KR102377940B1 - Eco-frendly polyproplyene buoy and manufacturing method thereof - Google Patents

Abstract

The present invention relates to an eco-friendly polypropylene buoy and a method for manufacturing the same. According to the present invention, in the marine buoy, including a foam core layer, the foam core layer is at least one of a homopolymer polypropylene (homo PP) resin or a propylene-ethylene copolymer resin polypropylene resin comprising; And there is provided a marine buoy consisting of an additive comprising at least one of ethylene propylene diene monomer rubber (EPDM rubber) or polyolefin elastomer (POE). The present invention can provide a buoy with high productivity and low manufacturing cost and a manufacturing method thereof by manufacturing a buoy comprising a high magnification foamed core layer and a thin non-foamed skin layer using a polypropylene foamed extrusion method in a continuous process. .

Description

ECO-FRENDLY POLYPROPLYENE BUOY AND MANUFACTURING METHOD THEREOF

The present invention relates to an eco-friendly polypropylene buoy and a method for manufacturing the same. Specifically, the present invention relates to an eco-friendly integrated polypropylene buoy with excellent buoyancy and low-temperature impact resistance without generating microplastics and a method for manufacturing the same.

A buoy is an object installed on the water to instruct a route to help a ship safely navigate in the sea or to warn of the presence of dangerous objects on the voyage, such as a reef or a sunken ship. The buoy is used as a mark for fishing grounds, aquaculture farms, and nets, used as a mark in marine terms, or as a route mark for the safe navigation of a ship, and in some cases, it can be used as various lifesaving products for the safety of passengers in an emergency. The buoy is chained to the seabed and fixed in a floating state at a designated sea location regardless of the current. Therefore, buoyancy and cushioning are required.

Conventionally, expanded poly-styrene (EPS), commonly called styrofoam, has been used as a material of the buoy. In the conventional manufacturing method of a buoy using expanded polystyrene, expanded polystyrene beads made of polystyrene resin in which pentane or butane is dissolved as a blowing agent are filled in a buoy-shaped mold. and heating with steam to expand the bead to form a final shape.

Another method of manufacturing a conventional buoy is a synthetic resin raw material such as ethylene vinyl acetate (EVA), polyvinyl chloride (PVC), polyethylene (PE), and a foaming agent, a crosslinking agent, etc. The process of mixing with the additive raw material of This includes the process of manufacturing a buoy of a desired shape.

However, the conventional method of manufacturing a buoy has a problem in that the expanded polystyrene used as a material generates microplastics and causes marine environmental pollution. Accordingly, in recent years, a method for manufacturing a buoy in an environmentally friendly manner in accordance with national policies seeking environmental protection has been developed.

Korean Patent Registration Nos. 10-1155877 and 10-1191376 disclose a method of manufacturing an eco-friendly buoy by adding a coating layer to the surface of the buoy by expanding and then molding a synthetic resin in the form of a bead.

Korean Patent Laid-Open Patent No. 10-1998-0067833 discloses a method for manufacturing a buoy for aquaculture, a process of molding a urethane resin mold by injecting urethane resin into a mold, and a plurality of plural produced by injection molding The process of putting the waste-Styrofoam buoy between the two urethane resin molds and precisely attaching the abutting part of the urethane resin mold, and the foaming urethane stock solution by injecting the expandable urethane stock solution through the foaming urethane stock solution injection hole formed in the mutually attached urethane resin molds A method comprising forming a layer is disclosed.

In addition, buoys made of expanded polypropylene (EPP) material manufactured by attaching polypropylene foam beads with steam were certified as eco-friendly buoys by the National Academy of Fisheries Science and then commercialized. Since foam made of expanded polypropylene material has excellent low-temperature impact resistance enough to be used as a material for bumper bumpers of automobiles, the beads do not fall apart or split even under external forces such as waves and typhoons in the ocean. This is a physical property that is differentiated from the existing expanded polystyrene bead foam buoy. However, the expanded polypropylene buoy has a problem in that the overall weight of the buoy increases and the buoyancy decreases because water is absorbed between the beads. In addition, since the foamed polypropylene bead foam buoy has a high manufacturing cost, there is a problem in that the purchasing attractiveness of the fishermen who actually purchase and use the buoy is lowered.

Therefore, there is a need for an eco-friendly buoy that can replace the conventional expanded polystyrene bead foam buoy, has excellent buoyancy and mechanical properties, and has a low manufacturing cost and a manufacturing method thereof.

