CN115232300A - Preparation method of regenerated copolyester and heat shrinkable film thereof - Google Patents

Abstract

The invention discloses a preparation method of regenerated copolyester and a heat shrinkable film thereof, belonging to the field of waste polyester recycling. The invention utilizes the technologies of waste polyester glycolysis, methanol ester exchange and the like to prepare regenerated dimethyl terephthalate, then the regenerated dimethyl terephthalate is used for carrying out ester exchange, polycondensation and the like with other modified monomers and ethylene glycol to prepare regenerated copolyester, and finally the regenerated copolyester is directly sent to each extrusion die head through a melt conveying pipeline and a metering pump to prepare the regenerated polyester heat shrinkable film. The regenerated polyester heat shrinkable film has the characteristics of high shrinkage rate, excellent toughness, excellent transparency and the like, and realizes high-valued regeneration and utilization of waste polyester.

Description

Preparation method of regenerated copolyester and heat shrinkable film thereof

Technical Field

The invention relates to the field of waste polyester recycling, in particular to regenerated copolyester and a preparation method of a heat shrinkable film of the regenerated copolyester

Background

In polyethylene terephthalate (PET) beverage and mineral water bottles, a polyvinyl chloride (PVC) film is commonly used as a shrinkage sleeve label, so that the sleeve label needs to be removed in a PET bottle recycling process, the procedure and cost of pretreatment of regenerated bottle flakes are increased, and once the PVC film is not completely removed, the purity and quality of the regenerated PET flakes are influenced. Therefore, whether the material, technology, and design of the label can be matched with those of PET bottle body is a problem that the PET bottle can be recycled efficiently and excellently.

When used as an outer label for PET bottles, the polyester heat shrinkable film can be recycled and regenerated together with the bottle body, thereby eliminating a process of peeling a label film from the PET bottle body, which is required when a PVC heat shrinkable film label is used, and avoiding a post-treatment pressure of the waste PVC heat shrinkable film, and thus, the PVC heat shrinkable film has been banned in countries and regions such as japan, western europe, and north america. With the increasing rise of environmental protection wave at home and abroad, the polyester heat shrinkable film which is an environmental protection type packaging material will gradually replace the common PVC heat shrinkable film.

However, the conventional polyester shrink film has a low shrinkage rate of not more than 30%, which cannot meet the requirements of practical application, and therefore, the conventional polyester shrink film must be modified. Among the monomers that may be used for modification are isophthalic acid (IPA), 1, 4-Cyclohexanedimethanol (CHDM), neopentyl glycol (NPG), and the like. Wherein, because the IPA has rigid benzene ring in the molecular structure, the toughness of the polyester heat shrinkable film modified by the IPA is poor; the CHDM modified polyester film has high heat shrinkage, but the monomer price is high, so that the cost of the copolyester is high; neopentyl glycol (NPG) is a typical diol with a neopentyl structure, has good chemical reaction performance and relatively low monomer price, but the NPG modified polyester film has low heat shrinkage, and the modified polyester is the primary polyester at present. Therefore, how to integrate the cost and the performance and develop the regenerated copolyester heat shrinkable film with excellent characteristics such as high shrinkage, high toughness, high transparency and the like is a necessary way for realizing high-valued recycling of the waste polyester.

Therefore, a new solution is needed to solve this problem.

Disclosure of Invention

The present invention has been made to solve the above problems and an object of the present invention is to provide a recycled copolyester.

The technical purpose of the invention is realized by the following technical scheme:

the invention utilizes the technologies of waste polyester glycolysis, methanol ester exchange and the like to prepare regenerated dimethyl terephthalate, then the regenerated dimethyl terephthalate is used for carrying out ester exchange, polycondensation and the like with other modified monomers and ethylene glycol to prepare regenerated copolyester, and finally the regenerated copolyester is directly sent to each extrusion die head through a melt conveying pipe and a metering pump to prepare the regenerated polyester heat shrinkage film. The regenerated polyester heat shrinkable film has the characteristics of high shrinkage, excellent toughness, excellent transparency and the like, and realizes high-valued recycling of waste polyester.

The detailed preparation process of the regenerated copolyester heat shrinkable film comprises the following steps:

1. pretreatment of waste polyester: the waste polyester blocks are crushed and sent into a storage bin, the waste polyester textiles are cut off and subjected to friction granulation and then sent into the storage bin, the waste polyester bottle pieces are sorted, cleaned, subjected to impurity removal and crushed and then sent into the storage bin, and then the waste polyester bottle pieces are mixed and proportioned according to a certain proportion for the next procedure.

2. Alcoholysis of waste polyester: according to the weight percentage of waste polyester: the mass ratio of the ethylene glycol is 1. Controlling the reaction temperature to 190-210 ℃ and the reaction time to 2-4 hours to obtain an alcoholysis product with the main component of BHET, and feeding the alcoholysis product into an ester exchange kettle after filtering.

3. Preparation of crude DMT: according to BHET: methanol molar ratio of 1: 2-3, and adding a certain amount of ester exchange catalyst. Controlling the ester exchange reaction temperature to be 60-70 ℃ and the reaction time to be 3-4 hours to obtain the crude DMT of the ester exchange product.

