阅读说明：本技术 一种连续制备发泡热塑性聚氨酯弹性体珠粒的方法及装置 (Method and device for continuously preparing foamed thermoplastic polyurethane elastomer beads ) 是由 陈凯 于 2020-05-27 设计创作，主要内容包括：本发明提供了一种连续制备发泡热塑性聚氨酯弹性体珠粒的方法及装置,所述方法是从液体制备原料开始,仅通过两台挤出机和发泡熔腔能够直接生产发泡热塑性聚氨酯弹性体珠粒,相比于先制备得到热塑性聚氨酯弹性体,再进行发泡的现有技术而言,本申请的方法及装置设备简单,控制点少,生产效率高,成本大幅降低,而且一次性挤出具有以下优点：发泡过程中熔体强度高、粘度大,分子量容易控制且无二次挤出分子量降低的问题,另外第二挤出机后端连接有发泡熔腔,在发泡熔腔内熔体可快速预发泡,这大大降低了对后续水下切粒的要求,生产压力大幅降低,便于控制。(The invention provides a method and a device for continuously preparing foamed thermoplastic polyurethane elastomer beads, wherein the method starts from a liquid preparation raw material, can directly produce the foamed thermoplastic polyurethane elastomer beads only through two extruders and a foaming melting cavity, and compared with the prior art of firstly preparing the thermoplastic polyurethane elastomer and then foaming, the method and the device have the advantages of simple equipment, few control points, high production efficiency and greatly reduced cost, and the one-time extrusion has the following advantages: the melt strength is high, viscosity is big among the foaming process, and molecular weight is easy to control and do not have the problem that the secondary extruded molecular weight reduces, and the second extruder rear end is connected with the foaming and melts the chamber in addition, and the intracavity fuse that melts in the foaming can be prefoamed fast in advance, and this greatly reduced to follow-up underwater cut grain's requirement, production pressure reduces by a wide margin, the control of being convenient for.)

1. A method for continuously producing expanded thermoplastic polyurethane elastomer beads, wherein the method comprises the steps of:

A) injecting isocyanate, polyol, a micromolecular chain extender and an auxiliary agent into a charging barrel of a first extruder, mixing and reacting in the first extruder to form a polymer melt, and injecting a supercritical fluid into the tail end of the first extruder to mix the supercritical fluid and the polymer melt in the first extruder;

B) injecting the mixture of the supercritical fluid and the polymer melt in the step A) into a second extruder, and controlling the temperature of each temperature zone of the second extruder to gradually reduce the temperature so as to obtain a mixture with lower relative temperature and more uniform mixing;

C) the mixture with lower temperature and more uniform mixing in the step B) enters a foaming melting cavity through a second extruder and is pre-foamed in the foaming melting cavity to form a pre-foamed melt with uniformly mixed micro bubbles and the mixture;

D) and C), passing the uniformly mixed prefoamed melt in the step C) through an underwater pelletizing die head to obtain the foamed thermoplastic polyurethane elastomer beads.

2. The method of claim 1, wherein the method further comprises the steps of:

E) and heating, drying and curing the prepared foamed thermoplastic polyurethane elastomer beads to obtain a finished product of the foamed thermoplastic polyurethane elastomer beads.

3. The method according to claim 1 or 2, wherein in step a), the mass part ratio of the isocyanate, the polyol, the small molecule chain extender and the auxiliary agent is 25-35 parts of isocyanate, 50-65 parts of polyol, 5-10 parts of the small molecule chain extender and 0.5-5 parts of the auxiliary agent;

in the step A), the supercritical fluid is selected from one or more of supercritical carbon dioxide fluid, supercritical nitrogen fluid, supercritical n-butane fluid and supercritical cyclopentane fluid;

in the step A), the mass ratio of the supercritical fluid to the polymer melt is 35-55: 45-65.

4. A process according to any one of claims 1 to 3, wherein in step a) the first extruder is a twin-screw extruder;

in step a), the temperature parameters of the first extruder are shown in the following table:

5. the process according to any one of claims 1 to 4, wherein in step B) the second extruder is a single screw extruder;

in step B), the temperature parameters of the second extruder are shown in the following table:

temperature zone 1 2 3 4 5 6 7 8 9 10 Temperature/. degree.C 80-140 80-140 80-140 80-140 80-140 80-140 70-130 70-130 70-130 70-130

。

6. The method of any one of claims 1-5,

in the step C), the temperature in the foaming melting cavity is 100-150 ℃, and the lowest pressure is 2-8 MPa.

7. The method of any one of claims 1-6,

in the step D), in the underwater pelletizing process, keeping the temperature of water at 25-65 ℃ and the pressure of a pelletizing water system at 0.05-0.6 MPa;

in the step D), the temperature of the underwater pelletizing die head is 80-130 ℃, and the pressure is 1-4 MPa.

