JP2021195482A - Method for producing resin recycled material - Google Patents

Abstract

To highly efficiently acquire resin recycled material without degrading resin.SOLUTION: A method for producing resin recycled material comprises: a coarsely crushing step of coarsely crushing resin foam of crosslinked polyolefin with a crusher; a finely crushing step of heating and extruding the coarsely crushed resin foam with a single screw extruder, cutting the resin foam thereby obtaining a finely crushed material; and a melt-kneading step of melt-kneading the finely crushed material with a co-rotating twin screw extruder.SELECTED DRAWING: None

Description

The present disclosure relates to a method for producing a recycled resin material.

In recent years, a large amount of plastic foam has been used for various purposes, and waste treatment has become a social problem. In particular, crosslinked polyolefin foam is used in large quantities in various miscellaneous goods, civil engineering, and building materials, but it is not easy to heat and melt because it has a three-dimensional crosslinked structure. Therefore, it is difficult to remold and reuse, and most of them are incinerated or landfilled, and there is no effective recycling method at present.
Recently, a method of using a crosslinked polyolefin foam as a recycled material by plasticizing it has been studied. For example, Patent Documents 1 and 2 propose a method of applying heat and shearing force to eliminate the influence of the foaming agent remaining on the crosslinked polyolefin foam and the odor during extrusion, and to carry out the plasticization to a reusable level. ..
Further, Patent Document 3 proposes a regeneration treatment method in which a crosslinked polyolefin resin pulverized body is melt-kneaded twice or more while applying a shearing force at a predetermined temperature to have high fluidity and a low gel fraction. ..

Japanese Unexamined Patent Publication No. 2001-347558 Japanese Unexamined Patent Publication No. 2006-175717 Japanese Unexamined Patent Publication No. 2006-31315

Any of the methods of Patent Documents 1, 2 and 3 can obtain a recycled product and is a processing method that can be sufficiently reused.
However, in Patent Documents 1 and 2, since the temperature is as high as 300 ° C. at the time of plasticization, there are problems that the resin deteriorates, yellowing, burning, deterioration of physical properties, and further, processing efficiency is low.
Further, in Patent Document 3, a good recycled product can be obtained, but there is a problem that it cannot be recycled when the gel fraction of the raw material is high.
The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to obtain a resin recycled material with high efficiency without deteriorating the resin.
The present inventors have conducted extensive research to develop a new method for producing a recycled resin material. As a result, the crosslinked polyolefin resin foam having a high gel content is coarsely pulverized with a crusher, then heated and extruded with a single-screw extruder, and cut immediately after the die is discharged to obtain a finely pulverized product, and the finely pulverized product is biaxially oriented in the same direction. We have found the fact that recycled materials can be obtained with high efficiency without deteriorating the resin by melt-kneading with an extruder. This disclosure is based on this finding. The present disclosure can be realized in the following forms.

[1] A coarse pulverization step of coarsely pulverizing a resin foam of a crosslinked polyolefin with a pulverizer.
The coarsely pulverized resin foam is heated and extruded by a single-screw extruder and cut 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 product with a twin-screw extruder in the same direction.

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

It is a schematic diagram which shows an example of the barrel screw composition of the same direction twin screw extruder. It is explanatory drawing (cross-sectional view) explaining the minimum chip clearance.

Here are desirable examples of the present disclosure.
[2] The method for producing a recycled resin material according to [1], wherein the minimum chip clearance of the same-direction twin-screw extruder is larger than 0.01 mm and 0.2 mm or less.
When the minimum tip clearance is larger than 0.01 mm and 0.2 mm or less, the damming ability of the resin is increased, the pressure in the pressure holding zone is increased, and kneading is performed at the portion where the resin of the twin-screw extruder in the same direction is blocked. It is expected that a sufficient shearing force can be obtained in the zone to obtain a resin recycled material having few bubbles and a low gel content.
[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. The method for producing a recycled resin material according to [1] or [2].
When the average particle size 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 same direction is used in the melt-kneading step of melt-kneading with a twin-screw extruder in the same direction. When feeding materials from the hopper mouth of a twin-screw extruder, the effect of not causing a feed neck defect can be expected.
[4] The method for producing a recycled resin material according to any one of [1] to [3], wherein the finely pulverized product contains 0.01% by mass or more and 5.0% by mass or less of an organic foaming agent. ..
[5] The item according to any one of [1] to [4], wherein in the melt-kneading step, zinc oxide is added in an amount of 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the finely pulverized product. Manufacturing method of recycled resin material.
By adding zinc oxide, the decomposition reaction temperature of the pyrolysis-type organic foaming agent remaining in the finely pulverized product is lowered, and the reaction is completely reacted in the same-direction twin-screw extruder. It is expected that the effect of suppressing the trouble caused by the above and obtaining the resin recycled material with few bubbles can be expected.

Hereinafter, the present invention will be described in detail. Unless otherwise specified, the notation indicating the range "x to y" shall include x and y in the range.
That is, unless otherwise specified, the description using "~" for the numerical range includes the lower limit value and the upper limit value. For example, in the description of "10 to 20", both the lower limit value "10" and the upper limit value "20" are included. That is, "10 to 20" has the same meaning as "10 or more and 20 or less".

1. 1. Manufacturing Method of Recycled Resin Material The manufacturing method of the recycled resin material of the present disclosure includes a coarse crushing step of coarsely crushing a resin foam of a crosslinked polyolefin with a crusher and a heat extrusion of the coarsely crushed resin foam with a single-screw extruder. , A fine pulverization step of cutting to obtain a finely pulverized product, and a melt kneading step of melt-kneading the finely pulverized product with a twin-screw extruder in the same direction.

The "resin recycled material" in the present disclosure is a material produced by treating at least one of a used resin foam (molded product) and waste generated from the resin foam manufacturing process, and is a new resin foam. A material that can be used as a material for.

(1) Coarse pulverization step The coarse pulverization step is a step of coarsely pulverizing a resin foam of a crosslinked polyolefin with a pulverizer.
The "crosslinked polyolefin resin foam" is obtained by heating and cross-linking a polyolefin-based resin with a pyrolyzable foaming agent and an organic peroxide and various additives blended as necessary, and the polyolefin-based resin is heated. Pyrolytic foaming agents and various additives are blended, crosslinked with ionizing radiation, and then heated to foam.
Examples of the polyolefin-based resin include homopolymers obtained by polymerizing α-olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene, or copolymers. Further, two or more kinds of these homopolymers or copolymers can be mixed. Of these, polyethylene-based resins and polypropylene-based resins are preferably used.
Examples of the polyethylene-based resin include low-density polyethylene, linear low-density polyethylene, linear ultra-low-density polyethylene, medium-density polyethylene, high-density polyethylene, and a copolymer containing ethylene as a main component.
The copolymer containing ethylene as a main component includes ethylene and one or more comonomer selected from α-olefins having 3 to 10 carbon atoms, vinyl esters, unsaturated carboxylic acid esters, conjugated diene, and non-conjugated diene. , And the copolymer 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 the vinyl ester include vinyl acetate and vinyl propionate. Examples of unsaturated carboxylic acid esters include methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate.
Examples of the polypropylene-based resin include homopolypropylene (propylene homopolymer) and a copolymer of propylene and α-olefin (excluding propylene). Examples of the α-olefin include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene and 1-decene.

Pyrolytic foaming agents are various known organic foaming agents, such as azodicarbonamide (hereinafter abbreviated as "ADCA"), dinitrosopentamethylenetetramine, 4,4'-oxybisbenzenesulfonylhydrazide, and azobisiso. There are butyronitrile and the like, and those using azodicarbonamide are particularly preferable. The crosslinked polyolefin foam may contain additives such as various flame retardants, fillers, antioxidants and colorants, depending on the intended use.
The content of the organic foaming agent in the resin foam is not particularly limited. The content of the organic foaming agent in the resin foam is usually 0.01% by mass or more and 5.0% by mass or less when the total amount of the resin foam is 100% by mass. The content of the organic foaming agent in the finely pulverized product is also usually 0.01% by mass or more and 5.0% by mass or less when the total amount of the finely 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-terriary butylperoxyhexene, 1,3. -Bis-tershary peroxyisopropylbenzene and the like can be mentioned.
The gel fraction of the resin foam is not particularly limited. The gel fraction is measured according to JIS K6796. The gel fraction of the finely pulverized product is equivalent to the gel fraction of the resin foam. This is because the finely pulverized product is obtained by heating and extruding the resin foam, which is a coarsely pulverized resin foam, with a single-screw extruder and cutting it, and the treatment that affects the gel fraction is particularly performed during these steps. Because it is not.
The production method of the present disclosure is very useful for regenerating a highly crosslinked resin foam (finely pulverized product) having a gel fraction of 65% or more, particularly a resin foam (finely pulverized product) having a gel fraction of 70% or more. be. The gel fraction of the resin foam (finely pulverized product) 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 technology has not been able to regenerate a highly crosslinked resin foam having a gel fraction as high as 65% or more. In particular, the production method of the present disclosure can regenerate a highly crosslinked resin foam having a gel fraction as high as 65% or more while suppressing resin deterioration. This effect is a particularly advantageous effect of the present disclosure over prior art.

"Coarse crushing" means crushing to a size of 20 mm to 50 mm by using a crusher such as a jaw crusher, a rotary cutter mill, a roll mill, or a hammer mill.
The 20 mm to 50 mm size is a measurement of the maximum length of the coarsely pulverized resin molded product with a caliper in accordance with JIS B7507.

(2) Fine pulverization step The fine pulverization step is a step of heating and extruding a coarsely pulverized resin foam with a single-screw extruder and cutting it to obtain a finely pulverized product.
By heating the barrel of the uniaxial extruder, the resin foam is heated. Since the resin foam contains crosslinked polyolefin, it is heated and extruded in an unmelted state or a slightly melted 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 higher and 200 ° C. or lower from the viewpoint of suppressing deterioration of the resin and obtaining a finely pulverized product for producing a recycled resin material with high efficiency. The temperature of the kneading zone is the barrel temperature of the portion where the kneading zone of the screw is located. The temperature of the kneading zone is usually measured by a thermoelectric pair attached to the barrel. In order to set the temperature of the kneading zone to a predetermined temperature, external heating by an extruder barrel heater or the like is generally used, but it may be achieved by shear heat generation of the resin foam.
The rotation speed of the screw is not particularly limited. The rotation 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 pulverized product is smaller in size than the coarsely pulverized resin foam. The finely pulverized material is melt-kneaded in the same-direction twin-screw extruder, which is the next step. The average particle size is preferably 2.0 mm or more and 5.0 mm or less. The average particle size is obtained by randomly selecting 50 particles (finely pulverized substances) with an optical microscope, measuring the maximum length of the particles, and averaging the values.
The bulk specific density of the finely pulverized product is not particularly limited. The bulk specific density of the finely pulverized material should be adjusted so that a feed neck defect does not occur when the material is fed from the hopper opening of the same-direction twin-screw extruder in the melt-kneading process of melt-kneading in the same-direction twin-screw extruder, which is the next step. From the viewpoint of the above, 0.15 or more and 0.25 or less are preferable. The bulk specific density is measured according to JIS K7365.

(3) Melt-kneading step The melt-kneading step is a step of melt-kneading a finely pulverized product with a twin-screw extruder in the same direction. In the melt-kneading step, a twin-screw extruder that rotates in the same direction, that is, a twin-screw extruder in the same direction 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 feed zone (extrusion zone) in order from the hopper opening. However, a pressure holding zone may be provided in the middle of the kneading zone.
The feed zone uses a threaded element, usually called a flight. The feed zone is a zone in which the material input from the hopper mouth is transferred to the kneading zone while being heated.
The kneading zone is mainly composed of elements called kneading discs (kneading discs) and rotors, and is a zone that shears the material. The length of the kneading zone is not particularly limited. The length of the kneading zone is 5 or more and 30 in L / D from the viewpoint of giving sufficient shear to the finely pulverized material, suppressing deterioration of quality due to excessive plasticization, and increasing the processing amount per unit time. The following is preferable, and 10 or more and 30 or less are more preferable.
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 to dam the material or feed it back. This zone is composed of elements that act to dam or reverse the material, and usually seal discs, reverse flights, reverse kneading disc elements, etc. are used. The pressure holding zone has the role of increasing the pressure in the kneading zone and ensuring a sufficient residence time for the crosslinked polyolefin to be plasticized in the kneading zone, and its length is 0.25 to 2.5 in L / D. Degree is desirable. In addition, the pressure holding zone needs to be provided at least behind the kneading zone (on the downstream side), but in some cases, it may be placed in the middle part of the kneading zone, or in the middle part of the kneading zone and immediately after. Multiple arrangements may be made. If the length of the pressure holding zone is shorter than L / D = 0.25, it becomes difficult to hold the pressure in the kneading zone, and if it is longer than 2.5, the processing amount cannot be increased and the kneading zone The heat generated by shearing increases, which causes deterioration of the quality of the plastic.
The feed zone on the most extrusion head side has a function of cooling the plasticized crosslinked polyolefin to a temperature suitable for extrusion molding to prevent a recrosslinking reaction and a deterioration reaction after extrusion, and to extrude the thermoplastic at a constant speed. The length of the feed zone is preferably 5 or more in L / D. The length of the feed zone is usually 30 or less in L / D. By setting the length of the feed zone to L / D = 5 or more, it is possible to suppress burning, coloring, etc. caused by extruding the thermoplastic material heated in the kneading zone without being cooled.

The temperature of the kneading zone of the same-direction twin-screw extruder is not particularly limited. The temperature of the kneading zone is 170 ° C. or higher from the viewpoint of foaming and cutting off the pyrolyzable foaming agent remaining in the crosslinked polyolefin to suppress defects due to sudden foaming during remolding and suppressing resin deterioration. 250 ° C. or lower is preferable, 175 ° C. or higher and 235 ° C. or lower is more preferable, and 180 ° C. or higher and 230 ° C. or lower is further preferable. The temperature of the kneading zone is the barrel temperature of the portion where the kneading zone of the screw is located. The temperature of the kneading zone is usually measured by a thermoelectric pair attached to the barrel. In order to set the temperature of the kneading zone to a predetermined temperature, external heating by an extruder barrel heater or the like is generally used, but it may be achieved by shear heat generation of the resin foam.

FIG. 1 shows an example of a barrel screw configuration of a twin-screw extruder in the same direction. In the kneading zone, kneading is performed using a kneading disc (symbol K). In the kneading zone, there is a portion where the resin is blocked by using the reverse feed disk (symbol LL). It is preferable that a vent is installed at this site. The number of parts to be blocked is not particularly limited. It is preferable that a plurality of sites for blocking are provided.

The minimum chip clearance of the same-direction twin-screw extruder is not particularly limited. This minimum tip clearance increases the damming ability of the resin, increases the pressure in the pressure holding zone, and obtains sufficient shearing force in the kneading zone at the site where the resin is blocked by using the reverse feed disk, so that bubbles can be generated. From the viewpoint of obtaining a resin recycled material having a small amount and a low gel content, it is preferably larger than 0.01 mm and 0.2 mm or less.
As shown in FIG. 2, the minimum tip clearance is the clearance between the elliptical disk 1 provided in the screw and the inner wall surface 3A of the barrel 3, and the end 1A and the barrel 3 in the elliptical longitudinal direction of the disk 1. Refers to the clearance C, which is the minimum clearance with the inner wall surface 3A.

In the same-direction twin-screw extruder, the shear rate in the kneading zone is not particularly limited. The shear rate in the kneading zone is based on the viewpoint of preventing a feed neck defect when feeding the material from the hopper mouth of the twin-screw extruder in the same direction in the melt kneading step, and the resin recycled material having a low gel content. From the viewpoint of obtaining, it is preferably 5000 / s or more and 10000 / s or less, and more preferably 7000 / s or more and 9000 / s or less. This shear rate is a numerical 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 chip 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 to add 1 part by mass or more and 10 parts by mass or less of zinc oxide to 100 parts by mass of the finely pulverized product. By adding zinc oxide in this proportion, the reaction temperature of the organic foaming agent is lowered, so that the foaming of the organic foaming agent can be completed in the twin-screw extruder, and as a result, suddenly during remolding. It can be expected to suppress problems caused by foaming.

2. 2. Method for Producing Resin Foam Using Recycled Resin Material The method for producing a new resin foam using the recycled resin material is not particularly limited. For example, a resin foam can be obtained by blending a heat-decomposable foaming agent and an organic peroxide in a resin recycled material alone or a mixture of a resin recycled material mixed with a thermoplastic polyolefin resin in an arbitrary ratio and heat-crosslinking and foaming. Can be manufactured.

Examples will be shown and the present disclosure will be described in more detail. However, the present disclosure is not limited to this embodiment, and can be carried out in various embodiments with various changes and improvements based on the knowledge of those skilled in the art.

The various measured values in the following description are measured values by the following measuring methods.

1. 1. Measuring method (1) Average particle size The average particle size was determined by randomly selecting 50 particles (finely pulverized substances) with an optical microscope, measuring the maximum length of the particles, and averaging the values.
(2) Bulk specific density The bulk specific gravity was measured according to JIS K7365.
(3) Gel fraction The gel fraction was measured according to JIS K6796.
(4) Pellet hole The cross section of the pellet particles (pellet-shaped resin recycled material) was observed with an optical microscope. As a result of observation, when there was a hole of 0.1 mm or more, this was evaluated as a pellet hole. The smaller the number, the better, in order to suppress void defects during remolding.
(5) MI (melt index)
MI was measured according to JIS K7210-1.
(6) Appearance of pellets Burning was observed. Here, "burning" means that the temperature of the resin rises due to excessive shearing and reacts with oxygen existing in the extruder or when exposed to the environment outside the extruder, oxidatively deteriorates, and becomes a combustible product. , Yellowing or black spots.
(7) Apparent density The apparent density was measured according to JIS Z8807.

2. 2. Preparation of Recycled Resin Material (2.1) Examples 1 to 4
By blending the polyolefin with ADCA and DCP and heating, a resin foam of the crosslinked polyolefin (apparent density 0.064 g / ml, gel fraction 70%) was obtained. The resin foam of the crosslinked polyolefin was coarsely pulverized with a pulverizer. The coarsely crushed resin foam was heated and extruded with 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 product, and melt-kneaded with a twin-screw extruder in the same direction to obtain a recycled resin material. The recycled resin material was pelletized.
Tables 1 and 2 show the settings of the same-direction twin-screw extruder (in the table, simply referred to as "double-screw extruder") in melt-kneading. Tables 1 and 2 also describe other conditions. Based on the conditions of Example 1, the minimum chip clearance is 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 pulverized product was 0.45 g / ml.

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

(2.4) Comparative Example 1
By blending the polyolefin with ADCA and DCP and heating, a resin foam of the crosslinked polyolefin (apparent density 0.064 g / ml, gel fraction 70%) was obtained. The resin foam of the crosslinked polyolefin was pulverized with a pulverizer to obtain a pulverized product (bulk specific density 0.075 g / ml). 3 parts by mass of zinc oxide was added to 100 parts by mass of the crushed product, and melt-kneaded with a twin-screw extruder in the same direction to attempt pelletization. could not.
Table 4 shows the settings of the same-direction twin-screw extruder (in the table, simply referred to as "double-screw extruder") in melt-kneading. Table 4 also describes other conditions.

(2.5) Comparative Example 2
As Comparative Example 2, a method for producing a recycled resin material described in JP-A-2001-347558 is shown. In this method, heat extrusion with a single-screw extruder is not adopted. Further, the barrel temperature in the twin-screw extruder in the same direction is set to a high temperature of 300 ° C. or higher.
The manufacturing method of Comparative Example 2 is specifically shown. By blending ADCA and DCP with polyolefin and heating, a resin foam (gel fraction 60%) of crosslinked polyolefin was obtained. The resin foam of the crosslinked polyolefin was pulverized with a pulverizer. The crushed material was melt-kneaded with a twin-screw extruder in the same direction to obtain a recycled resin material.
Table 4 shows the settings of the same-direction twin-screw extruder in melt-kneading. Table 4 also describes other conditions.

(2.6) Comparative Example 3
As Comparative Example 3, a method for producing a recycled resin material described in JP-A-2006-175717 is shown. In this method, heat extrusion with a single-screw extruder is not adopted. Further, the barrel temperature in the twin-screw extruder in the same direction is set to a high temperature of 300 ° C. or higher.
The manufacturing method of Comparative Example 3 is specifically shown. By blending ADCA and DCP with polyolefin and heating, a resin foam (gel fraction 60%) of crosslinked polyolefin was obtained. The resin foam of the crosslinked polyolefin was pulverized with a pulverizer. To 100 parts by mass of the pulverized product, 5 parts by mass of zinc oxide and 50 parts by mass of additional polyolefin were added and melt-kneaded with a twin-screw extruder in the same direction to obtain a recycled resin material.
Table 5 shows the settings of the same-direction twin-screw extruder in melt-kneading. Table 5 also describes other conditions.

