A preparation method for preparing high-density boards using foamed polyolefin scraps

Abstract

This application relates to the field of high-density boards, and specifically discloses a preparation method for preparing high-density boards using foamed polyolefin scraps, including the following steps: crushing the scraps to obtain crushed materials; then adding the crushed materials into a mixing cylinder, heating the crushed materials with steam, controlling the heating temperature at 165-175 °C, stirring at a rotation speed of 8-10 r / min, and the stirring time is 40-60 min, so that the volume of the crushed materials shrinks by 60-75%, thus obtaining shrunk materials; preparing high-density boards: laying the shrunk materials in a mold frame, controlling the pressure of the press at 10-12 kg / cm 2 , controlling the temperatures of the upper pressing plate and the lower pressing plate at 160-170 °C, and the heating time is 30-35 min; taking out the pressed and formed board after pressing, thus obtaining the high-density board. This application has the effects of reducing the energy consumption required for melting the scraps, reducing air pollution, and obtaining high-density boards with good heat insulation performance and high strength.

Description

Technical Field

[0001] This application relates to the field of high-density boards, and more specifically, it relates to a preparation method for high-density boards using foamed polyolefin scraps. Background Art

[0002] Polyolefin foamed materials have the characteristics of rich raw material sources, light weight, excellent cost performance, as well as excellent heat resistance, chemical corrosion resistance, and easy recyclability. Under the background of global industrial upgrading and transformation and the continuous improvement of environmental protection requirements, the trend of polyolefin foamed materials replacing traditional foamed materials is becoming increasingly obvious, and the market prospect is broad.

[0003] At present, during the production process of polyolefin foamed materials, a large amount of scraps and trimmings are often generated, which is likely to cause waste of resources. Therefore, generally, the scraps are recycled and granulated to avoid waste of resources.

[0004] However, since the scraps are secondary foamed materials, the weight of the scraps is very light, and the density is generally 20 - 40 kg / m 3 , resulting in a large apparent volume and a small apparent density of the shredded scraps. If the traditional method is used to process the scraps, the scraps need to be melted, which consumes a large amount of energy, and the scraps will generate flue gas during the granulation process, which is likely to cause air pollution. Therefore, there is still room for improvement. Summary of the Invention

[0005] In order to reduce the energy consumption required for melting the scraps, reduce air pollution, and produce high-density boards with good heat preservation performance and high strength, this application provides a preparation method for high-density boards using foamed polyolefin scraps.

[0006] This application provides a preparation method for high-density boards using foamed polyolefin scraps, adopting the following technical solutions:

[0007] A preparation method for high-density boards using foamed polyolefin scraps, comprising the following steps:

[0008] Step 1: Collect the scraps;

[0009] Step 2: Heat shrink the scraps

[0010] (1) Crush the scraps to obtain crushed materials;

[0011] (2) Pump the crushed materials into a mixing barrel, heat the crushed materials with steam, control the heating temperature at 165 - 175 °C, stir at a rotation speed of 8 - 10 r / min, and the stirring time is 40 - 60 min to shrink the volume of the crushed materials by 60 - 75%, thereby obtaining shrunk materials;

[0012] Step 3: Prepare the high-density board

[0013] (1) Weigh the shrinkage material after heat shrinkage;

[0014] (2) Evenly apply a release agent on the upper platen, lower platen and the edge of the mold frame. Then lay a layer of corner scraps in the mold frame to form the lower epidermal layer of the high-density board. Next, pour the weighed shrinkage material into the mold frame and level the shrinkage material;

[0015] (3) Lay another layer of corner scraps on the surface of the leveled shrinkage material to form the upper epidermal layer of the high-density board;

[0016] (4) Press down the upper platen, control the pressure of the press to be 10 - 12 kg / cm 2 , control the temperature of the upper platen and the lower platen to be 160 - 170 °C, and the heating time to be 30 - 35 min;

[0017] (5) After the heating is completed, cool the upper platen and the lower platen, and take out the pressed board, thus obtaining the high-density board.

