Manufacturing method of resin foam particles

Abstract

To provide a method for producing resin foam particles for the purpose of effectively utilizing a polyolefin-based resin base material among synthetic resin base materials contained in recovered materials for fishery such as a fishing net, a rope for fishing, and a fishing line.SOLUTION: A method for producing resin foam particles includes a melting and mixing step A of melting and mixing a specific propylene-based random copolymer, and a specific recovered polyolefin-based resin, and forming the mixture into a molten mixed resin, a resin particle production step B of obtaining resin particles from the molten mixed resin, and a foaming step C of foaming the resin particles and obtaining resin foam particles, wherein the recovered polyolefin-based resin (II) is a substance obtained by pelletizing one or more recovered materials for fishery selected from the group consisting of a fishing net, a fishing line and a rope for fishing, and has an ash content of 3 mass% or less, and the melting and mixing step A melts and mixes a specific amount of a random copolymer (I) and a specific amount of a recovered polyolefin-based resin (II).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for producing expanded resin beads, and more particularly to a method for producing expanded resin beads containing a raw material recovered from marine products. [Background technology]

[0002] In recent years, marine pollution caused by plastic waste has become serious. Some of the plastic waste has been used in fishing and fishing and then discarded, which has caused serious marine pollution. For example, fishing nets, fishing lines, ropes, etc. used in fishing in the ocean or rivers may break during use and be left in the ocean as they are, drifting in the ocean as garbage, and how to dispose of these has become a social issue.

[0003] Plastic waste is also generated in set net fishing. Set net fishing is a fishing method in which a fence net, a playground net, a climbing net, a box net, and a safe net are set up along the fish's migration route, and fish are caught by guiding them through the fence net, the playground net, the climbing net, and the box net into the safe net. The fishing net, especially the sinker rope, has weights such as lead woven into it to adjust buoyancy. Therefore, how to collect plastic waste containing lead and other substances has become an issue.

[0004] In addition, at fishing net manufacturing factories, fishing net waste is generated when new fishing nets are manufactured. In addition, fishing nets are repaired at the same factories, and fishing net waste is also generated during the repair of fishing nets. The fishing net waste generated at fishing net manufacturers is unnecessary. However, since no suitable method for reusing it has been found, it is sometimes discarded as garbage, and effective ways of using it are being sought. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of such problems, and an object of the present invention is to provide a method for producing resin foam particles that aims to effectively utilize polyolefin-based resin materials contained in synthetic resin materials contained in fishery recovered materials such as fishing nets, fishing ropes, and even fishing lines. [Means for solving the problem]

[0006] According to the present invention, there is provided a method for producing expanded resin beads as described below. [1] A melt mixing step (A) of melt-mixing a propylene random copolymer (I) having a melting point of 120°C or more with a recovered polyolefin resin (II) having a melting point of 125°C or more and 170°C or less to obtain a melt mixed resin; a resin particle production step (B) of obtaining resin particles from the molten mixed resin; and (C) an expansion step of expanding the resin particles to obtain expanded resin particles, The recovered polyolefin resin (II) is a pellet made from one or more recovered fishery products selected from the group consisting of fishing nets, fishing lines, and fishing ropes, and has an ash content of 3 mass% or less; In the melt mixing step (A), 40% by mass or more and 95% by mass or less of the random copolymer (I) and 5% by mass or more and 60% by mass or less of the recovered polyolefin-based resin (II) are melt mixed (provided that the total amount of the propylene-based random copolymer (I) and the recovered polyolefin-based resin (II) is 100% by mass). [2] The method for producing expanded resin beads according to the above item 1, wherein the propylene random copolymer (I) has a melt flow rate of 1 g / 10 min or more and 10 g / 10 min or less at 230° C. under a load of 2.16 kg, and the recovered polyolefin resin (II) has a melt flow rate of 230° C. under a load of 2.16 kg that is smaller than the melt flow rate of the propylene random copolymer (I). [3] The method for producing expanded resin beads according to the above item 1 or 2, wherein the recovered polyolefin resin (II) comprises a high-density polyethylene resin having a melting point of 125°C or higher and 145°C or lower. [4] A method for producing resin foamed beads according to any one of the above items 1 to 3, characterized in that a first DSC curve measured by heating and melting the resin foamed beads as a test piece at a heating rate of 10°C / min from 30°C to a heating end temperature 30°C higher than the end of the melting peak at a heating rate of 10°C / min based on heat flux differential scanning calorimetry in accordance with JIS K7121-1987 has two or more melting peaks, and the two or more melting peaks include a melting peak specific to the resin constituting the resin foamed beads and a high-temperature melting peak having a peak temperature higher than the peak temperature of the specific melting peak, and the resin foamed beads are then held at the heating end temperature for 10 minutes, cooled to 30°C at a cooling rate of 10°C / min, and heated and melted again at a heating rate of 10°C / min to a temperature 30°C higher than the end of the melting peak at a heating rate of 10°C / min, in which the high-temperature melting peak does not appear in the second DSC curve measured. [5] The method for producing expanded resin beads according to any one of the above items 1 to 4, characterized in that the resin beads are multi-layered resin beads having a core layer made of a mixture of a propylene-based random copolymer (I) and a recycled polyolefin-based resin (II) as a base resin, and a coating layer made of a polyolefin-based resin (III) as a base resin coating the core layer. [6] In the expansion step (C), the resin particles are expanded to a bulk density of 10 kg / m 3 More than 100kg / m 3 6. A method for producing expanded resin beads according to any one of 1 to 5 above, characterized in that the following expanded resin beads are obtained. [7] The method for producing expanded resin beads according to any one of the above items 1 to 6, wherein the melting point of the propylene random copolymer (I) is 135°C or higher and 160°C or lower. Effect of the Invention

[0007] According to the present invention, by producing expanded resin particles containing a polyolefin resin obtained from recovered fishery products such as fishing nets, fishing lines, fishing ropes, etc., it is possible to effectively reuse the recovered fishery products. In addition, by reusing recovered fishery products such as fishing nets, fishing lines, fishing ropes, etc., it is possible to prevent the fishing nets, fishing lines, fishing ropes, etc. from being burned as waste and reduce carbon dioxide emissions. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of a first DSC curve in heat flux differential scanning calorimetry of the expanded beads of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The method for producing expanded resin beads of the present invention will be described in detail below. The method for producing expanded resin beads (hereinafter also simply referred to as expanded beads) of the present invention is a method comprising a melt-mixed resin production step (A), a resin particle production step (B), and an expansion step (C). The melt mixing step (A), the resin particle production step (B), and the foaming step (C) will be described in this order.

[0010] In the melt mixing step (A), a propylene random copolymer (I) having a melting point of 120° C. or higher and a recovered polyolefin resin (II) having a melting point of 125 to 170° C. are melt mixed to form a melt mixed resin. In detail, the propylene random copolymer (I), the recovered polyolefin resin (II), and additives such as a cell regulator, which are blended as necessary, are fed to an extruder and melt kneaded to form a melt mixed resin.

[0011] In the melt-mixed resin production step (A), a melt-kneading method using a conventionally known extruder can be adopted. In order to perform uniform kneading, it is preferable to mix various resins in advance and then perform extrusion. The melt kneading is preferably performed using a single screw extruder or a twin screw extruder equipped with a high dispersion type screw such as a Dulmage type, a Maddock type, or a Unimelt type.

[0012] Next, the propylene random copolymer (I) having a melting point of 120° C. or higher will be described. The propylene random copolymer (I) (hereinafter also simply referred to as copolymer (I)) refers to a propylene random copolymer containing 50% by mass or more of structural units derived from propylene. Specific examples of the copolymer include random copolymers of propylene and ethylene or α-olefins having 4 or more carbon atoms, such as propylene-ethylene random copolymer, propylene-butene random copolymer, and propylene-ethylene-butene random copolymer, propylene-acrylic acid random copolymer, and propylene-maleic anhydride random copolymer. The propylene random copolymer preferably contains 70% by mass or more of structural units derived from propylene, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0013] The melting point of the propylene random copolymer (I) is 120° C. or higher. To obtain expanded beads having excellent heat resistance, the melting point is preferably 125°C or higher, more preferably 130°C or higher, even more preferably 135°C or higher, and particularly preferably 140°C or higher. The upper limit is generally 160°C, and from the viewpoint of excellent moldability, 158°C is preferable, and 155°C is more preferable. Among the copolymers (I) having a melting point within these ranges, it is preferable to use a propylene-based random copolymer (I) having a melting point of 135°C or higher and 160°C or lower, since the resulting expanded beads will have excellent moldability, heat resistance, etc.

