JPH05177107A - Continuous perforated sheet and its production - Google Patents

Abstract

PURPOSE:To obtain a continuous perforated sheet as an air filter excellent in air/liquid permeability, heat resistance, moldability and uniformity by compounding monofilaments of a thermoplastic synthetic fiber and a thermosetting resin having heat flowability to form them into a composite web and subjecting the composite web to continuous hot press molding. CONSTITUTION:50-95wt.% of a thermoplastic synthetic fiber with a fiber length of 1-200mm and 50-5wt.% of a thermosetting resin whose heat flowability measured by a discuring method is 30-150mm are compounded by a wet or dry lamination method to form a continuous web. This continuous web is subjected to continuous hot press molding not only to cure the thermosetting resin but also to adjust void content to 40-95% and thickness irregularity to 10% or less. By this method, a continuous perforated sheet having the excellent shaping processability of the thermoplastic synthetic fiber and the heat resistance of the thermosetting resin is obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is excellent in breathability / liquid permeability, heat resistance, and moldability in molding such as shaping.
The present invention relates to a continuous porous sheet having further improved uniformity and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, woven fabrics and non-woven fabrics made of thermoplastic synthetic fibers have been widely used as filter media for filters such as air filters. For example, it is known from JP-A-57-147413.

As these fiber materials, thermoplastic synthetic fibers such as polyamide fibers, polyester fibers, polyolefin fibers and acrylic fibers are often used.

These filters are designed compactly, and in order to increase the filtration area of the filter medium, they are often subjected to shaping such as pleating. Especially in the case of air filters, most of these processed products are used.

[0005] In recent years, as the diversification and performance of filters have increased, the applications for use in high temperature environments are increasing. However, if the above materials are used for such applications as they are, they lack heat resistance, and therefore shrinkage, fusion, Or, the initial performance cannot be maintained due to deformation or the like due to the applied force.

On the other hand, even if an attempt is made to use a non-woven fabric made of inorganic fiber such as glass fiber having excellent heat resistance to meet the above-mentioned demand, pleating or the like is caused due to lack of essential heat setting property of these materials. Shape processing is difficult.

The present invention combines the excellent shaping processability of thermoplastic synthetic fibers with the heat resistance of a cured thermosetting resin,
Moreover, it is an object of the present invention to provide a continuous porous sheet suitable as a filter material for an air filter having excellent ventilation and liquid permeability and uniformity, and a method for producing a continuous porous sheet capable of easily producing such a sheet.

[0008]

The inventors of the present invention have arrived at the present invention as a result of intensive research to solve such problems. That is, the present invention is a sheet in which a thermoplastic synthetic fiber and a cured thermosetting resin are compounded, having a large number of continuous pores penetrating from one surface of the sheet to the other surface, The gist of the present invention is a continuous porous sheet having a porosity of 40 to 95% and a thickness variation of 10% or less.
50 mm to 95% by weight of 200 mm thermoplastic synthetic fiber and 30 to 150 mm of thermosetting resin measured by the disk cure method
5% by weight is compounded or compounded by a wet stacking method or a dry stacking method to form a continuous web, which is continuously hot pressed to cure a thermosetting resin and has a porosity of 50 to 50%.
The gist is a method for producing a continuous porous sheet, which is characterized by adjusting 95% thickness unevenness to 10% or less.

The continuous porous sheet of the present invention has 50 to 95% of interconnected pores, has excellent ventilation / liquid permeability, shaping processing and heat resistance, and is a material with further improved uniformity. Is.

As the fibers constituting the continuous porous sheet of the present invention, any conventionally known fibers can be adopted, but thermoplastic synthetic fibers are preferable in view of the required properties such as heat setting property. For example, polyester fiber, polyamide fiber,
Polyvinyl alcohol fiber, polyolefin fiber,
Examples include thermoplastic synthetic fibers such as polyacrylic fibers. The fiber length of these fibers is 1 to 200 mm, preferably 5
-100 mm is preferred. When the fiber length is less than 1 mm, the strength of the continuous porous sheet is insufficient, and when the fiber length is 200 mm or more, it becomes difficult to form a web by the wet stacking method or the dry stacking method. The fiber diameter of the fibers forming the continuous porous sheet is, for example, 0.1 to 10 denier, preferably 1 to 5 denier.

