JP4951375B2 - Protective cover manufacturing method and protective cover - Google Patents

Description

  The present invention relates to a method for manufacturing a protective cover suitable for protecting a pole, a post of a signboard, a handrail, a rod-like support such as a water pipe, and the like, a protective cover thereof, and an apparatus for manufacturing the protective cover.

  In a support having a corner (rod-shaped support), the corner is easily damaged, and is often damaged particularly when the support is transported or installed. In addition, if the corners are exposed, it may harm people and surrounding objects. In order to prevent such danger, a protective material for protecting the support, particularly its corners, is widely used.

  Japanese Utility Model Publication No. 51-37655 (Patent Document 1) is provided with a notch along the longitudinal direction of a synthetic resin cylindrical foam having elastic restoring force, and one end of the cylindrical body at the notch. There is disclosed an impact relaxation material for an article corner portion in which an edge is wound inwardly from the other end edge. As a method for producing the relaxation material, a method is described in which a synthetic resin is produced by extrusion from an extrusion die having a notch. The impact relaxation material obtained by such a manufacturing method cannot be said to have a sufficient holding force to hold the article, and is not practical as a protective material for protecting the article over a long period of time.

Japanese Patent No. 3182403 (Patent Document 2) includes a cylindrical polyethylene-based resin foam or a cylindrical polypropylene-based resin foam which has a continuous crack in the longitudinal direction, and both side edges forming the crack overlap each other. A protective material for a building is disclosed. As a method for producing this protective material, the resin is extruded from a chestnut-shaped lip having an open top, and the outer surface near the center of the extruded foam is cooled in order to increase the restoring force of the foam. A method of manufacturing is described. This cooling operation utilizes the fact that the inner surface of the foam shrinks as the inner surface of the foam becomes hotter than the outer surface and the foaming agent is more easily removed. However, in such a manufacturing method, the shape of the lip portion of the die and the foam to be extruded has a triangular cross section, and the protected material that can be protected by the building protective material is limited, There is a limit to increasing the restoring force of the foam, and it is difficult to improve the mounting property to the protected material.
Japanese Utility Model Publication No. 51-37655 (page 2, right column, lines 2-6) Japanese Patent No. 3182403 (paragraph number [0013])

  Accordingly, an object of the present invention is a method for producing a protective cover that is a foam having excellent resilience, has high wearability, and can protect a material to be protected for a long period of time with high retention, and its protective cover, and its It is providing the manufacturing apparatus of a protective cover.

  Another object of the present invention is to provide a method for manufacturing a protective cover that can adjust the restoring force, mounting property, and holding force of the foam, and that can protect a wide range of materials to be protected, its protective cover, and its protective cover. It is to provide a manufacturing apparatus.

  Still another object of the present invention is to provide a method for manufacturing a protective cover having a high surface smoothness and an excellent appearance, a protective cover thereof, and an apparatus for manufacturing the protective cover.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventor has formed and molded a thermoplastic foam by extrusion-foaming a thermoplastic resin and forming a cylindrical foam having a circular cross section and a wall cut in the axial direction. If the protective cover is manufactured through a bending step of bending one side wall to the other side of the side walls adjacent to the cut portion by utilizing the shrinkage difference between the inner and outer walls, it is excellent in restoring force and wearability The present invention has been completed by finding that it is possible to produce a protective cover that is high and that can protect the material to be protected for a long period of time with high retention.

  That is, the method of the present invention is a method for producing a protective cover for covering a rod-shaped support, which is obtained by extruding and foaming a thermoplastic resin, having a circular cross section, and the wall portion being cut in the axial direction. The protective cover is manufactured through a molding step of molding the cylindrical foam and a bending step of bending one side wall adjacent to the cut portion to the other side by utilizing the shrinkage difference between the inner and outer walls. In the molding step, the thermoplastic resin may be extruded and foamed to form a cylindrical foam having an annular cross section, and then the wall of the foam may be cut in the axial direction. For example, in the molding process, a cylindrical foam having a quadrangular cross section is molded using an olefin resin as the thermoplastic resin, and in the bending process, one side wall adjacent to the cut portion of the foam is used as the other side wall. You may manufacture a protective cover by bending 30-70 degrees to the side wall side. The width | variety of a cutting | disconnection part may be formed in the magnitude | size which can bend | fold one side wall to the other side wall side.

  In the molding step, the foaming ratio of the foam to be extruded may be about 20 to 50 times. Further, the inner diameter of the hollow portion of the foam is controlled using a member provided in the extrusion direction and in contact with the inner wall of the extruded foam, and the compressed air is circulated inside the foam. Periodic wall thickness fluctuations may be suppressed.

