Decrosslinked eva resin, composition comprising same, and method for recycling crosslinked eva molded article

Abstract

Disclosed is a decrosslinked EVA resin having a gel fraction of 40 wt% or less and an elongation of 200% or more. According to the present invention, it is possible to manufacture a high-quality EVA product that is reprocessable and has a low gel fraction, a high elongation, and a high VA content. In particular, when a sub- or supercritical fluid is used, the amount of by-products generated during decrosslinking is reduced, and thus the color of the product may be improved.

Description

Decrosslinked EVA resin, a composition containing the same, and a method for recycling a crosslinked EVA molded body

[0001] The present invention relates to a decrosslinked EVA resin, a composition containing the same, and a method for recycling a crosslinked EVA molded body. More specifically, the present invention relates to a decrosslinked EVA resin that can produce a high-quality EVA product with a low gel fraction and high elongation, a high VA content, and reprocessability by decrosslinking crosslinked EVA, a composition containing the same, and a method for recycling a crosslinked EVA molded body with improved color.

[0002] When cross-linked EVA molded bodies are de-crosslinked and recycled, waste is reduced and costs are lowered by reusing raw materials, and they can be utilized to manufacture various products by improving processability and flexibility.

[0003] Methods for recycling cross-linked EVA molded articles include using them as low-quality fillers by crushing, or completely decomposing the cross-linked polymer through reactions such as pyrolysis and hydrolysis and then repolymerizing them for use.

[0004] When manufacturing EVA foam by crushing and recycling existing cross-linked EVA molded bodies, particularly cross-linked EVA foams, the recycled material of the EVA molded body can be added up to a maximum of 10 wt% to 15 wt% of the total weight. If added in excess of this range, it acts as a defect in the foaming process and causes a rapid deterioration in mechanical properties. In addition, if the crushed EVA foam is used as a filler rather than in the foaming process, there is a disadvantage that it can only be used as a low-grade product.

[0005] On the other hand, the method of completely decomposing and recycling cross-linked EVA molded bodies has the disadvantage of entailing high energy and investment costs.

[0006] Therefore, a recycling method for cross-linked EVA molded articles that enables energy savings and is simple is required. In addition, it is necessary to develop a decross-linked EVA resin that allows for the manufacture of EVA molded articles even with a high content of recycled material, and has a low gel fraction and excellent elongation.

[0007] Related prior art is Korean Patent Publication No. 10-2024-0107730.

[0008] The objective of the present invention is to provide a decrosslinked EVA resin having a low gel fraction, high elongation, and high VA content by decrosslinking crosslinked EVA, a composition containing the same, and a method for recycling a crosslinked EVA molded body.

[0009] Another objective of the present invention is to provide a decrosslinked EVA resin capable of producing high-quality EVA products that can be reprocessed, a composition comprising the same, and a method for recycling a crosslinked EVA molded body.

[0010] Another objective of the present invention is to provide a decrosslinked EVA resin with improved color and reduced by-products generated during decrosslinking when a sub- or supercritical fluid is used, a composition containing the same, and a method for recycling a crosslinked EVA molded body.

[0011] Another objective of the present invention is to provide a decrosslinked EVA resin that enables high-quality recycling compared to conventional crushed material recycling, is simpler than a complete decomposition process, and saves energy.

[0012] The above and other objectives of the present invention can all be achieved by the present invention described below.

[0013] 1. One aspect of the present invention relates to a decrosslinked EVA resin. The decrosslinked EVA resin has a gel fraction of 40 wt% or less and an elongation of 200% or more.

[0014] 2. In the above embodiment 1, the decrosslinked EVA resin may have a content of 3 wt% or more of VA (vinyl acetate) defined by the following formula 1:

[0015] [Equation 1]

[0016] VA (wt%) = W * (MVA / MA)

[0017] (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

[0018] 3. In the above 1 to 2 embodiments, the decrosslinked EVA resin may have a recycling index (RI) defined by Formula 2 below of 100 or more:

[0019] [Equation 2]

[0020] RI = (100 * E * M) / C

[0021] (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

[0022] 4. In the above 1 to 3 embodiments, the decrosslinked EVA resin may have a ratio of elongation rate (%) to gel fraction (wt%) (E / C) of 5 or more.