[0014] In this specification, the melting point of a resin is measured as follows. Based on JIS K7121:2012, the specimen is conditioned (2) by a certain heat treatment and the temperature is raised at 10°C / min to obtain a melting peak. The temperature at the apex of the melting peak obtained is taken as the melting point. If two or more melting peaks appear, the temperature at the apex of the melting peak with the largest area is taken as the melting point.

[0015] The flexural modulus of the propylene random copolymer (I) is preferably 600 MPa or more, more preferably 800 MPa or more, since shrinkage of the molded article immediately after molding can be suppressed and a molded article with excellent dimensional accuracy can be easily obtained. On the other hand, in order to maintain the cushioning performance of the expanded bead molding, the flexural modulus of the propylene random copolymer (I) is preferably 1200 MPa or less, more preferably 1000 MPa or less.

[0016] The flexural modulus in this specification can be determined based on JIS K 7171:2016 by preparing a test specimen (test specimen dimensions: length 80 mm, width 10 mm, thickness 4 mm) by injection molding.

[0017] Next, the recovered polyolefin resin (II) having a melting point of 125° C. or higher and 170° C. or lower will be described. The recovered polyolefin resin (II) (hereinafter, also simply referred to as recovered resin (II)) is obtained by pelletizing one or more fishery recovered materials selected from the group consisting of fishing nets, fishing lines, and fishing ropes. The fishery recovered materials are generated during the manufacture or repair of fishing nets, etc., and may include fishing nets that have not yet been used. However, it is preferable that the recovered materials are fishing plastic waste collected from fishing nets, fishing lines, or fishing ropes that have already been used in the sea, rivers, lakes, etc. In particular, fishing plastic waste used in the sea has been soaked in seawater for a long time, causing salt to adhere to it and becoming soaked in it, and foreign matter such as shellfish and seaweed to adhere to it, so in the past it was disposed of in landfills. Therefore, it is more preferable that the fishery recovered materials are fishing plastic waste that have already been used in the sea, because this can reduce landfill waste.

[0018] The recovered resin (II) may be recovered from any one of fishing nets, fishing lines, and fishing ropes, or may be recovered from two or more of them.

[0019] The marine product recovered can be pelletized by any of the conventional methods known in the art. For example, the fishery recovered material can be crushed, fed into an extruder, heated and kneaded, and the resulting molten resin extruded into strands, cooled by passing through water, and cut into pellets to produce a pelletized recovered raw material.

[0020] When the fishery recovered material is crushed, it is preferable to use a crusher to make it easier to feed to the extruder. The crusher may be a known device, such as a normal shear crusher or impact crusher.

[0021] In producing the recovered polyolefin resin (II), when the fishery recovered materials consist of used fishery plastic waste such as fishing nets, fishing lines, and fishing ropes, it is important to remove the dirt. Specifically, the collected fishery plastic waste is dirty and has foreign matter such as metals, labels, and connectors attached thereto, so it is preferable to wash the dirt and remove the foreign matter before pelletizing. This can increase the productivity of the pellet production, and further, in the resin particle production step (B) described below, when the molten mixed resin is extruded, strand breakage is less likely to occur, thereby increasing the productivity of the resin particle production. In addition, when the expanded beads are molded in a mold to produce an expanded bead molding, the expanded beads have excellent moldability. A magnet is preferably used to remove the metal. Water, hot water, detergent, etc. are used for cleaning, and a high-pressure cleaner is also preferably used.

[0022] The degree of dirt contained in the recovered polyolefin resin (II) is represented by the amount of ash. The amount of ash contained in the recovered polyolefin resin (II) is 3% by mass or less, preferably 2% by mass or less, and more preferably 1.5% by mass or less. The fact that the amount of ash is low means that the recovered polyolefin resin (II) is particularly less dirty among those that have been subjected to the above-mentioned foreign matter removal and cleaning. Examples of ash contained in the recovered polyolefin resin (II) include calcium, sodium, silicon, and the like. Specifically, for example, carbonates and sulfates of Ca, Na, and Si derived from seawater are included. In the expanded particles of the present invention, it is considered that the presence of trace amounts of these acts as a bubble nucleating agent and contributes to lowering the apparent density during expansion (improving the expansion ratio). From the above viewpoint, the amount of ash contained in the recovered polyolefin resin (II) is preferably 0.05% by mass or more.

[0023] The ash content can be measured based on JIS K 6226-2. For example, a thermogravimetric analyzer TGA701 manufactured by LECO can be used as a measuring device. Approximately 5 g of the recovered resin (II) is collected as a measurement sample and placed in a crucible, and nitrogen is used as a flow in the heating furnace. (1) In a nitrogen atmosphere, the temperature of the heating furnace is heated from room temperature to 105°C at a heating rate of 10°C / min, then (2) the temperature is held at 105°C until the measured weight is equilibrated, (3) the temperature is raised from 105°C to 450°C at a heating rate of 10°C / min, (4) the temperature is held at 450°C until the measured weight is equilibrated, (5) the heating furnace air flow is changed from nitrogen to air, and the temperature is raised from 450°C to 950°C at a heating rate of 10°C / min, (6) the weight W1 of the combustion residue after holding at 950°C for 10 minutes is determined, and (7) the temperature is cooled to room temperature. The weight W1 of the combustion residue is divided by the weight of the measurement sample placed in the crucible, and the resulting value is multiplied by 100 to obtain the amount of ash in the recovered resin (II). The ash content in the resin particles described below can also be measured in a similar manner. Furthermore, when the resin particles contain an inorganic pigment such as carbon black as a colorant, the content can be determined by the following method. The weight W2 of the combustion residue is determined by subtracting the weight W1 measured after holding for 10 minutes in (6) from the weight measured after equilibrium is reached in (4). Next, the weight W2 of the combustion residue is divided by the weight of the measurement sample placed in the crucible, and the result is multiplied by 100 to determine the content of the inorganic pigment in the resin particles.

[0024] Thermoplastic resins such as nylon, polyester, polyethylene, polypropylene, etc. are mainly used as raw materials for fishing nets, fishing lines, ropes, etc. In the present invention, among them, polyolefin resins such as polyethylene, polypropylene, or a mixture of polyethylene and polypropylene are selectively recovered and pelletized, and used as the recovered polyolefin resin (II).

[0025] Examples of the recovered polyolefin resin (II) include polyethylene resins, polypropylene resins, and mixtures of two or more of these. Examples of the polyethylene resins include polymers of ethylene monomers, such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, and ethylene-vinyl acetate copolymers, and copolymers of ethylene and comonomers with an ethylene content of more than 50 mol%, and mixtures of two or more of these. Examples of the polypropylene resins include polymers of propylene monomers, propylene-ethylene copolymers, propylene-butene copolymers, propylene-ethylene-butene copolymers, and mixtures of two or more of these.

[0026] Among these polyolefin resins, high density polyethylene, propylene homopolymer, and a mixture of high density polyethylene and propylene homopolymer are preferred because they have excellent melt mixability with the propylene random copolymer (I). Furthermore, the recovered polyolefin resin (II) is more preferably made of high density polyethylene because the resulting foamed beads have excellent moldability. In this specification, high density polyethylene refers to a polyethylene having a density of 940 kg / m 3 Super 970kg / m 3 This refers to polyethylene less than 100 mm.

[0027] The melting point of the recovered polyolefin resin (II) is 125°C or higher and 170°C or lower. If the melting point is within this range, it can be mixed with a propylene random copolymer (I) having a melting point of 120°C or higher to obtain good expanded beads. Furthermore, when the recovered polyolefin resin (II) contains the high-density polyethylene, the melting point of the high-density polyethylene is preferably 125°C or higher, more preferably 130°C or higher. The melting point of the high-density polyethylene is preferably 145°C or lower, more preferably 140°C or lower. If the melting point of the high-density polyethylene satisfies the above range, the moldability of the obtained expanded beads is excellent, which is preferable.

[0028] When the recovered polyolefin resin (II) contains a high-density polyethylene resin, the resulting expanded beads have excellent moldability, and therefore the content thereof is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, 80% by mass or more, and particularly preferably 90% by mass or more.

[0029] The flexural modulus of the recovered polyolefin resin (II) is preferably 500 MPa or more, more preferably 600 MPa or more, in order to maintain the rigidity of the resin and provide a molded article with excellent recovery from shrinkage after molding.The flexural modulus of the recovered polyolefin resin (II) is preferably 1400 MPa or less, more preferably 1300 MPa or less, in order to provide a molded article with excellent flexibility.

