NPG-PETG / polyethylene blending material and production process thereof

Abstract

The invention belongs to the technical field of polymer materials, and particularly relates to an NPG-PETG / polyethylene blending material and a production process thereof.The method comprises the steps that S1, r-PET is cut into pieces and then put into a depolymerization kettle, MEG / NPG mixed liquor and terephthalic acid are added into the depolymerization kettle, nitrogen is introduced for protection, and heating and stirring reaction are conducted to generate intermediate feed liquid; s2, pumping the intermediate material liquid into a polymerization reaction kettle, decanting to remove unreacted raw materials, adding a polymerization catalyst and a stabilizer into the polymerization reaction kettle, heating and pressurizing to carry out polymerization reaction, and after the reaction is finished, extruding and cooling to obtain r-PETG; and S3, respectively drying the r-PETG material and the polyethylene material, adding into a mixing tank, adding a compatilizer and an antioxidant into the mixing tank, mixing, feeding into a double-screw extruder for extrusion, and then carrying out water-cooling granulation and drying. The polyethylene material modified by the ethylene-acrylic acid copolymer and the maleic anhydride is used as the mixed compatilizer, so that the compatibility of the two materials is greatly improved, and the blended material is endowed with better impact resistance and toughness.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to an NPG-PETG / polyethylene blend material and a production process thereof. Background Art

[0002] PETG is short for polyethylene terephthalate-1,4-cyclohexanedimethanol ester. It is a new type of copolyester obtained by modifying PET by using 1,4-cyclohexanedimethanol (CHDM) as a comonomer raw material to partially replace ethylene glycol (EG). Its most prominent application field is the preparation of heat-shrinkable films, and the shrinkage rate can be as high as more than 70%. It belongs to an environmentally friendly product that can be recycled. Ordinary PETG still has certain crystallization behavior, which causes difficulties in film processing, and the modified component CHDM is relatively expensive, which has obvious limitations in large-scale industrial applications. Therefore, researchers proposed to use neopentyl glycol (NPG) to replace CHDM to prepare polyethylene terephthalate-neopentyl glycol ester (NPG-PETG) to reduce production costs.

[0003] In the prior art, for example, Chinese Patent CN102558517A provides an ecological multifunctional terpolymerized PETG polyester, its production process, and a method for preparing a unidirectionally stretched heat-shrinkable film from the polyester. It is copolymerized from terephthalic acid, neopentyl glycol, and ethylene glycol monomers, and the molar ratio of terephthalic acid, neopentyl glycol, and ethylene glycol is 1∶(0.1-0.65)∶(1.2-1.75). The production process includes an esterification reaction and a polymerization reaction. The temperature of the esterification reaction is 200°C-255°C, the temperature of the polymerization reaction is 270°C-280°C, and the vacuum degree of the polymerization reaction is 0.098MPa-0.1MPa. Thus, the prepared PETG polyester has a complete structure and high strength, and can meet the use requirements of high-quality heat-shrinkable films.

[0004] Another example is that Chinese Patent CN110790907A in the prior art provides a production equipment and process flow of all-continuous PETG. By using NPG to replace CHDM, PETG is continuously produced, and a PETG product with a viscosity that can meet higher requirements is prepared through the cooperation of the equipment and the process.

[0005] The PETG materials produced by the above prior art use NPG to replace CHDM, resulting in poor toughness of the products, easy embrittlement of the products, poor impact resistance, and unstable heat-shrinkage performance. Therefore, they can only be applied to low-end shrink films and label films and cannot meet the use requirements of bottle materials and high-end packaging materials. Summary of the Invention

[0006] In view of the problems mentioned in the background art, the present invention provides an NPG-PETG / polyethylene blend material and its production process. By first depolymerizing recycled r-PET and then preparing it into r-PETG containing NPG, the intrinsic viscosity of r-PETG is improved. Through blending with polyethylene materials, the toughness and impact resistance of PETG materials can be significantly improved under the action of a mixed compatibilizer, meeting the usage requirements of high-end packaging materials and bottle materials.

[0007] The present invention provides a production process for an NPG-PETG / polyethylene blend material, and the method includes the following steps:

[0008] S1. Cut r-PET into pieces and put them into a depolymerization kettle, then add a MEG / NPG mixed solution and terephthalic acid thereto, fill with nitrogen for protection, heat up and stir to react to generate an intermediate liquid;

[0009] S2. Pump the intermediate liquid into a polymerization reactor, decant to remove unreacted raw materials, then add a polymerization catalyst and a stabilizer to the polymerization reactor, heat up and pressurize for polymerization reaction, and after the reaction is completed, extrude and cool to obtain r-PETG;

[0010] S3. Dry the r-PETG material and the polyethylene material respectively and add them to a mixing tank, then add a compatibilizer and an antioxidant to the mixing tank, mix and send them to a twin-screw extruder for extrusion, and then water-cool and pelletize and dry.

