JPH0551449B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a synthetic resin composite pipe. Prior Art and Its Problems Thermoplastic resin pipes such as polyvinyl chloride and polyethylene are widely used for construction and civil engineering works such as water and sewage pipes, electrical piping, and drainage pipes, as well as for agricultural purposes. However, these thermoplastic resin tubes are sensitive to heat and deform when exposed to high temperatures, and are also melted and burnt by flames. On the other hand, metal pipes commonly used for these applications have excellent heat resistance and flame resistance, but have poor insulation properties, and in the event of a fire, the contents inside the pipe, the pipe support, or the surrounding area may be damaged. It has disadvantages such as transmitting high heat and causing the spread of fire, being heavy, having poor workability, and being corrosive. Therefore, it is possible to provide thermosetting resin pipes that are relatively lightweight and have high heat resistance, flame resistance, corrosion resistance, and heat insulation properties for these applications, but conventional molding methods are expensive and have poor physical properties. However, it has not been put to practical use in these applications due to some problems. That is, long tubes of thermosetting resin are generally molded by the plunger extrusion method (for example, JP-A-48-83155, Plastics vol. 25, No. 3 p47). In the case of this method, the extrusion pressure in the mold part is high, and since the extrusion is performed intermittently, it is difficult to obtain a uniform molded product, and the productivity is low. Due to these circumstances, a molding method using a die and screw type extruder has been developed (for example, Japanese Patent Application Laid-open No. 54-23611), but with this method, resin tends to stagnate in the extrusion device, causing localized problems. There are problems in that the curing reaction progresses quickly, or that the curing reaction progresses rapidly due to slight changes in pressure or temperature, making it difficult to carry out continuous and safe molding.
In addition, when using any of the extrusion methods described above, only a tube with low strength in the circumferential direction is obtained, and as a result, it is weak against internal and external pressure and easily cracks in the axial direction of the tube when subjected to impact. There were practical problems such as: The reason for this is that in conventional extrusion methods, molten resin is guided into the mold and shaped and hardened while moving along the flow path within the mold, during which time the resin moves in the extrusion direction. In other words, it is thought that this is because only the tube axis direction exists, and the resin, filler, etc. are oriented in that direction. Means for Solving the Problems The present inventors have solved such problems and have improved heat resistance,
As a result of various studies in order to obtain an inexpensive synthetic resin pipe that is lightweight and impact resistant with excellent flame resistance, corrosion resistance, etc., we have developed an extruded thermosetting resin pipe in which the resin and/or filler is oriented in irregular directions. However, it was discovered that the compressive strength in the axial direction and the direction perpendicular to the tube is well balanced, and as a result, it is strong against internal and external pressure and exhibits excellent properties against impact. It has been found that by coating with resin, a composite tube with further improved heat resistance, flame resistance, impact resistance, etc. can be obtained. Furthermore, by using a screw having a smooth part at the tip, shaping the smooth part to the extent that it can maintain its own shape after extrusion, and coating the extruded thermosetting resin tube with thermosetting resin. The inventors have discovered that these synthetic resin composite pipes can be obtained and have arrived at the present invention. That is, the present invention uses an extruder equipped with a screw having a feeding section, a compression section, a measuring section, and a smooth section, and a cylinder having a constant inner diameter, and between the screw smooth section and the inner wall of the cylinder. Shaped, the resin and/or filler is oriented in irregular directions, the ratio of the compressive strength in the direction perpendicular to the tube axis and the compressive strength in the tube axis direction is 0.4 to 1.5, and the breaking stress is 400 to 700 Kg/cm This is a synthetic resin composite pipe made by coating the surface of a thermosetting resin pipe (No. ² ) with a thermosetting resin. The composite tube of the present invention preferably uses an extrusion molding machine with a built-in screw, and heats the surface of a thermosetting resin tube obtained by shaping and curing the tip of the extrusion molding machine to the extent that it can maintain its own shape after extrusion. It is obtained by coating with a curable resin, for example, patent application 1988-
It is manufactured by coating the surface of a thermosetting resin tube obtained by the method described in No. 51526 with a thermosetting resin. That is, a screw having a smooth part at the tip is used, the thermosetting resin is shaped and extruded in the smooth part to the extent that it can maintain its own shape, and the surface is coated with the thermosetting resin. A specific method for this is so-called filament winding, in which a band-shaped cloth or filament impregnated with a thermosetting resin is wound around the surface of the thermosetting resin tube extruded by the above method, and then hardened. Method 1: Wrap a thermosetting resin-impregnated cloth around the thermosetting resin tube, place it in a mold, and heat it.