Registered Patent No. 10-1155877 (Manufacturing method of eco-friendly buoy) Registered Patent No. 10-1191376 (Environmentally friendly and manufacturing method) Patent Publication No. 10-1998-0067833 (Manufacturing method of eco-friendly buoy)

The present invention aims to solve the following problems in order to solve the above problems.

An object of the present invention is to provide a buoy made of a bead-free polypropylene material and a method for manufacturing the same as a material having excellent buoyancy and low-temperature impact resistance without generating microplastics in an environmentally friendly manner.

An object of the present invention is to provide a buoy with high productivity and low manufacturing cost and a method for manufacturing the same by manufacturing a polypropylene buoy foamed at a high magnification using a continuous process foam extrusion method in a continuous process.

The problems to be solved of the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

The marine buoy according to various embodiments of the present invention includes a foamed core layer, and the foamed core layer is at least one of a homopolymer polypropylene (homo PP) resin or a propylene-ethylene copolymer resin. polypropylene resin including one; and an additive comprising at least one of ethylene propylene diene monomer rubber (EPDM rubber) or polyolefin elastomer (POE).

In the method for manufacturing a buoy for the sea according to various embodiments of the present invention, the primary extruder and the secondary extruder for inducing cooling of the molten polypropylene resin are in series for inducing the mixing of the polypropylene resin and the dissolution of the foaming agent. The process of manufacturing the foamed core layer using a tandem foaming extruder connected by a tandem, and the process of extruding a cylindrical polypropylene foam consisting of only the foamed core layer; or co-extrusion of a cylindrical polypropylene foam including the foamed core layer and the non-foamed skin layer through a co-extrusion die.

The present invention can provide a buoy made of a polypropylene foam material that does not use beads and a manufacturing method thereof as a material having excellent buoyancy and low-temperature impact resistance without generating microplastics in an environmentally friendly manner.

The present invention can provide a buoy with high productivity and low manufacturing cost and a manufacturing method thereof by manufacturing an integrated buoy foamed at a high magnification using a polypropylene foam extrusion method in a continuous process.

Effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those of ordinary skill in the art from the following description.

1 shows an example of a process for manufacturing an integral polypropylene foam buoy according to various embodiments of the present invention.
Figure 2 shows an example of the cross-sectional structure of the integrated high magnification polypropylene buoy manufactured according to the present invention.
Figure 3 shows an example of the cross-sectional structure of the integrated high magnification polypropylene buoy manufactured according to the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement them. The present invention may be implemented in several different forms and is not limited to the embodiments described herein.

A buoy is an object installed on the water to indicate a route to help a ship safely navigate, or to warn of the presence of dangerous objects on the voyage, such as a reef or a sunken ship. The buoy is used as a mark in marine terms such as a fishing ground mark, a fish farm, and a net mark or as a route mark for the safe navigation of a ship, and in some cases, it can be used as various lifesaving products for the safety of the passengers in case of an emergency. Therefore, buoyancy and cushioning are required.

Conventionally, expanded poly-styrene (EPS), commonly called styrofoam, has been used as a material of the buoy. However, expanded polystyrene has a problem of causing environmental pollution by generating microplastics.

The buoys made of expanded polypropylene (EPP), which were recently certified as eco-friendly buoys by the National Academy of Fisheries Science, have problems in that the overall weight of the buoy increases and the buoyancy decreases because water is absorbed between the beads. there is. In addition, the buoy made of expanded polypropylene material has a problem in that the purchase attractiveness is lowered to fishermen who actually purchase and use the buoy because the manufacturing cost is high.

The present invention provides a buoy of a high-magnification integrated polypropylene material using an extrusion foaming method, which is a continuous process, and a method for manufacturing the same. The buoy and its manufacturing method according to the present invention have eco-friendliness because the generation of microplastics is fundamentally prevented, practicality is good because it has excellent low-temperature impact resistance, and it is commercially viable with low manufacturing cost through high productivity.

Various embodiments of the present invention provide a new method for manufacturing a buoy for the sea. The method uses a tandem foam extruder as a facility. The cross section of the foam continuously extruded through the above method has a circular or polygonal structure. Various embodiments of the present invention, as if rice cakes are continuously discharged, when the polypropylene resin composition foam rapidly expanded in volume is discharged as soon as it comes out of the die, it is cooled by a calibrator unit and then cut to a predetermined length. A marine buoy and a method for manufacturing the same are provided.

