JPH0517249B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an air diffuser plate, a filter material, a water absorption plate, a humidity control plate,
The present invention relates to a porous composite sheet with excellent air permeability and mechanical properties suitable as a mold material, etc., and a method for manufacturing the same. (Prior Art) Conventionally, a method of manufacturing a porous sheet having continuous pores by sintering and forming fine particles of organic polymers such as polyester, polypropylene, polystyrene, polymethyl methacrylate, and polyacrylonitrile into a sheet has been known. These porous sheets are widely used as air diffusers, filter media, and the like. These porous sheets have a problem in that they have poor heat resistance and solvent resistance due to the characteristics of the organic polymer used as the material, so their uses have been limited. Therefore, the present inventors sintered and formed fine particles of thermosetting phenolic resin, which is a phenolic resin with excellent heat resistance and solvent resistance and has specific thermal fluidity, to create a porous molded body. We first proposed a manufacturing method (Japanese Patent Application No. 61-208782,
63-63727). (Problems to be Solved by the Invention) However, the porous sheet obtained by the above method only has sintered fine particles of phenolic resin and is fused by point bonding, so it has a high bending strength. ,
Mechanical properties such as flexural modulus were not necessarily sufficient. Furthermore, the porosity is limited to about 40% at most, making it difficult to reduce the weight of the porous body. The present invention is intended to solve the above-mentioned problems, and its purpose is to have a large porosity, excellent mechanical properties such as bending strength and bending elastic modulus, and excellent air permeability despite the large porosity. An object of the present invention is to provide a porous composite sheet with excellent properties and a manufacturing method that can easily manufacture such a sheet. (Means for Solving the Problems) In order to solve these problems, the present inventors have conducted extensive research and found that the mechanical properties and air permeability of reinforcing fibers and a specific thermosetting phenolic resin have been improved. It was discovered that an excellent porous composite sheet could be obtained, and the present invention was achieved. That is, the porous composite sheet of the present invention is made of reinforcing fibers and a phenolic resin, and is a sheet in which the reinforcing fibers and the hardened phenolic resin are integrated. It has pores, the porosity of the entire sheet is 40-80%, the bending strength is 50Kg/cm2 ^or more, and the bending elastic modulus is
It is characterized by being 2000Kg/cm ² or more. In addition, the manufacturing method of the present invention allows the sheet made of reinforcing fibers to have thermal fluidity of Japanese Industrial Standards JIS-K-
6911 ₁₉₇₉ , 5.3.2 [Molding material (disc flow)] After impregnating with an aqueous dispersion of thermosetting phenolic resin with a resin elongation of 3 to 15 cm, and squeezing the dispersion with a squeezing roller, It is characterized in that it is dried and then pressurized and heated to harden the phenolic resin. The present invention will be explained in detail below. First, the porous composite sheet of the present invention is made of reinforcing fibers and a phenolic resin, and the reinforcing fibers and the hardened phenolic resin are integrated. Examples of reinforcing fibers include synthetic fibers made of organic polymers such as polyester fibers, polyamide fibers, and polyolefin fibers, and inorganic fibers such as glass fibers and carbon fibers. These materials may be in any sheet-like form, such as nonwoven fabrics, woven fabrics, or knitted fabrics made of long or short fibers. Among these reinforcing fibers, polyester fibers, particularly polyethylene terephthalate fibers, are preferred, and their form is preferably a long fiber nonwoven fabric.
The preferable range of the fiber density, i.e., the basis weight, of the above-mentioned fiber sheet varies depending on the type of fiber, form, etc., but in the case of a long fiber nonwoven fabric of polyethylene terephthalate fiber, the fiber density is preferably about 100 to 700 g/ ^m2 . . If the fiber density of the fiber sheet, which is a reinforcing fiber, is too high, it may be difficult to impregnate the inside of the sheet with the phenolic resin, which will be described later.On the other hand, the fiber density of the fiber sheet is too low. This is not preferable because the mechanical strength such as bending strength of the composite sheet decreases. In addition, the phenol resin in the present invention includes a thermosetting phenol/aldehyde resin obtained by reacting phenols and aldehydes,
Thermosetting nitrogen-containing phenols obtained by reacting phenols, aldehydes, and nitrogen-containing compounds.