On the other hand, the thermosetting resin constituting the continuous porous sheet of the present invention includes phenol resin, urea resin, melamine resin, benzoguanamine resin, furan resin, alkyd resin, unsaturated polyester resin, diallyl phthalate resin, epoxy resin, Examples include conventionally known resins such as polyurethane resin, silicone resin, and polyimide resin or copolymers thereof, or crosslinked polymer compositions obtained by inducing a crosslinking unit into a thermoplastic resin. In consideration of easy moldability that can obtain a cured molded product by dry molding from a reactive raw material, resoleated novolac resin, phenol-formaldehyde resin or melamine
Thermosetting resins such as formaldehyde resin are most suitable.

The continuous porous sheet of the present invention is a composite sheet of the above-mentioned thermoplastic synthetic fiber and thermosetting resin. The ratio of the thermoplastic synthetic fiber and the thermosetting resin constituting these is 50 to 95% by weight to 50 to 5% by weight, respectively, are suitable. If the thermosetting resin content exceeds 50%, the moldability of the continuous porous sheet such as shaping is poor, and if it is less than 5%, the heat resistance of the continuous porous sheet is insufficient. The ratio of the thermosetting resin is preferably in the range of 10 to 40% by weight in the normal operation.

The thermoplastic synthetic fiber of the present invention (hereinafter,
When necessary, they are simply referred to as fibers. ) And a thermosetting resin (hereinafter, simply abbreviated as a resin, if necessary) means compounding fibers and resin, filling the resin between the fibers, and fixing the fibers to each other. .. However, not all the spaces between the fibers are filled with the resin, but this is applied locally. When viewed from the fibers, this is a state in which the thermosetting resin is coated on the surface of at least a part of the fibers existing independently of the composite state, or the fiber aggregate in which two or more fibers are in contact with or close to each other. ..

The continuous porous sheet of the present invention (hereinafter, simply referred to as a sheet if necessary) has a large number of continuous pores penetrating from one side of the sheet to the other side. Here, the continuous pores are the gaps between fibers that are continuously connected, in particular,
It means an organization in which relatively sparse gaps are connected.

Next, the sheet of the present invention has a large number of continuous pores penetrating from one surface of the sheet to the other surface. Such continuous pores mean that the gaps between the fibers joined together by the thermosetting resin are continuous and penetrate from one surface of the sheet to the other surface, which is complicatedly bent. There are various shapes of pores such as those that penetrate relatively linearly, those that have a branch, those that have a cavity, and those that have a bottleneck.

While the definition of open pores is as set forth above, the following criteria are used to define a web structure having a large number of open pores that achieves the objects of the present invention. That is, when a circular plate with a diameter of 10 mm is cut out from a continuous porous sheet with a thickness of 1.5 mm and air is flown through this circular plate at a rate of 1 Nm ³ / min, continuous pores will be generated if the pressure loss is 1000 mmH ₂ O or less. Judging to have The smaller the pressure loss when flowing the air, the larger the proportion of the continuous pores in the sheet. The above pressure loss also represents the degree of air permeability of the sheet. In a continuous porous sheet of the present invention, it is preferable that the pressure loss is 500mmH ₂ O or less, particularly preferably 200 mm ₂ O or less. The porosity (%) of the continuous porous sheet of the present invention must be 40 to 95% in order to maintain the desired pressure loss and strength.

The porosity (%) is the ratio of the pore volume to the total volume of the continuous porous sheet expressed as a percentage. The porosity (%) is specifically measured as follows. First, the dry weight W (g) and volume V of the sheet
Measure (cm ³ ). Next, the true specific gravities of the fibers and the resin forming the sheet are measured, and the weight average specific gravity B is calculated. Next, the apparent specific gravity A of the continuous porous sheet is measured, and the porosity (%) is calculated by the following formula.