The marine buoy manufactured according to the present invention includes a non-foamed skin layer and a foamed core layer of a co-extruded integral structure, and the non-foamed skin layer and the foamed core layer use polypropylene resin as a basic material. . Polypropylene resin is known as a safe plastic that has excellent impact resistance and is non-toxic. However, in order to further improve impact resistance at low temperatures, homopolymer polypropylene (homo PP) resin or propylene-ethylene resin It is composed of a polypropylene resin including at least one of a propylene-ethylene copolymer resin. Alternatively, an impact reinforcing material such as a thermoplastic elastomer or ethylene propylene diene monomer rubber (EPDM rubber) resin may be blended. In this case, the final integrated polypropylene foam buoy has very good low-temperature impact properties, so it is not easily broken even in typhoons or rough waves, and has the characteristics to withstand, and it is possible to prevent the generation of microplastics.

In the method for manufacturing a buoy for the sea according to various embodiments of the present invention, the primary extruder and the secondary extruder for inducing cooling of the molten polypropylene resin are in series for inducing the mixing of the polypropylene resin and the dissolution of the foaming agent. It includes a process of manufacturing the foamed core layer using a tandem foaming extruder connected by a tandem, and a process of co-extruding a cylindrical polypropylene foam including the foamed core layer and the non-foaming skin layer. In addition, the present invention includes an integrated polypropylene foam buoy made of only high-magnification polypropylene foam without a non-foaming skin layer and a method for manufacturing the same.

1 shows an example of a process for manufacturing an integral polypropylene foam buoy according to various embodiments of the present invention.

Specifically, Figure 1 shows a process for manufacturing an integral polypropylene foam buoy without microplastic generation using a tandem foam extruder according to various embodiments of the present invention.

Referring to Figure 1, the process for manufacturing the integral polypropylene foam buoy according to various embodiments of the present invention uses a co-extrusion foaming facility and a cooling device.

1 illustrates a co-extrusion foaming process using a co-extrusion die 14, but this is only an example. In some cases, unlike FIG. 1 , polypropylene buoyancy foams without a non-foamed skin layer can be made by not using a co-extrusion die.

The conventional expanded polystyrene bead foam buoy has a density of about 30 kg/m ³ and is manufactured to be lightweight, so workability and handling at sea are good. In addition, EPS bead foam buoys provide excellent buoyancy and thus float well over seawater.

In various embodiments of the present invention, a tandem foam extruder is used to manufacture an integrated polypropylene buoy equivalent to that of the expanded polystyrene bead foam buoy at a low cost. The extrusion method is known as the lowest cost and high productivity plastic processing method.

The basic plastic material used in various embodiments of the present invention is polypropylene (PP). The unique properties of polypropylene materials, that is, excellent impact resistance, can be excellent properties that can fundamentally prevent the occurrence of microplastics. For this reason, unlike the conventional EPS bead foam buoy, the integrated high magnification polypropylene buoy comprising a foaming layer and a non-foaming layer has the advantage of not being broken or split by an external force.

Due to the nature of the use, the buoy floats well on seawater and has to give buoyancy to other objects, so under the condition that it has the mechanical strength required for the specification, the lower the density, the more advantageous. That is, the higher the magnification foam buoy, the greater the floating effect. Polypropylene resin is known as a plastic material that is very difficult to expand at high magnification in the prior art. This is because, since the melt strength of the polypropylene resin is fundamentally low, the polypropylene resin does not have the rheological properties necessary for good foaming properties. In order to overcome the limitations of the polypropylene resin, in various embodiments of the present invention, a polypropylene resin having excellent foamability is prepared in-line during the process through a chemical bridging reaction, and the resin is directly prepared. High-magnification extrusion foaming is performed by foaming.

For high-magnification extrusion foaming, a tandem foaming extruder is essential.

1, the tandem foam extruder has a form in which two extruders 11 and 13 are connected in series. The primary extruder 11 induces kneading of raw materials and dissolution of a blowing agent, and the secondary extruder 13 effectively induces cooling of the molten resin to maximize foaming characteristics. In addition, the gas injection port of the foaming agent pump 12 is processed so that the foaming agent can be injected in the middle of the primary extruder 11 . A co-extrusion die 14 is mounted at the end of the tandem foam extruder. Although not shown in FIG. 1 , a general die may be used instead of the co-extrusion die 14 . In this case, a cylindrical foam without a non-foamed skin layer is extruded.

