CN109705537B - Recycling method of demoulding cloth containing epoxy resin - Google Patents
Recycling method of demoulding cloth containing epoxy resin Download PDFInfo
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Abstract
The invention relates to a recycling method of demoulding cloth containing epoxy resin, which is characterized in that granules prepared from the demoulding cloth containing the epoxy resin and branched polyester granules are uniformly mixed and then are melted, extruded and foamed, wherein the structural formula of the branched polyester is shown as a formula (I), and specifically comprises the following steps:
in the formula, R1、R2、R3And R4At least three of them have a structural formula shown in formula (II), and the rest are-H, and the formula (II) is as follows:
Description
Technical Field
The invention belongs to the technical field of demolding cloth recycling, and relates to a recycling method of demolding cloth containing epoxy resin.
Background
Wind power generation is an important development direction of clean energy, wherein in the manufacturing process of the wind power blade, workers often use high-strength fiber cloth, namely demolding cloth which takes high-molecular polymers such as polyester and the like as a matrix and is cured and formed by epoxy resin in the matrix as disposable demolding cloth, so that a large amount of resource waste is caused, and therefore, the recycling of the demolding cloth containing the epoxy resin is an important link of resource saving.
Although theoretically, the epoxy resin on the release fabric is removed and reused as an effective method, the method is technically difficult on one hand, and on the other hand, energy and reagents are consumed, so that resource waste and environmental pollution are caused.
At present, many documents disclose methods for recycling polyester cloth, for example, a research on reactive extrusion modification and microcellular foaming of polyester PET [ D ] of great eastern university of china: 2014.1-66 ] in document 1 (Yuan sea. polyester PET) discloses a method for improving the molecular weight of recycled polyester by a method combining chain extension and tackifying, but the method has the advantages of long technical route, complex process and high cost.
Patent CN 104817830a discloses an aromatic polyester microcellular foam material and a preparation method thereof, which is prepared by foaming an aromatic polyester composition mainly comprising aromatic polyester, sorbierite benzylidene derivatives, an antioxidant, a chain extender and a nucleating agent. Patent CN107057303A discloses a blending modified aromatic polyester microcellular foam material and a preparation method thereof, wherein the foam material is prepared by foaming an aromatic composition mainly comprising aromatic polyester, polyamide, a polyfunctional epoxy group chain extender, a cell nucleating agent and an antioxidant through a foaming process. However, the method mainly utilizes the aromatic polyester to prepare the foaming material, the application range is narrow, the mechanical property of the prepared foaming material is general, the highest tensile strength can reach 22MPa, and the mechanical property is still to be improved. The prior art documents disclosed do not relate to recycling of epoxy resin-containing release cloth, and the difficulty of recycling epoxy resin-containing release cloth is that the matrix of the release cloth is thermoplastic polyester, the attached epoxy resin is thermosetting, and the thermosetting epoxy resin is dispersed as particles in the polyester to form a two-phase unstable system and is easy to fall off, thereby affecting the quality of the recycled product.
Therefore, it is very important to develop a method for recycling an epoxy resin-containing release fabric in which an epoxy resin is stably dispersed in a matrix.
Disclosure of Invention
The present invention has been made to overcome the above-mentioned problems of the prior art, and an object of the present invention is to provide a method for recycling an epoxy resin-containing release fabric which can stably disperse an epoxy resin in a matrix.
In order to achieve the purpose, the invention adopts the technical scheme that:
the method for recycling the demoulding cloth containing the epoxy resin comprises the following steps of uniformly mixing granules prepared from the demoulding cloth containing the epoxy resin with branched polyester granules, and then melting, extruding and foaming;
the structural formula of the branched polyester is shown as a formula (I), and the structure formula is as follows:
in the formula, R1、R2、R3And R4At least three of them have a structural formula shown in formula (II), and the rest are-H, and the formula (II) is as follows:
wherein n is 25 to 50.
According to the invention, the demolding cloth containing the epoxy resin is blended with the branched polyester to realize the recycling of the demolding cloth containing the epoxy resin, the branched polyester contains rich hydroxyl groups, and the branched polyester can simultaneously react with the polyester and the epoxy resin in the demolding cloth containing the epoxy resin to play a role of a cross-linking agent, and the epoxy resin is connected with the polyester through a chemical bond, so that the epoxy resin particles in the demolding cloth are not easy to fall off, and the thermoplastic epoxy resin can be stably dispersed in the matrix material.
