Special PET (Polyethylene Terephthalate) resin for melt blowing and preparation method thereof

Abstract

The invention relates to the technical field of melt-blowing, and provides a PET resin special for melt-blowing and a preparation method thereof, aiming at the problems of high processing temperature and poor melt flowability during melt-blowing of PET resin, the PET resin special for melt-blowing comprises the following raw materials: HBPET / PET composite resin master batch and pure PET resin slices; hBPET is hyperbranched polymer polyester with a terminal carboxyl group structure, the number of terminal carboxyl groups accounts for 25-100% of the total amount of terminal groups, and the branching degree is 30-100%; the mass ratio of the HBPET in the raw materials is 0.1-3%. According to the invention, the rheological property of PET resin can be improved, the melt-blowing processability of PET can be improved, the PET melt can keep higher melt strength, and finer and stronger fiber products can be obtained. The invention also provides a preparation method of the PET resin special for melt-blowing, which comprises the following steps: carrying out melt blending on the HBPET and the PET to prepare master batches, and carrying out mixed melting, mixing and granulation on the master batches and the pure PET resin slices.

Description

Technical Field

[0001] The invention relates to the field of melt-blowing technology, in particular to a PET resin dedicated to melt-blowing and a preparation method thereof. Background Art

[0002] Meltblown fabrics use polypropylene (PP) as the main raw material, and polyethylene terephthalate (PET) is the second largest raw material after PP. Compared with PP, PET has higher mechanical strength and chemical stability, and is an excellent choice for meltblown processing raw materials, and its cost is lower. However, the linear molecular structure of PET leads to its poor processability and low crystallization rate. At the same time, the higher melting point makes the processing temperature of PET high, and the higher processing temperature causes thermal degradation of PET, which seriously affects the performance of PET products.

[0003] In melt-blowing processing, melt fluidity is the key to melt-blowing material processing. Since melt-blowing processing requires the use of hot air flow to stretch the polymer melt extruded from the spinneret, the raw material is required to have low melt viscosity, good fluidity and thermal stability at the melting temperature. However, directly using PET resin for filament melt spinning in melt-blowing processing has high viscosity and poor fluidity. The temperature required for melt-blowing processing is high, the energy consumption is large, and the performance of the product is not ideal.

[0004] The rheological properties of PET resin can be regulated by adding rheological additives, thereby improving the melt-blown processing performance of PET resin and the properties of melt-blown nonwoven fabrics. At present, there are many additives used to improve the rheological properties of PET resin, including inorganic nanopowders, organic small molecules and some oligomers. The basic principle is to weaken the interaction between polymer chains. Although the addition of additives can effectively improve the rheological properties of PET during melt-blown processing, it often brings other problems. For example: poor compatibility will affect the mechanical properties of the fiber, causing it to break during hot air drawing and unable to be effectively stretched. The resulting non-woven fabric has poor fiber uniformity and low breaking strength; thermal stability issues: the addition of small molecules can greatly improve the melt rheology, but small molecules are often unstable at high temperatures and are easily decomposed or oxidized, resulting in deterioration of the material's performance. At the same time, the addition of small molecules will also reduce the melt strength, making it easy to break the wire during the drawing process, uneven drawing, and even dripping during the spinning process; choosing a suitable oligomer can better solve the above two problems, but the processability of the melt is still subject to certain restrictions. In existing reports, the melt index of PET resin does not exceed 250g / 10min (DOI: 10.3969 / j.issn.1004-3918.2007.06.007), and the intrinsic viscosity of the modified PET composite resin is 0.5-1.2dL / g (CN113186654A). Melt index and intrinsic viscosity are important parameters for measuring melt processability. The higher the melt index value and the better the melt strength, the better the processability and the more conducive to obtaining finer and more uniform fibers, which is of great significance for the application of PET resin in meltblowing processing. Summary of the invention

