JP2024026078A - Recycled resin materials and finely pulverized materials for recycled resin materials - Google Patents

Abstract

The present invention provides a pelletized resin recycled material and a finely pulverized material for the resin recycled material. [Solution] A recycled resin material in the form of pellets obtained from a crosslinked polyolefin resin foam with a gel fraction of 65% or more, the recycled resin material having no pellet holes evaluated by the following evaluation method. It is. (Evaluation method) Observe the cross section of the pellet-shaped recycled resin material using an optical microscope. As a result of observation, if there is a hole of 0.1 mm or more, this is evaluated as a pellet hole. Further, the recycled resin material has a melt index measured in accordance with JIS K7210-1 of 0.1 g/10 minutes or more and 12 g/10 minutes or less. [Selection diagram] None

Description

The present disclosure relates to a method of manufacturing a recycled resin material.

In recent years, plastic foams have been used in large quantities for various purposes, and the disposal of waste has become a social issue. In particular, crosslinked polyolefin foams are used in large quantities in various miscellaneous goods, civil engineering, and construction materials, but because they have a three-dimensional crosslinked structure, they are not easily melted by heating. Therefore, it is difficult to reshape and reuse, and most of it is incinerated or landfilled, and there is currently no effective recycling method.
Recently, a method of plasticizing crosslinked polyolefin foam and using it as a recycled material has been studied. For example, Patent Documents 1 and 2 propose a method of plasticizing crosslinked polyolefin foam to the extent that it can be reused by applying heat and shearing force to eliminate the influence of the blowing agent remaining in the crosslinked polyolefin foam and odor during extrusion. .
Furthermore, Patent Document 3 proposes a regeneration treatment method in which a crosslinked polyolefin resin pulverized body is melt-kneaded two or more times while applying a shearing force at a predetermined temperature to achieve high fluidity and a low gel fraction. .

Japanese Patent Application Publication No. 2001-347558 Japanese Patent Application Publication No. 2006-175717 Japanese Patent Application Publication No. 2006-312315

Any of the methods disclosed in Patent Documents 1, 2, and 3 is a processing method that allows a recycled product to be obtained and is fully recyclable.
However, in Patent Documents 1 and 2, the resin is heated to a high temperature of 300° C. during plasticization, which causes problems such as yellowing, burning, and deterioration of physical properties, as well as problems such as low processing efficiency.
Further, in Patent Document 3, a good recycled product can be obtained, but there is a problem that it cannot be recycled if the gel fraction of the raw material is high.
The present disclosure has been made in view of the above circumstances, and aims to obtain resin recycled material with high efficiency without deteriorating the resin.
The present inventors have conducted extensive research in order to develop a new method for producing recycled resin materials. As a result, a cross-linked polyolefin resin foam with a high gel fraction was roughly pulverized in a pulverizer, heated and extruded in a single-screw extruder, and immediately after being discharged from a die, it was cut into a finely pulverized product. We have discovered that recycled materials can be obtained with high efficiency by melt-kneading using an extruder without degrading the resin. The present disclosure has been made based on this knowledge. The present disclosure can be realized as the following forms.

[1] A coarse crushing step of coarsely crushing the crosslinked polyolefin resin foam using a crusher;
A pulverization step of heating and extruding the coarsely pulverized resin foam with a single screw extruder and cutting it to obtain a finely pulverized product;
A method for producing a recycled resin material, comprising a melt-kneading step of melt-kneading the finely pulverized material using a co-directional twin-screw extruder.

According to the manufacturing method of the present disclosure, recycled material can be obtained with high efficiency without deteriorating the resin.

FIG. 2 is a schematic diagram showing an example of a barrel screw configuration of a co-directional twin-screw extruder. It is an explanatory view (sectional view) explaining minimum tip clearance.

