KR20210098737A - Regeneration method of scrap of polyolefin foam - Google Patents

Abstract

The present invention relates to a method for recycling cross-linked polyolefin foam scraps. The present invention includes the steps of: making pellets; and mixing and using new polyolefin foams. The present invention can increase the reuse rate of polyolefin foam scraps.

Description

REGENERATION METHOD OF SCRAP OF POLYOLEFIN FOAM

The present invention relates to a method of recycling cross-linked polyolefin foam scrap.

Crosslinked polyolefin foams are used in a variety of ways. Shock-absorbing mats, water play equipment, insulation materials for electronic and building products, sound insulation materials, flooring materials for kindergartens, buoy for aquaculture, etc. However, among them, there is a lot of waste and a lot of waste. In particular, EVA foam used for midsole and unitsole for shoes (polyolefin other than EVA is also used a lot) is the one that generates the most waste during manufacturing. In particular, waste generated from sprue and runners and defective products from the EVA injection process, which is the most in the footwear process, is 15-20% of the total, and 10-15% of waste is generated in processes other than injection. This is not only a waste of resources, but also has a great impact on environmental problems and is a factor in the cost increase of products. Numerous studies have been conducted for the regeneration of EVA Foam Scrap generated in this way, and they are as follows.

One. After scraping the scrap with phenol-based antioxidants in an open mill at a high temperature, and then crushing it with the shear force of the open mill to form a sheet, it is mixed and used when manufacturing EVA foam.

2. To make scrap foam powder by pushing scrap between the abrasive slabs rotating in the opposite direction and mixing it to use when manufacturing EVA foam.

3. Put scrap into a specially designed freezing grinder, freeze it at -150°C, grind it to make a powder, and mix and use it when manufacturing EVA Foam.

4. When scrap is put between two rollers with saliva like a hedgehog and turned, the scrap foam is torn and turned into a chip. Select a 3-5mm chip and mix it with cement concrete and use it to manufacture lightweight concrete. However, these methods have significant problems as follows.

That is, the method of 1 above requires a lot of power to regenerate scrap and requires a lot of equipment because of the small processing capacity per machine. It is difficult to exceed a maximum of 10% in the amount of mixing during manufacturing.

In the method of 2 above, EVA Foam Scrap from the recent shoe process has a lot of sprue runners from the injection process, but it is not easy to push it between the abrasive slabs. This is so severe that the working environment is not good and the risk of fire is high due to the generation of heat and static electricity during high-speed rotation of the grinding stone. The regenerated product made in this way is in a powder state, but it cannot be put into the production of new foam as it is (the problem of scattering in the workshop and the problem of dispersion when mixing with the new product, etc.), and the cost is high because it has to be mixed with EVA, etc. to make a master batch. And it is difficult to exceed 10% of the scrap use rate that can be put into new foam in this way.

The method of 3 above is a method commonly used for making pulverized products of rubber tires, but the equipment cost is high. The economic feasibility is low, and the only equipment that is put into practical use is large equipment, so it cannot be used by small-scale shoe manufacturers.

In the method of 4 above, the distance between the scrap generating place and the reclaimed product is long, so the transportation cost is high and the amount of use itself is small, so the scrap consumption is small. It is being treated as a major detriment to the global environment.

An object of the present invention is to provide a method for efficiently recycling cross-linked polyolefin foam scrap.

In order to solve the above problems, the present invention cuts the peroxide cross-linked polyolefin foam scrap to a size of 3 to 30 mm in width x length x height (or diameter, or the length of the largest part of an unspecified shape), then peroxide Mixing with the crosslinkable polyolefin resin, foam / resin = 90/10 ~ 50/50 mixing, pouring the mixture into the hopper of a single screw or twin screw extruder, extruding at a temperature above the DSC Melting Point of the polyolefin resin to make pellets; and

It provides a recycling and use method of cross-linked polyolefin foam scrap comprising the step of using the pellets as a part of the raw material to be mixed and used in the production of a new polyolefin foam.

The peroxide crosslinkable polyolefin may be PE (HDPE, MDPE, LDPE, LLDPE, VLDPE, ULDPE).

or Ethylene Copolymer (EVA, EBA, EMA, EMMA, etc.), Ionomer, Ethylene α-olefin Copolymer (POE, OBC), or Ethylene Propylene Copolymer.

L/D of the single screw or twin screw extruder may be 20-40.

The screw compression ratio of the single-screw or twin-screw extruder (the screw depth of the supply part/the screw depth of the metering part) may be 2.5 to 3.5.

The present invention can increase the reuse rate of polyolefin foam scrap.

In the present invention, after cutting peroxide crosslinked polyolefin foam scrap to a size of 3 to 30 mm in width x length x height (or diameter, or the length of the largest part of an unspecified shape), it is mixed with peroxide crosslinkable polyolefin resin. Foam/resin = 90/10 to 50/50, pouring the mixture into the hopper of a single screw or twin screw extruder, and extruding at a temperature above the DSC Melting Point of the polyolefin resin to make pellets (the first process), and the pellets It provides a method of recycling and using cross-linked polyolefin foam scrap, which includes the step of mixing and using as a part of the raw material to produce a new polyolefin foam (J. process).