[0005] In order to overcome the problems of high processing temperature and poor melt fluidity of PET resin when used for melt blowing, the present invention provides a PET resin dedicated to melt blowing and a preparation method thereof. HBPET is added to the PET resin as a plasticizer, which not only greatly improves the rheological properties of the PET resin and improves the melt blowing processing performance of PET, but also enables the PET melt to always maintain a high melt strength during the melt blowing process, so as to ensure that the PET melt can be fully stretched after leaving the spinneret hole, so as to obtain a thinner and stronger fiber product.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A PET resin specially used for meltblowing, wherein the raw materials include HBPET / PET composite resin masterbatch and pure PET resin; the HBPET is a hyperbranched high molecular polyester with a terminal carboxyl structure, wherein the number of terminal carboxyl groups accounts for 25-100% of the total number of terminal groups, and the degree of branching is 30-100%; the mass proportion of HBPET in the raw materials is 0.1-3%, and more preferably 0.3-1%.

[0007] Preferably, the pure PET resin is in the form of chips; the hyperbranched polymer polyester is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0008] Preferably, the relative molecular weight of HBPET in the HBPET / PET composite resin masterbatch is 1100-50000 g / mol, and the terminal carboxyl content is 1000-4000 mol / t.

[0009] Preferably, the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 1-10%, and more preferably 3%; the mass proportion of HBPET / PET composite resin masterbatch in the raw material is 10-30%.

[0010] Preferably, the melting point of the PET resin for meltblowing is 249-253° C., and the initial decomposition temperature is higher than 290° C. The meltblowing processing temperature is 260-270° C., and the initial decomposition temperature of the PET resin for meltblowing is much higher than the meltblowing processing temperature, which can meet the meltblowing temperature requirements.

[0011] The present invention also provides a method for preparing the melt-blown special PET resin, comprising the following steps: (1) melt-blending HBPET and PET to prepare HBPET / PET composite resin masterbatch; (2) HBPET / PET composite resin masterbatch and pure PET resin chips are mixed, melted, mixed and granulated to obtain a PET resin for meltblowing.

[0012] Preferably, the HBPET in step (1) is first dried in a vacuum oven at 30-60° C. for more than 24 hours.

[0013] Preferably, in step (1), HBPET and PET are mixed in powder form and mixed in a high-speed mixer at a speed of 1300-1500 r / min for 3-5 min.

[0014] As a further preference, the inner wall of the high-speed mixer is cleaned every 1-2 minutes. HBPET contains a large number of terminal carboxyl groups, so HBPET has strong hygroscopicity. This prevents HBPET from adhering to PET powder to form lumps after absorbing water.

[0015] Preferably, in step (1), a twin-screw extruder is used to prepare the HBPET / PET composite resin masterbatch.

[0016] Preferably, in step (2), the HBPET / PET composite resin masterbatch and the pure PET resin chips are first dried in a vacuum oven at 150-170° C. for 7-9 hours, cooled to room temperature, and then mixed.

[0017] Preferably, the mixing temperature in step (2) is 20-60° C., the mixing time is 10-15 min, and the mixing is carried out in a high-speed mixer at 1300-1500 r / min.

[0018] Preferably, the granulation in step (2) is carried out by twin-screw extrusion granulation, and during the screw extrusion process, the temperature of each zone is 170-270°C, the head temperature is 250-260°C, and the screw speed is 390-420r / min.

[0019] Therefore, the beneficial effects of the present invention are as follows: using a hyperbranched polymer polyester (HBPET) with a carboxyl-terminated structure as a rheology modifier, preparing a HBPET / PET composite resin by a melt blending method; using the HBPET / PET composite resin as a masterbatch and blending it with a pure PET resin to prepare a melt-blown PET resin. HBPET significantly enhances the thermal stability of the melt-blown PET resin compared to pure PET resin, and greatly increases the decomposition temperature compared to pure PET resin, reaching more than 290°C, which is much higher than its melt-blown processing temperature, and significantly reduces the melt processing temperature (the processing temperature is reduced by about 10°C), which can meet the requirements for the thermal stability of PET in melt-blown processing. DETAILED DESCRIPTION

[0020] The technical solution of the present invention is further described below through specific embodiments.

[0021] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art.

