JPH1158432A - Porous tube made of fiber-reinforced plastic and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a porous tube made of fiber-reinforced plastic and a method for manufacture thereof having high porosity, superior mechanical strength, a small pressure lose, and capable of generating fine air bubbles uniformly from the entire part of the tube wall irrespective of an amount of delivery of air during the aeration in water. SOLUTION: The porous tube is made of fiber-reinforced plastic consisting of 45-400 pts.wt. inorganic reinforcing fiber with respect to 100 pts.wt. heat melting fiber and having a porosity of 50-90 vol.%. and the 100 pts.wt. heat melting fiber and 45-400 pts.wt. inorganic fiber are dispersed in water to then be composited into a sheet, and the sheet is heated under pressure; then being cooled for compactness. Next, the compacted sheet is wound in one or more layers into a tube that is subsequently inserted in the inner part of a mold, followed by heating the sheet inserted mold for expanding the sheet, resulting in molding of a porous tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous tube made of fiber reinforced plastic and a method for producing the same, and more particularly, to a tube having a high porosity and excellent mechanical strength in a tube wall, and a pressure loss due to the tube wall. The present invention relates to a porous tube made of fiber reinforced plastic which generates fine bubbles uniformly from the entire tube wall regardless of the amount of air supply when aerated in water, and a method for producing the same.

[0002]

2. Description of the Related Art As a conventional plastic porous tube used for a diffuser tube or the like, for example, a resin porous material formed by filling a resin powder such as a polyolefin resin into a mold and molding by heating, It is known that heat-fusible fibers are accumulated in a tubular shape and heat-fused. However, any of these methods has insufficient mechanical strength and does not generate bubbles when aerated in water. It was uniform. In order to solve these problems, the present inventors have made a composite sheet made of a polyolefin resin powder and a reinforcing fiber, once melted and densified by melting the resin, and then heat-expanded in a mold composed of cylindrical tubes having different diameters. A plastic diffuser made of a plastic, which is lightweight, high-strength, high in porosity and low in pressure loss, has been proposed (JP-A-8-243369). However, when this plastic diffuser tube is aerated in water, fine bubbles can be uniformly generated when the air supply amount is relatively large, but when the air supply amount is small, the uniformity of bubble generation is low. It was not always satisfactory. As a technique to improve this point,
The present inventors have proposed, for example, an air diffuser tube in which colloidal silica is attached to the tube wall to improve the hydrophilicity (Japanese Patent Application No. 8-108).
64136). This air diffuser tube was excellent in mechanical strength, and could generate uniform and fine air bubbles from the entire wall of the tube even when the air supply amount was as small as 3 liters / minute during aeration in water.

[0003]

However, even in the above-mentioned air diffuser, there is a problem that a step of hydrophilizing the tube wall is required, and the pressure loss is slightly increased due to the attached colloidal silica. Had left a point. Accordingly, an object of the present invention is to provide a pipe having a high porosity and excellent mechanical strength, a small pressure loss due to a pipe wall, and even if the pipe wall is not particularly hydrophilic, regardless of the amount of air supply during aeration in water. An object of the present invention is to provide a fiber-reinforced plastic perforated tube capable of uniformly generating fine bubbles from the entire wall and a method for producing the same.

[0004]

Means for Solving the Problems One of the causes of non-uniform generation of air bubbles during aeration in water is that when a perforated tube is submerged in water, the pore distribution inside the tube wall becomes non-uniform. It is conceivable that the degree of intrusion of water into the inside becomes uneven. In other words, the part where water has not entered the pores inside the tube wall is
Since the airflow resistance is relatively lower than that of the area filled with water, the air flow is concentrated during aeration, so that the generation of bubbles is uneven, and the generation of large bubbles is also seen. Become. If the tube wall is hydrophilic, the unevenness of the degree of intrusion of water into the inside of the tube wall is reduced, the uniformity of bubble generation during aeration is improved, and fine bubbles are generated from the whole. However, in essence, it is thought that if the uniformity of the pore distribution inside the tube wall is improved, bubbles can be generated uniformly even if the tube wall is not particularly hydrophilic. The present inventors have conducted intensive studies based on such findings in order to solve the above-described problems,
The present inventors have found that a perforated tube as described below can solve the above-mentioned problems, and have found that such a perforated tube can be easily obtained by the method described later, and have reached the present invention. That is, the present invention firstly provides the heat fusible fiber 100
A porous tube made of fiber-reinforced plastic, comprising 45 to 400 parts by weight of reinforcing fiber with respect to parts by weight, and having a porosity in the tube wall of 50 to 90% by volume. Secondly, the gist of the present invention is a method for producing the above-mentioned porous tube made of fiber-reinforced plastic, which comprises the following four steps. (1) 100 parts by weight of heat-fusible fiber and reinforcing fibers 45 to 4
(2) heating the sheet under pressure, cooling and densifying (3) winding the densified sheet more than one layer Step of inserting a sheet made into a tubular shape into a mold (4) Step of heating a mold into which the sheet is inserted to expand the sheet and form a porous tube.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

First, the fiber-reinforced plastic porous tube of the present invention comprises a heat-fusible fiber and a reinforcing fiber.

