JP3893689B2 - Manhole cover and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manhole cover made of a reaction injection molded body having a texture pattern formed on its surface, and a method for manufacturing the same.
[0002]
[Prior art]
For example, a manhole cover is detachably attached to a manhole hole formed in the ground in order to perform maintenance of sewers, waterworks, electrical wiring, gas piping, septic tanks, etc. buried in the ground.
[0003]
A metal manhole cover is well known as a conventional manhole cover. However, the metal manhole cover has a problem that it is heavy and inconvenient to handle. In addition, there is a problem that noise is generated when an automobile passes over a manhole.
[0004]
Therefore, a manhole cover made of synthetic resin has been proposed. For example, manhole covers made by FRP manhole covers and reaction injection molding (RIM) of norbornene monomers have been proposed.
[0005]
[Problems to be solved by the invention]
However, the manhole cover made of FRP has a problem that it takes time to manufacture and the manufacturing cost increases. In contrast, reaction injection molding of norbornene-based monomers is suitable for use as a manhole cover because the molding time is short, the production cost can be reduced, and the molded body has excellent mechanical strength. It is considered to be.
[0006]
However, with the conventional norbornene-based RIM technology, only a manhole cover whose surface is slippery can be formed.
[0007]
The present invention has been made in view of such a situation, and is lightweight, easy to handle, has low noise, has sufficient mechanical strength required as a manhole cover, and has a top surface that is difficult to slip, and a manufacturing method thereof The purpose is to provide.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the manhole cover according to the present invention is composed of a reaction injection molded body of a norbornene-based monomer having a wrinkle pattern formed on the upper surface.
[0009]
In order to prevent slipping and accumulation of water, it is preferable to form a concave portion and a convex portion on the upper surface of the manhole cover. According to general reaction injection molding, a circular convex portion or a circular concave portion having a diameter of about 300 mm or more can be easily molded.
[0010]
In order to further enhance the anti-slip effect, a finer uneven pattern such as a texture pattern is formed on the top surface of the convex part. The wrinkle pattern includes a pear-like wrinkle pattern, a leather-like wrinkle pattern, a cloth-like wrinkle pattern, a stone-like wrinkle pattern, a wood-grain wrinkle pattern, a geometric wrinkle pattern, or other wrinkle patterns. In the texture pattern, the maximum height Rmax of the surface roughness specified in Japanese Industrial Standard (JIS) is about 25 s to 1000 s, or the maximum height of the convex portion (between the top of the convex portion and the bottom of the concave portion). Maximum distance) is 0.5 to 5 mm. Furthermore, the minimum diameter or the minimum width of the minute convex portion or the minute concave portion constituting the texture pattern is 3.0 mm or less.
[0011]
In the conventional norbornene-based RIM, even if the surface of the mold is subjected to a textured process so as to form a fine textured pattern on the surface, the surface of the molded product does not follow the surface of the mold, so that the textured process is difficult.
[0012]
The method for manufacturing a manhole cover according to the present invention uses a mold apparatus having a first mold and a second mold, and sets the temperature of the second mold having a texture pattern transfer surface formed on the cavity inner peripheral surface to the first temperature. The reaction stock solution is injected into the cavity of the mold apparatus in a state higher than the temperature of one mold, the reaction injection molding is performed, and the embossed pattern is formed on the upper surface of the manhole cover contacting the second mold. And Such a specific molding method makes it possible for the first time to transfer a textured pattern of a mold to a molded product, which was impossible with the conventional method.
[0013]
The second mold and the first mold are made of materials having different linear expansion coefficients. Due to the temperature difference between the second mold and the first mold, the amount of thermal expansion of these molds is reduced. It is preferable to use a material whose absolute values are substantially equal. As such a combination of materials, the first mold is a cast aluminum mold, and the second mold is an electrocast mold in which a refractory metal layer such as nickel is lined with a resister. A regicon is a concrete mold containing resin and aluminum powder.
[0014]
In the present invention, the temperature of the second mold is preferably 20 to 50 ° C., more preferably about 20 to 40 ° C. higher than the temperature of the first mold. The temperature of the first mold is preferably 30 to 70 ° C, more preferably 40 to 60 ° C. By setting to such a temperature range, the shape of the embossed pattern transfer surface formed on the cavity inner peripheral surface of the second mold is satisfactorily transferred to the molded body.
[0015]
When the first mold is a cast aluminum mold and the second mold is a nickel-plated electroformed mold, the respective linear expansion coefficients are α₁= 23 × 10^-6/ K, α₂= 13.3 × 10^-6/ K. Assuming that the room temperature is 10 ° C, the first mold made of cast aluminum is set to 45 ° C, and the second mold made of electroplated nickel plating is set to 70 ° C. In the first mold, α₁× (45-10) = 8.05 × 10^-FourIn the second mold, α₂ × (70-10) = 7.98 × 10^-FourAnd they are almost equal. Therefore, even if a temperature difference is provided between the first mold and the second mold, the absolute amounts of thermal expansion of both are substantially equal, and the dimensional accuracy of the molded product is not adversely affected.
[0016]
In the present invention, the upper surface side of the manhole cover preferably has a convex shape that rises at the center. This is to prevent rainwater from accumulating on the lid. Further, in order to improve drainage, a drainage groove may be formed on the upper surface of the lid. In addition to the drainage grooves, anti-slip grooves and irregularities may be formed. In any case, in the present invention, in addition to the drainage groove, the anti-slip groove and the unevenness, a texture pattern which is an uneven pattern finer than these grooves and unevenness is formed on at least the upper surface of the manhole cover. It is.
[0017]
In the present invention, the manhole cover preferably has one or two handle portions. In the case where there are two grip portions, as shown in FIG. 1, it is preferable that the grip portion is located in a place where there is no rib and is in a symmetrical position. In the embodiment, the grip portion is projected so as to protrude to the bottom surface side of the lid body 8. A part forming groove 10 is formed. As shown in FIG. 2, a fitting hole 12 is formed in the handle portion forming groove 10, and a handle portion such as a metal rod is fitted therein.
[0018]
Further, on the upper surface of the manhole cover, a handle may be integrally formed with synthetic resin at the time of molding the lid, but a handle made of metal or the like may be attached later to the upper surface of the lid.
[0019]
In the present invention, the outer shape of the manhole cover is not particularly limited, and may be an ellipse or a rectangle other than a circle. Further, in the present invention, the term “manhole cover” is used in a broad sense including a checker plate in addition to a normal manhole cover. In other words, the manhole cover in the present invention means a removably attached to a hole formed on the ground for some purpose.
[0020]
In the present invention, as a reaction stock solution used for reaction injection molding, one containing a norbornene monomer is used.