And 4, DMT purification: and (3) filtering, centrifuging and distilling the ester exchange product, and then sending the product into an ester exchange kettle.

5. Ester exchange reaction: adding 10-20% (mole percent relative to DMT) NPG and CHDM, excess Ethylene Glycol (EG), controlling total alcohol: DMT molar ratio is 2-3, and a certain amount of ester exchange catalyst is added into the mixture. Controlling the temperature of the ester exchange reaction at 190-210 ℃ and the reaction time at 2-4 hours, and feeding the obtained ester exchange liquid into a pre-polycondensation kettle.

6. Polycondensation and preparation of chips: the esterified material enters into polycondensation-I and polycondensation-II in sequence, a certain amount of catalyst, antioxidant and stabilizer are added, the reaction temperature is controlled to be 220-260 ℃, the absolute pressure is 1-100 Kpa, and the intrinsic viscosity of the prepolymer is 0.2-0.4 dl/g. Then the mixture enters a vertical final polycondensation kettle, the reaction temperature is controlled to be 260-270 ℃, the absolute pressure is controlled to be 0.1-1 Kpa, and the reaction time is 1-2 hours, so as to prepare the regenerated copolyester; the regenerated copolyester can be formed into regenerated copolyester particles for standby by slicing processing, or sent to a film forming device through a melt pump and a melt pipeline.

7. Preparing a heat shrinkable film; and directly passing the melt conveyed from the polymerization process through a melt distribution pipe, conveying the melt to a die head through a melt metering pump to extrude a thick sheet, performing bidirectional stretching on the thick sheet, and performing sizing, trimming and rolling to obtain the regenerated copolyester heat shrinkable film. The die head temperature in the film forming process is 250-255 ℃, the longitudinal stretching temperature is 110-160 ℃, the stretching ratio is 2.5-3.5, the transverse stretching temperature is 110 ℃, and the stretching ratio is 3.0-4.5 times. The initial shrinkage temperature of the prepared shrink film is 80-100 ℃, and the shrinkage rate is 60-80%.

The comonomers are: neopentyl glycol, 1, 4-cyclohexanedimethanol;

alcoholysis catalyst: potassium carbonate, sodium hydroxide, acetate, and the like, preferably zinc acetate;

ester exchange catalyst: an acetic acid catalyst, preferably calcium acetate;

the stabilizer is: triphenyl phosphate, phosphorous acid, trimethyl phosphate, etc., preferably triphenyl phosphate;

the antioxidant is as follows: antioxidants of the hindered phenols, preferably antioxidant 1010;

the polycondensation catalyst is: antimony-based catalysts and titanium-based catalysts, preferably ethylene glycol antimony;

the invention has the following characteristics:

1) Because of the uncertainty of the waste polyester raw material, the alcoholysis product has more impurities, the BHET monomer after glycol alcoholysis is difficult to purify, and the quality of the recovered product is improved by converting the BHET monomer into DMT which is easier to purify;

2) By adding CHDM and NPG as comonomers, the toughness of the copolyester is enhanced, the shrinkage rate of the polyester film is improved, and the cost is competitive;

3) The lower prepolycondensation intrinsic viscosity is controlled, an efficient vertical liquid phase tackifying kettle is adopted as a final polycondensation reaction kettle, the residence time and the reaction temperature of a melt in the final polycondensation reaction kettle are reduced, the defects of long reaction time, high reaction temperature and melt retention of a common horizontal final polycondensation reaction kettle are overcome, the hue of a product is better, and various product quality indexes of the regenerated polyester are stable;

4) The method of directly sending the melt to the die head for extrusion film forming is adopted, so that the production process can be greatly shortened, the operation cost can be reduced, and the product quality can be improved.

Drawings

FIG. 1 is a schematic view showing the structures of circulation lines of a prepolycondensation reactor and a finisher of the present invention;

FIG. 2 is a schematic view of the structure of a booster pump apparatus according to the present invention;

FIG. 3 is a schematic view of a one-way valve according to the present invention;

FIG. 4 is a schematic structural view of a second check valve of the present invention;

FIG. 5 is an enlarged view of a second one-way valve of the present invention;

FIG. 6 is a first schematic view of the construction of the pumping cartridge and buffer cartridge of the present invention;

