JP7598293B2 - Recycling method and manufacturing method for laminated sheet for vehicle interior material - Google Patents

Description

The present invention relates to a method for recycling a laminate sheet for vehicle interior materials, which comprises recycling a laminate sheet for vehicle interior materials that contains a thermoplastic resin skin material and a crosslinked resin foam, and obtaining the ground material of the thermoplastic resin skin layer as a recycled material, and a method for producing a laminate sheet for vehicle interior materials that uses the recycled material.

Laminated sheets made by laminating thermoplastic resin skin materials and crosslinked resin foams are widely used for vehicle interior materials such as automobile interior materials, particularly insmelt panels and door panels, due to their good heat resistance, moldability, and cushioning. However, crosslinked resin foams are less likely to melt than thermoplastic resin skin materials, and the crosslinked parts in the crosslinked resin foams become foreign matter, making it difficult to use the laminated sheets as they are as recycled materials. In addition, such laminated sheets usually contain a surface treatment agent layer, and when the laminated sheets are used as recycled materials as they are, the surface treatment agent also becomes foreign matter, which can cause abnormal appearance.

As a method for recycling products containing synthetic resin, Patent Document 1 describes a method of crushing a synthetic resin laminate to separate and separate the synthetic resin skin material and the synthetic resin cushioning material. Patent Document 2 describes a method of leaving an integrated insulator made of a molded product composed of amorphous polyethylene terephthalate and rigid polyurethane foam in a high-temperature atmosphere below the melting point for heat treatment, and then separating the amorphous polyethylene terephthalate and the rigid polyurethane foam.

JP 2000-167832 A Japanese Patent Application Publication No. 9-248869

However, when the methods described in Patent Documents 1 and 2 are used to recycle laminated sheets containing a thermoplastic resin skin material and a cross-linked resin foam used as a vehicle interior material, there is a problem in that the separation of the thermoplastic resin and the cross-linked resin foam is insufficient.

The present invention provides a method for recycling laminate sheets for vehicle interior materials, which can remove cross-linked foamed resin from a laminate sheet containing a thermoplastic resin skin material and a cross-linked resin foam used as a vehicle interior material, efficiently recover the thermoplastic resin as a recyclable material, and reuse it as a thermoplastic resin skin material for the laminate sheet for vehicle interior materials, and a method for manufacturing the laminate sheet for vehicle interior materials.

The present invention relates to a method for recycling a laminate sheet for vehicle interior materials, which includes a thermoplastic resin skin material and a crosslinked resin foam disposed on a first surface of the thermoplastic resin skin material, the method comprising the steps of: heating a waste laminate sheet; crushing the heated laminate sheet waste with an impact crusher; separating the crushed laminate sheet waste by air separation into a recycled material, which is a crushed thermoplastic resin skin material, and a foreign matter including a crushed crosslinked resin foam; and melt-kneading and molding a recycled resin composition containing the recycled material obtained through the separation step to obtain a recycled sheet, wherein in the heating step, the laminate sheet waste is heated to a temperature 25° C. or higher than the lowest melting point Tmin of the thermoplastic resin skin material, and in the crushing step, a relationship coefficient between the rotation speed R (rpm) of the impact crusher and the mesh opening S (m), which is expressed by the following mathematical formula (1), is 0.500 rpm·m2 ^{or higher} and 2.650 rpm·m2 or higher. The present invention relates to a method for recycling a laminated sheet for vehicle interior materials, the method being characterized in that the ^above range is satisfied.

The present invention also relates to a method for producing a laminate sheet for vehicle interior materials, which is characterized by using a recycled sheet obtained by the above-mentioned method for recycling vehicle interior materials.

According to the method for recycling a laminate sheet for vehicle interior materials of the present invention, the cross-linked foamed resin component can be effectively removed from a laminate sheet containing a thermoplastic resin skin material and a cross-linked resin foam, and the thermoplastic resin component can be efficiently recovered as a recycled material and reused as the thermoplastic resin skin material of the laminate sheet for vehicle interior materials.
Furthermore, according to the method for producing a laminate sheet for vehicle interior materials of the present invention, it is possible to provide a laminate sheet for vehicle interior materials using a thermoplastic resin component recovered as a recycled material.

The inventors of the present invention conducted intensive research to solve the above-mentioned problems. As a result, they discovered that by heating a waste laminate sheet containing a thermoplastic resin skin material and a cross-linked resin foam placed on the first surface of the thermoplastic resin skin material at a predetermined temperature, then crushing it in an impact crusher under conditions where the relationship coefficient between the rotation speed R (rpm) and the screen opening S (m) satisfies a predetermined range, and then sorting the crushed waste laminate sheet by air separation, it is possible to effectively remove foreign matter such as cross-linked foam resin components and efficiently recover the thermoplastic resin components as recycled materials.