[0018] By adopting the above technical solution, the materials remaining in the processing of polyolefin foaming materials are collected, which are the corner scraps. Then the corner scraps are crushed to obtain the crushed material. Then the crushed material is heated, and the heating temperature, heating time and stirring speed are controlled so that the apparent volume of the crushed material shrinks by 60 - 75%, and the apparent density increases by 60 - 75%, that is, the volume of the crushed material shrinks by 60 - 75%, making the volume of the crushed material greatly reduced and the air inside greatly reduced. Furthermore, it makes the crushed material easier to melt, and it is also beneficial to reduce the storage space of the crushed material; then the obtained shrinkage material is pressed. The surface of the shrinkage material obtained by heating softens and has viscosity. And by controlling the pressure, temperature and heating time, the prepared high-density board has better heat preservation performance and higher strength.

[0019] Therefore, in this application, by controlling the heating temperature, heating time and stirring speed of the crushed material, the apparent volume of the crushed material shrinks by 60 - 75%. At the same time, it is also necessary to control the pressure, temperature and heating time for pressing the shrinkage material so that the prepared high-density board has better heat preservation performance and higher strength. And in this application, by recycling the corner scraps remaining in the processing of polyolefin foaming materials to prepare high-density boards, there is no need to remelt the corner scraps, which is beneficial to reducing pollution. And it greatly reduces the storage space of the corner scraps, having high economic benefits.

[0020] Preferably, the particle size of the crushed material is 12 - 16 mm.

[0021] By adopting the above technical solution, if the particle size is too large, the energy consumption required for the apparent volume of the broken material to shrink by 60 - 75% is large. If the particle size is too small, the energy consumption required for the broken material during the crushing process is large. Therefore, using a broken material with a specific range of particle sizes is beneficial for the volume of the broken material to better shrink by 60 - 75% during heating, and further enables the prepared high-density board to have better strength and heat insulation performance.

[0022] Preferably, the scrap material is from the remaining material during the processing of the polyolefin foaming material, and the polyolefin foaming material comprises the following components in parts by mass:

[0023] 55 - 60 parts of EVA; 10 - 20 parts of inorganic flame retardant; 5 - 8 parts of nano-silica; 2 - 4 parts of seaweed stone; 1 - 3 parts of silicate; 0.6 - 1.2 parts of cross-linking agent; 4 - 6 parts of foaming agent.

[0024] By adopting the above technical solution, using EVA as the base material and adding nano-silica, seaweed stone, and silicate, the EVA molecules are adsorbed on the surfaces of nano-silica, seaweed stone, and silicate to form crystal nuclei, which can play a role in heterogeneous nucleation, facilitating the generation of the number of foam cells. Furthermore, during the heating and shrinking process of the scrap material, it is not easy for the density to be too large, resulting in a reduction in the number of closed pores inside the obtained shrinkage material. In this way, the heat insulation performance of the prepared high-density board is not easily affected.

[0025] Preferably, the mass ratio of the nano-silica, seaweed stone, and silicate is 1:(1 - 1.5):2.

[0026] By adopting the above technical solution, using specific ratios of nano-silica, seaweed stone, and silicate in combination is beneficial for promoting the better adsorption of EVA molecules on the surfaces of nano-silica, seaweed stone, and silicate, further promoting the role of heterogeneous nucleation, and further promoting the generation of the number of foam cells, thereby improving the heat insulation performance of the prepared high-density board.

[0027] Preferably, the preparation method of the polyolefin foaming material is as follows:

[0028] S1: Kneading: Mix EVA, inorganic flame retardant, nano-silica, seaweed stone, silicate, cross-linking agent, and foaming agent evenly, and then heat and knead, controlling the kneading temperature at 120 - 135 °C to obtain a mixed material;

[0029] S2: Open milling: Stir, compact, and then extrude and mold the mixed material to form a blank;

[0030] S3: Primary foaming: Add the blank into a mold for mold pressing and foaming, controlling the foaming temperature at 140 - 145 °C and the foaming time at 35 - 45 min to obtain a board material;

[0031] S4: Secondary foaming: Take out the sheet material, trim the four sides (the remaining material after trimming is scrap), add it into the mold for secondary foaming, control the foaming temperature at 160 - 170 °C, the foaming time at 15 - 30 min, cool for 30 - 40 min to form a closed-cell blank, take it out and let it cool, then the polyolefin foamed material is obtained, and then it is cut. The remaining material after cutting is also scrap.

