CN119752122A

CN119752122A - A kind of PET resin for melt-blowing and preparation method thereof

Info

Publication number: CN119752122A
Application number: CN202410817877.3A
Authority: CN
Inventors: 孙宾; 杨新华; 陈龙; 李院院; 靳向煜; 刘园园; 郑佳; 王松林
Original assignee: Donghua University; Zhejiang Hengyi Petrochemical Co Ltd
Current assignee: Donghua University; Zhejiang Hengyi Petrochemical Co Ltd
Priority date: 2024-06-24
Filing date: 2024-06-24
Publication date: 2025-04-04

Abstract

The invention relates to the technical field of melt blowing, and provides a special PET resin for melt blowing and a preparation method thereof, aiming at the problems of high processing temperature and poor melt fluidity during melt blowing of PET resin, wherein the special PET resin for melt blowing comprises HBPET/PET composite resin master batch and pure PET resin slices, HBPET is hyperbranched high molecular polyester with a carboxyl end group structure, the quantity of carboxyl end groups accounts for 25-100% of the total quantity of end groups, the branching degree is 30-100%, and the mass ratio of HBPET in the raw materials is 0.1-3%. The invention can improve the rheological property of PET resin, improve the melt-blown processing property of PET, and ensure that the PET melt maintains higher melt strength, thus obtaining finer and stronger fiber products. The invention also provides a preparation method of the special PET resin for melt blowing, which comprises the steps of preparing master batches by melt blending HBPET and PET, mixing the master batches with pure PET resin slices, melting, mixing and granulating.

Description

PET resin special for melt blowing and preparation method thereof

Technical Field

The invention relates to the technical field of melt blowing, in particular to a PET resin special for melt blowing and a preparation method thereof.

Background

The meltblown fabric uses polypropylene (PP) as a main raw material, and polyethylene terephthalate (PET) is the second largest raw material next to PP. Compared with PP, PET has higher mechanical strength and chemical stability, is an excellent choice of melt-blowing processing raw materials, and has lower cost. However, the linear molecular structure of PET results in poor processability and a low crystallization rate. Meanwhile, the high melting point ensures that the processing temperature of PET is high, and the high processing temperature ensures that the PET is thermally degraded, thereby seriously affecting the performance of PET products.

In melt blowing, melt flowability is critical to melt blown material processing, which requires the use of hot air streams to stretch the polymer melt extruded from the spinneret, and therefore requires the raw materials to have low melt viscosity, good flowability, and thermal stability at the melt temperature. However, the PET resin for filament melt spinning is directly used for melt-blowing processing, which has the disadvantages of larger viscosity, poorer fluidity, higher temperature required in melt-blowing processing, larger energy consumption and unsatisfactory performance of products.

The rheological property of the PET resin can be regulated and controlled by adding the rheological additive, so that the melt-blown processing property of the PET resin and the property of the melt-blown non-woven fabric are improved. At present, many auxiliary agents for improving the rheological properties of PET resins are available, including inorganic nano-powder, small organic molecules and partial oligomers. The basic principle is to weaken the interaction between high molecular chains. Although the addition of additives can be effective in improving the rheological properties of PET melt blown processing, other problems are often associated with the addition of additives. For example, the mechanical properties of the fibers are affected due to poor compatibility, breakage occurs in the hot air traction process, the fibers cannot be effectively stretched, the obtained non-woven fabric is poor in uniformity and low in breaking strength, the thermal stability is low, the addition of small molecules can well improve the rheological property of a melt, but the small molecules are unstable at high temperature and are easy to decompose or oxidize, so that the performance of the material is deteriorated, meanwhile, the addition of the small molecules can also reduce the strength of the melt, the filaments are easy to break in the drawing process, the drawing is uneven, even the dripping phenomenon occurs in the spinning process, the two problems can be well solved by selecting proper oligomers, the processability of the melt is still limited to a certain extent, the melt index of the PET resin in the prior report is not more than 250g/10min (DOI: 10.3969/j. Isn. 1004-3918.2007.06.007), and the intrinsic viscosity of the modified PET composite resin is 0.5-1.2dL/g (CN 113186654A). The melt index and the intrinsic viscosity are taken as important parameters for measuring the processability of the melt, and the higher the value of the melt index and the better the melt strength, the better the processability, the more favorable the finer and more uniform fibers are obtained, and the important significance is provided for the application of the PET resin in melt blowing processing.