Here, a desirable example of the present disclosure will be shown.
[2] The method for producing a recycled resin material according to [1], wherein the minimum tip clearance of the co-directional twin-screw extruder is greater than 0.01 mm and less than or equal to 0.2 mm.
If the minimum tip clearance is greater than 0.01 mm and less than 0.2 mm, the resin blocking capacity of the co-directional twin screw extruder will be increased, the pressure in the pressure holding zone will be increased, and the kneading process will be improved. The effect of obtaining sufficient shearing force in the zone to obtain a recycled resin material with few bubbles and a low gel fraction can be expected.
[3] The finely pulverized product has a gel fraction of 65% or more, an average particle size of 2.0 mm or more and 5.0 mm or less, and a bulk specific gravity of 0.10 g/ml or more and 0.50 g/ml or less. A method for producing a recycled resin material according to [1] or [2].
If the average particle diameter is 2.0 mm or more and 5.0 mm or less and the bulk specific gravity is 0.10 g/ml or more and 0.50 g/ml or less, the co-directional melt kneading process of melt-kneading with a co-directional twin screw extruder It can be expected to be effective in preventing feedneck defects when feeding materials from the hopper mouth of a twin-screw extruder.
[4] The method for producing a recycled resin material according to any one of [1] to [3], wherein the pulverized material contains an organic blowing agent of 0.01% by mass or more and 5.0% by mass or less .
[5] In the melt-kneading step, 1 part by mass or more and 10 parts by mass or less of zinc oxide is added to 100 parts by mass of the finely pulverized material, according to any one of [1] to [4]. Method for producing recycled resin material.
By adding zinc oxide, the decomposition reaction temperature of the pyrolytic organic foaming agent remaining in the finely ground material is lowered, and the reaction is completed in the same direction twin screw extruder, resulting in sudden foaming during remolding. This can be expected to have the effect of suppressing defects caused by this process and obtaining recycled resin material with fewer bubbles.

The present invention will be explained in detail below. Note that the expression "x to y" indicates that x and y fall within the range unless otherwise specified.
That is, a description using "~" for a numerical range includes the lower limit value and the upper limit value, unless otherwise specified. For example, the description "10 to 20" includes both the lower limit value of "10" and the upper limit value of "20". That is, "10 to 20" has the same meaning as "10 or more and 20 or less".

1. Method for producing recycled resin material The method for producing recycled resin material of the present disclosure includes a coarse crushing step of coarsely crushing a crosslinked polyolefin resin foam using a crusher, and a heating extrusion of the coarsely crushed resin foam using a single-screw extruder. , a pulverization step of cutting and obtaining a finely pulverized product, and a melt-kneading step of melt-kneading the pulverized product using a co-directional twin-screw extruder.

In the present disclosure, "recycled resin material" refers to a material manufactured by processing at least one of used resin foam (molded product) and waste generated from the manufacturing process of resin foam, and is a material that is manufactured by processing at least one of used resin foam (molded product) and waste generated from the manufacturing process of resin foam, and is used to create new resin foam. Refers to materials that can be used as materials.

(1) Coarse pulverization process The coarse pulverization process is a process in which a crosslinked polyolefin resin foam is coarsely pulverized using a pulverizer.
"Crosslinked polyolefin resin foam" is a polyolefin resin that is crosslinked and foamed by heating a pyrolytic blowing agent, an organic peroxide, and various additives that are blended as necessary. A suitable example is one in which a decomposable foaming agent and various additives are blended, crosslinked with ionizing radiation, and then heated and foamed.
Examples of the polyolefin resin include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene. Moreover, two or more types of these homopolymers or copolymers can also be mixed. Among these, polyethylene resins and polypropylene resins are preferably used.
Examples of the polyethylene resin include low density polyethylene, linear low density polyethylene, linear very low density polyethylene, medium density polyethylene, high density polyethylene, and copolymers containing ethylene as a main component.
The copolymer containing ethylene as a main component includes ethylene and one or more comonomers selected from α-olefins having 3 to 10 carbon atoms, vinyl esters, unsaturated carboxylic acid esters, conjugated dienes, and non-conjugated dienes. Examples include copolymers of . Examples of the α-olefin having 3 to 10 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. Examples of vinyl esters include vinyl acetate and vinyl propionate. Examples of unsaturated carboxylic esters include methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.
Examples of the polypropylene resin include homopolypropylene (a propylene homopolymer) and a copolymer of propylene and an α-olefin (excluding propylene). Examples of α-olefins include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, and 1-decene.