[0030] In the melt mixing step (A), the blending ratio of the random copolymer (I) is 40% by mass or more and 95% by mass or less, and the blending ratio of the recovered polyolefin-based resin (II) is 5% by mass or more and 60% by mass or less (however, the total blending ratio of the propylene-based random copolymer (I) and the recovered polyolefin-based resin (II) is 100% by mass). If the blending ratio of the recovered polyolefin resin (II) is too low, the purpose of reusing fishery waste (effective use of resources and reduction of carbon dioxide) may not be achieved. On the other hand, if the blending ratio of the recovered polyolefin resin (II) is too high, the production stability may decrease, such as strand breakage occurring easily when the molten mixed resin is extruded from the extruder in the resin particle production step (B), making it difficult to stably obtain resin particles, or in the expansion step (C), expanding particles having the desired density may not be obtained.

[0031] From this viewpoint, the blending ratio of the random copolymer (I) is preferably 50% by mass or more and 90% by mass or less, and the blending ratio of the recovered polyolefin resin (II) is preferably 10% by mass or more and 50% by mass or less. The blending ratio of the random copolymer (I) is more preferably 60% by mass or more and 85% by mass or less, and the blending ratio of the recovered polyolefin resin (II) is more preferably 15% by mass or more and 40% by mass or less. The blending ratio of the random copolymer (I) is more preferably 70% by mass or more and 80% by mass or less, and the blending ratio of the recovered polyolefin resin (II) is more preferably 20% by mass or more and 30% by mass or less. However, in any case, the total blending ratio of the propylene random copolymer (I) and the recovered polyolefin resin (II) is 100% by mass.

[0032] The melt flow rate (hereinafter also referred to as MFR) of the propylene random copolymer (I) at 230°C under a load of 2.16 kg is preferably 1 g / 10 min or more and 10 g / 10 min or less. If the MFR is within this range, the expandability and moldability of the resulting expanded beads are improved, and a good expanded bead molding can be obtained. From the above viewpoint, the melt flow rate of the random copolymer (I) is more preferably 2 g / 10 min or more, and even more preferably 3 g / 10 min or more. Moreover, the melt flow rate of the random copolymer (I) is more preferably 8 g / 10 min or less, and even more preferably 7 g / 10 min or less.

[0033] Furthermore, it is preferable that the melt flow rate of the recovered polyolefin resin (II) at 230° C. under a load of 2.16 kg is smaller than the melt flow rate of the propylene random copolymer (I). If the MFR of the recovered polyolefin resin (II) is smaller than that of the propylene random copolymer (I), the expandability and moldability of the resulting expanded beads are improved, and a good expanded bead molding can be obtained. The fact that the recovered polyolefin resin (II) has a small MFR means that the resin constituting the recovered polyolefin resin (II) is not excessively deteriorated. In order to maintain a small MFR of the recovered polyolefin resin (II), it is preferable to produce the recovered polyolefin resin (II) without applying excessive heat or shear when the recovered fishery material is heated and melted and pelletized to obtain the recovered polyolefin resin (II). The recovered polyolefin resin (II) preferably has an MFR of 5 g / 10 min or less at 230° C. and a load of 2.16 kg, and more preferably has an MFR of 3 g / 10 min or less.

[0034] In this specification, the melt flow rate is a value measured under conditions of a temperature of 230° C. and a load of 2.16 kg based on JIS K7210-1:2014.

[0035] The resin particles constituting the expanded beads of the present invention may contain other resin components other than the propylene-based random copolymer (I) and the recovered polyolefin-based resin (II) within the range that does not impair the effects of the present invention. Examples of other resin components include styrene-based resins such as polystyrene and styrene-maleic anhydride copolymers; rubbers such as ethylene-propylene-based rubbers (having a melting point of less than 120°C), ethylene-1-butene rubber, propylene-1-butene rubber, ethylene-propylene-diene-based rubbers, isoprene rubber, neoprene rubber, and nitrile rubber; and thermoplastic elastomers such as styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated styrene-butadiene-styrene block copolymers, and hydrogenated styrene-isoprene-styrene block copolymers. These resins, rubbers, or elastomers may be used in combination of two or more kinds. When the other resin components are contained, the total content of the other resin components is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less, based on 100% by mass of the total of the copolymer (I) and the recovered resin (II) (including the total of the other resin components).

[0036] In the melt mixing step (A), additives may be added, if necessary, together with the propylene random copolymer (I) and the recovered polyolefin resin (II), such as cell regulators, colorants, flame retardants, lubricants, antioxidants, weathering agents, dispersion size expanders, etc.

[0037] Examples of the bubble regulator include talc, silica, calcium carbonate, borax, zinc borate, aluminum hydroxide, alum, fatty acid monoamide, fatty acid bisamide, polyethylene wax, methylene bis stearic acid, zinc borate, alum, polytetrafluoroethylene, etc. The amount of the bubble regulator added is preferably 0.001 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, per 100 parts by mass of the total of the copolymer (I) and the recovered resin (II). When the bubble regulator is added, the bubble regulator can be blended as it is, but it is usually preferable to add it as a master batch of the bubble regulator in consideration of dispersibility, etc.

[0038] Many of the recovered fisheries materials, such as fishing nets, fishing lines, and fishing ropes, are colored green or the like. In such cases, the resin foam beads containing the recovered polyolefin resin (II) obtained by pelletizing the recovered fisheries materials, and further the finally obtained foamed bead moldings, will have the color derived from the recovered fisheries materials.

[0039] In the resin foamed beads containing the recovered polyolefin resin (II) and the finally obtained foamed bead molding, a colorant can be used for the purpose of making the appearance for marine products beautiful. As the colorant, either a pigment or a dye can be used, and it is preferable to use carbon black such as furnace black, channel black, thermal black, acetylene black, and ketjen black, or carbon-based pigments such as graphite and carbon fiber, and carbon black is more preferable.

[0040] The amount of colorant added to the expanded beads is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, from the viewpoint of making the appearance beautiful. The amount of colorant added to the expanded beads is preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of maintaining the moldability of the expanded bead molding.

[0041] In the melt mixing step (A), when forming the molten mixed resin, additives such as a cell regulator and a colorant can be directly fed to an extruder and kneaded therein. However, it is preferable to prepare a master batch of the additives and feed the master batch, the copolymer (I), and the recovered resin (II) to an extruder and melt knead them.

[0042] The resin particle forming step (B) is melt This is a step of obtaining resin particles from the melt-mixed resin, and is a step subsequent to the melt-mixing step (A). Usually, the melt-mixing step (A) and the resin particle formation step (B) are carried out continuously using the same extruder. That is, the propylene random copolymer (I) and the recovered polyolefin resin (II) are heated, melted, and kneaded in an extruder to form a molten mixed resin (melt mixing step (A)). The molten mixed resin is then extruded in a strand shape through a die attached to the outlet of the extruder, cooled by passing through water, and then cut to an appropriate length to produce resin particles (resin particle formation step (B)). Incidentally, resin particles can also be produced by a method in which the strands are cut into pieces of an appropriate length and weight, and then cooled, or simultaneously with cutting.

[0043] In cutting the strand, it is preferable to cut the resin particles so that their weight is 0.5 to 10 mg, more preferably 1 to 5 mg. If the weight is within this range, it is preferable because uniform filling of the expanded particles into the mold can be ensured during molding in the mold.

[0044] The amount of ash contained in the resin particles is preferably 1% by mass or less, more preferably 0.5% by mass or less, and even more preferably 0.4% by mass or less. The resin particles may contain inorganic components derived from a foam regulator, etc., but the amount of the inorganic components contained in the resin particles is extremely small, so it does not have a significant effect on the measurement of the ash content. The amount of ash contained in the resin particles can be measured by the above-mentioned method.

[0045] In the expansion step (C), the resin particles obtained in the resin particle formation step (B) are expanded to produce expanded resin particles. For example, the resin particles can be used to produce expanded particles by carrying out a so-called dispersion medium release foaming method. In the dispersion medium release foaming method, the resin particles are dispersed in a dispersion medium such as water in a sealed container such as an autoclave together with a physical foaming agent, the dispersion medium is heated to a temperature equal to or higher than the softening temperature of the resin particles, the foaming agent is impregnated into the resin particles, and then, while maintaining the pressure in the sealed container at a pressure equal to or higher than the vapor pressure of the foaming agent, one end of the sealed container below the water surface is opened, and the expandable resin particles containing the foaming agent are released from the sealed container together with the dispersion medium such as water under an atmosphere of a lower pressure than the pressure in the sealed container, usually atmospheric pressure, to be foamed, thereby obtaining expanded particles. Alternatively, the expandable resin particles containing a physical foaming agent may be taken out of the sealed container and heated with a heating medium such as steam to be foamed.