(Method of recycling laminated sheets for vehicle interior materials)
First, in a heating step, a waste laminate sheet for vehicle interior materials containing a thermoplastic resin skin material and a crosslinked resin foam is heated. In the laminate sheet, a crosslinked resin foam (crosslinked resin foam layer) is laminated on a first surface of a thermoplastic resin skin material (thermoplastic resin skin layer). In the heating step, the waste laminate sheet is heated to a temperature 25°C higher than the lowest melting point Tmin of the thermoplastic resin skin material, that is, to a temperature of "Tmin + 25°C" or higher. This softens the thermoplastic resin skin material, and then the waste laminate sheet is crushed and separated by air force, so that the crushed thermoplastic resin skin material can be easily separated from the crushed crosslinked resin foam. The heating temperature is preferably [Tmin + 30°C] or higher, more preferably [Tmin + 35°C] or higher, and particularly preferably [Tmin + 40°C] or higher. The upper limit of the heating temperature is not particularly limited as long as it is lower than the temperature at which the thermoplastic resin decomposes. For example, from the viewpoints of resin deterioration and processability, the upper limit may be 250° C. or lower, or may be 200° C. or lower.

The lowest melting point Tmin of a thermoplastic resin skin material can be confirmed by performing differential scanning calorimetry (DSC) using a waste material of a thermoplastic resin skin material or a laminate sheet. Specifically, the lowest melting point Tmin of a thermoplastic resin skin material can be confirmed by determining the value of the minimum melting peak in the DSC curve obtained by heating 8 mg (5-15 mg) of skin material or 8 mg (5-15 mg) of waste material of a laminate sheet at a heating rate of 10°C/min from 40°C to 200°C (first heating) to melt it, then cooling it at a heating rate of 10°C/min from 200°C to 40°C to crystallize it, and then heating it at a heating rate of 10°C/min from 40°C to 200°C (second heating) at a heating rate of 10°C/min to obtain all of the DSC curves (first heating → cooling → second heating) obtained by the second heating.

In the heating step, the heating time is not particularly limited, but may be, for example, from the viewpoint of suppressing resin deterioration and processability, from 10 seconds to 5 minutes or from 20 seconds to 3 minutes.

The thermoplastic resin constituting the thermoplastic resin skin material is not particularly limited, and examples thereof include polyolefin-based resins, vinyl chloride-based resins, and olefin-based thermoplastic elastomers. From the viewpoint of excellent separability from crosslinked resin foams and suitable use as a recyclable material in the skin layer of a laminate sheet for vehicle interior materials, it is preferable that the thermoplastic resin skin material contains one or more selected from the group consisting of olefin-based thermoplastic elastomers and polyolefin-based resins. From the viewpoint of excellent rubber elasticity at high temperatures and during long-term deformation and high heat resistance, it is more preferable that the thermoplastic resin skin material contains an olefin-based thermoplastic elastomer, and it is even more preferable that the thermoplastic resin skin material contains an olefin-based thermoplastic elastomer and a polyolefin-based resin. When the thermoplastic resin skin material contains one or more selected from the group consisting of olefin-based thermoplastic elastomers and polyolefin-based resins, the heating temperature is preferably 135°C or more and 250°C or less, more preferably 140°C or more and 230°C or less, and particularly preferably 150°C or more and 195°C or less.

The olefin-based thermoplastic elastomer is not particularly limited and may be any of a blend type, a polymerization type (also called reactor TPO), and a dynamic crosslinking type (also called TPV). The olefin-based thermoplastic elastomer may be used alone or in combination of two or more types. From the viewpoint of cost and performance, it is preferable to use a combination of a polymerization type and a dynamic crosslinking type.

The polyolefin resin is not particularly limited as long as it is an olefin polymer. For example, it may be a homopolymer of an olefin such as ethylene, propylene, 1-butene, isobutene, or 4-methyl-1-pentene, a copolymer of two or more olefins, or a copolymer of an olefin and another monomer. The copolymer may be a random copolymer or a block copolymer. The copolymer may be a terpolymer. In a copolymer of an olefin and another monomer, it is desirable that the olefin is 50% by weight or more. Examples of the other monomer include dienes, cyclopentadiene, and vinyl compounds. Specific examples include homopolypropylene, ethylene-propylene copolymer, random polypropylene (hereinafter also referred to as R-PP), block polypropylene, ethylene-1-butene copolymer, high density polyethylene, low density polyethylene, and linear low density polyethylene (hereinafter also referred to as LLDPE). The polyolefin resin may be used alone or in combination of two or more types.

