JPH0386529A - Porous composite sheet and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a porous composite sheet excellent not only in surface smoothness but also in dynamic characteristics and hydrophilicity by adding specific fine particles to a composite sheet obtained from staple fibers and a binder resin. CONSTITUTION:A web is formed by mixing particles of a thermosetting phenol resin whose resin elongation prescribing heat flowability of 3 - 15cm and stable fibers having a length of 1 - 30mm and subsequently pressed and heated to form a porous composite sheet. Subsequently, silica fine particles having a particle size of 1mum or less are added to the porous composite sheet. The whole of this sheet has properties such that a void ratio is 40 - 80%, bending strength is 50kg/cm<2> or more, modulus of elasticity in flexure is 1,000kg/cm<2> or more, a water absorbing speed is 30mm/10sec or more and water absorbancy is 60wt.% or more.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention has excellent surface smoothness, hydrophilicity, mechanical properties, etc.
The present invention relates to a porous composite sheet suitable for use as a water absorption board, humidity control board, water evaporation board, etc., and a method for manufacturing the same.

(Conventional technology) Conventionally, polyethylene, polypropylene, polystyrene,
Porous sheets with continuous pores formed by sintering and forming fine particles of thermoplastic polymers such as polymethyl methacrylate and polyacrylonitrile into sheet shapes are known.
These porous sheets are widely used as diffuser plates, filter media, and the like.

These porous sheets are hydrophobic due to the properties of the thermoplastic polymer used as their material, so their uses have been limited.

Therefore, the present inventors developed a method for manufacturing a porous molded body by sintering and molding fine particles of a thermosetting phenolic resin, which is a phenolic resin having a certain degree of hydrophilicity and a specific thermofluidity. Previously proposed (Japanese Unexamined Patent Publication No. 63-63727
Publication No.). However, the porous sheet obtained by the above method does not necessarily have sufficient mechanical properties such as 9 bending strength because the fine particles of phenolic resin are simply sintered and fused together by point adhesion. Furthermore, the porosity is limited to about 40% at most, making it difficult to reduce the weight of the porous body.

Therefore, in order to solve these problems, the present inventors developed a porous composite sheet with excellent mechanical properties and air permeability, and a method for manufacturing the same, made from two-reinforced fibers and a specific thermosetting phenolic resin. proposed (Japanese Patent Application Laid-open No. 1-165427)
. However, although the porous composite sheet proposed by this proposal can secure a certain amount of water retention, there is a problem in that a sufficient water absorption rate cannot be obtained.

(Problem to be solved by the invention) The present inventors aimed to solve such problems.

Previously, we proposed a porous composite sheet with a large porosity, excellent mechanical properties such as bending strength despite the large porosity, hydrophilicity, and especially a fast water absorption rate, and a method for manufacturing the same (Patent Application No. 1983- No. 114369). However, although the porous composite sheet proposed by this proposal has significantly improved water absorption properties, there remains a problem in the surface smoothness of the sheet that needs to be improved.

Therefore, the object of the present invention is to have excellent surface smoothness.

It is an object of the present invention to provide a porous composite sheet having excellent hydrophilicity and mechanical properties, and a manufacturing method for easily obtaining such a porous composite sheet.

(Means for Solving the Problems) In order to solve these problems, the present inventors have conducted extensive research and found that by attaching specific fine particles to a composite sheet obtained from short fibers and binder resin, two surfaces can be The present invention was achieved by discovering that a porous composite sheet with excellent smoothness, mechanical properties, and hydrophilicity can be obtained.

That is, the porous composite sheet of the present invention has a fiber length of l.
A sheet in which short fibers of m11 to 30 mm+ and a hardened binder are integrated, and has continuous pores penetrating from one side of the sheet to the other, and the porosity of the entire sheet is 4.
0~80%1 Bending strength is 50kg/cat or more.

It is characterized by having a flexural modulus of 1000 kg/caf or more, a water absorption rate of 30 mm/10 seconds or more, and a water absorption rate of 60% by weight or more.