FIG. 7 is a second schematic structural view of a pumping cartridge and a buffer cartridge of the present invention;

reference numerals: 1. a pump body; 2. a channel; 3. a feed inlet; 4. a discharge port; 5. a one-way valve I; 6. a second one-way valve; 7. a pumping barrel; 8. a pumping chamber; 9. a pumping piston; 10. a telescopic rod; 11. a buffer cylinder; 12. a cushion piston; 13. a stopper; 14. a buffer spring; 15. a guide cylinder; 16. a first valve body; 17. a first valve hole; 18. a first conical flow limiting surface; 19. a first current limiting spring; 20. a first current limiting baffle ring; 21. a through groove; 22. a first current limiting ball head; 23. adjusting a rod; 24. an adjusting sleeve; 25. a through hole; 26. a second valve body; 27. a valve hole II; 28. an annular valve plug; 29. a second conical flow limiting surface; 30. a support spring; 31. a second current limiting spring; 32. a second current-limiting bulb; 33. adjusting the baffle ring I; 34. adjusting a baffle ring II; 35. an adjusting ring groove; 36. a second current-limiting baffle ring; 37. a guide bar; 38. a connecting rod; 39. a pressing end; 40. a rope; 41. a pre-polycondensation kettle; 42. a final polycondensation kettle; 43. a feeding pipe I; 44. a feeding pipe II; 45. a third feeding pipe; 46. a three-way joint; 47. a booster pump arrangement; 48. a valve; 49. a check valve device; 50. a pressure relief vent.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

All physical performance indexes of the regenerated copolyester chips are tested according to a test method of GBT 14190-2008 fiber grade polyester chips (PET), and the thermal shrinkage rate of the film is tested according to a test method of GB/T13519-92.

Example 1:

and (2) putting the pretreated waste polyester into an alcoholysis kettle according to the mass ratio of the waste polyester to the ethylene glycol of 1. Controlling the reaction temperature at 190 ℃ and the reaction time at 4h to obtain an alcoholysis product containing BHET, and filtering the alcoholysis product to send the alcoholysis product into an ester exchange kettle.

Controlling the ester exchange reaction temperature at 60 ℃ and the reaction time at 4h, adding BHET: the molar ratio of methanol is 1.

5% (mole percent to DMT) CHDM, 5% (mole percent to DMT) NPG and excess Ethylene Glycol (EG) were added to control total alcohol: and (3) adding 0.2 thousandth of ester exchange catalyst into the DMT at a molar ratio of 2. The obtained ester exchange liquid enters a pre-polycondensation kettle.

Controlling the temperature of polycondensation-I and polycondensation-II to be 220 ℃ and 240 ℃ respectively, controlling the absolute pressure to be 1-100 KPa, adding 0.4 per mill of stabilizer, 0.2 per mill of polycondensation catalyst and 0.5 per mill of antioxidant, and controlling the intrinsic viscosity of the prepolymer to be 0.31dL/g. And then the mixture enters a vertical final polycondensation kettle, the reaction temperature is controlled to be 260 ℃, the absolute pressure is 0.1-1 KPa, the reaction time is 2.0h, then the mixture is sent to a die head through a melt pump and a melt pipeline to extrude a thick sheet, the thick sheet is stretched in two directions, and the regenerated copolyester heat shrinkage film is prepared through shaping, trimming and rolling. Film production control conditions: the die head temperature is 250-255 ℃, the longitudinal stretching temperature is 110 ℃, the stretching ratio is 2.5 times, the transverse stretching temperature is 110 ℃, the stretching ratio is 3.0 times, the shrinkage rate of the obtained regenerated polyester heat shrinkable film is 62%, and the initial shrinkage temperature is 85 ℃ (the result is shown in table 1).

Example 2:

and (2) putting the pretreated waste polyester into an alcoholysis kettle according to the mass ratio of the waste polyester to the ethylene glycol of 1. Controlling the reaction temperature at 200 ℃ and the reaction time for 3h to obtain an alcoholysis product containing BHET, and filtering the alcoholysis product to send the alcoholysis product into an ester exchange kettle.

Controlling the ester exchange reaction temperature at 65 ℃ and the reaction time at 3.5h, adding BHET: the molar ratio of methanol is 1.

Add 7.5% (mole percent DMT) CHDM, 7.5% (mole percent DMT) NPG and excess Ethylene Glycol (EG), control total alcohol: and (3) adding 0.2 thousandth of ester exchange catalyst into the DMT at a molar ratio of 2.5, controlling the temperature of ester exchange reaction to be 200 ℃, and reacting for 3 hours. The obtained ester exchange liquid enters a pre-polycondensation kettle.

Controlling the temperature of polycondensation-I and polycondensation-II at 230 ℃ and 250 ℃ respectively, controlling the absolute pressure at 1-100 KPa, and adding 0.4 per thousand stabilizer, 0.2 per thousand polycondensation catalyst and 0.5 per thousand antioxidant, wherein the inherent viscosity of the prepolymer is 0.38dL/g. And then the mixture enters a vertical final polycondensation kettle, the reaction temperature is controlled to be 265 ℃, the absolute pressure is 0.1-1 KPa, the reaction time is 1.5h, then the mixture is conveyed to a die head through a melt pump and a melt pipeline to be extruded into a thick sheet, the thick sheet is subjected to bidirectional stretching, and then the thick sheet is subjected to shaping, trimming and rolling to obtain the regenerated copolyester heat shrinkable film. Film production control conditions: the die head temperature is 250-255 ℃, the longitudinal stretching temperature is 130 ℃, the stretching ratio is 3.0 times, the transverse stretching temperature is 110 ℃, the stretching ratio is 4.0 times, the shrinkage rate of the obtained regenerated polyester heat shrinkable film is 65%, and the initial shrinkage temperature is 95 ℃ (the result is shown in table 1).