The sub-extruder 17 for supplying the polypropylene resin used for the non-foaming layer is directly connected to the body of the co-extrusion die 14 by a connecting pipe. A diverter valve is installed between the connection pipe and the coextrusion die 14 so that the non-foaming layer resin containing no foaming agent is applied in one layer on one surface of the foaming layer, or one layer on both surfaces of the foaming layer. It is possible to select and control the flow direction of the resin so that it is formed in a total of two layers. Here, the co-extrusion die 14 is suitable for the tubular co-extrusion die 14 in order to suppress the problem of wrinkling of the buoy.

Polypropylene resin, which is known to be difficult to expand and foam at high magnification, needs reforming to increase its melt strength. Since the polypropylene resin has a long linear structure, strain hardening does not occur in the foam expansion process, and open cells are mainly formed instead of closed cells. Therefore, in order to increase the melt strength, it is necessary to make a long chain branch in the polypropylene molecule having a linear structure. It is one of the technical features of the present invention to induce this molecular structure reforming operation in-line in the primary extruder 11 of the tandem foaming extruder. By reforming the polypropylene resin in-line in the primary extruder 11, it is possible to manufacture an integral polypropylene foam buoy in a continuous process.

For reforming the polypropylene resin, the raw material input to the primary extruder 11 for kneading the raw material and dissolving the foaming agent is polypropylene resin, a nucleating agent, a foaming agent, and other functional additives.

According to various embodiments of the present invention, as the polypropylene resin, a homopolymer polypropylene (homo PP) resin or a propylene-ethylene copolymer resin may be added alone or in combination. As an embodiment, the melt index (MI) of the polypropylene resin is preferably 2 to 10 g/10 min (ASTM (American society for testing and materials) D1238, 2.16 kg).

In addition, an additive of a rubber component that can further supplement low-temperature impact resistance by blending with the polypropylene resin may be added together with the polypropylene resin. That is, in order to further supplement the low-temperature impact resistance of the polypropylene resin, an additive of a rubber component may be added together with the polypropylene resin. For example, ethylene propylene diene monomer rubber (EPDM rubber) or polyolefin elastomer (POE) may be added together with the polypropylene resin as an additive of the rubber component.

According to various embodiments of the present invention, inorganic particles such as talc, calcium carbonate, and aluminum hydroxide may be added as a nucleating agent. Nucleating agents can make the foam cells small. In one embodiment, inorganic particles may be added together with the polypropylene resin as a nucleating agent. In one embodiment, the amount of the nucleating agent is preferably 0.5 to 5.0 parts by weight based on 100 parts by weight of the resin.

According to various embodiments of the present invention, as the blowing agent, a physical blowing agent is suitable for high-magnification foaming, and a hydrocarbon blowing agent having high solubility in the polypropylene resin is preferable. That is, as the foaming agent, a hydrocarbon-based foaming agent having high solubility in the polypropylene resin is preferable. For example, carbon dioxide, propane, butane, pentane, etc. are suitable blowing agents with low cost. In one embodiment, carbon dioxide (carbon dioxide), propane (propane), butane (butane), pentane (pentane), or at least one of a mixture thereof is selected as a foaming agent to inject 3 to 30 parts by weight based on 100 parts by weight of the resin. can Since the blowing agent containing propane, butane, pentane, or a mixture thereof is a raw material vulnerable to fire, extreme care must be taken in its handling and storage.

In addition, within 3 parts by weight based on 100 parts by weight of the resin, an ultraviolet stabilizer, UV stabilizer, or antioxidant, or colored pigments for imparting color, which increases resistance to UV rays can be added additionally.

Finally, an additive that helps to improve foamability by changing the molecular structure of the polypropylene resin from a linear to a branched structure should be added. According to various embodiments of the present invention, organic peroxides are preferable, and specifically, dicumyl peroxide, didecanoyl peroxide, dibenzoyl peroxide, dilauroyl peroxide, cyclic trimer peroxide, tert-amyl peroxyneodecanoate, tert-butyl peroxyneodecanoenite ( tert-butyl peroxyneodecanoate, dicetyl peroxydicarbonate, cumyl peroxyneodecanoate, sec-butyl peroxydicarbonate It is preferable to use it by mixing. According to an embodiment, the organic peroxide is preferably added in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of the resin.