In addition, the manufacturing method of the present invention conforms to the Japanese Industrial Standard JIS-6911, which specifies thermal fluidity, in accordance with 5. 3.
2. The elongation of the resin based on [molding material (disc flow)] is 3
A web is formed by mixing thermosetting phenolic resin powder with a diameter of cm to 15 cm and short fibers with a fiber length of 1 mm to 30 mm, and then pressurized and heated to harden the phenolic resin to form a porous material. After forming a composite sheet,
A feature of this method is that silica-based fine particles having a particle size of 1 μm or less are attached to this porous composite sheet.

Hereinafter, one aspect of the present invention will be explained in detail.

First, the porous composite sheet of the present invention consists of short fibers and binder, and the short fibers and hardened binder are integrated.

Here, the short fibers include polyethylene terephthalate fibers and low melting point modified polyester fibers.

Synthetic fibers made of organic polymers such as polyamide fibers such as nylon 6, nylon 66, and nylon 46, polyolefin fibers such as polypropylene and polyethylene, and phenolic resin fibers such as Kynol fiber (trade name of Nippon Kynol ■), glass fiber, and carbon. Examples include those made of inorganic fibers such as fibers.

The fiber length of the short fibers used in the present invention is 1 mm to 30+
u+, preferably 3 to 25 mm, more preferably 5 to 10 mm. When the fiber length exceeds 30++ us, sufficient surface smoothness cannot be obtained. On the other hand, when the fiber length is less than 1 mm, the effect as a reinforcing material cannot be sufficiently exhibited.

Moreover, the fineness of the fiber is preferably 1 to 20 deniers.

Next, the binder in the present invention is, for example, a thermosetting resin having a melting point or softening point of 150° C. or lower.

Alternatively, thermoplastic resin is used. These resins are used in the form of powder or granules. this house.

Preferred binders include phenolic resins. Phenol resins include thermosetting phenol/aldehyde resins obtained by reacting phenols and aldehydes, and thermosetting nitrogen-containing phenol/aldehyde resins obtained by reacting phenols, aldehydes, and nitrogen-containing compounds. Examples include aldehyde resins.

Next, one sheet of the present invention has continuous pores that penetrate from one side of the sheet to the other side. Such continuous pores are bent through the voids of the short fibers that make up the sheet, penetrating from one surface to the other, and penetrating relatively straight from one surface to the other. Examples include things.

In the present invention, the presence or absence of continuous pores is determined as follows. First, a diameter of 10 mm is made from a composite sheet with a thickness of 2 mm.
When a disk is cut out and air is flowed through this disk at a rate of INl/min, the pressure loss is 2000 mmH2O.
The material is judged to have continuous pores in the following cases.

It means that the smaller the pressure loss when the air is flowing, the higher the proportion of continuous pores in the composite sheet. Further, the above pressure loss also represents the degree of air permeability of the sheet. In the sheet of the present invention, the pressure loss is preferably 1000 mm H20 or less, particularly preferably 300 mm H20 or less.

Furthermore, the composite sheet of the present invention has a porosity (%) of 40 to
It is 80%.

Here, the porosity (%) is the ratio of the pore volume to the total volume of the composite sheet expressed as a percentage. Specifically, the porosity (%) is measured as follows.

First, the dry weight W (g) and volume V (caf
) to measure. Next, the sheet is powdered, the true density ρ (g/cnf) of the composite sheet is measured, and the porosity (%) is calculated using the following formula.

If the porosity is less than 40%, the proportion of continuous pores will decrease, resulting in a decrease in air permeability, which is not preferable. On the other hand, if the porosity exceeds 80%, the mechanical properties such as the bending strength of the composite sheet tend to decrease, which is not preferable.

