A modified foamed PET and its preparation method

Abstract

The present invention relates to the technical field of polymer materials, and discloses a modified foamed PET and a preparation method thereof. The raw materials, by mass, include: 100 parts of terephthalic acid; 20 to 60 parts of ethylene glycol; 10 to 60 parts of modified diol; 0.01 to 0.10 part of catalyst; 0.01 to 0.10 part of viscosity increasing agent. In the raw materials of the modified foamed PET, stearate and modified diol are added. The alkyl chain of the stearate can entangle with the polyester chain of PET to generate entanglement points, which can significantly increase the melt viscosity during PET foaming. The modified diol can destroy the regularity of the PET molecular chain, promote the entanglement points generated by the stearate and PET, and further improve the viscosity increasing performance of the stearate. In addition, the modified diol can also reduce the foaming temperature and increase the foaming ratio. In addition, the foaming processing temperature of the modified PET provided in this application is low and the energy consumption is small.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a modified foamed PET and a preparation method thereof. Background Art

[0002] Polyethylene terephthalate (PET) is a high molecular polyester made from terephthalic acid and ethylene glycol through esterification reaction and polycondensation reaction under the condition of a catalyst. After foaming treatment, PET can be made into foamed PET material, which has good mechanical properties, dimensional stability, electrical insulation, weather resistance, corrosion resistance, and light weight and high strength.

[0003] At present, the foaming methods of foamed PET materials include physical foaming method and chemical foaming method. The chemical foaming method uses a chemical foaming agent for foaming. The chemical foaming agent decomposes into gas under certain conditions to make the PET material foam and form. However, the chemical foaming method has high cost, complex process, and chemical reagents are easy to remain, which is toxic, harmful and not environmentally friendly. Therefore, the prior art uses the physical foaming method with low cost, simple process, non-toxic and harmless to replace the chemical foaming method. The foaming agent of the physical foaming method often selects non-toxic and harmless gases such as inert gas and carbon dioxide, and the foaming method is more green and safe.

[0004] PET has the characteristics of low melt strength and low melt viscosity. Therefore, PET is prone to degradation when processed at a temperature higher than the melting point, and PET cannot provide good conditions for the growth and shaping of bubbles during foaming, and problems such as bubble rupture, collapse and merging are likely to occur. In order to solve the above problems, in the prior art, PET is modified by a chain extender. The melt viscosity of the modified PET increases, and the PET with high melt viscosity can provide better support for the formation of bubbles during foaming, reducing problems such as bubble collapse and bubble merging. For example, a method for enhancing the melt toughness and viscosity of PET disclosed in Publication No. CN111253611A prepares an organosilicon epoxy chain extender through polysiloxane and bisphenol A type epoxy resin, and improves the toughness and strength of PET by adding a chain extender. However, bisphenol A is contained in the chain extender in this method, and bisphenol A has high biological toxicity, resulting in problems of environmental unfriendliness and low safety performance. Another example is a method for preparing an aromatic polyester microcellular foaming material and a preparation method thereof disclosed in Publication No. CN104817830A. In this method, pyromellitic dianhydride (PMDA), tetrafunctional epoxy resin and bisoxazoline are used as chain extenders to significantly increase the melt strength of PET, but this method also has problems of high energy consumption for foaming and limited foaming ratio. Summary of the Invention

[0005] In order to overcome the problems of low melt strength, high foaming temperature, narrow processing window and uneven cell distribution in the PET foaming process in the above-mentioned prior art, the present application provides a modified foamed PET and its preparation method. A tackifier and a modified diol are added to the raw materials of the modified foamed PET, wherein the tackifier is a stearate. The present application finds that the alkyl chain of the stearate can entangle with the polyester chain to form cross-linking points, which can improve the melt viscosity of the foamed PET and the melt strength of the foamed PET. At the same time, the modified diol is beneficial to the generation of entanglement cross-linking points between the stearate and the polyester chain, further enhancing the tackifying performance of the stearate.

[0006] The specific technical solution of the present invention is as follows:

[0007] A modified foamed PET, the raw materials by mass parts include:

[0008] 100 parts of terephthalic acid;

[0009] 20 - 60 parts of ethylene glycol;

[0010] 10 - 60 parts of modified diol;

[0011] 0.01 - 0.10 parts of catalyst;

[0012] 0.01 - 0.10 parts of tackifier;

[0013] The tackifier is a stearate.