Disclosure of Invention

In order to solve the problems of high processing temperature and poor melt fluidity when the PET resin is used for melt blowing, the invention provides the special PET resin for melt blowing and the preparation method thereof, and HBPET is added into the PET resin as a plasticizer, so that the rheological property of the PET resin is greatly improved, the melt blowing processing property of PET is improved, the melt strength of the PET melt can be kept higher all the time in the melt blowing processing process, and the PET melt can be fully drawn after leaving a spinneret orifice, so that finer and stronger fiber products are obtained.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

the PET resin special for melt blowing comprises HBPET/PET composite resin master batch and pure PET resin as raw materials, wherein HBPET is hyperbranched high molecular polyester with a carboxyl end group structure, the quantity of carboxyl end groups accounts for 25-100% of the total quantity of end groups, the branching degree is 30-100%, and the mass ratio of HBPET in the raw materials is 0.1-3%, and more preferably 0.3-1%.

Preferably, the pure PET resin is a slice, and the hyperbranched polymer polyester is mainly composed of C and H except for O of carboxyl and hydroxyl.

Preferably, the relative molecular weight of HBPET in HBPET/PET composite resin master batch is 1100-50000g/mol, and the carboxyl end group content is 1000-4000mol/t.

Preferably, the mass ratio of HBPET in HBPET/PET composite resin master batch is 1-10%, more preferably 3%, and the mass ratio of HBPET/PET composite resin master batch in raw materials is 10-30%.

Preferably, the melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃. The melt-blowing processing temperature is 260-270 ℃, and the initial decomposition temperature of the special PET resin for melt-blowing is far higher than the melt-blowing processing temperature, so that the requirement of the melt-blowing temperature can be met.

The invention also provides a preparation method of the PET resin special for melt blowing, which comprises the following steps:

(1) Melting and blending HBPET and PET to prepare HBPET/PET composite resin master batch;

(2) And mixing HBPET/PET composite resin master batch and pure PET resin slices, and carrying out melting, mixing and granulating to obtain the PET resin special for melt blowing.

Preferably, the HBPET in the step (1) is dried in a vacuum oven at 30-60 ℃ for more than 24 hours.

Preferably, the HBPET and PET in the step (1) are mixed in powder form, and mixed in a high-speed mixer at a rotation speed of 1300-1500r/min for 3-5min.

As a further preference, the inner wall of the high-speed mixer is cleaned every 1-2 min. HBPET contains a large amount of terminal carboxyl groups, so HBPET has strong hygroscopicity. Prevent HBPET from adhering to PET powder to form a block after absorbing water.

Preferably, the step (1) adopts a double-screw extruder to prepare HBPET/PET composite resin master batch.

Preferably, the HBPET/PET composite resin master batch and the pure PET resin slices in the step (2) are dried in a vacuum oven at 150-170 ℃ for 7-9 hours, cooled to room temperature and mixed.

Preferably, the mixing temperature in the step (2) is 20-60 ℃, the mixing time is 10-15min, and the mixing is carried out in a high-speed mixer with the speed of 1300-1500 r/min.

Preferably, the granulating in the step (2) adopts double-screw extrusion granulating, wherein the temperature of each region in the screw extrusion process is 170-270 ℃, the temperature of a machine head is 250-260 ℃, and the rotating speed of the screw is 390-420r/min.