Next, the composite sheet of the present invention has a bending strength of 50 kg/
ctl above JJ and bending elastic modulus is 1000kg/cuf
Has above JJ. The higher the bending strength, the better.2
Usually, 50 to 300 kg/ctl is suitable. If the bending strength is less than 50 kg/cut, it is not preferable because there is a risk of damage. The higher the flexural modulus, the better; however, a modulus of flexural elasticity of 1,000 to 10,000 kg/cd is usually appropriate. Flexural modulus is 1000kg/c++
If it is less than f, the rigidity tends to be insufficient, which is not preferable.

Here, 1 bending strength and bending elastic modulus are JIS-72
03,,, □ Measured based on the regulations of [Hard plastic bending test method].

Furthermore, the composite sheet of the present invention has a water uptake rate, that is, a water absorption rate of 30 mm/10 seconds or more.

The water absorption rate is measured in the following manner. First, from a composite sheet with a thickness of 1 to 5 mm, two widths of 20
Cut out a board with a length of 150 mm. next.

This board is stood vertically in the long plane direction, the lower end 30 mm is immersed in water, the rising water level in the board is read 10 seconds after this time, and that value is taken as the water suction speed. If the water absorption rate is less than 30++ on/10 seconds, the transpiration rate becomes slow when used in a water evaporation plate, etc., which is not preferable.

Further, the composite sheet of the present invention has a water absorption rate of 60% by weight or more.

Here, the water absorption rate (% by weight) indicates the percentage of water that the composite sheet can retain when it is sufficiently immersed in water.

Specifically, the water absorption rate (weight %) is measured as follows. First, the dry weight W1 (g) of the composite sheet is measured. Next, after fully immersing the sheet in water, take it out of the water and cut a drop to find the weight Wz (
g) is measured and calculated from the linear equation.

If the water absorption rate is less than 60% by weight, it is not preferable because the amount of water retained will decrease when used for water absorption plates and the like.

The porous composite sheet of the present invention described above is preferably manufactured by the manufacturing method of the present invention.

In the manufacturing method of the present invention, first, the elongation of the resin is determined based on the Japanese Industrial Standard JIS-6911, which specifies thermal fluidity, 5°3.2 [molding material (disc flow)]. A web is formed by mixing 3 cm to 15 cm of thermosetting phenol resin powder and short fibers. To form the web, devices such as well-known carding machines or aerodynamic web formers may be used.

Further, after forming the web, by passing it through a calender roll, a mat having a desired thickness can be obtained.

The above Japanese Industrial Standard JIS-6911□, 7.
5.3.2 [Molding material (disc flow)] is a test method that evaluates the thermal fluidity of a resin by the diameter of a disc-shaped molded product obtained by compression molding the resin. However, specifically, 5 g of phenolic resin was placed in a conical shape on a mold kept at a temperature of 160±3°C.

A disk-shaped molded product is compression molded by applying a load of 2500 kg f for 60 seconds to this phenolic resin, and the diameter of the obtained disk-shaped molded product (the average value of the major axis and minor axis is the diameter of the disk) ) is the elongation of the resin.

The phenolic resin preferably used in the present invention is:

The elongation of the resin measured by this test method is 3co+~
It is a thermosetting phenolic resin in the range of 15 cm.

In the production method of the present invention, if a thermofluid phenolic resin with a resin elongation of less than 3 cm is used, it may be difficult to form the desired porous composite sheet, or even if it can be formed, the mechanical There is a tendency to obtain composite sheets with insufficient properties. On the other hand, the elongation of the resin is 15 cm.
When using a phenolic resin with thermal fluidity exceeding There is.

The particle size of the phenolic resin powder used in the present invention is preferably spherical particles with a diameter of 50 to 500 μm or irregularly shaped particles of this size, but 100 to 3 μm in diameter.
A particle size of about 00 μm is more preferable. Further, it is also possible to use a cylindrical or ellipsoidal powder.

The amount of resin mixed with short fibers is 10 to 90% by weight, preferably 30 to 70% by weight based on the weight of the composite sheet obtained.
is within the range of If the amount of the resin is less than IO weight %, it may be difficult to obtain sufficient mechanical properties, whereas if it exceeds 90 weight %, the porosity will decrease and there will be fewer continuous pores. .