The second method is to pressurize and harden, and the third method is to sandwich the thermosetting resin tube between three heated rolls, and while rotating, wrap a cloth impregnated with thermosetting resin and heat harden it. can be adopted. The thermosetting resin tube that forms the inner layer of the composite tube of the present invention is formed by extrusion molding, particularly by using an extrusion molding machine with a built-in screw, and shaping and hardening it at its tip to the extent that it can maintain its own shape after extrusion. It is obtained by That is, the thermosetting resin material introduced into the extruder is heated and melted while passing through the screw supply section and the compression section, passes through the measuring section, moves from the tip of the flight of the measuring section to a smooth part in a spiral shape, and there Due to frictional resistance with the inner wall of the cylinder, the gap created by the screw flight is narrowed, and finally pressure fusion is achieved. The resin is then hardened and shaped while traveling through the smooth section, and is extruded from the tip of the cylinder into a continuous tube. During this time, the resin moves while being subjected to shear in the direction generally along the screw groove from the supply section to the metering section, so the resin itself and the filling are not oriented in a particularly fixed direction with respect to the extrusion direction of the tube. After the resin is oriented in an irregular direction without any bending and transitions to a smooth part, the resin itself and the filler are oriented in a well-balanced manner in the axial direction and circumferential direction of the tube as the curing progresses. It is considered that the balance between compressive strength in the direction perpendicular to the tube axis is improved. To further explain the above-mentioned molding method, the extruder used is not only a single screw extruder, but also a twin screw extruder or a multi-screw extruder, the tip of which eventually converges into a single screw. Any extruder that can be used can be used. As for the internal structure of these extruders that can be used, there is no problem in providing a deaeration hole or a special kneading structure between the supply section and the measuring section at the tip of the extruder. A typical screw is a screw having a smooth portion at its tip, and this screw includes, for example, a supply section, a compression section, and a metering section.
The smooth section may be of a type such that it begins where the supply section ends, where the compression section ends, or in the middle of the metering section. Further, the screw diameter of the smooth portion can be adjusted to match the desired inner diameter of the molded product separately from the diameter of the screw bottom portion of the portion having flights. The L/D of the screw is usually 7 to 40, preferably 10 to 35, more preferably 15 to 25, and the compression ratio is 1.0.
~5.0, preferably 1.2-4.0, more preferably 1.5
~3.0, the length of the smooth part at the screw tip is 1D~
5D, preferably 2D~10D, more preferably 2D~
You can select from the range of 7D as appropriate. If the length of the smooth portion at the screw tip is less than 1D, the molded product obtained after extrusion will be deformed and it will be difficult to continuously obtain a good molded product. Furthermore, if the length of the smooth portion is 15D or more, the molding pressure will be too high and it is not practical in terms of the mechanical strength of the extruder. The compression ratio of the screw and the length of the smooth part are subject to various restrictions depending on the gap between the screw and the cylinder in the smooth part, in other words, the thickness of the molded product, the extrusion speed, and the characteristics of the material used. . The larger or smaller the compression ratio of the screw and the length of the smooth portion, the larger or smaller the back pressure applying function. If the back pressure is too large, excessive kneading will occur in the portions having flights, resulting in excessive heat generation and hardening of the material, which is undesirable. On the other hand, if the back pressure is too low, compression filling and kneading of the material will become insufficient, which is also not preferred. Adequate back pressure is necessary for compaction filling and proper kneading of the material. The larger or smaller the gap between the screw and the cylinder in the smooth part, the lower or higher the extrusion speed, the lower or higher the viscosity of the material used, the lower or higher the curing speed of the material used, the lower or higher the extrusion speed. , the compression ratio of the screw and the length of the smooth part need to be large or small. The temperature settings for each part of the extruder will naturally vary depending on the combination of the characteristics of the material used, the compression ratio of the screw, the gap between the smooth part of the screw and the cylinder, the length of the smooth part, the extrusion speed, etc. The temperature setting of the cylinder portion corresponding to the smooth portion is usually in the range of 50 to 200°C, preferably 60 to 150°C. Therefore, if the set temperature is below 50℃,