As a preferred technical scheme:
according to the method for recycling the demoulding cloth containing the epoxy resin, the mass content of the epoxy resin in the demoulding cloth containing the epoxy resin is less than or equal to 10 percent, and the content of the epoxy resin in the demoulding cloth is less than or equal to 10 percent, so that the method is favorable for melt extrusion after the granules of the demoulding cloth and the branched polyester are blended, and is favorable for ensuring the smooth operation of a foaming process; wherein, the content of epoxy groups on the surface of the epoxy resin is more than or equal to 104Per mm2The mechanical property of the foaming material is ensured;
according to the method for recycling the demolding cloth containing the epoxy resin, the component with the highest content in the demolding cloth containing the epoxy resin is the polyester, the intrinsic viscosity of the polyester is 0.9-1.10 dL/g, the intrinsic viscosity is in the range, so that the strength of a blended melt in the melting extrusion process is guaranteed, the raw material is not required to be tackified and can be directly used for foaming, and the base material of the demolding cloth provided by the invention comprises but is not limited to the polyester, and the polyester is preferably used as the demolding cloth base mainly because the branched polyester and the polyester base have good compatibility and terminal carboxyl contained in the polyester can also react with the branched polyester, so that the strength and the stability of the blended melt are improved, and the quality and the mechanical property of a recovered product of the demolding cloth are improved;
the content of the terminal carboxyl groups is 15-20 mol/ton, the content of the terminal carboxyl groups of the polyester is preferably 15-20 mol/ton, the smooth melt extrusion of the blend of the demolding cloth granules and the branched polyester granules can be ensured, and the mechanical property of the foaming material can be improved, the content of the terminal carboxyl groups in the polyester comprises but is not limited to the content, the terminal carboxyl groups can be properly adjusted, but is not too high, the content of the terminal carboxyl groups is too low, the cross-linking points formed by the polyester and the branched polyester in the demolding cloth are too few, the strength of the blended melt is low, the mechanical property of the recovered foaming material is poor, the practical value of the recovered product is low, the content of the terminal carboxyl groups is too high, the cross-linking points formed by the polyester and the branched polyester in the demolding cloth are too many, the melt extrusion of the blend of the demolding cloth granules.
The method for recycling the release fabric containing the epoxy resin comprises the following steps: firstly, mixing and pulping ethylene glycol and terephthalic acid, then carrying out esterification reaction and polycondensation reaction to obtain polyester with average polymerization degree n of 25-50 and terminal carboxyl group content of 150-280 mol/ton, wherein the polymerization degree is relatively low, the terminal carboxyl group content is high, the reactivity with pentaerythritol is improved, then adding the polyester and pentaerythritol into a double-screw extruder, carrying out melt blending, extruding and granulating, wherein the mass ratio of the pentaerythritol to the polyester is 0.3-1.0: 100, finally generating branched polyester as a long chain, and on one hand, the branched polyester can react with epoxy and a polyester matrix in the subsequent utilization process, but the cross-linking point is few, and the extrusion is not influenced.
The method for recycling the demoulding cloth containing the epoxy resin comprises the steps of (1) enabling the molar ratio of ethylene glycol to terephthalic acid to be 1.05-1.1: 1; the temperature of the esterification reaction is 230-250 ℃, the time is 1-2 h, and the pressure is 0.1-0.3 MPa; the temperature of the polycondensation reaction is 265-285 ℃, the time is 20-40 min, and the vacuum degree is 100-200 Pa; the temperature of the melt blending is 270-280 ℃, and the time is 5-15 min.
In the method for recycling the epoxy resin-containing release cloth, the branched polyester pellets account for 1 to 5wt% of the total mass of the pellets prepared from the epoxy resin-containing release cloth and the branched polyester pellets. The preferable weight percentage of the branched polyester granules is 1-5 wt%, which can ensure the smooth melt extrusion of the blend of the demoulded cloth granules and the branched polyester granules and improve the mechanical property of the foaming material, the addition amount of the branched polyester granules includes but is not limited to the above, the addition amount can be properly adjusted, but is not too large, the addition amount is too low, the cross-linking points formed by the branched polyester and the polyester in the demoulded cloth are too few, the strength of the blended melt is low, the mechanical property of the recycled foaming material is poor, the practical value of the recycled product is low, the addition amount is too high, the cross-linking points formed by the branched polyester and the polyester in the demoulded cloth are too many, the smooth extrusion of the blended melt of the demoulded cloth granules and the branched polyester granules is.
