JP5812786B2 - High strength nonwoven fabric - Google Patents

Description

  The present invention comprises a fused liquid crystal-forming wholly aromatic polyester fiber, a substrate for resin reinforcement (FRP) such as a printed circuit board and an abrasive carrier, a tape substrate, a bag filter, a lithium ion secondary battery separator, a fuel cell electrolyte membrane The present invention relates to a nonwoven fabric useful for a reinforcing base material and the like and a method for producing the same.

As a high-strength nonwoven fabric made of a melted liquid crystal-forming wholly aromatic polyester, a wet nonwoven fabric having an average breaking length of 3 km or more has been proposed (for example, see Patent Document 1). However, the wet nonwoven fabric of Patent Document 1 has a length in the vertical direction of less than 10 km, a width in the horizontal direction of less than 6 km, and is substantially 20 g / m ² or less because of the wet method. It is also difficult to reduce the weight and weight.

On the other hand, a melt blown nonwoven fabric having a breaking length of 1.5 km or more made of a melted liquid crystal forming wholly aromatic polyester has been proposed (for example, see Patent Document 2). However, in the melt blown nonwoven fabric of the prior art document 2, since there are ² or more 1 mm ^{2 of} film-like parts where the fibers converge, the length in the vertical direction is substantially less than 10 km, and the width in the horizontal direction is less than 6 km. Therefore, it cannot be said that the resin reinforcing (FRP) base material or bag filter has sufficient strength.

JP-A-8-170295 Japanese Patent No. 4429501

  An object of the present invention is to provide a high-strength nonwoven fabric made of a melted liquid crystal-forming wholly aromatic polyester having almost no film-like material and having a high breaking length.

  As a result of intensive studies, the present inventors have found that a melt liquid crystal-forming wholly aromatic polyester nonwoven fabric produced by melt spinning using a spinning nozzle having a specific structure and further heat-treating under specific heat treatment conditions is the above. The present inventors have found that the problems can be solved and completed the present invention.

That is, the present invention comprises a substantially continuous filament having a melt liquid crystal forming wholly aromatic polyester having a melt viscosity at 310 ° C. of 20 Pa · s or less and an average fiber diameter of 0.5 μm or more and 15 μm or less. It is a melt blown nonwoven fabric characterized by satisfying both (1) and (2) below.
(1) The film-like material having a size of 0.02 mm ² or more present in the nonwoven fabric is less than 2 pieces / 1 mm ² ;
(2) The length in the vertical direction is 10 km or more and the length in the horizontal direction is 6 km or more.

  The present invention also provides a melt blown non-woven fabric by melt-spinning a melted liquid crystal-forming wholly aromatic polyester and at the same time blowing off the spun product with a high-temperature high-speed fluid to accumulate on the collecting surface to form a web and subjecting it to heat treatment. A nozzle having a nozzle hole diameter of 0.1 to 0.3 mm, a nozzle hole length to nozzle hole diameter ratio (L / D) of 20 to 50, and a nozzle hole spacing of 0.2 to 1.0 mm. The nonwoven fabric obtained by melt spinning is subjected to a heat treatment for 3 hours or more at a temperature of <melting point of molten liquid crystal forming wholly aromatic polyester −40 ° C.> or higher and <melting point temperature + 20 ° C.> or lower. It is related with the manufacturing method of said melt blown nonwoven fabric.

  The nonwoven fabric mainly composed of a melted liquid crystal-forming wholly aromatic polyester obtained by the present invention has heat resistance, high strength, and non-hygroscopicity, so that resin reinforcement for printed circuit boards, polishing carriers, etc. It is useful for (FRP) base materials, tape base materials, bag filters, lithium ion secondary battery separators, fuel cell electrolyte membrane reinforced base materials, and the like.

Hereinafter, the present invention will be described in detail.
The molten liquid crystal-forming wholly aromatic polyester used in the present invention is a resin excellent in heat resistance and chemical resistance. The molten liquid crystal-forming wholly aromatic polyester referred to in the present invention is an aromatic polyester that exhibits optical anisotropy (liquid crystallinity) in the molten phase. For example, a sample is placed on a hot stage and heated in a nitrogen atmosphere. It can be recognized by observing the transmitted light. The melted liquid crystal-forming wholly aromatic polyester is composed mainly of repeating structural units of aromatic diol, aromatic dicarboxylic acid, and aromatic hydroxycarboxylic acid. For example, what consists of the combination of the repeating structural unit group shown below is preferable.

  Among the combinations of the repeating structural unit groups described above, the main components are parahydroxybenzoic acid and 2-hydroxy-6-naphthoic acid, or parahydroxybenzoic acid, 2-hydroxy-6-naphthoic acid, terephthalic acid, and biphenol. Is preferable as the molten liquid crystal-forming wholly aromatic polyester used in the present invention.