  In the bending step, since one side wall adjacent to the cut portion is bent toward the other side wall, the inner wall of one side wall may be cooled. The inner wall of one side wall may be cooled with at least one selected from water and air. In the manufacturing method of the present invention, the protective cover may be manufactured through the molding step and the bending step, respectively, or may be manufactured through the above steps continuously.

  The present invention includes a protective cover obtained by the manufacturing method and an apparatus for manufacturing the protective cover. The manufacturing apparatus according to the present invention includes a molding unit for molding a cylindrical foam having an annular section and a wall section cut in an axial direction by extruding and foaming a thermoplastic resin, and a shrinkage difference between the inner and outer walls. It may be provided with at least a bending unit that bends one side wall adjacent to the cut portion to the other side wall. The molding unit is provided in the extrusion direction and contacts the inner wall of the extruded foam to control the inner diameter of the hollow portion of the foam, and the compressed air is circulated inside the foam. There may be provided a corrugation removing unit configured with an air ejection unit for the purpose.

  In the present specification, the “tubular shape” is not limited to a hollow shape (or a hollow column shape) having a circular cross section, and includes a hollow shape having a circular cross section, for example, a hollow shape having a polygonal cross section. Use as meaning.

  In the method of the present invention, a thermoplastic resin is extruded and foamed, a cylindrical foam having an annular cross section and a wall portion cut in the axial direction is formed, and the cut portion is utilized by utilizing the shrinkage difference between the inner and outer walls. When one side wall adjacent to the side wall is bent toward the other side wall, it is possible to impart excellent restoring force, wearability and holding force to the protective cover obtained. Furthermore, it is possible to adjust the degree of restoring force, mountability, and holding force that can be imparted to the foam, and it is possible to easily attach to the protected material and protect the protected material in a wide variety of shapes. Further, when the corrugation removing unit is used, a protective cover having a high surface smoothness and an excellent appearance can be produced.

  Hereinafter, the present invention will be described in detail with reference to the accompanying drawings as necessary.

  In the method of the present invention, a thermoplastic resin is extruded and foamed, a cross-section is annular, and a cylindrical foam having a wall portion cut in the axial direction is molded, and the shrinkage difference between the inner and outer walls is utilized. The protective cover is manufactured by going through a bending step of bending one of the side walls adjacent to the cut portion to the other side wall. The method utilizes a difference in shrinkage between the inner and outer walls and a molding unit for molding a cylindrical foam having at least a thermoplastic resin extruded and foamed, having a circular cross section and a wall portion cut in the axial direction. And you may carry out using the apparatus provided with the bending unit which bends one side wall adjacent to a cutting part to the other side wall side.

  FIG. 1 is a schematic sectional view showing an example of the protective cover manufacturing apparatus of the present invention, and FIG. 2 is a partially cutaway schematic perspective view of the apparatus shown in FIG. 3 is a schematic perspective view taken along line II of FIG. 1, FIG. 4 is a schematic perspective view taken along line II-II of FIG. 1, and FIG. 5 is a schematic perspective view cut along line III-III of FIG. In FIG. 1, arrows indicate the flow of compressed air 12.

  In this example, the molding unit is a periodic meat formed by a tandem extruder and a thick portion and a thin portion that are adjacent to each other along the axial direction of the extruded foam 1 and extend in the circumferential direction. A corrugation removal unit for suppressing the occurrence of a thickness difference (referred to as corrugation) and a rotary blade 6 disposed downstream from the corrugation removal unit (sizing member 5) are provided. The lip portion 8 of the die of the tandem extruder is formed in a quadrangular shape, and the resin channel width at one corner is larger than the resin channel width adjacent to the corner.

  The corrugation removal unit is provided in a downstream direction from the die 2 in the extrusion direction, and has a truncated quadrangular pyramid shape for controlling the inner diameter of the hollow portion of the foam 1 in contact with the inner wall of the extruded foam 1. It comprises a sizing member 5 and a cylindrical air ejection unit 4 for circulating compressed air 12 of about 85 to 120 ° C. inside the foam 1 (particularly between the foam 1 and the sizing member 5). Yes. As shown in FIG. 2, the sizing member 5 is disposed with a diameter increasing from the upstream toward the downstream. Further, the die 2 and the sizing member 5 are arranged on the same axis, and both are connected by the air ejection unit 4. The air ejection unit 4 has an ejection port (not shown) that is formed on the tube wall and ejects the compressed air 12 from the mold 3 into the foam 1. When the compressed air 12 from the jet port is circulated inside the foam 1, the internal pressure of the foam 1 can be increased, and the foam 1 becomes a balloon and the generation of corrugation can be suppressed. Even if corrugation occurs in the foam 1, the inner wall of the foam 1 is smoothed at the contact portion with the sizing member 5. If the molding process is continuously performed, the temperature of the sizing member 5 rises, the frictional resistance between the foam 1 and the sizing member 5 increases, and the foam 1 may become difficult to slip. However, in this case, the compressed air 12 acts effectively, and the frictional resistance can be reduced by allowing the compressed air 12 to flow between the foam 1 and the sizing member 5.

