WO2024011919A1

WO2024011919A1 - Preparation method for eva material and eva material

Info

Publication number: WO2024011919A1
Application number: PCT/CN2023/078579
Authority: WO
Inventors: 王经逸; 肖晖; 陈汝盼; 卢鑫; 张青海; 林鸿裕; 詹迎旭; 王育玲; 刘东斌
Original assignee: 黎明职业大学
Priority date: 2022-07-15
Filing date: 2023-02-28
Publication date: 2024-01-18
Also published as: CN115073773A

Abstract

The present invention provides a preparation method for an EVA material. The preparation method comprises the steps of preparation, crosslinking and molding. The present invention further provides an EVA material obtained by using the preparation method. In the present invention, a mechanical blending method is used, and an ester exchange reaction is used under the action of a catalyst so as to obtain an EVA material with dynamic cross-linking bonding. Due to dynamic cross-linking bonding, the cross-linked EVA can be recycled and processed by using a conventional plastic hot-processing method, and after multiple cycles of processing, good mechanical performance is still maintained; relatively good physical and mechanical properties are kept; and the utilization rate is relatively high.

Description

Preparation method of EVA material and EVA material

Technical field

The present invention relates to an EVA material, in particular to a preparation method of an EVA material and an EVA material.

Background technique

The continuous development of the global plastics industry has brought great convenience to life, and at the same time, it has also produced a large amount of plastic waste around the world. Therefore, developing sustainable plastics with longer lifespans, upcycling or repurposing post-consumer polymers are among the effective ways to reduce plastic waste.

After ethylene-vinyl acetate copolymer (EVA) plastic is cross-linked and foamed, the products have excellent properties such as softness, good elasticity, and chemical corrosion resistance. They are widely used in the soles and interiors of mid-to-high-end travel shoes, hiking shoes, and sports shoes. Material. The traditional EVA cross-linking method mainly uses irreversible chemical cross-linking, which brings great challenges to the recycling or reuse of EVA.

Currently, waste EVA is mainly disposed of through incineration to obtain heat and reprocessing. It is relatively simple to obtain heat through incineration, but incineration will produce toxic chemicals and the utilization rate is low; reprocessing mainly involves chopping and grinding cross-linked EVA into fine powder, and using it as a new EVA material to replace part of the filler, which is the current cross-linked EVA recycling The main method, however, the compatibility of the crushed EVA colloidal particles after cross-linking with the new EVA material is low, so it can only be added or replaced in small amounts, and the utilization rate is low.

In view of this, this application conducted an in-depth study on the above issues, and this case emerged.

technical problem

The purpose of the present invention is to provide a preparation method and EVA material with a relatively high utilization rate of EVA materials.

Technical solutions

In order to achieve the above objects, the present invention adopts the following technical solutions:

A preparation method of EVA material, including the following steps:

S1. Preparation, place the filler particles in a container, pre-disperse the filler particles in a toluene solvent or an ethanol solvent to obtain a suspension, then add an ester silane coupling agent to the suspension, and undergo a modification reaction Finally, a mixture is obtained, the mixture is centrifuged and washed to obtain a filter residue, and then the filter residue is dried to obtain a dynamic cross-linking agent;

S2. Cross-linking: put the EVA raw material into the torque rheometer for pre-dispersion, and then add the transesterification catalyst and the dynamic cross-linking agent to the torque rheometer respectively for blending processing to obtain a blend;

S3. Molding. The blend is vulcanized and molded sequentially to obtain an EVA material.

As an improvement of the present invention, in step S1, add the ester silane coupling agent into the container in 3-5 times, and while adding the ester silane coupling agent, clean the contents in the container. The solution is stirred at a stirring speed of 500-1500 r/min, and then condensed and refluxed at 70-110°C for 2 hours.

As an improvement of the present invention, the filler particles are silica and/or calcium carbonate, the particle size of the filler particles is 20-2000 nm, and the mass fraction of the filler particles is 1%-10%, so The above-mentioned ester silane coupling agents are 2-carbonylmethoxyethyldimethoxymethylsilane, acetoxypropyltrimethoxysilane, and 3-(carbonylmethoxy)propyldimethylmethoxy One or both of silane and 3-(carbonylethoxy)propyldimethylethoxysilane, the EVA raw material is thermoplastic unvulcanized cross-linked EVA with an ethyl acetate content of 10-30%, so The transesterification catalyst is tetrabutyl titanate, tetraethyl titanate, tetraisopropyl titanate or acetyl molybdenum.