[0046] When releasing from a high pressure where foaming does not occur to a low pressure where foaming occurs, the pressure difference between the high pressure and the low pressure is preferably 400 kPa or more, more preferably 500 to 15,000 kPa.

[0047] The blowing agent used in the dispersion medium release foaming method usually includes organic physical blowing agents such as propane, isobutane, normal butane, isopentane, normal pentane, cyclopentane, normal hexane, cyclobutane, cyclohexane, chlorofluoromethane, trifluoromethane, 1,1,1,2-tetrafluoroethane, 1-chloro-1,1-difluoroethane, 1,1-difluoroethane, and 1-chloro-1,2,2,2-tetrafluoroethane, and inorganic physical blowing agents such as nitrogen, carbon dioxide, argon, and air. Among these, inorganic physical blowing agents that do not destroy the ozone layer and are inexpensive are preferred, and carbon dioxide is particularly preferred. In addition, two or more of these blowing agents can be used in combination.

[0048] The amount of the blowing agent used is appropriately determined depending on the relationship between the bulk density of the expanded beads to be obtained and the expansion temperature. Specifically, in the case of the above blowing agents other than nitrogen and air, the amount of the blowing agent used is usually 2 to 50 parts by weight per 100 parts by weight of resin beads. In the case of nitrogen and air, an amount is used that ensures that the pressure in the closed container is within the pressure range of 1 to 7 MPa (G). Note that MPa (G) means gauge pressure.

[0049] The dispersion medium for dispersing the resin particles in the closed container is preferably water, but any medium that does not dissolve the resin particles can be used, and examples of such dispersion medium include ethylene glycol, glycerin, methanol, ethanol, etc., but water is usually used.

[0050] In the closed container, when the base resin particles are dispersed in a dispersion medium and heated to a foaming temperature, a fusion inhibitor can be used to prevent the resin particles from fusing together. As the fusion inhibitor, any fusion inhibitor can be used, whether inorganic or organic, as long as it is insoluble in water or the like and does not melt when heated, but inorganic ones are generally preferred.

[0051] As inorganic anti-fusing agents, powders such as kaolin, talc, mica, aluminum oxide, titanium oxide, and aluminum hydroxide are suitable. The anti-fusing agents preferably have an average particle size of 0.001 to 100 μm, particularly 0.001 to 30 μm. The amount of anti-fusing agent added is usually preferably 0.01 to 10 parts by mass per 100 parts by mass of resin particles.

[0052] In addition, anionic surfactants such as sodium dodecylbenzenesulfonate and sodium oleate, and aluminum sulfate are preferably used as dispersion aids. The dispersion aid is preferably added in an amount of 0.001 to 5 parts by mass per 100 parts by mass of resin particles.

[0053] In the case of producing expanded beads having a low bulk density, it is preferable to produce expanded beads by the above-mentioned dispersion medium release foaming method or the like, and then further expand the expanded beads obtained, thereby performing so-called two-stage expansion. According to the two-stage expansion, the expanded beads are filled into a pressurizable sealed container, and the expanded beads are pressurized with a gas such as air to increase the internal pressure of the expanded beads to 0.01 to 0.6 MPa (G), and then the expanded beads are taken out of the container and heated with a heating medium such as steam, thereby easily obtaining expanded beads having a low bulk density.

[0054] In the expansion step (C), the resin particles are expanded to a bulk density of 10 kg / m 3 It is preferable to obtain resin foamed beads having a bulk density of 15 kg / m or more. If the bulk density is satisfied, the mechanical strength of the finally obtained foamed bead molding will be excellent, which is preferable. From the above viewpoint, the bulk density of the foamed beads is 15 kg / m or less. 3 More preferably, it is 20 kg / m or more. 3 More preferably, it is 25 kg / m or more. 3 On the other hand, from the viewpoint of obtaining an excellent cushioning property and light weight of the expanded bead molding, it is particularly preferable that the bulk density is 100 kg / m or more. 3 It is preferable to obtain resin foam particles having a density of 70 kg / m 3 More preferably, it is 50 kg / m or less. 3 More preferably, it is 40 kg / m or less. 3 It is particularly preferred that:

[0055] In this specification, the bulk density is measured as follows: Bulk density of expanded beads (kg / m 3 ) is measured by preparing a 1L measuring cylinder, filling the empty measuring cylinder with foam particles up to the 1L mark, measuring the weight (g) of the foam particles per 1L, and dividing the weight of the foam particles by the volume [kg / m 3 ] is calculated by converting the units.

[0056] In the expansion step (C), the average cell diameter of the expanded beads is preferably 30 μm or more, more preferably 40 μm or more, even more preferably 45 μm or more, and particularly preferably 50 μm or more. On the other hand, the average cell diameter of the expanded beads is preferably 300 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 120 μm or less. When the average cell diameter is within the above range, the moldability in the mold is excellent, and the obtained expanded bead molding is excellent in dimensional recovery after molding and is also excellent in mechanical properties such as compression properties.

[0057] In this specification, the average bubble diameter of an expanded bead can be determined as follows based on an enlarged photograph of a cut surface of an expanded bead approximately in half taken with a microscope. First, in the enlarged photograph of the cut surface of the expanded bead, four line segments are drawn from one surface of the expanded bead to the other surface, passing through approximately the center of the cut surface of the bubbles. However, the line segments are drawn so as to form radial straight lines extending in eight directions at equal intervals from the approximately center of the cut surface of the bubbles to the cut particle surface. Next, the total number N (pieces) of bubbles intersecting with the four line segments is determined. The sum L (μm) of the lengths of the four line segments is determined, and the value (L / N) obtained by dividing the sum L by the sum N is defined as the average bubble diameter of one expanded bead. This operation is performed for 10 or more expanded beads, and the arithmetic mean of the average bubble diameters of each expanded bead is defined as the average bubble diameter of the expanded beads.

[0058] The bulk density of the expanded beads obtained is adjusted by the amount of foaming agent added, the foaming temperature, and the pressure difference during foaming. In general, within the appropriate range, the larger the amount of foaming agent added, the higher the foaming temperature, and the larger the pressure difference, the smaller the bulk density of the expanded beads obtained. The average cell diameter of the expanded beads is adjusted by the type and amount of foaming agent, the foaming temperature, and the amount of foam regulator added.

[0059] In the present invention, it is preferable that the expanded beads obtained in the expansion step (C) are measured by heat flux differential scanning calorimetry for a melting peak specific to the resin and a melting peak on the higher temperature side resulting from secondary crystallization of the resin formed by the thermal history until the resin particles are expanded to obtain the expanded beads. That is, according to the heat flux differential scanning calorimetry method of JIS K7121-1987, a test piece of 1 to 3 mg of expanded beads is heated and melted at a heating rate of 10°C / min from 30°C to a heating end temperature 30°C higher than the end of the melting peak, and the first DSC curve measured has two or more melting peaks, and the two or more melting peaks include a melting peak inherent to the resin constituting the expanded beads (hereinafter also simply referred to as an "intrinsic peak") and a high-temperature melting peak (hereinafter also simply referred to as a "high-temperature peak") which is due to secondary crystallization of the resin formed by the thermal history until the resin particles are expanded to obtain the expanded beads and has a peak temperature higher than the peak temperature of the inherent melting peak, and the expanded beads are then kept at the heating end temperature for 10 minutes, cooled to 30°C at a cooling rate of 10°C / min, and heated and melted again at a heating rate of 10°C / min to a temperature 30°C higher than the end of the melting peak, and the second DSC curve measured does not show the high-temperature melting peak. If the expanded bead is larger than 3 mg, it is divided into equal portions each having a size of 1 to 3 mg and used as a test piece.

[0060] The appearance of a high-temperature peak in the first DSC curve indicates that the expanded beads have excellent moldability in a mold, and the mechanical properties such as compressive strength and tensile strength of the resulting expanded bead molding are improved.

[0061] The calorific value of the high-temperature peak (high-temperature peak calorific value) is preferably 10 J / g or more, more preferably 15 J / g or more, and even more preferably 20 J / g or more. On the other hand, the calorific value of the high-temperature peak is preferably 35 J / g or less, more preferably 30 J / g or less, and even more preferably 25 J / g or less. When the heat of fusion of the high-temperature peak is within this range, the expanded beads are more excellent in moldability. In addition, the mechanical strength of the resulting expanded bead molding is further improved.