  The rotary blade 6 is extruded and cuts the wall portion of the foam obtained through the corrugation removing unit into a slit shape over the entire length in the axial direction. In this example, in the foam 1, the slit-shaped cut portion 9 is formed over the entire length in the axial direction on the wall portion of the corner portion 1 d formed with a thickness larger than the thickness of the adjacent portion (side wall). Yes.

  Among the molding units, use the tandem extruder and corrugation removal unit to melt the thermoplastic resin and the foaming agent and other additives [foaming nucleating agent (foaming aid) and shrinkage inhibitor] as required. When the kneaded thermoplastic resin composition is extruded and foamed at an expansion ratio of about 25 to 35 times with an extruder, the section is a quadrangular cylinder, and the corner portion 1d is adjacent to the corner portion 1d. A foam formed larger than the thickness of the part (side wall) can be obtained. The thickness of the portion (side wall) adjacent to the corner portion 1d is about 7.5 to 9 mm, and the ratio between the thickness of the corner portion 1d and the thickness of the portion (side wall) adjacent to the corner portion 1d is the former / The latter is about 1.5 / 1 to 3.5 / 1 (particularly 2/1 to 3/1). Further, as shown in FIG. 3, the corrugation removal unit is configured to reduce the periodic wall thickness difference (corrugated) formed by the thick portion and the thin portion adjacent to each other in the axial direction and extending in the circumferential direction. The foam 1a in which generation is suppressed can be obtained. Then, the foam 1b in which the cutting part 9 as shown in FIG. 4 was formed by the rotary blade 6 can be obtained.

  The bending unit includes a nozzle 7 disposed downstream from the rotary blade 6. The nozzle 7 is inserted into the foam from the cutting part 9, and the inner wall of one side wall 10 adjacent to the cutting part is cooled by spraying water of about 15 to 45 ° C., thereby reducing the contraction difference between the inner and outer walls. Utilizing this, the one side wall 10 is bent about 30 to 70 ° toward the other side wall 11. In such a bending step (or cooling step), the foam 1c in which the one side wall 10 as shown in FIG. 5 is bent toward the other side wall 11 can be obtained. In addition, a desired protective cover can be obtained by appropriately cutting the foam 1c into a length (about 1 to 3 m).

  The molding unit is usually composed of an extruder equipped with a die, but the extruder is not limited to a multistage extruder such as a tandem extruder, for example, a single-screw extruder (for example, a vent-type extruder), A twin screw extruder (for example, a same direction twin screw extruder, a different direction twin screw extruder, etc.) etc. can be used. The shape of the lip portion of the die is not particularly limited to a quadrangular shape, and may be, for example, a circular shape (for example, a circular shape or an elliptical shape), a polygonal shape (for example, a tri to octagonal shape), or the like. In the case of a shape, it is usually a four to hexagonal shape. By extrusion molding, it is possible to obtain a cylindrical foam having a circular cross section corresponding to the shape of the lip portion of the die. Usually, a cylindrical foam or a cylindrical foam having a quadrangular cross section is manufactured from the standpoints of restoration, attachment to a protected material, and retention. The size and thickness of the foam can be selected according to the type, shape and size of the material to be protected. For example, when the material to be protected is a sign post or the like, the average inner diameter of the foam may be, for example, about 10 to 200 mm, preferably about 15 to 100 mm, and more preferably about 20 to 80 mm. The thickness of the foam may be, for example, 2 to 20 mm, preferably 5 to 15 mm, and more preferably about 7 to 10 mm. In the above example, the thickness of one corner 1d of the cylindrical foam having a quadrangular cross section is formed larger than the thickness of the portion (side wall) adjacent to the corner 1d. The thickness in the width direction or the circumferential direction of the body may be formed uniformly or may be formed non-uniformly.