As the heat fusible fiber in the present invention, for example, various synthetic resin fibers such as polyolefin fiber, polyester fiber and acrylic fiber, and synthetic resin composite fiber are used. In particular, a composite fiber having a core / sheath structure, in which the sheath has a lower melting point than the core and the fibers are fused together by heating, is desirable. Examples of such composite fibers include polyolefin fibers having a core of polypropylene and a sheath of modified polyethylene, and polyester fibers having a core of polyethylene terephthalate and a sheath of low-melting polyester.

As the reinforcing fibers in the present invention, fibers having high elasticity are preferable. For example, inorganic fibers such as glass fibers and alumina fibers, and carbon fibers can be used alone or in combination.

The average fiber length of the heat fusible fiber and the reinforcing fiber is preferably 1 to 50 mm, more preferably 3 to 50 mm.
２５25 mm. If the average fiber length is shorter than 1 mm, the sheet may have insufficient thermal expansion as described below, and it may be difficult to obtain a porous body. In addition, the average fiber length is 5
If it exceeds 0 mm, the thermal expansion may be insufficient in some cases, and it may be difficult to obtain sufficient uniformity between the heat-fusible fiber and the composite fiber. The average fiber diameter of the heat-fusible fiber and the reinforcing fiber is preferably 2 to 100 μm, more preferably 5 to 50 μm.

In the present invention, the mixing ratio of the heat fusible fiber and the reinforcing fiber is 45 to 400 parts by weight of the reinforcing fiber with respect to 100 parts by weight of the heat fusible fiber. If the mixing ratio of the reinforcing fibers is less than 45 parts by weight based on 100 parts by weight of the heat-fusible fiber, it tends to be difficult to secure pores inside the tube wall. If the amount exceeds 400 parts by weight, it tends to be difficult to obtain a cylindrical molded body from the sheet.

Further, the fiber-reinforced plastic porous tube of the present invention may contain various other components as required, for example, pigments or dyes for imparting color to the porous tube, antioxidants, ultraviolet stabilizers, foaming agents, It may contain chemical additives such as a foaming agent, an antifungal agent, and a bactericide.

The porosity of the fiber reinforced plastic porous tube of the present invention must be 50 to 90% by volume, preferably 60 to 85% by volume, and more preferably 65 to 80% by volume. If the porosity is less than 50% by volume, the pressure loss when ventilating in water increases, and if the porosity exceeds 90% by volume, the mechanical strength tends to be insufficient. In the present invention, the porosity refers to the theoretical density of a material constituting the fiber-reinforced plastic porous tube having no pores as Ag / cm ^3, and the apparent density of the fiber-reinforced plastic porous tube as Bg / cm ^3. Is obtained by the following equation.

[(AB) / A] × 100 (%)

[0014] In terms of mechanical strength, it is preferable to have a transverse rupture strength equal to or higher than that of a perforated tube made of a resin powder sintered compact in order to prevent breakage during handling. For example, in the case of a perforated tube having an outer diameter of 30 mm, this value is 25 kg
It is preferably f or more. The transverse rupture strength of the fiber-reinforced plastic porous tube of the present invention is represented by the load at the time of breakage, supporting both ends at intervals of 20 cm and continuously applying a load to the center.

The fiber-reinforced plastic porous tube of the present invention can be manufactured, for example, by the following method.

First, a composite slurry is prepared by dispersing and mixing 45 to 400 parts by weight of inorganic fibers in water with respect to 100 parts by weight of the heat-fusible conjugate fibers.

When dispersing and mixing the heat-fusible conjugate fiber and the inorganic fiber in water, it is preferable to use, for example, a binder. % By weight, more preferably 0.1% by weight.
2 to 5% by weight. Binders include, for example, bound anions such as acrylic polymers or styrene / butadiene polymers containing bound sulfonium, isothiouronium, pyridinium, quaternary ammonium, sulfate, or carboxylate groups. Alternatively, a polymer latex made of an organic polymer having a cationic charge and substantially insoluble in water may be used.