When the above-mentioned raw materials are melted and kneaded into a uniform melt in the primary extruder 11 of the tandem foaming extruder, the structure of the polypropylene molecule is changed from a linear structure to a long branched chain by a radical reaction of a peroxide. A reaction that transforms into a structure with (long chain branch) occurs. For this, a single screw extruder or a twin screw extruder may be used in the form of the primary extruder 11 .

Since it is necessary to precisely control the chemical reaction in which the structure of the polypropylene molecule is transformed from a linear structure to a structure having a long chain branch, the temperature precision of the primary extruder 11 is very important. The screw structure of the primary extruder 11 must have a structure suitable for uniform raw material kneading. The polypropylene resin melt melted and modified in the primary extruder 11 enters the secondary extruder 13 through the cross pipe.

The secondary extruder 13 maximizes the foaming characteristics of the polypropylene resin melt by gradually and precisely cooling the polypropylene resin melt that has flowed and moved from the first extruder 11 . In particular, it helps to create a closed cell structure without the cell bursting during the cell growth during the foaming process. When a closed cell content of 80% or more is obtained, the mechanical strength of the overall foam buoy can be obtained at an excellent level.

The polypropylene resin melt cooled through the secondary extruder 13 and maximized melt strength is discharged into the air at atmospheric pressure while passing through the tubular co-extrusion die 14 or a general die. At this time, the polypropylene resin melt is a thermodynamically unstable material because a large amount of foaming gas is dissolved at high temperature and high pressure. As soon as the polypropylene resin melt passes through the tubular co-extrusion die 14 or a general die and comes out to normal pressure, the solubility of the foaming gas drops sharply and phase separation occurs, and countless fine foamed cells are formed. The diffusion phenomenon of the foaming gas is also involved in this process, and the size and structure of the cells are determined by the diffusion rate of the foaming gas and the numerical density of the foaming cells. As a result, the polypropylene foam exiting through the tubular co-extrusion die 14 or ordinary die rapidly expands, resulting in high-magnification foaming.

According to various embodiments of the present invention, a tubular coextrusion die 14 is used to form a non-foamed skin layer on the surface of the polypropylene foam to enhance the surface strength and durability of the polypropylene buoy. The non-foaming skin layer constituted on the surface of the polypropylene buoy preferably uses a polypropylene resin in the same way as the foamed core layer from the viewpoint of recycling. In addition, according to one embodiment, in order to ensure long-term durability of the buoy, functional additives such as UV stabilizers and antioxidants may be included in a high concentration in the non-foaming skin layer.

According to another embodiment, although not shown in FIG. 1 , a general die may be used instead of the co-extrusion die 14 . In this case, a cylindrical foam without a non-foamed skin layer is extruded.

The high magnification integral polypropylene foam in the form of a cylinder discharged through the tubular co-extrusion die 14 of the tandem foaming extruder enters the calibration unit 15 to determine cooling and outer diameter. In order to speed up the cooling of the polypropylene foam, the calibration unit 15 is preferably in the form of a water tank. According to an embodiment, by pulling the outside of the polypropylene foam with a vacuum, it may be adsorbed to the calibration unit 15 having a fixed outer diameter. Polypropylene foam has a slow heat transfer, so cooling takes a lot of time. Accordingly, the length of the calibration unit 15 is preferably 10 to 100 meters.

The high-magnification integrated polypropylene foam in the form of a cylinder, which has passed through the calibration unit 15 and has been cooled, is cut to a predetermined length by the hot wire cutter 16 . The cut cylindrical polypropylene foam can be further processed to make a groove in the body, and the edge portion can be processed into a curved shape. A string can be tied to the body of the polypropylene foam through the grooves made in the cut polypropylene foam.

The high magnification integral polypropylene foam cut to a certain length by the hot wire cutter 16, or the high magnification integral polypropylene foam after additional processing after being cut to a certain length by the hot wire cutter 16, is an integral polypropylene without microplastics. It can be used as a foam buoy 18 .

Figure 2 shows an example of the cross-sectional structure of the integrated high magnification polypropylene buoy manufactured according to the present invention.

Specifically, FIG. 2 shows the cross-sectional structure of a cylindrical foam that does not include a non-foamed skin layer, although not shown in FIG. 1 , using an ordinary die instead of the co-extrusion die 14 .

The integral high magnification polypropylene buoy 20 made in accordance with various embodiments of the present invention includes a polypropylene high magnification foam core layer 19 .

