阅读说明：本技术 一种低乙醛瓶坯聚酯的生产方法及装置 (Production method and device of low-acetaldehyde bottle blank polyester ) 是由 何胜君 夏峰伟 戴志彬 常玉 周倩 于 2020-04-09 设计创作，主要内容包括：本发明涉及一种低乙醛瓶坯聚酯的生产方法及装置,属于聚酯领域。该方法以对苯二甲酸、乙二醇为主要原料,添加间苯二甲酸或2-甲基1,3丙二醇等二元醇作为第三单体,钛或锑系作为聚合催化剂,制备高粘度聚酯熔体特性粘度为(0.75-0.85)dL/g；将最终熔体泵出口的熔体分流一部分通过均质混合器与高溶度乙二醇磷稳定剂混合,将混合后熔体再输送到终缩反应釜,从底部进入与终缩釜中熔体混合。剩余熔体采用水下造粒-结晶切直接获得球形粒子,粒子在经过脱醛反应。最终聚酯粒子特性粘度为(0.75-0.87)dL/g,AA值小于0.5μg/g。本发明制备的聚酯粒子经干燥、注塑生产的瓶坯乙醛小于3μg/g。(The invention relates to a production method and a device of low-acetaldehyde bottle blank polyester, belonging to the field of polyester. The method takes terephthalic acid and ethylene glycol as main raw materials, adds dihydric alcohol such as isophthalic acid or 2-methyl 1,3 propanediol and the like as a third monomer, and takes titanium or antimony as a polymerization catalyst to prepare the high-viscosity polyester with the melt intrinsic viscosity of (0.75-0.85) dL/g; and (3) mixing a part of the melt flow of the outlet of the final melt pump with the high-solubility ethylene glycol phosphorus stabilizer through a homogenizing mixer, conveying the mixed melt to a final reduction reaction kettle, and mixing the melt from the bottom of the final reduction reaction kettle with the melt in the final reduction kettle. And directly obtaining spherical particles from the residual melt by adopting underwater granulation-crystallization cutting, wherein the particles are subjected to dealdehyding reaction. The final polyester particles had an intrinsic viscosity of (0.75-0.87) dL/g and an AA value of less than 0.5. mu.g/g. The acetaldehyde in the bottle blank produced by drying and injection molding the polyester particles prepared by the invention is less than 3 mug/g.)

1. a production method of low-acetaldehyde bottle blank polyester is characterized by comprising the following steps: the method comprises the steps of taking terephthalic acid and ethylene glycol as raw materials, adding dibasic acid or dihydric alcohol substances as modified monomers, taking titanium, antimony or germanium metal compounds as polymerization catalysts, and reacting in a final condensation kettle to prepare polyester melt; shunting melt at an outlet of a melt pump connected with a final reduction kettle, conveying one part of the melt to a homogenizing mixer to be mixed with a stabilizer, conveying the mixed melt to the final reduction kettle again and uniformly mixing with the melt in the final reduction kettle, directly conveying the other part of the melt to a granulator for granulation to obtain spherical crystal particles, conveying the spherical crystal particles to a VOC (volatile organic compound) removal reactor for reaction to obtain polyester particles, drying the polyester particles, and performing injection molding on an injection molding machine to obtain bottle blanks.

2. The method for producing a low acetaldehyde preform polyester as claimed in claim 1, wherein: the modified monomer is one or more of isophthalic acid, neopentyl glycol, 2-methyl-1, 3-propanediol and the like.

3. The method for producing a low acetaldehyde preform polyester as claimed in claim 1, wherein: the concentration of a stabilizer in the homogenizing mixer is 50-500 mu g/g, and the stabilizer is one or more of phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphonoacetate and diphenyl isooctyl phosphate.

4. The method for producing a low acetaldehyde preform polyester as claimed in claim 1, wherein: and (3) shunting the melt at the outlet of the melt pump, conveying 5-30% of the melt into a homogenizing mixer, and conveying the rest of the melt into a granulator for granulation.