[0011] Further, in step S1, the mass ratio of terephthalic acid and the MEG / NPG mixed solution to r-PET is 0.25 - 0.5:1:10 - 20; the weight ratio of MEG:NPG in the MEG / NPG mixed solution is 2 - 6:1.

[0012] Further, in step S1, the reaction temperature is 200 - 250 °C, the reaction pressure is 1 - 2 MPa, and the reaction time is 120 - 160 minutes.

[0013] Further, the content of free MEG in the intermediate liquid is 13% - 15% of the total amount of the intermediate liquid, and the content of free NPG is 8% - 10% of the total amount of the intermediate liquid.

[0014] Further, in step S2, the reaction temperature of the polymerization reactor is 250 - 290 °C, and the vacuum degree is 50 - 100 Pa.

[0015] Further, in step S2, the stabilizer is a phosphate compound stabilizer, and the addition amount is 0.8 - 1% of the mass of r-PET fragments; the polymerization catalyst is one or a combination of germanium-based catalysts, cobalt-based catalysts, and tin-based catalysts, and the addition concentration is 30 - 100 ppm; the intrinsic viscosity of r-PETG is 0.75 - 0.85 dL / g.

[0016] Further, in the step S3, the extrusion temperature of the extruder is 190 - 210°C, and the rotation speed of the extruder is 200 - 300 r / min.

[0017] The present invention also provides an NPG-PETG / polyethylene blend material, comprising the following components in parts by weight: 100 - 200 parts of r-PCTG, 20 - 40 parts of polyethylene material, 6 - 12 parts of compatibilizer, and 0.1 - 0.25 parts of antioxidant. The compatibilizer comprises an ethylene acrylic acid copolymer and a maleic anhydride-modified polyethylene material with a mass ratio of 2 - 3:1.

[0018] Further, the ethylene acrylic acid copolymer comprises any one or several combinations of ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic acid ionomer, and ethylene-methyl acrylic acid ionomer.

[0019] Further, the polyethylene material is LLDPE (linear low density polyethylene) or mPE (metallocene polyethylene).

[0020] The beneficial effects of the present invention are as follows:

[0021] 1. The present invention uses recycled PET material as a regenerated raw material. By classifying and recycling to select recyclable PET materials, and through depolymerization and repolymerization to prepare r-PETG material, it solves the problem of regenerative use of PET materials and also solves the problem of preparation raw materials. At the same time, using the MEG / NPG mixed solution as the depolymerization solution, PET can be efficiently depolymerized through a reasonable ratio. The MEG after depolymerization can be recycled, and NPG can be directly used as a raw material for regenerative preparation. With the added terephthalic acid, an r-PETG material with a greater intrinsic viscosity and better whiteness can be obtained. Mixing the obtained r-PETG material with a polyethylene material, such as LLDPE or mPE, a blend material with stronger toughness or impact resistance can be obtained, which can be respectively applicable to high-end packaging materials and bottle materials.

[0022] 2. In the present invention, PETG is a polar material, while polyethylene is a non-polar material. Therefore, conventional blending of the two will lead to phase separation and affect the performance of the blended material. Currently, the general solution is to use compatibilizers such as maleic anhydride grafted polymers and epoxy group grafted polymers for melt blending together. The inventors of the present invention tried the conventional method but could not solve the problem of incompatibility between PETG and polyethylene materials. Therefore, creatively, ethylene-acrylic acid copolymers and maleic anhydride-modified polyethylene materials were selected as the mixed compatibilizer during blending. The carboxylic acid groups in the ethylene-acrylic acid copolymers form hydrogen bonds or ion-dipole interactions with the polar groups of PETG, and at the same time, the ethylene end is compatible with the polyethylene material, which can greatly improve the compatibility of the two materials. At the same time, the inventors of the present invention found that when melt blending the ethylene-acrylic acid copolymer with PETG and polyethylene materials, adding a certain amount of acid anhydride-modified polyethylene materials such as maleic anhydride-modified linear low-density polyethylene or maleic anhydride-modified metallocene polyethylene can make the two materials combine more closely, improve the structural stability of the material, and endow the blended material with better impact resistance and toughness.