[0062] The calorific value of the high-temperature peak is measured by a method based on JIS K7122-1987 as follows. First, 1 to 3 mg of expanded beads are sampled, and the temperature is raised at 10°C / min from 23°C to a heating end temperature 30°C higher than the end of the melting peak using a heat flux differential scanning calorimeter. Figure 1 shows an example of a first DSC curve obtained by heat flux differential scanning calorimetry for the expanded beads of the present invention. In Fig. 1, a represents the characteristic peak that appears on the low-temperature side, b represents the high-temperature peak, and T E is the end temperature of melting, and indicates the temperature at which the high temperature side of endothermic peak b returns to the baseline position.

[0063] The heat of fusion of the high-temperature peak in the first DSC curve is calculated as follows. As shown in Figure 1, the heat of fusion of the foamed beads is calculated by dividing the 80°C point α on the DSC curve by the melting end temperature T EA straight line is drawn connecting point β on the DSC curve showing the characteristic peak a and point β, and the bottom of the valley between the characteristic peak a and the high-temperature peak b is designated as point γ. A straight line is drawn from point γ parallel to the vertical axis of the figure, and the point where the line intersects with the line connecting point α and point β is designated as point δ. The heat of fusion of the high-temperature peak is the heat amount corresponding to the region surrounded by the line connecting point δ and point γ, the DSC curve from point γ to point β, and the line connecting point β to point δ. Note that, although this high-temperature peak b is recognized in the first DSC curve measured as described above, it is not recognized in the second DSC curve obtained by holding the sample for 10 minutes at a heating end temperature 30°C higher than the end of the melting peak after obtaining the first DSC curve, lowering the temperature to 30°C at 10°C / min, and then raising the temperature again to a heating end temperature 30°C higher than the end of the melting peak at 10°C / min, and only the characteristic peak a of the resin constituting the expanded beads is recognized. For example, when the melting point difference between the propylene random copolymer (I) and the recovered polyolefin resin (II) is large, three or more endothermic peaks appear in the first DSC curve. In this case, no high-temperature peak is observed in the second DSC curve. By utilizing this, it is possible to distinguish which peak is the high-temperature peak by comparing the first and second DSC curves.

[0064] Next, the multi-layer expanded beads in which the above-mentioned expanded beads are coated with a polyolefin-based resin coating layer will be described. In the present invention, it is preferred that the resin foamed beads constitute an expanded resin core layer (hereinafter simply referred to as the expanded bead core layer), and that the expanded bead core layer is coated with a polyolefin-based resin coating layer (hereinafter simply referred to as the coating layer), so that the expanded bead is a multi-layered expanded bead consisting of the expanded bead core layer and the coating layer as a whole.

[0065] In the multi-layered expanded beads, the expanded bead core layer has the same structure as the expanded beads obtained in the expansion step (C) described above. Furthermore, since the multi-layered expanded beads are expanded beads having excellent expandability and moldability in a mold, the finally obtained expanded bead molding is likely to have better fusion between the composite expanded beads.

[0066] The coating layer may be in a foamed or non-foamed state, but in order to obtain an expanded bead molding having excellent mechanical strength, it is preferable that the resin layer is substantially non-foamed. Note that, as used herein, "substantially non-foamed" does not only mean that no bubbles are present (including bubbles that were formed during the expansion of the resin beads and melted and destroyed, resulting in the disappearance of the bubbles), but also means that there are a small number of very small bubbles present within a range that does not affect the mechanical strength of the expanded bead molding obtained.

[0067] In the multilayer expanded beads, the expanded core layer may be completely covered with the expanded coating layer, or a part of the expanded core layer may be exposed. An example of a structure in which the expanded core layer is exposed is a structure in which only the side surface of a cylindrical expanded core layer is covered with the expanded coating layer, and the expanded core layer is exposed on the top and bottom surfaces of the cylinder.

[0068] Examples of the polyolefin resin (III) constituting the coating layer include polypropylene resins, polyethylene resins, polybutene resins, and mixtures thereof.

[0069] The polypropylene resin refers to a resin in which the propylene component unit is 50% by mass or more, and examples thereof include a propylene homopolymer, a copolymer with other olefins copolymerizable with propylene, and the like. Examples of other olefins copolymerizable with propylene include α-olefins having 4 or more carbon atoms, such as ethylene and 1-butene. The copolymer may be a random copolymer or a block copolymer, and may be not only a binary copolymer but also a ternary copolymer. These polypropylene resins may be used alone or in a mixture of two or more kinds. Examples of the copolymer include a propylene-ethylene random copolymer, a propylene-ethylene block copolymer, a propylene-ethylene-butene random copolymer, and a mixed resin of two or more kinds thereof.

[0070] The polyethylene resin refers to a resin in which the ethylene component unit is 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more in the resin, and preferably used is a homopolymer of ethylene or a copolymer of ethylene and an α-olefin having 4 to 6 carbon atoms. Examples of the polyethylene resin include high-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, very low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene-acrylic acid alkyl ester copolymer, ethylene-methacrylic acid copolymer, ethylene-methacrylic acid alkyl ester copolymer, and further mixed resins of two or more of these.

[0071] When the polyolefin resin (III) constituting the coating layer is a polypropylene resin, the polypropylene resin preferably has the same resin composition as the propylene random copolymer (I) constituting the expanded particle core layer. When the polyolefin resin (III) constituting the coating layer has the same resin composition as the propylene random copolymer (I) constituting the expanded particle core layer, the adhesion between the expanded particle core layer and the coating layer can be improved.

[0072] The polyolefin resin (III) constituting the coating layer may contain the above-mentioned recycled polyolefin resin (II). The amount of the recycled polyolefin resin (II) in the polyolefin resin constituting the coating layer is preferably less than the amount of the recycled polyolefin resin (II) in the resin constituting the core layer. From the viewpoint of improving the manufacturing stability of the expanded beads and improving the thermal fusion property between the expanded beads, it is preferable that the polyolefin resin (III) does not contain the recycled polyolefin resin (II).

[0073] In addition, by forming the coating layer using a polyolefin resin having a melting point lower than that of the copolymer (I), the molding vapor pressure during in-mold molding can be reduced. That is, in the case of multi-layer expanded beads having a coating layer with a low melting point, when the expanded bead core layer is heated to a temperature at which secondary expansion can be performed and molded in a mold, the coating layer softens faster than the expanded bead core layer, improving the thermal fusion between the expanded beads.

[0074] The melting point of the polyolefin resin constituting the coating layer is preferably 0°C or more and 30°C or less lower than the melting point of the propylene random copolymer (I) constituting the expanded particle core layer, more preferably 5°C or more and 25°C or less lower, and even more preferably 10°C or more and 20°C or less lower.

[0075] Additives such as colorants, flame retardants, lubricants, antioxidants, weather resistance agents, etc. may be added to the coating layer, and it is particularly preferable to add carbon black as a colorant. These additives are blended by, for example, blending them with the polyolefin resin forming the coating layer when forming the molten resin for forming the coating layer described below.

[0076] The mass ratio of the expanded bead core layer to the coating layer is preferably 99.5:0.5 to 65:35, more preferably 99:1 to 70:30, further preferably 97:3 to 75:25, and particularly preferably 97:3 to 80:20. If the mass ratio of the coating layer is within the above range, the effect of improving the fusibility is easily obtained, which is preferable.

[0077] The multi-layer expanded particles can be obtained by forming a molten mixed resin in the melt mixing step (A) by the above-mentioned method, coating the obtained molten mixed resin with a molten resin for forming a coating layer in the resin particle production step (B) to produce multi-layer resin particles, and expanding the multi-layer resin particles in the expansion step (C) by the above-mentioned method.

[0078] The resin particles are preferably multi-layered resin particles having a core layer having a mixture of the propylene random copolymer (I) and the recycled polyolefin resin (II) as a base resin, and a coating layer having a polyolefin resin (III) as a base resin that coats the core layer.

[0079] The multi-layered resin particles can be produced, for example, as follows. An apparatus in which two extruders, an extruder for a resin particle core layer and an extruder for a resin particle coating layer, are connected to a co-extrusion die is used, and the required propylene-based random copolymer (I), the recovered polyolefin-based resin (II), and additives such as a bubble regulator and a colorant as required are supplied to the extruder for the resin particle core layer and melt-kneaded to form a molten resin for forming the resin particle core layer, and the required polyolefin-based resin and colorant as required are supplied to the extruder for the coating layer and melt-kneaded to form a molten resin for forming the coating layer, and the molten resin for forming the resin particle core layer is co-extruded. Multilayer resin particles can be produced by introducing the molten resin for forming the coating layer into a die to form a linear flow, simultaneously introducing the molten resin for forming the coating layer into the co-extrusion die, laminating the molten resin for forming the coating layer so as to surround the linear flow of the molten resin for forming the resin particle core layer to form a molten resin with a sheath-core structure, extruding the molten resin in the form of one or more strands from small holes in a die attached to the outlet of the extruder, cooling the strands by passing them through water and then cutting them to an appropriate length, or cutting and cooling the molten resin composition while extruding it from the die into water, etc. In this specification, the composite structure formed in this manner is sometimes referred to as a "sheath-core" structure.