Since the curing reaction of the resin does not proceed sufficiently, it tends to be difficult to obtain a good molded product.On the other hand, thermosetting resins commonly used at temperatures up to 200°C are sufficiently thermoset, so there is no need to increase the temperature above that temperature. Normally, in the extrusion molding method for thermosetting resins, the resin is heated and melted in a cylinder and shaped into the final shape after being introduced into the mold via an adapter. Because the flow path of the resin changes in a complicated manner, such as the flow being constricted by an adapter and then re-expanded around the mandrel fixed by a spider, it is easy for the resin to stagnate, causing localized curing reactions to occur. A slight change in pressure or temperature can cause problems such as rapid curing reactions. In addition, in order to overcome the resistance caused by the complicated flow paths and extrude the resin while preventing stagnation, a large extrusion pressure is required and a special extrusion device is required. However, when using such a molding method, the extrusion speed is at most about 30 cm/min, and it is difficult to obtain a product with good roundness and thickness distribution. According to the above method, the smooth part of the screw and the cylinder part in that area play the role of a mold, and the resin flow path is only the gap between the cylinder and the screw, so there is no stagnation of the resin and only local hardening occurs. It does not cause rapid curing reactions due to reactions, changes in pressure, or temperature. In addition, since the screw smooth part, which corresponds to the mandrel in the mold in general molding methods, rotates, the frictional resistance between the hardened resin and the metal part is relatively small, and the extrusion pressure can be applied using a normal screw extruder. The pressure obtained is sufficient. When using such a method, an extrusion speed of 80 cm/min can be easily obtained. The orientation of the resin and filler of the tube forming the inner layer of the composite tube of the present invention described above can be observed using, for example, an electron microscope. Fig. 1 is an electron micrograph of a cross section in the extrusion direction of a phenolic resin tube extruded by a conventional extrusion method (plunger type), and Fig. 2 is an electron micrograph of a cross section taken in the direction perpendicular to the extrusion direction. , 3 and 4 are electron micrographs of respective cross sections of a phenolic resin pipe, which is one of the thermosetting resin pipes of the present invention. While it is clear in Figures 1 and 2 that the glass fibers are oriented in the tube axis direction,
In FIGS. 3 and 4, it can be seen that the fibers are not oriented in a particular direction, but are oriented irregularly. Table 1 below shows the compressive strength A in the direction perpendicular to the pipe axis, the compressive strength B in the direction of the pipe axis, the ratio of A/B, and the results of the water pressure test.As can be seen from this table, the results of the conventional method Compared to the pipe with a small A/B ratio of 0.37, which tends to cause vertical cracks, the pipe of the present invention has a large A/B ratio of 0.4 to 1.5, making it strong against internal pressure without causing vertical cracks. Recognize. In the present invention, the compressive strength in the tube axis direction is
A test (compressive strength test) according to sections 5, 19, and 5 of JIS-K-6911 is performed, and the compressive strength in the direction perpendicular to the pipe axis is expressed as the strength when the pipe is broken (including cracks). Strength refers to the strength of a pipe when it breaks when tested in accordance with sections 5 and 6 of JIS-K-6741 (flattening test). The thermosetting resin pipe obtained in this way has excellent heat resistance and is resistant to oils such as heavy oil, gasoline, and kerosene, organic solvents such as alcohol, ketones, esters, and aromatic hydrocarbons, acids, and alkalis. By using phenolic resin, melamine resin, xylene resin, etc. as the molding material, it does not spread, does not drop, and almost maintains its original shape even when exposed to flame. It has excellent flame resistance properties such as not emitting toxic gases, and the resin and/or filler is oriented in a well-balanced manner in the extrusion direction of the tube and in the circumferential direction, so it has excellent strength in the extrusion direction of the tube and in the direction perpendicular to it. The result is a good balance of properties, resulting in excellent pressure resistance. Examples of thermosetting resins used in the present invention include phenolic resins, melamine resins, urea resins, unsaturated polyester resins, epoxy resins, silicone resins, allyl resins, xylene resins, and aniline resins. Among them, phenolic resin, melamine resin and urea resin are preferably used. The thermosetting resin used in the present invention may contain fillers, mold release agents, thickeners, colorants, dispersants, blowing agents, or polymerization initiators commonly used in the molding of thermosetting resins, as necessary. A curing agent, a curing accelerator, a polymerization inhibitor, etc. can be added. In the present invention, organic or inorganic fibrous substances such as wood flour, cotton, nylon fiber, vinylon fiber, glass fiber, carbon fiber, metal fiber, etc. For example, the total amount with the filler mentioned above is 20 to 80
It can also be added in higher quantitative ranges, such as weight percent. The thermosetting resin pipe molded by the above-mentioned method can be produced by the above-mentioned first method, second method or third method.