The crosslinked resin foam is not particularly limited, but is preferably a crosslinked polyolefin resin foam from the viewpoint of excellent separability from the thermoplastic resin skin material. The crosslinked polyolefin resin foam is not particularly limited, and may be one in which a polyolefin resin is crosslinked by a conventionally known method and then foamed. The polyolefin resin may be any of those described above.

The thermoplastic resin skin material and the cross-linked resin foam may be directly bonded by heating the surfaces to be bonded to a surface temperature of 120°C or higher and 200°C or higher, or may be bonded via an adhesive. When the thermoplastic resin skin material contains one or more selected from the group consisting of an olefin-based thermoplastic elastomer and a polyolefin-based resin, and the cross-linked resin foam is formed of a cross-linked polyolefin-based resin foam, they can be directly bonded.

The laminated sheet may further include a surface treatment agent layer. The surface treatment agent constituting the surface treatment agent layer is not particularly limited, and may be, for example, a water-based urethane paint, a solvent-based urethane paint, or the like, or may be silicone, silicone beads, urethane beads, or the like. When the thermoplastic resin skin material contains one or more selected from the group consisting of an olefin-based thermoplastic elastomer and a polyolefin-based resin, the surface treatment agent layer is often included from the viewpoint of scratch resistance, abrasion resistance, and the like. The surface treatment agent layer may be disposed on the second surface opposite to the first surface of the thermoplastic resin skin material, and may be bonded to the thermoplastic resin skin material via a primer. According to the recycling method of the present invention, the surface treatment agent layer can be effectively removed from the thermoplastic resin skin material.

The laminated sheet scrap may be waste generated during the manufacture of vehicle interior materials, or may be scrap collected from used vehicle interior materials. The laminated sheet scrap may be cut to a size of 5 cm to 30 cm using, for example, a cutting machine or a punching machine, as necessary. Here, the size of the laminated sheet scrap means the maximum length of the laminated sheet scrap.

但し、前記数式（１）において、Ｒ（ｒｐｍ）は衝撃粉砕機の回転数を示し、Ｓ（ｍ）は衝撃粉砕機のスクリーンの目開きサイズを示す。 Next, in the crushing step, the heated laminated sheet waste material is crushed by an impact crusher. In the crushing step, the relationship coefficient between the rotation speed R (rpm) of the impact crusher and the screen opening S (m) expressed by the following mathematical formula (1) satisfies the range of 0.500 rpm· ^m2 to 2.650 rpm· ^m2 . In the following explanation, the unit of the relationship coefficient is omitted.

In the above formula (1), R (rpm) represents the rotation speed of the impact crusher, and S (m) represents the mesh size of the screen of the impact crusher.

The relationship coefficient affects the crushing ability (processability) and the quality of the recycled material. If the relationship coefficient is less than 0.500, the separation of the thermoplastic resin skin material from foreign matter other than the thermoplastic resin skin material, such as the crosslinked resin foam and the surface treatment agent layer, becomes insufficient, and the quality of the recycled material becomes poor. In addition, the screen passability of the crushed material decreases, and the crushing ability decreases significantly. On the other hand, if the relationship coefficient exceeds 2.650, the separation of the thermoplastic resin skin material as the recycled material from foreign matter other than the thermoplastic resin skin material, such as the crosslinked resin foam and the surface treatment agent layer, becomes insufficient, and the quality of the recycled material becomes poor. The relationship coefficient is preferably 0.550 or more and 2.500 or less, and more preferably 0.550 or more and 2.000 or less.

The impact crusher is not particularly limited as long as it can crush the object by impact. For example, a crusher can be used that rotates a rotor at high speed to obtain an impact force and crushes the object with a hammer (rotary blade) attached to the rotor. From the viewpoint of efficiently crushing the laminated sheet waste material with a large impact force and separating the crosslinked resin foam and the surface treatment agent, it is preferable that the impact crusher be a swing hammer crusher type.

It is desirable to crush the laminated sheet waste into pieces having a size of 1 mm to 80 mm, and more desirably, 3 mm to 40 mm. Here, the size of the crushed pieces means the maximum length of the crushed pieces. If the size of the crushed pieces is within the above-mentioned range, foreign matter such as the crosslinked resin foam and the surface treatment agent layer is easily peeled off from the thermoplastic resin skin material. The size of the crushed pieces can be adjusted by the size of the screen openings of the impact crusher, etc.