[0023] 3. In the present invention, the basic properties of r-PETG are defined. During the preparation, by controlling the contents of MEG and NPG in the intermediate liquid, as well as the reaction temperature and pressure, the crystallinity of the r-PETG material decreases and it has a relatively high intrinsic viscosity. During the process of preparing the blended material, by setting an appropriate blending temperature, under the action of the ethylene-acrylic acid copolymer and the acid anhydride-modified polyethylene material, the melting and connection between r-PETG and the polyethylene material can be promoted, the effect of interfacial adhesion can be improved, and phase separation can be reduced. At the same time, a lower blending temperature during the preparation can reduce the crystallinity of the material, especially the polyethylene material, thereby improving the transparency of the material and preventing chain dissociation of the polyethylene material. Specific embodiments

[0024] The following will be combined with specific embodiments. It should be noted that the technical features described in the following embodiments or the combination of technical features should not be considered in isolation, and they can be combined with each other to achieve better technical effects.

[0025] The present invention provides a production process for an NPG-PETG / polyethylene blended material, comprising the following steps:

[0026] S1. Cut r-PET into pieces and put them into a depolymerization kettle, then add the MEG / NPG mixed solution and terephthalic acid thereto, charge nitrogen for protection, and raise the temperature and stir to react to generate an intermediate liquid;

[0027] Specifically, the r-PET used in this embodiment is derived from recycled PET materials. It should be noted that the recycled PET materials do not contain PVC material components to avoid affecting the chromaticity and transparency of the final product. Before depolymerization, it needs to be washed and mechanically crushed. The collected r-PET is classified according to color. In this invention, transparent r-PET materials are selected to ensure higher transparency of the prepared product. After classification, the r-PET is preliminarily rinsed and then crushed into r-PET fragments with a size of 10 - 20 mm in a plastic crusher to facilitate the melting and decomposition of r-PET during the stirring and heating process. The r-PET fragments are added to hot water at 80 - 100 °C to be softened and then added with a cleaning solution such as an alkaline cleaning solution to deeply clean the r-PET fragments and remove the pollutants in the r-PET fragments. After cleaning, it is centrifuged and dehydrated, and dried until the moisture content of the r-PET fragments is less than 0.5%.

[0028] The dried r-PET fragments are put into a depolymerization kettle, and then a MEG / NPG mixture and terephthalic acid are pumped into the depolymerization kettle. The weight ratio of the r-PET fragments to the MEG / NPG mixture and terephthalic acid is 10 - 20:1:0.25 - 0.5. The mass ratio of EG to NPG in the MEG / NPG mixture is 2 - 6:1, and the MEG / NPG mixture is prepared by dissolving solid NPG in EG. Subsequently, nitrogen is introduced into the depolymerization kettle, and the temperature is raised to 190 °C and stirred for 60 min until the r-PET fragments are dissolved and mixed evenly. Then the temperature is raised to 200 - 250 °C and the pressure in the depolymerization kettle is maintained at 1 - 2 MPa for the depolymerization reaction. After continuing the reaction for 60 - 100 min, the depolymerization reaction is completed to generate an intermediate liquid. At this time, the content of free MEG in the intermediate liquid is 13% - 15% of the total amount of the intermediate liquid, and the content of free NPG is 8% - 10% of the total amount of the intermediate liquid.

[0029] S2. Pump the product of S1 into a polymerization reactor, decant to remove the unreacted raw materials, then add a polymerization catalyst and a stabilizer to the polymerization reactor, raise the temperature and pressure for the polymerization reaction, and after the reaction is completed, extrude and cool to obtain r-PETG;

[0030] Specifically, the reaction solution of S1 is pumped into the polymerization reactor through a pipeline. After decantation filtration to remove residual impurities in the reaction solution, a stabilizer and a polymerization catalyst are added thereto. The stabilizer is a phosphate compound stabilizer, such as diphenyl phosphate, triphenyl phosphate, etc., and the addition amount is 0.8-1% of the mass of r-PET fragments. The polymerization catalyst is one or a combination of germanium-based catalysts, cobalt-based catalysts, and tin-based catalysts, and the addition concentration is 30-100 ppm. Subsequently, the polymerization reactor is evacuated and heated for 30 min to make its pressure reach 50-100 Pa and the temperature reach 250-290 °C for reaction. When the intrinsic viscosity of the prepared r-PETG reaches 0.75-0.85 dL / g, the reaction is terminated. Pressurization is carried out to extrude r-PETG from the outlet side of the polymerization reactor, and it is cooled in a water bath and then granulated to obtain r-PETG particles.

[0031] S3. The r-PETG particles and the polyethylene material are dried separately and then added into a mixing tank. Then, an ethylene acrylic copolymer, a compatibilizer, and an antioxidant are added into the mixing tank, and after mixing, they are sent to a twin-screw extruder for extrusion, and then water-cooled and granulated and dried.