[0023] 5. In the above 1 to 4 embodiments, the decrosslinked EVA resin may be a decrosslinked version of crosslinked EVA.

[0024] 6. Another aspect of the present invention relates to a composition. The composition comprises the decrosslinked EVA resin of embodiments 1 to 5.

[0025] 7. In the above 6 embodiments, the composition may contain 5% to 90% by weight of decrosslinked EVA resin.

[0026] 8. In the above 6 to 7 embodiments, the composition may further include 20 weight% or less of cross-linked EVA resin.

[0027] 9. In the above 6 to 8 embodiments, the composition may further include 5% to 90% by weight of general new EVA resin.

[0028] 10. Another aspect of the present invention relates to an EVA molded article comprising the composition of the 6 embodiments above.

[0029] 11. Another aspect of the present invention relates to a method for recycling a cross-linked EVA molded article. The method comprises the step of biscuiting a cross-linked EVA molded article to produce a decross-linked EVA resin having a gel fraction of 40 wt% or less and an elongation of 200% or more.

[0030] 12. In the above 11 embodiment, the biscuit extrusion can be performed at a temperature of 200°C to 380°C.

[0031] 13. In the above 11 to 12 embodiments, the biscuit extrusion may be performed in the presence of a subcritical fluid or a supercritical fluid.

[0032] 14. In the above embodiments 11 to 13, the decrosslinked EVA resin may have a content of 3 wt% or more of VA (vinyl acetate) defined by the following formula 1:

[0033] [Equation 1]

[0034] VA (wt%) = W * (MVA / MA)

[0035] (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

[0036] 15. In the above embodiments 11 to 14, the decrosslinked EVA resin may have a recycling index (RI) defined by Formula 2 below of 100 or more:

[0037] [Equation 2]

[0038] RI = (100 * E * M) / C

[0039] (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

[0040] 16. In the above 11 to 15 embodiments, the cross-linked EVA molded body may be cross-linked by a peroxide.

[0041] 17. In the above 11 to 16 embodiments, the cross-linked EVA molded body may have a gel fraction of 70 wt% to 90 wt%.

[0042] 18. In the above 11 to 17 embodiments, the method may further include the step of forming a composition by mixing one or more selected from the group consisting of a cross-linked EVA resin and a general new EVA resin with the decross-linked EVA resin prepared above.

[0043] 19. In the above 11 to 18 embodiments, the step of foaming the composition may be further included.

[0044] 20. In the above 11 to 19 embodiments, the composition may contain 20 weight% or less of cross-linked EVA resin.

[0045] 21. In the above 11 to 20 embodiments, the composition may contain 5% to 90% by weight of general new EVA resin.

[0046] The present invention has the effect of providing a decrosslinked EVA resin, a composition containing the same, and a method for recycling a crosslinked EVA molded body, which can produce a high-quality EVA product having a low gel fraction and high elongation, a high VA content, and reprocessable, and in particular, when using a sub- or supercritical fluid, the by-products generated during decrosslinking are reduced and the color is improved.

[0047] Figure 1 is a photograph of an EVA foam containing 50 wt% of decrosslinked EVA resin prepared in Examples 1 and 2 and a crosslinked EVA foam of Comparative Example 1.

[0048] The present invention will be described in more detail below. Where terms such as 'comprising,' 'having,' and 'consisting of' are used in this specification, other parts may be added unless 'only' is used. Where a component is expressed in the singular, it includes cases where it includes the plural unless specifically stated otherwise.

[0049] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0050] Hereinafter, with reference to the drawings, an embodiment of the present invention specifically describes a decrosslinked EVA resin, a composition including the same, and a method for manufacturing the same.

[0051]

[0052] One aspect of the present invention relates to a decrosslinked EVA resin.