The invention has the beneficial effects that hyperbranched high molecular polyester (HBPET) with a carboxyl end structure is taken as a rheology modifier, HBPET/PET composite resin is prepared by a melt blending method, and HBPET/PET composite resin is taken as master batch to be blended with pure PET resin to prepare the special melt-blown PET resin. HBPET enables the thermal stability of the PET resin special for melt blowing to be obviously enhanced compared with that of pure PET resin, the decomposition temperature is greatly improved compared with that of the pure PET resin, the decomposition temperature is more than 290 ℃, the melt blowing processing temperature is far higher than that of the PET resin, the melt processing temperature is obviously reduced (the processing temperature is reduced by about 10 ℃), and the requirement on the thermal stability of PET in melt blowing processing can be met.

Detailed Description

The technical scheme of the invention is further described through specific embodiments.

In the present invention, unless otherwise specified, the materials and equipment used are commercially available or are commonly used in the art, and the methods in the examples are conventional in the art unless otherwise specified.

A PET resin special for melt-blowing comprises HBPET/PET composite resin master batch and pure PET resin slices. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

The mass ratio of HBPET in the raw material is 0.1-3% (more preferably 0.5%). The melt index is increased and then reduced with the increase of HBPET content, when HBPET content is 0.5%, the complex viscosity of PET composite resin is reduced to over 390g/10min, with the increase of angular frequency, the phenomenon of 'shear thinning' appears, with the increase of shear rate and the increase of temperature, the apparent viscosity of PET composite resin is reduced, the main reasons are that the molecular weight distribution of PET resin is widened after HBPET with low molecular weight is added, the HBPET with low molecular weight plays an internal plasticization role, furthermore, the interaction among PET molecular chains is reduced by HBPET, HBPET hyperbranched polyester takes a spherical shape, the entanglement points among PET molecular chains are destroyed, the viscosity is rapidly reduced under the shearing action, meanwhile, the short molecular chains are easy to orient under the high shearing action, the internal plasticization role is further enhanced, the relaxation time of PET long molecular chains is long, the oriented molecules in the flowing are not easy to relax, retract and orient, the flowing resistance is reduced, and the viscosity is reduced. Therefore, PET composite resin added with HBPET can be used as a raw material for melt-blowing processing.

Preferably, the mass ratio of HBPET in HBPET/PET composite resin master batch is 1-10% (more preferably 3%), and the mass ratio of HBPET/PET composite resin master batch in raw material is 10-30%. The higher the HBPET content, the more pronounced the moisture absorption of the mixture. The higher water content in the mixture can lead to difficult feeding, can not carry out strand granulation on the resin to affect processing, and simultaneously, the water can lead to degradation of the polyester at high temperature to affect the performance of the product.

HBPET is hyperbranched high molecular polyester with a carboxyl end structure, the carboxyl end content is 1000-4000mol/t, the quantity of carboxyl end accounts for 25-100% of the total quantity of end groups, the branching degree is 30-100%, the relative molecular weight is 1100-50000g/mol, the carboxyl end content is 1000-4000mol/t, the molecular formula is shown as the following formula except for O of carboxyl and hydroxyl, and the molecule mainly comprises C and H:

The hyperbranched high molecular polyester is prepared by using a M2+M3 synthesis method, M2 is a monomer containing two reactive groups, at least 1 of the monomers is carboxyl, and M3 is a monomer containing three reactive hydroxyl groups. Preferably, the M2 is pyrazine-2, 3-dicarboxylic acid, 2-carboxyethylphenyl phosphinic acid, 5-tert-butyl-1, 3-benzene dicarboxylic acid or 2-carboxyethylphosphoric acid, [ (6-oxo-6H-dibenzo [ c, e ] [1,2] oxaphosphorin-6-yl) methyl ] butanedioic acid, and the M3 is 1, 1-tris (hydroxymethyl) propane, tris (2-hydroxyethyl) isocyanurate, 2,4, 5-trihydroxybenzene butanone, 2,3, 4-trihydroxybenzophenone or 1,2, 4-trihydroxybenzene.