[0018]

[Equation 1]

A: Apparent specific gravity of the continuous porous sheet B: Load average specific gravity of the components of the continuous porous sheet If the porosity is less than 40%, the proportion of the continuous pores decreases and the air permeability decreases, which is not preferable. On the other hand, if the porosity exceeds 95%, mechanical properties such as bending strength of the continuous porous sheet tend to deteriorate, which is not preferable.

Further, the continuous porous sheet of the present invention has extremely small unevenness in the thickness of the sheet and is excellent in uniformity. If this is expressed quantitatively, the thickness of any 10 randomly selected points within a 90 cm square sheet is measured, and the percentage of the difference between the maximum value and the minimum value with respect to the average value of these measurement points is defined as thickness unevenness. Then, the thickness variation of the continuous porous sheet of the present invention is 10% or less.

The following method is effective for producing such a continuous porous sheet of the present invention with high quality and economically. First, 50 to 95% by weight of the above-mentioned thermoplastic synthetic fiber having a fiber length of 1 to 200 mm and a thermosetting resin having a heat fluidity of 50 to
A continuous web is prepared by compounding 5% by weight with a wet stacking method or a dry stacking method.

Here, the thermoplastic synthetic fiber is as described above, but the thermosetting resin having heat fluidity is the above-mentioned thermosetting resin, in particular, resoleated novolac resin, phenol-formaldehyde resin, melamine. It is a substance having heat fluidity before curing treatment of a resin such as formaldehyde resin.

Among these substances, those suitable for the continuous porous sheet of the present invention are disc cure methods, that is, resins specified in 5.3.2 [molding material (disc flow)] of Japanese Industrial Standard JIS-K-6911 _1979. 30-150m expressed by the elongation of
It has a thermal fluidity of m, preferably 50 to 120 mm (hereinafter abbreviated as HPF).

The HPF of these thermosetting resins is 30 mm
If it is less than the above, it is difficult to form a continuous porous sheet having a desired strength by continuous hot pressing in the next step. On the other hand, if the HPF exceeds 150 mm, a sheet having heat resistance sufficiently cured by continuous hot pressing is obtained. Hard to form.

The morphology and shape of the resin also have an important influence on the performance, quality and productivity of the product. The morphology and shape of the thermosetting resin having heat fluidity useful for the continuous porous sheet of the present invention are spherical particles having a particle size of 10 to 1000 μm.

Particularly preferably, the novolak resin and hexamethylenetetramine are added in an aqueous solvent in the presence of a dispersant.
It is a spherical resol novolac resin obtained by suspension polymerization. Since the present spherical powder has good fluidity and extremely excellent dispersibility in fitting into the fiber gap, a sheet having excellent uniformity can be obtained because compounding, compounding and web formation are easy.

The compounding, compounding and web formation of the continuous porous sheet of the present invention are preferably prepared by a wet stacking method or a dry stacking method. Here, the wet stacking method uniformly mixes a predetermined amount of fiber and resin in a predetermined amount of a liquid medium such as water.
A predetermined amount of the fiber / resin mixture that is dispersed and solid-liquid separated by papermaking such as wire mesh is formed, and a heat treatment involving fusion between resin particles and / or fusion between resin particles and fibers is performed as necessary. This is a method of preparing a composite web.

The dry stacking method is to form a web on the screen while quantitatively mixing the fiber and the resin by using a device such as a carding machine or an aerodynamic web former to form a web on the screen. Is a method for preparing a composite web by performing heat treatment involving fusion between resin particles and / or resin particles / fibers. In order to carry out continuous production in the above double stacking method, it is recommended to employ a method in which a papermaking screen or a screen is driven endlessly by driving a conveyor belt.