Also suitable as binders are starches, especially linear starches such as natural starch or corn starch, starches including enzymatically or chemically modified starches including cationic starches.

Further, when dispersing and mixing the heat-fusible conjugate fiber and the inorganic fiber in water, it is preferable to use an organic coagulant. The amount of the organic coagulant added is preferably less than about 3% by weight of the composite sheet, more preferably less than 1% by weight. Examples of the organic coagulant include aluminum polychloride (aluminum hydroxychloride), partially hydrolyzed polyacrylamide, modified cationic polyacrylamide, diallyl diethylammonium chloride, and the like. Further, for the purpose of adjusting the viscosity of a slurry in which the heat-fusible conjugate fibers and the inorganic fibers are dispersed in water, a viscosity modifier such as xanthan gum can be used.

From the slurry prepared as described above, in which the heat-fusible conjugate fibers and the inorganic fibers are uniformly dispersed and formed into a composite, a composite sheet comprising the heat-fusible conjugate fibers and the inorganic fibers is obtained. In order to form a sheet from the slurry, the wet sheet obtained by solid-liquid separation of the slurry in the manner of wet papermaking may be dried.

Next, one or two of the above composite sheets are used.
What is necessary is to heat-press the thing laminated more than one sheet, and to cool and densify it.

The temperature for hot pressing is preferably 10 to 50 ° C. higher than the melting point of the low melting point resin of the heat-fusible conjugate fiber, and the pressure is 5 to 100 kg / c.
m ² is preferable. Also, it is desirable that the cooling press be performed at a pressure similar to that of the hot press and at a temperature of 50 ° C. or less.

By performing the heating press and the cooling press in this manner, the thickness is about 0.1 to 1 mm and the weight is about 10 to 1 mm.
A dense sheet of about 0 to 1000 g / m ² can be obtained. At this time, the porosity of the sheet needs to be lower than the porosity of the finally obtained porous tube, and is preferably 50% by volume or less.

Next, the densified sheet is wound into one or more layers, preferably 2 to 20 layers to form a tube, which is inserted into a mold. In this case,
It is preferable that two sets of pipes having different diameters can be fixed with their central axes aligned. If the material is put into the inside of this mold, that is, the space between the two pipes, the material is molded. Good. The material of the mold is preferably made of metal or carbon from the viewpoints of heat resistance, thermal conductivity and mechanical strength.

The molding die into which the sheet is inserted is put into a heating tank set at a temperature higher than the melting point of the high melting point resin of the heat-fusible conjugate fiber, preferably at a temperature higher than the melting point and lower than a temperature 30 ° C. higher than the melting point. For 10 to 300 minutes. At this time, the inorganic fibers which were bent or entangled in the densified sheet and were in a compressed state are released from the compressed state by the elastic recovery force of the inorganic fibers themselves when the resin is softened by heating and return to the original state. This causes thermal expansion of the sheet. Therefore, the higher the inorganic fiber is and the higher the content of the inorganic fiber is, the larger the thermal expansion ratio becomes. Due to this thermal expansion, a porous tube conforming to the internal shape of the mold is formed.

Next, the mold is taken out of the heating tank, cooled, and then released to obtain the fiber-reinforced plastic porous tube of the present invention.

In the above manufacturing method, the weight of the sheet,
The apparent density of the perforated tube can be freely controlled by adjusting at least one of the number of layers, the number of windings, the thickness at the time of molding, that is, the internal shape of the mold, and thereby the porosity. Can be obtained in the range of 50 to 90%.

In the above method, when the material is put into the molding die, the wound sheet may be inserted.
The operation is extremely simple, and there is no fear that the packing density will be biased, which is a problem in the manufacturing method of filling the granules into the mold, and a long and uniform porous tube can be stably obtained.

[0029]

Next, the present invention will be described specifically with reference to examples.

Example 1 Xanthan gum was added to 18 liters of water with stirring.
After adding 3 g, the average fiber length is 6 mm as a reinforcing fiber.
Of glass fiber (415BB, manufactured by Owens Corning Fiberglass Co., Ltd.) was added to the water, and the mixture was stirred for 5 minutes and dispersed well.

Next, to this dispersion were added 40 g of heat-fusible conjugate fibers (manufactured by Daiwabo, NBF) having a core / sheath structure, a sheath portion of modified polyethylene and a core portion of polypropylene, and 0.8 g of an acrylic polymer latex. After that, 98 g of a cationic flocculant (Betz Laboratories, trade name: Betz 1260) having a concentration of 0.41% by weight is gradually added to cause coagulation, whereby the heat-fused fiber and the reinforcing fiber are uniformly dispersed. A composite slurry was obtained.