Pyrolytic blowing agents are various known organic blowing agents, such as azodicarbonamide (hereinafter abbreviated as "ADCA"), dinitrosopentamethylenetetramine, 4,4'-oxybisbenzenesulfonyl hydrazide, azobisiso Examples include butyronitrile, and those using azodicarbonamide are particularly preferred. The crosslinked polyolefin foam may contain additives such as various flame retardants, fillers, antioxidants, and colorants depending on the purpose.
The content of the organic blowing agent in the resin foam is not particularly limited. The content of the organic blowing agent in the resin foam is usually 0.01% by mass or more and 5.0% by mass or less, when the entire resin foam is 100% by mass. The content of the organic blowing agent in the finely pulverized product is also usually 0.01% by mass or more and 5.0% by mass or less, when the entire pulverized product is 100% by mass.
Examples of the organic peroxide (crosslinking agent) include dicumyl peroxide (hereinafter abbreviated as "DCP"), 2,5-dimethyl-2,5-bis-tert-butylperoxyhexene, 1,3 -bis-tert-peroxyisopropylbenzene and the like.
The gel fraction of the resin foam is not particularly limited. Gel fraction is measured according to JIS K6796. The gel fraction of the finely pulverized product is equivalent to that of the resin foam. This is because finely pulverized resin foam is obtained by heating and extruding coarsely pulverized resin foam using a single-screw extruder and cutting it, and no treatments that affect the gel fraction are carried out during these steps. This is because they are not.
The manufacturing method of the present disclosure is very useful for regenerating highly crosslinked resin foams (finely pulverized) with a gel fraction of 65% or more, particularly resin foams (finely pulverized) with a gel fraction of 70% or more. be. The gel fraction of the resin foam (finely pulverized material) may be 100%, but is usually 85% or less. The prior art is applied to resin foams having a gel fraction of 60% or less. Conventional techniques have not been able to reproduce highly crosslinked resin foams with a high gel fraction of 65% or more. In particular, the manufacturing method of the present disclosure can regenerate even a highly crosslinked resin foam with a high gel fraction of 65% or more while suppressing resin deterioration. This effect is a particularly advantageous effect of the present disclosure over the prior art.

"Coarsely pulverizing" means pulverizing to a size of 20 mm to 50 mm using a pulverizer such as a jaw crusher, rotary cutter mill, roll mill, or hammer mill.
The size of 20 mm to 50 mm is the maximum length of a coarsely pulverized resin molded body measured with a caliper in accordance with JIS B7507.

(2) Fine pulverization step The pulverization step is a step in which the coarsely pulverized resin foam is heated and extruded using a single-screw extruder and cut to obtain a finely pulverized product.
The resin foam is heated by heating the barrel of the single screw extruder. Since the resin foam contains a crosslinked polyolefin, it is heated and extruded in an unmolten state or a slightly molten state.
The temperature of the kneading zone of the single screw extruder is not particularly limited. The temperature of the kneading zone is preferably 150° C. or more and 200° C. or less from the viewpoint of suppressing resin deterioration and obtaining a finely pulverized material for producing resin recycled material with high efficiency. The temperature of the kneading zone is the barrel temperature of the portion of the screw where the kneading zone is located. The temperature of the kneading zone is usually measured with a thermocouple or the like attached to the barrel. To set the temperature of the kneading zone to a predetermined temperature, external heating using an extruder barrel heater or the like is generally used, but it may also be achieved by shear heat generation of the resin foam.
The rotational speed of the screw is not particularly limited. The rotational speed of the screw is, for example, 5 rpm or more and 50 rpm or less.
The shear rate is not particularly limited. The shear rate is, for example, 120/s or more and 1200/s or less.
The finely ground material has a smaller size than the coarsely ground resin foam. The finely pulverized material is used in order to avoid feed neck defects when feeding the material from the hopper mouth of the co-directional twin-screw extruder in the next process, which is melt-kneading in the co-directional twin-screw extruder. The average particle size is preferably 2.0 mm or more and 5.0 mm or less. The average particle size is determined by randomly selecting 50 particles (finely pulverized particles) using an optical microscope, measuring the maximum length of the particles, and averaging the values.
The bulk specific gravity of the finely pulverized product is not particularly limited. The bulk specific gravity of the finely pulverized material is determined in order to avoid feed neck defects when feeding the material from the hopper mouth of the co-directional twin-screw extruder in the next melt-kneading process, which is melt-kneading in the co-directional twin-screw extruder. From the viewpoint of this, it is preferably 0.15 or more and 0.25 or less. Bulk specific gravity is measured in accordance with JIS K7365.