Since the integrated high magnification polypropylene buoy 20 of the cylindrical shape is not a bead type, it is not broken even by the external force of waves and typhoons and has very good impact resistance.

According to an embodiment, the density of the total polypropylene buoy may be 20 to 200 kg/m ³ . According to an embodiment, the closed cell content of the foam core layer may be 50 to 100%.

Figure 3 shows an example of the cross-sectional structure of the integrated high magnification polypropylene buoy manufactured according to the present invention.

Specifically, FIG. 3 shows a cross-sectional structure of a cylindrical foam including a non-foamed skin layer extruded through the coextrusion foaming process of FIG. 1 .

The integral high magnification polypropylene buoy 23 manufactured according to various embodiments of the present invention includes a thin non-foamed polypropylene skin layer 21 and a polypropylene high magnification foamed core layer 22 . The non-foamed polypropylene skin layer 21 is relatively thin compared to the foamed core layer 22 . The surface strength and durability of the integral high magnification polypropylene buoy 22 can be enhanced through the non-foamed polypropylene skin layer 21 .

Since the integrated high magnification polypropylene buoy 23 of the cylindrical shape is not a bead type, it is not broken even by the external force of waves and typhoons and has very good impact resistance.

According to an embodiment, the density of the foam core layer may be 15 to 100 kg/m3. According to an embodiment, the density of the total polypropylene buoy may be 20 to 200 kg/m ³ . The thickness of the non-foamed skin layer may be from 2 to 6,000 micron meters (μm). According to an embodiment, the closed cell content of the foam core layer may be 50 to 100%.

Hereinafter, an embodiment of the present invention will be described. The following examples are only examples of the present invention, and the present invention is not limited to the following examples.

(Example 1)

The used tandem foaming extruder has a structure in which a 200 mm diameter single screw extruder (primary extruder) and a 250 mm screw diameter single screw extruder (secondary extruder) are continuously connected. In addition, it is a form in which the gas injection hole is processed so that the injection of the physical foaming agent is possible in the middle of the primary extruder. The end of the tandem foam extruder was equipped with a tubular coextrusion die. The sub-extruder that supplies the polypropylene resin used for the non-foaming layer uses a single screw extruder with a diameter of 80 mm, and is directly connected to the tubular co-extrusion die and the connecting pipe.

As the polypropylene resin used for the foaming layer and the non-foaming layer, an ethylene-propylene copolymer resin having a melt index of 3 g/10 min (ASTM D1238) was used. Based on 100 parts by weight of the polypropylene resin, 10 parts by weight of iso-butane as a foaming agent, 1 part by weight of dicumyl peroxide as a molecular structure modifier, and 1 part by weight of talc as a nucleating agent were added. . The primary extruder temperature conditions were 160 degrees-180 degrees-200 degrees-220 degrees-220 degrees-220 degrees-220 degrees Celsius, and the terminal pressure was operated at 200 bar level. The secondary extruder temperature conditions were 200 degrees-180 degrees-170 degrees-160 degrees-140 degrees-140 degrees Celsius, and the terminal pressure was operated at 150 bar level. The sub-extruder temperature conditions for making the non-foaming skin layer were 160 degrees-180 degrees-200 degrees-220 degrees-220 degrees-220 degrees-220 degrees Celsius, and the end pressure was operated at 200 bar level. The high magnification integral polypropylene foam in the form of a cylinder discharged through the tubular coextrusion die has a non-foaming skin layer, is a foam with a total diameter of 600 mm, is cooled while passing through the calibration unit, and has excellent surface quality. The thickness of the non-foaming skin layer of the foam buoy is 2 mm, and the density of the polypropylene foam core layer inside is 35 kg/m ³ . The foam from the calibration unit is cut to a length of 1200 mm by a hot wire cutter. The cut cylindrical foam is grooved in the body, and the edge is further processed into a curved surface. After processing, a high-magnification integral polypropylene foam product is finally produced.

The high magnification integrated polypropylene foam manufactured in this way is not a bead type, so it can be used as an eco-friendly buoy without the risk of microplastics. In addition, the high magnification integrated polypropylene foam does not break even under the external force of waves and typhoons and has very good impact resistance. Since the high magnification integral polypropylene foam is manufactured in a single continuous process, the overall manufacturing cost is also low. Therefore, it is possible to economically manufacture an eco-friendly buoy that can replace the bead foam buoy of the conventional expanded polystyrene material.