[0014] Preferably, the modified diol is selected from one or more of 1,2 - propanediol, 1,3 - butanediol, 1,4 - butanediol, neopentyl glycol and 1,4 - cyclohexanedimethanol.

[0015] Preferably, the catalyst is selected from one or more of antimony glycolate, antimony trioxide, antimony acetate, tetraisopropyl titanate, tetrabutyl titanate, potassium oxalate titanate and potassium fluotitanate.

[0016] Preferably, the stearate is selected from one or more of potassium stearate, sodium stearate, magnesium stearate, calcium stearate, zinc stearate and aluminum stearate.

[0017] The present application provides a modified foamed PET. The raw materials of the modified foamed PET include a modified diol and a viscosity-increasing agent stearate, which significantly improve the viscoelasticity and melt strength of the foamed PET. The polyester with a high melt viscosity can provide better support for the formation of foam cells during foaming, reducing problems such as foam cell collapse and cell coalescence. Adding stearate during the synthesis of PET in the present application can improve the viscoelasticity of PET. The alkyl chains on the molecular chain of stearate can physically entangle with the polyester chain to form entanglement points, which can significantly improve the viscoelasticity of PET. In addition, a modified diol is added in the present application. The modified diol can improve the flexibility of the PET polyester molecular chain and promote the formation of more entanglement points between the stearate and the PET molecular chain, thereby further enhancing the viscosity-increasing performance of the stearate. In addition, stearate also has lubricity during the polyester foaming process, which can reduce the friction between polyester molecular chains and increase the uniformity of the foamed cells. When the modified diol improves the flexibility of the polyester molecular chain, it can further enhance the uniformity of the foam cells of the PET polyester. The regularity of the PET molecular chain is destroyed, and the crystallization performance is greatly reduced. This makes the blowing agent dissolve more uniformly in the polyester, and the foam cell distribution during foaming is also more uniform. Compared with conventional PET, the foaming temperature is greatly reduced, and the foaming ratio is increased.

[0018] A preparation method of a modified foamed PET includes the following preparation steps:

[0019] Step 1: Mix terephthalic acid, ethylene glycol, a modified diol, and a catalyst and react to form an esterified product;

[0020] Step 2: React a viscosity-increasing agent with the esterified product obtained in Step 1 to form polyester chips;

[0021] Step 3: Mix the polyester chips with a blowing agent and foam to form a modified foamed PET.

[0022] Preferably, the mixing conditions in Step 1 are: temperature is 100 - 150 °C, and time is 5 - 30 min;

[0023] The reaction conditions are: temperature is 220 - 260 °C, and pressure is 0 - 0.4 MPa.

[0024] Preferably, the reaction in Step 2 includes a pre-polycondensation reaction and a final polycondensation reaction;

[0025] The pre-polycondensation reaction conditions include: temperature is 260 - 280 °C, pressure is 0 - 1000 Pa, and time is 30 - 70 min;

[0026] The final polycondensation reaction conditions include: temperature is 270 - 280 °C, pressure is 0 - 300 Pa, and time is 30 - 120 min.

[0027] Preferably, the intrinsic viscosity of the polyester chips described in step 2 is greater than 0.8 dL / g. The viscosity of conventional polyester fiber chips is 0.64 - 0.68 dL / g. The viscosity of the polyester chips prepared in this application is much higher than that of conventional polyester fiber chips.

[0028] Preferably, the foaming conditions described in step 3 include: temperature 70 - 150 °C, pressure 10 - 30 MPa, holding pressure time 5 - 120 min, pressure relief time 0 - 10 s, and cooling time 0 - 30 min.

