle, resulting in a particularly low tear strength. A similar problem is also seen in the case of the nonwoven fabric disclosed in JP-A-59-1.83723.

The present invention aims to create a single-layer type high-strength ultra-fine fiber non-woven fabric that maintains the features of the above-mentioned ultra-fine fiber web as much as possible, and that does not involve lamination with other high-strength non-woven fabrics such as spunbond. The purpose is to provide.

[Means to solve the problem]

The objective of the present invention is to use ultrafine fibers with an average fiber diameter of 0.1 to 8.0 mm, a fiber diameter of 1.5 denier or more, and an average fiber length of 30 I or more.
2, and is made up of a random mixture of fibers that are compatible with the ultra-fine fibers, and at least the thick fibers and the ultra-fine fibers are partially thermally bonded. achieved.

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, copolymers and blends thereof, polyvinyl chloride, acrylic and acrylic copolymers, polystyrene, polyarylene sulfide, polysulfone, and the like. In the present invention,
The ultrafine fibers are thermoplastic fibers, particularly thermoplastic polymer fibers of the same type that are compatible with the mixed fibers, for the purpose of increasing the thermal bonding strength between the ultrafine fibers and the fibers mixed with the fibers (hereinafter referred to as mixed fibers).

The ultrafine fibers referred to in the present invention have an average fiber diameter of 0.1
It is preferable to use fibers with an average fiber diameter of ~8.0- or less, preferably an average fiber diameter of 0.5-6.0p, particularly preferably 1.0-5.
．． The fibers preferably have an average fiber diameter in the range of 0-.

If the average fiber diameter is less than 0.1, it is not preferable because although it is flexible, the fiber strength is low and fluff may fall off, which limits its uses. - On the other hand, if it is 8.0p or more, the strength of the nonwoven fabric will be high, but on the other hand, the above-mentioned characteristics of ultrafine fibers such as filter performance, bacterial barrier property, dust absorption property, liquid absorption property, and heat insulation property will be inferior, so this is not preferable. The mixed fibers are thermoplastic fibers that are compatible with the ultrafine fibers.

Such mixed fibers are selected from materials such as polypropylene, polyolefins such as polyethylene, polyester 1 nylon 6 such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon 6.6, and polyacrylonitrile. Examples include copolymers and blends of. Further, the number of material components may be two or more.

A combination in which ultrafine fibers and mixed fibers are compatible is when these two types of fibers are of the same material system. For example, when the ultra-Ia fiber (A) is polyolefin, the mixed fiber (B) is also polyolefin, When A is polyester, B
When A is polyester, B is also polyamide, and these may be a copolymer or a blend. In particular, when A is polypropylene, B
is polypropylene, and when A is polyethylene terephthalate, B is also polyethylene terephthalate and A is nylon 6.
In this case, a combination of the same materials, such as B and nylon 6, is most preferable in terms of easy thermal bonding and strength. By creating a compatible combination of ultrafine fibers and mixed fibers,
Appropriate thermal bonding occurs between these two types of fibers, resulting in the effect that the tensile strength, and especially the tear strength, of the nonwoven fabric is greatly improved.

The mixed fibers of the present invention may or may not be crimped, but if they are 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. Also, I
It is also preferable to use it as a heat insulating material because it improves the heat insulation properties when there is shrinkage.

Furthermore, since the pressure loss of 1R and the amount of dust retained are also reduced, this is also a preferable direction when used as a filter.

The crimp ratio is preferably 15% or more.

In the present invention, the denier (fiber diameter) and fiber length of the mixed fibers are important as they affect the strength of the nonwoven fabric.

The mixed fiber has a denier of 1.5 denier or more, preferably 2 to 25 denier, particularly 3 to 20 denier.

If it is less than 1.5 denier, the effect of improving tear strength is not sufficient. The larger the denier of the mixed fibers, the higher the tear strength, but if the denier exceeds 25, the nonwoven fabric will be hard and have a poor feel, which is not preferable.

In addition, the average fiber length of the mixed fiber is 30Illf11 or more,
Preferably 35-110++ua, especially 50-8011ua
111 is preferred.

If it is less than 30 IW, the effect of improving tear strength is insufficient.

The longer the average fiber length of the mixed fibers, the higher the tear strength, but even if the fiber length is increased by 110 mm or more, the tear strength hardly increases and becomes almost saturated. Furthermore, if the average fiber length of the mixed fibers is too long, it becomes difficult to uniformly disperse the fibers into the ultrafine fibers, and in some cases, the tear strength may decrease.

In the present invention, the tear strength is maximized when the mixed fiber has a denier of 1.5 denier or more and the average fiber length does not exceed 30 fibers at the same time.

The higher the tensile strength of the mixed fibers, the higher the tear cooperation and tensile strength of the nonwoven fabric. The tensile strength of the blended fibers is preferably at least 2 g/denier, especially 3 to 10 g/denier.