  The sizing member may have any shape as long as the sizing member can contact the inner wall of the foam and control the inner diameter of the hollow portion of the foam. In the present invention, the shape is not limited to a truncated quadrangular pyramid. For example, a columnar shape such as a columnar shape or a prismatic shape, a conical shape, a conical shape such as a pyramid shape, a truncated conical shape, or another truncated polygonal pyramid shape (for example, It may be a truncated cone shape such as a pentagonal pyramid. The shape of the bottom surface of the sizing member and the cross-sectional shape of the foam may be the same or different, but are usually the same. When the sizing member has a cone shape or a truncated cone shape, the diameter of the sizing member is usually increased from the upstream in the extrusion direction to the downstream direction. You may arrange | position large toward this.

  The air ejection unit 4 is not limited to a hollow body (cylindrical) having a circular cross section, and may be a hollow body having a polygonal cross section (for example, a triangle or an octagon). The temperature of the compressed air ejected from the air ejection unit 4 may be in a range where the formation of the foam is not inhibited and the resin has excellent fluidity in the mold, for example, 70 to 250 ° C., Preferably it may be about 75 to 200 ° C, more preferably about 80 to 150 ° C.

  In the above example, the sizing member 5 and the die 2 are disposed on the coaxial core via the air ejection unit 4, but the axial core may be different without being disposed completely coaxially. The sizing member 5 and the air ejection unit 4 are preferably made of the same or different materials having heat resistance, such as polyfluorinated ethylene resin (for example, polytetrafluoroethylene), heat resistant It can be made of steel, heat-resistant glass or the like, and polytetrafluoroethylene is particularly preferable.

  Moreover, in the said example, in order to cut | disconnect the wall part of a foam in an axial direction, the rotary blade 6 is provided, However, Not only the rotary blade 6 but other cutting means (cutting member) may be provided. . Examples of the cutting means (cutting member) include a slit knife and a cone. Such a cutting means (cutting member) may be disposed in the downstream direction from the sizing member 5 to form a cut portion in the extruded foam. In the above example, the cut portion is formed in the downstream region from the sizing member 5, but the cut portion may be formed between the lip portion 8 of the die and the sizing member 5 or at the lip portion 8 of the die. . In the lip part of the die, for example, a jig with a screw having a conical tip may be screwed into the die and protruded into the lip, or the lip part of the die may be a lip having a cross-sectional shape that is partially opened in advance. Good. However, it is preferable to form the cut portion in the downstream region from the sizing member 5 in terms of formability. The cutting portion is not limited to being formed in a slit shape in the axial direction in the wall portion of the foam. For example, the cutting portion may be formed in a zigzag shape in the axial direction. In addition, with respect to the position where the cut portion is formed, in the above example, in the cylindrical foam having a quadrangular cross section, the cut portion is formed on the wall portion of the corner portion 1d formed with a thickness larger than the thickness of the adjacent portion. Although it was formed over the entire length in the axial direction, it may be formed in an appropriate place according to the shape of the foam. When the cross section of the foam is circular, the cut portion may be formed at the corner of the foam or the side wall of the foam when the cross section of the foam is polygonal. . From the standpoints of restoring properties and bendability, the cut portion is usually formed in a slit shape in the axial direction on the wall portion of the corner portion of the foam. Note that the slit width of the cut portion can be selected according to the desired shape and size (for example, thickness) of the foam. As will be described later, the cut portion is useful for bending one side wall adjacent to the cut portion of the foam to the other side wall. Therefore, the slit width of the cut portion is such that the side walls adjacent to the cut portion are slightly in contact with each other as long as one side wall adjacent to the cut portion of the foam can be bent to the other side wall. However, it is preferable that the one side wall is formed to have a width that can be bent to the other side wall without contacting both side walls. For example, if the width is too small, when the one side wall is bent, one side wall may overlap the top of the other side wall and may not be bent.

  Examples of the thermoplastic resin constituting the foam formed by extrusion foaming include, for example, olefin resins (for example, polyethylene resins, polypropylene resins, methylpentene resins), polystyrene resins [for example, polystyrene (GPPS), Impact polystyrene (HIPS), styrene-acrylonitrile copolymer (AS resin), styrene-acrylonitrile-butadiene copolymer (ABS resin), etc.], vinyl chloride resin (for example, polyvinyl chloride, vinyl chloride-vinyl acetate co Polymers), vinyl acetate resins [for example, polyvinyl acetate, vinyl acetate-ethylene copolymers (EVA resins), etc.], polyvinyl alcohol resins [for example, polyvinyl alcohol (PVA), vinyl alcohol-ethylene copolymers, etc. (EVOH resin) etc.], acrylic Resin [for example, methyl methacrylate resin (PMMA), methyl methacrylate-butadiene-styrene copolymer (MBS resin), etc.], polyacetal resin, polyester resin [for example, polyalkylene arylate (polyethylene terephthalate, PET, poly Butylene terephthalate, PBT, polyethylene-2,6-naphthalate, PEN, etc.)], polycarbonate resins, polyamide resins (for example, polyamide 6, polyamide 6-6, etc.). The thermoplastic resin may be, for example, a thermoplastic polyimide resin, (modified) polyphenylene ether resin (PPE), polyphenylene sulfide resin (PPS), polyether ether ketone (PEEK), etc. Furthermore, the thermoplastic elastomer containing the structural component of the said thermoplastic resin is also contained. These resins may be used alone or in combination of two or more.