(3) Melt-kneading step The melt-kneading step is a step of melt-kneading the finely pulverized material using a co-directional twin-screw extruder. In the melt-kneading step, a co-rotating twin screw extruder, that is, a co-rotating twin screw extruder is used. The extruder may be equipped with degassing equipment such as a vent (vacuum vent), if necessary, in order to remove volatile components generated during the plasticization process.
The extruder screw is composed of a feed zone, a kneading zone, a pressure holding zone, and a feeding zone (extrusion zone) in order from the hopper mouth. However, a pressure holding zone may be provided in the middle of the kneading zone.
For the feed zone, a screw-shaped element called a flight is usually used. The feed zone is a zone where the material input from the hopper mouth is heated and conveyed to the kneading zone.
The kneading zone is mainly composed of elements called kneading disks and rotors, and is a zone that applies shear to the material. The length of the kneading zone is not particularly limited. The length of the kneading zone should be set at L/D of 5 or more and 30 or more, from the viewpoint of applying sufficient shear to the pulverized material, suppressing deterioration in quality due to excessive plasticization, and increasing the throughput per unit time. The following is preferable, and 10 or more and 30 or less are more preferable.
In addition, in "L/D", L=screw length and D=screw diameter. L/D is the ratio of length to diameter.

The kneading zone consists of a single zone. A pressure holding zone is provided at the end of the kneading zone on the extrusion head side, which serves to dam up or reverse feed the material. This zone consists of elements that act to dam up or reverse feed the material, typically sealing discs, reverse flights, reverse kneading disc elements, etc. The pressure holding zone has the role of increasing the pressure of the kneading zone and ensuring sufficient residence time for the crosslinked polyolefin to plasticize in the kneading zone, and its length is 0.25 to 2.5 in L/D. degree is desirable. In addition, it is necessary to provide a pressure holding zone at least behind the kneading zone (on the downstream side), but in some cases it may be placed in the middle of the kneading zone, or in the middle of the kneading zone and immediately after the kneading zone. A plurality of them may be arranged. If the length of the pressure holding zone is shorter than L/D=0.25, it becomes difficult to maintain the pressure in the kneading zone, and if it is longer than 2.5, the throughput cannot be increased and the kneading zone is Shear heat generation increases, causing a decline in the quality of the plasticized product.
The feeding zone closest to the extrusion head has the function of cooling the plasticized crosslinked polyolefin to a temperature suitable for extrusion molding to prevent recrosslinking reactions and deterioration reactions after extrusion, and extruding the plasticized product at a constant speed. The length of the feeding zone is preferably 5 or more in terms of L/D. The length of the feed zone is typically 30 L/D or less. By setting the length of the feeding zone to L/D=5 or more, burning, coloring, etc. caused by the heated plasticized material in the kneading zone being extruded without being cooled can be suppressed.

The temperature of the kneading zone of the co-directional twin-screw extruder is not particularly limited. The temperature of the kneading zone is set to 170°C or higher from the viewpoint of foaming the pyrolytic foaming agent remaining in the crosslinked polyolefin, suppressing problems caused by sudden foaming during remolding, and suppressing resin deterioration. The temperature is preferably 250°C or lower, more preferably 175°C or higher and 235°C or lower, and even more preferably 180°C or higher and 230°C or lower. The temperature of the kneading zone is the barrel temperature of the portion of the screw where the kneading zone is located. The temperature of the kneading zone is usually measured with a thermocouple or the like attached to the barrel. To set the temperature of the kneading zone to a predetermined temperature, external heating using an extruder barrel heater or the like is generally used, but it may also be achieved by shear heat generation of the resin foam.

An example of the barrel screw configuration of a co-directional twin-screw extruder is shown in FIG. 1. In the kneading zone, kneading is performed using a kneading disk (symbol K). In the kneading zone, there is a part where the resin is blocked using a reversing disk (symbol LL). Preferably, a vent is installed at this location. The number of parts to be blocked is not particularly limited. It is preferable that a plurality of blocking portions be provided.