A wet sheet subjected to solid-liquid separation was obtained from the slurry using a sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.), and then the obtained sheet was lightly compressed and dried to obtain 280 g / m2. ^A composite sheet comprising a heat-fusible composite fiber and a glass fiber having a basis weight of ² was obtained. At this time,
The glass fiber was 120 parts by weight based on 100 parts by weight of the heat-fusible conjugate fiber.

The obtained composite sheet was weighed at 20 kgf / cm ^2.
After heating at 120.degree. C. under pressure of 40.degree. C., compression and densification was performed by pressurizing and cooling at 40.degree.

Next, the above-mentioned densified sheet was sewn with an outer diameter of 18 mm.
It is wound about 8 times along the outer peripheral surface of a stainless steel cylinder with a diameter of 30 mm, inserted into a stainless steel cylindrical mold with an inner diameter of 30 mm, and kept in a hot-air circulation oven set at a temperature of 200 ° C. for 30 minutes. Then, it is cooled to room temperature and removed from the stainless steel mold to obtain an outer diameter of 30 mm and an inner diameter of 18 mm.
A porous tube made of fiber-reinforced plastic and having a smooth surface made of a heat-fusible conjugate fiber having a thickness of 2 mm and glass fiber was molded. The density of this porous tube is 0.38 g / cm ³ and the porosity is 7
It was calculated to be 3%. Further, when the bending strength of a fiber-reinforced plastic perforated tube having a length of 30 cm was measured, it was found to be 30 cm.
kgf.

Example 2 Xanthan gum 0.1 was added to 18 liters of water while stirring.
After adding 3 g, the average fiber length is 6 mm as a reinforcing fiber.
Of water (415BB, manufactured by Owens Corning Fiberglass Co., Ltd.) was added to the water, and the mixture was stirred for 5 minutes and dispersed well.

Next, 32 g of a heat-fusible conjugate fiber (manufactured by Daiwabo Co., Ltd., NBF) having a core / sheath structure, a modified polyethylene resin and a polypropylene core, and 0.8 g of an acrylic polymer latex were added to the dispersion. After that, 98 g of a cationic flocculant (Betz Laboratories, trade name: Betz 1260) having a concentration of 0.41% by weight was gradually added to cause coagulation, whereby the heat-fused fiber and the reinforcing fiber were uniformly dispersed. A composite slurry was obtained.

Using a sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.), a wet sheet obtained by solid-liquid separation was obtained from the above slurry, and the obtained sheet was lightly compressed and dried to give a basis weight of 300 g / m ² . A composite sheet comprising a heat-fusible composite fiber having the following and a glass fiber was obtained. At this time, the glass fiber was 1 to 100 parts by weight of the heat-fusible conjugate fiber.
It was 85 parts by weight.

The obtained composite sheet was weighed at 20 kgf / cm ^2.
After heating at 120.degree. C. under pressure of 40.degree.

Next, the above-mentioned densified sheet was coated with an outer diameter of 18
Around the outer circumference of a 7 mm stainless steel cylinder, it is wound about 7 times, inserted into a 30 mm inner diameter stainless steel cylindrical mold, and kept in a hot air circulation oven set at a temperature of 200 ° C. for 30 minutes. After cooling to room temperature and removing the mold from the mold, a porous tube made of fiber-reinforced plastic having a smooth surface and composed of a heat-fusible conjugate fiber and a glass fiber having an outer diameter of 30 mm and an inner diameter of 18 mm was formed. The density of this porous tube was 0.36 g / cm ³ , and the porosity was calculated to be 77%. Further, when the transverse rupture strength of a fiber-reinforced plastic porous tube having a length of 30 cm was measured, it was 27 kgf.

COMPARATIVE EXAMPLE 1 Xanthan gum was added to 18 liters of water while stirring.
After adding 3 g, the average fiber length is 6 mm as a reinforcing fiber.
Of glass fiber (415BB, manufactured by Owens Corning Fiberglass Co., Ltd.) was added to the water, and the mixture was stirred for 5 minutes to be well dispersed.

Next, 45 g of a high-density polyethylene resin powder (manufactured by Sumitomo Seika) and 0.8 g of an acrylic polymer latex were added to the dispersion, and a 0.41% by weight cation coagulant (manufactured by Betz Laboratories) was added. , Product name: Betz 126
0) Slurry was obtained by adding 98 g gradually to cause aggregation.