(Example 2)

All conditions were the same as in Example 1, except that the primary extruder of the tandem foaming extruder used was not a single screw extruder, but a twin screw extruder having a diameter of 55 mm. As a result, the kneading of the raw materials is improved inside the primary extruder, and the molecular structure reforming reaction of the polypropylene resin can proceed more efficiently. The cylindrical high-magnification integrated polypropylene foam discharged through the tubular co-extrusion die has a non-foaming skin layer and is cooled while passing through the calibration unit as a foam with a total diameter of 600 mm, and excellent surface quality is obtained. The thickness of the non-foaming skin layer of the foam buoy is 2 mm, and the density of the polypropylene foam core layer inside is 30 kg/m ³ . The foam from the calibration unit is cut to a length of 1200 mm by a hot wire cutter. The cut cylindrical foam is grooved in the body, and the edge is further processed into a curved surface. After processing, a high-magnification integral polypropylene foam product is finally produced. By using a twin screw extruder as the primary extruder, it was possible to obtain excellent foaming properties than in Example 1, and the foam density could be reduced to 30 kg/m ³ .

It will be apparent to those skilled in the art that the present invention can be embodied in other forms without departing from the spirit and essential characteristics of the present invention. Accordingly, the above embodiments should be considered in all respects as illustrative and not restrictive. The scope of the present invention should be determined by a reasonable interpretation of the appended claims and all possible changes within the equivalent scope of the present invention.

11: primary extruder 12: blowing agent pump
13: secondary extruder 14: co-extrusion die;
15: calibration unit 16: hot wire cutter
17: sub extruder 18: integral polypropylene buoy
19: polypropylene foam core 20: integral polypropylene buoy
21: non-foamed polypropylene skin layer 22: polypropylene foamed core
23: Integral polypropylene buoy

Claims (9)

In a marine buoy,
Cylindrical foam core layer; and
A non-foamed skin layer having an integral structure with the foamed core layer co-extruded together with the foamed core layer through a co-extrusion die,
The foamed core layer and the non-foamed skin layer,
a polypropylene resin comprising at least one of a homopolymer polypropylene (homo PP) resin or a propylene-ethylene copolymer resin; and
A first additive comprising ethylene propylene diene monomer rubber (EPDM rubber), a second additive comprising a mixture of dicumyl peroxide and didecanoyl peroxide,
The non-foaming skin layer is manufactured using a sub-extruder directly connected to the body of the co-extrusion die, and thus has a thickness of 2 to 299 microns (μm).
maritime buoy.
delete According to claim 1,
The density of the marine buoy is 20 to 200 kg / m ³ of,
maritime buoy.
delete According to claim 1,
The closed cell content of the foam core layer is 50 to 100%,
maritime buoy.
A method for manufacturing a marine buoy, comprising:
To prepare a foamed core layer using a tandem foaming extruder in which a primary extruder for inducing kneading of the polypropylene resin and dissolution of the foaming agent and a secondary extruder for inducing cooling of the molten polypropylene resin are connected in series process and
In order to perform kneading of the polypropylene resin and dissolution of the foaming agent, a first additive, dicumyl peroxide, and die including ethylene propylene diene monomer rubber (EPDM rubber) in the primary extruder The process of adding a second additive consisting of a mixture of decanoyl peroxide,
A process of preparing a non-foamed skin layer of polypropylene having a thickness of 2 to 299 microns (μm) using a sub-extruder directly connected to the body of a co-extrusion die;
Co-extruding the polypropylene foam in the form of a cylinder including the foam core layer and the non-foaming skin layer through the co-extrusion die connected to the tandem foam extruder and the sub-extruder,
method.
7. The method of claim 6,
The foaming agent input to the primary extruder,
Containing at least one of carbon dioxide, propane, butane, pentane, or a mixture thereof,
3 to 30 parts by weight relative to 100 parts by weight of the polypropylene resin,
method.
delete 7. The method of claim 6,
The process of cooling the polypropylene foam using a calibration unit;
The process of cutting the cooled polypropylene foam to a predetermined length using a hot wire cutter;
Further comprising the step of forming a groove capable of tying a string in the body of the cut polypropylene foam,
wherein the calibration unit is 10 to 100 meters long, is in the form of a water bath filled with water, and is configured so that the outside of the polypropylene foam is adsorbed into the inside of the calibration unit with a vacuum,
method.

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