Air permeability tends to decrease.

Also, when forming the web, alumina, silica, talc, and carbon black are added as necessary.

Filler 9 such as graphite, molybdenum disulfide, fluororesin powder, etc. A pigment, a fungicide, a flame retardant, etc. may be added as a coloring agent.

Next, press and heat the web or mat.

The uncured thermosetting phenol resin attached to the short fibers is cured. Pressurization and heating are preferably carried out at a pressure of 1 to 10 kg/cd and a temperature of 140 to 180°C for 1 to 20 minutes, particularly at a pressure of 3 to 6 kg/cnf and a temperature of 150 to 180°C.
It is preferable to carry out the heating at 170°C for 3 to 10 minutes.

Next, nine silica-based fine particles having a particle size of 1 μm or less are attached to the porous composite sheet that has been cured by applying pressure and heating. The silica-based fine particles are impregnated by impregnating the porous composite sheet with an aqueous dispersion of silica-based fine particles.

This is preferably done by drying.

Here, examples of the silica-based fine particles include fine particles of anhydrous silicic acid or hydrous silicic acid. If silica-based fine particles with a particle size larger than 1 μm are used, the amount of impregnation may occur, or the bonding force with the sheet may become weak, making it impossible to obtain a sufficient amount of impregnation, which tends to reduce the water wicking speed and water absorption rate. Undesirable.

In the manufacturing method of the present invention, the silica-based fine particles are impregnated and attached to the porous sheet as an aqueous dispersion as described above, and the silica-based fine particles are used as a solvent for dispersing the silica-based fine particles, that is, as a dispersion medium. Outside the water, ethanol and methanol.

Solvents such as acetone and methyl ethyl ketone may also be used. Among these dispersion media, an aqueous dispersion medium is particularly preferred because it has good affinity for the porous sheet, is inexpensive, and is easy to handle and dry.

The concentration of the dispersion liquid of the silica-based fine particles is 1 to 40% by weight.
It is preferable that If the concentration is 1% by weight,
As the amount of silica fine particles attached to the porous composite sheet described above is reduced, sufficient hydrophilicity may not be obtained.
On the other hand, if the concentration exceeds 40% by weight, impregnated carbon may be produced during impregnation into the porous composite sheet, and the silica fine particles may scatter after drying, which is not preferable. In addition, in this dispersion of silica-based fine particles, methyltrimethoxysilane, methyltriethoxysilane,
Phenyltrimethoxysilane.

T-glycidyloxypropyltrimethoxysilane, γ
-methacryloxypropyltrimethoxysilane, γ-(
A silane coupling agent such as N-β-aminoethyl)aminopropyltrimethoxysilane or T-aminopropyltrimethoxysilane may be contained.9 In order to improve the stability of the dispersion, cationic, Anionic surfactants, nonionic surfactants, etc. may also be contained.

The amount of silica-based fine particles attached to the porous composite sheet cured by pressure and heating is 0.01 to 15% by weight, preferably 0.1 to 10% by weight, based on the weight of the porous composite sheet.
is within the range of If the amount of the silica-based fine particles is less than 0.01% by weight, a sufficient water absorption rate may not be obtained; on the other hand, if it exceeds 15% by weight, the silica-based fine particles may scatter after drying. There is.

In order to more firmly fix the silica-based fine particles, it is preferable to heat-treat the porous composite sheet after attaching the silica-based fine particles. Such heat treatment is performed at a temperature of 60 to 110°C.
It is preferable to carry out the reaction at a temperature of 10 to about 60 minutes.

Thus, it consists of short fibers and phenolic resin.

A sheet made of short fibers and hardened phenolic resin, with continuous pores penetrating from one side of the sheet to the other, with a porosity of 40 to 80% as a whole, and a bending strength of 9. is 50kg/c++f or more 1 flexural modulus is 1
000kg/c++f or more, water suction speed is 30+n
+n/10 seconds or more, a porous composite sheet with a water absorption rate of 60% by weight or more and good surface smoothness is formed. usually.