The minimum tip clearance of the co-directional twin-screw extruder is not particularly limited. This minimum chip clearance increases the resin damming ability in the part where the resin is blocked using the reverse feed disk, increases the pressure in the pressure holding zone, and obtains sufficient shearing force in the kneading zone to prevent air bubbles. From the viewpoint of obtaining a recycled resin material with a low gel fraction, the diameter is preferably greater than 0.01 mm and less than or equal to 0.2 mm.
As shown in FIG. 2, the minimum tip clearance refers to the clearance between the elliptical disc 1 provided on the screw and the inner wall surface 3A of the barrel 3, which is the clearance between the elliptical longitudinal end 1A of the disc 1 and the barrel 3. This refers to the minimum clearance C between the inner wall surface 3A and the inner wall surface 3A.

In the co-directional twin-screw extruder, the shear rate in the kneading zone is not particularly limited. The shear rate in the kneading zone is determined from the viewpoint of preventing feed neck failure when feeding the material from the hopper port of the co-directional twin screw extruder in the melt-kneading process, and from the viewpoint of preventing the occurrence of feed neck defects, and from the viewpoint of using recycled resin material with a low gel fraction. From the viewpoint of obtaining, 5000/s or more and 10000/s or less are preferable, and 7000/s or more and 9000/s or less are more preferable. This shearing rate is a value obtained by dividing the peripheral speed (mm/s) of the outermost peripheral portion of the screw element by the clearance (mm) between the screw and the barrel (corresponding to the above-mentioned "minimum tip clearance"). The higher the shear rate, the greater the shear stress that can be applied to the material.

In the melt-kneading step, it is preferable that 1 part by mass or more and 10 parts by mass or less of zinc oxide be added to 100 parts by mass of the finely pulverized material. By adding zinc oxide in this proportion, the reaction temperature of the organic blowing agent is lowered, so that the expansion of the organic blowing agent can be completed in the twin-screw extruder, and as a result, there is no sudden change during remolding. It can be expected to suppress problems caused by foaming.

2. Method for producing resin foam using recycled resin material The method for producing a new resin foam using recycled resin material is not particularly limited. For example, resin foam can be created by blending a thermally decomposable blowing agent and an organic peroxide with a recycled resin material alone or with a mixture of recycled resin and a thermoplastic polyolefin resin in an arbitrary ratio, and then cross-linking and foaming the mixture with heat. can be manufactured.

Examples will be shown to further specifically explain the present disclosure. However, the present disclosure is not limited to this embodiment, and can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art.

Various measured values in the following description are measured by the following measuring methods.

1. Measurement method (1) Average particle size The average particle size was determined by randomly selecting 50 particles (finely pulverized particles) using an optical microscope, measuring the maximum length of the particles, and averaging the values.
(2) Bulk specific gravity Bulk specific gravity was measured in accordance with JIS K7365.
(3) Gel fraction Gel fraction was measured according to JIS K6796.
(4) Pellet holes The cross section of pellet particles (pellet-shaped recycled resin material) was observed using an optical microscope. As a result of observation, if there was a hole of 0.1 mm or more, this was evaluated as a pellet hole. The smaller the amount, the better in order to suppress void defects during remolding.
(5) MI (melt index)
MI was measured in accordance with JIS K7210-1.
(6) Appearance of pellet Burning was observed. Here, "burning" refers to the resin becoming hot due to excessive shearing, reacting with oxygen present in the extruder or with oxygen when exposed to the environment outside the extruder, oxidizing and deteriorating, and becoming a combustible product. , refers to yellowing or black spots.
(7) Apparent Density Apparent density was measured in accordance with JIS Z8807.