[0053] Generally, crosslinking refers to the bonding of one polymer chain to another, in which monomers are repeatedly connected, while de-crosslinking refers to the process of removing or weakening crosslinking bonds.

[0054] The decrosslinked EVA resin according to the present invention can be produced by a decrosslinking reaction of crosslinked EVA. That is, the decrosslinked EVA resin may be a decrosslinked product of crosslinked EVA. The EVA (ethylene-vinyl acetate) resin may include a random copolymer of ethylene-vinyl acetate monomers, and the decrosslinking reaction may be performed to control the physical properties of the polymer or to improve recyclability.

[0055] The above decrosslinked EVA resin has a gel fraction of about 40 wt% or less. In a specific example, the gel fraction may be about 38 wt% or less, for example, about 2 to 35 wt%. In the case of conventional crosslinked EVA foam, the gel fraction of the decrosslinked EVA resin may be somewhat high because a large amount of inorganic material may be included.

[0056] The above decrosslinked EVA resin has an elongation of about 200% or more. In a specific example, the elongation may be about 250% or more, for example about 300% or more, preferably about 400% to 600%.

[0057] The above decrosslinked EVA resin may have a content of about 3 wt% or more of VA (vinyl acetate) defined by Formula 1 below:

[0058] [Equation 1]

[0059] VA (wt%) = W * (MVA / MA)

[0060] (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

[0061] The VA content above may be significantly influenced by the VA content of the EVA raw material. In a specific example, the VA content may be about 5 wt% or more, for example, about 7 wt% or more, preferably about 10 wt% to 30 wt%. Within this range, a high-quality EVA product capable of reprocessing can be manufactured.

[0062] The above decrosslinked EVA resin may have a recycling index (RI) defined by the following Formula 2 of about 100 or more:

[0063] [Equation 2]

[0064] RI = (100 * E * M) / C

[0065] (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

[0066] In a specific example, the recycling index (RI) may be about 150 to 1000, for example, about 155 to 750. High-quality EVA products that can be reprocessed can be manufactured within this range.

[0067] The above decrosslinked EVA resin may have a ratio of elongation (%) to gel fraction (wt%) (E / C) of about 5 or more. In a specific example, the ratio (E / C) may be about 12 or more, for example, about 15 to 30. High-quality EVA products that are reprocessable can be manufactured within this range.

[0068] The above-mentioned decrosslinked EVA resin may be a decrosslinked version of crosslinked EVA. In a specific example, the above-mentioned crosslinked EVA may be crosslinked by a peroxide. The decrosslinking process of the above-mentioned EVA crosslinked by a peroxide is simple, can save energy, and can be easily reused after decrosslinking.

[0069]

[0070] Another aspect of the present invention relates to a composition comprising the above-described decrosslinked EVA resin.

[0071] In a specific example, the composition may include a decrosslinked EVA resin and a crosslinked EVA resin. The composition may include the decrosslinked EVA resin in an amount of about 5% to 90% by weight. In a specific example, it may include about 10% to 50% by weight, for example, about 20% to 50% by weight. Conventionally, the decrosslinked EVA resin could only be added up to about 10% to 15% by weight, and it was impossible to add more than about 20% by weight. On the other hand, the present invention has the advantage of not only being able to add more than about 20% by weight, particularly more than about 50% by weight of decrosslinked EVA resin, but also maintaining mechanical properties even when adding a high amount of decrosslinked EVA resin.

[0072] In one embodiment, the composition may further include the cross-linked EVA resin in an amount of about 20 weight% or less. In an embodiment, it may include about 15 weight% or less, for example, about 12 weight% or less, preferably about 5 weight% to 10 weight%. Within this range, a high-quality EVA product that is reprocessable can be manufactured.

[0073] In addition, in a specific embodiment, the composition may further include a general new EVA resin. That is, the composition may include a blend of the decrosslinked EVA resin and the general new EVA resin. The composition may include the general new EVA resin in an amount of about 5% to 90% by weight. In a specific embodiment, it may include about 10% to 50% by weight, for example, about 20% to 50% by weight. Within this range, a high-quality EVA product capable of reprocessing can be manufactured.