Examples include aldehyde resins. Next, the sheet of the present invention has continuous pores that penetrate from one side of the sheet to the other side. Such continuous pores may penetrate from one surface to the other by bending through the voids in the reinforcing fibers that make up the sheet, or they may penetrate 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. In other words, a 10 mm diameter disk is cut out from a 1 mm thick composite sheet, and 1N is applied to this disk.
If the pressure loss is 1000 mmH ₂ O or less when air is flowed at a rate of /min, it is determined that the material has continuous pores. The smaller the pressure loss when the air is passed, the higher the proportion of continuous pores in the composite sheet. In addition, the above pressure loss is
It also represents the degree of breathability of the sheet. In the sheet of the present invention, the above pressure loss is 500 mmH ₂
It is preferably less than or equal to O, particularly preferably
It is 200mmH ₂ O or less. Furthermore, the composite sheet of the present invention has a porosity (%)
is required to be between 40 and 80%. Here, the porosity (%) is the ratio of the pore volume to the total volume of the composite sheet expressed as a percentage. The porosity (%) is specifically measured as follows. First, the dry weight W (g) and volume V (cm ³ ) of the composite sheet are measured. Next, the sheet is powdered and the true density of the composite sheet is ρ (g/cm ³ ).
is measured, and the porosity (%) is calculated using the following formula. Porosity (%) = (1-W/ρ×V)×100 If the porosity is less than 40%, the proportion of continuous pores will decrease, resulting in a decrease in air permeability. This is not preferable because the amount of water retained in this case decreases. On the other hand, if the porosity exceeds 80%, the mechanical properties such as bending strength and bending elastic modulus 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/cm ² or more, and the bending elastic modulus is 2000 Kg/cm ² or more. The higher the bending strength, the better, but normally 50 to 300 kg/cm ² is suitable. If the bending strength is less than 50 kg/cm ² , it is not preferable because there is a risk of damage. Further, the higher the bending elastic modulus, the better, but usually about 2,500 to 4,000 kg/cm ² is suitable. Flexural modulus is 2000Kg/cm ²
If it is less than that, it is not preferable because deflection is likely to occur. Here, the bending strength is determined by JIS-K-7203 ₁₉₈₂ [Bending test method for hard plastics], and the bending modulus is determined by JIS-K-7203 1982 [Bending test method for hard plastics].
K-7113 ₁₉₈₁ [Tensile test method for plastics]. The above porous composite sheet of the present invention is preferably manufactured, for example, by the manufacturing method of the present invention. In the production of the present invention, first, a sheet made of reinforcing fibers has thermal fluidity that meets Japanese Industrial Standards JIS-K.
-6911 ₁₉₇₉ , 5.3.2 [Molding material (disk type flow)] The resin is impregnated with an aqueous dispersion of thermosetting phenolic resin having a resin elongation of 3 to 15 cm. 5.3.2 of the above Japanese Industrial Standard JIS-K-6911 ₁₉₇₉
[Molding material (disc flow)] is a test method that evaluates the elongation of resin by the diameter of a disc-shaped molded product obtained by compression molding the resin. , 5g of phenolic resin was placed in a conical shape on a mold kept at a temperature of 160°C ± 3°C, and a load of 2500 kgf was applied to this phenolic resin for 60 seconds to compression mold a disc-shaped molded product. The diameter of the obtained disc-shaped molded product (the average value of the major axis and minor axis is the diameter of the disc) is taken as the elongation of the resin. The phenolic resin used in the present invention is a thermosetting phenolic resin whose resin elongation measured by the above test method is in the range of 3 to 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 is possible to form it, the mechanical There is a tendency to obtain composite sheets with insufficient properties. On the other hand, when using a phenolic resin with thermal fluidity that allows the elongation of the resin to exceed 15 cm, the surface portion of the porous sheet tends to be fused under pressure and heat, and therefore, the porous sheet with continuous pores tends to be fused. It tends to be difficult to obtain composite sheets. Such phenolic resin is impregnated into reinforcing fibers as an aqueous dispersion as described above, and examples of solvents or dispersion media for dispersing such resin include water, ethanol, methanol, methyl ethyl ketone, ethylene glycol, etc. . Among these dispersion media, aqueous dispersion media are particularly preferred because they are inexpensive and easy to handle. The concentration of the above phenolic resin dispersion is 5 to 50
It is preferable to set it as weight%. If the concentration is less than 5% by weight, a stable dispersion may not be obtained due to weight settling, while if the concentration exceeds 50% by weight, impregnation spots tend to occur when impregnating reinforcing fibers. There is. The amount of resin impregnated into the reinforcing fibers is 10 to 90% by weight, preferably 10 to 90% by weight, based on the weight of the composite sheet obtained.