The heat treatment involving fusion between resin particles and / or between resin particles and fibers (hereinafter simply referred to as heat treatment) means a heating oven heated to a predetermined temperature, a heating roll press, or the like. By passing through a heating device for a relatively short time, fusion of resin particles and / or fusion between resin particles and fibers is caused without causing a thermosetting reaction, which means a process of forming a composite of fibers and resin.

In addition to this method, a method of impregnating a non-woven fabric prepared in advance with a resin by a wet method or a dry method and then performing a treatment in the same manner as the above method to prepare a web can be effectively employed.

The thus-prepared continuous web is continuously hot press molded at a temperature not lower than the thermosetting temperature of the resin to cure the thermosetting resin, and the porosity is 50 to 95% and the thickness variation is 10%.
Adjust as follows. Here, the continuous hot press molding is a heating roll pressing machine using two or more heating rolls (or, if necessary, a combination of cooling rolls), a heating double belt (or, if necessary, It can be molded using a double belt press machine using a combination of cooling double belts or an apparatus using both machines in combination.

As another method of the present invention which is slightly different from the above, there is also a method of omitting the heat treatment at the time of forming the continuous web and performing the heat treatment and the heat curing sequentially or simultaneously in the continuous hot press forming step. Can be effectively adopted.

A part of the thermoplastic synthetic fiber constituting the continuous porous sheet may be used in combination with a heat-fusible fiber which is melted during hot pressing to improve the strength of the sheet.

[0034]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 Polyester monofilament (fiber diameter 4 denier, fiber length 5 mm)
60 parts, polyester adhesive monofilament with a softening point of 110 ° C (fiber diameter 4 mm, fiber length 5 mm) 20 parts, spherical phenolic resin (Unitika, HPF90 Univex resin UA-200) 20
Parts to an aerodynamic web former to form a composite web with a basis weight of 370 g / m ² by the dry stacking method, and using a heating roll press machine equipped with a two-stage hot press roller at 180 ° C,
Press molding was continuously performed to produce a continuous porous sheet having a thickness of about 1 mm.

The HPF value used here is JIS-
The diameter (average value of major axis and minor axis) of a disk formed by hot pressing 2 g of a sample at 165 ° C. for 1 minute under a load of 1145 kg in accordance with 5.3.2 of K-6911 ₁₉₇₉ is shown.

Example 2 Polyester monofilament (fiber diameter 4 denier, fiber length 5 mm)
A continuous porous sheet having a thickness of about 1 mm was produced from 70 parts of spherical phenol resin (Unitika, HPF90, Unibex resin UA-200, 30 parts) in the same manner as in Example 1.

Comparative Example 1 Polyester monofilament (fiber diameter 4 denier, fiber length 5 mm)
A continuous porous sheet having a thickness of about 1 mm was produced in the same manner as in Example 1 by using 80 parts and 20 parts of a polyester-based heat-adhesive fiber having a softening point of 110 ° C. (fiber diameter 4 mm, fiber length 5 mm). ..

Comparative Example 2 Polyester monofilament (fiber diameter 4 denier, fiber length 5 mm)
A continuous porous sheet having a thickness of about 1 mm was produced using 70 parts and 30 parts of a polyester-based heat-adhesive fiber having a softening point of 110 ° C. (fiber diameter 4 mm, fiber length 5 mm) in the same manner as in Example 1. ..

COMPARATIVE EXAMPLE 3 The composite web obtained in Example 1 was cut into 90 cm × 90 cm pieces, which was then heated in batch at 180 ° C. in a 6-stage hot press machine using a 1 mm thick spacer in batch type hot press molding. Do 90
A cut porous sheet having a size of cm × 90 cm and a thickness of about 1 mm was produced.

Regarding each of the above examples, that is, each of the continuous porous sheet and the cut porous sheet prepared in Examples 1 and 2 and Comparative Examples 1, 2 and 3 (hereinafter, both are collectively referred to as a porous sheet). Each characteristic shown below was measured. The definition of each characteristic value, the measurement standard, and the measurement method (condition) are as follows.