[0074] The above composition may include a crosslinking agent, a foaming agent, etc. The crosslinking agent may include a peroxide-based compound for crosslinking the EVA foam composition, and may be included in an amount of about 0.2 phr to 1.5 phr of the total composition, about 0.3 phr to 1.2 phr in specific examples, for example, about 0.4 phr to 0.8 phr. In addition, the foaming agent may include an azo-based compound, a nitroso-based compound, a sulfonylhydrazide-based compound, etc., to form the foam cell structure of the EVA foam, and may be included in an amount of about 3 phr to 11 phr of the total composition, about 4 phr to 10 phr in specific examples, for example, about 5 phr to 9 phr. High-quality EVA products capable of reprocessing can be manufactured within the above ranges.

[0075] The above composition may additionally include inorganic materials such as CaCO3, TiO2, etc. for a nucleation effect and color during foaming. The inorganic material may be included in an amount of about 2 phr to 10 phr of the total composition, about 3 phr to 9 phr in specific examples, for example, about 4 phr to 8 phr.

[0076]

[0077] Another aspect of the present invention relates to an EVA molded article comprising the composition described above. Since the EVA molded article can utilize decrosslinked EVA resin, it is environmentally friendly and can reduce raw material costs. In one embodiment, the composition can be used as a foam. In this case, by using the decrosslinked EVA resin included in the composition, processability and mechanical properties are improved compared to conventional crosslinked EVA crushed foam, thereby enabling the production of a foam with excellent properties. Furthermore, in one embodiment, the composition can be used as a solar encapsulant. When EVA is used as a solar encapsulant, there is a problem in that it is difficult to recycle EVA waste generated during the process due to the crosslinking agent contained in the EVA. Therefore, the EVA for solar encapsulant is decrosslinked, and by including the composition and crosslinking without foaming, it can be used as a solar encapsulant, etc.

[0078]

[0079] Another aspect of the present invention relates to a method for recycling a cross-linked EVA molded body.

[0080] The above method includes the step of producing a decrosslinked EVA resin by biaxially extruding a crosslinked EVA molded body.

[0081] The above twin-screw extrusion can be performed at a temperature of about 200°C to 380°C. In a specific example, the temperature may be about 220°C to 360°C, for example, about 250°C to 350°C. High-quality EVA products that can be reprocessed can be manufactured within this range. Compared to general crushed material recycling, high-quality recycling is possible, and compared to a complete decomposition process, decrosslinked EVA resin can be manufactured with simpler and energy-saving methods.

[0082] In one embodiment, the twin-screw extrusion may be performed in the presence of a subcritical or supercritical fluid. When using the subcritical fluid, temperature and pressure can be easily controlled, which simplifies the decrosslinking process, saves energy, and facilitates reuse after decrosslinking. Additionally, the supercritical fluid has excellent solute penetration and reactivity, allowing it to penetrate into the resin with a large free volume and uniformly transfer thermal energy. Through this, recycled resin of uniform quality can be produced during the decrosslinking process of the crosslinked EVA molded body.

[0083] The above-mentioned fluids may include alcohols having 1 to 4 carbon atoms, acetone, water, organic solvents, carbon dioxide, etc. In specific examples, methanol, ethanol, etc. may be used. However, the fluids are not limited to those described above.

[0084] The above fluid may be introduced in an amount of about 0.5 wt% to 20 wt%, in a specific example about 1.0 wt% to 15 wt%, for example about 2 wt% to 10 wt%. Within this range, high-quality EVA products that are reprocessable can be manufactured, and decrosslinked EVA resin can be manufactured simply and with energy savings without grinding or decomposition processes.

[0085] The above decrosslinked EVA resin may have a content of about 3 wt% or more of VA (vinyl acetate) defined by Formula 1 below:

[0086] [Equation 1]

[0087] VA (wt%) = W * (MVA / MA)

[0088] (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

[0089] The VA content above may be significantly influenced by the VA content of the EVA raw material. In a specific example, the VA content may be about 5 wt% or more, for example, about 7 wt% or more, preferably about 10 wt% to 30 wt%. Within this range, a high-quality EVA product capable of reprocessing can be manufactured.