5. The method for producing a low acetaldehyde preform polyester as claimed in claim 1, wherein: the crystallinity of the granulated crystal particles is 36 to 45%.

6. An apparatus for carrying out the process for producing a low acetaldehyde preform polyester of claim 1, wherein: the device includes the final kettle, homomixer and VOC desorption reactor, the discharge end of the final kettle afterbody that contracts passes through the melt pump and links to each other, and an output of melt pump passes through the homomixer and links to each other with the final kettle that contracts, and another output passes through granulator and VOC desorption reactor, VOC desorption reactor link to each other with the injection molding machine.

7. The apparatus for producing polyester bottle preforms with low acetaldehyde according to claim 4, wherein: the final reduction kettle is transversely arranged, the head part of the final reduction kettle is arranged on the left side, the tail part of the final reduction kettle is arranged on the right side, and the position where the homogenizing mixer is connected with the final reduction kettle is positioned at the left end of the discharge end of the tail part of the final reduction kettle.

8. The apparatus for producing polyester bottle preforms with low acetaldehyde according to claim 4, wherein: the ratio of the outlet of the discharge port at the tail part of the final reduction kettle to the cross-sectional area of the final reduction kettle is 1: 10-1: 15.

9. the method for producing a low acetaldehyde preform polyester as claimed in claim 1, wherein: the conditions under which the reaction is carried out in the VOC removal reactor are: the dealdehyding temperature is 140 ℃ and 180 ℃, and the retention time is 15-36 hours.

10. The process for producing a low acetaldehyde preform polyester as claimed in claim 1, wherein: the intrinsic viscosity of the polyester particles is (0.75-0.87) dL/g, and the AA value is less than 0.5 mu g/g; the intrinsic viscosity of the polyester melt was (0.75-0.85) dL/g.

Technical Field

The invention relates to the field of polyester, in particular to a production method and a device of low-acetaldehyde bottle blank polyester.

Background

Polyethylene terephthalate (PET) is a semi-crystalline thermoplastic polyester that is widely used to make fibers, films, sheets, and food trays and beverage containers. The polymer for producing the beverage container is generally produced by continuous melt polymerization and solid-phase tackifying reaction in the well-known prior art, then the polymer particles are prepared into bottle blanks through an injection molding process, and the bottle blanks are subjected to stretch blow molding to obtain the beverage containers. The base particles produced by melt polymerization generally contain more than 60. mu.g/g polymerized acetaldehyde, and the acetaldehyde (AA) content in the polymer is reduced to less than 1.0. mu.g/g by the solid phase polymerization process. The polyester particles are plasticized by a screw, acetaldehyde precursors (such as terminal vinyl) in the melt generate new AA under the action of heat and oxygen, and the new AA and the free AA in the original particles are remained in the bottle blank, and the AA in the bottle blank is increased to (5-10) mu g/g. The presence of acetaldehyde is detrimental from a taste point of view, especially for sensitive beverages such as cola, beer and water, and it is particularly desirable to keep the acetaldehyde content as low as possible.

At present, methods for reducing the acetaldehyde content in polyester bottle preforms include: 1) an acetaldehyde stabilizer is added, and the thermal stability of the polyester is improved by adding the stabilizer. U.S. Pat. No. 5.874.517 describes that by adding antioxidant 1010 and P-EPQ to reduce the acetaldehyde content during melt polymerization, PET having at least a 25% reduction in acetaldehyde content is obtained. In spring, proper modifier is added into PET to reduce acetaldehyde amount caused by thermal degradation reaction, and the acetaldehyde content in the bottle blank can be reduced by at least 30%. Ultra-low acetaldehyde PET manufactured by dao corporation is improved in hue by adding an amount of acetaldehyde scavenger stabilizer, removing the acetaldehyde formed, and adding an amount of toner. 2) Improved post-processing procedures, while the great Qingmu et al describe a method of reducing acetaldehyde emissions from a container by adding an acetaldehyde reduction procedure, i.e., reducing the amount of acetaldehyde emissions from the product by heating the product at high temperatures for short periods of time.