The surface of the composite sheet changes due to the above pressure and heating.

It is coated with the thermoset phenolic resin except for the portion where the continuous pores penetrate.

The phenolic resin preferably used in the present invention is 1
For example, it can be produced by reacting a phenol or novolac resin with an aldehyde in an aqueous medium in the presence of a suspension stabilizer and a basic compound. Such phenols include phenol derivatives in addition to phenol. Examples of phenol derivatives include m-alkylphenol substituted with an alkyl group having 1 to 9 carbon atoms, 0-alkylphenol, p-alkylphenol, specifically m-cresol.

Examples thereof include p-tert-butylphenol, 0-propylphenol, resorcinol, bisphenol A, and halogenated phenol derivatives in which part or all of the hydrogen atoms of their benzene nucleus or alkyl group are substituted with chlorine or bromine. Note that the phenols are not limited to these, and any other compound having a phenolic hydroxyl group can be used. Moreover, two or more types of these phenols can also be used.

The novolac resin used to produce the above phenolic resin is produced by reacting the aforementioned phenols with aldehydes in a molar ratio of 1 to 1 or less in the presence of an acidic catalyst such as oxalic acid, hydrochloric acid, or sulfuric acid. It is a thermoplastic resin having a linear molecular structure obtained by the process, and is a solid resin with a melting point of 70 to 100°C as measured by the ring and ball method. Such novolac resins can be easily produced manually as commercial products.

Examples of the aldehydes used to produce the phenol resin include formaldehyde, acetaldehyde, formalin, paraformaldehyde, furfural, and the like.

The amount of aldehydes used relative to phenols is 1
1 to 2 in molar ratio. Particularly preferred is 1.1 to 1.4. Further, the amount of aldehydes used relative to the novolac resin is preferably 50% by weight or less.

Further, examples of the suspension stabilizer used to produce the above-mentioned phenolic resin include substantially water-insoluble inorganic salts and water-soluble organic polymers.

Examples of substantially water-insoluble inorganic salts include:

Calcium fluoride, magnesium fluoride, strontium fluoride, etc. are preferred. The substantially water-insoluble inorganic salts may be added directly to the reaction system during the reaction for producing the phenol resin.

Two or more water-soluble inorganic salts capable of producing such substantially water-insoluble inorganic salts may be added.

Examples of water-soluble inorganic salts that can produce substantially water-insoluble inorganic salts include at least one selected from the group consisting of fluoride, calcium fluoride, and ammonium fluoride; calcium; Magnesium, strontium chloride.

At least one selected from the group consisting of sulfates and nitrates
Examples include seeds.

Examples of water-soluble organic polymers include gum arabic, gum gatsuchi, and hydroxyguar gum.

Partially hydrolyzed polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose.

Examples include soluble starch and agar. Such water-soluble organic polymers can be used alone or in combination.

Further, a substantially water-insoluble inorganic salt and a water-soluble organic polymer may be used in combination.

Examples of basic compounds include 9, for example, caustic soda.

Caustic potash, calcium hydroxide, magnesium hydroxide, aqueous ammonia, hexamethylenetetramine.

Dimethylamine, diethylenetriamine, polyethyleneimine, etc. may be mentioned, and aqueous ammonia or hexamethylenetetramine is particularly preferred.

Such basic compounds can be used alone or in combination.

The aqueous medium used to produce the phenolic resin used in the present invention may be water containing an organic solvent, in addition to water. The amount of such aqueous medium used is such that the solid content of the produced phenolic resin is 20 to 70% by weight, particularly 30 to 70% by weight.
It is preferable to use it in an amount of 60% by weight.

The reaction temperature for producing the phenolic resin in the present invention is preferably 70 to 100°C, particularly 80 to 95°C.

Further, the reaction time is preferably 20 to 120 minutes, particularly 40 to 90 minutes.