[0022] A PET resin for melt-blowing, the raw materials include HBPET / PET composite resin masterbatch and pure PET resin chips. The melting point of the PET resin for melt-blowing is 249-253°C, and the initial decomposition temperature is higher than 290°C.

[0023] The mass proportion of HBPET in the raw material is 0.1-3% (more preferably 0.5%). With the increase of HBPET content, the structural viscosity index decreases, and the melt index increases first and then decreases. When the content of HBPET is 0.5%, it reaches more than 390g / 10min; with the increase of angular frequency, the complex viscosity of PET composite resin decreases, and the phenomenon of "shear thinning" occurs; with the increase of shear rate and the increase of temperature, the apparent viscosity of PET composite resin decreases, and the main reason is that the molecular weight distribution of PET resin becomes wider after the addition of low molecular weight HBPET, and low molecular weight HBPET plays an internal plasticizing role in it; in addition, the introduction of HBPET reduces the interaction between PET molecular chains, and the HBPET hyperbranched polyester is spherical and dispersed in the PET resin matrix, destroying the entanglement points between PET molecular chains, and the viscosity decreases rapidly under shear action. At the same time, under high shear action, short molecular chains are easy to orient, which further enhances the internal plasticizing effect; in addition, the relaxation time of PET long molecular chains is long, and the molecules that have been oriented in the flow are not easy to relax, shrink and de-orient, so that the flow resistance is reduced and the viscosity is reduced. Therefore, the PET composite resin after adding HBPET can be used as the raw material for melt-blowing processing.

[0024] Preferably, the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 1-10% (more preferably 3%); the mass proportion of HBPET / PET composite resin masterbatch in the raw material is 10-30%. The higher the content of HBPET, the more obvious the moisture absorption of the mixture. A high water content in the mixture will lead to difficulty in feeding, and the resin cannot be stretched and pelletized, which affects processing; at the same time, moisture will also cause polyester to degrade at high temperature, affecting the performance of its products.

[0025] HBPET is a hyperbranched high molecular weight polyester with a carboxyl terminal structure, with a carboxyl terminal content of 1000-4000 mol / t, the number of carboxyl terminal groups accounts for 25-100% of the total number of terminal groups, and a branching degree of 30-100%; the relative molecular weight is 1100-50000 g / mol, and the carboxyl terminal content is 1000-4000 mol / t; except for the O of the carboxyl and hydroxyl groups, the molecule is mainly composed of C and H, and the molecular formula is shown below: The hyperbranched polymer polyester is prepared by the M2+M3 synthesis method, wherein M2 is a monomer containing two reactive groups, at least one of which is a carboxyl group, and M3 is a monomer containing three reactive hydroxyl groups. Preferably, M2 is pyrazine-2,3-dicarboxylic acid, 2-carboxyethylphenylphosphinic acid, 5-tert-butyl-1,3-benzenedicarboxylic acid or 2-carboxyethylphosphoric acid, [(6-oxo-6H-dibenzo[c,e][1,2]oxaphosphorin-6-yl)methyl]succinic acid; and M3 is 1,1,1-tri(hydroxymethyl)propane, tris(2-hydroxyethyl)isocyanurate, 2,4,5-trihydroxybutyrophenone, 2,3,4-trihydroxyacetophenone or 1,2,4-trihydroxybenzene.

[0026] The preparation method of HBPET refers to the preparation method of substance A in patent CN109721968B, which is specifically "esterification reaction of pyrazine-2,3-dicarboxylic acid and 1,1,1-tri(hydroxymethyl)propane in a molar ratio of 1:1 at a temperature of 150°C under nitrogen protection for 1 hour, and then vacuum polycondensation reaction at a temperature of 200°C and a pressure of 0 MPa for 4 hours to obtain HBPET, wherein stirring is required during the esterification reaction and polycondensation reaction, and the stirring rate is 200 rpm." The present invention also provides a method for preparing a melt-blown special PET resin, comprising the following steps: (1) Drying HBPET powder in a vacuum oven at 30-60°C for more than 24 hours, and then mixing it with PET powder in a high-speed mixer at a speed of 1300-1500 r / min for 3-5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer is cleaned every 1-2 minutes; extruding through a twin-screw extruder, cooling the melt in a water tank, and then pelletizing it with a pelletizer to obtain HBPET / PET composite resin masterbatch.