HBPET A is prepared by referring to the preparation method of the A substance in the patent CN109721968B, specifically, "the pyrazine-2, 3-dicarboxylic acid and the 1, 1-tri (hydroxymethyl) propane with the molar ratio of 1:1 are subjected to esterification reaction for 1h under the protection of nitrogen at the temperature of 150 ℃, and then are subjected to polycondensation reaction for 4h under the conditions of 200 ℃ and the pressure of 0MPa by vacuumizing, wherein stirring is needed in the processes of the esterification reaction and the polycondensation reaction, and the stirring speed is 200rpm. "

(1) Drying HBPET powder in a vacuum oven at 30-60 ℃ for more than 24 hours, mixing with PET powder in a high-speed mixer at a rotating speed of 1300-1500r/min for 3-5min, cleaning the inner wall of the high-speed mixer once every 1-2min in order to prevent the powder from adhering to the PET powder into a block after HBPET absorbs water, extruding the powder by a double-screw extruder, cooling the melt extruded by a water tank, and granulating by a granulator to obtain HBPET/PET composite resin master batch.

(2) Drying HBPET/PET composite resin master batch and pure PET resin slice in a vacuum oven at 150-170 ℃ for 7-9h, cooling to room temperature, mixing in a high-speed mixer at 1300-1500r/min for 10-15min and 20-60 ℃, and granulating by twin-screw extrusion, wherein the temperature of each zone in the screw extrusion process is 170-270 ℃, the temperature of a machine head is 250-260 ℃ and the screw rotation speed is 390-420r/min, thus obtaining granular special PET resin for melt blowing.

Example 1

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (10% by mass and the same applies below) and 90% pure PET resin slices. The mass ratio of HBPET in HBPET/PET composite resin master batch is 1%, and the mass ratio of HBPET in the raw material after folding is 0.1%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

HBPET is hyperbranched polymer with carboxyl end structure, the carboxyl end content is 1000-4000mol/t, the quantity of carboxyl end accounts for 25-100% of the total quantity of end groups, the branching degree is 30-100%, the relative molecular weight is 1100-50000g/mol, and the hyperbranched polymer is composed of C and H except for O of carboxyl and hydroxyl.

The preparation method of the PET resin special for melt blowing comprises the following steps:

(1) And carrying out vacuum drying on HBPET powder for 24 hours at the temperature of 30 ℃, mixing the dried HBPET powder with PET powder in a high-speed mixer at the rotating speed of 1400r/min for 5min, and cleaning the inner wall of the high-speed mixer once every 1min in order to prevent the powder from being adhered to the PET powder into a block after HBPET absorbs water. Extruding by a double-screw extruder, cooling the melt after extruding by a water tank, and granulating by a granulator to obtain HBPET mass percent HBPET/PET composite resin master batch.

(2) HBPET/PET composite resin master batch and pure PET resin slices were dried in a vacuum oven at 160℃for 8h, respectively, and cooled to room temperature. Pre-mixing HBPET/PET master batch and pure PET resin slices in a high-speed mixer, wherein the mass ratio of HBPET/PET master batch is 10%, the mixing temperature is 20 ℃, the mixing time is 10min, and the rotating speed of the high-speed mixer is 1400r/min. The processing technological parameters in the twin-screw extruder are controlled to be that the temperatures of a first region to a seventh region of the screw are 240 ℃, 270 ℃, 268 ℃, 263 ℃, 258 ℃ and 258 ℃ respectively, the temperature of a machine head is 258 ℃, and the rotating speed of the screw is 400r/min, so that the granular special PET resin for melt blowing is prepared.

Example 2

The difference from example 1 is that HBPET accounts for 3% of the mass of HBPET/PET composite resin master batch, and HBPET accounts for 0.3% of the mass of the raw material after folding.

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (10% by mass and the same applies below) and 90% pure PET resin slices. The mass ratio of HBPET in HBPET/PET composite resin master batch is 3%, and the mass ratio of HBPET in the raw material after folding is 0.3%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

HBPET is hyperbranched polymer with carboxyl end structure, the carboxyl end content is 1000-4000mol/t, the quantity of carboxyl end accounts for 25-100% of the total quantity of end groups, the branching degree is 30-100%, the relative molecular weight is 1100-50000g/mol, and the molecule is mainly composed of C and H except the O of carboxyl and hydroxyl.