After completion of the reaction, one reactant is cooled to 40° C. or lower, solid and liquid are separated by filtration or centrifugation, and further washed with water and dried.

(Example) The present invention will be specifically explained below using examples.

Reference Examples 1 to 4 200 g of phenol in 3 flasks of 11, 3
7% by weight formaldehyde aqueous solution (formalin) 20
g.

Add 70 g of water, 18 g of hexamethylenetetramine, and 6.7 g of calcium chloride with stirring to make a homogeneous solution, and add 10% by weight of sodium fluoride to this solution while stirring.
After adding 32 g of the aqueous solution, the contents were evaporated to 8
The mixture was heated to 5°C and stirring was continued while maintaining this temperature.

After the temperature of the contents reached 85°C, the contents were heated at 50%
Each sample was sampled in g. After cooling each sample to 30° C., 0.3 I2 of water was added. Next, after removing the supernatant liquid, the microspherized resin in the lower layer was washed with water, air dried, and further dried at 50 to 60°C under reduced pressure of 5 mmHg or less to obtain a phenol resin with an average particle size of about 70 μm. Ta. These phenolic resins are called resins A, B, C and D, respectively.
shall be.

Reference Examples 5 to 7 3200 g of novolac resin [#6000 (melting point 70 to 76°C) manufactured by Mitsui Toatsu Chemical Co., Ltd.] in an IJ glass flask
.

150 g of water and 4 g of gum arabic were added, and the contents were heated to 95° C. while stirring twice. A solution of 20 g of hexamethylenetetramine dissolved in 150 g of water was added to this,
Stirring was continued while maintaining the temperature at 95°C.

After adding an aqueous solution of hexamethylenetetramine.

50 g of the contents were each sampled at 10 minutes, 60 minutes, and 150 minutes. After cooling each sample to 30°C, 0.31% water was added, and the resin microspheres were separated by filtration using filter paper, then washed with water, air-dried, and further divided into 5 mm
Dry at 35° C. for 24 hours under vacuum below Hg.

A phenol resin having an average particle diameter of 200 μm was obtained. These phenolic resins are referred to as resins E, F, and G, respectively.

Examples 1-4. Comparative Examples 1 to 3 The elongation of the resins A to G was measured based on the JIS regulations. The results are shown in Table 1.

By mixing 10 kg each of the above resins A-G and 20 kg of polyethylene terephthalate short fibers (average fiber length 5 mm, average fineness 4 denier) in a carding machine to form a web, and passing it through a calender roll set at 150 ° C. Thickness 10+++m, basis weight 800g/
A mat with a width of 50 cm was obtained.

These were pressed and heated at a pressure of 1 kg/cut for 5 minutes using a press molding machine preheated to a temperature of 170° C., thereby curing the phenol resin and obtaining a composite sheet with a thickness of 2 mm.

Furthermore, 20 g of finely powdered silicic anhydride with a particle size of 0.1 μm was added to 1 part of water.
An aqueous dispersion of finely powdered silica particles was obtained by dispersing the mixture in 80 g.

The cured sheet was impregnated with the finely powdered silicic anhydride dispersion and then dried at 100° C. for 20 minutes to obtain a composite sheet to which the finely powdered silicic anhydride was attached. The amount of finely powdered silicic anhydride impregnated at this time was in the range of 0.5 to 3% by weight.

These sheets are made to correspond to the phenolic resins A to G, respectively, to form composite sheets A + to G.

Comparative Example 4 A composite sheet was obtained in the same manner as in Example 2, except that silicic anhydride having a particle size of 2.5 μm was used as the fine powder silica particles. This sheet is referred to as a composite sheet H. The amount of finely powdered silicic anhydride impregnated at this time was 0.03% by weight.

Comparative example 5 As short fibers of polyethylene terephthalate.

A composite sheet was obtained in the same manner as in Example 2, except that short fibers having an average fiber length of 40 mm and an average fineness of 4 denier were used.

This sheet is referred to as a composite sheet L.