[0027] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips are first dried in a vacuum oven at 150-170°C for 7-9h, cooled to room temperature, and then mixed in a high-speed mixer at a speed of 1300-1500r / min for 10-15min, and the mixing temperature is 20-60°C; then twin-screw extrusion is used for granulation, and the temperature of each zone during the screw extrusion process is 170-270°C, the head temperature is 250-260°C, and the screw speed is 390-420r / min, to obtain granular PET resin for melt-blowing.

[0028] Example 1 A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 90% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 1%, and the mass percentage of HBPET in the raw material after conversion is 0.1%. The melting point of the PET resin for meltblowing is 249-253°C, and the initial decomposition temperature is higher than 290°C.

[0029] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and it is composed of C and H except for the O of carboxyl and hydroxyl groups.

[0030] The preparation method of PET resin for melt-blown is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 1%.

[0031] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 10%, the mixing temperature being 20°C, the mixing time being 10 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 400r / min, to obtain granular PET resin for meltblowing.

[0032] Example 2 The difference from Example 1 is that the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 3%, and the mass proportion of HBPET in the raw material after conversion is 0.3%.

[0033] A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) HBPET / PET composite resin masterbatch and 90% pure PET resin slices. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 3%, and the mass percentage of HBPET in the raw material after conversion is 0.3%. The melting point of the PET resin for meltblowing is 249-253℃, and the initial decomposition temperature is higher than 290℃.

[0034] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and the molecule is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0035] The preparation method of PET resin for melt-blowing is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 3%.

[0036] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 10%, the mixing temperature being 20°C, the mixing time being 10 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 400r / min, to obtain granular PET resin for meltblowing.

[0037] Example 3 The difference from Example 1 is that the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 5%, and the mass proportion of HBPET in the raw material after conversion is 0.5%.

[0038] A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 90% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 5%, and the mass percentage of HBPET in the raw material after conversion is 0.5%. The melting point of the PET resin for meltblowing is 249-253℃, and the initial decomposition temperature is higher than 290℃.

[0039] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and the molecule is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0040] The preparation method of PET resin for melt-blowing is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 5%.

[0041] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 10%, the mixing temperature being 20°C, the mixing time being 10 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 400r / min, to obtain granular PET resin for meltblowing.

[0042] Example 4 The difference from Example 1 is that the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 7.5%, and the mass proportion of HBPET in the raw material after conversion is 0.75%.

[0043] A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 90% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 7.5%, and the mass percentage of HBPET in the raw material after conversion is 0.75%. The melting point of the PET resin for meltblowing is 249-253℃, and the initial decomposition temperature is higher than 290℃.

[0044] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and the molecule is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0045] The preparation method of PET resin for melt-blowing is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 7.5%.

[0046] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 10%, the mixing temperature being 20°C, the mixing time being 10 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 400r / min, to obtain granular PET resin for meltblowing.

[0047] Example 5 The difference from Example 1 is that the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 10%, and the mass proportion of HBPET in the raw material after conversion is 1%.

[0048] A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 90% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 10%, and the mass percentage of HBPET in the raw material after conversion is 1%. The melting point of the PET resin for meltblowing is 249-253°C, and the initial decomposition temperature is higher than 290°C.

[0049] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and the molecule is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0050] The preparation method of PET resin for melt-blown is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 10%.

[0051] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 10%, the mixing temperature being 20°C, the mixing time being 10 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 400r / min, to obtain granular PET resin for meltblowing.

[0052] Example 6 The difference from Example 1 is that the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 30%, and the mass proportion of HBPET in the raw material after conversion is 3%.

[0053] A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 90% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 30%, and the mass percentage of HBPET in the raw material after conversion is 3%. The melting point of the PET resin for meltblowing is 249-253℃, and the initial decomposition temperature is higher than 290℃.

[0054] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and the molecule is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0055] The preparation method of PET resin for melt-blown is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 10%.