[0029] Preferably, the foaming agent described in step 3 is carbon dioxide and / or nitrogen;

[0030] Preferably, the density of the foamed beads of the modified foamed PET is 35 - 400 kg / m 3 。

[0031] Compared with the prior art, this application has the following technical effects:

[0032] (1) In the modified PET raw material provided in this application, stearate is added as a viscosity increasing agent. The alkyl chain of stearate can entangle with the polyester chain of PET to generate entanglement points, which can significantly increase the melt viscosity during PET foaming;

[0033] (2) In the modified PET raw material provided in this application, modified diol is also added. The modified diol can destroy the regularity of the PET molecular chain, promote the entanglement points generated by stearate and PET, further improve the viscosity increasing performance of stearate. In addition, the modified diol can also reduce the foaming temperature and increase the foaming ratio;

[0034] (3) The foaming processing temperature of the modified PET provided in this application is low and the energy consumption is small. Detailed Embodiments

[0035] The present invention will be further described below in conjunction with embodiments.

[0036] General Embodiment

[0037] A polyester foaming material includes the following raw materials by weight:

[0038] Terephthalic acid 100 parts;

[0039] Ethylene glycol 20 - 60 parts;

[0040] Modified diol 10 - 60 parts, and the modified diol is selected from one or more of 1,2 - propanediol, 1,3 - propanediol, 1,4 - butanediol, neopentyl glycol, 1,4 - cyclohexanedimethanol;

[0041] The catalyst (calculated based on the central atom) is 0.01 to 0.10 parts, and the catalyst is selected from one or more of antimony glycolate, antimony trioxide, antimony acetate, tetra-isopropyl titanate, tetra-butyl titanate, potassium oxalate titanate, and potassium fluotitanate;

[0042] The stearate is 0.01 to 0.10 parts, and the stearate is selected from one or more of potassium stearate, sodium stearate, magnesium stearate, calcium stearate, zinc stearate, and aluminum stearate;

[0043] The foaming agent is one or both of carbon dioxide and nitrogen;

[0044] A preparation method of modified foamed PET includes the following preparation steps:

[0045] Step 1: Mix terephthalic acid, ethylene glycol, modified glycol, and a catalyst and react to form an esterified product;

[0046] The mixing conditions are: temperature is 100 to 150 °C, and time is 5 to 30 min;

[0047] The reaction conditions are: temperature is 220 to 260 °C, and pressure is 0 to 0.4 MPa;

[0048] Step 2: React the viscosity-increasing agent with the esterified product obtained in Step 1 to form polyester chips;

[0049] The reaction includes a pre-polycondensation reaction and a final polycondensation reaction;

[0050] The pre-polycondensation reaction conditions include: temperature 260 to 280 °C, pressure 0 to 1000 Pa, and time 30 to 70 min;

[0051] The final polycondensation reaction conditions include: temperature 270 to 280 °C, pressure 0 to 300 Pa, and time 30 to 120 min;

[0052] The intrinsic viscosity of the polyester chips is greater than 0.8 dL / g;

[0053] Step 3: Mix the polyester chips with the foaming agent and foam to form modified foamed PET;

[0054] The foaming agent is carbon dioxide and / or nitrogen;

[0055] The foaming conditions include: temperature 70 to 150 °C, pressure 10 to 30 MPa, holding pressure time 5 to 120 min, pressure relief time 0 to 10 s, and cooling time 0 to 30 min;

[0056] The foamed bead density of the modified foamed PET is 35 to 400 kg / m 3 .

[0057] Example 1:

[0058] A modified foamed PET, the raw materials by mass fraction include:

[0059] 100 parts of terephthalic acid;

[0060] 60 parts of ethylene glycol;

[0061] 30 parts of modified diol, and the modified diol is 1,3 - butanediol;

[0062] 0.05 part of catalyst, and the catalyst is antimony glycolate;

[0063] 0.05 part of viscosity - increasing agent, and the viscosity - increasing agent is sodium stearate;

[0064] A preparation method of the modified foamed PET, comprising the following preparation steps:

[0065] Step 1: Add terephthalic acid, ethylene glycol, modified diol and catalyst into a 2.5L reaction kettle according to the above raw material ratio. After stirring at 100°C for 15 min, introduce N2, and carry out an esterification reaction at 220 - 243°C, 0.30 - 0.40 Mpa and a stirring paddle frequency of 50 Hz to produce an esterified product;