The prior patent is mainly realized by adding trace amounts of heat stabilizer, antioxidant and acetaldehyde scavenger in the initial reaction stage or screw to improve the heat stability of polyester, reduce thermal-oxidative degradation and absorb acetaldehyde generated in the processing process, the polyester catalyst still plays a role in catalyzing degradation reaction to a certain extent in the production and processing processes, and the acetaldehyde content in the bottle blank is still more than 5 mug/g. The acetaldehyde scavenger added to the screw can reduce the acetaldehyde content of the preform, but the acetaldehyde scavenger can degrade the polyester. Therefore, from the point of view of deactivation of polyester catalyst, a new production method is developed, which can more effectively reduce the acetaldehyde content in the bottle blank.

Disclosure of Invention

The invention provides a method and a device for producing low-acetaldehyde bottle blank polyester aiming at the existing technical problems.

The purpose of the invention can be realized by the following technical scheme:

a production method of low acetaldehyde bottle blank polyester is characterized in that terephthalic acid and ethylene glycol are used as raw materials, dibasic acid or dihydric alcohol substances are added as modified monomers, titanium, antimony or germanium metal compounds are used as polymerization catalysts, and a polyester melt is prepared by reaction in a final kettle; shunting melt at an outlet of a melt pump connected with a final reduction kettle, conveying one part of the melt to a homogenizing mixer to be mixed with a stabilizer, conveying the mixed melt to the final reduction kettle again and uniformly mixing with the melt in the final reduction kettle, directly conveying the other part of the melt to a granulator for granulation to obtain spherical crystal particles, conveying the spherical crystal particles to a VOC (volatile organic compound) removal reactor for reaction to obtain polyester particles, drying the polyester particles, and performing injection molding on an injection molding machine to obtain bottle blanks.

The technical scheme of the invention is as follows: the modified monomer is one or more of isophthalic acid, neopentyl glycol, 2-methyl-1, 3-propanediol and the like.

The technical scheme of the invention is as follows: the concentration of a stabilizer in the homogenizing mixer is 50-500 mu g/g, and the stabilizer is one or more of phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphonoacetate and diphenyl isooctyl phosphate.

The technical scheme of the invention is as follows: and (3) shunting the melt at the outlet of the melt pump, conveying 5-30% of the melt into a homogenizing mixer, and conveying the rest of the melt into a granulator for granulation.

The technical scheme of the invention is as follows: the crystallinity of the granulated crystal particles is 36 to 45%.

The device for realizing the production method of the low-acetaldehyde bottle blank polyester comprises a final reduction kettle, a homogenizing mixer and a VOC removal reactor, wherein a discharge end at the tail part of the final reduction kettle is connected through a melt pump, one output end of the melt pump is connected with the final reduction kettle through the homogenizing mixer, the other output end of the melt pump is connected with the VOC removal reactor through a granulator, and the VOC removal reactor is connected with an injection molding machine.

In the above apparatus: the final reduction kettle is transversely arranged, the head part of the final reduction kettle is arranged on the left side, the tail part of the final reduction kettle is arranged on the right side, and the position where the homogenizing mixer is connected with the final reduction kettle is positioned at the left end of the discharge end of the tail part of the final reduction kettle.

In the above apparatus: the ratio of the outlet of the discharge port at the tail part of the final reduction kettle to the cross-sectional area of the final reduction kettle is 1: 10-1: 15.

in the above apparatus: the conditions under which the reaction is carried out in the VOC removal reactor are: the dealdehyding temperature is 140 ℃ and 180 ℃, and the retention time is 15-36 hours.

In the above apparatus: the intrinsic viscosity of the polyester particles is (0.75-0.87) dL/g, and the AA value is less than 0.5 mu g/g; the intrinsic viscosity of the polyester melt was (0.75-0.85) dL/g.