[0056] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 30%, the mixing temperature being 20°C, the mixing time being 10 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 400r / min, to obtain granular PET resin for meltblowing.

[0057] Example 7 The difference from Example 3 is that in step (2), the mixing time is 15 min and the screw speed is 410 r / min.

[0058] A PET resin for meltblowing, the raw material is composed of 10% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 90% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 5%, and the mass percentage of HBPET in the raw material after conversion is 0.5%. The melting point of the PET resin for meltblowing is 249-253℃, and the initial decomposition temperature is higher than 290℃.

[0059] HBPET is a hyperbranched high molecular weight polyester with a terminal carboxyl structure. The terminal carboxyl content is 1000-4000 mol / t, the number of terminal carboxyl groups accounts for 25-100% of the total terminal groups, the degree of branching is 30-100%, the relative molecular weight is 1100-50000 g / mol, and the molecule is mainly composed of C and H except for the O of the carboxyl and hydroxyl groups.

[0060] The preparation method of PET resin for melt-blowing is as follows: (1) HBPET powder was vacuum dried at 30°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1400 r / min for 5 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 1 minute. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 5%.

[0061] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 160°C for 8 hours and cooled to room temperature. The HBPET / PET masterbatch and pure PET resin chips were pre-mixed in a high-speed mixer, with the mass proportion of HBPET / PET masterbatch being 10%, the mixing temperature being 20°C, the mixing time being 15 minutes, and the speed of the high-speed mixer being set to 1400r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 258°C, and the screw speed was 410r / min, to obtain granular PET resin for meltblowing.

[0062] Example 8 A PET resin for meltblowing, the raw material is composed of 30% (mass percentage, the same below) of HBPET / PET composite resin masterbatch and 70% of pure PET resin chips. The mass percentage of HBPET in the HBPET / PET composite resin masterbatch is 1%, and the mass percentage of HBPET in the raw material after conversion is 0.3%. The melting point of the PET resin for meltblowing is 249-253℃, and the initial decomposition temperature is higher than 290℃.

[0063] In the HBPET / PET composite resin masterbatch, the mass proportion of HBPET is 0.1%. HBPET is a hyperbranched high molecular polyester with a terminal carboxyl structure, the terminal carboxyl content is 4000 mol / t, the number of terminal carboxyl accounts for 25% of the total terminal, the branching degree is 100%, the relative molecular weight is 50000 g / mol, and the molecule is mainly composed of C and H except for the O of carboxyl and hydroxyl.

[0064] The preparation method is: (1) HBPET powder was vacuum dried at 50°C for 24 hours, and the dried HBPET powder was mixed with PET powder in a high-speed mixer at a speed of 1300 r / min for 4 minutes. To prevent HBPET from adhering to PET powder to form agglomerates after absorbing water, the inner wall of the high-speed mixer was cleaned every 2 minutes. The HBPET was extruded by a twin-screw extruder, and the melt was cooled in a water tank and pelletized by a pelletizer to prepare a HBPET / PET composite resin masterbatch with a HBPET mass fraction of 1%.

[0065] (2) The HBPET / PET composite resin masterbatch and pure PET resin chips were dried in a vacuum oven at 150°C for 9 hours, cooled to room temperature, and pre-mixed with the pure PET resin chips in a high-speed mixer. The mass proportion of the HBPET / PET masterbatch was 30%, the mixing temperature was 40°C, the mixing time was 13 minutes, and the speed of the high-speed mixer was set to 1300 r / min. The processing parameters in the twin-screw extruder were controlled as follows: the temperatures of the screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the die temperature was 250°C, and the screw speed was 420 r / min, to obtain granular PET resin for melt-blowing.

[0066] Comparative Example 1 A PET resin for meltblowing, the raw material is pure PET resin chips. The preparation method is: The pure PET resin slices were dried in a vacuum oven at 160°C for 8 hours, and then added to a high-speed mixer after cooling to room temperature. The premixing temperature was 20°C, the mixing time was 10 minutes, and the speed of the high-speed mixer was set to 1400r / min. The premix was added to a twin-screw extruder, and the processing parameters of the PET resin in the twin-screw extruder were controlled as follows: the temperatures of the screw zones 1 to 7 were 240°C, 270°C, 270°C, 268°C, 263°C, 258°C, and 258°C, respectively, the head temperature was 258°C, the screw speed was 400r / min, and the melt was extruded and cooled in a water tank, and then pelletized with a pelletizer to prepare pure granular PET resin.