[0090] The above decrosslinked EVA resin can satisfy a recycling index (RI) of about 100 or more, defined by the following Equation 2:

[0091] [Equation 2]

[0092] RI = (100 * E * M) / C

[0093] (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

[0094] In a specific example, the recycling index (RI) may be about 150 to 1000, for example, about 155 to 750. High-quality EVA products that can be reprocessed can be manufactured within this range.

[0095] The above decrosslinked EVA resin may have a ratio of elongation (%) to gel fraction (wt%) (E / C) of about 5 or more. In a specific example, the ratio (E / C) may be about 12 or more, for example, about 15 to 30. High-quality EVA products that are reprocessable can be manufactured within this range.

[0096] The above-mentioned crosslinked EVA molded body may be crosslinked by a peroxide. The decrosslinking process of the above-mentioned EVA molded body crosslinked by a peroxide is simple, can save energy, and can be easily reused after decrosslinking.

[0097] In a specific example, the peroxide may include, but is not limited to, di-tert-amyl peroxide, 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexane, 2,5-di(tert-butylperoxy)-2,5-dimethylhexane, tert-butylcumyl per-oxide, di(tert-butyl)peroxide, dicumyl peroxide, di(tert-butylperoxy-isopropyl)benzene, butyl-4,4-bis(tert-butylperoxy)valerate, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, tert-butylperoxybenzoate, diben-zoyl peroxide, etc.

[0098] The cross-linked EVA molded body may have a gel fraction of about 70 wt% to 90 wt%. In a specific example, the gel fraction may be about 72 wt% to 88 wt%, for example, about 75 wt% to 85 wt%. High-quality EVA products that are reprocessable can be manufactured within the above range.

[0099] The above-derivatively manufactured decrosslinked EVA resin has a gel fraction of about 40 wt% or less and an elongation of about 200% or more.

[0100] The method may further include the step of forming a composition by mixing one or more selected from the group consisting of cross-linked EVA resin and general new EVA resin with the above-mentioned decross-linked EVA resin. The composition may contain about 5% to 90% by weight of the decross-linked EVA resin, and the mixing ratio may be increased compared to conventional decross-linked EVA resin.

[0101] The above composition may be foamed. In the above step, the foaming agent may be pyrolyzed, and the pyrolyzation products may form bubbles within the polymer, thereby forming a new foam. The above composition may further include cross-linked EVA resin in an amount of about 20 weight% or less. In a specific example, it may include about 15 weight% or less, for example, about 12 weight% or less, preferably about 5 weight% to 10 weight%. Within this range, a high-quality EVA product capable of reprocessing can be manufactured.

[0102] In addition, the composition may further include general virgin EVA resin in an amount of about 5% to 90% by weight. In a specific example, it may include about 10% to 50% by weight, for example, about 20% to 50% by weight. High-quality EVA products that are reprocessable can be manufactured within the above range.

[0103] In a specific example, the foaming can be carried out in a conventional manner using a foaming press at a temperature of about 150°C to 200°C, and in a specific example, at about 165°C to 190°C.

[0104]

[0105] The present invention is to be explained more specifically below through examples and comparative examples; however, these examples are for illustrative purposes only and should not be interpreted as limiting the invention.

[0106]

[0107] Examples

[0108] Example 1

[0109] Decrosslinked EVA resin was prepared by performing decrosslinking extrusion of crosslinked EVA resin using a twin-screw extruder (SM Platek, 30mmΦ Screw) at 330℃ and a die temperature of 220℃.

[0110]

[0111] Example 2

[0112] The procedure was carried out in the same manner as Example 1 above, except that 5 wt% of ethanol, which is a sub-supercritical fluid, was injected to perform decrosslinking extrusion.

[0113]

[0114] Comparative Example 1

[0115] Cross-linked EVA foam that had not undergone de-crosslinking extrusion was used.