It ranges from 30 to 70% by weight. If the amount of the above resin is less than 10% by weight, it may be difficult to obtain sufficient mechanical properties;
If it exceeds , the porosity tends to decrease, the number of continuous pores decreases, and the air permeability tends to decrease. In addition, fillers such as alumina, silica, talc, carbon black, graphite, molybdenum disulfide, and fluororesin powder, and colorants are added to the dispersion medium of the phenolic resin that is impregnated into the sheet made of reinforcing fibers. Dyes and pigments may also be added. Next, in the present invention, the dispersion liquid is squeezed using a squeezing roller to remove the excess dispersion liquid impregnated into the reinforcing fiber sheet. Here, the squeezing rate of the squeezing roller is determined by taking into consideration the concentration of the dispersion liquid and the amount of resin to be attached to the reinforcing fiber sheet. Next, the reinforcing fiber sheet to which the uncured resin is attached is dried. Such drying is preferably carried out at a temperature of 80 to 110°C for about 10 to 30 minutes. After the drying, the uncured thermosetting phenol resin attached to the reinforcing fiber sheet is cured by applying pressure and heating. Pressurization and heating are preferably carried out at a pressure of 1 to 10 kg/cm ² and a temperature of 140 to 180°C for 1 to 20 minutes, particularly at a pressure of 3 to 6 kg/cm ² and a temperature of 150 to 170°C.
It is preferable to carry out the heating for 3 to 7 minutes. Thus, it is a sheet made of reinforcing fibers and phenolic resin, in which the reinforcing fibers and hardened phenolic resin are integrated, and has continuous pores penetrating from one side of the sheet to the other, and the pores of the entire sheet are A porous composite sheet having a bending strength of 40 to 80%, a bending strength of 50 Kg/cm ² or more, and a flexural modulus of 2000 Kg/cm ^{2 or} more is formed. Usually, by applying the pressure and heating, the surface of the composite sheet is coated with the thermosetting phenolic resin except for the areas where the continuous pores pass through. The phenolic resin preferably used in the present invention can be produced, for example, by reacting a phenol or a novolak resin with an aldehyde in an aqueous medium in the presence of a suspension stabilizer and a basic compound. Examples of such phenols include phenol and phenol derivatives. Examples of phenol derivatives include m-alkylphenol, o-alkylphenol, p-alkylphenol substituted with an alkyl group having 1 to 9 carbon atoms, specifically m-cresol,
Examples thereof include p-tert-butylphenol, o-propylphenol, resorcinol, bisphenol A, and halogenated phenol derivatives in which part or all of the hydrogen atoms of the benzene nucleus or alkyl group of these 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-mentioned phenolic resin is prepared by adding the above-mentioned phenols in the presence of an acidic catalyst such as oxalic acid, hydrochloric acid, or sulfuric acid.
It is a thermoplastic resin with a linear molecular structure obtained by reacting aldehydes at a molar ratio of 1:1 or less, and has a melting point of 70 to 70 as measured by the ring and ball method.