Example 3

The difference from example 1 is that HBPET% by mass of the HBPET/PET composite resin master batch is equal to 0.5% by mass of HBPET after folding.

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (10% by mass and the same applies below) and 90% pure PET resin slices. The mass ratio of HBPET% in HBPET/PET composite resin master batch is 5%, and the mass ratio of HBPET in the raw material after folding is 0.5%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

(1) And carrying out vacuum drying on HBPET powder for 24 hours at the temperature of 30 ℃, mixing the dried HBPET powder with PET powder in a high-speed mixer at the rotating speed of 1400r/min for 5min, and cleaning the inner wall of the high-speed mixer once every 1min in order to prevent the powder from being adhered to the PET powder into a block after HBPET absorbs water. Extruding by a double-screw extruder, cooling the melt after extruding by a water tank, and granulating by a granulator to obtain HBPET% HBPET/PET composite resin master batch.

Example 4

The difference from example 1 is that HBPET mass percent in HBPET/PET composite resin master batch is 7.5 mass percent, and HBPET mass percent in raw material after folding is 0.75 mass percent.

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (10% by mass and the same applies below) and 90% pure PET resin slices. The mass ratio of HBPET in HBPET/PET composite resin master batch is 7.5%, and the mass ratio of HBPET in the raw material after folding is 0.75%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

Example 5

The difference from example 1 is that HBPET accounts for 10% of the mass of HBPET/PET composite resin master batch, and HBPET accounts for 1% of the mass of the raw material after folding.

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (10% by mass and the same applies below) and 90% pure PET resin slices. The mass ratio of HBPET in HBPET/PET composite resin master batch is 10%, and the mass ratio of HBPET in the raw material after folding is 1%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

Example 6

The difference from example 1 is that HBPET mass percent in HBPET/PET composite resin master batch is 30 percent, and the mass percent of HBPET after folding in the raw material is 3 percent.

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (10% by mass and the same applies below) and 90% pure PET resin slices. The mass ratio of HBPET in HBPET/PET composite resin master batch is 30%, and the mass ratio of HBPET in the raw material after folding is 3%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

(2) HBPET/PET composite resin master batch and pure PET resin slices were dried in a vacuum oven at 160℃for 8h, respectively, and cooled to room temperature. Pre-mixing HBPET/PET master batch and pure PET resin slices in a high-speed mixer, wherein the mass ratio of HBPET/PET master batch is 30%, the mixing temperature is 20 ℃, the mixing time is 10min, and the rotating speed of the high-speed mixer is 1400r/min. The processing technological parameters in the twin-screw extruder are controlled to be that the temperatures of a first region to a seventh region of the screw are 240 ℃, 270 ℃, 268 ℃, 263 ℃, 258 ℃ and 258 ℃ respectively, the temperature of a machine head is 258 ℃, and the rotating speed of the screw is 400r/min, so that the granular special PET resin for melt blowing is prepared.

Example 7

The difference from example 3 is that the mixing time in step (2) was 15min and the screw speed was 410r/min.

(2) HBPET/PET composite resin master batch and pure PET resin slices were dried in a vacuum oven at 160℃for 8h, respectively, and cooled to room temperature. Pre-mixing HBPET/PET master batch and pure PET resin slices in a high-speed mixer, wherein the mass ratio of HBPET/PET master batch is 10%, the mixing temperature is 20 ℃, the mixing time is 15min, and the rotating speed of the high-speed mixer is 1400r/min. The processing technological parameters in the twin-screw extruder are controlled to be that the temperatures of a first region to a seventh region of the screw are 240 ℃, 270 ℃, 268 ℃, 263 ℃, 258 ℃ and 258 ℃ respectively, the temperature of a machine head is 258 ℃, and the rotating speed of the screw is 410r/min, so that the granular special PET resin for melt blowing is prepared.