  It is important that the melted liquid crystal-forming wholly aromatic polyester used in the present invention has a melt viscosity at 310 ° C. of 20 Pa · s or less. If the melt viscosity at 310 ° C. exceeds 20 Pa · s, it is not preferable because it is difficult to make ultrafine fibers, or oligomers are generated during polymerization, and troubles occur during polymerization or granulation. On the other hand, if the melt viscosity is too low, fiberization is difficult, and it is desirable to exhibit a melt viscosity of 5 Pa · s or more at 310 ° C.

  The molten liquid crystal-forming wholly aromatic polyester has the functions of the present invention as required by adding additives such as colorants, inorganic fillers, antioxidants, ultraviolet absorbers and thermoplastic elastomers as necessary. It can be added as long as it does not inhibit.

Next, the manufacturing method of the nonwoven fabric by the melt blow method of the molten liquid crystal forming wholly aromatic polyester of the present invention will be described in detail below.
As the spinning device, a conventionally known melt blow device can be used. However, regarding the spinning nozzle to be used, the nozzle hole is preferably 0.1 to 0.3 mmφ, and more preferably 0.15 to 0.2 mmφ. preferable. If the nozzle hole is less than 0.1 mmφ, nozzle clogging is likely to occur. On the other hand, if it exceeds 0.3 mmφ, the discharge pressure becomes insufficient, and the molten resin in the nozzle hole fluctuates and yarn breakage is likely to occur.

  Moreover, regarding the spinning nozzle to be used, the ratio (L / D) of the nozzle hole length to the nozzle hole diameter is preferably 20 to 50, and more preferably 25 to 45. When L / D is less than 20, polymer orientation is insufficient and yarn breakage is liable to occur. Conversely, when L / D exceeds 50, pressure loss in the nozzle tube increases, the load on the nozzle increases, and the durability of the nozzle Decreases. In order to maintain the durability of the nozzle, there is a method of reducing the polymer discharge amount, but in this case, the productivity is lowered.

  Furthermore, it is preferable that the space | interval of nozzle holes is 0.2-1.0 mm, and it is still more preferable that it is 0.25-0.75 mm. When the interval between the nozzle holes is less than 0.2 mm, adjacent fibers directly under the spinning are fused to form a yarn lump, and the homogeneity is impaired. On the other hand, if the thickness exceeds 1.0 mm, the interfiber gap becomes too large, and in this case, the homogeneity is impaired.

The spinning conditions are preferably a spinning temperature of 310 to 360 ° C., a hot air temperature (primary air temperature) of 310 to 380 ° C., and an air amount (per nozzle length of 1 m) of 10 to ³⁰ Nm ³ .

  Thus, the average fiber diameter of the fiber which comprises the nonwoven fabric of this invention manufactured is required to be 0.5 micrometer or more and 15 micrometers or less. If the average fiber diameter is less than 0.5 μm, fluff is likely to be formed into a fiber lump, and if it exceeds 15 μm, the formation becomes rough, which is not preferable. Preferably they are 1 micrometer or more and 10 micrometers or less, More preferably, they are 2 micrometers or more and 5 micrometers or less. In addition, in this invention, an average fiber diameter refers to the average value of the value which magnified and imaged the nonwoven fabric with the scanning electron microscope, and measured arbitrary 100 fiber diameters.

Further, in the nonwoven fabric of the present invention thus produced to, it is necessary that film material of 0.02 mm ² or more in size is less than 2/1 mm ^2. If there are two film-like parts of 0.02 mm ² or more / 1 mm ² or more, it becomes a disadvantage, and sufficient strength is not exhibited after post-heating treatment. In addition, in this invention, a film-form thing expands and images a nonwoven fabric with a scanning electron microscope, and refers to the part of a fiber convergence and a lump.

The nonwoven fabric obtained by melt spinning from the spinning nozzle of the present invention is subjected to a heat treatment for 3 hours or more at a temperature of <melting point of melted liquid crystal-forming wholly aromatic polyester −40 ° C.> or higher and <melting point temperature + 20 ° C.> or lower. Do. Examples of the gas used as the heating medium during the heat treatment include a mixed gas such as nitrogen, oxygen, argon, carbon dioxide, or air, but oxygen or air is more preferable in terms of cost and an effect of improving the adhesion to the resin. . The heat treatment may be under tension or without tension depending on the purpose.
When heat treatment is performed at a temperature lower than <melting point of molten liquid crystal-forming wholly aromatic polyester −40 ° C.>, fiber surface modification does not proceed sufficiently, and the heat treatment temperature is less than <melting liquid crystal-forming wholly aromatic When the melting point of the polyester group exceeds + 20 ° C., the polymer is softened, the fiber starts to melt, a part of the sheet is formed into a film, the air permeability of the nonwoven fabric is lost, and the voids are blocked.