It is a solid resin at 100℃. Such novolak resins are easily available as commercial products. Further, examples of the aldehydes used for producing the above-mentioned phenolic resin include formaldehyde, acetaldehyde, formalin, paraformaldehyde, furfural, and the like. The molar ratio of aldehydes to phenols is preferably 1 to 2, particularly 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.
Preferred examples of the substantially water-insoluble inorganic salts include calcium fluoride, magmium fluoride, and strontium fluoride. The method for adding such substantially water-insoluble inorganic salts is as follows:
Although such substantially water-insoluble inorganic salts may be directly added to the reaction system, two or more water-soluble inorganic salts that can produce such substantially water-insoluble inorganic salts may be added during the reaction for producing the phenolic resin. Salts may be added. Examples of the water-soluble inorganic salts that can produce substantially water-insoluble inorganic salts include at least one selected from the group consisting of sodium fluoride, calcium fluoride, and ammonium fluoride, and calcium, magnesium, and stolon. Examples include at least one selected from the group consisting of chloride, sulfate, and nitrate of thiium. Examples of water-soluble organic polymers include gum arabic, gum gum, hydroxyguar gum, partially hydrolyzed polyvinyl alcohol, hydroxyethyl cellulose, carboxymethyl cellulose, 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 caustic soda,
Examples include caustic potash, calcium hydroxide, magnesium hydroxide, ammonia water, hexamethylenetetramine, dimethylamine, diethylenetriamine, and polyethyleneimine, with ammonia water or hexamethylenetetramine being 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
It is preferable to use it in an amount of up to 70% by weight, particularly 30 to 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. In addition, the reaction time is 20 to 120 minutes,
Particularly preferred is 40 to 90 minutes. After the reaction is completed, the reaction product is cooled to 40° C. or lower, solid and liquid are separated by filtration or centrifugation, and further washed with water and dried. (Examples) Hereinafter, the present invention will be specifically explained using examples. Reference examples 1 to 4 200g of phenol in the 3-necked flask from 1, 37
Weight% formaldehyde aqueous solution (formalin)
20 g, water 70 g, hexamethylenetetramine 18 g and calcium chloride 8.4 g were added with stirring to make a homogeneous solution, and after adding 40 g of a 10% by weight aqueous solution of sodium fluoride to this solution with stirring, 60 g
The contents were heated to 85° C. over a period of minutes and stirring was continued while maintaining this temperature. After the temperature of the contents reaches 85℃, 40 minutes for 10 minutes.
50 g of the contents were sampled at 90 minutes, 90 minutes, and 150 minutes. Each sample at 30℃
After cooling to 0.3 ml 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 heated for 50 minutes under reduced pressure of 5 mmHg or less.
Drying at ~60°C yielded a phenolic resin with an average particle size of approximately 50 microns. These phenolic resins are referred to as resins A, B, C and D, respectively. Reference Examples 5 to 7 Into the glass flask from step 1, add 200 g of Novolac resin [Mitsui Toatsu Co., Ltd. #6000 (melting point 70 to 76°C)].
g, 150 g of water, and 4 g of gum arabic were added, and the contents were heated to 95° C. while stirring. A solution of 20 g of hexamethylenetetramine dissolved in 150 g of water was added to this, and stirring was continued while maintaining the temperature at 95°C. After adding the 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, add 0.3 ml of water, filter the resin into microspheres using filter paper, and then wash with water.
Air dry and further dry at 35℃ for 24 hours under reduced pressure of 5 mmHg or less.
After drying for hours, a phenolic resin with an average particle size of about 200 microns was obtained. These phenolic resins are referred to as resins E, F, and G, respectively. Examples 1 to 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.

[Table] 100g of each of the above resins A to G was redispersed in 400g of water, and then milled in a stainless steel ball mill.