As an improvement of the present invention, in step S1, the filler particles are pre-dispersed using ultrasound at 20-40°C for 20-40 minutes.

As an improvement of the present invention, in step S1, when performing centrifugal washing treatment, the mixture is centrifuged 3-5 times at a speed of 8000-12000 r/min, and the time of each centrifugal treatment is 3-7 min. .

As an improvement of the present invention, in step S1, during the drying process, the filter residue is vacuum dried at 80-120°C for 8-20 h.

As an improvement of the present invention, in step S2, the reaction temperature of the torque rheometer is controlled to be 100-180°C and the rotation speed is 50-200 rpm.

As an improvement of the present invention, in step S2, the pre-dispersion time is 5-10 min, the transesterification catalyst is added into the torque rheometer in 3-5 times, and then mixed for 10-30 min, and then The dynamic cross-linking agent is added into the torque rheometer in 3-5 times, and then blended for 10-30 minutes.

As an improvement of the present invention, in step S3, during molding, the molding pressure is 5-20 MPa, the molding temperature is 120-180°C, and the molding time is 0.5-2h.

An EVA material, including 10-30 parts by mass of filler particles, 1-10 parts by mass of ester silane coupling agent, 70-100 parts by mass of EVA, 0.1-2.5 parts by mass of transesterification catalyst and 1-10 parts by mass of dynamic cross-linking The agent is prepared using the above preparation method of EVA material.

beneficial effects

Adopting the above technical solution, the present invention has the following beneficial effects:

The present invention adopts a mechanical blending method and uses transesterification reaction under the action of a catalyst to obtain an EVA material with dynamic cross-linking bonding. The dynamic cross-linking bonding allows the cross-linked EVA to be processed using conventional plastic thermal processing methods. It is recycled and processed, and it still maintains good mechanical properties after multiple cycles of processing, and maintains good physical and mechanical properties, and the utilization rate is relatively high.

Description of drawings

Figure 1 is a schematic structural diagram of the dynamic cross-linking agent in the embodiment;

Figure 2 is a scanning electron microscope image of the EVA-1 foam material in Example 3;

Figure 3 is a scanning electron microscope image of the EVA-2 foam material in Example 3;

Figure 4 is a scanning electron microscope image of the EVA-3 foam material in Example 3.

The symbols in the figure correspond to the following:

1-Filler particles; 2-Ester silane coupling agent.

Embodiments of the invention

The present invention will be further described below with reference to specific examples. The raw materials and test instruments used in the following examples and comparative examples can be purchased directly from the market. The test steps or test steps without specifying specific conditions are It is carried out in accordance with conventional conditions or in accordance with the conditions recommended by the test instrument manufacturer, which will not be described in detail here.

The present invention provides a method for preparing EVA materials, which uses a mechanical blending method to utilize the transesterification reaction between carboxylic acid esters contained in EVA and cross-linking agents containing polyvalent alkyl esters to prepare multi-component cross-linked EVA materials. Change the use and type of cross-linking agent, control the dynamics of the cross-linking network, and regulate the dynamic cross-linking structure and physical and mechanical properties of EVA materials. The method includes the following steps:

S1. Preparation, place filler particles in a container, where the filler particles can be silica and/or calcium carbonate, the particle size of the filler particles is 20-2000 nm, and the mass fraction of the filler particles is 1%-10%.

Then, the filler particles are pre-dispersed in a toluene solvent or an ethanol solvent to obtain a uniform suspension. Specifically, the filler particles are pre-dispersed using ultrasound at 20-40°C for 20-40 minutes. Then, an ester silane coupling agent is added to the suspension, and a mixture is obtained after a modification reaction. The ester silane coupling agent can be 2-carbonylmethoxyethyldimethoxymethylsilane, acetoxy One or two of propyltrimethoxysilane, 3-(carbonylmethoxy)propyldimethylmethoxysilane and 3-(carbonylethoxy)propyldimethylethoxysilane. Preferably, the ester silane coupling agent is added to the container in 3-5 times, and the solution (and suspension) in the container is stirred while adding the ester silane coupling agent. The stirring speed of the stirring process is 500-500. 1500 r/min, and then condense and reflux for 2 hours at 70-110°C.