[0032] Specifically, the r-PETG particles are dried at 70 °C for 4 h, and the polyethylene material is dried at 100 °C for 1 h and then put into a mixing tank. A mixed compatibilizer is added thereto. The compatibilizer includes an ethylene acrylic copolymer and a maleic anhydride-grafted polyethylene material. Among them, there are 100-200 parts of r-PETG particles, 20-40 parts of polyethylene material, 6-12 parts of compatibilizer, and 0.1-0.25 parts of antioxidant. The mass ratio of the ethylene acrylic copolymer and the maleic anhydride-grafted linear low-density polyethylene resin in the compatibilizer is 2-3:1. The mixed raw materials are added into a twin-screw extruder and melt-blended for 20 min. The temperature of the twin-screw extruder is 190-210 °C, and the rotation speed of the extruder is 200-300 r / min.

[0033] The present invention also provides an NPG-PETG / polyethylene blend material, which comprises the following components in parts by weight: 100-200 parts of r-PCTG, 20-40 parts of polyethylene material, 6-12 parts of compatibilizer, and 0.1-0.25 parts of antioxidant. In the present invention, the polyethylene material includes LLDPE (linear low-density polyethylene) or mPE (metallocene polyethylene). The compatibilizer includes an ethylene acrylic copolymer and a maleic anhydride-modified polyethylene material with a mass ratio of 2-3:1. The maleic anhydride-modified polyethylene material includes maleic anhydride-grafted linear low-density polyethylene and maleic anhydride-grafted metallocene polyethylene. In the present invention, r-PETG is prepared according to the above method, and the intrinsic viscosity is 0.7-0.8 dL / g. The LLDPE is purchased from Zhenhai Refining & Chemical, and the mPE is purchased from ExxonMobil. The antioxidant is antioxidant 1010.

[0034] Ethylene acrylic acid copolymers include any one or several combinations of ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic acid ionomer, and ethylene-methacrylic acid ionomer. Specifically, such as DuPont Surlyn Ionomer, with grades 8920 / 8940 / 9320W / 9910, etc.

[0035] Maleic anhydride-modified linear low density polyethylene and maleic anhydride-modified metallocene polyethylene, such as products like French Orevac OE825, etc., are both acceptable.

[0036] The experimental parameters of the examples and comparative examples of the present invention are shown in Table 1 below:

[0037]

[0038] Data testing was conducted on the above-mentioned examples and comparative examples:

[0039]

[0040] From the above experimental results, it can be seen that:

[0041] The NPG-PETG / polyethylene blend material prepared in this application has enhanced toughness and impact resistance compared to pure PETG material. The reason is that after adding polyethylene material for blending, ethylene acrylic acid copolymers and maleic anhydride-modified polyethylene materials are used as mixed compatibilizers. The carboxylic acid groups in the ethylene acrylic acid copolymers form hydrogen bonds or ion-dipole interactions with the polar groups of PETG, and at the same time, the ethylene end is compatible with the polyethylene material, which can greatly improve the compatibility of the two materials. When ethylene acrylic acid copolymers are melt-blended with PETG and polyethylene materials, adding a certain amount of acid anhydride-modified polyethylene material such as maleic anhydride-modified linear low density polyethylene or maleic anhydride-modified metallocene polyethylene can further closely combine the two materials, improve the structural stability of the material, and endow the blend material with better impact resistance and toughness.

[0042] Comparative Example 1 reduced the addition amount of r-PET compared to the example. In the preparation of r-PETG, the content of NPG will increase. Excessive NPG reduces the crystallinity and degree of polymerization of the PETG material, and thus reduces the intrinsic viscosity of the prepared r-PETG material. After blending with polyethylene material LLDPE, the impact resistance of the material decreases significantly.

[0043] Comparative Example 2 reduced the terephthalic acid compared to the example, which has little effect on the extrusion performance of the prepared blend material, but the whiteness of the prepared blend material has a significant decrease.

[0044] Comparative Example 3 reduced the dosage of ethylene glycol compared with the example and increased the dosage of NPG, which led to an increase in the NPG content in the intermediate stock solution after depolymerization and an increase in the NPG content of the prepared r-PETG material. Due to the influence of the steric hindrance of the NPG side chain, the polymerization chain length of the prepared r-PETG material was shorter and its intrinsic viscosity decreased.

[0045] Comparative Example 4 reduced the contents of MEG and NPG in the intermediate stock solution (by increasing the depolymerization time) compared with the example. As a result, the r-PETG material prepared lacked organic chains during polymerization, had a lower degree of polymerization, and its intrinsic viscosity decreased.