(2.7) Comparative Example 4
As Comparative Example 4, a method for producing a recycled resin material described in Japanese Patent Application Laid-Open No. 2006-31315 is shown. In this method, a crosslinked polyolefin foam having a gel fraction of 35% is used as a raw material.
The manufacturing method of Comparative Example 4 is specifically shown. By blending ADCA and DCP with polyolefin and heating, a resin foam (gel fraction 35%) of crosslinked polyolefin was obtained. The resin foam of the crosslinked polyolefin was pulverized with a pulverizer. The crushed material was melt-kneaded twice with a twin-screw extruder in the same direction to obtain a recycled resin material.
Table 5 shows the settings of the same-direction twin-screw extruder in melt-kneading. Table 5 also describes other conditions.

(2.8) Comparative Example 5
In Comparative Example 5, a crosslinked polyolefin foam having a gel fraction of 70% is used as a raw material.
The manufacturing method of Comparative Example 5 is specifically shown. By blending ADCA and DCP with polyolefin and heating, a resin foam (gel fraction 70%) of crosslinked polyolefin was obtained. The resin foam of the crosslinked polyolefin was pulverized with a pulverizer. The crushed material was melt-kneaded with a twin-screw extruder in the same direction to obtain a recycled resin material.
Table 6 shows the settings of the same-direction twin-screw extruder in melt-kneading. Table 6 also describes other conditions.

3. 3. Evaluation Evaluation results are shown in Tables 1-6.
In Examples 1 to 6, even if a resin foam having a gel fraction of 65% or more was used, it was possible to produce a resin recycled material having no pellet holes and no burning. Further, in Examples 1 to 6, since the recycled resin material can be continuously produced, the production efficiency is good.
Among Examples 1 to 4, in Examples 1 and 2 in which the minimum tip clearance of the twin-screw extruder in the same direction is larger than 0.01 mm and 0.2 mm or less, the amount of resin flowing to the downstream side due to the small tip clearance. Was suppressed, the resin was well blocked in the barrel, and kneading was well performed. The resin recycled materials obtained in Examples 1 and 2 had a high MI and good fluidity.
In Example 5, in which the bulk specific density of the finely pulverized product was higher than that in Example 1, it was possible to produce a resin recycled material having no pellet holes and no burning.
Even in Example 6 in which the content of the organic foaming agent was higher than that in Example 1, it was possible to produce a resin recycled material having no pellet holes and no burning.
In Comparative Example 1, as described above, a mixture of powdered material and zinc oxide was melt-kneaded with a twin-screw extruder in the same direction to attempt pelletization, but the bulk specific gravity of the crushed product was low and the twin-screw extrusion in the same direction was performed. I couldn't put it into the machine. That is, in Comparative Example 1, a reusable pellet-shaped resin recycled material could not be produced.
In Comparative Example 2, the barrel temperature (the temperature of the kneading zone of the twin-screw extruder in the same direction) was too high, and pellet holes, discoloration, and burning occurred in the recycled resin material.
In Comparative Example 3, the resin foam having a gel fraction of 60% or less and having a low gel fraction was merely regenerated, and the resin foam having a high gel fraction could not be regenerated. Moreover, in Comparative Example 3, the barrel temperature (the temperature of the kneading zone of the twin-screw extruder in the same direction) was too high, and the resin recycled material was discolored and burnt.
In Comparative Example 4, the resin foam having a gel fraction of 35% and having a low gel fraction was merely regenerated, and the resin foam having a high gel fraction could not be regenerated.
In Comparative Example 5, since the content of the organic foaming agent was large, the foaming was excessive at the time of 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, a recycled resin material with little resin deterioration could be produced even if a resin foam having a high gel fraction was used.

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

Claims (5)

A coarse pulverization process in which a resin foam of crosslinked polyolefin is coarsely pulverized with a pulverizer,
The coarsely pulverized resin foam is heated and extruded by a single-screw extruder and cut 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 product with a twin-screw extruder in the same direction. The method for producing a recycled resin material according to claim 1, wherein the minimum chip clearance of the same-direction twin-screw extruder is larger than 0.01 mm and 0.2 mm or less. Claimed product having 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 product contains 0.01% by mass or more and 5.0% by mass or less of an organic foaming agent. The reclaimed resin material according to any one of claims 1 to 4, wherein in the melt-kneading step, zinc oxide is added in an amount of 1 part by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the finely pulverized product. Manufacturing method.

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