The size of the openings in the screen of the impact crusher is preferably 0.015 m or more and 0.030 m or less, and more preferably 0.015 m or more and 0.025 m or less, from the viewpoint of easily crushing the waste laminated sheet to the above-mentioned size, within the range that satisfies the above-mentioned relationship coefficient. The shape of the openings in the screen is not particularly limited, and may be circular, elliptical, rectangular, or other shapes. Here, the size of the openings in the screen means the diameter when the opening shape is circular, and means the maximum length when the opening shape is other than the above.

The rotation speed of the impact crusher is not particularly limited as long as it satisfies the above-mentioned relationship coefficient, but from the viewpoint of efficiently peeling off and crushing foreign matter such as crosslinked resin foam and surface treatment agent layer from the thermoplastic resin skin material, for example, it may be 2500 rpm or more and 4500 rpm or less, or 2500 rpm or more and 4000 rpm or less.

Next, in a separation step, the crushed laminate sheet waste is separated by wind separation into recycled material, which is a crushed thermoplastic resin skin material, and foreign matter including crushed crosslinked resin foam, and the recycled material is recovered. Wind separation is not particularly limited, and can be performed, for example, using a wind sorter (also called a wind classifier). The air volume of the blower that transports the crushed laminate sheet waste to the wind sorter is not particularly limited, and may be, for example, 5 ^m3 /min or more and 100 ^m3 /min or less. The wind speed of the wind sorter is not particularly limited, and may be, for example, 5 m/sec or more and 30 m/sec or less.

In the separation process, it is preferable to sieve the recycled material recovered after wind separation using a vibrating screen to further remove foreign matter such as crushed crosslinked resin foam that adheres to the surface of the recycled material. The mesh size of the vibrating screen is preferably the same as the mesh size of the screen of the impact crusher, for example.

By using a wind sorting machine equipped with an air separator and a vibrating screen, wind separation and sieving can be performed.

From the viewpoint of recyclability and surface smoothness of the recycled sheet, the recycled material preferably has a foreign matter remaining rate of 0.10% by weight or less, more preferably 0.090% by weight or less, even more preferably 0.080% by weight or less, even more preferably 0.070% by weight or less, and particularly preferably 0.060% by weight or less. The lower limit of the foreign matter remaining rate of the recycled material is better as it is closer to 0% by weight, and may be, for example, 0.001% by weight or more.

From the viewpoint of recyclability and the surface beauty of the recycled sheet, the recycled material preferably has a foreign matter adhesion number rate of 8.0% or less, more preferably 7.0% or less, even more preferably 6.0% or less, and particularly preferably 5.0% or less. The closer to 0% the foreign matter adhesion number rate of the recycled material is, the better, and it may be, for example, 0.010% or more.

The residual foreign matter rate and the rate of foreign matter particles attached to the recycled material can be measured as follows.
(1) Approximately 100 g of recycled material is randomly collected as a sample, and the weight of the sample is accurately measured to three decimal places using an electronic balance and designated as W0. The total number of crushed pieces contained in the sample is also measured and designated as N0. If the weight of the recycled material is less than 100 g, all of the recycled material is used as the sample.
(2) Observe the appearance of each pulverized particle in the sample and select any pulverized particles that have foreign matter attached.
(3) The number of crushed pieces having the selected foreign matter attached thereto is counted and designated as N1.
(4) Any foreign matter adhering to the crushed material is removed with a file, and the weight of the sample after the foreign matter has been removed is measured accurately to three decimal places on an electronic balance and recorded as W1.
(5) The residual foreign matter rate of the recycled material is calculated using the following formula (2).
Foreign matter remaining rate of recycled material (weight%) = (W0 - W1) / W0 x 100 (2)
(6) The rate of foreign matter particles adhering to the recycled material is calculated using the following formula (3).
Rate of foreign matter adhesion in recycled materials (%) = N1/N0 x 100 (3)

From the viewpoint of the surface smoothness and surface beauty of the recycled sheet, the recycled material preferably has a coating thickness without residual foreign matter of 25 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less.

Next, in the sheet forming process, the recycled resin composition containing the recycled material obtained through the separation process is melted and kneaded, and formed to obtain a recycled sheet. From the viewpoint of recyclability and physical properties of the recycled sheet, the recycled resin composition preferably contains 1% by weight to 60% by weight of the recycled material and 40% by weight to 99% by weight of unused (virgin) thermoplastic resin having the same composition as the recycled material, more preferably contains 5% by weight to 60% by weight of the recycled material and 40% by weight to 95% by weight of unused (virgin) thermoplastic resin having the same composition as the recycled material, even more preferably contains 20% by weight to 60% by weight of the recycled material and 40% by weight to 80% by weight of unused (virgin) thermoplastic resin having the same composition as the recycled material, and particularly preferably contains 30% by weight to 60% by weight of the recycled material and 40% by weight to 70% by weight of unused (virgin) thermoplastic resin having the same composition as the recycled material.

The recycled resin composition may contain one or more additives such as softeners, inorganic fillers, antioxidants, light stabilizers, UV absorbers, antistatic agents, lubricants, and colorants, as necessary. The content of the additives may be, for example, 0.1% by weight or less.

The sheet molding is not particularly limited, and may be calendar molding or extrusion molding. The thickness of the recycled sheet is not particularly limited, and may be set appropriately as needed. The thickness of the recycled sheet may be, for example, 300 μm or more and 1500 μm or less.

(Method for producing laminated sheet for vehicle interior materials)
The laminate sheet for vehicle interior materials can be produced by the same method as known methods, except that a recycled sheet obtained by the above-mentioned method for recycling vehicle interior materials is used.
A laminate sheet for vehicle interior materials can be obtained by laminating a recycled sheet obtained by calendar molding or extrusion molding on the surface of a crosslinked resin foam (crosslinked resin foam layer) by a method of thermal lamination to form a thermoplastic resin skin layer. Alternatively, a laminate sheet for vehicle interior materials can be obtained by bonding a recycled sheet obtained by calendar molding or extrusion molding to the surface of a crosslinked resin foam (crosslinked resin foam layer) using an adhesive such as a two-component curing adhesive.
A laminate sheet for vehicle interior materials may be obtained by a method (calendar topping method) in which a recycled resin composition containing a molten recycled material rolled by a calendar roll or a recycled material and an unused (virgin) thermoplastic resin having the same composition as the recycled material is topped on the surface of a crosslinked resin foam to form a recycled sheet (thermoplastic resin skin layer). Alternatively, a laminate sheet for vehicle interior materials may be obtained by extruding a molten recycled material or a recycled resin composition containing a molten recycled material and an unused (virgin) thermoplastic resin having the same composition as the recycled material from a T-die of an extruder onto the surface of a crosslinked resin foam to form a recycled sheet (thermoplastic resin skin layer).

From the viewpoint of excellent rubber elasticity at high temperatures and long-term deformation and high heat resistance, the recycled sheet is preferably made of a recycled material derived from a thermoplastic resin skin material containing an olefin-based thermoplastic elastomer, and more preferably made of a recycled material derived from a thermoplastic resin skin material containing an olefin-based thermoplastic elastomer and a polyolefin-based resin. Examples of the olefin-based thermoplastic elastomer and the polyolefin-based resin include those described above.

The crosslinked resin foam is not particularly limited, but is preferably a crosslinked polyolefin resin foam. The crosslinked polyolefin resin foam is not particularly limited, and can be obtained by crosslinking a polyolefin resin by a conventionally known method and then foaming. As the polyolefin resin, the above-mentioned resins can be used as appropriate. The method for forming the crosslinked structure is not particularly limited, and examples thereof include a method of irradiating ionizing radiation such as α rays, β rays, γ rays, and electron beams, a method of irradiating ultraviolet rays, and a method using a crosslinking agent such as an organic peroxide and a silane compound. The foaming method is not particularly limited, and examples thereof include extrusion foaming, in-mold foaming, atmospheric foaming, and chemical reaction foaming. Examples of the foaming agent that can be used include inorganic gases, hydrocarbons or halogenated hydrocarbons having a boiling point of -50 to 120°C, water, and thermal decomposition type foaming agents.

The crosslinked resin foam is not particularly limited, but may have a degree of crosslinking of 30% to 65% or 40% to 55% from the viewpoint of moldability. The degree of crosslinking of the crosslinked resin foam can be measured, for example, by the rate of weight loss after dissolving the non-crosslinked portion using an organic solvent.

The crosslinked resin foam is not particularly limited, but from the viewpoint of flexibility and cushioning, the expansion ratio may be, for example, from 10 to 40. The expansion ratio of the crosslinked resin foam can be calculated, for example, by measuring the specific volumes (unit: ^cm3 /g) of the expandable resin sheet before foaming and the crosslinked resin foam sheet, and calculating the specific volume of the crosslinked resin foam sheet/the specific volume of the expandable resin sheet before foaming.

The crosslinked resin foam may contain additives such as foaming aids, softeners, lubricants, antioxidants, antistatic agents, flame retardants, UV absorbers, light stabilizers, colorants, and inorganic fillers, as necessary.