  Of these resins, in order to impart excellent flexibility (flexibility), rebound resilience (restorability), impact resistance, etc. to the foam, usually a soft resin such as an olefin resin (especially a polyethylene resin) Resin, polypropylene resin, etc.).

The olefin resin includes an olefin monomer alone or a copolymer, and a copolymer of an olefin monomer and another copolymerizable monomer. The olefin monomer may be a chain olefin monomer or a cyclic olefin monomer, but is usually a chain olefin monomer (for example, ethylene, propylene, 1-butene, Α-C _2-20 chain olefins such as isobutene, 1-pentene, 4-methyl-1-pentene, especially α-C _2-4 chain olefins) are used. These olefinic monomers can be used alone or in combination of two or more.

More specifically, examples of the olefinic monomer alone or copolymer include α-C ₂₋ such as polyethylene (polyethylene such as high density polyethylene, low density polyethylene, linear low density polyethylene) and polypropylene. _20- chain olefin (especially α-C _2-4 chain olefin) homopolymer, α-C _2-20 chain olefin such as ethylene-propylene copolymer (especially α-C _2-4 chain olefin) ) A copolymer can be illustrated. Moreover, as a copolymer of an olefinic monomer and another copolymerizable monomer, for example, a copolymer of an α-C _2-20 chain olefin and another copolymerizable monomer [ For example, ethylene and other copolymerizable monomers such as ethylene-vinyl acetate copolymer (EVA resin), ethylene- (meth) acrylic acid ester copolymer, ethylene- (meth) acrylic acid copolymer, and metal salts thereof. And a copolymer of an α-C _2-4 chain olefin such as a copolymer with a monomer and another copolymerizable monomer]. Among these olefin resins, α-C _2-4 chain olefins alone such as polyethylene (polyethylene such as high density polyethylene, low density polyethylene, linear low density polyethylene), polypropylene, ethylene-propylene copolymer or the like A copolymer, an ethylene-vinyl acetate copolymer (EVA resin), and the like are preferable, and in particular, α-C ₂₋ such as polyethylene (polyethylene such as high-density polyethylene, low-density polyethylene, and linear low-density polyethylene) and polypropylene. _{A 4-} chain olefin homo- or copolymer is preferred. These olefin resins may be used alone or in combination of two or more.

  Foaming agents are roughly classified into volatile foaming agents (physical foaming agents) and degradable foaming agents (chemical foaming agents). Examples of the volatile blowing agent include inorganic blowing agents such as nitrogen, carbon dioxide, oxygen, air, water, propane, butane (n-butane, isobutane), pentane (n-pentane, isopentane, etc.), hexane ( lower aliphatic hydrocarbons such as n-hexane), alicyclic hydrocarbons such as cyclopentane and cyclohexane, aromatic hydrocarbons such as toluene and benzene, chlorohydrocarbons such as methyl chloride and ethyl chloride, and fluorine such as chlorofluorocarbon. Organic foaming agents such as fluorinated hydrocarbons, alcohols such as methanol and 2-propanol, ethers such as dimethyl ether, methyl ethyl ether and petroleum ether, aldehydes such as formaldehyde, and ketones such as acetone and methyl ethyl ketone. Examples of the decomposable foaming agent include inorganic carbonates such as sodium bicarbonate and ammonium carbonate, organic acids such as citric acid, azo compounds such as 2,2′-azobisisobutyronitrile and azodicarbonamide, Examples thereof include sulfonyl hydrazide compounds such as benzenesulfonyl hydrazide and p-toluenesulfonyl hydrazide, nitroso compounds such as N, N′-dinitrosopentamethylenetetramine (DNPT), and azide compounds such as terephthalazide. These foaming agents may be used alone or in combination of two or more.

  The ratio of the foaming agent can be selected according to the type of foaming agent, the desired foaming ratio, and the like. For example, 0.01 to 30 parts by weight, preferably 0.1 to 25 parts by weight with respect to 100 parts by weight of the thermoplastic resin. It may be about 1 to 20 parts by weight, more preferably about 5 to 15 parts by weight.