[0032] By adopting the above technical solution, by controlling the crosslinking process and the foaming process of the polyolefin foamed material, the polyolefin foamed material is not prone to excessive crosslinking, and the volume of the broken material can contract more easily by 60 - 75% at a lower temperature, thereby improving the strength of the high-density board.

[0033] Preferably, the crosslinking agent is composed of triallyl isocyanurate and dicumyl peroxide mixed in a mass ratio of 1:(1 - 1.2).

[0034] By adopting the above technical solution, using triallyl isocyanurate and dicumyl peroxide in a specific ratio as the crosslinking agent makes the polyolefin foamed material not prone to insufficient crosslinking. Furthermore, the broken material has sufficient melt strength and is not prone to cracking during the heating and shrinking process, and maintains a closed-cell structure, thereby making the heat preservation performance of the prepared high-density board not easily affected.

[0035] Preferably, the foaming agent is one or more of azodicarbonamide, barium azodicarboxylate, azoaminobenzene, and azodiisobutyronitrile.

[0036] Preferably, the foaming agent is composed of azodicarbonamide and azodiisobutyronitrile mixed in a mass ratio of (0.8 - 1):1.

[0037] By adopting the above technical solution, the foam cells are uniform, fine, and have higher strength, thereby making the high-density board have better heat preservation performance.

[0038] In summary, the present application includes at least one of the following beneficial technical effects:

[0039] 1. By controlling the heating temperature, heating time, and stirring speed of the broken material, the apparent volume of the broken material shrinks by 60 - 75%. At the same time, it is also necessary to control the pressure, temperature, and heating time for pressing the shrunk material, so that the prepared high-density board has good heat preservation performance and high strength. By recycling the scrap left over during the processing of the polyolefin foamed material to prepare a high-density board, there is no need to remelt the scrap, which is beneficial to reducing pollution. Moreover, it greatly reduces the storage space for the scrap and has high economic benefits.

[0040] 2. By using EVA as the base material and adding nano-silica, seaweed stone and silicate, the EVA molecules are adsorbed on the surfaces of nano-silica, seaweed stone and silicate to form crystal nuclei, which can play a role in heterogeneous nucleation, facilitating the generation of the number of pores, and making it less likely that the density of the scraps is too high during the heating and shrinking process, resulting in a reduction in the number of closed pores inside the obtained shrinkage material. Thus, the heat insulation performance of the prepared high-density board is not easily affected.

[0041] 3. By controlling the cross-linking process and the foaming process of the polyolefin foaming material, it is made less likely for the polyolefin foaming material to be over-cross-linked, so that the volume of the crushed material can more easily shrink by 60 - 75% at a lower temperature, thereby improving the strength of the high-density board.

[0042] 4. By using a specific proportion of triallyl isocyanurate and dicumyl peroxide as cross-linking agents, it is made less likely for the polyolefin foaming material to be under-cross-linked. Furthermore, the crushed material has sufficient melt strength and is not easily cracked during the heating and shrinking process, and maintains a closed-cell structure. Thus, the heat insulation performance of the prepared high-density board is not easily affected. Specific embodiments

[0043] The following further elaborates on this application with reference to the embodiments.

[0044] Preparation Example 1

[0045] A preparation method of a polyolefin foaming material is as follows:

[0046] S1: Internal mixing: Mix 55 kg of EVA, 10 kg of inorganic flame retardant, 5 kg of nano-silica, 2 kg of seaweed stone, 1 kg of silicate, 0.6 kg of cross-linking agent and 4 kg of foaming agent evenly, and then heat and internally mix, controlling the internal mixing temperature at 120 °C to obtain a mixed material;

[0047] Among them, the inorganic flame retardant is aluminum hydroxide; the mass ratio of nano-silica, seaweed stone and silicate is 1:1:2; the cross-linking agent is composed of triallyl isocyanurate and dicumyl peroxide mixed in a mass ratio of 1:1; the foaming agent is composed of azodicarbonamide and azodiisobutyronitrile mixed in a mass ratio of 0.8:1;