Example 3:

and (2) putting the pretreated waste polyester into an alcoholysis kettle according to the mass ratio of the waste polyester to ethylene glycol of 1. Controlling the reaction temperature at 210 ℃ and the reaction time for 2h to obtain an alcoholysis product containing BHET, and filtering the alcoholysis product to feed the alcoholysis product into a transesterification kettle.

Controlling the ester exchange reaction temperature at 70 ℃ and the reaction time at 3h, adding BHET: the molar ratio of methanol is 1.

Add 10% (mole percent to DMT) CHDM, 10% (mole percent to DMT) NPG, and excess Ethylene Glycol (EG), control total alcohol: DMT molar ratio 3, adding 0.2 thousandth of ester exchange catalyst, controlling the temperature of ester exchange reaction at 210 ℃ and the reaction time at 2h. The obtained ester exchange liquid enters a pre-polycondensation kettle.

Controlling the temperature of polycondensation-I and polycondensation-II to 240 ℃ and 260 ℃ respectively, controlling the absolute pressure to be 1-100 KPa, adding 0.4 per mill of stabilizer, 0.2 per mill of polycondensation catalyst and 0.5 per mill of antioxidant, and controlling the intrinsic viscosity of the prepolymer to be 0.40dL/g. And then the mixture enters a vertical final polycondensation kettle, the reaction temperature is controlled at 270 ℃, the absolute pressure is 0.1-1 KPa, the reaction time is 1.0h, then the mixture is conveyed to a die head through a melt pump and a melt pipeline to extrude a thick sheet, the thick sheet is subjected to bidirectional stretching, and the regenerated copolyester heat shrinkable film is prepared through shaping, trimming and rolling. Film production control conditions: the die head temperature is 250-255 ℃, the longitudinal stretching temperature is 160 ℃, the stretching ratio is 3.5 times, the transverse stretching temperature is 110 ℃, the stretching ratio is 4.5 times, the shrinkage rate of the obtained regenerated polyester heat shrinkable film is 70%, and the initial shrinkage temperature is 98 ℃ (the result is shown in table 1).

Example 4:

as in example 2, except that: 5% (mole percent against DMT) CHDM and 10% (mole percent against DMT) NPG were added. The shrinkage rate of the obtained regenerated polyester heat shrinkable film is 64 percent, and the initial shrinkage temperature is 96 ℃ (the results are shown in Table 1).

Example 5:

as described in example 2, except that: add 10% (mole percent DMT) CHDM and 5% (mole percent DMT) NPG. The shrinkage rate of the obtained recycled polyester heat shrinkable film was 73%, and the initial shrinkage temperature was 94 ℃ (see table 1 for results).

Comparative example 1:

as in example 2, except that: 15% (mole percent with DMT) CHDM was added. The shrinkage rate of the obtained regenerated polyester heat shrinkable film is 58 percent, and the initial shrinkage temperature is 82 ℃ (the results are shown in Table 1).

Comparative example 2:

as described in example 2, except that: 15% (mole percent relative to DMT) NPG was added. The shrinkage of the obtained recycled polyester heat shrinkable film was 45%, and the initial shrinkage temperature was 87 ℃ (the results are shown in table 1).

TABLE 1 Synthesis conditions and Performance indices of recycled high-shrink polyesters and Heat-shrinkable films

Example 6

The embodiment discloses a production process of regenerated copolyester, wherein pumping is realized between a pre-polycondensation kettle 41 and a final polycondensation kettle 42 through a booster pump device 47, smoothness of a pumping process can be kept through booster pumping, materials can be still pumped smoothly under the condition that the materials have certain viscosity, and the condition that the materials are blocked possibly due to high viscosity in the pumping process is avoided.

The pre-polycondensation kettle 41 and the final polycondensation kettle 42 are connected through a booster pump device 47 for pumping materials and a material conveying pipeline, so that the high-viscosity ester materials are pumped, the materials can be conveyed smoothly, and the reaction and preparation smoothness of the regenerated copolyester are maintained.

As shown in fig. 2, the booster pump device 47 includes a cylindrical pump body 1, a channel 2 with two through ends is arranged in the pump body 1, two ends of the channel 2 are respectively provided with a feed port 3 and a discharge port 4, and the feed port 3 and the discharge port 4 are respectively connected with a conveying pipeline for materials to pass through, so as to pump the materials.

One end of the feeding port 3 of the channel 2 is provided with a one-way valve I5, one end of the discharging port 4 is provided with a one-way valve II 6, and the one-way valve I5 and the one-way valve II 6 can keep the materials to pass through in a one-way mode and conduct in a one-way mode from the feeding port 3 to the discharging port 4. Through one-way conduction structure, can ensure the pumping process in, only realize one-way transport, can apply certain pressure at the pumping process, can apply the pumping effort to the material through pressure, improve the transport smoothness nature of ester material.