[0080] The method for producing multilayer resin particles using the above-mentioned coextrusion die is described in detail in, for example, JP-B-41-16125, JP-B-43-23858, JP-B-44-29522, and JP-A-60-185816.

[0081] In producing the coating layer that constitutes the multilayer resin particles, additives such as colorants can be directly supplied to an extruder for the coating layer together with the polyolefin-based resin that constitutes the coating layer and kneaded therein. However, it is preferable to prepare a master batch in advance and supply the master batch and the polyolefin-based resin to an extruder for forming the coating layer and knead them therein.

[0082] As for the weight of the multilayer resin particles, in order to ensure uniform filling of the expanded beads in a mold, similarly to the production of the resin particles, it is preferable to cut the strands so that the weight is 0.02 to 20 mg, and more preferably 0.1 to 6 mg.

[0083] Next, an expanded bead molding obtained by in-mold molding using the expanded resin beads obtained according to the present invention will be described. By performing in-mold molding using the resin foamed beads obtained by the present invention, an expanded bead molded body (hereinafter, also simply referred to as a molded body) can be obtained. The in-mold molding method is a conventionally known method, and the expanded beads are filled into a mold and heated and molded using a heating medium such as steam to obtain an expanded bead molded body. Specifically, after the expanded beads are filled into a mold, steam is introduced into the mold to heat and expand the expanded beads, which are then fused together to obtain a molded body having the shape of the molded space. In addition, if necessary, a pressure treatment operation for increasing the pressure inside the expanded beads can be performed in the same manner as in the above-mentioned two-stage expansion to adjust the internal pressure of the expanded beads to 0.01 to 0.2 MPa (G).

[0084] After the foamed beads are heat-fused and molded, the molded body obtained can be cooled in the mold by a water-cooling method, or by a vacuum method using the heat of vaporization of steam.

[0085] The expanded bead molding finally obtained by the method of the present invention contains a polyolefin resin obtained from fishery waste such as fishing nets, fishing lines, and ropes, and enables the effective reuse of fishery waste. EXAMPLES

[0086] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples.

[0087] The types and physical properties of the propylene random copolymers (I) used in the examples and comparative examples are shown in Table 1-1, and the types and physical properties of the recovered polyolefin resins (II) are shown in Table 1-2.

[0088] [Table 1-1]

[0089] [Table 1-2]

[0090] In Table 1-2, Recovered Resin 1 and Recovered Resin 3 are mixed resins of propylene homopolymer, the main component of which is propylene homopolymer, and high-density polyethylene.

[0091] The melting points and melt flow rates in Table 1 were measured by the following methods. The melting point of the resin was measured by heat flux DSC measurement using 2 mg of randomly selected expanded particles as a sample, using a heat flux differential scanning calorimeter (DSC7020) manufactured by SII Nano Technology Co., Ltd., according to the method described in JIS K7121 (1987) "Measuring the melting temperature after a certain heat treatment". The measurement was performed by heating from 30 to 200 °C at a heating rate of 10 °C / min, cooling to 30 °C at a cooling rate of 10 °C / min, and then heating again from 30 to 200 °C at a heating rate of 10 °C / min. The apex temperature of the endothermic peak determined by the DSC curve obtained when the sample was heated from 30 to 200 °C at a heating rate of 10 °C / min was taken as the melting point of the resin.

[0092] The melt flow rate of the resin was measured under conditions of a temperature of 230°C and a load of 2.16 kg in accordance with JIS K7210-1:2014.

[0093] The flexural modulus in Table 1 was measured by the following method. The flexural modulus was measured in accordance with JIS K7171-2:2016. Each of the raw materials in Table 1 was used to prepare a 4 mm thick press sheet by the following method. Specifically, a 4 mm thick mold was placed on a heat press heated to 200 ° C., the raw materials were placed in the mold and melted, and then pressed at a pressure of 15 MPa for 5 minutes. The mold was then moved to a heat press at 200 ° C. and pressed at a pressure of 15 MPa until the temperature reached room temperature to produce a sheet. A test piece measuring 80 mm in length and 10 mm in width was prepared from the obtained sheet, and after conditioning for 24 hours under standard conditions, it was tested using a Shimadzu Autograph AGS-X universal testing machine at a test speed of 2 mm / min to determine the flexural modulus.

[0094] The melting point of the raw resin was measured by heat flux differential scanning calorimetry based on JIS K7121-1987. Under the condition of a nitrogen inflow rate of 30 mL / min, the resin was heated and melted from 30°C to a temperature 30°C higher than the end of the melting peak at a heating rate of 10°C / min (first heating), then held at that temperature for 10 minutes, cooled to 30°C at a cooling rate of 10°C / min, and heated and melted again at a heating rate of 10°C / min to a temperature 30°C higher than the end of the melting peak. The melting point was determined as the peak apex temperature of the melting peak of the DSC curve obtained by heating and melting the resin at a DSC curve obtained by heating and melting the resin at a heating rate of 10°C / min to a temperature 30°C higher than the end of the melting peak. When there are two or more melting peaks, the apex temperature of the endothermic curve peak with the largest peak intensity was taken as the original melting point. A high-sensitivity differential scanning calorimeter "EXSTAR DSC7020" (manufactured by SII Nano Technology Co., Ltd.) was used as the measuring device. The heat of fusion of the raw resin was measured based on JIS K7122-1987 and was calculated as the total heat of fusion of the melting peak of the second DSC curve obtained by measuring the melting point of the raw resin.

[0095] The foam regulator used was "Zinc Borate 2335" manufactured by Tomita Pharmaceutical Co., Ltd.

[0096] Examples 1 to 7, Comparative Examples 1 to 3 [Step A] [Step B]: Manufacturing of resin particles Using a device equipped with a die for strand formation at the outlet side of the resin particle forming extruder, the type and amount of propylene-based random copolymer (I) shown in Table 2, the type and amount of recovered polyolefin-based resin (II) shown in Table 2, and the type and amount of additives shown in Table 2 were fed to the resin particle forming extruder, heated, melted, and kneaded at a set temperature of 200 to 220 ° C., fed to the die, and extruded as a number of strands from the holes in the die, cooled with water, and cut into 1.2 mg and L / D = 2.9 with a pelletizer to obtain cylindrical resin particles. The weight and L / D of the resin particles are arithmetic average values ​​calculated from 100 resin particles randomly extracted from the resin particle group.

[0097] [Table 2]

[0098] [Step C]: Production of foamed beads 20 kg of the above-mentioned fat particles were charged into a 100 L autoclave together with 60 L of water as a dispersion medium, 15 g of kaolin as a dispersant, 12 g of sodium alkylbenzene sulfonate as a dispersion aid, and 3 g of aluminum sulfate were added to the dispersion medium, and carbon dioxide as a foaming agent was pressurized into the autoclave to the foaming pressure shown in Table 3. The mixture was heated to the foaming temperature shown in Table 3 with stirring and maintained at the same temperature for 15 minutes to adjust the high-temperature peak heat quantity, after which the contents of the autoclave were released together with water under atmospheric pressure. Departure Foam particles were obtained.

[0099] [Table 3]

[0100] [Production of foamed bead moldings] The foamed beads obtained above were left to stand in the net layer for 12 hours for curing, and then used for molding. The foamed beads were filled into a pressurized filling hopper and pressurized with compressed air, and then a flat mold measuring 400 mm long x 300 mm wide x 80 mm thick was pressurized at a pressure 0.05 MPa (G) lower than that of the filling hopper. The partition of the pipe connecting the filling hopper and the mold was opened, and the foamed beads were filled into the cavity of the flat mold together with compressed air, and molding was performed in the mold by steam heating to obtain a plate-shaped foamed bead molded body. The pressure of the filling hopper was determined by changing the pressure and performing molding several times to find the pressure at which a molded body of the desired density was obtained. The heating method was as follows: with the drain valves of both sides of the mold open, steam was supplied for 2 seconds to perform preheating (exhaust process), and then one-way heating was performed at a pressure 0.1 MPa (G) lower than the main heating pressure, and one-way heating was performed from the opposite direction at the same pressure, and then heating was performed at the molding heating steam pressure (molding pressure) shown in Table 3. The molding pressure was set at a pressure at which the molded body did not shrink significantly and showed a fusion rate of 80% or more. After heating, the pressure was released and water-cooled for 20 seconds, and then vacuum-cooled until the surface pressure due to the foaming force of the molded body reached 0.05 MPa (G), after which the mold was opened and the molded body was removed from the mold. The obtained molded body was cured in an oven at 80°C for 12 hours to obtain an expanded bead molded body. The physical properties of the obtained molded body are shown in Table 4.