2. Production of recycled resin material (2.1) Examples 1 to 4
By blending ADCA and DCP with polyolefin and heating, a crosslinked polyolefin resin foam (apparent density 0.064 g/ml, gel fraction 70%) was obtained. The crosslinked polyolefin resin foam was coarsely pulverized using a pulverizer. The coarsely pulverized resin foam was heated and extruded using a single screw extruder and cut to obtain a finely pulverized product (bulk specific gravity: 0.21 g/ml). 3 parts by mass of zinc oxide was added to 100 parts by mass of the finely pulverized material, and the mixture was melt-kneaded in a co-directional twin-screw extruder to obtain a recycled resin material. Note that the resin recycled material was pelletized.
Tables 1 and 2 show the settings of the co-directional twin-screw extruder (simply described as "twin-screw extruder" in the table) for melt-kneading. Tables 1 and 2 also list other conditions. Based on the conditions of Example 1, the minimum tip clearance was changed in Examples 2 to 4.

(2.2) Example 5
As shown in Table 3, a recycled resin material was obtained in the same manner as in Example 1, except that the bulk specific gravity of the finely ground material was 0.45 g/ml.

(2.3) Example 6
As shown in Table 3, a recycled resin material was obtained in the same manner as in Example 1 except that the content of the organic blowing agent was 4.8% by mass.

(2.4) Comparative example 1
By blending ADCA and DCP with polyolefin and heating, a crosslinked polyolefin resin foam (apparent density 0.064 g/ml, gel fraction 70%) was obtained. The crosslinked polyolefin resin foam was pulverized using a pulverizer to obtain a pulverized product (bulk specific gravity: 0.075 g/ml). 3 parts by mass of zinc oxide was added to 100 parts by mass of the pulverized material, and the mixture was melt-kneaded using a co-directional twin-screw extruder to form pellets, but the bulk specific gravity of the pulverized product was low, so it was not put into the co-directional twin-screw extruder. could not.
Table 4 shows the settings of the codirectional twin-screw extruder (simply described as "twin-screw extruder" in the table) during melt-kneading. Table 4 also lists other conditions.

(2.5) Comparative example 2
As Comparative Example 2, a method for producing a recycled resin material described in JP-A No. 2001-347558 is shown. This method does not employ heated extrusion using a single screw extruder. Further, the barrel temperature in the co-directional twin-screw extruder is set to a high temperature of 300° C. or higher.
The manufacturing method of Comparative Example 2 will be specifically shown. By blending ADCA and DCP with polyolefin and heating, a crosslinked polyolefin resin foam (gel fraction 60%) was obtained. The crosslinked polyolefin resin foam was pulverized using a pulverizer. The pulverized material was melt-kneaded using a co-directional twin-screw extruder to obtain a recycled resin material.
Table 4 shows the settings of the co-directional twin-screw extruder during melt-kneading. Table 4 also lists other conditions.

(2.6) Comparative example 3
As Comparative Example 3, a method for producing a recycled resin material described in JP-A No. 2006-175717 is shown. This method does not employ heated extrusion using a single screw extruder. Further, the barrel temperature in the co-directional twin-screw extruder is set to a high temperature of 300° C. or higher.
The manufacturing method of Comparative Example 3 will be specifically shown. By blending ADCA and DCP with polyolefin and heating, a crosslinked polyolefin resin foam (gel fraction 60%) was obtained. The crosslinked polyolefin resin foam was pulverized using a pulverizer. 5 parts by mass of zinc oxide and 50 parts by mass of additional polyolefin were added to 100 parts by mass of the pulverized material, and the mixture was melt-kneaded in a co-directional twin-screw extruder to obtain a recycled resin material.
Table 5 shows the settings of the co-directional twin-screw extruder during melt-kneading. Table 5 also lists other conditions.

(2.7) Comparative example 4
As Comparative Example 4, a method for producing a recycled resin material described in JP-A No. 2006-312315 is shown. In this method, a crosslinked polyolefin foam with a gel fraction of 35% is used as a raw material.
The manufacturing method of Comparative Example 4 will be specifically shown. By blending ADCA and DCP with polyolefin and heating the mixture, a crosslinked polyolefin resin foam (gel fraction: 35%) was obtained. The crosslinked polyolefin resin foam was pulverized using a pulverizer. The pulverized material was melt-kneaded twice using a twin-screw extruder in the same direction to obtain a recycled resin material.
Table 5 shows the settings of the co-directional twin-screw extruder during melt-kneading. Table 5 also lists other conditions.