Although the phenomenon in which the tear strength is improved in the present invention is not necessarily clear, it can be summarized as follows. That is,
The tear strength of a nonwoven fabric is almost determined by the cutting of the mixed fibers, which are stronger than the ultrafine fibers, and the greater the strength ((strength per denier) x (denier)) of the mixed fibers, the higher the tear strength of the nonwoven fabric. Furthermore, it is necessary for the mixed fibers to be firmly fixed in the nonwoven yarn and not to be pulled out, etc., in order to fully exhibit the strength of the mixed fibers. In the nonwoven fabric of the present invention, since the ultrafine fibers and the mixed fibers are compatible, they can be thermally bonded sufficiently, and since the fiber length of the mixed fibers is relatively long, in addition to the thermal bonding with the ultrafine fibers, the mixed fibers can also be bonded to each other. It is thought that a large amount of thermal bonding occurs, and as a result, the mixed fibers are firmly fixed in the nonwoven fabric.

In the nonwoven fabric of the present invention, it is preferable that the mixed fibers are randomly mixed substantially in the form of single fibers in 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 (overlap) of the mixed fibers to the total amount of fibers is 20 to 80%, preferably 30 to 70%, especially 40 to 60%. If it is 20% or less, the thermal bonding force is low and sufficient strength is not obtained. Difficult 0. 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.

Also, Kiwami! [il! It is more preferable that the II 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.

The nonwoven fabric of the present invention may contain a composite fiber containing a low melting point component as a mixed fiber.It is preferable to mix composite fibers to increase tensile strength as well as tear strength as a synergistic effect.

Furthermore, since the ultrafine fibers obtained by the melt blowing method have extremely small fiber diameters, it is difficult to estimate the average length of the fibers, but 30I! 111 or more, often 1
Estimated to be 00-500ma.

The weight of the nonwoven fabric of the present invention is 10 to 200 g/nf, preferably 20 to 1.50 g/nf, especially 25 to 100 g
/bo is preferred.

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

Examples of mixing methods for mixed fibers include melt blowing,
In the flash spinning method, a web of crimped short fibers is created, and this is mixed into a group of ultrafine fibers being spun using a Rickerin roll or the like to obtain a sheet-like product; There is a method in which a sliver is made into a sliver, defibrated using a combing roll (a roll with many teeth), and then mixed in the same manner as described above to obtain a sheet.

Another method is to further cut the short fibers mixed with the ultrafine fibers obtained by the super draw method or the sea-island fiber method to prepare a slurry in which two types of fibers are mixed, and then form the slurry into a sheet using the papermaking method. These fiber sheets may be subjected to a tantalization 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. Especially the hot air bonding method,
The ultrasonic bonding method is preferred because it can thermally bond the nonwoven fabric without pressurizing it, resulting in a bulky nonwoven fabric and fully exhibiting the features of the ultrafine fibers described above. It is sufficient that the thermal bonding temperature is above the temperature at which thermal bonding occurs, and for boat fishing, it is sufficient that the ultrafine fiber is softened. On the other hand, if the temperature is raised above the melting point of the ultrafine fibers, the ultrafine fibers will undergo a lot of thermal bonding, which is undesirable. Therefore, in the present invention, it is preferable that the softening point of the ultrafine fibers be higher than the melting point of the ultrafine fibers.

The nonwoven fabric of the present invention can be subjected to seed post-treatment. 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.

r Example] EXAMPLES 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 (grain) Ten arbitrary points on the sample were 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 (ffill) Measured using a beef-ink type thickness needle under a constant load of 130 g/cd.

◎Tensile strength (g/fabric weight) A sample of 20ml x 160mm was taken, and using a universal tensile tester (Tensilon), the gripping length was 10.
0mm, load capacity 100kg, tensile speed 100m/min, value per 1 CIl, unit date (Ig/nf)
It was converted into a hit.

◎Tear Strength (g/Weight) Take a 60-medium x 65-inch length sample, place the sample on a 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 weight (1 g/ryf).

◎Collection efficiency (%), pressure loss (ta HtO) In addition, a particle counter manufactured by K company (model C-
01B), dust particles of 0.3 μm or more were measured using the atmospheric suction method at a suction air rate of 0.51/min.

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

■　Pressure) Fire Read the differential pressure before and after the sample with the differential pressure needle.

◎ Wiping Performance (Oil Absorption) Kerosene was used as the dust, and each was sprinkled onto an acrylic plate, and evaluated by the size of the wiping residue when actually wiped.

◎Crimp ratio (%) This is the value obtained by dividing the difference between the uncrimped length and the crimped length of the fiber by the crimped length and multiplying it by 100.