[0116]

[0117] Comparative Example 2

[0118] Decrosslinking extrusion of crosslinked EVA resin was performed at a high temperature of 400°C using a uniaxial extruder.

[0119]

[0120] Comparative Example 3

[0121] The procedure was performed in the same manner as Example 1, except that the extrusion temperature was changed to 180℃. It was confirmed that almost no decrosslinking occurred.

[0122]

[0123] Comparative Example 4

[0124] The procedure was carried out in the same manner as Example 1, except that the extrusion temperature was changed to 380℃. It was confirmed that the VA content was almost eliminated.

[0125]

[0126] The physical properties of the above examples and comparative examples were evaluated by the following method, and the results are shown in Table 1:

[0127]

[0128] Methods for evaluating physical properties

[0129] (1) Gel fraction (wt%)

[0130] Gel fraction was analyzed using xylene according to ASTM D2765 standards. In this case, 120-mesh stainless steel was used, and the gel content was measured by extracting in xylene at a temperature of 140°C or higher and drying, and the gel fraction was defined as the percentage of the weight of the insoluble matter relative to the weight of the raw sample.

[0131]

[0132] (2) Growth rate (%)

[0133] Elongation was measured at a speed of 50 mm / min using a Type IV specimen of ASTM D638.

[0134]

[0135] (3) VA content (wt%)

[0136] The VA content in the EVA resin was measured using a TGA 8000 (PerkinElmer). At this time, the weight loss ratio due to the deacetylation reaction of the EVA resin occurring at temperatures between 300°C and 400°C was calculated via TGA (thermogravimetric analysis). Using the molecular weight of the VA monomer (86.09 g / mol) and the molecular weight of acetic acid (65.05 g / mol), the VA content was determined according to Equation 1 below:

[0137] [Equation 1]

[0138] VA (wt%) = W * (MVA / MA)

[0139] (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

[0140]

[0141] (4) Melt index (g / 10min)

[0142] ​The melt index (MI2.16) was measured using a TOYOSEIKI MELT INDEXER measuring device and according to ASTM D 1238 at 190°C with a load of 2.16 kg.

[0143]

[0144] (5) Recycling index (RI)

[0145] The recycling index of decrosslinked EVA resin was calculated by the following Equation 2:

[0146] [Equation 2]

[0147] RI = (100 * E * M) / C

[0148] (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

[0149]

[0150] (6) Ratio of elongation rate (E) to gel fraction (C): After measuring the gel fraction and elongation rate of the decrosslinked EVA resin, the ratio of elongation rate (%) to gel fraction (wt%) (E / C) was calculated.

[0151] Gel fraction (wt%) Elongation (%) Content of VA (wt%) MI 2.16 (g / 10min) Recycling Index (RI) E / C Example 1 3558111.70.2332.0016.6 Example 2 3352010.10.2315.1515.8 Comparative Example 18119019.70.012.352.3 Comparative Example 2 151120.20.2149.337.5 Comparative Example 3 7519518.30.012.602.6 Comparative Example 4 252350.40.194.009.4

[0152] As shown in Table 1 above, Examples 1-2 according to the present invention achieved a high elongation rate while having a significantly lower gel fraction compared to cross-linked EVA, and were able to prevent a decrease in VA content. On the other hand, Comparative Example 2 had a low VA content and a low elongation rate due to excessive deacetase and decrosslinking reactions, and Comparative Example 3 hardly underwent decrosslinking. In addition, it was confirmed that Comparative Example 4 exhibited an excessive deacetase reaction and a significant deterioration in physical properties.

[0153]

[0154] A composition was prepared by mixing the decrosslinked EVA resin and the crosslinked EVA resin prepared in Examples 1 and 2 in a weight ratio of 50 wt% : 50 wt% to produce a foam. Foaming was performed using a foaming press at a temperature of 170°C at a 160% expansion rate. Photographs of the prepared foam and the crosslinked EVA foam (Comparative Example 1) are shown in Fig. 1. As shown in Fig. 1, it was confirmed that Examples 1 and 2 could produce a foam even when containing as much as 50 wt% of decrosslinked EVA resin. In addition, it was observed that the color was improved when using a resin decrosslinked using a supercritical fluid.