[0048] S2: Open mixing: Stir, compact and then extrude and mold the mixed material to form a blank;

[0049] S3: Primary foaming: Add the blank into a mold for compression foaming, controlling the foaming temperature at 140 °C and the foaming time at 35 min to obtain a board material;

[0050] S4: Secondary foaming: Take out the sheet material, trim the four sides (the remaining material after trimming is scrap), add it into the mold for secondary foaming, control the foaming temperature at 160 °C, the foaming time at 15 min, cool for 30 min to form a closed-cell blank, take it out and let it cool, then the polyolefin foaming material is obtained. Then cut it according to the actual required size of the sheet. After cutting the required sheet, the remaining material is also scrap.

[0051] Preparation Example 2

[0052] The difference from Preparation Example 1 is:

[0053] A method for preparing a polyolefin foaming material, the steps are as follows:

[0054] S1: Kneading: Mix 60 kg of EVA, 20 g of inorganic flame retardant, 8 kg of nano-silica, 4 kg of seaweed stone, 3 kg of silicate, 1.2 kg of crosslinking agent and 6 kg of foaming agent evenly, and then heat and knead, control the kneading temperature at 135 °C to obtain a mixed material;

[0055] Among them, the inorganic flame retardant is aluminum hydroxide; the mass ratio of nano-silica, seaweed stone and silicate is 1:1.5:2; the crosslinking agent is composed of triallyl isocyanurate and dicumyl peroxide mixed in a mass ratio of 1:1.2; the foaming agent is composed of azodicarbonamide and azodiisobutyronitrile mixed in a mass ratio of 1:1;

[0056] S2: Open milling: Stir, compact and then extrude and mold the mixed material to form a blank;

[0057] S3: Primary foaming: Add the blank into the mold for compression foaming, control the foaming temperature at 145 °C, the foaming time at 45 min to obtain a sheet material;

[0058] S4: Secondary foaming: Take out the sheet material, trim the four sides (the remaining material after trimming is scrap), add it into the mold for secondary foaming, control the foaming temperature at 170 °C, the foaming time at 30 min, cool for 40 min to form a closed-cell blank, take it out and let it cool, then the polyolefin foaming material is obtained. Then cut it according to the actual required size of the sheet. After cutting the required sheet, the remaining material is also scrap.

[0059] Preparation Example 3

[0060] The difference from Preparation Example 2 is: The crosslinking agent is composed of triallyl isocyanurate and dicumyl peroxide mixed in a mass ratio of 1:2.

[0061] Preparation Example 4

[0062] The difference from Preparation Example 2 is: The crosslinking agent is composed of triallyl isocyanurate and dicumyl peroxide mixed in a mass ratio of 2:1.

[0063] Preparation Example 5

[0064] The difference from Preparation Example 2 is that:

[0065] The polyolefin foamed material comprises the following components by mass:

[0066] EVA 50 kg; inorganic flame retardant 7 kg; nano-silica 10 kg; seaweed stone 1 kg; silicate 6 kg; cross-linking agent 0.3 kg; foaming agent 2 kg.

[0067] Preparation Example 6

[0068] The difference from Preparation Example 2 is that nano-silica is not added in S1.

[0069] Preparation Example 7

[0070] The difference from Preparation Example 2 is that seaweed stone is not added in S1.

[0071] Preparation Example 8

[0072] The difference from Preparation Example 2 is that silicate is not added in S1.

[0073] Preparation Example 9

[0074] The difference from Preparation Example 2 is that EVA is replaced with an equal amount of ethylene-octene copolymer.