The mixture is centrifuged and washed to obtain the filter residue. When performing centrifugal washing, the mixture is centrifuged 3-5 times at a speed of 8000-12000 r/min, and the centrifugation time for each time is 3-7 min; the filter residue is then dried. The dynamic cross-linking agent is obtained through the treatment. During the drying process, the filter residue is vacuum dried at 80-120°C for 8-20 h. As shown in Figure 1, the dynamic cross-linking agent obtained by the present invention has a hard segment structure mainly formed by filler particles 1. This hard segment structure is used to connect the ester silane coupling agent 2, which has good stability.

S2. Cross-linking, put EVA raw materials into the torque rheometer and perform pre-dispersion. Control the reaction temperature of the torque rheometer to be 100-180°C, the rotation speed is 50-200 rpm, and the pre-dispersion time is 5-10 minutes. It should be noted that the above-mentioned EVA raw material is thermoplastic unvulcanized cross-linked EVA with an ethyl acetate content of 10-30%.

Then, the transesterification catalyst and the dynamic cross-linking agent were respectively added to the torque rheometer for blending treatment to obtain a blend, in which the transesterification catalyst was tetrabutyl titanate, tetraethyl titanate, and tetraisotitanate. propyl ester or acetyl molybdenum. Add the transesterification catalyst into the torque rheometer in 3-5 times, and then mix for 10-30 minutes. Add the dynamic cross-linking agent into the torque rheometer in 3-5 times, and then blend for 10-30 minutes.

S3. Molding. The blend is vulcanized and molded in sequence to obtain EVA material. The vulcanization treatment is performed using a flat vulcanizer. During molding, the molding pressure is 5-20 MPa and the molding temperature is 120-180°C. The time is 0.5-2h.

The invention also provides an EVA material, including 10-30 parts by mass filler particles, 1-10 parts by mass ester silane coupling agent, 70-100 parts by mass EVA, 0.1-2.5 parts by mass transesterification catalyst and 1-10 parts by mass The mass part of dynamic cross-linking agent is prepared by using the above preparation method of EVA material.

The invention circumvents the traditional irreversible chemical cross-linking method and utilizes the transesterification reaction between the carboxylic acid ester contained in EVA and a specific cross-linking agent containing polyvalent alkyl esters to prepare multi-component cross-linked EVA materials. EVA contains a large number of C=O bonds. The presence of unsaturated bonds makes EVA sensitive to ultraviolet radiation, easily oxidized, and has poor weather resistance. It is prone to aging and failure after long-term exposure. Dynamic cross-linked EVA is formed through transesterification, which reduces the polymer The content of medium unsaturated double bonds effectively improves its UV resistance and high temperature stability and extends its use time. Compared with traditional thermoplastics, due to the formation of a cross-linked network, this network helps stabilize the molecular structure during reprocessing and prevents the breakage of the polymer chains. The present invention adopts a pre-hydrolysis reaction between an ester-containing silane coupling agent and filler particles to obtain an ester-based dynamic cross-linking agent with a hard segment (filler particle) structure. Under the action of the transesterification catalyst, the ester-based dynamic cross-linking agent and EVA The transesterification reaction of carboxylic acid esters produces multi-element cross-linked EVA materials, which shows good reprocessability and maintains good physical and mechanical properties; reinforcing particles are embedded in the EVA molecular chain to avoid simple mechanical blending. It solves the agglomeration problem and effectively improves the mechanical properties of EVA materials that can be recycled.

The preparation method and EVA material of the EVA material of the present invention will be further described below through several examples and comparative examples.

Example 1

According to the preparation method of the above EVA material, 20g of silica is pre-dispersed in 500 mL of toluene solution, ultrasonically dispersed at 25°C for 30 minutes, and 3g of 2-carbonylmethoxyethyldimethoxymethylsilane is added. Stir with an external electric stirrer. Control the stirrer speed to 800 r/min, the reaction temperature to 80°C, and the condensation reflux reaction for 2 hours. The mixture was centrifuged and washed 5 times at 8000 r/min for 5 minutes each time to obtain a filter residue. The filter residue was vacuum dried at 100°C for 15 hours to obtain an ester silane coupling agent grafted silica dynamic cross-linking agent.

In the torque rheometer, put 100g of EVA (product name is DuPont 770), control the temperature of the torque rheometer to 130°C, the rotation speed to 100 rpm, premix for 5 minutes; add 6g of tetrabutyl titanate catalyst, a total of Mix for 5 minutes; add 8g of dynamic cross-linking agent and blend for 30 minutes to obtain a blend. After leaving it for a period of time, place the blend in a flat vulcanizer for vulcanization and molding. The molding pressure for molding is 10Mpa, and the molding temperature is 120 ℃, molding time is 2.5h, and EVA-0 material is obtained.

Finally, the dynamic cross-linked structure is recycled and reused: cut the EVA-0 material into 0.5-2cm blocks and repeat the molding step to obtain EVA-1 material (that is, the EVA material that has been recycled for the first time); then Repeat the shearing and molding steps to obtain EVA-n, where n represents the number of times of recycling; for example: EVA-0 means that it has not been recycled, and EVA-1 means that EVA-0 has been recycled once to obtain EVA-1.

Example 2

According to the above preparation method of EVA material, pre-disperse 20g rice calcium carbonate in 500mL ethanol solution, ultrasonically disperse at 25°C for 30 minutes, add 10g acetoxypropyltrimethoxysilane, and stir with an external electric stirrer. , control the stirrer speed to 800 r/min, the reaction temperature to 80°C, and conduct the condensation reflux reaction for 2 h. The mixture was centrifuged and washed 5 times at 8000 r/min for 5 minutes each time to obtain a filter residue. The filter residue was vacuum dried at 100°C for 15 hours to obtain an ester silane coupling agent grafted calcium carbonate dynamic cross-linking agent.

In the torque rheometer, put 100g of EVA (product name: DuPont 53071), control the temperature of the torque rheometer to 130°C, the rotation speed to 100 rpm, and premix for 5 minutes; add 1.5g of acetyl molybdenum (analytical grade) for a total of Mix for 5 minutes; add 8g of dynamic cross-linking agent and 5g of calcium carbonate, and blend for 30 minutes to obtain a blend; place the blend in a flat vulcanizer for vulcanization and molding. The molding pressure of molding is 10 MPa, and the molding temperature is 150 ℃, molding time is 2h, and EVA-0 material is obtained.

Finally, the dynamic cross-linked structure is recycled and reused: cut the EVA-0 material into 0.5-2cm blocks and repeat the molding steps to obtain EVA-1 material; then repeat the shearing and molding steps to obtain EVA- n.

Example 3

According to the preparation method of the above EVA material, 20g of silica is pre-dispersed in 500 mL of toluene solution, ultrasonically dispersed at 25°C for 30 minutes, and 7g of 3-(carbonylmethoxy)propyldimethylmethoxysilane is added. Use an external electric stirrer for stirring, control the stirrer speed to 800 r/min, the reaction temperature to 80 °C, and the condensation reflux reaction for 2 h. The mixture was centrifuged at 8000 r/min and washed 5 times for 5 min each time to obtain a filter residue. The filter residue was vacuum dried at 100°C for 15 h to obtain an ester silane coupling agent grafted silica dynamic cross-linking agent. .

In the torque rheometer, put 100g of EVA (product name is DuPont 53071), control the temperature of the torque rheometer to 130°C, the rotation speed to 100rpm, premix for 5 minutes; add 1.5g of tetrabutyl titanate, and blend 5min; add 9g of dynamic cross-linking agent and blend for 30 minutes to obtain a blend; place the blend in a flat vulcanizer for vulcanization and molding. The molding pressure of molding is 10MPa, the molding temperature is 150°C, and the molding time is After 2h, EVA-0 material was obtained.

Finally, the dynamic cross-linked structure is destroyed for recycling: put the EVA-0 material back into the torque rheometer, control the reaction temperature to 120°C, and the rotation speed to 70 rpm. After completion, perform molding again to obtain EVA-1, repeat The torque rheometer and compression molding steps were reintroduced to obtain EVA-n.

Example 4

Repeat the preparation method of Example 3, but add 8g of dynamic cross-linking agent (that is, change the dynamic cross-linking agent content of Example 3 from 9g to 8g), and then add 3g of ADC foaming agent (product name is Junpeng HG2097-91 ), and then blended for 30 minutes, keeping the contents of the other components unchanged, to obtain EVA-0 foam material.

Recycling and reusing by destroying the dynamic cross-linked structure: Put the EVA-0 material back into the torque rheometer, control the reaction temperature to 120°C, the rotation speed to 70rpm, and add 3g of ADC foaming agent at the same time. After completion, mold it again , EVA-1 was obtained, and the steps of re-entering the torque rheometer and molding were repeated to obtain EVA-n.

Comparative example 1

Referring to steps S2 and S3 in the preparation method of the above EVA material, put 100g of EVA (DuPont 53071) into the torque rheometer, control the temperature of the torque rheometer to 130°C, the rotation speed to 100rpm, and premix for 5 minutes. ;Add 1.5g tetrabutyl titanate and blend for 5 minutes; add 9g of unmodified silica and blend for 30 minutes to obtain a blend; place the blend in a flat vulcanizer for vulcanization and molding, and molding The molding pressure is 10MPa, the molding temperature is 150°C, the molding time is 2h, and the EVA-0 material is obtained.

Recycling and reusing by destroying the dynamic cross-linked structure: Put the EVA-0 material back into the torque rheometer, control the reaction temperature to 120 ℃, and the rotation speed to 70 rpm. After completion, mold it again to obtain EVA-1, and put it back in again. Torque rheometer and compression molding steps to obtain EVA-n.

Comparative example 2

Referring to the above preparation method of EVA material, pre-disperse 20 parts by mass of silica in 500 mL of toluene solution, ultrasonically disperse at 25°C for 30 minutes, add conventional silane coupling agent KH560, stir with an external electric stirrer, and control the stirring The rotation speed of the reactor was 800 r/min, the reaction temperature was 80°C, and the condensation reflux reaction was carried out for 2 h. The mixture was centrifuged and washed 5 times at 8000 r/min for 4 minutes each time to obtain a filter residue. The filter residue was vacuum dried at 100°C for 12 hours to obtain the coupling agent KH560 grafted silica.

In the torque rheometer, put 100g of EVA (product name is DuPont 53071), control the temperature of the torque rheometer to 130°C, the rotation speed to 100rpm, premix for 5 minutes; add 1.5g of tetrabutyl titanate, and blend 5 minutes; add 9g of coupling agent KH560 silica and blend for 30 minutes to obtain a blend; place the blend in a flat vulcanizer for vulcanization and molding. The molding pressure of molding is 10MPa and the molding temperature is 150 ℃, molding time is 2h, and EVA-0 material is obtained.

Comparative example 3

Referring to steps S2 and S3 in the preparation method of the above EVA material, put 100g of EVA (product name: DuPont 53071) into the torque rheometer, control the temperature of the torque rheometer to 130°C, and the rotation speed to 100rpm. Premix for 5 minutes; add 1.5g tetrabutyl titanate and blend for 5 minutes; add 20g of silica and 7g of dicumyl peroxide (DCP cross-linking agent) and blend for 30 minutes to obtain a blend; Place it in a flat vulcanizer for vulcanization and molding. The molding pressure of molding is 10MPa, the molding temperature is 150°C, and the molding time is 2h to obtain EVA-0 material.

The physical and mechanical properties of the EVA materials obtained in each of the above examples and comparative examples were tested, and the results are as shown in the table below.

As can be seen from the above table, the regenerated EVA obtained in Example 3 has the best effect, and the EVA regenerated foaming material obtained in Example 4 has better performance, meeting the requirements of the ethyl acetate content of EVA and the mole ratio of cross-linking agent triisobutyl borate. The ratio is 3:1; compare to Comparative Example 1, the dosage of ester silane coupling agent is 3g, and the tensile strength of the EVA material obtained due to insufficient cross-linking is low; compare to Comparative Example 2, the dosage of dynamic cross-linking agent is 10g , multiple degrees of cross-linking; compare to Comparative Example 1, silica and 3-(carbonylmethoxy)propyldimethylmethoxysilane were added directly to the torque rheometer, and the silica was not mixed with ester in advance. The silane-like coupling agent was grafted to obtain a dynamic cross-linking agent, but no effective cross-linking system was formed; in Comparative Example 2, KH560 silane coupling agent was used to improve the compatibility between silica and EVA, and the mechanical properties were improved, but no formation of Effective cross-linking system; compared with Comparative Example 3, the traditional DCP cross-linking agent method is directly used. The obtained EVA material has better performance, but cannot be recycled.

The EVA foam material obtained in Example 3 was observed and photographed through a scanning electron microscope. The obtained photographs are shown in Figures 2 to 4. It can be seen from the figures that the cell diameter is 50 to 150 μm, and the foam has a Closed cell structure and good shrinkage resistance.

The present invention has been described in detail above with reference to specific embodiments. However, the implementation of the present invention is not limited to the above-mentioned embodiments. Those skilled in the art can make various modifications to the present invention based on the existing technology, and these all belong to the protection of the present invention. scope.

Claims

A method for preparing EVA material, which is characterized by including the following steps:

S1. Preparation, place the filler particles in a container, pre-disperse the filler particles in a toluene solvent or an ethanol solvent to obtain a suspension, then add an ester silane coupling agent to the suspension, and undergo a modification reaction Finally, a mixture is obtained, the mixture is centrifuged and washed to obtain a filter residue, and then the filter residue is dried to obtain a dynamic cross-linking agent;

S2. Cross-linking: put the EVA raw material into the torque rheometer for pre-dispersion, and then add the transesterification catalyst and the dynamic cross-linking agent to the torque rheometer respectively for blending processing to obtain a blend;

S3. Molding. The blend is vulcanized and molded sequentially to obtain an EVA material.
The preparation method of EVA material according to claim 1, characterized in that, in step S1, add the ester silane coupling agent into the container in 3-5 times, add the ester silane coupling agent While adding the solution, stir the solution in the container at a stirring speed of 500-1500 r/min, and then condense and reflux for 2 hours at 70-110°C.
The preparation method of EVA material according to claim 1, characterized in that the filler particles are silica and/or calcium carbonate, the particle size of the filler particles is 20-2000 nm, and the mass of the filler particles The fraction is 1%-10%, and the ester silane coupling agent is 2-carbonylmethoxyethyldimethoxymethylsilane, acetoxypropyltrimethoxysilane, 3-(carbonylmethoxy ) one or two of propyldimethylmethoxysilane and 3-(carbonylethoxy)propyldimethylethoxysilane, the EVA raw material is ethyl acetate with a content of 10-30% Thermoplastic unvulcanized cross-linked EVA, the transesterification catalyst is tetrabutyl titanate, tetraethyl titanate, tetraisopropyl titanate or acetyl molybdenum.
The preparation method of EVA material according to claim 1, characterized in that, in step S1, the filler particles are pre-dispersed using ultrasound under the conditions of 20-40°C for 20-40 minutes.
The preparation method of EVA material according to claim 1, characterized in that, in step S1, when performing centrifugal washing, the mixture is centrifuged 3-5 times at a speed of 8000-12000 r/min, each time The centrifugation time is 3-7 minutes.
The preparation method of EVA material according to claim 1, characterized in that, in step S1, during the drying process, the filter residue is vacuum dried at 80-120°C for 8-20 h.
The preparation method of EVA material according to claim 1, characterized in that, in step S2, the reaction temperature of the torque rheometer is controlled to be 100-180°C, and the rotation speed is 50-200 rpm.
The preparation method of EVA material according to claim 1, characterized in that, in step S2, the pre-dispersion time is 5-10 min, and the transesterification catalyst is added into the torque rheometer in 3-5 times. , then mix for 10-30 minutes, then add the dynamic cross-linking agent into the torque rheometer in 3-5 times, and then blend for 10-30 minutes.
The preparation method of EVA material according to claim 1, characterized in that, in step S3, during molding, the molding pressure is 5-20 MPa, the molding temperature is 120-180°C, and the molding time is 0.5-2h.
An EVA material, characterized in that it includes 10-30 parts by mass filler particles, 1-10 parts by mass ester silane coupling agent, 70-100 parts by mass EVA, 0.1-2.5 parts by mass transesterification catalyst and 1-10 parts by mass The dynamic cross-linking agent is prepared by the preparation method of the EVA material as described in any one of claims 1-9.