Aqueous dispersions of resins A to G were obtained by wet milling for a period of time. These are respectively referred to as phenolic resin aqueous dispersions A ₁ to G ₁ . A long-fiber nonwoven fabric of polyethylene terephthalate fibers with a basis weight of 400 g/m ² was impregnated with the above phenolic resin aqueous dispersion A ₁ to G ₁ , and after squeezing this dispersion with a squeezing roller, it was dried at 100°C for 20 minutes. A polyethylene terephthalate nonwoven fabric to which uncured phenolic resin was adhered was obtained. The amount of phenol resin deposited at this time was in the range of 200 to 240 g/m ² . These were pressed and heated at a pressure of 1 kg/cm ² for 5 minutes using a press molding machine preheated to a temperature of 160° C., thereby curing the phenolic resin and obtaining a composite sheet with a thickness of 1 mm. These sheets are made to correspond to the phenolic resin aqueous dispersions _A1 to _G1 , respectively, to form composite sheets _A2 to _G2 . Table 2 shows the results of measuring the porosity, bending strength, and bending elastic modulus of the composite sheets A ₂ to G ₂ based on the above-mentioned JIS regulations.

[Table] As is clear from Table 2, composite sheet A ₂ ~
The porosity of _G2 was 60 to 65% in all cases. However, regarding bending strength and bending modulus, A ₂ ,
The composite sheets of B ₂ , C ₂ , E ₂ , and F ₂ had sufficient bending strength and bending modulus for practical use, but the composite sheets
D ₂ and G ₂ were not suitable for practical use. Next, the composite sheet was cut out into a disc with a diameter of 10 mm.
Air was flowed through A ₂ , B ₂ , C ₂ , E ₂ , and F ₂ at a rate of 1 N/min, and the pressure loss was measured by the method described above to examine the presence or absence of continuous pores and air permeability.

[Table] For comparison composite sheet A ₂ , 1N/min
When air was flowed at a rate of , the pressure loss was so large that it could not be measured. This means that the composite sheet
_A2 does not have continuous pores, indicating poor air permeability. However, as is clear from Table 2, the composite sheets B ₂ , C ₂ , F ₂ ,
_E2 has a low pressure loss of 130 or less when air is flowed at a rate of 1N/min, has continuous pores, has sufficient ventilation, and has ventilation suitable for practical use. It had a sexual nature. Further, when the composite sheets of Examples 1 to 4 according to the present invention were examined, most of the pores were continuous. (Effects of the Invention) The porous composite sheet of the present invention is formed by integrating reinforcing fibers and hardened phenolic resin, and therefore has excellent mechanical properties such as bending strength and bending elastic modulus. Therefore, in addition to air diffusers, filter media, etc., it can be used in molds and the like that particularly require the above-mentioned mechanical properties, and can be used in a wide range of applications. Moreover, because of its high porosity, it is lightweight and
It is easy to handle. Furthermore, since it has continuous pores, it has excellent breathability. In addition, since the porosity is high, there are many continuous pores, and together with the hydrophilic properties of phenol resin, it can retain moisture, making it suitable for use in humidity control boards for air conditioners, electric refrigerators, etc. . Furthermore, since the production 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 (1)

[Scope of Claims] 1. A sheet made of reinforcing fibers and a phenolic resin, in which the reinforcing fibers and the hardened phenolic resin are integrated, and having continuous pores penetrating from one surface of the sheet to the other surface. , the porosity of the entire sheet is 40
~80%, a bending strength of 50 Kg/cm ² or more, and a flexural modulus of 2000 Kg/cm ² or more. 2. The porous composite sheet according to claim 1, wherein the reinforcing fibers are a nonwoven fabric of polyester fibers. 3 A sheet made of reinforcing fibers is made of a thermosetting phenolic resin whose thermal fluidity is 3 to 15 cm in elongation based on 5.3.2 [Molding material (disc flow)] of the Japanese Industrial Standard JIS-K-6911 ₁₉₇₉ . impregnated with an aqueous dispersion of
A method for producing a porous composite sheet, which comprises squeezing the dispersion liquid with a squeezing roller, drying it, and then applying pressure and heating to harden the phenolic resin.