The laminated sheet for vehicle interior materials may further include a surface treatment agent layer. The surface treatment agent constituting the surface treatment agent layer is not particularly limited, and examples thereof include water-based urethane paint and solvent-based urethane paint. When the thermoplastic resin skin layer includes one or more selected from the group consisting of olefin-based thermoplastic elastomers and polyolefin-based resins, it is preferable to include a surface treatment agent layer from the viewpoint of scratch resistance, abrasion resistance, etc. The surface treatment agent layer is disposed on the second surface opposite to the first surface on which the crosslinked resin foam of the thermoplastic resin skin material is disposed, and may be bonded to the thermoplastic resin skin material via a primer. This improves the scratch resistance and abrasion resistance of the thermoplastic resin skin material.

The laminated sheet for vehicle interior materials is not particularly limited, but can be suitably used as vehicle interior materials such as instrument panels, door trims, trunk trims, seats, pillar covers, ceiling materials, rear trays, console boxes, airbag covers, arm rests, head rests, meter covers, and crash pads for automobiles and other vehicles.

The present invention will be described in more detail below using examples. Note that the present invention is not limited to the following examples.

(Laminated sheet waste)
Skin material: 40% by weight of dynamically crosslinked olefin-based thermoplastic elastomer (Milastomer (registered trademark) "8030NHS" manufactured by Mitsui Chemicals, Inc.), 50% by weight of polymerization type olefin-based thermoplastic elastomer ("R-110E" manufactured by Prime Polymer Co., Ltd.), 10% by mass of random polypropylene ("B-221WA" manufactured by Prime Polymer Co., Ltd.), 0.65 parts by weight in total of lubricant, antioxidant and ultraviolet absorber as additives per 100 parts by weight of resin, thickness 500 μm
Cross-linked resin foam: Cross-linked polyolefin resin foam (Toray Industries, Inc. "JP17-15025"), cross-linking degree: 43%, expansion ratio: 15 times, thickness: 2.5 mm)
Surface treatment layer: urethane paint (Dainichiseika Color & Chemicals "Lezaroid LU-855SP"), thickness 6 μm
In the laminated sheet, a crosslinked resin foam is laminated on one surface of a skin material and directly bonded to the skin material, and a surface treatment agent layer is laminated and bonded to the other surface of the skin material via a one-liquid primer ("Leatheroid LU-236" manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd. The laminated sheet was trimmed to form an automobile door trim, and the remaining waste material was collected.

The Tmin of the above skin material was confirmed by using a differential scanning calorimeter (Shimadzu Corporation's "DSC-60Plus") to melt 8 g of the skin material by heating it from 40°C to 200°C at a heating rate of 10°C/min (first heating), then crystallizing it by cooling it from 200°C to 40°C at a heating rate of 10°C/min, and then heating it from 40°C to 200°C at a heating rate of 10°C/min (second heating). The Tmin was confirmed by determining the value of the minimum melting peak in the DSC curve obtained in the second heating, which was 110.6°C.

Example 1
The laminated sheet waste was cut with a blade into pieces approximately 5 cm square (approximately 25 ^cm2 ), heated to 140°C with an infrared heater, and left at 140°C for 5 seconds, after which it was impact crushed using an impact crusher (Makino Sangyo Co., Ltd., Sling Hammer Crusher, model "HC-20") under the conditions of rotation speed and screen opening size shown in Table 1 below. In the impact crusher, the shape of the screen openings was circular. The rotation speed of the impact crusher was determined by the current value.
The crushed material was then sent to a Horai AS separator (pre-air separator, main separator, vibrating screen) using a Horai DF type fan (DF-1: 0.75 kW, 2 P, air volume: 6.5 ^m3 /min, static air pressure: 2 MPa), where the recycled material was separated from the crosslinked resin foam and surface treatment agent layer at a wind speed of 10 to 15 m/sec, and the recycled material was recovered. In the AS separator, the openings in the vibrating screen were circular and had a size (diameter) of 30 mm.
50 g of the recycled material was melt-kneaded at 180° C. for 5 minutes in a test roll to prepare a recycled sheet having a thickness of about 500 μm.

(Examples 2 to 4)
Recycled materials were recovered and recycled sheets were produced in the same manner as in Example 1, except that the cut size of the waste laminated sheet, the heating temperature, and the impact crushing conditions were as shown in Table 1 below.

(Examples 5 to 7)
An impact crusher manufactured by Onoue Machinery Co., Ltd. (Sling Hammer Crusher, model "WALD-15") was used to recover recycled materials and produce recycled sheets in the same manner as in Example 1, except that the cut size of the waste laminated sheet and the heating and impact crushing conditions were as shown in Table 1 below.