Table 2 shows the results of measuring the surface smoothness, porosity, bending strength and bending elastic modulus of Composite Sea) A and -1, as well as bending strength and bending elastic modulus based on the above JIS regulations.

Note that 1. Surface smoothness is the result of a sensitivity test.

○ Smooth feel X Rough feel As is clear from Table 2, the porosity of the composite sheets A1 to I was all 60 to 65%. but.

Regarding bending strength, + A In B l + C In
The composite sheets of E In F ItH+, It had sufficient bending strength for practical use, but the composite sheets) D, , G,
It was not practical.

Next, composite sheet A cut out into a disk with a diameter of 10n+m
Air was flowed through I+ B, C, F, E I+ H at a rate of lNff/min, and the pressure loss was measured by the method described above to examine the presence or absence of continuous pores.

In the case of comparison composite sheet A1, INji! /m
The pressure loss when air was flowed at a rate of in was so large that it could not be measured. This indicates that the composite sheet AI does not have continuous pores.

Moreover, as is clear from Table 3, two composite sheets according to the present invention B1, CI, F1. E 1 and comparative example 4
The composite sheet H1 had a low pressure loss of 300 or less when air was flowed at a rate of 1Nll1...in, and had continuous pores. Furthermore, when the composite sheets of Examples 1 to 4 and Comparative Example 4 according to the present invention were examined, most of the pores were continuous.

Next, composite sheets were cut into 9 boards with a width of 20 mm and a length of 150 mco.
The water uptake rate and water absorption rate of H. The results are shown in Table 4.

As is clear from Table 4, in the case of the comparative composite sheet H1, the water absorption rate is 35% by weight and the water absorption speed is 5mm.
/10 seconds, indicating poor hydrophilicity. However, the composite C according to the present invention) B,, CI.

The water absorption rate of El and F+ was 65 to 80% by weight, and the water absorption rate was 35 to 65 mm/10 seconds, indicating sufficient hydrophilicity.

(Effects of the Invention) The porous composite sheet of the present invention is formed by integrating short fibers and binder resin, so it has excellent mechanical properties such as 9 bending strength and 1 bending modulus, and particularly has a high bending modulus. It shows excellent rigidity.

Moreover, since short fibers are used, surface smoothness is good.

Furthermore, since it has a high porosity, it is lightweight and easy to handle. Furthermore, since it has continuous pores, it has excellent breathability. Furthermore, since the porosity is high, there are many continuous pores. Furthermore, it has a high water absorption rate and a high water absorption rate.

Therefore, it can be used as an air diffuser plate, a filter medium, a water absorption plate, a water evaporation plate 2, etc., and especially for air conditioners,
It can be suitably used as a humidity control plate for electric refrigerators, refrigerated vending machines, etc. and a drain water evaporation plate, and also as a molding material for ceramic slurry molding, etc., which particularly requires the above-mentioned mechanical properties. It can also be suitably used and can be used in a wide range of applications.

Furthermore, since the manufacturing method of the present invention uses a thermosetting phenolic resin having a specific thermal fluidity, the above porous composite sheet can be easily obtained by a simple operation.

Claims (2)

[Claims] (1) A sheet in which short fibers with a fiber length of 1 mm to 30 mm and a hardened binder are integrated, and has continuous pores penetrating from one side of the sheet to the other, and the porosity of the entire sheet is low. 40-80%, bending strength 50kg/cm^
2 or more, a flexural modulus of 1000 kg/cm^2 or more, a water absorption rate of 30 mm/10 seconds or more, and a water absorption rate of 60% by weight or more. (2) Japanese Industrial Standard JIS-K-6 that defines thermal fluidity
911_1_9_7_9 5.3.2 [Molding material (disc flow)] Thermosetting phenolic resin powder with resin elongation of 3 cm to 15 cm and fiber length of 1 mm to 30 cm
mm short fibers to form a web, and then pressurized and heated to harden the phenolic resin to form a porous composite sheet. A method for producing a porous composite sheet with excellent surface smoothness, characterized by impregnating silica-based fine particles.