A composite tube is obtained by being coated with a thermosetting resin by the method described above. To explain these using diagrams, Fig. 5 is a diagram showing an outline of the first method, in which a thermosetting resin tube is extruded by an extruder 3 using a screw 2 having a smooth portion 1 at the tip. 4 is heated by a post-cure device 5 as necessary to complete curing. then
It is guided into the FRP molding machine 6 and wrapped with a cloth or roving impregnated with a thermosetting resin, and while it continues to pass through a heating device 7, the hardening of the outer layer is completed and the composite tube 8 is formed. FIG. 6 is a diagram showing an outline of the second method, in which the thermosetting resin tube 4 obtained by the above-mentioned extrusion method is
A cloth 9 impregnated with a thermosetting resin is wound around the tube, and it is placed in a mold 10 shown in FIG. 7, and heated under pressure to harden the outer layer, thereby obtaining a composite tube. Figure 8 is the third
This is a diagram showing an outline of the method, in which a thermosetting resin tube 4 obtained by the above-mentioned extrusion molding method is sandwiched between three heated rolls 11, and a cloth or roping impregnated with a thermosetting resin is inserted. A composite tube is obtained by winding and curing. In any of the above methods, the temperature for curing the thermosetting resin that forms the outer layer varies depending on the material used and the heating time, but usually
The temperature is appropriately selected from the range of 100 to 200°C. Examples of the thermosetting resin forming the outer layer of the composite pipe of the present invention include the above-mentioned resins, but liquid ones are preferably used, such as phenol resin (resol resin), unsaturated polyester resin, and epoxy resin. . Further, the various additives mentioned above, such as thickeners, mold release agents, colorants, curing agent accelerators, dispersants, etc., can be added to these resins. In addition, as the cloth, filament, and roving used for forming the outer thermosetting resin layer, inorganic and organic cloth, filament, and roving, such as glass cloth, glass roving, canvas, and paper, are used. The thickness of the thermosetting resin layer to be formed is also appropriately selected depending on the purpose and required physical properties, but is usually within a range equal to the thickness of the thermosetting resin forming the inner layer. Function: The composite pipe according to the present invention is made of thermosetting resin for both the inner and outer layers, and has excellent heat resistance and flame retardancy.
The inner layer is stronger than thermosetting resin tubes obtained by conventional extrusion molding methods, and the outer layer is reinforced with cloth, filaments, rovings, etc., so it has excellent impact resistance. When manufactured by the first method or the like, a long tube with a desired length can be obtained. The synthetic resin composite pipe of the present invention described above has excellent heat resistance, flame retardance, and impact resistance, and is therefore useful as, for example, electrical equipment or construction and civil engineering materials. The present invention will be further explained below using reference examples and production examples. Reference example 1 An extruder with a diameter of 3 mm and L/D = 22 has a diameter of 26 mm at the tip that follows the measuring section at the bottom of the screw, which has a diameter of 26 mm.
A screw with a compression ratio of 2.0 and a smooth part with a length of 105 mm (3.5D) is used to continuously form a pipe using phenolic resin (manufactured by Nippon Oil Seal Co., Ltd., trade name Logiyas RX6684) as the molding material. Extrusion molded. The temperature inside the cylinder is C ₁ (0 to 2D) = water cooling,
C ₂ (3D ~ 10D) = 80℃, C ₃ (11D ~ 18D) = 100℃,
C ₄ (19D to 22D) was set at 120°C and extrusion molding was performed at a screw rotation speed of 35 rpm.
A pipe with a wall thickness of 2.0 mm was obtained. Reference Example 2 A pipe was extrusion-molded using the same extrusion apparatus as in Reference Example 1, using a phenol resin (manufactured by Nippon Gosei Kako Co., Ltd., trade name: Nikalite 950-J) as a molding material. The temperature of each part of the cylinder is C ₁ = water cooling, C ₂ = 80
℃, C ₃ = 110℃, C ₄ = 120℃, molding was performed under the conditions of screw rotation speed 35 rpm, outer diameter 30 mm,
A pipe with a wall thickness of 2.0 mm was obtained. Reference Example 3 Using the same extrusion apparatus as in Reference Example 1, a pipe was extrusion-molded using phenol resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name PM-795J) as a molding material. The temperature of each part of the cylinder is C ₁ = water cooling, C ₂ = 80℃,
Molding was carried out under the conditions of setting C ₃ = 105°C and C ₄ = 120°C and a screw rotation speed of 35 rpm to obtain a pipe with an outer diameter of 30 mm and a wall thickness of 2.0 mm. Reference Example 4 Using the same extrusion equipment as Reference Example 1, melamine resin (manufactured by Otalite Co., Ltd., product name ON) was used as the molding material.