(Comparative Example 1)
The recycled material was recovered and a recycled sheet was produced in the same manner as in Example 1, except that the cut waste laminated sheet was crushed in an impact crusher without heating.

(Comparative Example 2)
The recycled material was recovered and a recycled sheet was produced in the same manner as in Example 1, except that the cut laminated sheet waste was cut into pieces approximately 15 cm square (approximately 225 ^cm2 ), the cut laminated sheet waste was not heated, and the impact crushing conditions were set forth in Table 2 below.

(Comparative Examples 3 to 5)
The recycled material was recovered and a recycled sheet was produced in the same manner as in Example 1, except that the heating temperature was set as shown in Table 2 below.

(Comparative Examples 6 and 7)
The recycled material was recovered and a recycled sheet was produced in the same manner as in Example 1, except that the cut size of the waste laminated sheet, the heating temperature, and the impact crushing conditions were as shown in Table 2 below.

(Comparative Example 8)
The cut size of the laminated sheet waste material and the impact crushing conditions were as shown in Table 2 below, and the recycled material was recovered and a recycled sheet was produced in the same manner as in Example 1, except that air separation was not performed.
The recycled material contained crushed crosslinked resin foam.

(Comparative Example 9)
The laminated sheet waste was cut into pieces approximately 15 cm square (approximately 225 ^cm2 ), heated to 160°C with an infrared heater, and left at 160°C for 5 seconds, after which it was shear-pulverized using a shear crusher (HORAI Corporation's "BO-480") under the conditions of rotation speed and screen opening size shown in Table 1 below. In the shear crusher, the shape of the screen openings was circular. The rotation speed of the shear crusher was determined by the current value.
Thereafter, in the same manner as in Example 1, the recycled material was separated from the crosslinked resin foam and the surface treatment agent layer by air separation, the recycled material was recovered, and a recycled sheet was produced.

In Examples 1 to 7 and Comparative Examples 1 to 7 and 9, the correlation coefficient between the rotation speed R (rpm) of the crusher and the screen opening S (m) shown in the following formula 1 was calculated, and the results are shown in Tables 1 and 2 below.

In Examples 1 to 7 and Comparative Examples 1 to 7 and 9, the foreign matter remaining rate and the rate of foreign matter adhesion in the recycled materials were measured as follows. In addition, the thickness of the coating film with remaining foreign matter in the recycled materials was observed and evaluated as follows. The results are shown in Tables 1 and 2 below. In addition, the appearance of the recycled sheets was observed and evaluated as follows, and the results are shown in Tables 1 and 2 below.

(Foreign matter remaining rate and rate of foreign matter adhesion)
(1) Approximately 100 g of recycled material was randomly collected as a sample, and the weight of the sample was accurately measured to three decimal places using an electronic balance and designated as W0. In addition, the total number of crushed pieces contained in the sample was measured and designated as N0.
(2) The appearance of each pulverized particle in the sample was observed, and pulverized particles with foreign matter attached were selected.
(3) The number of crushed pieces having foreign matter attached thereto was counted and designated as N1.
(4) Any foreign matter adhering to the crushed product was removed with a file, and the weight of the sample after the foreign matter was removed was measured accurately to three decimal places on an electronic balance and recorded as W1.
(5) The residual foreign matter rate of the recycled material was calculated using the following formula (2).
Foreign matter remaining rate of recycled material (weight%) = (W0 - W1) / W0 x 100 (2)
(6) The rate of foreign matter particles adhering to the recycled material was calculated using the following formula (3).
Rate of foreign matter adhesion in recycled materials (%) = N1/N0 x 100 (3)

(Foreign matter remaining coating thickness)
The crushed material with foreign matter attached that was selected when measuring the foreign matter remaining rate and the foreign matter attached number rate was cut perpendicular to the foreign matter with a sharp blade, and the cross section with the foreign matter attached was observed at 300 times magnification (detection limit: 0.01 μm) with a One Shot VR-5000 manufactured by Keyence Corporation, and the foreign matter attached to the surface of the recycled material was detected, and the thickness of the coating film with the remaining foreign matter was confirmed using the scale measurement system built into the device.