[0067] Comparative Example 2 The difference from Example 1 is that the mass proportion of HBPET in the HBPET / PET composite resin masterbatch is 50%, and the mass proportion of HBPET in the raw material after conversion is 5%.

[0068] Comparative Example 3 The difference from Example 1 is that the terminal carboxyl content of HBPET is 20%.

[0069] Comparative Example 4 The difference from Example 1 is that the branching degree of HBPET is 25%.

[0070] Performance Testing The resins obtained in Examples 1-8 and Comparative Examples 1-4 were dried and then injection molded in a vertical injection molding machine to obtain tensile specimens, wherein the melt temperature, mold temperature and cooling time were set to 245-270°C, 25°C and 20s, respectively. The following rheological tests were performed on the resins: melt index (test temperature was 285°C and pressure was 1.2kg), apparent viscosity of the melt under shearing of the slices at different temperatures (shear rate 1000s -1 ). The resin was melt-blown using the following process parameters to obtain fiber products, and the fiber diameter and fiber strength were compared. Melt-blown spinning process parameters are: screw zone 1 temperature 265°C, screw zone 2 temperature 265°C, screw zone 3 temperature 270°C, screw zone 4 temperature 275°C, filtration zone temperature 275°C, metering pump temperature 275°C, die zone 1 temperature 275°C, die zone 2 temperature 280°C, die zone 3 temperature 285°C, die zone 4 temperature 285°C, traction air temperature 330°C, traction air pressure 0.15MPa, receiving distance 14cm. The test results are shown in Table 1.

[0071] Table 1. Properties of the resins and meltblown fibers obtained in the examples and comparative examples It can be seen from the results in Table 1 that the hyperbranched HBPET with terminal carboxyl structure can effectively improve the fluidity and melt processability of PET resin. The melt index of PET composite resin after adding HBPET is improved to varying degrees, and the shear viscosity is significantly reduced. As shown in Example 3, when the mass fraction of HBPET in the raw material is 0.5%, the melt index of the melt at 285°C and 1.2kg pressure is 396.8g / 10min, which is much higher than the melt index of pure PET resin under the same addition (73.5g / 10min).

[0072] Comparing the shear apparent viscosity of each embodiment and comparative example at 270°C and 280°C, the shear viscosity decreases with increasing temperature, but the shear apparent viscosity of the PET composite resin after adding HBPET decreases significantly. Under given conditions, the apparent viscosity at 270°C can reach below 70Pa·s, while the apparent viscosity of pure PET resin at 280°C is 74.5Pa·s. It can be seen that the PET composite resin after adding HBPET can be processed at a lower temperature during melt-blowing. This shows that the introduction of hyperbranched HBPET with terminal carboxyl structure characteristics can effectively improve the fluidity of PET resin.

[0073] As the content of HBPET increases, the melt index of the PET composite resin increases first and then decreases, and the apparent viscosity shows the opposite change. When the content of HBPET 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. This is because the introduction of HBPET reduces the interaction between PET molecular chains, and the HBPET hyperbranched polyester is spherical and dispersed in the PET resin matrix, destroying the entanglement points between PET molecular chains, and the viscosity decreases rapidly under the shear action. When the addition amount of HBPET exceeds 1%, HBPET is entangled with each other, and the interaction between HBPET and PET molecules also begins to increase. Therefore, as the content of HBPET increases, the viscosity of the melt rises again. As the content of HBPET gradually increases, the melt index of the PET composite resin gradually decreases, and the shear apparent viscosity gradually increases. In Comparative Example 2, the HBPET content is excessive and cannot be granulated, indicating that the HBPET content has a great influence on the performance.