[0155]

[0156] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be included within the scope of the present invention.

Claims

1. It is a decrosslinked EVA (ethylene-vinyl acetate) resin, and The gel fraction is 40 wt% or less, and Decrosslinked EVA resin characterized by an elongation rate of 200% or more.

2. In Paragraph 1, The above decrosslinked EVA resin is a decrosslinked EVA resin having a content of 3 wt% or more of VA (vinyl acetate) defined by Formula 1 below: [Equation 1] VA (wt%) = W * (MVA / MA) (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

3. In Paragraph 1, The above decrosslinked EVA resin is a decrosslinked EVA resin having a recycling index (RI) defined by Formula 2 below of 100 or more: [Equation 2] RI = (100 * E * M) / C (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

4. In Paragraph 1, The above decrosslinked EVA resin is a decrosslinked EVA resin having a ratio (E / C) of the elongation rate (%) to the gel fraction (wt%) of 5 or more.

5. In Paragraph 1, The above-mentioned decrosslinked EVA resin is a decrosslinked EVA resin that is a decrosslinked body of crosslinked EVA.

6. A composition comprising a decrosslinked EVA resin according to any one of claims 1 to 5.

7. In Paragraph 6, The above composition comprises 5% to 90% by weight of decrosslinked EVA resin.

8. In Paragraph 6, The above composition further comprises 20 weight% or less of cross-linked EVA resin.

9. In Paragraph 6, The above composition further comprises 5% to 90% by weight of general new EVA resin.

10. An EVA molded article comprising the composition of claim 6.

11. A method for recycling a cross-linked EVA molded body, wherein the method comprises: A method comprising the step of producing a decrosslinked EVA resin having a gel fraction of 40 wt% or less and an elongation of 200% or more by biscuit extrusion of a crosslinked EVA molded body.

12. In Paragraph 11, A method for recycling a cross-linked EVA molded body, wherein the above-mentioned twin-screw extrusion is performed at a temperature of 200°C to 380°C.

13. In Paragraph 11, A method for recycling a cross-linked EVA molded body, wherein the above-mentioned twin-screw extrusion is performed in the presence of a subcritical fluid or a supercritical fluid.

14. In Paragraph 11, A method for recycling a cross-linked EVA molded body, wherein the above-mentioned decrosslinked EVA resin has a content of 3 wt% or more of VA (vinyl acetate) defined by Formula 1 below: [Equation 1] VA (wt%) = W * (MVA / MA) (In Equation 1, VA is the vinyl acetate content, W is the weight loss ratio measured by TGA, MVA is the molecular weight of the VA monomer, and MA is the molecular weight of acetic acid).

15. In Paragraph 11, A method for recycling a cross-linked EVA molded body, wherein the above-mentioned decrosslinked EVA resin satisfies a recycling index (RI) of 100 or more as defined by Formula 2 below: [Equation 2] RI = (100 * E * M) / C (In Equation 2, E is the elongation rate (%), M is the melt index (ASTM D 1238, 190℃, 2.16kg) (g / 10min), and C is the gel fraction (wt%)).

16. In Paragraph 11, A method for recycling a cross-linked EVA molded body, wherein the cross-linked EVA molded body has a gel fraction of 70 wt% to 90 wt%.

17. In Paragraph 11, A method for recycling a cross-linked EVA molded body, further comprising the step of forming a composition by mixing one or more selected from the group consisting of a cross-linked EVA resin and a general new EVA resin with the above-mentioned decross-linked EVA resin.

18. In Paragraph 17, A method for recycling a cross-linked EVA molded body, further comprising the step of foaming the above composition.

19. In Paragraph 18, A method for recycling a cross-linked EVA molded body, wherein the above composition contains 20 weight% or less of cross-linked EVA resin.

20. In Paragraph 18, A method for recycling a cross-linked EVA molded body, wherein the above composition comprises 5% to 90% by weight of general new EVA resin.

Images