[0021]
Norbornene monomer
In the present invention, the reaction injection molding is a method in which a norbornene-based monomer is bulk polymerized in a mold in the presence of a metathesis catalyst, and any monomer may be used as long as it has a norbornene ring. It is preferable to use a tricyclic or higher polycyclic norbornene-based monomer because a molded article having excellent properties can be obtained.
[0022]
Specific examples of norbornene-based monomers include bicyclic compounds such as norbornene and norbornadiene; tricyclic compounds such as dicyclopentadiene (cyclopentadiene dimer) and dihydrodicyclopentadiene; tetracyclic compounds such as tetracyclododecene; Pentacycles such as pentadiene trimer; heptacycles such as cyclopentadiene tetramer; alkyl such as methyl, ethyl, propyl and butyl, alkenyl such as vinyl, alkylidene such as ethylidene, phenyl, tolyl, naphthyl, etc. Substituents such as aryl of the above; further, substituents having polar groups such as ester groups, ether groups, cyano groups, and halogen atoms are exemplified. One or more of these monomers may be used in combination. Tricyclic, tetracyclic, or pentacyclic monomers are preferred because they are easily available, have excellent reactivity, and are excellent in heat resistance of the resulting resin molding.
[0023]
Further, the ring-opening polymer to be produced is preferably a thermosetting type. For that purpose, among the norbornene monomers, a crosslinkable monomer having two or more reactive double bonds such as cyclopentadiene trimer is used. Those containing at least are used. The proportion of the crosslinkable monomer in all norbornene monomers is preferably 2 to 30% by weight.
[0024]
In addition, monocyclic cycloolefins such as cyclobutene, cyclopentene, cyclopentadiene, cyclooctene, and cyclododecene, which can be ring-opening copolymerized with a norbornene-based monomer, may be used as a comonomer within a range that does not impair the object of the present invention.
[0025]
Metathesis catalyst
The metathesis catalyst that can be used in reaction injection molding using a norbornene-based monomer is not particularly limited as long as it can ring-open polymerization the norbornene-based monomer by the RIM method, and may be a known one. For example, halides such as tungsten or molybdenum, oxyhalides, oxides, ammonium salts, heteropolyacids (P⁵⁺, As⁵⁺, Si⁴⁺, Ge⁴⁺, Ce⁴⁺, Th⁴⁺, Mn⁴⁺, Ni⁴⁺, Te⁶⁺, I⁷⁺, Co³⁺, Al³⁺, Cr³⁺, Cu²⁺A compound of a heteroatom such as tungsten or molybdenum). In the present invention, a molybdenum-based metathesis catalyst such as organic molybdic acid such as tridodecyl ammonium molybdate, tri (tridecyl) ammonium molybdate, or molybdate organic ammonium salt such as ammonium acid is preferably used.
[0026]
The amount of the metathesis catalyst used is usually 0.01 mmol or more, preferably 0.1 mmol or more and 50 mmol or less, preferably 20 mmol or less with respect to 1 mol of the monomer used in the whole reaction solution. If the amount of metathesis catalyst used is too small, the polymerization activity is too low and the reaction takes a long time, resulting in poor production efficiency.If the amount used is too large, the reaction is too intense and hardens before being fully filled in the mold. In other words, the catalyst is likely to precipitate, and it is difficult to store it homogeneously. The metathesis catalyst is usually used after being dissolved in a monomer, but if it is in a range that does not substantially impair the properties of the molded article by the RIM method, it is suspended in a small amount of solvent and then mixed with the monomer. Therefore, it may be difficult to precipitate, or the solubility may be increased.
[0027]
Activator
As the activator (cocatalyst), known as disclosed in JP-A-58-127728, JP-A-4-226124, JP-A-58-129003, JP-A-4-145247. In the present invention, for example, organoaluminum compounds such as alkylaluminum halides such as ethylaluminum dichloride and diethylaluminum chloride, and alkoxyalkylaluminum halides are preferably used.
[0028]
The amount of the activator used is not particularly limited, but is usually 0.1 mol or more, preferably 1 mol or more, and 100 mol or less, preferably 10 mol or less with respect to 1 mol of the metathesis catalyst used in the whole reaction solution. It is. If the activator is not used or if the amount of the activator used is too small, the polymerization activity is too low and the reaction takes time, resulting in poor production efficiency. Conversely, if the amount used is too large, the reaction is so intense that it may harden before it is fully filled in the mold. The activator is used after being dissolved in the monomer. However, as long as it does not substantially impair the properties of the molded article by the RIM method, the activator is suspended in a small amount of solvent and then mixed with the monomer. It may be difficult to use or may be used with increased solubility.
[0029]
In the present invention, generally, an active regulator is used in combination with the active agent. By using an activity regulator in combination, the reaction rate, the time from mixing the reaction solution to the start of the reaction, the reaction activity, etc. can be changed.
[0030]
As the activity regulator, a compound having an action of reducing the metathesis catalyst is used, and as the activity regulator, alcohols, haloalcohols, esters, ethers, nitriles and the like are exemplified. Among these, specific examples of alcohols include n-propanol, n-butanol, n-hexanol, 2-butanol, isobutyl alcohol, isopropyl alcohol, t-butyl alcohol and the like. Specific examples of haloalcohols Examples include 1,3-dichloro-2-propanol, 2-chloroethanol, 1-chlorobutanol and the like. In addition, the addition amount of an activity regulator changes with the compounds to be used, and is not uniform.
[0031]
Other optional ingredients
If desired, various additives such as antioxidants, fillers, pigments, colorants, foaming agents, flame retardants, sliding imparting agents, elastomers, dicyclopentadiene-based thermal polymerization resins and their hydrogenated products may be added to the reaction stock solution. And thereby modify the properties of the resulting RIM product.
[0032]
In particular, for the purpose of obtaining a molded article having high mechanical strength, a reinforcing material can be filled in the mold in advance, and then the polymerization reaction liquid can be poured into the mold and cured. The filling amount of the reinforcing material is not particularly limited, but is usually 10% by weight or more, preferably 20 to 60% by weight of the monomer weight. If the filling amount is small, the mechanical strength ratio is small. When the filling amount is too large, uneven filling may occur without filling or filling inhibition tends to occur.
[0033]
Examples of the reinforcing material include glass fiber, aramid fiber, carbon fiber, ultra high molecular weight polyethylene fiber, metal fiber, polypropylene fiber, aluminum coated glass fiber, cotton, acrylic fiber, boron fiber, silicon carbide fiber, alumina fiber, and the like. be able to. These reinforcing materials can be used in various shapes such as those obtained by matting long fiber or chopped strands, those woven into a cloth, and those having a chopped shape. Those reinforcing materials whose surfaces are treated with a coupling agent such as a silane coupling material are preferable for improving the adhesion to the resin. The blending amount of the reinforcing material is not particularly limited, but is usually 10% by weight or more, preferably 20 to 60% by weight, with the total monomer weight being 100% by weight. By blending the reinforcing material in such a range, the mechanical strength of the manhole cover can be improved.