[0101] [Table 4]

[0102] Examples 8 to 11 [Step A] [Step B]: Production of multilayer resin particles An extrusion device having a die for forming a multilayer strand attached to the outlet side of a multilayer extruder consisting of an extruder for forming a resin particle and an extruder for forming a resin particle coating layer was used, and the type and amount of propylene-based random copolymer (I) shown in Table 5, the type and amount of recovered polyolefin-based resin (II) shown in Table 5, and the type and amount of additives shown in Table 2 were fed to the extruder for forming a resin particle, and at the same time, the resin for forming a coating layer shown in Table 5 (the total of the resin for forming the core layer and the resin for forming the coating layer is 100 mass%) and the resin for forming the coating layer shown in Table 5 were fed to the extruder for forming a resin particle. The types and amounts of additives shown in were fed to the extruder for coating layer, each of which was heated to a set temperature of 200 to 220°C, melted, and kneaded, and then fed to the die, where they merged in the die and were co-extruded from the fine holes in the die attached to the tip of the extruder as a multi-layer strand in which the resin for forming expanded beads was coated on the side with the coating layer, and the co-extruded strand was cooled with water and cut into 1.2 mg pieces with L / D = 2.9 using a pelletizer to obtain cylindrical composite resin particles formed into two layers (sheath-core structure). The weight and L / D of the composite resin particles are the arithmetic average values ​​calculated from 100 composite resin particles randomly sampled from the group of composite resin particles.

[0103] [Table 5]

[0104] [Step C]: Production of multi-layer foam particles The multi-layer expanded beads were produced in the same manner as in the production of the single-layer expanded beads. The expansion temperature and expansion pressure are shown in Table 6.

[0105] [Table 6]

[0106] The production of an expanded bead molding by in-mold molding of the multi-layered expanded beads was carried out in the same manner as in the in-mold molding using the single-layered expanded beads described above, to obtain an expanded bead molding. The evaluation of moldability and the physical properties of the obtained foamed bead moldings are shown in Table 7.

[0107] [Table 7]

[0108] Examples 1 to 7 and Comparative Examples 1 to 3 are examples in which single-layer expanded beads were produced. Example 2 is an example in which recovered resin 1 having a different ash content from base resin 1 was mixed in the same mass ratio (base resin 1:recovered resin 1=) of 75:25 as in Example 1. The manufacturing stability of the resin particles was excellent, and molding in a mold was possible. Example 3 is an example in which base resin 1 and recovered resin 1 having a different ash content were mixed in a mass ratio (base resin 1:recovered resin 1=) of 50:50. The production stability of the resin particles was excellent, and molding in a mold was possible. Example 4 is an example in which base resin 1 and recovered resin 2 were mixed in a mass ratio (base resin 1:recovered resin 2=) of 85:15. The production stability of the resin particles was excellent, and molding in a mold was good. Example 5 is an example in which base resin 1 and recovered resin 2 having a different ash content were mixed at a mass ratio (base resin 1:recovered resin 2=) of 75:25. The production stability of the resin particles was excellent, and molding in a mold was good. Example 6 is an example in which base resin 1 and recovered resin 3 were mixed in a mass ratio (base resin 1:recovered resin 3=) of 75:25. The production stability of the resin particles was excellent, and molding in a mold was possible. Example 7 is an example in which base resin 1 and recovered resin 1 having a different ash content were mixed at a mass ratio (base resin 1:recovered resin 1=) of 85:15. The production stability of the resin particles was excellent, and molding in a mold was possible.

[0109] Comparative Example 1 is an example in which the amount of base resin 1 and recovered resin 1 was reduced to a mass ratio (base resin 1:recovered resin 1=) of 25:75. Although resin particles could be produced, expandability was poor and expanded particles could not be obtained. Comparative Example 2 is an example in which the base resin 1 and recovered resin 1 having a different ash content were mixed in a mass ratio (base resin 1:recovered resin 1=) of 25:75, with the amount of base resin 1 being reduced, similarly to Comparative Example 1. Although resin particles could be produced, the expandability was poor and expanded particles could not be obtained. Comparative Example 3 is an example in which, except for using recovered resin 1 having a high ash content, the resins were blended in a mass ratio (base resin 1:recovered resin 1=) of 75:25 in the same manner as in Example 1. Although resin particles could be produced and expanded beads could be obtained, the moldability was poor and the range of vapor pressure that could be molded was extremely narrow.

[0110] Examples 8 to 11 are examples in which multi-layered expanded beads were produced. In Example 8, base resin 1 and recovered resin 1 with an ash content of 0.63% by mass were mixed in a mass ratio (base resin 1:recovered resin 1=) of 85:15 to form a coating layer (core layer:coating layer=95% by mass:5% by mass). The manufacturing stability of the resin particles was excellent, and molding in a mold was possible. Example 9 is an example in which base resin 1 and recovered resin 1 with an ash content of 1.24 mass% were mixed in a mass ratio (base resin 1:recovered resin 1=) of 75:25 to form a coating layer (core layer:coating layer=95 mass%:5 mass%), similarly to Example 1. The manufacturing stability of the resin particles was excellent, and molding in a mold was possible. Example 10 is an example in which base resin 1 and recovered resin 2 with an ash content of 1 mass% were mixed in a mass ratio (base resin 1:recovered resin 2=) of 85:15 as in Example 8 to form a coating layer (core layer:coating layer=95 mass%:5 mass%). The production stability of the resin particles was excellent, and the molding in the mold was excellent. In Example 11, base resin 1 and recovered resin 2 with an ash content of 0.88% by mass were mixed in a mass ratio (base resin 1:recovered resin 2=) of 75:25 to form a coating layer (core layer:coating layer=95% by mass:5% by mass). The resin particles had excellent manufacturing stability and excellent molding in a mold.

[0111] The production stability of the resin beads, and the physical properties of the expanded beads and the expanded bead moldings were evaluated as follows.

[0112] [Ash content measurement] The ash content of the recovered polyolefin resin (II) and the resin particles was measured based on JIS K 6226-2. The measuring device used was a thermogravimetric analyzer TGA701 manufactured by LECO. 5 g of the measurement sample was collected and placed in a crucible, and the inside of the heating furnace was made a nitrogen gas flow. (1) In a nitrogen atmosphere, the temperature of the heating furnace was heated from room temperature to 105°C at a heating rate of 10°C / min, then (2) it was held at 105°C until the measured weight was equilibrated, (3) it was heated from 105°C to 450°C at a heating rate of 10°C / min, (4) it was held at 450°C until the measured weight was equilibrated, (5) the heating furnace air flow was changed from nitrogen to air, and it was heated from 450°C to 950°C at a heating rate of 10°C / min, (6) it was held at 950°C for 10 minutes, and then (7) it was cooled to room temperature. The weight W1 of the combustion residue after the 10-minute hold measured in (6) was obtained. Next, the weight W1 of the combustion residue was divided by the weight of the measurement sample placed in the crucible, and the result was multiplied by 100 to obtain the ash content.

[0113] [Production stability of resin particles] (Table 2, Table 5) The production stability of the resin particles was evaluated according to the following criteria. A: The amount of resin discharged during extrusion was stable, and resin particles of uniform size were obtained when confirmed visually. B: The amount of resin discharged during extrusion was unstable, and visual inspection revealed that the resin particles varied in size.

[0114] [Evaluation of moldability] (Table 4, Table 7) Using the above-mentioned molding method, each expanded bead was molded in a mold by changing the molding pressure in increments of 0.02 MPa (G), and the pressure range within which molded bodies that passed all of the evaluations of secondary foamability, fusion property, and recovery property shown below were obtained was evaluated according to the following criteria. Molding pressure range is 0.06MPa(G) or more: A Molding pressure range is 0.04MPa(G):B Molding pressure range is 0.02MPa(G):C Molding pressure range is less than 0.02MPa(G):D

[0115] The secondary foaming property, fusion property and recovery property were evaluated according to the following criteria.