The size of 3~30mm: A size of 30mm or more does not fit well into the screw of the extruder and does not go down from the hopper inlet. The size of 3mm or less has low productivity and high cost when pulverizing with a cutter or pulverizer, and even if it is smaller than 3mm, there is no difference in the quality of the regenerated product after extrusion with that of 3mm.

The 90/10 ~ 50/50: If the polyolefin resin is less than 10, pellets are not made, and if it exceeds 50, the shear force in the extruded paper extruder is weakened, so that the quality of the regenerated product is deteriorated and the regeneration cost is high.

At a temperature below the DSC Melting Point, the melt viscosity of the polyolefin is high, and the extrusion speed is lowered, thereby significantly lowering the productivity of the recycled product.

The peroxide crosslinkable polyolefin is PE (HDPE, MDPE, LDPE, LLDPE, VLDPE, ULDPE), Ethylene Copolymer (EVA, EBA, EMA, EMMA, etc.), Ionomer, Ethylene α-olefin Copolymer (POE, OBC), Ethylene Propylene Copolymer can be

L/D of the single screw or twin screw extruder may be 20-40.

If the L/D is 20 or less, the shear force in the cylinder is low, and the melting viscosity of the regenerated product is not sufficiently melted, so there is a problem in the quality of the reclaimed product. Or, it is oxidized and the physical properties are lowered, and in severe cases, it is carbonized.

The screw compression ratio (the screw depth of the supply part / the screw depth of the metering part) of the single-screw or twin-screw extruder may be 2.5 to 3.5.

If the compression ratio is 2.5 or less, the shear force in the cylinder is low, so that the melt viscosity is high because the melting viscosity of the recycled product is high, and the productivity is low. It is changed or oxidized, and the physical properties are deteriorated, and in severe cases, it may be carbonized.

In this way, the rate of use of scrap for new products can be raised to 30%.

<Example>

EVA Midsole Foam

EVA (VA21%, MI 2.5) 100, Steraic Acid 1.0, ZnO 2.0, DCP 0.8, blowing agent ADCA 2.5, TiO2 5.0 were mixed with a kneader and extruded to obtain pellets with a diameter of 4 mm. This pellet was poured into the hopper of the injection molding machine for midsole for shoes, and while the midsole was produced, the sprue runner attached to the midsole injection product was removed to obtain a scrap (hereafter referred to as Scrap-1).

<Comparative Example 1>

The scrap-1 above was pulverized with a plastic crusher to obtain an EVA scrap chip having a diameter of 10 mm. After mixing this Chip 100 and antioxidant BHT 5, it was passed for 10 minutes in an open mill with a surface temperature of 120℃ (mill interval 1mm), and then Sheet-1, a foam scrap sheet with a thickness of 1.5mm, was obtained.

<Comparative Example 2>

After mixing the chip 80, EVA (VA21%, MI 2.5) 20, and antioxidant BHT 5 crushed in <Comparative Example 1>, the mixture was passed through an open mill (1 mm spacing between mills) at a surface temperature of 120° C. for 10 minutes. Sheet-2, a foam scrap sheet of 1.5 mm, was obtained.

<Comparative Example 3>

Powder-1, a scrap foam powder having a particle size of 500 to 700 μm, was obtained by pushing and grinding the scrap-1 above between #100 abrasive slabs rotating in the reverse direction.

<Comparative Example 4>

The scrap-1 above was pulverized in a freeze grinder at -150° C. to obtain Powder-2, a scrap foam powder having a particle size of 300 to 500 μm.

<Comparative Example 5>

The chip pulverized in <Comparative Example 1> was put into the hopper of a co-rotating twin-screw extruder having a screw diameter of 40 mm, L/D of 36, and compression ratio of 2.8, and extruded at a cylinder temperature of 130° C. to obtain a scrap foam powder, powder. As soon as this powder was discharged from the extruder nozzle, it was condensed and became a lump like a bunch of grapes. After cooling this mass, it was crushed again with a plastic crusher to obtain Powder-3 having a particle size of 1.0-1.5m. This Powder-3 had changed color to dark yellow.

<Comparative Example 6>

After mixing the chip 95 and EVA (VA21%, MI 2.5) 5 pulverized in <Comparative Example 1>, the screw diameter is 40 mm, L/D is 36, and the compression ratio is 2.8. When extruded at 130°C, under water pelletizing could not be performed, and powder was obtained by extruding directly from the nozzle. As soon as this powder was discharged from the extruder nozzle, it was condensed and became a lump like a bunch of grapes. After cooling this mass, it was crushed again with a plastic crusher to obtain Powder-4 having a particle size of 1.0-1.5m. This Powder-4 had changed color to pale yellow.

<Example 1>

After mixing the chip 85 crushed in <Comparative Example 1> and EVA (VA21%, MI 2.5) 15, the screw diameter is 40 mm, L/D is 36, and the compression ratio is 2.8. Pellet-1 with a diameter of 4 mm was obtained by extruding at 130° C. and under water pelletizing.

<Example 2>

After mixing the chip 60 and EVA (VA21%, MI 2.5) 40 pulverized in <Comparative Example 1>, the screw diameter is 40mm, L/D is 36, and the compression ratio is 2.8. Pellet-2 with a diameter of 4 mm was obtained by extruding at 130° C. and under water pelletizing.

<Comparative Example 7>

After mixing the chip 40 and EVA (VA21%, MI 2.5) 60 pulverized in <Comparative Example 1>, the screw diameter is 40 mm, L/D is 36, and the compression ratio is 2.8. Pellet-3 with a diameter of 4 mm was obtained by extruding at 130°C and under water pelletizing. This pellet was not completely pulverized, so foam-type scrap particles were mixed inside the pellet, and the pellet shape was not spherical but irregular.

The regenerated products of Comparative Examples and Examples obtained above were mixed with the formulations shown in Tables 1 and 2, and then injected with an Injection EVA Foam Molding machine to produce a shoe midsole and measure physical properties.

EVA Midsole Comparative Example 1-1 Comparative Example 1-2 Comparative Example 2-1 Comparative Example 2-2 Comparative Example 3 Comparative Example 4 EVA (VA21% MI 2.5) 100 90 85 88 85 90 90 Sheet-1 10 15 Sheet-2 12 15 Powder-1 10 Powder-2 10 Powder-3 Powder-4 Pellet-1 Pellet-2 Pellet-3 Stearic Acid 1.0 0.9 0.85 0.904 0.88 0.9 0.9 ZnO 2.0 1.8 1.7 1.808 1.76 1.8 1.8 DCP 0.8 0.72 0.68 0.723 0.704 0.72 0.72 ADCA 2.5 2.5 2.5 2.5 2.5 2.5 2.5 TiO2 5.0 4.5 4.25 4.52 4.4 4.5 4.5 Scrap usage % 10 15 9.6 12 10 10 MI (150℃ 5Kg) g/10min 3.0 1.5 1.0 1.6 1.2 1.4 1.4 Injection availability possible possible impossible possible impossible impossible impossible Hardness Shore C 55 56 57 56 57 57 57 Tensile strength Kg/cm2 25 23 23 23 23 23 23 elongation % 300 250 200 250 200 200 200 product surface appearance Replay Applicability charm charm charm charm charm charm

EVA Midsole Comparative Example 5-1 Comparative Example 5-2 Comparative Example 6-1 Comparative Example 6-2 Example 1 Example 2 Comparative Example 7-1 Comparative Example 7-2 EVA (VA21% MI 2.5) 100 90 80 90 80 70 50 50 70 Sheet-1 Sheet-2 Powder-1 Powder-2 Powder-3 10 20 Powder-4 10 20 Pellet-1 30 Pellet-2 50 Pellet-3 50 30 Stearic Acid 1.0 0.9 0.8 0.905 0.81 0.745 0.7 0.8 0.88 ZnO 2.0 1.8 1.6 1.81 1.62 1.49 1.4 1.6 1.76 DCP 0.8 0.72 0.64 0.724 0.648 0.596 0.56 0.64 0.740 ADCA 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 TiO2 5.0 4.5 4.0 4.525 4.05 3.725 3.5 4.0 4.4 Scrap usage % 10 20 9.5 19 25.5 30 20 12 MI (150℃ 5Kg) g/10min 3.0 2.0 1.5 2.2 1.7 2.2 1.9 1.0 1.4 Injection availability possible possible possible possible possible possible possible impossible impossible Hardness Shore C 55 55 56 55 56 55 55 no form no form Tensile strength Kg/cm2 25 24 24 24 24 25 25 elongation % 300 280 280 280 280 290 290 product surface appearance surface yellowing surface
yellowing slightly
yellowing slightly
yellowing inside the form
bubble foam inside bubble Replay Applicability charm charm charm charm fitness fitness charm charm

Claims (4)

After cutting the peroxide cross-linked polyolefin foam scrap so that the length of any one of the width, length, or height is 3 to 30 mm, it is mixed with peroxide cross-linkable polyolefin resin, foam scrap: resin is 90: 10 to 50: mixing to 50, pouring the mixture into the hopper of a single screw or twin screw extruder and extruding at a temperature higher than the DSC Melting Point of the polyolefin resin to make pellets; and
A recycling and use method of cross-linked polyolefin foam scrap comprising the step of using the pellet as a part of the raw material and mixing and using the new polyolefin foam. According to claim 1,
The peroxide crosslinkable polyolefin is PE (HDPE, MDPE, LDPE, LLDPE, VLDPE, ULDPE), Ethylene Copolymer (EVA, EBA, EMA, EMMA, etc.), Ionomer, Ethylene α-olefin Copolymer (POE, OBC), Ethylene Propylene Copolymer A method of using recycled polyolefin foam scrap that is phosphorus. According to claim 1,
L/D of the single-screw or twin-screw extruder is 20-40 of the recycling method of polyolefin foam scrap. The method of claim 1,
A method of recycling and using polyolefin foam scrap in which the screw compression ratio of the single-screw or twin-screw extruder (the screw depth of the supply part / the screw depth of the metering part) is 2.5 to 3.5.