8. The process according to any one of claims 2 to 7, wherein in step E), the drying is for example by infrared heating, also for example by infrared heating during the delivery of the expanded thermoplastic polyurethane elastomer beads;

wherein the infrared heating temperature is 40-100 ℃.

9. A foamed thermoplastic polyurethane elastomer bead prepared according to the method of any one of claims 1 to 8; the particle size of the foaming thermoplastic polyurethane elastomer bead is 4-6mm, the closed porosity is more than 96%, the bulk density is 0.108-0.255kg/L, and the bulk density is 80-106 g/L.

10. The utility model provides a device of continuous preparation foaming thermoplastic polyurethane elastomer bead, the device includes feed unit, first extruder, second extruder, foaming fuse the chamber, cuts grain unit and conveying unit under water, wherein, feed unit and first extruder are connected, first extruder with the second extruder is connected, the second extruder melts the chamber with the foaming and is connected, the foaming fuse the chamber and passes through the pipeline and cut grain unit connection under water, it is connected with conveying unit to cut grain unit under water.

Technical Field

The invention belongs to the field of novel polyurethane elastomer foaming materials, and particularly relates to a method and a device for continuously preparing foaming thermoplastic polyurethane elastomer beads.

Background

The thermoplastic polyurethane elastomer (TPU) has the advantages of wide hardness range, excellent wear resistance, mechanical strength, water resistance, oil resistance, chemical corrosion resistance, mold resistance, aging resistance, no yellowing, recyclability and the like. The foaming material prepared by the TPU has excellent rebound resilience and can be used in a wider temperature range besides the excellent performance of the original matrix. The foamed TPU material has a series of characteristics of small density, high strength, strong energy absorption capacity, good sound and heat insulation performance, attractive appearance, practicability and the like compared with a pure thermoplastic elastomer material, and has very wide application prospects in various industrial fields (automobile industry, packaging materials, sports grounds, fitness equipment) and daily life fields (shoe materials, floor coatings, toys and homes) based on the advantages.

Chinese patent document CN104385479A discloses a method for preparing foamed TPU beads by an extrusion method, which comprises mixing TPU particles and inorganic nanoparticles, adding the mixture into an extruder, injecting supercritical fluid into the rear end of the extruder to form a completely mixed melt, and finally extruding the melt through a die head to obtain the foamed TPU beads.

Patent documents WO2010/136398A, CN102229709A, CN103642200A, CN103951965A, etc. also disclose methods for preparing expanded TPU beads by using a physical blowing agent through kettle pressing, and the yield is relatively high, but such methods have high requirements on equipment, cause material differences among batches due to batch production, and have relatively strict control requirements, and cannot better meet the requirements of downstream customers.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method and a device for continuously preparing foamed thermoplastic polyurethane elastomer beads, wherein the method and the device have the characteristics of continuous production, stable quality of a foamed material, high production efficiency, wide application range and the like.

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

a method for continuously producing expanded thermoplastic polyurethane elastomer beads, the method comprising the steps of:

A) injecting isocyanate, polyol, a micromolecular chain extender and an auxiliary agent into a charging barrel of a first extruder, mixing and reacting in the first extruder to form a polymer melt, and injecting a supercritical fluid into the tail end of the first extruder to mix the supercritical fluid and the polymer melt in the first extruder;

B) injecting the mixture of the supercritical fluid and the polymer melt in the step A) into a second extruder, and controlling the temperature of each temperature zone of the second extruder to gradually reduce the temperature so as to obtain a mixture with lower relative temperature and more uniform mixing;

C) the mixture with lower temperature and more uniform mixing in the step B) enters a foaming melting cavity through a second extruder and is pre-foamed in the foaming melting cavity to form a pre-foamed melt with uniformly mixed micro bubbles and the mixture;

D) and C), passing the uniformly mixed prefoamed melt in the step C) through an underwater pelletizing die head to obtain the foamed thermoplastic polyurethane elastomer beads.

The invention also provides a foaming thermoplastic polyurethane elastomer bead which is prepared according to the method; the particle size of the foaming thermoplastic polyurethane elastomer bead is 4-6mm, the closed porosity is more than 96%, the bulk density is 0.108-0.255kg/L, and the bulk density is 80-106 g/L.

The invention also provides a device for continuously preparing the foamed thermoplastic polyurethane elastomer beads, which comprises a feeding unit, a first extruder, a second extruder, a foaming melting cavity, an underwater granule cutting unit and a conveying unit, wherein the feeding unit is connected with the first extruder, the first extruder is connected with the second extruder, the second extruder is connected with the foaming melting cavity, the foaming melting cavity is connected with the underwater granule cutting unit through a pipeline, and the underwater granule cutting unit is connected with the conveying unit.