[0075] Example 1

[0076] This example discloses a preparation method for preparing a high-density board using foamed polyolefin scraps, comprising the following steps:

[0077] Step 1: Collect the scraps in Preparation Example 1;

[0078] Step 2: Heat shrink the scraps

[0079] (1) Place the scraps on the conveyor belt, feed them into the inlet of the crusher, and then crush the scraps to obtain crushed materials with a particle size of 12 mm;

[0080] (2) Use a blower to suck the crushed materials into the mixing barrel, heat the crushed materials with steam, control the heating temperature at 165 °C, stir at a speed of 8 r / min, after the mixing barrel is full, turn off the crusher and the blower, and continue stirring for 40 min. At this time, the volume of the crushed materials shrinks by 60%, that is, shrinkage materials are obtained, and then open the discharge port and bag the shrinkage materials;

[0081] Step 3: Prepare the high-density board

[0082] (1) Weigh 60 kg of the shrinkage materials after heating shrinkage;

[0083] (2) Lift the upper platen into place, evenly apply a release agent on the upper platen, lower platen, and the edges of the mold frame. Then, lay a layer of corner scrap material with a thickness of 3 mm inside the mold frame to form the lower skin layer of the high-density board, increasing the black bed on the surface and making the surface texture clearer. Next, pour the weighed shrinkage material into the mold frame and level the shrinkage material;

[0084] (3) Lay another layer of corner scrap material on the surface of the leveled shrinkage material to form the upper skin layer of the high-density board;

[0085] (4) Lower the upper platen, control the pressure of the press to be 10 kg / cm 2 , control the temperatures of the upper platen and the lower platen to be 160 °C, and the heating time to be 30 min;

[0086] (5) After the pressing is completed, cool the upper platen and the lower platen for 30 min, then lift the upper platen, loosen the mold frame, and take out the pressed board, thus obtaining a 25-mm-thick high-density board.

[0087] Example 2

[0088] The difference from Example 1 is as follows:

[0089] Step 1: Collect the corner scraps in Preparation Example 2;

[0090] Step 2: Heat and shrink the corner scraps

[0091] (1) Place the corner scraps on the conveyor belt and feed them into the inlet of the crusher. Then, crush the corner scraps to obtain crushed material with a particle size of 16 mm;

[0092] (2) Use a blower to suck the crushed material into the mixing drum, heat the crushed material with steam, and control the heating temperature to be 175 °C. Stir at a speed of 10 r / min. After the mixing drum is full, turn off the crusher and the blower, and continue stirring for 60 min. At this time, the volume of the crushed material shrinks by 75%, thus obtaining the shrinkage material. Then, open the discharge port and bag the shrinkage material;

[0093] Step 3: Prepare the high-density board

[0094] (1) Weigh 75 kg of the shrinkage material after heating and shrinking;

[0095] (2) Lift the upper platen into place, evenly apply a release agent on the upper platen, lower platen, and the edges of the mold frame. Then, lay a layer of corner scrap material with a thickness of 3 mm inside the mold frame to form the lower skin layer of the high-density board, increasing the black bed on the surface and making the surface texture clearer. Next, pour the weighed shrinkage material into the mold frame and level the shrinkage material;

[0096] (3) Lay another layer of corner pieces on the surface of the flattened shrinkage material to form the upper skin layer of the high-density board;

[0097] (4) Press down the upper platen, control the pressure of the press to be 12 kg / cm 2 , control the temperature of the upper platen and the lower platen to be 170 °C, and the heating time to be 35 min;

[0098] (5) After the pressing is completed, cool the upper platen and the lower platen for 30 min, then lift the upper platen, loosen the mold frame, and take out the pressed board, thus obtaining a 25-mm-thick high-density board.

[0099] Example 3

[0100] The difference from Example 2 is that in step one, collect the corner materials in Preparation Example 3.

[0101] Example 4

[0102] The difference from Example 2 is that in step one, collect the corner materials in Preparation Example 4.

[0103] Example 5

[0104] The difference from Example 2 is that in step one, collect the corner materials in Preparation Example 6.

[0105] Example 6

[0106] The difference from Example 2 is that in step one, collect the corner materials in Preparation Example 7.

[0107] Example 7

[0108] The difference from Example 2 is that in step one, collect the corner materials in Preparation Example 8.

[0109] Example 8

[0110] The difference from Example 2 is that in step one, collect the corner materials in Preparation Example 9.