The middle section of the pump body 1 is fixedly connected with a pumping cylinder 7, a pumping cavity 8 communicated with the channel 2 in the pump body 1 is arranged in the pumping cylinder 7, a pumping piston 9 is connected to the piston in the pumping cavity 8, the outward end of the pumping piston 9 is driven in a reciprocating mode through a telescopic rod 10, and the pumping piston 9 can realize compression and expansion of the pumping cavity 8 in the reciprocating moving process.

When the pumping piston 9 moves outwards, the channel 2 of the pump body 1 is lowered, the first check valve 5 is opened, the second check valve 6 is closed, the pressure in the channel 2 in the pump body 1 is lowered to form negative pressure, and materials in the channel 2 of the pump body 1 can be sucked from the first check valve 5 of the feed port 3; the materials subjected to the pre-shrinking treatment in the pre-polycondensation kettle 41 are sucked into the pump body 1; when the pumping piston 9 moves inwards, the channel 2 of the pump body 1 is pressurized, the one-way valve I5 is closed, the one-way valve II 6 is opened, the material in the channel 2 of the pump body 1 can be extruded out from the one-way valve II 6 of the discharge port 4, and the material in the pre-polycondensation kettle 41 is conveyed into the final polycondensation kettle 42; through the reciprocal flexible of telescopic link 10, to the reciprocal regulation change of pressure in the middle of the pump body 1 inner chamber, and then realize constantly carrying the ester material.

As shown in fig. 2 and 3, the check valve i 5 comprises a valve body i 16, a flow-limiting ball head i 22 and a flow-limiting spring i 19, wherein the valve body i 16 is fixedly arranged in the channel 2 and is pressed and fixed through a stepped surface; a valve hole 17 with two through ends is arranged in the valve body 16, and the two ends of the valve hole 17 are communicated and connected into the channel 2 in the valve body. And a first conical flow limiting surface 18 is formed at one end, facing the feed inlet 3, of the inner periphery of the first valve hole 17, the first conical flow limiting surface 18 is gradually reduced towards one end of the feed inlet 3, the first conical flow limiting surface 18 can be matched with the first flow limiting ball 22, and when the first flow limiting ball 22 and the first conical flow limiting surface 18 are pressed against each other, the sealing state of the first check valve 5 can be realized.

One end of the inner periphery of the valve hole I17, which faces away from the discharge hole 4, is provided with a first flow limiting blocking ring 20, the first flow limiting ball 22 is arranged in the valve hole I17, the first flow limiting spring 19 elastically abuts between the first flow limiting ball 22 and the first flow limiting blocking ring 20, the first flow limiting ball 22 and the first conical flow limiting surface 18 can be elastically pushed to abut against and seal through the elastic action of the flow limiting spring, and the first check valve 5 can be in a sealing state. When the material flows along the one-way valve 5, the flow-limiting ball head 22 can be driven to move inwards, and the flow-limiting spring 19 is compressed, so that a certain flow-guiding gap is formed between the flow-limiting ball head 22 and the conical flow-limiting surface 18, and the material can smoothly flow.

As shown in fig. 2 and 4, the second check valve 6 comprises a second valve body 26, a second flow-limiting ball head 32 and a second flow-limiting spring 31, wherein the second valve body is of a cylindrical structure and is installed in the channel 2 of the pump body 1; a valve hole II 27 with two ends penetrating is arranged in the valve body II 26, and the valve body II 26 can be inserted into the channel 2 of the pump body 1.

And an annular valve plug 28 is arranged at one end of the inner periphery of the second valve hole 27 facing the feed port 3, and a fixed second flow limiting baffle ring 36 is formed at one end of the inner periphery of the second valve hole 27 opposite to the feed port 3. The first flow-limiting ball head 22 is arranged in the valve hole, the second flow-limiting spring 31 is elastically pressed between the second flow-limiting ball head 32 and the second flow-limiting baffle ring 36, the second flow-limiting ball head 32 can be pushed to be pressed against the annular valve plug 28 through the elastic action of the second flow-limiting spring 31, and a pressing and sealing state can be formed after the second flow-limiting ball head 32 and the annular valve plug 28 are pressed against each other. When the material flows along the second check valve 6, the second flow-limiting ball head 32 is driven to move and the second flow-limiting spring 31 is compressed, so that a certain flow-guiding gap is formed between the second flow-limiting ball head 32 and the second conical flow-limiting surface 29, and the material can smoothly flow.

Furthermore, a buffer cylinder 11 can be fixedly installed at the middle section of the pump body 1, the inner cavity of the buffer cylinder 11 is communicated with the channel 2 in the pump body 1, a buffer piston 12 is installed in the buffer cylinder 11, and the buffer piston 12 can form a piston connecting structure which can be adjusted in a lifting manner in the buffer cylinder 11. The check block 13 is connected to one end, facing the pump body 1, of the inner cavity of the buffer piston 12, the check block 13 can achieve limiting and abutting effects on the buffer piston 12, the buffer spring 14 is installed at one end, far away from the pump body 1, of the buffer piston 12, and the buffer piston 12 can be elastically supported through the buffer spring 14.