[0074] Comparing the melt-blown fibers of different PET resins, it can be seen that under the same melt-blowing conditions, the PET composite resin after adding HBPET has better melt processing performance, and the fibers obtained by melt-blowing are thinner and more uniform, and the mechanical strength of the fibers is higher. This is mainly due to the HBPET with terminal carboxyl structure characteristics. During the melt-blowing and hot air drawing process, the terminal carboxyl in HBPET has a strong interaction with the hydroxyl and carboxyl in the PET molecular chain, and the terminal carboxyl in HBPET can react with the hydroxyl in the PET molecular chain to undergo small molecule removal reaction and cross-linking. It can be seen that the PET melt always maintains a high melt strength during the melt-blowing process, and can be effectively stretched during the hot air drawing process to obtain thinner and stronger fiber products, and its fibers also have higher breaking strength.

[0075] The terminal carboxyl content of HBPET in Comparative Example 3 is 20%, which is lower than the preferred range; the branching degree of HBPET in Comparative Example 4 is 25%, which is lower than the preferred range. The performance of the fiber products is significantly reduced, indicating that better results can only be achieved within the preferred range of the present invention.

[0076] In summary, the present invention provides a PET composite resin for melt-blowing and a preparation method thereof. The hyperbranched polymer with the structural characteristics of terminal carboxyl groups is selected to not only improve the fluidity of the PET melt, but also enable the melt to maintain good melt strength during the melt-blowing process. In the post-processing process, the hyperbranched polymer contains a large number of hydroxyl groups and terminal carboxyl groups, which can form strong physical interactions with the PET matrix: van der Waals force, hydrogen bond, etc.; the hydroxyl groups and terminal carboxyl groups contained in the hyperbranched polymer can also react with the terminal hydroxyl groups and carboxyl groups of the PET molecular chain in the matrix under the action of the melt state and hot air to remove small molecular water and play a chemical cross-linking role. The above-mentioned effect can enable the melt to always maintain a high melt strength and stretchability during the melt-blowing process, which is conducive to the formation of finer and stronger fiber products.

[0077] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A PET resin for meltblowing, characterized in that: The raw materials include HBPET / PET composite resin masterbatch and pure PET resin; the HBPET is a hyperbranched polymer polyester with a terminal carboxyl structure, the number of terminal carboxyl groups accounts for 25-100% of the total number of terminal groups, and the branching degree is 30-100%; the mass proportion of HBPET in the raw materials is 0.1-3%.

2. A melt-blown special PET resin according to claim 1, characterized in that: The relative molecular weight of HBPET in the HBPET / PET composite resin masterbatch is 1100-50000 g / mol, and the terminal carboxyl content is 1000-4000 mol / t.

3. A melt-blown special PET resin according to claim 1, characterized in that: The mass proportion of HBPET in HBPET / PET composite resin masterbatch is 1-10%; the mass proportion of HBPET / PET composite resin masterbatch in raw materials is 10-30%.

4. A melt-blown special PET resin according to claim 1, 2 or 3, characterized in that: The melting point of the PET resin for meltblowing is 249-253°C, and the initial decomposition temperature is higher than 290°C.

5. A method for preparing the melt-blown PET resin according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) melt-blending HBPET and PET to prepare HBPET / PET composite resin masterbatch; (2) HBPET / PET composite resin masterbatch and pure PET resin chips are mixed, melted, mixed and granulated to obtain PET resin for meltblowing.

6. The method for preparing a melt-blown special PET resin according to claim 5, characterized in that: The HBPET in step (1) is first dried in a vacuum oven at 30-60°C for more than 24 hours.

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

8. The method for preparing a melt-blown special PET resin according to claim 5, characterized in that: Step (2) The HBPET / PET composite resin masterbatch and pure PET resin chips are first dried in a vacuum oven at 150-170°C for 7-9 hours, cooled to room temperature, and then mixed.

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

10. The method for preparing a melt-blown special PET resin according to claim 1, 8 or 9, characterized in that: The granulation in step (2) is carried out by twin-screw extrusion granulation. During the screw extrusion process, the temperature of each zone is 170-270°C, the head temperature is 250-260°C, and the screw speed is 390-420 r / min.

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