  The nonwoven fabric of the present invention that is heat-treated in this way has a length in the vertical direction of 10 km or more and a length in the horizontal direction of 6 km or more. High power that can not be.

  There is no strict restriction on the basis weight of the melted liquid crystal-forming wholly aromatic polyester melt blown nonwoven fabric of the present invention, and the basis weight can be appropriately determined according to the required performance.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to the examples. In addition, the physical property of the nonwoven fabric in this invention means what was measured with the following method.

[Average fiber diameter μm]
An arbitrary value in the nonwoven fabric was magnified 1000 times with a scanning electron microscope, and an average value of values obtained by measuring 100 fiber diameters was defined as an average fiber diameter.

[Fracture length km]
Using an autograph manufactured by Shimadzu Corporation, according to JIS L 1906, the nonwoven fabric breaking strength was measured at three locations in each of the vertical and horizontal directions, and the breaking length was calculated from the average value according to the following formula.
Breaking length = <Strength (N) / Measurement width (mm) / Weight per unit (g / m ² ) /9.8> × 1000

[Area of film-like material, number of film-like materials]
For 10 arbitrary locations and 1 mm ² locations in the nonwoven fabric, take an enlarged photograph with a scanning electron microscope at a magnification of 100 times, calculate the area of the film-like material while using the fiber converging part and the lump part as a film-like material, and measure the number did.

[Example 1]
Molten liquid crystal forming fully aromatic polyester (polyplastics) comprising a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid and having a melting point of 300 ° C. and a melt viscosity of 15 Pa · s at 310 ° C. Co., Ltd., Vectorer L type) is extruded by a biaxial extruder, and has a nozzle hole diameter of 0.15 mmφ, L / D = 30, and a nozzle with 4000 holes per 1 m width (interval between nozzle holes of 0.25 mm). After supplying to a melt blown nonwoven fabric manufacturing apparatus and spraying at a single-hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C. and 35 Nm ³ , a nonwoven fabric having a basis weight of 40 g / m ² was obtained. Treated at 300 ° C. for 6 hours. The obtained non-woven fabric has an average fiber diameter of 2.6 μm, 0.2 mm ² or more of film-like material is 0 piece / 1 mm ² , the length in the vertical direction is 25 km, and the length in the horizontal direction is 11 km. There was a very high strength nonwoven fabric.

[Example 2]
A nonwoven fabric having a basis weight of 8 g / m ² was produced in the same manner as in Example 1. The average fiber diameter of the nonwoven fabric is 2.4 μm, 0.2 mm ² or more of film-like material is 0 piece / 1 mm ² , the length in the vertical direction is 16 km, and the length in the horizontal direction is 11 km. In addition, a high-strength nonwoven fabric with a low basis weight was obtained.

[Example 3]
The basis weight is 40 g / m under the same conditions as in Example 1 except that a nozzle having a hole diameter of 0.15 mmφ, L / D = 20, and 1300 holes per 1 m width (interval between nozzle holes: 0.77 mm) is used. It was obtained ² of non-woven fabric. The obtained non-woven fabric has an average fiber diameter of 3.2 μm, 0.2 mm ² or more of film-like material is 0 piece / 1 mm ² , the vertical tear length is 22 km, and the lateral tear length is 9 km. There was a very high strength nonwoven fabric.

[Comparative Example 1]
Molten liquid crystal forming fully aromatic polyester (polyplastics) comprising a copolymer of parahydroxybenzoic acid and 6-hydroxy-2-naphthoic acid and having a melting point of 300 ° C. and a melt viscosity of 15 Pa · s at 310 ° C. Co., Ltd., Vectorer L type) is extruded with a biaxial extruder, and nozzles with a nozzle hole diameter of 0.08mmφ, L / D = 30, and 1300 holes per 1m width (interval between nozzle holes 0.77mm) Although it supplied to the melt blown nonwoven fabric manufacturing apparatus which has, since the nozzle hole diameter was too small, nozzle clogging occurred frequently and the target nonwoven fabric was not obtained.

[Comparative Example 2]
The same fused liquid crystal-forming wholly aromatic polyester as in Example 1 was extruded by a biaxial extruder, the nozzle hole diameter was 0.4 mmφ, L / D = 30, and the number of holes was 1300 per 1 m width (the interval between the nozzle holes was 0. 0). The melt blown nonwoven fabric manufacturing apparatus having a nozzle of 77 mm) was sprayed at a single-hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ to obtain a nonwoven fabric with a basis weight of 40 g / m ² . However, since the nozzle hole diameter was too large, yarn breakage occurred frequently just below the nozzle, and there was much fluff scattering, and the intended nonwoven fabric could not be obtained.