(2.8) Comparative example 5
In Comparative Example 5, a crosslinked polyolefin foam with a gel fraction of 70% is used as a raw material.
The manufacturing method of Comparative Example 5 will be specifically shown. A crosslinked polyolefin resin foam (gel fraction 70%) was obtained by blending ADCA and DCP with polyolefin and heating the mixture. The crosslinked polyolefin resin foam was pulverized using a pulverizer. The pulverized material was melt-kneaded using a co-directional twin-screw extruder to obtain a recycled resin material.
Table 6 shows the settings of the co-directional twin-screw extruder during melt-kneading. Table 6 also lists other conditions.

3. Evaluation The evaluation results are shown in Tables 1 to 6.
In Examples 1 to 6, even when resin foams with a gel fraction of 65% or more were used, recycled resin materials with no pellet holes and no burning could be produced. Furthermore, in Examples 1 to 6, the recycled resin material can be produced continuously, so the production efficiency is high.
Among Examples 1 to 4, in Examples 1 to 2 in which the minimum tip clearance of the co-directional twin screw extruder is greater than 0.01 mm and 0.2 mm or less, the amount of resin flowing downstream due to the small tip clearance is was suppressed, the resin was well blocked in the barrel, and kneading was performed well. The recycled resin materials obtained in Examples 1 and 2 had high MI and good fluidity.
In Example 5, in which the bulk specific gravity of the finely pulverized material was higher than in Example 1, a recycled resin material without pellet holes and without burning could be produced.
Even in Example 6, in which the content of the organic blowing agent was higher than in Example 1, a recycled resin material without pellet holes and burnt could be produced.
In Comparative Example 1, as described above, a mixture of powder material and zinc oxide was melt-kneaded using a co-directional twin-screw extruder and an attempt was made to pelletize it, but the bulk specific gravity of the pulverized product was low, and co-directional twin-screw extrusion was not possible. I couldn't put it into the machine. In other words, in Comparative Example 1, a reusable pellet-shaped resin recycled material could not be produced.
In Comparative Example 2, the barrel temperature (temperature of the kneading zone of the co-directional twin-screw extruder) was too high, causing pellet holes, discoloration, and burns in the recycled resin material.
In Comparative Example 3, only a resin foam with a low gel fraction of 60% or less was recycled, but a resin foam with a high gel fraction could not be recycled. Moreover, in Comparative Example 3, the barrel temperature (temperature of the kneading zone of the co-directional twin-screw extruder) was too high, causing discoloration and burning in the recycled resin material.
In Comparative Example 4, only a resin foam with a low gel fraction of 35% was recycled, but a resin foam with a high gel fraction could not be recycled.
In Comparative Example 5, the content of the organic blowing agent was high, resulting in excessive foaming during extrusion. Therefore, it could not be pelletized and a recycled resin material could not be produced.

4. Effects of Examples In Examples 1 to 6, recycled resin materials with little resin deterioration could be produced even when resin foams with a high gel fraction were used.

1...Disk 1A...End 3...Barrel 3A...Inner wall surface C...Clearance LR...Forward feed disk LL...Reverse feed disk K...Kneading disk

Claims (5)

a coarse crushing step of coarsely crushing the crosslinked polyolefin resin foam with a crusher;
A pulverization step of heating and extruding the coarsely pulverized resin foam with a single screw extruder and cutting it to obtain a finely pulverized product;
A method for producing a recycled resin material, comprising a melt-kneading step of melt-kneading the finely pulverized material using a co-directional twin-screw extruder. The method for producing recycled resin material according to claim 1, wherein the minimum tip clearance of the co-directional twin-screw extruder is greater than 0.01 mm and less than or equal to 0.2 mm. The finely pulverized product has a gel fraction of 65% or more, an average particle size of 2.0 mm or more and 5.0 mm or less, and a bulk specific gravity of 0.10 g/ml or more and 0.50 g/ml or less. The method for producing a recycled resin material according to claim 1 or 2. The method for producing a recycled resin material according to any one of claims 1 to 3, wherein the finely pulverized material contains an organic blowing agent of 0.01% by mass or more and 5.0% by mass or less. The recycled resin material according to any one of claims 1 to 4, wherein in the melt-kneading step, 1 part by mass or more and 10 parts by mass or less of zinc oxide is added to 100 parts by mass of the finely pulverized material. manufacturing method.

Images