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

Polypropylene was spun using a melt-blowing method to obtain a group of ultrafine fibers with an average fiber diameter of 1.7 μm. The melting point of this fiber is D
When measured by SC, it was 158°C. On the other hand, polypropylene fibers of 6 denier, length 64111II, tensile strength 3.5 g/denier, and crimp ratio 40% are used as mixed fibers, and this fiber is made into a sliver. The fibers were allowed to fly and mixed into the previously dug fiber group. The mixed fibers were collected on a moving net surface provided below to obtain a 20 cm 11 web. This web had no lumps of crimped short 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 heat embossing roll having a width of 30 cm and having a diagonal (45°) grid pattern. At this time, the temperature of the hot roll was 130°C, the press pressure was 10 kg/cdG, and the processing speed was 6 m/min.

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

Table 1 As is clear from this table, the strength (especially tear strength) of the product of the present invention was significantly improved, and it was possible to use it alone. Moreover, it was found to have excellent oil absorption properties.

Implementation ■ Also, in the same manner as in Example 1, polypropylene was melt-blown to prepare a group of ultrafine fibers, and on the other hand, the denier and fiber length of the polypropylene short fibers to be mixed were varied, and the fibers were randomly and uniformly mixed in the same manner as in Example 1. A web with a basis weight of 50 g/rd was obtained. The tensile strength of short polypropylene fibers is 3
~6 g/denyl. Mixing ratio of crimped short fibers is 50%
Met.

This web was thermally bonded over the entire surface using a 30 cm wide heat press machine (metal/rubber roll) at a metal roll temperature of 140'C, a press pressure of 10 kg/cdG, and a processing speed of 6 m/min.

Table 2 shows the physical properties of this nonwoven fabric.

Table 2 It can be seen that the cracking strength increases.

In addition, although the strength of Experiment k14 was excellent, the nonwoven fabric was somewhat hard and the feel was also slightly inferior.

A mixed fiber nonwoven fabric was obtained in exactly the same manner as in Example 1, except that the mixing ratio of the mixed short fibers was varied. The results are shown in Table 3.

Table 3 As is clear from this Table 2, the mixed short fibers are 1.5 denier or more, the fiber length is 38 mm or more, and especially from Table 3, the mixing ratio of the mixed short fibers is 20 to 80%. It turns out that it is preferable in terms of both strength and filter performance.

Example 11: Polyethylene terephthalate was spun using a melt blow method to obtain a group of ultrafine fibers with an average fiber diameter of 2.5 μm. The melting point of this fiber was 258°C. On the other hand, as a mixed fiber, a polyethylene terephthalate fiber of 8 denier, length 30 mm, crimp rate (10%) was made into a 1.5 m sheet by the carding method, and this sheet was solved with a ricken! The fibers were allowed to fly and mixed uniformly into the flying fibers, and the fibers were collected by the moving net surface to obtain a randomly mixed web of 1.5 m. The mixing ratio of shortened fibers is 70
%Met.

The gonotsu nib was thermally bonded with ito''c using a hot embossing roll with a discontinuous circular pattern.

The weight of the obtained nonwoven fabric was 1.00 g/xd,
The thickness was 0.65 am, the tensile strength was 12.7 g/fabric weight, the tear strength was 20.48/of, and the filter performance was also excellent.

Fruit = Lathe 5 Polyethylene terephthalate was melt-blown to form a group of ultrafine fibers with an average fiber diameter of 0.9n (melting point 258°C),
Crimped polyethylene terephthalate fibers of 6 denier and 75 strands in length were uniformly mixed in the same manner as in Example 1. The mixing ratio was 30%.

This web was thermally bonded using hot air at 14.0"C.

The obtained nonwoven fabric had a basis weight of 80 g/d, a thickness of 1.1 ya,
Tensile strength 10.8 g / fabric weight, tear strength 13.7 g
/ [It was rated J and had excellent filter performance and heat insulation properties.

[Effects of the Invention] Since the nonwoven fabric of the present invention is configured as described above, it has almost all of the filter performance, bacteria barrier properties, dust absorption properties, liquid absorption properties, and heat insulation properties that ultrafine fiber nonwoven fabrics have. Since it does not require any single member and has significantly improved strength, especially tear strength, it can be used alone without reinforcing it by pasting it with other high-strength sheets.

For this reason, it can be widely used not only as various filters, wipers, wraps, and insulation materials, but also as civil engineering materials such as roofing materials and wall materials, and medical and sanitary materials such as surgical gowns, sheets, diapers, and napkins. Ta.

Moreover, it is advantageous in terms of process since it does not require pasting other sheet-like materials, etc., and is therefore excellent in terms of cost. Therefore, the present invention has great industrial significance.

Claims (1)

[Claims] Ultrafine fibers having an average fiber diameter of 0.1 to 8.0 μm; 1.
A sheet consisting of a random mixture of fibers having a denier of 5 denier or more, an average fiber length of 30 mm or more, and having compatibility with the ultrafine fibers, wherein at least the thick fibers and the ultrafine fibers are partially thermally bonded. High strength sheet.