  Further, a necessary amount of other additives may be contained in order to form a foam. Examples of the foaming nucleating agent (foaming aid) include inorganic acid metal salts such as silicon compounds such as talc, silica and zeolite, metal carbonates or hydrogen carbonate metal salts (calcium carbonate, magnesium carbonate, sodium hydrogen carbonate, etc.). Organic acids (fatty acids) such as citric acid and metal salts thereof (sodium citrate, calcium stearate, aluminum stearate, zinc stearate, etc.), metal oxides such as zinc oxide and aluminum oxide, hydroxide Examples thereof include metal hydroxides such as aluminum. These foam nucleating agents (foaming aids) may be used alone or in combination of two or more. The ratio of the foam nucleating agent (foaming aid) is, for example, 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, more preferably 0.1 to 3 parts by weight with respect to 100 parts by weight of the thermoplastic resin. Part, especially about 0.2 to 2 parts by weight (for example, 0.1 to 1 part by weight). The ratio of the foam nucleating agent is, for example, 0.1 to 500 parts by weight, preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight (for example, 10 to 30 parts by weight) with respect to 100 parts by weight of the foaming agent. Part by weight).

  Examples of the shrinkage preventing agent include esters of fatty acids and polyhydric alcohols, fatty acid amides, and the like. More specifically, esters of fatty acids (eg, lauric acid, myristic acid, palmitic acid, stearic acid, etc.) and polyhydric alcohols (eg, glycerin, xylitol, sorbitol, mannitol, etc.) include, Examples include triglycerides, monostearic acid triglycerides, and the like. Examples of the fatty acid amide include palmitic acid amide and stearic acid amide. These shrinkage inhibitors may be used alone or in combination of two or more. The proportion of the shrinkage inhibitor is, for example, 0.01 to 30 parts by weight, preferably 0.05 to 20 parts by weight, more preferably 0.1 to 15 parts by weight, and particularly preferably 0.1 to 30 parts by weight with respect to 100 parts by weight of the thermoplastic resin. About 5-10 weight part (for example, 1-5 weight part) may be sufficient. The ratio of the shrinkage inhibitor is, for example, 0.01 to 5 parts by weight, preferably 0.02 to 3 parts by weight, more preferably 0.05 to 2 parts by weight (for example, 100 parts by weight of the foaming agent). 0.1-1 part by weight).

  Other additives are not limited to foam nucleating agents (foaming aids) and shrinkage prevention agents, such as bubble regulators, stabilizers (thermal stabilizers, UV absorbers, etc.), antiblocking agents, antifogging agents, Antioxidants, antistatic agents, colorants (dyes, pigments, etc.), coupling agents, curing agents, flame retardants, lubricants, mold release agents, fragrances, plasticizers, biocides (bactericides, bacteriostats, anti-antioxidants Mold, antiseptic, insect repellent, etc.), viscosity modifier, dispersant, filler (calcium carbonate, carbon fiber, etc.), etc. These additives may be used alone or in combination of two or more.

  The foaming agent and other additives (for example, a foam nucleating agent, an anti-shrinkage agent, etc.) may be appropriately added or injected in the molding step as necessary. For example, the foaming agent and other additives may be mixed with the thermoplastic resin in advance and extruded and foamed, or injected into a thermoplastic resin melt-kneaded with an extruder.

  When a resin composition obtained by mixing a thermoplastic resin with a foaming agent and other additives as necessary is extruded and foam-molded from a die, a foam is obtained. The expansion ratio of the foam may be about 2 to 80 times (for example, 10 to 70 times, preferably 15 to 60 times, more preferably 20 to 50 times (particularly 25 to 45 times)). In addition, in the foam obtained by extrusion foam molding, a thickness difference (thickness difference, corrugated) occurs between the thick wall portion and the thin wall portion that are adjacent in the axial direction and extend in the circumferential direction, and the striped pattern is formed. May appear. In particular, the corrugation tends to occur as the foaming ratio of the foam increases. When corrugation occurs, the smoothness of the foam surface is reduced and the appearance is deteriorated. In the apparatus of the present invention, the molding unit may be provided with a corrugation removing unit. For example, the cross-section extruded with a high foaming ratio (for example, about 25 to 45 times) has a rectangular tubular foam Even when the size is 30 mm × 30 mm (inner dimensions) and the inner diameter is 40 mm in the diagonal direction, the periodic thickness difference (thickness difference) formed by the thick and thin portions extending in the circumferential direction is reduced. be able to. For example, the periodic thickness difference (thickness difference) obtained by measuring the thickness of the thick part and the thin part with calipers is 2 mm or less (for example, 0.1 to 1.5 mm), preferably 1 mm or less (for example, 0.1 to 0.8 mm), more preferably 0.5 mm or less (for example, about 0.2 to 0.4 mm), producing a foam having high surface smoothness and an excellent appearance. Can do.