(Appearance of the recycled sheet)
The surface of the recycled sheet was observed at 20 times magnification with a magnifying glass, and the appearance was evaluated according to the following 5-level scale: In the following, size refers to the maximum length of the convex portion and/or concave portion on the sheet surface.
1: The sheet surface is almost completely uneven, and is in good condition. 2: The sheet surface has small irregularities (size 1 mm or less) scattered over it. 3: The sheet surface has a small amount of obvious irregularities (size over 1 mm), and the appearance is somewhat poor. 4: The sheet surface has many obvious irregularities (size over 1 mm), and the appearance is poor. 5: The melted and kneaded recycled material sticks to the test roll, and it is impossible to form a sheet.

As can be seen from Table 1, in the examples, the cross-linked foamed resin component was effectively removed from the laminate sheet containing a thermoplastic resin skin material and a cross-linked resin foam, and the thermoplastic resin component was efficiently recovered as a recycled material and reused as a thermoplastic resin skin material for the laminate sheet for vehicle interior materials.
On the other hand, as can be seen from Table 2, in Comparative Examples 1 to 5 in which the waste laminate sheet was not heated or the heating temperature was low, foreign matter containing the cross-linked foamed resin component could not be effectively removed from the laminate sheet, and the foreign matter remaining rate and/or the number of foreign matter attachment rates were high. In addition, in Comparative Example 6 in which the correlation coefficient was low or Comparative Example 7 in which the correlation coefficient was high, foreign matter containing the cross-linked foamed resin component could not be effectively removed from the laminate sheet, and the foreign matter remaining rate and/or the number of foreign matter attachment rates were high. In Comparative Example 8 in which air separation was not performed, the cross-linked foamed resin component could not be removed. In Comparative Example 9 in which shear crushing was performed instead of impact crushing, foreign matter containing the cross-linked foamed resin component could not be effectively removed from the laminate sheet, and the foreign matter remaining rate and the number of foreign matter attachment rates were high.

Claims (9)

A method for recycling a laminate sheet for vehicle interior materials, comprising: a thermoplastic resin skin material; and a crosslinked resin foam disposed on a first surface of the thermoplastic resin skin material, the method comprising the steps of:
heating the waste laminated sheet;
a crushing step of crushing the heated waste laminated sheet using an impact crusher;
a separation step of separating the crushed laminate sheet waste material into a recycled material, which is a crushed thermoplastic resin skin material, and a foreign matter, which includes a crushed crosslinked resin foam, by wind separation; and a sheet molding step of melt-kneading and molding a recycled resin composition containing the recycled material obtained through the separation step to obtain a recycled sheet,
In the heating step, the waste laminate sheet is heated to a temperature 25° C. or more higher than the lowest melting point Tmin of the thermoplastic resin skin material,
a coefficient of relationship between the rotation speed R (rpm) of the impact crusher and the mesh size S (m) of the screen, as expressed by the following mathematical formula (1), is in the range of 0.500 rpm· ^m2 or more and 2.650 rpm·m2 or ^less , in the crushing step.

The method for recycling laminated sheets for vehicle interior materials according to claim 1, wherein the laminated sheets include a surface treatment agent layer, and in the separation step, the crushed waste laminated sheets are separated by wind separation into recycled material, which is crushed thermoplastic resin skin material, and foreign matter, which includes crosslinked resin foam and crushed surface treatment agent layer. The method for recycling a laminated sheet for vehicle interior materials according to claim 1 or 2, wherein the recycled material has a foreign matter remaining rate of 0.10% by weight or less and a foreign matter adhesion number rate of 8.0% or less. The method for recycling a laminate sheet for vehicle interior materials according to any one of claims 1 to 3, wherein the thickness of the coating film remaining on the recycled material is 25 μm or less. The method for recycling a laminate sheet for vehicle interior materials according to any one of claims 1 to 4, wherein the thermoplastic resin skin material contains one or more selected from the group consisting of olefin-based thermoplastic elastomers and polyolefin-based resins. The method for recycling a laminated sheet for vehicle interior materials according to any one of claims 1 to 5, wherein the crosslinked resin foam is formed of a crosslinked polyolefin-based resin foam. The method for recycling a laminate sheet for vehicle interior materials according to any one of claims 1 to 6, wherein the recycled resin composition contains 1% by weight or more and 60% by weight or less of the recycled material, and 40% by weight or more and 99% by weight or less of virgin thermoplastic resin having the same composition as the recycled material. A method for manufacturing a laminated sheet for vehicle interior materials, characterized in that a recycled sheet obtained by the vehicle interior material recycling method described in any one of claims 1 to 7 is used. The method for producing a laminate sheet for vehicle interior materials according to claim 8, wherein the recycled sheet is used to form a thermoplastic resin skin layer, to obtain a laminate sheet including a surface treatment agent layer, a thermoplastic resin skin layer, and a crosslinked resin foam.