Porosity (%): flexural strength, flexural modulus (kgf / mm ² ): Japanese Industrial Standard JI
It was measured based on SK-6911.

Heat resistant bending strength, bending elastic modulus (kgf / mm ² ): 9
It was measured in an atmosphere of 0 ° C. according to Japanese Industrial Standard JIS-K-6911. Airflow resistance (mmH ₂ O): Measured at a wind speed of 3 cm / min. The results obtained by the above measurement are shown in Table 1.

[0043]

[Table 1]

Further, the porous sheets of Examples 1 and 2 and Comparative Examples 1, 2 and 3 were randomly selected at a random position and had a width of 90 cm ×
The thickness of 10 points randomly selected from a 90 cm long rectangular sample was measured with a thickness gauge. The results are shown in Table 2.
Note.

[0045]

[Table 2]

As is apparent from Table 1, the continuous porous sheets prepared in Comparative Examples 1 and 2 have no composite thermosetting resin even when pressed in the same manner as in Examples, and thus continuous porous sheets of Examples 1 and 2 are obtained. The heat resistance is significantly lower than that of the sheet.

As is apparent from Table 2, the continuous porous sheet produced by continuous pressing by the method of the present invention (Example 1,
2) is the standard deviation rate 1.0-1.2%, thickness variation 3.2-3.6%
And a standard deviation rate of 3.9 to 6.8% and a thickness variation of 1 for the cut porous sheet (Comparative Example 3) hot-press molded in batch under the same conditions.
Accuracy of thickness control is higher than 3.2 to 21.6%. Further, as is clear from the comparison between Examples 1 and 2 and Comparative Examples 1 and 2, the thermosetting resin compounded for the purpose of improving heat resistance is also effective in improving the accuracy of thickness control.

[0048]

The continuous porous sheet of the present invention has a porosity of 50-
It has a large number of continuous through holes of 95% and has a bending strength of 50.
~100 kgf / mm ^2, to the tensile strength 1000~2000kgf / mm ² Mechanical is extremely superior materials. In addition, the continuous porous sheet of the present invention has a thickness variation of 10% or less, which is far superior to the conventional product in thickness control.

The continuous porous sheet of the present invention can not only be subjected to precise punching as it is, but also can be easily subjected to shaping such as pleated bending. The continuous porous sheet of the present invention has further improved heat resistance and excellent chemical resistance as compared with conventional porous sheets made of thermoplastic synthetic fibers. Thus, the continuous porous sheet of the present invention is an optimal material for an inexpensive heat resistant air filter as described above. Besides, as it is, or as a porous material having various functions such as hydrophilicity, heat insulating property, sound absorbing property, and electrical insulating property by applying various processing / treatment, it is used for industrial, transportation equipment, electric / electronic equipment, It is a useful material that can be used for various purposes such as construction, agriculture and civil engineering.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location D04H 1/60 7199-3B 1/64 B 7199-3B D06B 21/00 D06C 7/00 Z (72 ) Inventor Keizo Terada 4- 1-3, Kutaro-cho, Chuo-ku, Osaka City Yunichika Corporation Osaka Head Office

Claims (2)

[Claims] 1. A sheet in which a thermoplastic synthetic fiber and a cured thermosetting resin are compounded, having a large number of continuous pores penetrating from one surface of the sheet to the other surface, A continuous porous sheet having a porosity of 40 to 95% and a thickness variation of 10% or less. 2. A thermoplastic synthetic fiber 50 having a fiber length of 1 to 200 mm.
~ 95% by weight and thermal fluidity measured by the Discure method 30 ~ 15
50 mm to 5% by weight of 0 mm thermosetting resin is compounded or compounded by a wet stacking method or a dry stacking method to form a continuous web, which is continuously hot pressed to cure the thermosetting resin. In addition, the method for producing a continuous porous sheet is characterized in that the porosity is adjusted to 50 to 95% and the thickness unevenness is adjusted to 10% or less.