[0116] (Secondary foaming) A 100 mm x 100 mm rectangle was drawn in the center of the expanded bead molding, and then a diagonal was drawn from one corner of the rectangle. The number of voids (gaps between expanded beads) that were formed so as to overlap with the diagonal and were larger than a square with sides of 1 mm were counted, and a number of voids less than 5 was deemed to pass.

[0117] (Fusing ability) The foamed bead molding was folded in the longitudinal direction so as to be approximately equal in size and broken. The exposed fracture surface was visually observed, and the number of foamed beads with peeled-off interfaces between the foamed beads and the number of foamed beads broken internally were counted. The total number of foamed beads exposed on the fracture surface, that is, the ratio of the number of foamed beads broken internally to the total number of foamed beads with peeled-off interfaces between the foamed beads and the number of foamed beads broken internally, was calculated. The value expressed as a percentage (%) was taken as the fusion rate. From the obtained fusion rate value, a fusion rate of 80% or more was considered to pass.

[0118] (Recoverability) The foamed bead moldings were evaluated for the presence or absence of sink marks, i.e., the state in which the center of the molding is more depressed than the surroundings. Specifically, the thicknesses of the center and the four corners of the obtained foamed bead moldings were measured, and the ratio of the thickness of the center to the thickest part of the four corners was calculated. From the obtained thickness ratios, a thickness ratio of 99% or more was considered to pass.

[0119] [Bulk density of expanded particles] (Table 3, Table 6) Approximately 500 cm2 left for 2 days under conditions of 23°C, 50% relative humidity, and 1 atm 3 The weight (g) of the expanded particles was measured, and the expanded particles were placed in an empty 1 L graduated cylinder, and the bottom of the graduated cylinder was lightly tapped on the floor several times to stabilize the filling height of the expanded particles in the cylinder. The volume V [L] of the expanded particles indicated by the graduations on the graduated cylinder was then measured. The weight W [g] of the expanded particles placed in the graduated cylinder was divided by the volume V (W / V) to determine the bulk density of the expanded particles.

[0120] [Average bubble diameter of expanded particles] (Table 3, Table 6) The average cell diameter of the expanded beads was measured by the above-mentioned method (n=10).

[0121] [High-temperature peak heat value of expanded beads] (Table 3, Table 6) Ten expanded beads were randomly sampled from the resulting group of expanded beads, and the high-temperature peak calorific value of each expanded bead was measured by the following method, and the arithmetic mean of these measured values ​​was taken as the high-temperature peak calorific value of the expanded beads. Based on the heat flux differential scanning calorimetry method of JIS K7122-1987, the heat of fusion was calculated from the high-temperature peak of the first DSC curve obtained by heating from 30°C to a temperature 30°C higher than the end of the melting peak at a heating rate of 10°C / min by heat flux differential scanning calorimetry. The measurement device used was a high-sensitivity differential scanning calorimeter "EXSTAR DSC7020" (manufactured by SII NanoTechnology Co., Ltd.). The high-temperature peak heat of the expanded beads corresponds to the area of ​​high-temperature peak b, which appears on the higher temperature side than the intrinsic peak a in the DSC curve shown in Figure 1, and was calculated as follows. First, a straight line was drawn connecting point I, which is 80°C on the DSC curve, and point II, which indicates the end temperature of melting on the DSC curve, as shown in Figure 1. Next, point IV was determined as the intersection point between the line that passes through point III on the DSC curve, which is the valley between the intrinsic peak a and the high-temperature peak b, and the line that connects point I and point II. The area of ​​the portion (shaded portion) surrounded by the straight line connecting points IV and II, the straight line connecting points III and IV, and the DSC curve connecting points III and II was determined as the high-temperature peak heat quantity.

[0122] [Apparent density of foamed bead moldings] (Table 4, Table 7) The weight of the expanded bead molding was measured, and the weight was divided by the apparent volume of the expanded bead molding determined by a water immersion method (water temperature 23° C.) to determine the apparent density (g / L) of the expanded bead molding.

[0123] [Tensile strength] (Table 4, Table 7) The values ​​were measured in accordance with JIS K6767-1999. A 10 mm thick plate-shaped piece was cut out from the center of the foamed bead molding, excluding the skin layer, and then punched out into a No. 1 dumbbell-shaped test piece using a press. After conditioning the test piece for 24 hours under standard conditions, it was tested using a Shimadzu Autograph AGS-X universal testing machine at a test speed of 500 mm / min to determine the tensile strength. The maximum load obtained in the test was taken as the tensile strength, and the average value of the tensile strengths determined for the five test pieces is shown in the table.

[0124] [Compressive stress at 50% strain] (Table 4, Table 7) A test piece measuring 50 mm long x 50 mm wide x 25 mm thick was cut out from the expanded bead molding, excluding the skin, and a compression test was carried out at a compression speed of 10 mm / min according to JIS K6767-1999 to determine the 50% compressive stress of the expanded bead molding. The test was carried out on five test pieces, and the average of the obtained values ​​is shown in the table as the compressive stress at 50% strain. The apparent density of the test piece used in this measurement is shown in the table as the test piece density. The test piece density was measured in the same manner as in the measurement of the density of the expanded bead molding, except that the test piece was cut out by removing the skin from the molding. The compressive stress at 50% strain is an index of the rigidity of the expanded bead molding. [Explanation of symbols]

[0125] a Specific peak appears on the low temperature side b High temperature peak TE End of melting temperature α 80°C point on the DSC curve β The point on the DSC curve indicating the end temperature TE of melting of the foamed beads γ The bottom point of the valley between the intrinsic peak a and the high-temperature peak b

Claims

1. A melt-mixing step (A) of melt-mixing a propylene-based random copolymer (I) having a melting point of 120° C. or more with a recovered polyolefin-based resin (II) having a melting point of 125 to 170° C. to obtain a melt-mixed resin; a resin particle production step (B) of obtaining resin particles from the molten mixed resin; and (C) an expansion step of expanding the resin particles to obtain expanded resin particles, the recovered polyolefin resin (II) is a pellet made from one or more recovered fishery products selected from the group consisting of fishing nets, fishing lines, and fishing ropes, and has an ash content of 3 mass% or less; In the melt-mixing step (A), 40% by mass or more and 95% by mass or less of the propylene-based random copolymer (I) and 5% by mass or more and 60% by mass or less of the recovered polyolefin-based resin (II) are melt-mixed (with the proviso that the total amount of the propylene-based random copolymer (I) and the recovered polyolefin-based resin (II) is 100% by mass).

2. The method for producing resin foam beads according to claim 1, characterized in that the melt flow rate of the propylene random copolymer (I) at 230°C and a load of 2.16 kg is 1 g / 10 min or more and 10 g / 10 min or less, and the melt flow rate of the recovered polyolefin resin (II) at 230°C and a load of 2.16 kg is smaller than the melt flow rate of the propylene random copolymer (I).

3. 3. The method for producing expanded resin beads according to claim 1, wherein the recovered polyolefin resin (II) contains a high-density polyethylene resin having a melting point of 125° C. or higher and 145° C. or lower.

4. The method for producing the resin foamed beads according to any one of claims 1 to 3, characterized in that the resin foamed beads are used as test pieces, and a first DSC curve is measured in accordance with heat flux differential scanning calorimetry according to JIS K7121-1987, in which the resin foamed beads are heated and melted at a heating rate of 10°C / min from 30°C to a heating end temperature that is 30°C higher than the end of the melting peak, and the first DSC curve has two or more melting peaks, and the two or more melting peaks include a melting peak specific to the resin constituting the resin foamed beads and a high-temperature melting peak having a peak temperature higher than the peak temperature of the specific melting peak, and the resin foamed beads are then held at the heating end temperature for 10 minutes, cooled to 30°C at a cooling rate of 10°C / min, and heated and melted again at a heating rate of 10°C / min to a temperature 30°C higher than the end of the melting peak, in which the high-temperature melting peak does not appear in the second DSC curve.

5. The method for producing expanded resin beads according to any one of claims 1 to 4, characterized in that the resin beads are multi-layered resin beads having a core layer containing a mixture of a propylene-based random copolymer (I) and a recycled polyolefin-based resin (II) as a base resin, and a coating layer containing a polyolefin-based resin (III) as a base resin that coats the core layer.

6. In the expansion step (C), the resin particles are expanded to a bulk density of 10 kg / m ３ More than 100kg / m ３ The method for producing expanded resin beads according to any one of claims 1 to 5, characterized in that the following expanded resin beads are obtained:

7. The method for producing expanded resin beads according to any one of claims 1 to 6, characterized in that the melting point of the propylene-based random copolymer (I) is 135°C or higher and 160°C or lower.

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