-600) was used to continuously extrude the pipe. The temperature of each part of the cylinder is C ₁ = water cooling, C ₂ = 85℃,
Molding was carried out under the conditions of setting C ₃ = 115°C and C ₄ = 130°C and a screw rotation speed of 35 rpm to obtain a pipe with an outer diameter of 30 mm and a wall thickness of 2.0 mm. Evaluation Results: The results of the compressive strength (direction perpendicular to the pipe axis, direction of the pipe axis, and ratio thereof) and water pressure test of the pipe obtained in the above manufacturing example were as shown in Table 1. Production Example 1 Using the same extrusion equipment and extrusion conditions as Reference Example 3,
A pipe was extruded using phenolic resin (PM-795J) as a molding material, and then passed through a post-cure device and heated at 180° C. for 2.5 minutes to complete curing.
Next, the pipe was introduced into the FRP molding machine, wrapped with glass roving impregnated with unsaturated polyester (manufactured by Mitsui Toatsu Chemical Co., Ltd., trade name: Estar R-2110), and then heated at 120°C for 10 minutes using a heating device. After hardening, the outer diameter is 32 mm, consisting of an inner layer of 2 mm and an outer layer of 1 mm.
A composite tube was obtained. Production Example 2 A 1 m long pipe obtained in Reference Example 1 was coated with resol resin (manufactured by Hitachi Chemical Co., Ltd., product name: Hytanol).
A glass cloth impregnated with 2300 N) was placed in a winding mold and heated at 160°C for 40 minutes under a pressure of 90 kg/ ^cm2 to harden it, resulting in an outer diameter of 32 mm consisting of an inner layer of 2 mm and an outer layer of 1 mm.
mm composite tube was obtained. Production Example 3 An iron core was inserted into the 50 cm pipe obtained in Reference Example 4, and the pipe was sandwiched between three rolls heated to 160°C, and epoxy resin (manufactured by Ciel Chemical Co., Ltd., trade name Epicote 828) was added. After wrapping the canvas impregnated with a roll while rotating, the roll was continued to rotate for 15 minutes to cure, thereby obtaining a composite tube with an outer diameter of 32 mm, consisting of an inner layer of 2 mm and an outer layer of 1 mm. Table 2 shows the performance measurement results of the tubes obtained in each production example and comparative example. These results show that the synthetic resin composite pipe of the present invention has excellent heat resistance, flame resistance, and impact resistance.

【table】

【table】

【table】 [Brief explanation of the drawing]

Figures 1 and 2 are electron micrographs showing the shape of the filled fibers in the cross section of a phenolic resin tube extruded by a conventional extrusion method, in the tube axis direction and in the direction perpendicular to the tube axis, respectively. , 3 and 4 are electron microscope images of the shapes of the filled fibers in the cross-sections of the phenolic resin tube forming the inner layer of the synthetic resin composite tube of the present invention in the tube axis direction and in the direction perpendicular to the tube axis, respectively. It's a photo. FIG. 5 is a diagram showing an example of a preferred method for coating a thermosetting resin pipe with a thermosetting resin in the present invention (including some perspective views), and FIGS. It is a figure showing an example of the method. DESCRIPTION OF SYMBOLS 1... Smooth part, 2... Screw, 3... Extruder, 4... Thermosetting resin pipe, 5... Post cure device, 6... FRP molding machine, 7... Heating device, 8
... Composite pipe, 9 ... Cloth impregnated with thermosetting resin, 10 ... Mold, 11 ... Roll.

Claims (1)

[Claims] 1. Using an extruder equipped with a screw having a feeding section, a compression section, a measuring section, and a smooth section, and a cylinder having a constant inner diameter, the extruder is shaped between the screw smooth section and the inner wall of the cylinder, and , the resin and/or filler is oriented in irregular directions, the ratio of the compressive strength in the direction perpendicular to the tube axis and the compressive strength in the tube axis direction is 0.4 to 1.5, and the breaking stress is 400 to 700 kg/
A synthetic resin composite tube made by coating the surface of a cm ² thermosetting resin tube with thermosetting resin.