The invention has the beneficial effects that:

the preparation method is simple in preparation process and easy for industrial application, and the acetaldehyde content in the prepared low-acetaldehyde bottle blank is lower than 3 mug/g.

Drawings

FIG. 1 is a schematic diagram of the production process of the present invention.

Detailed Description

The invention is further illustrated by the following examples, without limiting the scope of the invention:

referring to fig. 1, the device for producing low acetaldehyde bottle blank polyester comprises a final reduction kettle, a homogenizing mixer and a VOC removal reactor, wherein a discharge end at the tail part of the final reduction kettle is connected through a melt pump, one output end of the melt pump is connected with the final reduction kettle through the homogenizing mixer, and the other output end of the melt pump is connected with the VOC removal reactor through a granulator. Wherein: the position where the homogenizing mixer is connected with the final reduction kettle is positioned at the left end of the discharge end at the tail part of the reduction kettle, and the VOC removing reactor is connected with an injection molding machine. The ratio of the outlet of the discharge port at the tail part of the final reduction kettle to the cross-sectional area of the final reduction kettle is 1: 10 (example 1), 1: 12 (example 2), 1: 14 (example 3), 1: 15 (example 4).

Comparative example

On a ten-thousand-ton bottle polyester production line, adding a third monomer by taking terephthalic acid and ethylene glycol as main raw materials: adding a polymerization catalyst and an ether inhibitor into an isophthalic acid pulping kettle; thermal stabilizer concentrated phosphoric acid (the total weight of P content polyester is 15 mu g/g) is added from a second esterification kettle, and bottle grade basic slices with the intrinsic viscosity of 0.630dL/g are prepared by a melt polymerization method. The bottle grade basic slices are subjected to the procedures of pre-crystallization and crystallization, then the viscosity is increased to the preset viscosity at the temperature of 210 ℃, and then the bottle grade basic slices are cooled and conveyed to a storage bin. Finally, the intrinsic viscosity of the obtained polyester chip for bottles is 0.800dL/g, delta b: -1.0, terminal carboxyl group: 28mol/t, diethylene glycol: 1.2%, acetaldehyde: 0.70. mu.g/g.

Example 1

On a ten thousand ton bottle polyester production line, terephthalic acid and ethylene glycol are taken as raw materials, and a third monomer is added: isophthalic acid, a polymerization catalyst and an ether inhibitor are simultaneously added into a pulping kettle, a high-viscosity melt is prepared by adopting the existing esterification and polymerization processes, when the viscosity of the polyester melt reaches 0.75dL/g, the melt is output by a melt pump, 10 percent of the melt is shunted at the outlet of the melt pump and mixed with an ethylene glycol phosphorus stabilizer (the P content accounts for 50 mu g/g of the total weight of polyester in a final polymerization kettle) by a homogenizing mixer, the mixed melt is conveyed to a final shrinkage reaction kettle again and enters from the bottom to be mixed with the melt in the final shrinkage kettle. And (3) feeding the rest 90% of melt into an underwater pelletizer to obtain high-viscosity polyester granules, conveying the polyester granules into a VOC removal reactor through a pipeline, keeping the temperature of reactor materials at 140 ℃ for 36 hours, cooling and conveying the polyester granules to a storage bin. Finally obtaining polyester chips for bottles: intrinsic viscosity of 0.751dL/g,. DELTA.b: -2.0, terminal carboxyl group: 25mol/t, diethylene glycol: 1.2%, acetaldehyde: 0.50. mu.g/g.