  The bending unit is provided with the nozzle 7 in the above example. However, the bending unit only needs to be able to locally cool the portion to be bent, and is disposed in the downstream direction of the cutting portion and uses the slit-shaped cutting portion. Then, a cooling means (for example, a hose or the like) extending into the hollow portion of the foam may be used.

  In the above example, the inner wall of one of the side walls 10 adjacent to the cut portion is cooled with water, but the fluid for cooling is not limited to water, but other cooling fluid (for example, cooling air). May be. Further, different cooling fluids may be used in combination. Usually, water that can be rapidly cooled is used. The temperature of the cooling fluid may be, for example, about 0 to 60 ° C., preferably 5 to 55 ° C., and more preferably about 10 to 50 ° C.

  When the cooling fluid is used for cooling, the degree of bending of the one side wall 10 can be easily adjusted by adjusting the temperature and the injection amount of the fluid. For example, in the case where the cross section is a quadrangular cylindrical foam, the degree of bending of the one side wall 10 is set to 20 to 20 with respect to the other side wall 11 side from the viewpoints of resilience, mounting force, and retention. You may adjust to 80 degrees, Preferably it is 30-70 degrees, More preferably, it is 35-65 degrees, Especially 40-60 degrees (for example, 45-55 degrees) grade.

  Since the folding unit bends one side wall 10 adjacent to the cut portion to the other side wall 11 side, the folding side wall is not limited to a unit that can be cooled. For example, the one side wall 10 can be bent mechanically. It may be a simple unit.

  The cooling means is formed on the downstream side of the sizing member, and in the extruded foam, an inclined forming member capable of contacting the outer wall of the side wall to be cooled is used to move the side wall from the upstream side to the downstream side. It may be performed in combination with an inclination forming means for continuously inclining the inside of the foam toward the curved direction.

  A series of steps including the forming step and the bending step may be performed individually or continuously, but it is advantageous to perform the two steps continuously from the viewpoint of industrial productivity. is there. The foam obtained through the molding step and the bending step is appropriately length (for example, 0.01 to 10 m, preferably 0.05 to 8 m, more preferably 0.1 to 6 m, particularly 0.5 to 5 m ( For example, when it is cut into about 1 to 3 m), the protective cover of the present invention can be manufactured.

  In the production method of the present invention, the inner wall of one side wall adjacent to the cut portion provided in the foam is cooled, and the one side wall is bent to the other side wall, whereby the foam has a restoring force, a mounting force, and a holding force. And the degree of bending of the one side wall, in other words, the resilience of the foam, the mounting force, the degree of retention, etc., can be adjusted, and it can be applied to a wide range of protected materials. A wearable protective cover can be manufactured.

  In the bending step, if the inner wall of the one side wall is cooled, the foam is cooled and fixed while maintaining the expansion ratio when the foam is formed by extrusion foaming, or the thickness of the cooled one side wall May be larger than the thickness of the side wall adjacent to the one side wall. For example, the present invention includes a foam in which the thickness of the one side wall cooled is 8.5 mm, and the thickness of the side wall adjacent to the one side wall is 7.8 mm. The thickness of the one side wall is about 9% larger than that of the side wall adjacent to the one side wall. By such an action, it is possible to impart a high restoring force, mounting force, and holding property to the foam.