[0066] Step 2: After the water removal is completed, add the viscosity - increasing agent to the esterified product obtained in Step 1, stir for 10 min, evacuate to a pressure of 1000 Pa for 30 min, and raise the temperature to 280°C for pre - polycondensation reaction; carry out a final polycondensation reaction at a temperature of 280°C and a pressure of 300 Pa; the initial stirring paddle power is 64.3 W. When the stirring paddle power rises to 80.0 W, reduce the rotation speed to 25 Hz. When the stirring power rises to 80.0 W again, stop the reaction, discharge and pelletize to obtain polyester chips;

[0067] Step 3: The obtained chips are dried and then placed in a foaming kettle, filled with foaming agent CO2 and pre - heated to a temperature of 115°C, pressurized to 18 MPa, kept at a constant temperature and pressure for 20 min, then quickly depressurized to atmospheric pressure through a manual valve for 3 s, cooled for 10 min, and the foaming kettle is opened to take out the sample to obtain the modified foamed PET.

[0068] Example 2:

[0069] A modified foamed PET, the raw materials by mass fraction include:

[0070] 100 parts of terephthalic acid;

[0071] 60 parts of ethylene glycol;

[0072] 30 parts of modified diol, and the modified diol is 1,3 - butanediol;

[0073] 0.05 part of catalyst, and the catalyst is antimony glycolate;

[0074] 0.01 part of tackifier, and the tackifier is sodium stearate;

[0075] A preparation method of modified foamed PET includes the following preparation steps:

[0076] Step 1: Add terephthalic acid, ethylene glycol, modified diol and catalyst into a 2.5 L reaction kettle according to the above raw material ratio. After stirring at 100 °C for 15 min, introduce N2. Carry out an esterification reaction at 220 - 243 °C, 0.30 - 0.40 Mpa and a stirring paddle frequency of 50 Hz to prepare an esterified product;

[0077] Step 2: After the water outlet is completed, add the tackifier to the esterified product obtained in Step 1, stir for 10 min, evacuate to a pressure of 1000 Pa for 30 min, and raise the temperature to 280 °C for pre-polycondensation reaction; Carry out a final polycondensation reaction at a temperature of 280 °C and a pressure of 300 Pa; The initial stirring paddle power is 64.3 W. When the stirring paddle power rises to 80.0 W, reduce the rotation speed to 25 Hz. When the stirring power rises to 80.0 W again, stop the reaction, discharge the material and pelletize to obtain polyester chips;

[0078] Step 3: The obtained chips are dried and then placed in a foaming kettle. Charge the foaming agent CO2 and preheat to a temperature of 110 °C, raise the pressure to 17 MPa, keep the temperature and pressure constant for 20 min, and then quickly release the pressure to atmospheric pressure through a manual valve for 3 s, cool for 10 min, open the foaming kettle and take out the sample to obtain modified foamed PET.

[0079] Example 3:

[0080] A modified foamed PET, the raw materials include by mass:

[0081] 100 parts of terephthalic acid;

[0082] 60 parts of ethylene glycol;

[0083] 30 parts of modified diol, and the modified diol is 1,3 - butanediol;

[0084] 0.05 part of catalyst, and the catalyst is antimony glycolate;

[0085] 0.1 part of tackifier, and the tackifier is sodium stearate;

[0086] A preparation method of modified foamed PET includes the following preparation steps:

[0087] Step 1: Add terephthalic acid, ethylene glycol, modified diol and catalyst into a 2.5 L reactor according to the above raw material ratio. After stirring at 100 °C for 15 min, introduce N2, and carry out an esterification reaction at 220 - 243 °C, 0.30 - 0.40 Mpa and a stirring paddle frequency of 50 Hz to produce an esterified product;

[0088] Step 2: After the water discharge is completed, add a viscosity increasing agent to the esterified product obtained in Step 1, stir for 10 min, evacuate to a pressure of 1000 Pa for 30 min, and raise the temperature to 280 °C for a pre-polycondensation reaction; carry out a final polycondensation reaction at a temperature of 280 °C and a pressure of 300 Pa; the initial stirring paddle power is 64.3 W. When the stirring paddle power rises to 80.0 W, reduce the rotation speed to 25 Hz. When the stirring power rises to 80.0 W again, stop the reaction, discharge the material and pelletize it to obtain polyester chips;

[0089] Step 3: The obtained chips are dried and then placed in a foaming kettle, filled with a foaming agent CO2 and preheated to a temperature of 95 °C, the pressure is raised to 15 MPa, kept at a constant temperature and pressure for 20 min, and then quickly depressurized to atmospheric pressure through a manual valve for 3 s, cooled for 10 min, open the foaming kettle and take out the sample to prepare modified foamed PET.