Example 2

On a ten thousand ton bottle polyester production line, terephthalic acid and ethylene glycol are taken as raw materials, and a third monomer is added: neopentyl glycol, adding a polymerization catalyst and an ether inhibitor into a pulping kettle simultaneously, preparing a high-viscosity melt by adopting the existing esterification and polymerization processes, outputting the melt by a melt pump when the viscosity of the polyester melt reaches 0.85dL/g, shunting 30% of the melt at the outlet of the melt pump, mixing the melt with a phosphoric acid stabilizer (the P content accounts for 500 mu g/g of the total weight of the polyester in a final polycondensation kettle) by a homogenizing mixer, conveying the mixed melt to the final polycondensation reaction kettle, and mixing the mixed melt with the melt in the final polycondensation kettle from the bottom. And (3) feeding the rest 70 percent of melt into an underwater pelletizer to obtain high-viscosity polyester granules, conveying the polyester granules into a dealdehyding reactor through a pipeline, keeping the polyester granules at the temperature of 180 ℃ for 15 hours, cooling and conveying the polyester granules to a storage bin. Finally obtaining polyester chips for bottles: intrinsic viscosity 0.87dL/g,. DELTA.b: -1.8, terminal carboxyl group: 25mol/t, diethylene glycol: 1.1%, acetaldehyde: 0.51. mu.g/g.

Example 3

On a ten thousand ton bottle polyester production line, terephthalic acid and ethylene glycol are taken as raw materials, and a third monomer is added: 2-methyl 1, 3-propanediol, and a polymerization catalyst and an ether inhibitor are added into a pulping kettle at the same time. The existing esterification and polymerization processes are adopted to prepare high-viscosity melt, when the viscosity of the polyester melt reaches 0.80dL/g, the melt is output through a melt pump, 5 percent of melt is shunted at a melt pump outlet and mixed with phosphoric acid stabilizer (the P content accounts for 300 mu g/g of the total weight of the polyester in the final polymerization kettle) through a homogenizing mixer, the mixed melt is conveyed to a final shrinkage reaction kettle again, and the mixed melt enters from the bottom and is mixed with the melt in the final shrinkage kettle. And (3) feeding the rest 95 percent of melt into an underwater pelletizer to obtain high-viscosity polyester granules, conveying the polyester granules into a VOC removal reactor through a pipeline, keeping the temperature of the materials in the reactor at 170 ℃ for 24 hours, cooling and conveying the polyester granules to a storage bin. Finally obtaining polyester chips for bottles: intrinsic viscosity 0.801dL/g,. DELTA.b: -2.2, terminal carboxyl group: 26mol/t, diethylene glycol: 1.1%, acetaldehyde: 0.48. mu.g/g.

Example 4

On a ten thousand ton bottle polyester production line, terephthalic acid and ethylene glycol are taken as raw materials, and a third monomer is added: cyclohexane dimethanol, and a polymerization catalyst and an ether inhibitor are added into the pulping kettle at the same time. The method comprises the steps of preparing a high-viscosity melt by adopting the existing esterification and polymerization processes, outputting the melt by a melt pump when the viscosity of the polyester melt reaches 0.82dL/g, shunting 10% of the melt at the outlet of the melt pump, mixing the melt with a phosphoric acid stabilizer (the P content accounts for 400 mug/g of the total weight of the polyester in a final polymerization kettle) by a homogenizing mixer, conveying the mixed melt to a final shrinkage reaction kettle, and mixing the mixed melt with the melt in the final shrinkage kettle from the bottom. And (3) feeding the rest 90% of melt into an underwater pelletizer to obtain high-viscosity polyester granules, conveying the polyester granules into a VOC removal reactor through a pipeline, keeping the polyester granules at the temperature of 160 ℃ for 30 hours, cooling and conveying the polyester granules to a storage bin. Finally obtaining polyester chips for bottles: intrinsic viscosity 0.82dL/g,. DELTA.b: -2.0, terminal carboxyl group: 25mol/t, diethylene glycol: 1.0%, acetaldehyde: 0.4. mu.g/g.

After being dried, the bottle grade polyester prepared by the method is prepared into 32g of polyester bottle blanks on an injection molding machine, and the acetaldehyde content in the bottle blanks is tested according to the acetaldehyde test standard (GB17931-2003) in the bottle grade polyester. The test results are given in the following table: