Green recyclable foaming material for shoe body

Abstract

The invention relates to the technical field of materials, and discloses a green recyclable foaming material for shoes, the foaming material is prepared by blending and foaming EVA (ethylene vinyl acetate) as a base material and auxiliary materials such as a functional aid, and the functional aid structurally contains a large amount of flame-retardant elements such as sulfur, silicon and phosphorus. According to the present invention, in the material combustion process, the hard and compact silicon-containing carbon layer can be rapidly formed so as to isolate oxygen from heat, such that the continuous inward combustion is difficult so as to effectively improve the flame retardant property of the material; according to the present invention, the phosphate group in the functional auxiliary agent structure can perform a reversible ester exchange reaction with the vinyl acetate in the EVA matrix under the action of the catalyst, such that the covalent dynamic reversible crosslinking of the EVA is achieved by using the functional auxiliary agent as the crosslinking agent, and the dynamic reversible disulfide bond is further contained in the functional auxiliary agent structure so as to achieve the covalent dynamic reversible crosslinking of the EVA; therefore, the purpose of secondary foaming and cyclic utilization of the foaming material is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a green and recyclable foaming material for a shoe body. Background Art

[0002] Foaming materials, as a major research and development achievement of modern materials science, have been widely used in all walks of life, especially in the manufacture of shoe bodies. Foaming materials not only determine the comfort, durability and stability of shoes, but also profoundly affect the overall performance and user experience of shoes. Ethylene-vinyl acetate copolymer (EVA), as a commonly used foaming material for shoe bodies, has many advantages. It reduces high crystallinity and improves flexibility, impact resistance, filler compatibility and heat sealing properties by introducing vinyl acetate monomer into the molecular chain. Therefore, EVA is widely used in the soles and interior materials of mid-to-high-end tourist shoes, hiking shoes, slippers and sandals. However, EVA is derived from petrochemical raw materials, is difficult to decompose at the end of its life cycle, and is prone to environmental pollution. Secondly, although the dependence on petrochemical raw materials can be reduced by mixing with bio-based materials such as starch-based materials, this process requires high temperature and high pressure preparation, consumes a lot of energy, and increases costs. In addition, EVA foam material is extremely flammable, and its combustion is accompanied by molten dripping, which can easily cause the spread of fire. With the continuous occurrence of fire accidents in recent years, the flame retardant properties of various materials have gradually become an important factor in consumer evaluation, which has led to the gradual application of EVA foam materials in the fields of shoe bodies. Therefore, how to improve the flame retardant and other functional properties of EVA foam materials and realize the recycling of EVA foam materials has become a research hotspot in recent years. Summary of the invention

[0003] In order to solve the problems mentioned in the background technology, the object of the present invention is to provide a green and recyclable foaming material for a shoe body.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A green and recyclable foaming material for a shoe body, made from raw materials including the following weight fractions:

[0006]

[0007] As a further embodiment of the present invention, the foaming agent is selected from azodicarbonamide or 2,2'-azobisisobutyronitrile; and the foaming aid is selected from zinc oxide or zinc stearate.

[0008] As a further embodiment of the present invention, the preparation method of the functional additive comprises the following preparation steps:

[0009] Step S1, adding 3,3'-dithiodipropionic acid and 1,5-bis(glycidoxypropyl)-3-phenyl-1,1,3,5,5-pentamethyltrisiloxane to toluene, stirring, and after forming a uniform solution, adding a phase transfer catalyst, and then gradually raising the temperature to 60-70° C., and maintaining the temperature and stirring for 8-12 hours to form a functional precursor;

[0010] Step S2, mixing the functional precursor with 1,4-dioxane, and then adding chlorophosphate monomer and acidifying agent to the resulting mixed solution, after the addition, heating to 70-80° C., keeping the temperature for reaction for 4-6 hours, to obtain a functional additive.

[0011] As a further embodiment of the present invention, in step S1, the molar ratio of the 3,3'-dithiodipropionic acid to 1,5-bis(glycidoxypropyl)-3-phenyl-1,1,3,5,5-pentamethyltrisiloxane is 1:1-1.2.

[0012] As a further embodiment of the present invention, in step S1, the phase transfer catalyst is any one of tetramethylammonium bromide, tetramethylammonium chloride, tetrabutylammonium bromide or tetrabutylammonium chloride.

[0013] As a further embodiment of the present invention, in step S2, the acidifying agent is triethylamine or pyridine.

[0014] As a further embodiment of the present invention, in step S2, the chlorophosphate monomer is dimethyl chlorophosphate or diethyl chlorophosphate.

[0015] As a further embodiment of the present invention, the inorganic filler is selected from any one of talc, titanium dioxide or calcium carbonate; and the catalyst is selected from any one of tetrabutyl titanate or tetrapropyl titanate.

[0016] As a further embodiment of the present invention, the method for preparing the foaming material comprises the following steps:

[0017] The first step is to weigh and prepare all the raw materials according to their weight;

[0018] Step 2: Add ethylene-vinyl acetate copolymer, functional additives and catalyst into a mixer, control the mixing temperature to 150-160°C, mechanically stir and mix for 10-15 minutes, then lower the temperature to 100-120°C, continue to add foaming agent, foaming aid and inorganic filler, stir for 5-10 minutes to form a premix;

[0019] The third step is to perform compression molding and foaming on the premix at a temperature of 160-170°C and take it out after 5-10 minutes.

[0020] Beneficial effects of the present invention:

[0021] The present invention prepares a functional auxiliary agent as an additive. The functional auxiliary agent is prepared by ring-opening polymerization using 3,3'-dithiodipropionic acid and 1,5-bis(glycidoxypropyl)-3-phenyl-1,1,3,5,5-pentamethyltrisiloxane, and then further reacting the formed product with a chlorophosphate monomer. Therefore, the functional auxiliary agent structure contains a large amount of sulfur, silicon, and phosphorus flame retardant elements, and can quickly form a hard and dense silicon-containing carbon layer when the material burns, isolate oxygen and heat, and make it difficult for the combustion to continue inward, thereby effectively improving the flame retardant performance of the material. In addition, in the subsequent high-temperature heating and mixing process, the phosphate group in the functional auxiliary agent structure can undergo a reversible ester exchange reaction with vinyl acetate in an EVA matrix under the action of a catalyst, thereby equivalent to using the functional auxiliary agent as a crosslinking agent to achieve covalent dynamic reversible crosslinking of EVA. In addition, the functional auxiliary agent structure also contains a dynamically reversible disulfide bond, thereby achieving the purpose of enabling the foaming material to be recycled for secondary foaming.

[0022] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0024] Figure 1 This is the FT-IR graph of the functional additive. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Preparation Example

[0027] Preparation of functional additives:

[0028] Step S1, adding 0.5 g of 3,3'-dithiodipropionic acid and 1.2 g of 1,5-bis(glycidoxypropyl)-3-phenyl-1,1,3,5,5-pentamethyltrisiloxane to toluene, stirring, and after forming a uniform solution, adding 0.1 g of tetrabutylammonium bromide, and then gradually raising the temperature to 65°C, and keeping the temperature under stirring for 9 hours to form a functional precursor;

[0029] Step S2, 1.2 g of the functional precursor was mixed with 1,4-dioxane, and then 0.2 g of dimethyl phosphate and 0.5 g of triethylamine were added to the resulting mixed solution. After the addition was completed, the temperature was raised to 75° C. and the mixture was kept warm for 6 hours to obtain a functional additive.

[0030] Figure 1 This is the infrared analysis test (FT-IR) diagram of the functional additive, where 3000-3100cm -1 The characteristic absorption peak at 2800-3000cm is the characteristic absorption peak of CH of benzene ring. -1 The characteristic absorption peaks appearing at 1736cm are the CH characteristic absorption peaks of methyl and methylene. -1 The characteristic absorption peak at 1239 cm is the ester group C=O characteristic absorption peak generated by the ring-opening reaction between carboxyl and epoxy groups. -1 The characteristic absorption peak at 1047cm is the characteristic absorption peak of P=O. -1 The characteristic absorption peak that appears at is the Si-O characteristic absorption peak.

[0031] Example 1

[0032] A green and recyclable foaming material for a shoe body, made from raw materials including the following weight fractions:

[0033]

[0034] The preparation method of the foaming material comprises the following steps:

[0035] The first step is to weigh and prepare all the raw materials according to their weight;

[0036] Step 2: Add ethylene-vinyl acetate copolymer, functional additives and tetrabutyl titanate into a mixer, control the mixing temperature to 150°C, mechanically stir and mix for 10 minutes, then lower the temperature to 100°C, continue to add azodicarbonamide, zinc oxide and talc, and stir for 10 minutes to form a premix;

[0037] The third step is to perform compression molding and foaming on the premix at a temperature of 170°C and take it out after 5 minutes.

[0038] The functional auxiliary agent used is the functional auxiliary agent prepared in the preparation example; the same applies to the following.

[0039] Example 2

[0040] A green and recyclable foaming material for a shoe body, made from raw materials including the following weight fractions:

[0041]

[0042]

[0043] The preparation method of the foaming material comprises the following steps:

[0044] The first step is to weigh and prepare all the raw materials according to their weight;

[0045] Step 2: Add ethylene-vinyl acetate copolymer, functional additives and tetrapropyl titanate into a mixer, control the mixing temperature to 155°C, mechanically stir and mix for 12 minutes, then lower the temperature to 110°C, continue to add 2,2'-azobisisobutyronitrile, zinc stearate and titanium dioxide, stir for 8 minutes to form a premix;

[0046] The third step is to perform compression molding and foaming on the premix at a temperature of 165°C and take it out after 6 minutes.

[0047] Example 3

[0048] A green and recyclable foaming material for a shoe body, made from raw materials including the following weight fractions:

[0049]

[0050] The preparation method of the foaming material comprises the following steps:

[0051] The first step is to weigh and prepare all the raw materials according to their weight;

[0052] Step 2: Add ethylene-vinyl acetate copolymer, functional additives and tetrapropyl titanate into a mixer, control the mixing temperature to 160°C, mechanically stir and mix for 10 minutes, then lower the temperature to 120°C, continue to add 2,2'-azobisisobutyronitrile, zinc stearate and calcium carbonate, stir for 5 minutes to form a premix;

[0053] The third step is to perform compression molding and foaming on the premix at a temperature of 170°C and take it out after 5 minutes.

[0054] Comparative Example 1

[0055] A green and recyclable foaming material for a shoe body, made from raw materials including the following weight fractions:

[0056]

[0057] The preparation method of the foaming material comprises the following steps:

[0058] The first step is to weigh and prepare all the raw materials according to their weight;

[0059] Step 2: Add ethylene-vinyl acetate copolymer and tetrapropyl titanate into a mixer, control the mixing temperature to 155°C, mechanically stir and mix for 12 minutes, then lower the temperature to 110°C, continue to add 2,2'-azobisisobutyronitrile, zinc stearate and titanium dioxide, stir for 8 minutes to form a premix;

[0060] The third step is to perform compression molding and foaming on the premix at a temperature of 165°C and take it out after 6 minutes.

[0061] Test Case

[0062] The foaming materials in the embodiments and comparative examples were tested for comprehensive properties, and the results are recorded in Table 1:

[0063] Table 1 - Test results

[0064]

[0065] Note: The compression strength is tested with reference to the standard GB / T 8813-2020. After the test, the foaming materials of the same batch are extruded and crushed, and the crushed materials are collected and placed in a mold. The temperature is controlled at 160°C, and hot-pressed and reshaped again for 20 minutes. After natural cooling, the mold is tested again. The limiting oxygen index is tested with reference to the standard GB / T 2406.2-2009.

[0066] From the analysis and test results, it can be seen that the use of the functional additives in the preparation example as additives can make the surface of the foamed material have higher strength and flame retardancy, and after reshaping, the compression strength does not decrease significantly, so it can be recycled for secondary use.

[0067] After removing the functional additives, it is obvious that the strength of the material becomes lower and the flame retardant performance is greatly reduced. This is because the functional additives have a cross-linking effect, which can improve the structural density of the foaming material, and the foaming material without functional additives does not have flame retardant elements.

[0068] Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enable any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, the present invention can also be improved and modified, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements similar to the literal expression of the claims, or if they include equivalent structural elements that are not substantially different from the literal expression of the claims, then these other embodiments should also be included in the scope of the claims.

[0069] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A green and recyclable foaming material for shoe body, characterized in that: Made from raw materials including the following weight fractions:

2. The green and recyclable foaming material for shoe body according to claim 1, characterized in that: The foaming agent is selected from azodicarbonamide or 2,2'-azobisisobutyronitrile; the foaming aid is selected from zinc oxide or zinc stearate.

3. The green and recyclable foaming material for shoe body according to claim 1, characterized in that: The preparation method of the functional additive comprises the following preparation steps: Step S1, using 3,3'-dithiodipropionic acid and 1,5-bis(glycidoxypropyl)-3-phenyl-1,1,3,5,5-pentamethyltrisiloxane as polymerization monomers, and performing ring-opening polymerization under the action of a phase transfer catalyst to form a functional precursor; Step S2: Under the action of an acidifying agent, the chlorophosphate monomer is used to further react with the functional precursor to obtain a functional additive.

4. The green and recyclable foam material for shoe body according to claim 3, characterized in that: In step S1, the molar ratio of the 3,3'-dithiodipropionic acid to 1,5-bis(glycidoxypropyl)-3-phenyl-1,1,3,5,5-pentamethyltrisiloxane is 1:1-1.

2.

5. The green and recyclable foaming material for shoe body according to claim 3, characterized in that: In step S1, the phase transfer catalyst is any one of tetramethylammonium bromide, tetramethylammonium chloride, tetrabutylammonium bromide or tetrabutylammonium chloride.

6. The green and recyclable foam material for shoe body according to claim 3, characterized in that: In step S2, the acidifying agent is triethylamine or pyridine.

7. The green and recyclable foaming material for shoe body according to claim 3, characterized in that: In step S2, the chlorophosphate monomer is dimethyl chlorophosphate or diethyl chlorophosphate.

8. The green and recyclable foaming material for shoe body according to claim 1, characterized in that: The inorganic filler is selected from any one of talc, titanium dioxide or calcium carbonate; the catalyst is selected from any one of tetrabutyl titanate or tetrapropyl titanate.

9. The green and recyclable foaming material for shoe body according to claim 1, characterized in that: The preparation method of the foaming material comprises the following steps: The first step is to weigh and prepare all the raw materials according to their weight; Step 2: Add ethylene-vinyl acetate copolymer, functional additives and catalyst into a mixer, control the mixing temperature to 150-160°C, mechanically stir and mix for 10-15 minutes, then lower the temperature to 100-120°C, continue to add foaming agent, foaming aid and inorganic filler, stir for 5-10 minutes to form a premix; The third step is to perform compression molding and foaming on the premix at a temperature of 160-170°C and take it out after 5-10 minutes.

Images