[0090] Example 4:

[0091] Compared with Example 1, in Example 4, the modified diol is 1,3 - butanediol, and the viscosity increasing agent is aluminum stearate, and the other conditions are the same as those in Example 1.

[0092] Example 5:

[0093] Compared with Example 1, in Example 5, the modified diol is 1,2 - propanediol, and the viscosity increasing agent is potassium stearate, and the other conditions are the same as those in Example 1.

[0094] Example 6:

[0095] Compared with Example 1, in Example 5, the modified diol is 1,4 - butanediol, and the viscosity increasing agent is magnesium stearate, and the other conditions are the same as those in Example 1.

[0096] Example 7:

[0097] Compared with Example 1, in Example 5, the modified diol is neopentyl glycol, and the viscosity increasing agent is calcium stearate, and the other conditions are the same as those in Example 1.

[0098] Example 8:

[0099] Compared with Example 1, in Example 5, the modified diol is 1,4 - cyclohexanedimethanol, and the viscosity increasing agent is zinc stearate, and the other conditions are the same as those in Example 1.

[0100] Comparative Example 1: (Ordinary PET)

[0101] Compared with Example 1, in Comparative Example 1, no modified diol and stearate were added to the raw materials of PET, and the other conditions were the same as those in Example 1.

[0102] Comparative Example 2: (No stearate added)

[0103] Compared with Example 1, in Comparative Example 2, no stearate was added to the raw materials of PET, and the other conditions were the same as those in Example 1.

[0104] Comparative Example 3: (No modified diol added)

[0105] Compared with Example 2, in Comparative Example 3, no modified diol was added to the raw materials of PET, and the other conditions were the same as those in Example 1.

[0106] Detection Example

[0107] The foaming properties of the modified foamed PET prepared in Examples 1-8 and Comparative Examples 1-3 were detected. The detection of the intrinsic viscosity referred to "GB / T 14189 Fiber-grade Polyester Chips", and the detection results are shown in Table 1;

[0108] Table 1 Foaming Properties of Modified Foamed PET

[0109] Modified diol Tackifier Intrinsic viscosity (dL / g) <![CDATA[Foam density (kg / m 3 )]]> Example 1 1,3-Butanediol 0.05 parts of sodium stearate 0.865 35 Example 2 1,3-Butanediol 0.01 parts of sodium stearate 0.808 62 Example 3 1,3-Butanediol 0.10 parts of sodium stearate 0.851 400 Example 4 1,3-Butanediol 0.05 parts of aluminum stearate 0.855 56 Example 5 1,2-Propylene glycol 0.05 parts of potassium stearate 0.856 44 Example 6 1,4-Butanediol 0.05 parts of magnesium stearate 0.852 49 Example 7 Neopentyl glycol 0.05 parts of calcium stearate 0.860 56 Example 8 1,4-Cyclohexanedimethanol 0.05 parts of zinc stearate 0.861 43 Comparative Example 1 / / 0.645 630 Comparative Example 2 30 parts of 1,3-butanediol / 0.652 583 Comparative Example 3 / 0.05 parts of sodium stearate 0.708 476

[0110] As shown in Table 1, compared with Comparative Example 1 (ordinary PET), the intrinsic viscosity of the modified foamed PET in Example 1 increased significantly. Comparing the examples with Comparative Examples 1-3, the results of Comparative Example 1 and Comparative Example 2 showed that adding modified diol could not improve the foaming intrinsic viscosity of PET and the reduction of foam density was not significant. The results of Comparative Example 1 and Comparative Example 3 showed that only adding stearate could significantly increase the intrinsic viscosity of PET, while adding both modified diol and stearate could further increase the intrinsic viscosity of PET. From the above results, it can be concluded that adding stearate alone to PET can significantly increase the intrinsic viscosity of PET, adding both modified diol and stearate to PET can further increase the intrinsic viscosity of PET, and modified diol can promote the viscosity-increasing performance of stearate in PET;