Example 8

A PET resin special for melt-blowing is prepared from HBPET/PET composite resin mother particles (30% by mass and the same applies below) and 70% pure PET resin slices. The mass ratio of HBPET in HBPET/PET composite resin master batch is 1%, and the mass ratio of HBPET in the raw material after folding is 0.3%. The melting point of the special PET resin for melt blowing is 249-253 ℃, and the initial decomposition temperature is higher than 290 ℃.

HBPET accounts for 0.1% of the total mass of the HBPET/PET composite resin master batch. HBPET is hyperbranched polymer with a carboxyl-terminated structure, the carboxyl-terminated content is 4000mol/t, the quantity of carboxyl-terminated groups accounts for 25% of the total quantity of end groups, the branching degree is 100%, the relative molecular weight is 50000g/mol, and the molecules are mainly composed of C and H except for O of carboxyl and hydroxyl.

The preparation method comprises the following steps:

(1) And carrying out vacuum drying on HBPET powder for 24 hours at 50 ℃, mixing the dried HBPET powder with PET powder in a high-speed mixer at a rotating speed of 1300r/min for 4min, and cleaning the inner wall of the high-speed mixer once every 2min in order to prevent the powder from being adhered to the PET powder into a block after HBPET absorbs water. Extruding by a double-screw extruder, cooling the melt after extruding by a water tank, and granulating by a granulator to obtain HBPET mass percent HBPET/PET composite resin master batch.

(2) The HBPET/PET composite resin master batch and the pure PET resin slice are dried in a vacuum oven at 150 ℃ for 9 hours, cooled to room temperature, and HBPET/PET master batch and the pure PET resin slice are premixed in a high-speed mixer, wherein the mass ratio of HBPET/PET master batch is 30%, the mixing temperature is 40 ℃, the mixing time is 13 minutes, and the rotating speed of the high-speed mixer is 1300r/min. The processing technological parameters in the twin-screw extruder are controlled to be that the temperatures of a first region to a seventh region of the screw are 240 ℃, 270 ℃, 268 ℃, 263 ℃, 258 ℃ and 258 ℃ respectively, the temperature of a machine head is 250 ℃, and the rotating speed of the screw is 420r/min, so that the granular special PET resin for melt blowing is prepared.

Comparative example 1

A special PET resin for melt-blowing is prepared from pure PET resin slice. The preparation method comprises the following steps:

The pure PET resin slices are dried in a vacuum oven at 160 ℃ for 8 hours, and are added into a high-speed mixer for mixing after being cooled to room temperature. Mixing temperature is 20 ℃, mixing time is 10min, and premixing is carried out under the condition that the rotating speed of a high-speed mixer is set to 1400 r/min. The premix is added into a double-screw extruder, the processing technological parameters of the PET resin in the double-screw extruder are controlled to be that the temperatures of a first region to a seventh region of a screw are 240 ℃, 270 ℃, 268 ℃, 263 ℃, 258 ℃ and 258 ℃, the temperature of a machine head is 258 ℃, the rotating speed of the screw is 400r/min, and the melt is pelletized by a pelletizer after being extruded and cooled by a water tank, so that the pure granular PET resin is prepared.

Comparative example 2

The difference from example 1 is that HBPET mass percent in HBPET/PET composite resin master batch is 50 mass percent, and HBPET mass percent in raw material after folding is 5 mass percent.

Comparative example 3

The difference from example 1 is that HBPET has a carboxyl end group content of 20%.

Comparative example 4

The difference from example 1 is that HBPET has a branching degree of 25%.