The buffer piston 12 forms an elastic buffer structure in the buffer cylinder 11, and when the pressure in the inner cavity of the pump body 1 normally changes, the buffer spring 14 maintains the buffer piston 12 in a fixed position state, so that pumping can be realized on the pump body 1 through the pumping piston 9. When a blockage occurs in the pump body 1 or the internal pressure of the pump body 1 is excessively large, pressure buffering can be realized by the buffer piston 12 in the buffer cylinder 11. Pressure will promote buffer piston 12 and remove for the space that buffer cylinder 11 inserts the pump body 1 can obtain the expansion, plays the effect to the pressure release of the pump body 1, with the operating condition stability who maintains the pump body 1.

As shown in fig. 7, a pressure relief hole 50 may be further formed in the outer peripheral wall of the buffer cylinder 11, after the buffer piston 12 moves a certain distance, the buffer piston 12 will pass through the pressure relief hole 50, the pressure relief hole 50 is communicated with the channel 2 in the pump body 1 through the buffer cylinder 11, and excess pressure in the pump body 1 will be discharged from the pressure relief hole 50, thereby preventing the pump body 1 from being damaged due to too high pressure.

Further, on the basis of the above embodiment, the booster pump device 47 may be further modified. As shown in fig. 2, 3 and 4, adjusting rods 23 are mounted at positions of the channel 2 of the pump body 1 corresponding to two ends of the buffer cylinder 11, and the adjusting rods 23 can be axially adjusted along the channel 2 of the pump body 1; specifically, an adjusting sleeve 24 is fixedly installed in the channel 2 in the pump body 1, and the adjusting rod 23 passes through the adjusting sleeve 24, so that the adjusting rod 23 can be slidably guided to maintain stability during sliding. The adjusting sleeve 24 is provided with a through hole 25 penetrating through two sides, and the adjusting sleeve 24 can support and guide the adjusting rod 23 and can supply ester materials to smoothly circulate without influencing the smooth circulation of the materials.

The adjusting rods 23 penetrate through the corresponding adjusting sleeves 24, one ends of the two adjusting rods 23, which are opposite to each other, are fixedly connected with the first current-limiting ball heads 22 and the second current-limiting ball heads 32 respectively, the corresponding first current-limiting ball heads 22 and the second current-limiting ball heads 32 can be adjusted and moved by moving the adjusting rods 23, and therefore the first current-limiting ball heads 22 and the second current-limiting ball heads 32 can seal the first check valves 5 and the second check valves 6 to realize one-way conduction and sealing in a matching manner.

Specifically, the damping cylinder 11 is perpendicular to the pump body 1, a guide rod 37 is coaxially installed in the damping cylinder 11, and the guide rod 37 penetrates through the damping piston 12 and is axially adjustable along the damping cylinder 11. The guide rod 37 and the cushion piston 12 are slidably sealed, and the guide rod 37 can be maintained to move smoothly. A guide cylinder 15 is fixedly mounted on an outward end of the buffer cylinder 11, and the guide rod 37 passes through the guide cylinder 15 to slidably guide the guide rod 37, thereby maintaining smooth movement of the guide rod 37.

The guide rod 37 extends into the channel 2 in the pump body 1, and the adjusting rod 23 can be driven to axially adjust through the movement of the guide rod 37, so that the one-way valve is assisted to be opened and closed by matching with the action of the one-way valve. Two connecting rods 38 are hinged on the guide rod 37, one end of each connecting rod 38 is connected to the guide rod 37, and the other end of each connecting rod 38 is hinged to the adjusting rod 23. The guide rod 37 will bring the adjusting rod 23 to slide and adjust during the sliding process.

As shown in fig. 6, the connecting rod 38, the adjusting rods 23 and the hinge point are in the same axial state, the two adjusting rods 23 will move in opposite directions, wherein in the one-way valve 5 on the left side, the adjusting rod 23 will drive the flow limiting ball 22 to move leftward, so as to keep the flow limiting ball 22 and the tapered flow limiting surface 18 in the one-way valve 5 in a tight abutting state, and maintain the one-way valve 5 in a one-way closed state. The adjusting rod 23 on the right moves the second flow-limiting ball head 32 rightwards, so that the second flow-limiting ball head 32 and the second conical flow-limiting surface 29 in the second check valve 6 form a separated state, namely the second check valve 6 is opened, and ester materials can smoothly flow out.

One end of the guide rod 37 passes through the channel 2 in the pump body 1 and extends into the pumping chamber 8 of the pumping cylinder 7, and a cable 40 is connected between the pumping piston 9 and the pressing end 39 of the guide rod 37. During the outward movement of the pumping piston 9, the pumping piston 9 may pull the guide rod 37 in the same direction by the cable 40, i.e., pull the guide rod 37 upward as shown in the drawing.

