JPH03251432A - Manufacture of corrosion-resistant reinforced plastic tube - Google Patents

Abstract

PURPOSE:To manufacture a tube with smooth inner wall surface, without pinholes and without corrosion of a glass fiber material as a reinforced material and upgrade the strength of the tube by forming a layer of given thickness composed of resin only on a section forming an innermost layer of the tube and then winding the reinforcing material and heat curing the resin. CONSTITUTION:Heat-curing resin 3 of desired quantity is fed from a feeding hose 18 onto a release sheet 24 and smoothed thereon by a spatula 19 to form continuously heat-curing resin layers 31 of uniform thickness. The heat-curing resin layers 31 move toward a curing oven 16 following the advancement of a mold surface 15 heated by a preheater 17 from the side of a mold 13 and cured starting from section facing the release sheet 24. The heat-curing resin layers 31 are arranged not to be entirely cured. Then, laminate welding is carried out in the order of glass paper 21, glass strand 22, resin concrete 25, glass strand 22 and glass paper 21, and then the heat-curing resin is heated in the curing oven 16 and cured to manufacture a reinforced plastic tube.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a reinforced plastic pipe with excellent corrosion resistance.

[Conventional technology]

In recent years, composite pipes with a sandwich structure, in which an intermediate layer such as resin mortar is provided between inner and outer reinforced resin layers reinforced with long glass fibers, have been used for large-diameter sewer pipes, etc. be. This type of composite pipe is lighter and has better corrosion resistance than metal or concrete pipes.

[Problem to be solved by the invention]

By the way, the water flowing down the sewer system includes domestic wastewater and some industrial wastewater, and the water quality may be extremely poor depending on the location, and even the above-mentioned composite pipe may not exhibit sufficient corrosion resistance. In other words, in composite pipes obtained by conventional manufacturing methods, the glass fiber material as a reinforcing material is present even near the inner wall surface of the pipe, and if there are pinholes or cracks on the inner wall surface, water flowing down can penetrate these pinholes or cracks. It penetrates through the glass fiber material continuously embedded in the tube wall. Glass fibers have poor chemical resistance, and are particularly vulnerable to alkalis and acids, so they continue to deteriorate indefinitely, significantly reducing the strength of the inner reinforced resin layer, and causing damage due to external forces such as tonosho. There is. Therefore, the present applicant first proposed a method for manufacturing a composite pipe as disclosed in Japanese Patent Publication No. 61-29254. In this manufacturing method, a strip containing a nonwoven fabric, a group of short fibers, and a resin is placed on a core mold to degas it by strong pressure, and then the resin is semi-cured and wound around the core mold to form an inner protective layer. The inner protective layer is fully defoamed and has very few pinholes, and is semi-cured in advance, so that when the whole is integrally cured, It has the excellent effect of not causing any cracks. However, even in the composite tube obtained by this manufacturing method, the inner protective layer contains nonwoven fabric and short fibers, so
Not only is it impossible to completely eliminate pinholes, but even if the resin and roving are completely impregnated, water channels exist at the interface between the resin and the roving, and penetration of the chemical solution is unavoidable. In view of these circumstances, the present invention aims to provide a method for manufacturing a reinforced plastic pipe with excellent corrosion resistance.

[Means to solve the problem]

In order to achieve such an object, the present invention forms an uncured thermosetting resin layer of a desired thickness around a cylindrical mold that has been subjected to a mold release treatment, and is made by forming an uncured thermosetting resin layer of a desired thickness around a cylindrical mold that has been subjected to a mold release treatment, and by the heat of the heated mold. After curing the thermosetting resin layer by a predetermined thickness from the surface facing the mold while keeping the surface side part in an uncured state, reinforcing material and thermosetting resin are wound around the layer and heated again. The gist of this paper is a method for manufacturing corrosion-resistant reinforced plastic pipes in which all of the uncured thermosetting resin is cured.

[For production]

According to the above configuration, an uncured thermosetting resin layer of a desired thickness formed on the peripheral surface of the mold is heated from the mold side to keep the surface side exposed to the outside air in an uncured state, First, a predetermined thickness of a resin-only layer is formed on the innermost layer of the tube by curing it by a predetermined thickness from the mold side surface. Next, the reinforcing material and thermosetting resin are further wound, but since the resin in the innermost layer has already hardened, care must be taken to prevent the reinforcing material, such as glass fiber, from entering the innermost layer. It can be turned. After that, all the resin can be cured to complete the tube.

【Example】

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 shows an example of manufacturing equipment used to carry out the method for manufacturing a corrosion-resistant reinforced plastic pipe according to the present invention. As shown in the figure, this manufacturing apparatus 1 is an F-Rostholm type molding apparatus, and is a cylindrical mold with one side open that rotates around a rotating shaft 12 extending horizontally from an apparatus main body 11. A mold (mandrel) 13 is provided, and an endless steel belt 14 is spirally wound around the mold 13.
As the mold 13 rotates, a mold surface 15 formed by a steel belt 14 moves forward. and,
The steel belt 14 that has reached the open end of the mold 13 passes through the center of the mold 13, returns to its original position, and is wound around the mold 13 again. Further, the mold 13 is configured such that its open end faces into the hardening furnace 16. On the other hand, on the side of the device body 11 of the mold 13, as shown in FIG. 2, a preheater 17 is provided on the inside, and a thermosetting resin supply hose 18 and a spatula 19 are provided on the outside. The preheating heater 17 is provided only between a preheating zone of a certain length from the device main body 11, and preheats the mold 13 in that portion from the inside. In addition, in the figure, 3 is a thermosetting resin, 21 is glass paper, 22 is a glass strand, 23 is a resin concrete supply means, and 24 is a mold release sheet, and both the glass paper 21 and the glass strand 22 are preliminarily prepared. Impregnated with thermosetting resin. This manufacturing apparatus 1 is configured as described above, and can continuously produce reinforced plastic tubes in the following manner. That is, the mold release sheet 24 is spirally wound without rotating the mold 13 to advance the mold surface 15 formed by the steel belt 14 toward the curing furnace 16. Then, a desired amount of thermosetting resin 3 is supplied from the supply hose 18 onto the release sheet 24 and leveled with a spatula 19 to continuously form a thermosetting resin layer 31 of uniform thickness. The thermosetting resin layer 31 gradually moves toward the curing furnace 16 as the mold surface 15 advances, but while it is in the preheating zone, it is heated from the mold 13 side by the preheating heater 17.
It gradually hardens from the part facing the release sheet 24. However, in the preheating zone, the thermosetting resin layer 31 is set so that it is not completely cured, and the thermosetting resin layer 31 is set so that it passes through the preheating zone with at least the surface in contact with the outside air remaining uncured. It is being done. The thickness of the hardened part depends on the amount of resin supplied, the molding length of the mandrel,
It can be changed freely by adjusting the heater temperature, molding speed, etc. Next, the glass paper 21.degree. glass strand 22 as a reinforcing material and the resin concrete 25 supplied from the resin concrete supply means 23 are applied to the glass paper 21.degree. Glass strand 22. Resin concrete 25. Glass strand 22. glass paper 2
After being laminated and wound in the order of No. 1, the thermosetting resin is heated again in the curing furnace 16 to harden the unhardened thermosetting resin, thereby making it possible to continuously obtain a reinforced plastic tube. Note that the release sheet 24 is designed to be removed after molding. The obtained reinforced plastic tube has no pinholes because the innermost layer is made only of resin and does not contain any fibrous materials or fillers that would cause such problems. Moreover, since it is made only of resin, the appearance of the inner wall surface is also good. The resin used in this manufacturing method is not particularly limited, but includes unsaturated polyester resins, vinyl ester resins, epoxy resins, etc. Among these, vinyl ester resins are particularly preferred because of their excellent chemical resistance. . Note that the resin forming the innermost layer and the resin wound together with the reinforcing material may be the same resin, or may be different resins. For example, if a fast-curing resin is used as the resin forming the innermost layer, there is an advantage that the molding line can be shortened. (Example 1) FRPM with a diameter of 80 cm was manufactured using the manufacturing equipment shown in Fig. 1.
A tube was formed. The manufacturing conditions were as follows. Preheating heater length: 50cm Heater surface temperature: 100°C Molding speed
20m/h Resin used: Unsaturated polyester resin (Nihon Oil & Fats Co., Ltd. (M-made Permec N) containing 1phr of hardening agent) Reinforcement material used: Glass paper (200g/rri
) Glass roving (number 2200) The obtained tube had a glossy inner wall surface, and no pinholes, voids, etc. were found by visual inspection. In addition, when cut and observing the cross section of the tube, it is found that 1 mm from the inner wall surface.
A layer of only resin was formed to a depth of . (Comparative Example 1) The innermost layer of the tube was defoamed by applying strong pressure to a semi-cured sheet made of resin, glass chop (thickness 13 μm, length 5 cm) and polyester nonwoven fabric (100 g/m), and then molded onto a mold. A tube was molded in the same manner as in Example 1 except for the following steps. The inner wall surface of the obtained tube was glossy, but the chop pattern was visible and did not look good. Furthermore, when the tube was cut and the cross section was observed, reinforcing fiber material was present up to the innermost layer. (Comparative Example 2) A tube was molded in the same manner as in Example except that the innermost layer of the tube was molded from resin and glass mat (300 g/m). The inner wall surface of the obtained tube did not have a good appearance, with pinholes partially visible and the mat visible through it. Furthermore, when the tube was cut and the cross section was observed, reinforcing fiber material was present up to the innermost layer. In the jig 4 as shown in FIG. 3, the above Example 1 and Comparative Example 1
The tubes 5 obtained in , 2 were each cut into 30 cm wide rings and attached, flattened by 5% to reproduce the state of being buried in the soil, and the inner wall surface of the tube was heated to 10% by weight at 23°C ± 1°C.
Each tube was exposed to sulfuric acid solution 6, and the time until white cracks appeared on the inner wall surface of the tube was measured. As a result, the tube obtained in Example 1 showed no cracking even after 6070 hours, whereas Comparative Example 1 did not crack after 3000 hours, and Comparative Example 2 had no cracks after 70 hours.
White cracks appeared in 00 hours. The method for manufacturing a corrosion-resistant reinforced plastic pipe according to the present invention is not limited to the above embodiments. In the above embodiment, the reinforced plastic tube was continuously molded using a Trostholm type molding apparatus, but it may also be molded in a batch type. Furthermore, if the surface of the mold has been subjected to mold release treatment in advance, there is no need to use a mold release sheet. Furthermore, in the above example,
Although the obtained reinforced plastic pipe was an FRPM pipe having a resin concrete layer as an intermediate layer, a normal FRP pipe without a resin concrete layer can also be obtained.