Performance testing

The resins obtained in examples 1 to 8 and comparative examples 1 to 4 were dried and injection molded in a vertical injection molding machine to obtain a drawn bar, wherein the melt temperature, the mold temperature and the cooling time were set to 245 to 270 ℃, 25 ℃ and 20s, respectively. The resins were subjected to rheological tests of the melt index (test temperature 285 ℃ C., pressure 1.2 kg) and the apparent viscosity of the melt under shear (shear rate 1000s ^-1) of the chips at different temperatures. The resin was subjected to the following melt blowing process parameters to obtain a fibrous article, and its fiber diameter and fiber strength were compared. The melt-blown spinning process parameters are 265 ℃ in the first area of the screw, 265 ℃ in the second area of the screw, 270 ℃ in the third area of the screw, 275 ℃ in the fourth area of the screw, 275 ℃ in the filtering area, 275 ℃ in the metering pump, 275 ℃ in the first area of the die head, 280 ℃ in the second area of the die head, 285 ℃ in the third area of the die head, 285 ℃ in the fourth area of the die head, 330 ℃ in the traction air, 0.15MPa in the traction air pressure and 14cm in the receiving distance. The test results are shown in Table 1.

TABLE 1 Properties of the resins and meltblown fibers obtained in examples and comparative examples

As can be seen from the results in Table 1, the introduction of hyperbranched HBPET with the carboxyl end group structure characteristic can effectively improve the fluidity and melt processability of PET resin. The melt index of PET composite resin added with HBPET is improved to different degrees, and the shear viscosity is obviously reduced. As shown in example 3, when HBPET was 0.5% by mass in the feed, the melt index at 285℃and 1.2kg pressure was 396.8g/10min, which is much higher than the melt index of the virgin PET resin (73.5 g/10 min) at the same addition.

The apparent viscosity at 270 ℃ and 280 ℃ of the PET composite resin of each example and comparative example is compared, the apparent viscosity at the temperature is increased and the apparent viscosity at the time of melt blowing is reduced, but the apparent viscosity at the time of 270 ℃ of the PET composite resin added with HBPET is reduced obviously, and the apparent viscosity at the time of 280 ℃ of the pure PET resin is 74.5 Pa.s, so that the PET composite resin added with HBPET can be processed at lower temperature in the melt blowing process. The introduction of hyperbranched HBPET with the carboxyl end structure characteristics can effectively improve the fluidity of PET resin.

As the HBPET content increases, the melt index of the PET composite resin increases and then decreases, the apparent viscosity exhibits the opposite change, and when the HBPET content in the raw material is less than 0.5%, the melt index of the PET composite resin gradually increases and the shear apparent viscosity gradually decreases, because the introduction of HBPET reduces interactions between PET molecular chains, and the HBPET hyperbranched polyester takes the shape of spheres, is dispersed in the PET resin matrix, and the entanglement points between the damaged PET molecular chains rapidly decrease in viscosity under the shearing action. When the amount of HBPET added exceeds 1%, HBPET intertwines with each other, and interaction between HBPET and PET molecules is also enhanced, so that the viscosity of the melt is improved with the increase of HBPET content, the melt index of the PET composite resin is gradually reduced with the gradual increase of HBPET content, and the shear apparent viscosity is gradually increased. The excess HBPET content in comparative example 2, which was not granulated, indicates that HBPET content has a great effect on performance.

Compared with melt-blown fibers of different PET resins, under the same melt-blown condition, the PET composite resin added with HBPET has better melt processing performance, and the fibers obtained by melt-blown processing are finer and have better uniformity and higher mechanical strength. This is mainly due to HBPET with the structural characteristic of terminal carboxyl, and in the process of melt blowing and hot air traction, the terminal carboxyl in HBPET has strong interaction with hydroxyl and carboxyl in PET molecular chains, and the terminal carboxyl in HBPET can react with hydroxyl in PET molecular chains in a small molecule removal way to generate crosslinking, so that the PET melt always maintains higher melt strength in the process of melt blowing, and can be effectively stretched in the process of hot air traction to obtain finer and stronger fiber products, and the fibers also have higher breaking strength.

The HBPET carboxyl end group content in comparative example 3 was 20% below the preferred range, the HBPET branching degree in comparative example 4 was 25% below the preferred range, and the properties of the fiber product were significantly reduced, indicating that superior results were only achieved within the preferred range of the present invention.