A wet sheet subjected to solid-liquid separation was obtained from the slurry using a sheet machine (manufactured by Kumagai Riki Kogyo Co., Ltd.), and then the obtained sheet was lightly compressed and dried to obtain 270 g / m2. ^A composite sheet comprising a resin powder having a basis weight of ² and glass fibers was obtained. At this time, the glass fiber was 100 parts by weight based on 100 parts by weight of the resin powder.

The obtained composite sheet was weighed at 20 kgf / cm ^2.
After heating at 170 ° C. under pressure of 40 ° C., compression and densification was performed by pressurizing and cooling at 40 ° C.

Next, the above-mentioned densified sheet was treated with an outer diameter of 18
It is wound about 8 times along the outer peripheral surface of a stainless steel cylinder of 2.5 mm, inserted into a stainless steel cylindrical mold of 30 mm inside diameter, and kept for 30 minutes in a hot air circulation oven set at a temperature of 150 ° C. After cooling to room temperature and removing from the mold, a porous tube made of high-density polyethylene resin and glass fiber and having a smooth surface and made of fiber reinforced plastic and having an outer diameter of 30 mm and an inner diameter of 18 mm was formed. The density of this porous tube is 0.37 g / cm ³ and the porosity is 73
%. An average particle size of 0.1 μm
Is impregnated with a dispersion obtained by dispersing 44 g of anhydrous silica particles in 956 g of water, and then dried at 60 ° C. to impregnate the silica particles by 3% by weight to obtain a porous tube having a hydrophilic tube wall. Was.

(Performance Test) The pressure loss of the fiber-reinforced plastic porous tubes obtained in Examples 1, 2 and Comparative Example 1 was measured by the following method, and the state of generation of bubbles was examined.

One end of the 30 cm long fiber reinforced plastic perforated tube obtained in Example 1, Example 2 and Comparative Example 1 was sealed, and a hose was connected to the other to make the perforated tube portion 20.
Submerged at a depth of 60 cm in a 1 m ³ water tank filled with water at a temperature of ℃, and air was blown in at a rate of 40 liters / minute using an air blower. Fine bubbles were generated uniformly and in large quantities. Each discharge pressure at this time was measured, and the pressure loss was calculated by the following equation.

Discharge pressure (mmAq) = effective water depth (600 mmAq)
+ Pressure loss (mmAq) + Piping resistance (460 mmAq)

As a result, the pressure loss in the porous tubes of Example 1, Example 2 and Comparative Example 1 was 150 mmAq and 19 mm, respectively.
The values were 0 mmAq and 350 mmAq.

Further, even when the amount of air supplied was reduced to 3 liters / minute, fine air bubbles were uniformly generated from the entire tube wall in the porous tubes of Example 1, Example 2 and Comparative Example 1.

From the above, the perforated tubes of Examples 1 and 2 have a smaller pressure loss than the perforated tubes of Comparative Example 1 and fine air bubbles from the entire tube wall regardless of the amount of air supply. It is clear that this is a perforated tube capable of uniformly generating.

[0051]

The porous tube made of fiber reinforced plastic according to the present invention has a high porosity and excellent mechanical strength, has a small pressure loss due to the tube wall, and is capable of supplying water when aerated in water even if the tube wall is not particularly hydrophilic. Regardless of the air volume, fine air bubbles can be uniformly generated from the entire tube wall. This is because the fiber-reinforced plastic porous tube of the present invention has a structure in which the heat-fusible conjugate fiber and the inorganic fiber are firmly bonded by fusion of the heat-fusible conjugate fiber, and the pore distribution in the tube wall. It is thought that the uniformity of the size and the size have been improved. Further, the production method of the present invention can easily produce a fiber-reinforced plastic porous tube having the above characteristics. Further, the fiber-reinforced plastic perforated tube of the present invention is suitable as a diffuser tube for sewage treatment and fish culture, and a filter tube for liquid filtration.

Continued on the front page (72) Inventor Tetsuya Sahara 4-3-1 Kutarocho, Chuo-ku, Osaka-shi, Osaka Unitika Co., Ltd.

Claims (2)

[Claims] 1. A fiber-reinforced plastic made of 45 to 400 parts by weight of reinforcing fiber with respect to 100 parts by weight of heat-fusible fiber, and having a porosity of 50 to 90% by volume in a tube wall. Perforated tube. 2. The method for producing a fiber-reinforced plastic perforated tube according to claim 1, comprising the following four steps. (1) 100 parts by weight of heat-fusible fiber and reinforcing fibers 45 to 4
(2) heating the sheet under pressure, cooling and densifying (3) winding the densified sheet more than one layer Step of inserting a sheet made into a tubular shape into a mold (4) Step of heating a mold into which the sheet is inserted to expand the sheet and form a porous tube.