  The protective cover of the present invention is useful for protecting pillars, sign posts, handrails, rod-shaped supports such as water pipes, and the like. In addition, because it has excellent flexibility and high resilience, mounting force, and retention, it can be protected over a long period of time even if the protected material is cylindrical or prismatic, and the protected material has other shapes Even if it has a semicircular cross section or an H-shaped columnar shape, for example, it can be protected with high retainability.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
A protective cover was manufactured using the apparatus shown in FIGS. As thermoplastic resin composition, 100 parts by weight of low density polyethylene (LDPE) (manufactured by Tosoh Corporation, Petrocene 173R), 3 parts by weight of an anti-shrink agent (manufactured by Boehringer Ingelheim Chemicals, Hydrocerol 325), core Agent (Eiwa Chemical Co., Ltd., EE275) 0.8 parts by weight, foaming gas (isobutane / n-butane (weight ratio) = 20/80) 13 parts by weight, the first stage is 65 mm, the second stage is It is melt-kneaded with a 90 mm tandem extruder (die OUT12 mm × 12 mm, IN8 mm × 8 mm), extruded and foam-molded from the die 2, has a square cross section, and the thickness of the corner portion 1 d is set in the axial direction. Foam formed over the entire length larger than the thickness of the portion (side wall) adjacent to the corner portion 1d (foaming magnification: 28.8 times, cross section: 49 mm × 50 mm (outside dimensions To obtain a site thickness (sidewall) 7.8 mm) adjacent to the corner portion 1d. In addition, while 90 degreeC compressed air 12 was distribute | circulated inside the foam, the generation | occurrence | production of corrugation was suppressed using the sizing member 5 comprised by the polytetrafluoroethylene. The rotary blade 6 is used to cut the wall portion of the corner portion 1d into a slit along the entire length in the axial direction, and spray water (20 ° C.) on the inner wall of one side wall adjacent to the cut portion (internal cooling operation). The one side wall was bent 50 ° toward the other side wall. The obtained foam was cut to 1.7 m to obtain a protective cover. The protective cover was attached to four types of test protection materials (15mm square protected material, 25mm square protected material, 35mm square protected material, 25mmφ protected material) that were set up vertically, and the protective cover did not come off. In the case of ◯, the case of evaluation was evaluated as x.

(Comparative Example 1)
Internal cooling operation in the foam formed by extrusion in the same manner as in Example 1 (foaming ratio 27.9 times, cross section 50 mm × 50 mm (outside dimension), portion (side wall) thickness adjacent to corner portion 1d) 8.2 mm) A protective cover was obtained in the same manner as in Example 1 except that the above was not performed. The obtained protective cover was evaluated in the same manner as in Example 1.

  The results of Examples and Comparative Examples are shown in Table 1.

  As is clear from Table 1, the protective cover obtained in the example can protect the material to be protected in a wide range compared to the comparative example.

FIG. 1 is a schematic sectional view showing an example of a protective cover manufacturing apparatus according to the present invention. 2 is a partially cutaway schematic perspective view of the apparatus shown in FIG. FIG. 3 is a schematic perspective view taken along line II of FIG. 4 is a schematic perspective view taken along line II-II in FIG. FIG. 5 is a schematic perspective view taken along line III-III in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a, 1b, 1c ... Foam 1d ... Corner part formed thicker than the thickness of the site | part (side wall) which adjoins 2 ... Die 3 ... Mold 4 ... Air ejection unit 5 ... Sizing member 6 ... Rotary blade 7 ... nozzle 8 ... lip of die 9 ... cutting part 10 ... one side wall adjacent to cutting part 11 ... other side wall adjacent to cutting part 12 ... compressed air

Claims (10)

A method of manufacturing a protective cover for covering a rod-shaped support, which is obtained by extrusion-foaming a thermoplastic resin, and forming a cylindrical foam having an annular cross section and a wall cut in the axial direction. a molding step, cooling the inner wall of one side wall adjacent the cut portion, a method of manufacturing the protective cover via a folding step of bending the side walls of the one on the other side wall side.   The method according to claim 1, wherein in the molding step, a thermoplastic resin is extruded and foamed to form a cylindrical foam having an annular cross section, and then the wall portion of the foam is cut in the axial direction.   In the molding step, a cylindrical foam having a quadrangular cross section is formed using an olefin resin as the thermoplastic resin, and in the bending step, one side wall adjacent to the cut portion of the foam is used as the other side wall. The method of claim 1 wherein the side is bent 30-70 °.   The method according to claim 1, wherein the width of the cut portion is large enough to bend one side wall to the other side wall. The method according to claim 1 , wherein the cooling is performed with at least one selected from water and air.   In the molding process, extrusion is performed at a foaming ratio of 20 to 50 times, and the inner diameter of the hollow part of the foam is controlled by using a member provided in the extrusion direction and in contact with the inner wall of the extruded foam. The method according to claim 1, wherein air that has been compressed inside the body is circulated to suppress periodic wall thickness fluctuations.   The method according to claim 1, wherein the forming step and the bending step are continuously performed.   A protective cover obtained by the method according to claim 1. A thermoplastic resin is extruded and foamed, and the inner wall of one side wall adjacent to the cutting part is cooled by a molding unit for molding a cylindrical foam having a circular cross section and a wall part cut in the axial direction. Te, to produce a protective cover is provided with at least a bending unit for bending the side walls of the one on the other side wall side device. A member for controlling the inner diameter of the hollow portion of the foam in contact with the inner wall of the extruded foam provided in the extrusion direction in the molding unit, and for circulating the compressed air inside the foam The apparatus of Claim 9 provided with the corrugated removal unit comprised with an air ejection unit.

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