[Comparative Example 3]
The same fused liquid crystal forming fully aromatic polyester as in Example 1 was extruded by a biaxial extruder, nozzle hole diameter 0.15 mmφ, L / D = 15, 1300 holes per 1 m width (interval between nozzle holes 0.77 mm) ) Was supplied to a melt blown nonwoven fabric manufacturing apparatus having a nozzle of No. ¹⁾ and sprayed at a single hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C., and 35 Nm ³ to obtain a nonwoven fabric with a basis weight of 40 g / m ^2. In comparison with Example 3, the L / D of the nozzle was too small, and there were many yarn breaks directly under the nozzle. Further the treated 6 hours at 300 ° C. in air, the average fiber diameter of the obtained non-woven fabric is 3.4 .mu.m, 0.2 mm ² or more film-like portion is four / 1 mm ^2, in the longitudinal direction The breaking length was 8 km, the breaking length in the horizontal direction was 3 km, and the strength was insufficient.

[Comparative Example 4]
The same molten liquid crystal forming wholly aromatic polyester as in Example 1 was extruded by a biaxial extruder, and a nozzle having a nozzle hole diameter of 0.15 mmφ, L / D = 30, and a nozzle having a number of holes of 650 per 1 m width (interval between nozzle holes 1. 54 mm), blown at a single-hole discharge rate of 0.05 g / min, a resin temperature of 310 ° C., a hot air temperature of 310 ° C. and 35 Nm ³ to obtain a nonwoven fabric of 40 g / m ² , then in the air For 6 hours at 300 ° C. The average fiber diameter of the obtained non-woven fabric was 3.1 μm, and the film-like portion of 0.2 mm ² or more was 1 piece / 1 mm ² , but the length in the vertical direction was 7 km, and the length in the horizontal direction was It was 3 km and the strength was insufficient. This is probably because the interval between the nozzle holes was too wide.

[Comparative Example 5]
A nonwoven fabric having a basis weight of 40 g / m ² was obtained under the same conditions as in Example 1 except that heat treatment was performed at 250 ° C. for 3 hours. The obtained nonwoven fabric had an average fiber diameter of 2.4 μm and a film-shaped portion of 0.2 mm ² or more was 0 piece / 1 mm ² , but the vertical tear length was 5.3 km, and the lateral tear length Was 3.2 km, and sufficient strength could not be obtained. This is probably because the heat treatment temperature was too low.

[Comparative Example 6]
A nonwoven fabric having a basis weight of 40 g / m ² was obtained under the same conditions as in Example 1 except that heat treatment was performed at 340 ° C. for 3 hours. The obtained nonwoven fabric had a heat treatment temperature that was too high, so that most of the fibers melted into a film, lost air permeability, and became an unsuitable structure as a base material to be impregnated with a filter or resin.

  The nonwoven fabric mainly composed of the melt-liquid crystal-forming wholly aromatic polyester of the present invention has heat resistance, high strength, and non-hygroscopicity, so that resin reinforcement (FRP) for printed circuit boards, polishing carriers, etc. It is useful for a substrate, a tape substrate, a bag filter, a lithium ion secondary battery separator, a fuel cell electrolyte membrane reinforced substrate and the like.

The scanning electron micrograph which shows an example of the surface state of the nonwoven fabric without the film-like material of this invention. The scanning electron micrograph which shows an example of the surface state of the nonwoven fabric in which the conventional film-form thing is scattered.

Claims (2)

It consists of a substantially continuous filament having a melt liquid crystal-forming wholly aromatic polyester having a melt viscosity at 310 ° C. of 20 Pa · s or less and an average fiber diameter of 0.5 μm or more and 15 μm or less. ) And (2) are satisfied, a melt blown nonwoven fabric having a basis weight of 40 g / m ² or less .
(1) The film-like material having a size of 0.02 mm ² or more present in the nonwoven fabric is less than 2 pieces / 1 mm ² ;
(2) The length in the vertical direction is 10 km or more and the length in the horizontal direction is 6 km or more. When melt-spun melted liquid crystal-forming wholly aromatic polyester and at the same time blow off the spun product with a high-temperature high-speed fluid to form a web by accumulating on the collecting surface, and when heat-treated to produce a melt-blown nonwoven fabric, The nozzle hole diameter is 0.1 to 0.3 mmφ, the nozzle hole length to nozzle hole ratio (L / D) is 20 to 50, and the nozzle holes are 0.2 to 1.0 mm in distance from the spinning nozzle. The obtained non-woven fabric is subjected to a heat treatment for 3 hours or more at a temperature of <melting point of melted liquid crystal-forming wholly aromatic polyester −40 ° C.> or higher and <melting point temperature + 20 ° C.> or lower. A method for producing a melt blown nonwoven fabric.

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