[0111] From the results of Examples 1-3, it can be seen that the dosage ratio of the viscosity-increasing agent does not have a linear increasing relationship with the viscosity-increasing performance of PET. The viscosity-increasing agent needs to be at a specific ratio to exhibit a significant increment characteristic. At the same time, the conditions of the foaming process in Examples 1-3 and the foam density of the foamed PET are relatively large. By controlling different foaming process conditions, foamed PET materials with different foam densities can be obtained. The foaming density of this application can control the foam density within 35-400 kg / m 3 ;

[0112] From the results of Examples 1 to 8, it can be obtained that various stearates and modified diols can significantly improve the intrinsic viscosity of PET. After modifying PET with a specific proportion of stearate, modified foamed PET with high intrinsic viscosity and low foam viscosity can be obtained.

[0113] In summary, stearate can significantly improve the intrinsic viscosity of PET, and modified diol and stearate can further improve the viscosity-increasing performance of stearate. The modified PET provided by this application has a high melt viscosity, uniform foaming, good cell morphology, low energy consumption and low processing temperature.

[0114] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes and equivalent transformations made to the above embodiments according to the technical essence of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A modified foamed PET, characterized in that, The raw materials by mass parts include: 100 parts of terephthalic acid; 20 - 60 parts of ethylene glycol; 0.01 - 0.10 part of catalyst; 0.01 - 0.10 part of viscosity increasing agent; The viscosity increasing agent is stearate; 10 - 60 parts of modified diol; the modified diol is selected from one or more of 1,2 - propanediol, 1,3 - butanediol, 1,4 - butanediol, neopentyl glycol and 1,4 - cyclohexanedimethanol; The modified foamed PET is made by mixing and foaming polyester chips and a foaming agent. The polyester chips are made by reacting a viscosity increasing agent with an esterified product. The esterified product is made by reacting terephthalic acid, ethylene glycol, modified diol and a catalyst.

2. The modified foamed PET according to claim 1, characterized in that, The catalyst is one or more of antimony glycolate, antimony trioxide, antimony acetate, tetra - isopropyl titanate, tetra - butyl titanate, potassium oxalate titanate and potassium fluotitanate.

3. The modified foamed PET according to claim 1, wherein The stearate is one or more of potassium stearate, sodium stearate, magnesium stearate, calcium stearate, zinc stearate and aluminum stearate.

4. A method for preparing the modified foamed PET according to any one of claims 1 to 3, characterized in that, It includes the following preparation steps: Step 1: Mix terephthalic acid, ethylene glycol, modified diol and a catalyst and react to make an esterified product; Step 2: React the viscosity increasing agent with the esterified product obtained in Step 1 to make polyester chips; Step 3: Mix the polyester chips and a foaming agent and foam to make the modified foamed PET.

5. The preparation method according to claim 4, characterized in that, The mixing conditions in Step 1 are: temperature is 100 - 150 °C, time is 5 - 30 min; the reaction conditions are: temperature is 220 - 260 °C, pressure is 0 - 0.4 MPa.

6. The preparation method according to claim 4, characterized in that, The reaction in Step 2 includes a pre - polycondensation reaction and a final polycondensation reaction; the pre - polycondensation reaction conditions include: temperature 260 - 280 °C, pressure is 0 - 1000 Pa, time is 30 - 70 min; the final polycondensation reaction conditions include: temperature 270 - 280 °C, pressure is 0 - 300 Pa, time is 30 - 120 min.

7. The preparation method according to claim 4, characterized in that, The intrinsic viscosity of the polyester chips in Step 2 is greater than 0.8 dL / g.

8. The preparation method according to claim 4, characterized in that, The foaming conditions in Step 3 include: temperature 70 - 150 °C, pressure 10 - 30 MPa, pressure holding time 5 - 120 min, pressure relief time 0 - 10 s, cooling time 0 - 30 min.

9. The preparation method according to claim 4, characterized in that, In Step 3, the blowing agent is carbon dioxide and / or nitrogen; the density of the foamed beads of the modified foamed PET is 35 - 400 kg / m 3 .