In the upward movement process of the guide rod 37, the guide rod 37 drives the adjusting rods 23 on the two sides to retract inwards through the connecting rod 38, so that the first flow limiting ball 22 and the second flow limiting ball 32 on the two sides move towards opposite directions, the first flow limiting ball 22 on the left side is separated from the first conical flow limiting surface 18, the first check valve 5 is opened through active driving, and materials can be smoothly sucked into the valve body. At this time, the second flow-limiting ball 32 on the right side of the connecting rod 38 will further move to the left, and the pressure of the second flow-limiting ball 32 against the annular valve plug 28 in the second check valve 6 will further increase, so as to maintain the second flow-limiting ball 32 to keep the second check valve 6 in a stable sealing state.

When the pumping piston 9 moves inwards, the pumping piston 9 can abut against the abutting end 39 of the guide rod 37, the guide rod 37 can be actively driven through the pumping piston 9, the two adjusting rods 23 are driven to move, the first check valve 5 on the left side is closed, the second check valve 6 on the right side is opened, and then materials in the pump body 1 can be smoothly output from the discharge port 4.

By adopting the pumping piston 9, in the reciprocating movement process, the reciprocating change of the pressure in the inner cavity of the pump body 1 can be driven, and then the one-way valve I5 and the one-way valve II 6 can be driven to realize the corresponding opening and closing actions, so as to maintain the smooth pumping of the ester material. Meanwhile, the action of the adjusting rod 23 and the connecting rod 38 in the pump body 1 is matched, so that the flow-limiting ball head in the one-way valve can be driven to act, and the corresponding one-way valve can be actively opened and closed. The one-way valve can be actively driven to be opened and closed through active opening and closing, and further the pump device can be actively maintained in an opened state or a closed state in the pumping process to keep a stable working state.

Furthermore, a buffering structure can be arranged in the second check valve 6, the annular valve plug 28 is maintained in a stable state through the buffering structure, the annular valve plug 28 can be elastically adjusted in the length direction of the second valve hole 27, and the action interference situation can be avoided through buffering action.

As shown in fig. 5, an annular adjusting ring groove 35 is formed at one end of the inner periphery of the valve hole 27 facing the feed port 3, the annular valve plug 28 is connected in the adjusting ring groove 35 in a piston manner, and the outer periphery of the annular valve plug 28 is sealed with the peripheral wall of the adjusting ring groove 35, so that piston adjustment can be realized.

The first adjusting baffle ring 33 is fixed at one end of the adjusting ring groove 35 facing the feed inlet 3, the second adjusting baffle ring 34 is fixed at one end facing the discharge outlet 4, and the first adjusting baffle ring 33 and the second adjusting baffle ring 34 can respectively stop and limit the two end positions of the annular valve plug 28. The first adjusting stop ring 33 is elastically connected with the annular valve plug 28 through a supporting spring 30, and the annular valve plug 28 can be elastically pushed to move towards one end of the discharge hole 4 through the elastic support of the supporting spring 30, so that the annular valve plug 28 is kept in a relatively stable state.

The conical flow limiting surface II 29 is formed in the end, facing the discharge port 4, of the inner periphery of the annular valve plug 28 in a machining mode, the conical flow limiting surface II 29 is gradually enlarged towards one end of the discharge port 4, the conical flow limiting surface II 29 can be matched with the flow limiting ball head II 32, and when the flow limiting ball head II 32 and the conical flow limiting surface II 29 are pressed against each other, a pressing sealing state can be maintained, and the one-way valve II 6 is closed. When the second flow-limiting ball head 32 is separated from the second conical flow-limiting surface 29, the second check valve 6 is in an open state, and the second check valve 6 is further in an open state, so that materials can be pumped and output.

Through adopting movable structure, can cushion the support to annular valve plug 28, can supply adjusting rod 23 and spacing bulb to adjust the action smoothly to maintain to the appropriate state of pressing that supports between current-limiting bulb and the toper current-limiting surface, and ensure that initiative adjustment structure can smoothly move, and then maintain booster pump device 47 normal work.

Further, the feeding between the prepolycondensation reactor 41 and the final polycondensation reactor 42 can be performed by pumping directly by the booster pump 47, so that the feeding between the prepolycondensation reactor 41 and the final polycondensation reactor 42 can be performed smoothly. Alternatively, as shown in FIG. 1, the ester material may be smoothly transferred by connecting the pre-polycondensation reactor 41 and the final polycondensation reactor 42 through a circulation line.

As shown in FIG. 1, the circulation pipeline comprises two first feeding pipes 43, two second feeding pipes 44 and a third feeding pipe 45, wherein the two first feeding pipes 43 are respectively connected to the bottoms of the prepolycondensation reactor 41 and the final polycondensation reactor 42, and the two second feeding pipes 44 are respectively connected to the tops of the prepolycondensation reactor 41 and the final polycondensation reactor 42. The lower end of the feeding pipe III 45 is connected with the two feeding pipes I43 through a three-way joint 46, and the upper end of the feeding pipe III 45 is connected with the two feeding pipes II 44 through the three-way joint 46. And a booster pump device 47 is arranged on the third feeding pipe 45, and materials can be pumped through the booster pump device 47.