[0034]
In addition, for the purpose of further improving the mechanical strength of the manhole cover, a metal rod or a metal plate or the like is previously inserted into a mold for reaction injection molding, and then reaction injection molding is performed (insert molding). it can. By this insert molding, a manhole cover excellent in mechanical strength, in which a metal bar or a metal plate is integrally molded, can be obtained.
[0035]
As the antioxidant, there are various antioxidants for plastics and rubbers such as phenol, phosphorus and amine. Examples of the filler include inorganic fillers such as milled glass, carbon black, talc, calcium carbonate, aluminum hydroxide, mica, potassium titanate, and calcium sulfate.
[0036]
As the elastomer, natural rubber, polybutadiene, polyisoprene, styrene-butadiene copolymer (SBR), styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), ethylene- Examples include propylene-diene terpolymer (EPDM), ethylene vinyl acetate copolymer (EVA), and hydrides thereof. The amount of the elastomer added is appropriately selected so that the viscosity of the reaction stock solution at 30 ° C. is 5 cps or more, preferably 50 cps or more and 1000 cps or less, preferably 500 cps or less.
The additive is usually mixed in advance with either or both of the reaction solutions.
[0037]
Reaction injection molding method
As a preparation for reaction injection molding, a reaction injection molding material mainly composed of a norbornene monomer, a metathesis catalyst and an aluminum activator, a liquid B composed of a norbornene monomer and a metathesis catalyst, and the norbornene monomer Divide into two stable liquids consisting of an aluminum-based activator and liquid A and put them in separate tanks.
[0038]
The temperature of the reaction stock solution composed of the A solution or the B solution is 20 to 80 ° C., and the viscosity of the reaction stock solution is, for example, about 5 cps to 3000 cps, preferably about 100 cps to 1000 cps at 30 ° C.
[0039]
In the reaction injection molding, a reinforcing material (molded body) can be produced by placing a reinforcing material in a mold in advance and supplying a reaction liquid therein to polymerize it. Alternatively, a metal material or the like may be installed in the mold in advance and insert molded.
[0040]
In order to start reaction injection molding, the mixer is controlled to mix the liquid A and liquid B from the tank, and the mixed liquid is filled into the mold cavity as a reaction stock solution. The reaction stock solution filled in the cavite spreads inside the cavity.
[0041]
The polymerization time may be appropriately selected, but is usually about 20 seconds to 20 minutes after the completion of the reaction liquid injection. Mold pressure is usually 0-100Kg / cm² Range. The polymerization time may be appropriately selected, but is usually 30 seconds to 20 minutes after the completion of the reaction liquid injection. The injection pressure of the reaction stock solution is 2 × 10^Five ~ 5x10^Five Pa is preferred. If the injection pressure is too low, transfer of the texture pattern transfer surface formed on the cavity inner peripheral surface of the second mold tends not to be performed well. If the injection pressure is too high, the rigidity of the mold is increased. It must be done and is not economical.
[0042]
  Further, in the present invention, the reaction proceeds rapidly from the start of the injection of the reaction stock solution into the cavity of the mold apparatus, the time t ′ until the white smoke slightly rises from the surface of the generated resin, and the filling is completed from the start of the injection. The gel time ratio (t ′ / t), which is the ratio to the filling time t until, is usually 1.5 to 20, preferably 2 to 15, and more preferably 4 to 12. Gel timeratioIf it is larger than the above range, the reaction is slow, so the surface appearance of the molded article is poor, and the cycle is too slow to be mass-produced. On the contrary, gel timeratioIf it is small, the emboss is not formed, and the filling is insufficient.
[0043]
The t ′ is usually 100 seconds to 300 seconds, preferably 150 seconds to 250 seconds, although it depends on the size of the molded body. Moreover, although said t is based also on the magnitude | size of a molded object, it is 5 to 100 second normally, Preferably it is 8 to 50 second. When the molded body is a manhole cover, t is 10 seconds to 30 seconds.
[0044]
As a method for adjusting the reaction so as to be in such a range, a known method may be followed, for example, methods disclosed in JP-A-3-146516 and JP-A-4-337318. . JP-A-3-146516 discloses 5-vinylbicyclo [2,2,1] hept-2-ene (vinyl norbornene), 5-isopropenylbicyclo [2,2,1] hept- as a reaction regulator. A method for producing norbornene polymers using 5-alkenyl-2-norbornenes such as 2-ene is described, and JP-A-4-337318 discloses 5-ethynyl-2-norbornene as an activity regulator. The use of 5-alkynyl-2-norbornenes such as By setting the gel time ratio in the above-described range, the transfer of the texture pattern transfer surface formed on the cavity inner peripheral surface of the second mold is improved.
[0045]
When the reaction injection molding in the cavity is completed and the molded body is solidified, the reaction injection molded body of a norbornene monomer can be obtained by opening the mold.
[0046]
Grain pattern
The texture pattern formed on the surface of the manhole cover obtained by the method of the present invention is not particularly limited, and the maximum height Rmax of the surface roughness specified by JIS is about 25 s to 1000 s (preferably 50 s to 900 s). If it is a wrinkle pattern or if the wrinkle pattern cannot be defined by JIS, the maximum height of the convex portion (maximum distance between the top of the convex portion and the bottom of the concave portion; the plane on which the wrinkle is formed A texture pattern having a vertical distance of 0.5 to 5.0 mm (preferably 1.0 to 4.0 mm) may be used. The minimum diameter or minimum width of the minute convex portions or the minute concave portions constituting these texture patterns is 3.0 mm or less.
[0047]
As for the types of wrinkle patterns, qualitatively, geometric patterns such as satin-like wrinkles, leather-like wrinkles, cloth-like wrinkles, stone-like wrinkles, wood-grain wrinkles, diamond cut shapes, etc. There are grain patterns and the like, and these grain patterns can be used in combination with a picture pattern or a character pattern. According to the JIS surface roughness, Rmax is about 25 s to 1000 s, and can be specified by JIS, such as a textured texture pattern, a leather texture pattern, and a texture texture pattern. However, it is difficult to specify the stone-like texture pattern, the grain-like texture pattern, etc. according to the surface roughness of JIS, and it is possible to specify using the maximum height of the convex portion as a reference instead of JIS. it can. According to this standard, a grain-like texture pattern, a grain-like texture pattern, or the like can be specified as a texture pattern whose maximum height of the convex portion is 0.5 to 5 mm.
[0048]
In the present invention, after the reaction injection molding, the surface of the molded body may be roughened by a sandblast method or the like. As an example of a method for forming a slip stopper such as a textured pattern on the surface of the lid after reaction injection molding, there is a sand blast method (air blast method, wet blast method). The air blasting method is a method in which hard particles such as glass beads, walnut shell powder, sand, aluminum, and wheat are used as the projection material and sprayed onto the molding surface with the force of pressurized air to physically roughen the surface. is there. The wet blasting method is a method in which hard particles such as glass beads, aluminum, and wheat are used as a projection material and sprayed onto the surface of the molded product with a force such as pressurized water to physically roughen the surface of the molded product.
[0049]
The particle size of the projection material used in the sandblasting method is generally about 80 to 500 μm, but is preferably about 100 to 300 μm when the surface of the manhole cover is roughened. Moreover, the pressure which sprays a projection material can be controlled by the fluid pressure, and in the case of compressed air, 0.2-5 kgf / cm.² It is. Furthermore, although the angle which sprays a projection material is not specifically limited, It is 0-90 degree | times with respect to the surface to process, However, In order to roughen effectively, about 10-80 degree | times is required. Is appropriate.
[0050]
By these methods, it is possible to form arbitrary minute irregularities having an irregularity size or surface roughness of Rmax of about 25 to 1000 s on the surface of the manhole cover.
[0051]
[Action]
In the method for manufacturing a manhole cover according to the present invention, the temperature of the second mold in which the embossed pattern transfer surface is formed on the inner peripheral surface of the cavity is higher than the temperature of the first mold, and the cavity is formed in the cavity of the mold apparatus. The reaction stock solution is injected and reaction injection molding is performed. As a result, it is possible to mold a manhole cover made of a reaction injection molded body having a textured pattern, which has been considered impossible in the past. This is because the shape of the textured pattern transfer surface of the second mold is satisfactorily transferred to the surface of the reaction injection molded body.
[0052]
The reason why the texture pattern transfer surface of the second mold is thus transferred to the surface of the reaction injection molded body is that the temperature of the second mold is set higher than the temperature of the first mold. This is considered to be because the reaction of the reaction stock solution starts earlier from the portion in contact with the cavity inner peripheral surface of the second mold having a high temperature.
[0053]
Since the manhole cover according to the present invention is composed of a reaction injection molded body, it is lighter than a metal manhole, and the manhole hole can be easily opened and closed. In addition, there is less noise than metal manholes. In addition, in the present invention, since the manhole cover is preferably formed of a reaction injection molded article using a norbornene-based monomer, it has necessary and sufficient mechanical strength required for a manhole cover.
[0054]
Furthermore, since the embossed pattern is formed on the upper surface of the manhole cover, it is possible to effectively prevent slipping on the upper surface of the manhole cover. In addition, the beauty of the manhole cover is improved.
[0055]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described based on embodiments shown in the drawings.
[0056]
1 is a plan view of a manhole cover according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view taken along the line II-II shown in FIG. 1, and FIG. 3 (A) is a textured texture pattern formed on the manhole cover. FIG. 3B is a cross-sectional view of the main part along the line BB shown in FIG. 3A, FIG. 4 is a schematic configuration diagram of the mold apparatus, and FIG. 5 is a mold cavity inner peripheral surface. FIG. 6A is a plan view of a skin-like texture pattern according to another embodiment of the present invention, and FIG. 6B is a cross-sectional view taken along line BB shown in FIG. 7 is a plan view of a fabric-like grain pattern, FIG. 8 is a plan view of a stone-like grain pattern, FIG. 9 is a sectional view of the main part of a grain-like grain pattern, and FIG. The top view which shows the half of the manhole cover which concerns on this embodiment, FIG.10 (B) is a schematic sectional drawing which follows the BB line of the same figure (A).
[0057]
As shown in FIGS. 1 and 2, the manhole cover 2 according to one embodiment of the present invention has a circular outer shape, and a circular thick portion 4 is integrally formed at the center thereof so as to protrude toward the bottom surface side. Molded. On the outer periphery of the manhole cover 2, a ring-shaped flange portion 6 projecting toward the bottom surface is integrally formed. A relatively thin disk-shaped lid body 8 is integrally formed between the flange portion 6 and the thick portion 4. The lid body 8 has a uniform thickness from the thick portion 4 toward the flange portion 6 or a gradually thinner thickness toward the flange portion 6, and the minimum thickness t1 is 6 to 25 mm.
[0058]
On the bottom surface side of the lid body 8 located between the thick part 4 and the flange part 6, radially extending ribs 14 are integrally formed so as to connect the thick part 4 and the flange part 6. . The height t4 of the rib 14 is not particularly limited, and is preferably about 0 to 40 mm. The arrangement pitch angle θ1 of the ribs 14 is not particularly limited, and is preferably 30 to 180 degrees. In the present embodiment, the arrangement pitch angle θ1 is 45 degrees, and a total of eight radial ribs 14 are formed. The width of each rib 14 is not particularly limited, but in the present embodiment, the rib 14 becomes thicker toward the outer diameter side, and the rib width angle θ2 that defines the width of the rib 14 is preferably 0 to 35 degrees, More preferably, it is about 5 to 25 degrees. In the present invention, the ribs 14 are not necessarily formed, and the height t4, the arrangement pitch θ1, and the rib width angle θ2 of the ribs 14 are not particularly limited and can be variously modified. Further, ribs that cross the radial ribs 14 may be provided.
[0059]
As shown in FIG. 1, in the present embodiment, a grip portion forming groove 10 is formed so as to protrude to the bottom surface side of the lid main body 8 at a position that is located without a rib and is symmetrical. As shown in FIG. 2, a fitting hole 12 is formed in the handle portion forming groove 10, and a handle portion such as a metal rod is fitted therein. In addition, you may shape | mold a handle part integrally by reaction injection molding body resin.
[0060]
Further, as shown in FIG. 1, a pair of lock holes 16 penetrating the front and back surfaces of the lid are formed at the bottom surface position of the disc-like lid body 8 which is shifted by 90 degrees with respect to the handle portion forming groove 10. These lock holes 16 are provided with lock pieces so that the opening and closing of the manhole cover 2 can be locked.
[0061]
As shown in FIG. 2, the upper surface of the manhole cover 2 is flat or swelled at the center, so that rainwater or the like does not accumulate on the upper surface of the manhole cover 2. A drainage groove 22 is formed on the upper surface of the lid 2 to improve drainage. A convex portion 20 is formed between the draining groove 22 and the draining groove 22. The minimum width of the drainage groove 22 and the convex portion 20 is about 5 to 20 mm. In the present embodiment, as will be described later, a texture pattern is formed on the top surface of the convex portion 20 located between the drain grooves 22.
[0062]
In the present embodiment, the area S2 of the thick portion 4 has a ratio of S2 / S1 of preferably 0.02 to 0.8, more preferably 0.05 to, compared to the entire area S1 of the lid 2. It is determined to be 0.7, particularly preferably 0.07 to 0.6. By setting it as such an area ratio, the manhole cover 2 excellent in mechanical strength while being lightweight can be implement | achieved.
[0063]
The ratio of the minimum thickness t1 of the lid body 8 (t1 / t2) to the thickness t2 of the thick portion 4 is 0.05 to 0.8, preferably 0.1 to 0.7, Preferably, it is determined to be 0.15 to 0.6. If the ratio t1 / t2 is too large, the effect of forming the thick portion 4 is small, and if it is too small, molding is difficult, and the weight balance between the weight distribution in the central portion and the weight distribution in the peripheral portion is small. It does not contribute to improving the strength of the manhole cover 2.
[0064]
In the present embodiment, the thickness t3 of the ring-shaped flange portion 6 formed on the outer periphery of the lid 2 is preferably set to a ratio of t3 / t2 to the thickness t2 of the thick portion of the lid main body 8, preferably 0.00. It is determined to be 05 to 2, more preferably 0.7 to 1.3. Moreover, the radial direction width b of the flange part 6 becomes like this. Preferably it is 5-30 mm, More preferably, it is 10-25 mm. Since the flange portion 6 is in direct contact with the edge of the manhole hole, a predetermined range of thickness and width are required. The outer surface of the flange portion 6 is an inclined surface 7 whose outer diameter increases in a tapered shape from the bottom surface to the top surface of the lid 2. This is to prevent the lid 2 from falling into the hole when the manhole cover 2 is attached to the manhole hole.
[0065]
In the present embodiment, the matte surface shown in FIGS. 3A and 3B is provided on the top surface of the convex portion 20 formed on the upper surface side of the manhole cover configured as described above for the purpose of enhancing the anti-slip effect. A textured pattern 2a is formed. The pear-like texture pattern 2a is a pattern like the surface of a fruit pear, and is a pattern in which minute protrusions independent of each other are randomly formed. The surface roughness of the textured texture pattern 2a is 25 s to 1000 s, preferably 50 s to 900 s, when expressed by the maximum height Rmax of JIS.
[0066]
Such a manhole cover of this embodiment is manufactured by reaction injection molding (RIM) of a norbornene monomer.
As shown in FIG. 4, a mold apparatus 40 used for reaction injection molding includes a first mold 41 and a second mold 42. A cavity 43 is formed in the mold apparatus 40 by combining the split surfaces of the molds 41 and 42. In the present embodiment, the first mold 41 is a concave mold (cavity mold), and the second mold 42 is a convex mold (core mold). The shape of the cavity 43 corresponds to the shape of the obtained molded product, and in this embodiment, the shape is suitable for molding the manhole cover 2 shown in FIGS.
[0067]
The reaction stock solution can be injected into the cavity 43 from the gate 44. By forming the gate 44 at one location on the lower end of the cavity 43 in this way, the reaction stock solution conveniently enters the cavity 43 from the gate 44, and it becomes difficult to form an unfilled location inside the cavity 43. In addition, during injection, the gas in the cavity 43 conveniently escapes from the mold parting surface or a separately provided escape port, so that bubbles or the like hardly occur in the reaction stock solution.
[0068]
As shown in FIG. 5, a heat medium channel 82 is formed inside the molds 41 and 42 shown in FIG. 4, and the temperature on the cavity 43 side of the molds 41 and 42 is controlled to a constant temperature. It is. The heat medium channel 82 may be formed directly in the mold by forming a gap in the mold, or may be formed by embedding a pipe or the like. It is preferable to provide the heat medium channel 82 as close to the cavity 43 as possible. This is for controlling the temperature of the cavity 43.
[0069]
Circulation means such as a pump is attached to the heat medium flow path 82 so as to circulate hot water heated to a constant temperature in the heat exchange section. In the heat exchange unit, the temperature of the heat medium flowing in the flow path 82 is controlled to be constant by a heating unit such as a heater or a cooling unit such as a cooling element.
[0070]
In the present embodiment, the first mold 41 is made of cast aluminum. The 2nd metal mold | die 42 is comprised with the electrocasting metal mold | die. As shown in FIG. 5, in the second mold 42 made of an electroformed mold, the back surface of the metal plating layer 80 is lined with a resister 81. The metal plating layer 80 is made of, for example, nickel or copper, and the layer thickness is preferably 1 to 10 mm, and more preferably 3 to 6 mm. The regicon 81 is made of concrete including a resin such as an epoxy resin or polyester and aluminum powder. As shown in FIG. 5, in the electroformed second mold 42, a heat medium flow channel 82 is formed inside the regicon 81 near the metal plating layer 80. In the present embodiment, it is preferable that the arrangement interval of the heat medium flow paths 82 embedded in the second mold 42 is narrower than the arrangement interval of the heat medium flow paths embedded in the first mold 41 shown in FIG. 4. . This is because heat is more likely to be accumulated in the electroformed mold than in the aluminum mold, so that the arrangement interval of the flow paths 82 is made close and the temperature control is made accurate.
[0071]
In the present embodiment, the temperature of the second mold 42 is preferably set higher than the temperature of the first mold 41 by about 20 to 50 ° C., more preferably about 20 to 40 ° C. by temperature control using a heat medium. Specifically, the first mold 41 is set to 45 ° C., and the second mold 42 is set to 75 ° C.
[0072]
In addition, in the present embodiment, the texture pattern transfer surface 84 is formed on the surface of the metal plating layer 80 mounted on the cavity inner peripheral surface of the second mold 42 that is an electroformed mold. The wrinkle pattern transfer surface 84 is produced by reversing and transferring from a wrinkle pattern original mold, and is produced by electroforming. The reverse texture pattern on the texture pattern transfer surface 84 is inverted and transferred to the surface of the reaction injection molded object formed in the cavity 43, and the texture pattern as shown in FIG. Is formed.
[0073]
Next, the reaction injection molding method according to this embodiment will be described.
First, the molds 41 and 42 shown in FIG. Although the pressure at the time of mold clamping is not specifically limited, 0-100 kg / cm²It is. At the time of mold closing, the reaction stock solution is not injected into the mold, the temperature in the mold is the temperature of the temperature-controlled mold itself, and the temperature of the first mold 41 is 45 °. C, and the temperature of the second mold 42 is about 75 ° C.
[0074]
Simultaneously with mold clamping, in this embodiment, dry air or nitrogen may be purged to dry the inside of the cavity by a purge means (not shown). By this purging, the inside of the cavity 43 shown in FIG. 4 is replaced with nitrogen gas, and the inside of the cavity 43 is 0 to 3 kg / cm.²It is filled with nitrogen gas of about (gauge pressure). By purging with nitrogen, moisture inside the cavity can be expelled, the reaction stock solution can be prevented from being deactivated, the reactivity on the surface of the molded body is improved, and contamination of the inner peripheral surface of the mold is also prevented. it can. This nitrogen purge is performed until immediately before the start of the injection of the reaction stock solution.
[0075]
In this embodiment, reaction injection molding is reaction injection molding using a norbornene-based monomer.
[0076]
As the reaction stock solution used in the present embodiment, a norbornene-based monomer, a metathesis catalyst, an activator, an activity regulator and an optional component prepared by dividing them into two or more solutions are used. These reaction stock solutions are not bulk polymerized by only one liquid, but when all the liquids are mixed, each component becomes a predetermined ratio and the norbornene monomer is bulk polymerized.
[0077]
For example, a liquid composed of a norbornene-based monomer, a metathesis catalyst, and an optional component and a liquid composed of a norbornene-based monomer, an activator, an activity regulator, and an optional component are not polymerized as they are. If the total amount of each component contained in the two liquids is the amount of each component used in the present embodiment, these two liquids are reaction stock solutions used in the present embodiment, respectively.
[0078]
In order to improve workability, bulk polymerization is usually carried out using two reaction stock solutions, but three or more reaction stock solutions may be used. In order to allow other components to sufficiently diffuse into the norbornene monomer after the reaction stock solution is mixed, the norbornene monomer is usually contained in any reaction stock solution, and the other components are dissolved in the norbornene monomer. Alternatively, although it is preferably dispersed, there may be a reaction stock solution containing no norbornene-based monomer. Moreover, since bulk polymerization starts when one reaction stock solution contains the norbornene monomer, the metathesis catalyst, and the activator, the metathesis catalyst and the activator are not usually contained in one reaction stock solution.
[0079]
As a method of mixing the reaction stock solution, a method of instantaneously mixing with a mixing head is common. In this case, the container in which the stirring stock solution is stored becomes a separate flow source. As the mixing head, a low-pressure injector such as a collision mixing device, a dynamic mixer or a static mixer can be used.
[0080]
After mixing the reaction liquid, it may be injected or injected several times into a preheated mold, or it may be continuously injected, so the equipment can be lightened and operated at low pressure. It is possible to produce large and thick molded bodies. Furthermore, when there is a large amount of filler such as glass fiber, it is desirable to use a low-pressure injector that can uniformly fill the reaction liquid into the mold by slowing the injection speed.
[0081]
In the above RIM process, in order to avoid problems such as catalyst deactivation,₂It is also possible to make an inert atmosphere by purging inert gas such as. Moreover, when filling with a filler, a fiber reinforcement, etc., when adsorbed water is included, you may remove adsorbed water by drying beforehand.
[0082]
In the reaction injection molding, the filling time t from the start of injection to the end of injection is determined by the size of the molded body and the like. In the present embodiment, the blending activity of the blending liquid that is the reaction stock solution is set to 4 to 12 times the filling time t.
[0083]
  In the present embodiment, the reaction proceeds rapidly from the start of the injection of the reaction stock solution into the cavity of the mold apparatus, the time t ′ until the white smoke slightly rises from the surface of the generated resin, and the filling from the start of the injection. The gel time ratio (t ′ / t), which is a ratio with the filling time t until completion, is usually 1.5 to 20, preferably 2 to 15, and more preferably 4 to 12. Gel timeratioIf it is larger than the above range, the reaction is slow, so the surface appearance of the molded article is poor, and the cycle is too slow to be mass-produced. On the contrary, gel timeratioIf it is small, the emboss is not formed, and the filling is insufficient.
[0084]
The t ′ is usually 100 seconds to 300 seconds, preferably 150 seconds to 250 seconds, although it depends on the size of the molded body. Moreover, although said t is based also on the magnitude | size of a molded object, it is 5 to 100 second normally, Preferably it is 8 to 50 second. When the molded body is a manhole cover, t is 10 seconds to 30 seconds.
[0085]
As a method for adjusting the reaction so as to be in such a range, a known method may be followed, for example, methods disclosed in JP-A-3-146516 and JP-A-4-337318. . JP-A-3-146516 discloses 5-vinylbicyclo [2,2,1] hept-2-ene (vinyl norbornene), 5-isopropenylbicyclo [2,2,1] hept- as a reaction regulator. A method for producing norbornene polymers using 5-alkenyl-2-norbornenes such as 2-ene is described, and JP-A-4-337318 discloses 5-ethynyl-2-norbornene as an activity regulator. The use of 5-alkynyl-2-norbornenes such as The amount is also described. By setting the gel time ratio in the above-described range, the transfer of the texture pattern transfer surface formed on the cavity inner peripheral surface of the second mold is improved.
[0086]
In this embodiment, the injection pressure of the reaction stock solution is 2 × 10.^Five~ 5x10^FivePa is preferred. If the injection pressure is too low, the texture pattern transfer surface 84 formed on the inner peripheral surface of the cavity of the second mold 42 tends not to be transferred well. If the injection pressure is too high, the mold 41, The rigidity of 42 must be increased, which is not economical.
[0087]
After completion of the injection, the polymerization reaction starts, and after the completion of the reaction, the cooling is performed. After about 120 to 150 seconds after the completion of the injection, the mold is opened and the molded body is taken out.
[0088]
In the present embodiment, the temperature of the second mold 42 is set to about 30 ° C. higher than the temperature of the first mold 41, so that when the reaction stock solution is injected into the cavity 43 of the mold, the temperature The reaction starts more quickly from the portion in contact with the second mold 42 having a higher height, and a textured pattern 2a as shown in FIG. 3A is satisfactorily transferred and formed on the surface of the resulting molded body. Conventionally, it has been considered impossible to transfer such a texture pattern onto the surface of the reaction injection molded body.
[0089]
The manhole cover 2 which is a reaction injection molded body having a texture pattern according to the present embodiment thus obtained is made of a polynorbornene resin, so is hardly broken and has excellent impact resistance. . Moreover, since the embossed pattern 2a is formed on the surface of the convex portion 20 of the manhole cover 2, it is difficult to slip and is excellent in appearance. Furthermore, since such a texture pattern 2a is integrally formed at the time of reaction injection molding, a special work process for forming the texture pattern is not required, which contributes to a reduction in manufacturing cost.
Further, since the manhole cover 2 according to the present embodiment is made of a reaction injection molded body resin, it is lighter than a metal manhole, and manhole opening and closing operations are easy. In addition, there is less noise than metal manholes. Moreover, in the present embodiment, the mechanical strength of the manhole cover 2 is remarkably improved by integrally forming the thick portion 4 at the center of the manhole cover 2, and the mechanical strength required for the manhole cover 2. Can be fully satisfied.
[0090]
The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
[0091]
For example, the texture pattern formed on the surface of the convex portion 20 of the manhole cover 2 by the method of the present invention is not limited to the pattern shown in FIG. 3 and can be variously modified.
For example, either a leather-like texture pattern 2b that imitates the skin of a beast as shown in FIGS. 6A and 6B, or a cloth-like texture pattern 2c that imitates the surface of a cloth as shown in FIG. good. The skin-like texture pattern 2b and the fabric-like texture pattern 2c are texture patterns having a maximum surface roughness Rmax specified by JIS of about 25 s to 1000 s (preferably 50 s to 900 s).
[0092]
Further, as shown in FIG. 8, the grain-like texture pattern 2d imitating the surface of a stone is a grain-like texture pattern 2e imitating the pattern of a wood surface as shown in FIG. Also good. These stone-like texture patterns, grain-like texture patterns, etc. are difficult to identify by the provision of the surface roughness of JIS, and can be specified using the maximum height of the convex portion as a reference instead of JIS. . According to this standard, the grain-like grain pattern 2d, the grain-like grain pattern 2e, and the like have a maximum height of the convex portion of 0.5 to 5.0 mm (preferably 1.0 to 4.0 mm). As can be specified.
The specific shape of the manhole cover according to the present invention is not particularly limited. For example, as shown in FIGS. 10 (A) and (B), the manhole cover (checker plate) 2A may be formed in a rectangular shape. good. In that case, the central portion of the manhole cover 2A is a region including an intersection of diagonal lines connecting the corner portions of the rectangular manhole cover 2A, and the thick portion 4A formed at the central portion is also rectangular. Further, the flange portion 6A on which the inclined surface 7A is formed also has a rectangular ring shape, and the shape of the lid body 8A located between the flange portion 6A and the thick portion 4A also has a rectangular shape.
[0093]
However, the relationship between the area S2 of the thick portion 4A and the area S1 of the lid 2A, the relationship between the thickness t2 and the minimum thickness t1 of the thick portion 4A, the width b and the thickness t3 of the flange portion 6A are the same as those in the above embodiment. It is the same. The lid 2A is also integrally formed by reaction injection molding of a norbornene monomer as in the above-described embodiment, and the drainage groove 22 and the convex portion 20 as shown in FIG. And a wrinkle pattern is formed on the surface of the convex portion 20. In addition, you may shape | mold only a wrinkle pattern in the whole upper surface of a manhole cover, without forming the drainage groove | channel 22 and the convex part 20. FIG.
[0094]
Furthermore, in the embodiment described above, the texture pattern formed on the surface of the manhole cover is transferred and integrally molded from the transfer surface of the mold at the time of reaction injection molding. However, in the present invention, the texture pattern is not molded. A textured pattern may be formed by molding a molded body and then using a sandblast method on the surface thereof.
[0095]
Among the sand blasting methods (air blasting method, wet blasting method), the air blasting method uses a hard particle (preferably glass beads, sand) such as glass beads, walnut shell powder, sand, aluminum, and wheat as a projection material. This is a method in which the surface is physically roughened by spraying on the molding surface with a force such as compressed air. In the wet blast method, hard particles such as glass beads, aluminum, and wheat (preferably glass beads) are used as the projection material, and the surface of the molded product is physically roughened by spraying the surface of the molded product with the force of pressurized water or the like. It is a method to convert.
[0096]
The particle size of the projection material used in the sandblasting method is generally about 80 to 500 μm, but is preferably about 100 to 300 μm when the surface of the manhole cover is roughened. Moreover, the pressure which sprays a projection material can be controlled by the fluid pressure, and in the case of compressed air, 0.2-5 kgf / cm.² It is. Furthermore, although the angle which sprays a projection material is not specifically limited, It is 0-90 degree | times with respect to the surface to process, However, In order to roughen effectively, about 10-80 degree | times is required. Is appropriate.
[0097]
By these methods, it is possible to form arbitrary minute irregularities having an irregularity size or surface roughness of Rmax of about 25 to 1000 s on the surface of the manhole cover.
[0098]
【Example】
Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples. Parts and% are based on weight unless otherwise specified.
[0099]
Example 1
The first mold 41 shown in FIG. 4 is made of cast aluminum, the second mold 42 is made of an electroformed mold, and a texture pattern transfer surface 84 as shown in FIG. Was formed by electroforming. The reverse texture pattern formed on the texture pattern transfer surface 84 is the reverse texture pattern of the textured texture pattern shown in FIG. 3 in which the maximum surface roughness Rmax specified by JIS is 300 s.
[0100]
Also, a norbornene monomer composed of 90% cyclopentadiene dimer (DCP) and 10% cyclopentadiene trimer is placed in two tanks, and 40 mol of diethylaluminum chloride (DEAC) is added to one monomer. It added so that it might become a density | concentration and 48 molar concentration of 1, 3- dichloro- 2-propanol (dcPrOH) (A liquid). On the other hand, tri (tridecyl) ammonium molybdate was added to the monomer so as to have a concentration of 10 mmol, and 6% vinyl norbornene was added (liquid B). These A liquid and B liquid were stored in A tank and B tank, respectively. The alkoxylation ratio of these reaction stock solutions was 1.1, and the gel time ratio (t '/ t) was 6 because t was about 30 seconds and t' was about 180 seconds.
[0101]
By flowing hot water through the heat medium flow path 82 (see FIG. 5) mounted inside the cast aluminum first mold 41 and the electroformed second mold 42 having the nickel plating layer shown in FIG. The temperature of the first mold 41 was set to 45 ° C., and the temperature of the second mold 42 was set to 75 ° C. The linear expansion coefficient of each mold at this time is α in the first mold.₁ = 23 × 10^-6/ K, α for the second mold₂ = 13.3 × 10^-6/ K.
[0102]
Next, liquid A and liquid B having the same volume of 25 ° C. from the tank are mixed and injected into the cavity of the mold, and after about 10 minutes, a manhole made of a reaction injection molded body is used. The lid 2 was taken out.
[0103]
The outer diameter of the manhole cover 2 is 680 mm, and the total area S1 of the cover is about 363000 mm.²Met. Moreover, the outer diameter of the circular thick part 4 formed in the center part is 200 mm, and the area S2 is about 31400 mm.²Met. That is, S2 / S1 was about 0.087.
[0104]
The minimum thickness t1 of the lid body 8 was about 8 mm, the thickness t2 of the thick portion 4 was 35 mm, and t2 / t1 was about 4.38. Further, the thickness t3 of the flange portion 6 was 30 mm, and t3 / t1 was about 3.75. The width b of the flange portion 6 was 13 mm.
[0105]
Furthermore, four ribs 14 were formed at equal intervals in the circumferential direction, and the arrangement pitch angle θ1 of the four ribs 14 was 90 degrees, and the rib width angle θ2 was 6 degrees. Moreover, the height t4 of the rib 14 was 20 mm.
[0106]
When the surface in contact with the second mold 42 was observed on the manhole cover taken out from the mold, the reverse texture pattern of the texture pattern transfer surface 84 of the second mold 42 shown in FIG. Inverted and transferred, it was confirmed that a good texture pattern 2a shown in FIG. 3 was formed.
[0107]
Further, when 100 shots were molded and the variation of the thickness of the molded product (design value: 6 mm) was examined, it was confirmed that the absolute value was within 0.5 mm and the production yield was good.
[0108]
Furthermore, using this manhole cover 2, a load resistance test and an impact resistance test were performed. In the load-bearing test, a rubber plate with a thickness of 6 mm is placed on the upper surface of the manhole cover 2 placed on the test bench, and a weight is placed on the rubber plate. Measurement was performed, and 1/4 of the value was taken as a test value. The test value was 250 kg. The test was performed at room temperature.
[0109]
In the impact resistance test, a manhole cover was placed on a test bench, and a steel spherical weight having a weight of 1 kg was dropped from the position of 1 m height at the center of the manhole cover. In this example, no damage was observed.
[0110]
Example 2
The first mold 41 shown in FIG. 4 is made of cast aluminum, the second mold 42 is made of an electroformed mold, and a texture pattern transfer surface is formed on the cavity side inner peripheral surface by electroforming. did. The inverted texture pattern formed on the texture pattern transfer surface was an inverted texture pattern of the stone-like texture pattern 2d shown in FIG. 8 in which the maximum height of the convex portion was 3.0 mm.
[0111]
Except for the different texture pattern, reaction injection molding was performed in the same manner as in Example 1, and the manhole cover made of the reaction injection molded body was taken out from the mold.
[0112]
When the surface in contact with the second mold 42 was observed in the molded body taken out, the inverted wrinkle pattern was transferred to the surface of the molded body with good reversal, and the good grainy wrinkle pattern 2d shown in FIG. Been formed.
[0113]
Further, when 100 shots were molded and the variation of the thickness of the molded product (design value: 6 mm) was examined, it was confirmed that the absolute value was within 0.5 mm and the production yield was good.
[0114]
In the load resistance test and the impact resistance test, the same results as in Example 1 were obtained.
[0115]
Example 3
The first mold 41 shown in FIG. 4 is made of cast aluminum, the second mold 42 is made of an electroformed mold, and the grain-like grain pattern 2e as shown in FIG. A wrinkle pattern transfer surface corresponding to was formed by electroforming. The reverse texture pattern formed on the texture pattern transfer surface was the reverse texture pattern of the grain-like texture pattern 2d shown in FIG. 9 in which the maximum height of the convex portion was 1.5 mm.
[0116]
Except for the different texture pattern, reaction injection molding was performed in the same manner as in Example 1, and the manhole cover made of the reaction injection molded body was taken out from the mold. It was confirmed that the grain-like grain pattern 2e shown in FIG.
[0117]
Further, when 100 shots were molded and the variation of the thickness of the molded product (design value: 6 mm) was examined, it was confirmed that the absolute value was within 0.5 mm and the production yield was good.
[0118]
Furthermore, the same results as in Example 1 were obtained in the load resistance test and the impact resistance test.
[0119]
Example 4
Except for using a mold on which no wrinkle pattern transfer surface was formed, reaction injection molding was performed in the same manner as in Example 1, and after molding a manhole cover, the surface of the manhole cover was subjected to sandblasting, A wrinkle pattern was formed.
[0120]
The conditions for sandblasting are glass beads having a particle size of 100 μm as the projection material, a spray angle of 45 degrees, and an air pressure of 2.5 kgf / cm.²Met. When the surface of the obtained molded body was observed, it was confirmed that a textured pattern like ground glass was formed, and it became difficult to slip.
[0121]
Further, the same results as in Example 1 were obtained in the production yield, load resistance test and impact resistance test.
[0122]
Comparative Example 1
Except that the set temperature of the first mold 41 and the second mold 42 was the same 50 ° C., reaction injection molding was performed in the same manner as in Example 1, and the manhole cover made of the reaction injection molded body was taken out. .
[0123]
When the surface of the molded body on the second mold side was observed, fine bubbles of 0.1 to 0.5 mm were observed within an area of 10 cm square, no good transfer was performed, and no wrinkle pattern was formed. Further, when 100 shots were molded and the variation of the thickness of the molded product (design value: 6 mm) was examined, the absolute value was 2.0 mm.
[0124]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a manhole cover that is light and easy to handle, has low noise, and has sufficient mechanical strength required as a manhole cover. Moreover, since the embossed pattern is formed in the upper surface of the manhole cover based on this invention, the slip on the upper surface of a manhole cover can be prevented effectively. In addition, the beauty of the manhole cover is improved. Furthermore, according to the method of the present invention, a manhole cover having such a textured pattern can be realized extremely easily and at low cost.
[Brief description of the drawings]
FIG. 1 is a plan view of a manhole cover according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view taken along the line II-II shown in FIG.
FIG. 3 (A) is a plan view of a textured texture pattern formed on a manhole cover, and FIG. 3 (B) is a cross-sectional view of an essential part along line BB shown in FIG. 3 (A).
FIG. 4 is a schematic configuration diagram of a mold apparatus.
FIG. 5 is a cross-sectional view of a principal part showing an inner peripheral surface of a cavity of a mold.
6A is a plan view of a skin-like texture pattern according to another embodiment of the present invention, and FIG. 6B is a cross-sectional view along the line BB shown in FIG. 6A. FIG.
FIG. 7 is a plan view of a fabric-like texture pattern.
FIG. 8 is a plan view of a grainy texture pattern.
FIG. 9 is a cross-sectional view of a main part of a grain-like grain pattern.
FIG. 10 (A) is a plan view showing a half of a manhole cover according to another embodiment of the present invention, and FIG. 10 (B) is a schematic sectional view taken along line BB of FIG. 10 (A). is there.
[Explanation of symbols]
2,2A ... Manhole cover
2a ~ 2e ... grain pattern
4, 4A ... Thick part
6, 6A ... Flange
8,8A ... Lid body
14 ... Ribs
20 ... Convex
22 ... Drainage groove

Claims (2)

Using a mold apparatus having a first mold and a second mold,
The reaction stock solution is injected into the cavity of the mold apparatus in a state where the temperature of the second mold having the textured transfer surface formed on the inner peripheral surface of the cavity is higher than the temperature of the first mold, and the reaction injection molding is performed. When forming a wrinkle pattern on the upper surface of the manhole cover in contact with the second mold, the reaction proceeds rapidly from the start of the injection of the reaction stock solution into the cavity of the mold apparatus, and slightly white smoke from the surface of the generated resin The manhole is characterized in that the gel time ratio (t ′ / t), which is the ratio of the time t ′ until the time of rise to the filling time t from the start of injection of the reaction stock solution to the completion of filling, is 1.5-20 A method for manufacturing a lid. The method for producing a manhole cover according to claim 1, wherein the reaction injection molding is a method in which a norbornene-based monomer is bulk-polymerized in a mold in the presence of a metathesis catalyst.

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