In summary, the invention provides the PET composite resin special for melt blowing and the preparation method thereof, wherein hyperbranched polymers with the structural characteristics of terminal carboxyl groups are selected, so that the fluidity of PET melt is improved, and the melt can maintain good melt strength in the melt blowing processing process. In the post-processing process, a large number of hydroxyl groups and carboxyl end groups contained in the hyperbranched polymer can form strong physical interactions with the PET matrix, such as Van der Waals force, hydrogen bonds and the like, and the hydroxyl groups and carboxyl end groups contained in the hyperbranched polymer can react with the hydroxyl end groups and carboxyl end groups of PET molecular chains in the matrix to remove small molecular water under the action of melt and hot air to play a role of chemical crosslinking. When the above-mentioned action is used in melt-blowing processing, it can make melt always retain higher melt strength and stretchability, and is favorable for forming finer and stronger fibre products.

The present invention is not limited to the preferred embodiments, and the present invention is described above in any way, but is not limited to the preferred embodiments, and any person skilled in the art will appreciate that the present invention is not limited to the embodiments described above, while the above disclosure is directed to various equivalent embodiments, which are capable of being modified or varied in several ways, any simple modification, equivalent changes and variation of the above embodiments according to the technical principles of the present invention will still fall within the scope of the present invention.

Claims

1. A PET resin special for melt blowing is characterized in that raw materials comprise HBPET/PET composite resin master batch and pure PET resin, HBPET is hyperbranched high molecular polyester with a carboxyl end group structure, the quantity of carboxyl end groups accounts for 25-100% of the total quantity of end groups, the branching degree is 30-100%, and the mass ratio of HBPET in the raw materials is 0.1-3%.

2. The special melt-blown PET resin according to claim 1, wherein the relative molecular weight of HBPET in HBPET/PET composite resin master batch is 1100-50000 g/mol, and the carboxyl end group content is 1000-4000 mol/t.

3. The special PET resin for melt blowing according to claim 1, wherein the mass ratio of HBPET in HBPET/PET composite resin master batch is 1-10%, and the mass ratio of HBPET/PET composite resin master batch in raw materials is 10-30%.

4. A melt blown special PET resin according to claim 1 or 2 or 3, wherein the melt blown special PET resin has a melting point of 249-253 ℃, and an initial decomposition temperature of higher than 290 ℃.

5. A process for preparing a PET resin special for melt-blowing according to any one of claims 1 to 4, which comprises the steps of (1) melt blending HBPET and PET to prepare HBPET/PET composite resin master batch;

6. The method for preparing a special PET resin for melt-blown according to claim 5, wherein the HBPET in the step (1) is dried in a vacuum oven at 30-60 ℃ for 24-h or more.

7. The method for preparing the special melt-blown PET resin according to claim 5 or 6, wherein in the step (1), HBPET and PET are mixed in the form of powder, and mixed in a high-speed mixer at a rotation speed of 1300-1500 r/min for 3-5 min, and the inner wall of the high-speed mixer is cleaned every 1-2 min.

8. The method for preparing the PET resin special for melt blowing according to claim 5, wherein the steps (2) HBPET/PET composite resin master batch and pure PET resin slices are dried in a vacuum oven at 150-170 ℃ for 7-9 h, cooled to room temperature and mixed.

9. The method for preparing a special PET resin for melt blowing according to claim 5, wherein the mixing temperature in the step (2) is 20-60 ℃, the mixing time is 10-15 min, and the mixing is carried out in a 1300-1500 r/min high-speed mixer.

10. The method for preparing a special PET resin for melt blowing according to claim 1, 8 or 9, wherein the pelleting in the step (2) is carried out by adopting twin-screw extrusion, the temperature of each zone in the screw extrusion process is 170-270 ℃, the temperature of a machine head is 250-260 ℃, and the rotating speed of the screw is 390-420 r/min.