[0111] Comparative Example 1

[0112] The difference from Example 2 is that:

[0113] Step two: Heat shrink the corner materials

[0114] (2) Use a blower to suck the crushed materials into the mixing barrel, heat the crushed materials with steam, control the heating temperature to be 150 °C, stir at a speed of 10 r / min, after the mixing barrel is full, turn off the crusher and the blower, and continue to stir for 30 min. At this time, the volume of the crushed materials shrinks by 50%, thus obtaining the shrinkage material, then open the discharge port and bag the shrinkage material.

[0115] Comparative Example 2

[0116] The difference from Example 2 is as follows:

[0117] Step 2: Heating and shrinking of the scrap

[0118] (2) Use a blower to suck the crushed material into the mixing barrel, heat the crushed material with steam, control the heating temperature at 185 °C, stir at a rotation speed of 10 r / min. After the mixing barrel is full, turn off the crusher and the blower, and continue stirring for 70 min. At this time, the volume of the crushed material shrinks by 80%, that is, the shrunk material is obtained. Then open the discharge port and bag the shrunk material.

[0119] Comparative Example 3

[0120] The difference from Example 2 is as follows:

[0121] Step 2: Heating and shrinking of the scrap

[0122] (2) Use a blower to suck the crushed material into the mixing barrel, heat the crushed material with steam, control the heating temperature at 175 °C, stir at a rotation speed of 20 r / min. After the mixing barrel is full, turn off the crusher and the blower, and continue stirring for 60 min. At this time, the volume of the crushed material shrinks by 55%, that is, the shrunk material is obtained. Then open the discharge port and bag the shrunk material.

[0123] Comparative Example 4

[0124] The difference from Example 2 is as follows:

[0125] Step 3: Preparation of high-density board

[0126] (4) Press down the upper pressing plate, control the pressure of the press at 8 kg / cm 2 , the temperature of the hotbed at 150 °C, and the heating time at 20 min.

[0127] Comparative Example 5

[0128] The difference from Example 2 is as follows:

[0129] Step 3: Preparation of high-density board

[0130] (4) Press down the upper pressing plate, control the pressure of the press at 15 kg / cm 2 , the temperature of the hotbed at 180 °C, and the heating time at 40 min.

[0131] Comparative Example 6

[0132] The difference from Example 2 is that in Step 1, the scrap in Preparation Example 5 is collected.

[0133] Experiment 1

[0134] This experiment referred to DIN53479 "Density Detection Standard" to detect the density (g / cm 3 ) of the shrinkage materials obtained in the above-mentioned examples and comparative examples respectively.

[0135] Experiment 2

[0136] This experiment referred to GB / T528 - 2009 "Determination of Tensile Stress - Strain Properties of Vulcanized Rubber or Thermoplastic Rubber" to detect the tensile strength (MPa) of the high - density boards prepared in the above-mentioned examples and comparative examples respectively.

[0137] Experiment 3

[0138] This experiment referred to ASTM D5470 - 2012 "Standard Test Method for Thermal Transmission Properties of Thermal Conductive Electrical Insulating Materials" to detect the thermal conductivity (W / m·K) of the high - density boards prepared in the above-mentioned examples and comparative examples respectively.

[0139] The above experimental results are all shown in Table 1.

[0140] Table 1

[0141]

[0142] According to the comparison between Comparative Example 1 and Example 2 in Table 1, it can be obtained that the density of the shrinkage material obtained in Comparative Example 1 is less than that of the shrinkage material obtained in Example 2, and the tensile strength of the high - density board is lower than that of Example 2. This is because: in Comparative Example 1, the heating time of the crushed material is too short and the temperature is too low, resulting in that the shrinkage material cannot shrink well, and then the volume of the shrinkage material is too large, making the strength of the high - density board vulnerable to influence.

[0143] According to the comparison between Comparative Example 2 and Example 2 in Table 1, it can be obtained that the density of the shrinkage material board obtained in Comparative Example 2 is greater than that of the shrinkage material obtained in Example 2, and the thermal conductivity of the high - density board is higher than that of Example 2. This is because: in Comparative Example 2, the heating time of the crushed material is too long and the temperature is too high, resulting in that the density of the shrinkage material is too large, and then the heat - preservation performance of the prepared high - density board is affected.