The method for recycling the release cloth containing the epoxy resin comprises the following specific steps:
(1) mechanically crushing the demoulding cloth containing the epoxy resin, wherein the method and conditions are not limited, and obtaining demoulding cloth powder when the average grain diameter of the epoxy resin is less than 10 mu m;
(2) melting and granulating the demoulding cloth powder at 270-290 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin, wherein the epoxy resin is not melted and is dispersed in the granules;
(3) respectively drying the granules prepared from the release cloth containing the epoxy resin and the branched polyester granules until the moisture content is lower than 100ppm, wherein the method and the conditions are not limited;
(4) melting granules prepared from demolding cloth containing epoxy resin and branched polyester granules at 285-305 ℃ to obtain a mixture, and then performing supercritical foaming to obtain a foaming material, wherein the supercritical foaming is a physical foaming technology and a microcellular foaming technology, in the processes of injection molding, extrusion and blow molding, firstly injecting other gases such as carbon dioxide or nitrogen in a supercritical state into a special plasticizing device, fully and uniformly mixing/diffusing the gases and the molten raw materials to form single-phase mixed sol, then performing melt extrusion through a plate molding die, and rapidly reducing pressure in a cooling and shaping process to continuously form bubble nuclei in the sol, thereby finally obtaining the polyester microcellular foaming plate; in the extrusion foaming process, hydroxyl of the branched polyester reacts with epoxy groups in the epoxy resin and terminal carboxyl of the polyester, solid granular epoxy groups are fixed and cannot fall off, and meanwhile, the branched polyester reacts with only a small amount of terminal carboxyl of the polyester to generate a small amount of crosslinking points, so that the extrusion is not influenced, and the melt strength in the foaming process is improved.
In the method for recycling the epoxy resin-containing release fabric, the foaming agent used for supercritical foam molding is carbon dioxide or nitrogen in a supercritical state, and the amount of the foaming agent is 0.1-8% of the total weight of the pellets prepared from the epoxy resin-containing release fabric and the branched polyester pellets.
The method for recycling the demoulding cloth containing the epoxy resin comprises the steps of enabling the compression strength of the foaming material to be 1-3 MPa, the shearing strength to be 0.5-1.0 MPa, the tensile strength to be 1.5-3 MPa and the apparent density to be 80-120 Kg/m3The diameter of the foam hole is 10-100 μm.
The invention mechanism is as follows:
the invention relates to a recycling method of demoulding cloth containing epoxy resin, which is characterized in that granules prepared from the demoulding cloth containing the epoxy resin and branched polyester granules are uniformly mixed and then are melted, extruded and foamed, wherein the structural formula of the branched polyester is as follows:
in the formula, R1、R2、R3And R4At least three of them have a structural formula shown in formula (II), and the rest are-H, and the formula (II) is as follows:
wherein n is 25 to 50;
r in the branched polyester with the structural formula of formula (II)1、R2、R3Or R4The hydroxyl group in (A) is capable of reacting with an epoxy group in the epoxy resin on the one hand and R on the other hand1、R2、R3Or R4The hydroxyl in the polyester resin can also react with terminal carboxyl in the polyester matrix of the demolding cloth, which is equivalent to a cross-linking agent between the polyester matrix of the demolding cloth and the epoxy resin, so that the falling of thermoplastic epoxy resin particles is effectively prevented, the strength of a blending melt of demolding cloth particles and branched polyester particles is improved, and the mechanical property of the foaming material is improved.
Has the advantages that:
(1) the method for recycling the demoulding cloth containing the epoxy resin is simple to operate, saves resources and energy, and does not generate new pollutants;
(2) according to the method for recycling the demoulding cloth containing the epoxy resin, the recycled demoulding cloth is high molecular weight polyester, does not need to be tackified and can be directly used for foaming;
(3) according to the method for recycling the demoulding cloth containing the epoxy resin, long-chain branched polyester is used as an additive in the foaming process, and chemical reaction is utilized to form chemical bonds with the epoxy resin and a matrix, so that epoxy resin particles are prevented from falling off, the compatibility with the matrix is good, the melt strength is improved, and the stability of a foaming material is improved.
Detailed Description
The invention will be further illustrated with reference to specific embodiments. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.
The structural formula of the branched polyester is shown as the formula (I), and the structure formula is as follows:
in the formula, R1、R2、R3And R4At least three of them have a structural formula shown in formula (II), and the rest are-H, and the formula (II) is as follows:
wherein n is 25 to 50.
Example 1
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing ethylene glycol and terephthalic acid according to a molar ratio of 1.1:1, pulping, performing esterification reaction for 2h at a temperature of 250 ℃ and a pressure of 0.3Mpa, performing polycondensation reaction for 40min at a temperature of 285 ℃, a time of 40min and a vacuum degree of 200pa to obtain polyester with an average degree of polymerization n of 50 and a terminal carboxyl group content of 150 mol/ton, adding the polyester and pentaerythritol into a double-screw extruder according to a mass ratio of 100:0.3, performing melt blending at a temperature of 280 ℃ for 15min, and extruding and pelletizing to obtain branched polyester pellets, wherein the branched polyester has a structural formula shown in formula (I) in which R is shown in formula (I), and the branched polyester pellets are obtained1、R2、R3And R4The structural formula is shown as formula (II), and n is 50;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 1.1dL/g, the content of terminal carboxyl groups is 15 mol/ton, the mass content of the epoxy resin in the demoulding cloth is 8 percent, and the content of epoxy groups on the surface of the epoxy resin isIs 104Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 8 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at the temperature of 280 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 90 ppm;
(5) the method comprises the steps of melting granules prepared from a release cloth containing epoxy resin and branched polyester granules at 285 ℃ to obtain a mixture, and then carrying out supercritical foaming molding to obtain a foaming material, wherein a foaming agent used in the supercritical foaming molding is carbon dioxide in a supercritical state, the dosage of the foaming agent is 0.1% of the total weight of the granules prepared from the release cloth containing epoxy resin and the branched polyester granules, and the branched polyester granules account for 1 wt% of the total weight of the granules prepared from the release cloth containing epoxy resin and the branched polyester granules.
The finally prepared foaming material has the compression strength of 1MPa, the shear strength of 0.5MPa, the tensile strength of 1.5MPa and the apparent density of 80Kg/m3The diameter of the foam hole is 10-29 μm.
Example 2
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing ethylene glycol and terephthalic acid according to a molar ratio of 1.05:1, pulping, performing esterification reaction for 1h at a temperature of 230 ℃ and a pressure of 0.1MPa, performing polycondensation reaction for 20min at a temperature of 265 ℃, a time of 20min and a vacuum degree of 100pa to obtain polyester with an average degree of polymerization n of 25 and a terminal carboxyl group content of 280 mol/ton, adding the polyester and pentaerythritol into a double-screw extruder according to a mass ratio of 100:0.5, performing melt blending at a temperature of 270 ℃ for 5min, and performing extrusion and granulation to obtain branched polyester granules, wherein the structural formula of the branched polyester is shown as formula (I), and in the formula (I), R is R1、R2And R3The structural formula of the compound is shown as a formula (II),R4is-H, n ═ 25;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 0.9dL/g, the content of terminal carboxyl groups is 20 mol/ton, the mass content of the epoxy resin in the demoulding cloth is 10 percent, and the content of epoxy groups on the surface of the epoxy resin is 2 multiplied by 104Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 5 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at 290 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 90 ppm;
(5) the method comprises the steps of melting granules prepared from demolding cloth containing epoxy resin and branched polyester granules at 290 ℃ to obtain a mixture, and then carrying out supercritical foaming molding to obtain a foaming material, wherein a foaming agent used in the supercritical foaming molding is carbon dioxide in a supercritical state, the dosage of the foaming agent is 1.2% of the total weight of the granules prepared from the demolding cloth containing epoxy resin and the branched polyester granules, and the branched polyester granules account for 2 wt% of the total weight of the granules prepared from the demolding cloth containing epoxy resin and the branched polyester granules.
The finally prepared foam material has the compression strength of 1.2MPa, the shear strength of 0.65MPa, the tensile strength of 1.8MPa and the apparent density of 88Kg/m3The diameter of the foam hole is 25-42 μm.
Example 3
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing ethylene glycol and terephthalic acid at a molar ratio of 1.05:1, pulping, performing esterification reaction at 235 deg.C and 0.2Mpa for 1.5h, and performing polycondensation reaction at 270 deg.C for 25min and at vacuum degree of 120pa for 25min to obtain average polyPolyester with the degree of polymerization n of 30 and the content of terminal carboxyl groups of 250 mol/ton, finally adding the polyester and pentaerythritol into a double-screw extruder according to the mass ratio of 100:0.65, melting and blending for 7min at the temperature of 272 ℃, extruding and pelletizing to obtain branched polyester pellets, wherein the structural formula of the branched polyester is shown as the formula (I), in the formula (I), R is1、R2And R3Has a structural formula shown as a formula (II), R4is-H, n is 30;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 0.95dL/g, the content of terminal carboxyl groups is 18 mol/ton, the mass content of the epoxy resin in the demoulding cloth is 10 percent, and the content of epoxy groups on the surface of the epoxy resin is 1.5 multiplied by 104Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 8 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at 275 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 90 ppm;
(5) the granules prepared from the release cloth containing the epoxy resin and the branched polyester granules are melted at the temperature of 293 ℃ to obtain a mixture, and then the mixture is subjected to supercritical foaming molding to obtain a foaming material, wherein a foaming agent used for the supercritical foaming molding is carbon dioxide in a supercritical state, the dosage of the foaming agent is 2.5 percent of the total weight of the granules prepared from the release cloth containing the epoxy resin and the branched polyester granules, and the branched polyester granules account for 3.2 percent of the total weight of the granules prepared from the release cloth containing the epoxy resin and the branched polyester granules.
The finally prepared foaming material has the compression strength of 1.5MPa, the shear strength of 0.73MPa, the tensile strength of 2.0MPa and the apparent density of 94Kg/m3The diameter of the foam hole is 41-59 μm.
Example 4
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing and pulping ethylene glycol and terephthalic acid according to a molar ratio of 1.08:1, performing esterification reaction for 1.5h at a temperature of 240 ℃ and a pressure of 0.15MPa, performing polycondensation reaction for 30min at a temperature of 275 ℃, a time of 30min and a vacuum degree of 150pa to obtain polyester with an average degree of polymerization n of 35 and a terminal carboxyl group content of 220 mol/ton, adding the polyester and pentaerythritol into a double-screw extruder according to a mass ratio of 100:0.68, performing melt blending at a temperature of 275 ℃ for 10min, and performing extrusion and granulation to obtain branched polyester granules, wherein the structural formula of the branched polyester is shown as formula (I), and in the formula (I), R is R1、R2And R3Has a structural formula shown as a formula (II), R4is-H, n is 35;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 1.0dL/g, the content of terminal carboxyl groups is 16 mol/ton, the mass content of the epoxy resin in the demoulding cloth is 8 percent, and the content of epoxy groups on the surface of the epoxy resin is 1.5 multiplied by 104Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 8 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at the temperature of 280 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 95 ppm;
(5) the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets are melted at the temperature of 295 ℃ to obtain a mixture, and then the mixture is subjected to supercritical foaming molding to obtain a foaming material, wherein a foaming agent used in the supercritical foaming molding is nitrogen in a supercritical state, the dosage of the foaming agent is 3.9% of the total weight of the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets, and the branched polyester pellets account for 3.8 wt% of the total weight of the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets.
The finally prepared foaming material has the compression strength of 2.2MPa, the shear strength of 0.85MPa, the tensile strength of 2.3MPa and the apparent density of 103Kg/m3The diameter of the foam hole is 57-70 μm.
Example 5
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing and pulping ethylene glycol and terephthalic acid according to a molar ratio of 1.08:1, performing esterification reaction for 1.5h at a temperature of 240 ℃ and a pressure of 0.25MPa, performing polycondensation reaction for 30min at a temperature of 270 ℃, a time of 35min and a vacuum degree of 150pa to obtain polyester with an average polymerization degree n of 38 and a terminal carboxyl group content of 190 mol/ton, adding the polyester and pentaerythritol into a double-screw extruder according to a mass ratio of 100:0.72, performing melt blending at a temperature of 275 ℃ for 12min, and performing extrusion and granulation to obtain branched polyester granules, wherein the structural formula of the branched polyester is shown as formula (I), and in the formula (I), R is R1、R2And R4The structural formula is shown as a formula (II), R3is-H, n is 38;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 1.05dL/g, the content of terminal carboxyl groups is 16 mol/ton, the mass content of the epoxy resin in the demoulding cloth is 8 percent, and the content of epoxy groups on the surface of the epoxy resin is 1.1 multiplied by 104Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 8 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at the temperature of 280 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 95 ppm;
(5) the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets are melted at the temperature of 298 ℃ to obtain a mixture, and then the mixture is subjected to supercritical foaming molding to obtain a foaming material, wherein a foaming agent used in the supercritical foaming molding is nitrogen in a supercritical state, the dosage of the foaming agent is 5.3% of the total weight of the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets, and the branched polyester pellets account for 4.0 wt% of the total weight of the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets.
The finally prepared foaming material has the compression strength of 2.4MPa, the shear strength of 0.91MPa, the tensile strength of 2.5MPa and the apparent density of 109Kg/m3The diameter of the foam hole is 70-88 μm.
Example 6
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing ethylene glycol and terephthalic acid according to a molar ratio of 1.1:1, pulping, performing esterification reaction for 2h at a temperature of 240 ℃ and a pressure of 0.3Mpa, performing polycondensation reaction for 35min at a temperature of 280 ℃, a time of 35min and a vacuum degree of 180pa to obtain polyester with an average degree of polymerization n of 42 and a terminal carboxyl group content of 180 mol/ton, adding the polyester and pentaerythritol into a double-screw extruder according to a mass ratio of 100:0.85, performing melt blending at a temperature of 275 ℃ for 12min, and performing extrusion and granulation to obtain branched polyester granules, wherein the structural formula of the branched polyester is shown as formula (I), and in the formula (I), R is R1、R2、R3And R4The structural formula is shown as formula (II), and n is 42;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 1.10dL/g, the content of terminal carboxyl groups is 15 mol/ton, the mass content of the epoxy resin in the demoulding cloth is 10 percent, and the content of epoxy groups on the surface of the epoxy resin is 1.3 multiplied by 104Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 7 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at 290 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 95 ppm;
(5) the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets are melted at the temperature of 302 ℃ to obtain a mixture, and then the mixture is subjected to supercritical foaming molding to obtain a foaming material, wherein a foaming agent used in the supercritical foaming molding is nitrogen in a supercritical state, the dosage of the foaming agent is 7.7 percent of the total weight of the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets, and the branched polyester pellets account for 4.5 percent of the total weight of the pellets prepared from the release cloth containing the epoxy resin and the branched polyester pellets.
The finally prepared foaming material has the compression strength of 2.6MPa, the shear strength of 0.96MPa, the tensile strength of 2.8MPa and the apparent density of 111Kg/m3The diameter of the foam hole is 76-91 μm.
Example 7
A method for recycling release cloth containing epoxy resin comprises the following steps:
(1) preparing branched polyester granules;
mixing ethylene glycol and terephthalic acid according to a molar ratio of 1.1:1, pulping, performing esterification reaction for 2h at a temperature of 250 ℃ and a pressure of 0.2MPa, performing polycondensation reaction for 40min at a temperature of 280 ℃, a time of 35min and a vacuum degree of 200Pa to obtain polyester with an average degree of polymerization n of 47 and a terminal carboxyl group content of 160 mol/ton, adding the polyester and pentaerythritol into a double-screw extruder according to a mass ratio of 100:1.0, performing melt blending at a temperature of 280 ℃ for 12min, and performing extrusion and granulation to obtain branched polyester granules, wherein the structural formula of the branched polyester is shown as formula (I), and in the formula (I), R is R1、R2、R3And R4The structural formula of (I) is shown as formula (II), and n is 47;
(2) taking a demoulding cloth containing epoxy resin, wherein the demoulding cloth containing the epoxy resin mainly comprises a polyester matrix and the epoxy resin dispersed in the polyester matrix, the intrinsic viscosity of the polyester is 1.10dL/g, and the carboxyl end groupsThe content of the base is 15 mol/ton, the mass content of the epoxy resin in the release cloth is 10 percent, and the content of the epoxy group on the surface of the epoxy resin is 10 percent4Per mm2Mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is 6 mu m to obtain demoulding cloth powder;
(3) melting and granulating the demoulding cloth powder at the temperature of 280 ℃ to obtain granules prepared from demoulding cloth containing epoxy resin;
(4) separately drying pellets prepared from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of 95 ppm;
(5) the method comprises the steps of melting granules prepared from a release cloth containing epoxy resin and branched polyester granules at the temperature of 305 ℃ to obtain a mixture, and then carrying out supercritical foaming molding to obtain a foaming material, wherein a foaming agent used in the supercritical foaming molding is carbon dioxide in a supercritical state, the dosage of the foaming agent is 8% of the total weight of the granules prepared from the release cloth containing epoxy resin and the branched polyester granules, and the branched polyester granules account for 5wt% of the total weight of the granules prepared from the release cloth containing epoxy resin and the branched polyester granules.
The finally prepared foaming material has the compression strength of 3MPa, the shear strength of 1.0MPa, the tensile strength of 3MPa and the apparent density of 120Kg/m3The diameter of the foam hole is 83-100 μm.
Claims (7)
1. A method for recycling a release fabric containing epoxy resin, which is characterized by comprising the following steps: uniformly mixing granules prepared from the demoulding cloth containing epoxy resin with branched polyester granules, and then melting, extruding and foaming;
the method comprises the following specific steps:
(1) mechanically crushing the demoulding cloth containing the epoxy resin until the average grain diameter of the epoxy resin is less than 10 mu m to obtain demoulding cloth powder;
(2) melting and granulating the demolding cloth powder at 270-290 ℃ to obtain granules prepared from the demolding cloth containing epoxy resin;
(3) separately drying pellets made from a release fabric containing an epoxy resin and branched polyester pellets to a moisture content of less than 100 ppm;
(4) melting granules prepared from a release fabric containing epoxy resin and branched polyester granules at the temperature of 285-305 ℃ to obtain a mixture, and performing supercritical foaming molding to obtain a foaming material;
the structural formula of the branched polyester is shown as a formula (I), and the structure formula is as follows:
(I)
in the formula, R1、R2、R3And R4At least three of them have a structural formula shown in formula (II), and the rest are-H, and the formula (II) is as follows:
(II)
wherein n = 25-50;
the preparation method of the branched polyester granules comprises the following steps: firstly, mixing and pulping ethylene glycol and terephthalic acid, then carrying out esterification reaction and polycondensation reaction to obtain polyester with the average polymerization degree n of 25-50 and the terminal carboxyl group content of 150-280 mol/ton, then adding the polyester and pentaerythritol into a double-screw extruder, and extruding and granulating after melt blending, wherein the mass ratio of the pentaerythritol to the polyester is 0.3-1.0: 100.
2. The method for recycling the epoxy resin-containing release fabric according to claim 1, wherein the epoxy resin content in the epoxy resin-containing release fabric is 10% by mass or less, and the epoxy group content on the surface of the epoxy resin is 10% by mass or more4Per mm2。
3. The method for recycling the epoxy resin-containing release fabric according to claim 1, wherein the epoxy resin-containing release fabric contains a polyester as a component having a highest content, an intrinsic viscosity of 0.9 to 1.10dL/g, and a carboxyl end group content of 15 to 20 mol/ton.
4. The method for recycling the epoxy resin-containing release fabric according to claim 1, wherein the molar ratio of ethylene glycol to terephthalic acid is 1.05 to 1.1: 1; the temperature of the esterification reaction is 230-250 ℃, the time is 1-2 h, and the pressure is 0.1-0.3 MPa; the temperature of the polycondensation reaction is 265-285 ℃, the time is 20-40 min, and the vacuum degree is 100-200 Pa; the temperature of the melt blending is 270-280 ℃, and the time is 5-15 min.
5. The method for recycling a releasing fabric containing an epoxy resin as claimed in claim 1, wherein the branched polyester pellets account for 1 to 5wt% of the total mass of the pellets produced from the releasing fabric containing an epoxy resin and the branched polyester pellets.
6. The method for recycling epoxy resin-containing release fabric according to claim 1, wherein the foaming agent used for the supercritical foam molding is carbon dioxide or nitrogen in a supercritical state, and the amount of the foaming agent is 0.1 to 8% by weight based on the total weight of the pellets made of the epoxy resin-containing release fabric and the branched polyester pellets.
7. The method for recycling the epoxy resin-containing release fabric according to claim 6, wherein the foam has a compressive strength of 1 to 3MPa, a shear strength of 0.5 to 1.0MPa, a tensile strength of 1.5 to 3MPa, and an apparent density of 80 to 120Kg/m3The diameter of the foam hole is 10-100 μm.
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| EP3283545A1 (en) * | 2015-04-14 | 2018-02-21 | Resinate Materials Group, Inc. | Polyester polyols with increased clarity |
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