[0046] Comparative Example 5 increased the contents of MEG and NPG in the intermediate stock solution (by reducing the depolymerization time) compared with the example. This led to an increase in the NPG content in the intermediate stock solution after depolymerization and an increase in the NPG content of the prepared r-PETG material. Due to the influence of the steric hindrance of the NPG side chain, the polymerization chain length of the prepared r-PETG material was shorter and its intrinsic viscosity decreased.

[0047] Comparative Examples 6-8 reduced the usage amounts of the compatibilizer, polyethylene, and the proportion of the blend material respectively compared with the example. From the performance tests, it can be seen that reducing the compatibilizer will reduce the compatibility of the blend material, and further cause a decline in the impact resistance and tensile properties of the material. Changing the proportion of the blend material will also reduce the performance of the material.

[0048] Although several embodiments of the present invention have been given in this article, those skilled in the art should understand that the embodiments in this article can be changed without departing from the spirit of the present invention. The above embodiments are only exemplary and should not be used as a limitation of the scope of the rights of the present invention.

Claims

1. A production process of NPG-PETG / polyethylene blend material, characterized in that It includes the following steps: S1. Cut r-PET into pieces and put them into a depolymerization kettle, then add MEG / NPG mixture and terephthalic acid thereto, charge nitrogen for protection, heat up and stir to react to generate an intermediate liquid; S2. Pump the intermediate liquid into a polymerization reactor, decant to remove unreacted raw materials, then add a polymerization catalyst and a stabilizer to the polymerization reactor, heat up and pressurize for polymerization reaction, and extrude and cool after the reaction to obtain r-PETG; S3. Dry the r-PETG material and the polyethylene material respectively and add them into a mixing tank, then add a compatibilizer and an antioxidant to the mixing tank, mix them and send them to a twin-screw extruder for extrusion, then cool by water and granulate, and dry.

2. The production process of a NPG-PETG / polyethylene blend material resin according to claim 1, characterized in that, In the step S1, the mass ratio of terephthalic acid and MEG / NPG mixture to r-PET is 0.25-0.5:1:10-20; the weight ratio of MEG to NPG in the MEG / NPG mixture is 2-6:

1.

3. The production process of an NPG-PETG / polyethylene blend material resin according to claim 2, characterized in that, In the step S1, the reaction temperature is 200-250 °C, the reaction pressure is 1-2 MPa, and the reaction time is 120-160 minutes.

4. The production process of an NPG-PETG / polyethylene blend material resin as claimed in claim 3, wherein, The content of free MEG in the intermediate liquid is 13%-15% of the total amount of the intermediate liquid, and the content of free NPG is 8%-10% of the total amount of the intermediate liquid.

5. The production process of an NPG-PETG / polyethylene blend material resin as described in claim 1, characterized in that, In the step S2, the reaction temperature of the polymerization reactor is 250-290 °C, the vacuum degree is 50-100 Pa, and the reaction time is 120-180 minutes.

6. The production process of an NPG-PETG / polyethylene blend material resin as described in claim 5, characterized in that, In the step S2, the stabilizer is a phosphate compound stabilizer, and the addition amount is 0.8%-1% of the mass of r-PET fragments; the polymerization catalyst is one or a combination of germanium catalysts, cobalt catalysts, and tin catalysts, and the addition concentration is 30-100 ppm; the intrinsic viscosity of r-PETG is 0.75-0.85 dL / g.

7. The production process of a NPG-PETG / polyethylene blend material resin as claimed in claim 1, characterized in that, In the step S3, the extrusion temperature of the extruder is 190-210 °C, and the rotation speed of the extruder is 200-300 r / min.

8. A NPG-PETG / polyethylene blend material produced by the production process according to any one of claims 1 to 7, characterized in that, It includes the following components by weight: 100-200 parts of r-PCTG, 20-40 parts of polyethylene material, 6-12 parts of compatibilizer, and 0.1-0.25 part of antioxidant. The compatibilizer includes an ethylene acrylic copolymer and a polyethylene material modified with maleic anhydride with a mass ratio of 2-3:

1.

9. The NPG-PETG / polyethylene blend material according to claim 8, characterized in that The ethylene acrylic copolymer includes any one or a combination of ethylene-acrylic acid copolymer, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer, ethylene-methyl methacrylate copolymer, ethylene-acrylic acid ionomer, and ethylene-methyl acrylic acid ionomer.

10. A NPG-PETG / polyethylene blend material according to claim 8, characterized in that, The polyethylene material is LLDPE or mPE.

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