【Effect of the invention】

As described above, the method for manufacturing a corrosion-resistant reinforced plastic tube according to the present invention is as follows: First, a thermosetting resin layer formed around a cylindrical mold that has been subjected to mold release treatment is left in an uncured state on the surface side. While holding the tube, it was cured to a predetermined thickness from the surface on the mold side to form a resin-only layer on the innermost layer of the tube, and then the reinforcing material and thermosetting resin were wound on top of it, so that the inner wall surface of the tube It is possible to provide an excellent reinforced plastic pipe that is smooth and free of pinholes, and that does not suffer from deterioration in the strength of the pipe due to corrosion of the glass fiber material used as a reinforcing material.

[Brief explanation of drawings]

FIG. 1 is a side view of an example of a manufacturing device used to carry out the manufacturing method according to the present invention, and FIG. 2 is a vertical cross-sectional view of the supply means for the thermosetting resin forming the innermost layer. The plan view and FIG. 3 are explanatory views for explaining the state of the chemical resistance test of the obtained reinforced plastic. 13...Mold 21...Glass paper (reinforcing material)
22...Glass strand (reinforcing material) 24...Release sheet 25...Resin concrete 3...Thermosetting 1 2

Claims (1)

[Claims] (1) Form an uncured thermosetting resin layer of a desired thickness around a cylindrical mold that has been subjected to mold release treatment, and the surface side portion of the thermosetting resin layer is heated by the heat of the heated mold. After curing a predetermined thickness from the mold side surface while keeping it in an uncured state, the reinforcing material and thermosetting resin are wound on top of it and heated again to harden all of the uncured thermosetting resin. A method for producing corrosion-resistant reinforced plastic pipes.