Electrically controlled valves 48 are respectively arranged on the two feeding pipes I43 and the two feeding pipes II 44 so as to control the on-off of the corresponding feeding pipes; a one-way valve device 49 is arranged on the first feeding pipe 43 to maintain the feeding of the materials from the kettle body to the third feeding pipe 45; and a one-way valve device 49 is arranged on the two feeding pipes II 44 to maintain the feeding of the materials from the feeding pipes III 45 to the kettle body. The on-off of the one-way valve device 49 on the circulating pipeline can be controlled to control the cyclic pumping from the pre-polycondensation kettle 41 to the pre-polycondensation kettle 41, so as to realize the ester material conveying action of the pre-polycondensation kettle 41 and the final polycondensation kettle 42. Through the circulating pumping, the preshrinked materials can be subjected to homogenization treatment, and the ester materials and the added materials are mixed to maintain the uniformity of the materials.

The valve 48 of the feeding pipe II 44 on the pre-polycondensation kettle 41 is cut off, the valve 48 of the feeding pipe I43 on the final polycondensation kettle 42 is cut off, and the material is pumped from the pre-polycondensation kettle 41 to the final polycondensation kettle 42 through the booster pump device 47, so that the intermediate to be treated can be fed into the final polycondensation kettle 42 for reaction.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims (10)

1. The regenerated copolyester is characterized by being prepared by the following steps:

1) Pretreating waste polyester;

2) Alcoholysis of waste polyester: according to the waste polyester: adding the ethylene glycol into an alcoholysis kettle according to the mass ratio of 1; controlling the reaction temperature to be 190-210 ℃ and the reaction time to be 2-4 hours to obtain an alcoholysis product of BHET, and feeding the alcoholysis product into an ester exchange kettle after filtering;

3) Preparation of crude DMT: according to BHET: methanol molar ratio of 1: 2-3, adding methanol and adding an ester exchange catalyst; controlling the ester exchange reaction temperature to be 60-70 ℃ and the reaction time to be 3-4 hours to obtain crude DMT of an ester exchange product;

4) Refining DMT: filtering, centrifuging and distilling the ester exchange product, and then sending the ester exchange product into an ester exchange kettle;

5) Ester exchange reaction: adding NPG, CHDM and glycol with the mol percentage of 10-20 percent of that of DMT, and controlling the total alcohol: DMT molar ratio is 2-3, and ester exchange catalyst is added; controlling the temperature of the ester exchange reaction at 190-210 ℃ and the reaction time at 2-4 hours, and feeding the obtained ester exchange liquid into a pre-polycondensation kettle;

6) Polycondensation: the esterified material enters into polycondensation-I and polycondensation-II in sequence, a polycondensation catalyst, an antioxidant and a stabilizer are added, the reaction temperature is controlled to be 220-260 ℃, the absolute pressure is 1-100 Kpa, and the intrinsic viscosity of the prepolymer is 0.2-0.4 dl/g; then the mixture enters a vertical final polycondensation kettle, the reaction temperature is controlled to be 260-270 ℃, the absolute pressure is controlled to be 0.1-1 Kpa, and the reaction time is 1-2 hours, so that the regenerated copolyester is prepared.

2. A recycled copolyester as claimed in claim 1, wherein the comonomers in the polycondensation process are: neopentyl glycol, 1, 4-cyclohexanedimethanol.

3. The recycled copolyester of claim 1, wherein the alcoholysis catalyst is: potassium carbonate or sodium hydroxide or acetate.

4. The recycled copolyester of claim 1, wherein the transesterification catalyst is: an acetic acid catalyst.

5. The recycled copolyester of claim 1, wherein the stabilizer is: triphenyl phosphate or phosphorous acid or trimethyl phosphate.

6. A recycled copolyester as claimed in claim 1, wherein said antioxidant is: antioxidants of the sterically hindered phenols.

7. A recycled copolyester as claimed in claim 1, wherein said polycondensation catalyst is: antimony-based catalyst or titanium-based catalyst or ethylene glycol antimony.

8. The recycled copolyester of claim 1, wherein in the polycondensation in step 6), the material pumping is performed between the pre-polycondensation kettle and the final polycondensation kettle by a booster pump device.

9. A process for preparing a heat-shrinkable film of recycled copolyester, which comprises preparing recycled copolyester as claimed in any one of claims 1 to 8, and feeding the recycled copolyester to a film-forming apparatus via a melt pump and a melt pipe;

and (2) preparing a heat shrinkable film, namely directly passing the melt conveyed from the polymerization process through a melt distribution pipe, conveying the melt to a die head through a melt metering pump to extrude a thick sheet, stretching the thick sheet in two directions, and then shaping, trimming and rolling to prepare the regenerated copolyester heat shrinkable film.

10. The recycled copolyester as claimed in claim 9, wherein the heat shrinkable film has a die temperature of 250-255 ℃, a longitudinal stretching temperature of 110-160 ℃, a stretching ratio of 2.5-3.5, a transverse stretching temperature of 110 ℃, a stretching ratio of 3.0-4.5, an initial shrinkage temperature of 80-100 ℃ and a shrinkage rate of 60-80% during film formation.

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