[0144] According to the comparison between Comparative Example 3 and Example 2 in Table 1, it can be obtained that the density of the shrinkage material obtained in Comparative Example 3 is less than that of Example 2, and the tensile strength of the high - density board is lower than that of Example 2. This is because: during the heating and shrinking process of the crushed material, the stirring speed is too fast, resulting in that the crushed material cannot absorb heat well, the shrinkage of the crushed material is insufficient, and then the volume of the shrinkage material is too large, with more air remaining inside the shrinkage material and small density, resulting in the prepared high - density board being too thick, thus affecting the strength of the high - density board.

[0145] Comparing Comparative Example 4 with Example 2 in Table 1, it can be seen that the tensile strength of the high-density board in Comparative Example 4 is lower than that in Example 2, and the thermal conductivity is higher than that in Example 2. This is because: during the process of pressing the shrinkage material, the pressure is too small and the pressure holding time is too short, resulting in the tensile strength and heat preservation performance of the high-density board being affected.

[0146] Comparing Comparative Example 5 with Example 2 in Table 1, it can be seen that the tensile strength of the high-density board in Comparative Example 5 is also lower than that in Example 2, and the thermal conductivity is also higher than that in Example 2. This is because: during the process of pressing the shrinkage material, the pressure is too large and the pressure holding time is too long, making it easy for the shrinkage material to be scorched, which in turn affects the structure of the high-density board, thus affecting the tensile strength and heat preservation performance of the high-density board.

[0147] Comparing Comparative Example 6 with Example 2 in Table 1, it can be seen that both the tensile strength and heat preservation performance of the high-density board in Comparative Example 6 are inferior to those in Example 2. This is because: the component ratios of the scraps in Comparative Example 6 are not within the scope of this application. When the collected scraps are heated and shrunk, the density of the scraps is likely to be too high, resulting in a decrease in the number of closed pores inside the obtained shrinkage material, thereby affecting the heat preservation performance of the prepared high-density board.

[0148] In summary, only by simultaneously controlling the heating temperature, heating time, and stirring speed of the crushed material, so that the apparent volume of the crushed material shrinks by 60 - 75%, and at the same time, it is necessary to control the pressure, temperature, and heating time of pressing the shrinkage material, and also, the components and ratios of the scraps need to cooperate synergistically. Only in this way can the prepared high-density board have high heat preservation performance and tensile strength.

[0149] Comparing Example 3 with Example 2 in Table 1, it can be seen that the density of the shrinkage material obtained in Example 3 is less than that in Example 2, and the tensile strength of the prepared high-density board is lower than that in Example 2. This is because: the crosslinking of the polyolefin foaming material is excessive, requiring higher temperature and energy, making it more difficult for the volume of the crushed material to shrink by 60 - 75%, resulting in an excessive volume, thus affecting the strength of the high-density board.

[0150] Comparing Example 4 with Example 2 in Table 1, it can be seen that the density of the shrinkage material obtained in Example 4 is greater than that in Example 2, and the thermal conductivity of the prepared high-density board is higher than that in Example 2. This is because: the crosslinking of the polyolefin foaming material is insufficient, which in turn makes the crushed material unable to have sufficient melt strength, making it easy for the crushed material to crack during the heating and shrinking process, thereby affecting the heat preservation performance of the prepared high-density board.

[0151] Comparing Examples 5-7 with Example 2 in Table 1 respectively, it can be seen that in Example 5, nano-silica was not added, and the tensile strength of the prepared high-density board was lower than that of Example 2; in Example 6, seaweed stone was not added, and the thermal conductivity of the prepared high-density board was higher than that of Example 2; in Example 7, silicate was not added, and the tensile strength of the prepared high-density board was lower than that of Example 2, indicating that the lack of any one of EVA, nano-silica, and seaweed stone will affect the performance of the high-density board.

[0152] In summary, only by using nano-silica, seaweed stone, and silicate in specific proportions and cooperating with each other can the generation of the number of foam cells be promoted. Moreover, by controlling the crosslinking process and the foaming process of the polyolefin foaming material, it is ensured that the polyolefin foaming material is not easily over-crosslinked. At the same time, using triallyl isocyanurate and dicumyl peroxide in specific proportions as crosslinking agents can prevent the polyolefin foaming material from having insufficient crosslinking. The components and the process cooperate synergistically with each other, so that the heat preservation performance and tensile strength of the prepared high-density board are not easily affected.

[0153] The above are all the preferred embodiments of this application. The protection scope of this application is not limited accordingly. Therefore, any equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A preparation method for preparing a high-density board using foamed polyolefin scraps, characterized in that: It includes the following steps: Step 1: Collect scraps; the scraps are from the materials remaining during the processing of polyolefin foaming materials, and the polyolefin foaming materials include the following components in parts by mass: 55 - 60 parts of EVA; 10 - 20 parts of inorganic flame retardant; 5 - 8 parts of nano-silica; 2 - 4 parts of seaweed stone; 1 - 3 parts of silicate; 0.6 - 1.2 parts of cross-linking agent; 4 - 6 parts of foaming agent, and the mass ratio of nano-silica, seaweed stone and silicate is 1:(1 - 1.5):2; Step 2: Heat shrink the scraps (1) Crush the scraps to obtain crushed materials; (2) Pump the crushed materials into a mixing barrel, heat the crushed materials by steam, control the heating temperature at 165 - 175 °C, stir at a speed of 8 - 10 r / min, and the stirring time is 40 - 60 min, so that the volume of the crushed materials shrinks by 60 - 75%, and thus shrinkage materials are obtained; Step 3: Prepare high-density boards (1) Weigh the shrinkage materials after heat shrinkage; (2) Uniformly apply a release agent on the upper pressing plate, lower pressing plate and the edges of the mold frame, then lay a layer of scrap sheet in the mold frame to form the lower epidermal layer of the high-density board, and then pour the weighed shrinkage materials into the mold frame and level the shrinkage materials; (3) Lay another layer of scrap sheet on the surface of the leveled shrinkage materials to form the upper epidermal layer of the high-density board; (4) Press down the upper platen, control the pressure of the press to be 10 - 12 kg / cm 2 , control the temperature of the upper platen and the lower platen to be 160 - 170 °C, and the heating time to be 30 - 35 min; (5) After the heating is completed, cool the upper pressing plate and the lower pressing plate, and take out the pressed board, thus obtaining the high-density board.

2. The preparation method of a high-density board using foamed polyolefin scraps according to claim 1, characterized in that: The particle size of the crushed materials is 12 - 16 mm.

3. The preparation method of a high-density board using foamed polyolefin scraps according to claim 1, characterized in that: The preparation method of the polyolefin foaming material is as follows: S1: Internal mixing: Mix EVA, inorganic flame retardant, nano-silica, seaweed stone, silicate, cross-linking agent and foaming agent evenly, and then heat and internally mix, control the internal mixing temperature at 120 - 135 °C, and thus obtain a mixed material; S2: Open mixing: Stir, compact and then extrude the mixed material to form a blank; S3: Primary foaming: Add the blank into a mold for mold pressing and foaming, control the foaming temperature at 140 - 145 °C, and the foaming time is 35 - 45 min to obtain a board material; S4: Secondary foaming: Take out the board material, add the remaining scraps after trimming the four sides into the mold for secondary foaming, control the foaming temperature at 160 - 170 °C, the foaming time is 15 - 30 min, cool for 30 - 40 min to form a closed-cell blank, take it out and let it cool, thus obtaining the polyolefin foaming material, and then cut it, and the remaining materials after cutting are also scraps.

4. A preparation method for preparing a high-density board using foamed polyolefin scraps according to claim 1, characterized in that: The cross-linking agent is composed of triallyl isocyanurate and dicumyl peroxide mixed in a mass ratio of 1:(1 - 1.2).

5. The preparation method of a high-density board using foamed polyolefin scraps according to claim 1, characterized in that: The foaming agent is one or more of azodicarbonamide, barium azodicarboxylate, azoaminobenzene and azodiisobutyronitrile.

6. The preparation method of a high-density board using foamed polyolefin scraps according to claim 5, characterized in that: The foaming agent is composed of azodicarbonamide and azodiisobutyronitrile mixed in a mass ratio of (0.8 - 1):1.

Images