The invention has the beneficial effects that:

the invention provides a method and a device for continuously preparing foamed thermoplastic polyurethane elastomer beads, wherein the method starts from a liquid preparation raw material, can directly produce the foamed thermoplastic polyurethane elastomer beads only through two extruders and a foaming melting cavity, and compared with the prior art of firstly preparing the thermoplastic polyurethane elastomer and then foaming, the method and the device have the advantages of simple equipment, few control points, high production efficiency and greatly reduced cost, and the one-time extrusion has the following advantages: the melt strength is high, the viscosity is high, the molecular weight is easy to control in the foaming process, and the problem of secondary extrusion molecular weight reduction is avoided, so that based on the advantages, the material has thicker cell walls in the foaming process, uniform cells and can manually adjust the pore diameter of the cells, the effect of intermittent kettle pressure foaming can be achieved, and the processing performance of the foaming thermoplastic polyurethane elastomer beads is greatly optimized; in addition, the rear end of the second extruder is connected with a foaming melting cavity, and a melt in the foaming melting cavity can be rapidly pre-foamed, so that the requirement on subsequent underwater grain cutting is greatly reduced, the production pressure is greatly reduced, and the control is convenient; furthermore, the foamed thermoplastic polyurethane elastomer beads obtained after underwater pelletizing are cured in the conveying process, so that the production efficiency is improved, the energy consumption is saved, and the product density is very stable.

Drawings

FIG. 1 is a schematic structural view of an apparatus for continuously producing expanded thermoplastic polyurethane elastomer beads.

Wherein, 1 is the foaming melting chamber, 2 is first extruder, 201 is first extruder motor, 202 is the second feed inlet, 3 is the second extruder, 301 second extruder motor, 4 is the die head, 5 is first feed inlet, 6 is the pelleter, 7 is the hydroextractor, 8 is the third feed inlet, 9 is the discharge gate, 10 is the eager grain water pipe, 11 is the hydroextractor feed inlet, 12 is the pipeline, 13 is the pouring machine.

Detailed Description

< method for continuously producing expanded thermoplastic polyurethane elastomer beads >

As previously mentioned, the present invention provides a method for continuously producing expanded thermoplastic polyurethane elastomer beads, comprising the steps of:

A) injecting isocyanate, polyol, a micromolecular chain extender and an auxiliary agent into a charging barrel of a first extruder, mixing and reacting in the first extruder to form a polymer melt, and injecting a supercritical fluid into the tail end of the first extruder to mix the supercritical fluid and the polymer melt in the first extruder;

B) injecting the mixture of the supercritical fluid and the polymer melt in the step A) into a second extruder, and controlling the temperature of each temperature zone of the second extruder to gradually reduce the temperature so as to obtain a mixture with lower relative temperature and more uniform mixing;

C) the mixture with lower temperature and more uniform mixing in the step B) enters a foaming melting cavity through a second extruder and is pre-foamed in the foaming melting cavity to form a pre-foamed melt with uniformly mixed micro bubbles and the mixture;

D) and C), passing the uniformly mixed prefoamed melt in the step C) through an underwater pelletizing die head to obtain the foamed thermoplastic polyurethane elastomer beads.

Wherein the method further comprises the steps of:

E) and heating, drying and curing the prepared foamed thermoplastic polyurethane elastomer beads to obtain a finished product of the foamed thermoplastic polyurethane elastomer beads.

In one embodiment of the present invention, in step a), the selection of the isocyanate, the polyol and the small molecule chain extender is not particularly defined, and the thermoplastic polyurethane elastomer can be prepared.

Illustratively, the isocyanate has a structure represented by formula (I):

in formula (I), A represents a polyisocyanate core moiety selected from a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, or a substituted or unsubstituted aryl group, said substituents being inertly substituted; y is an integer of 2-10.

Preferably, y is an integer between 2 and 8; also preferably, y is an integer between 2 and 6.

Preferably, a is selected from the following groups: substituted or unsubstituted C_1～10Straight or branched alkyl, substituted or unsubstituted C_3～12Cycloalkyl, or substituted or unsubstituted C_6～16An aryl group; the substitution is an inert substitution.

Also preferably, the aryl group is a substituted or unsubstituted phenyl group, a substituted or unsubstituted naphthyl group, or a substituted or unsubstituted anthracenyl group, the substitution being inert substitution.

More preferably, the isocyanate is selected from the group consisting of Toluene Diisocyanate (TDI), diphenylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dimethylbiphenyl diisocyanate, polymethylene polyphenyl isocyanate, 1, 6-hexamethylene diisocyanate, trimethyl-1, 6-hexamethylene diisocyanate, xylylene isocyanate, tetramethylm-xylylene diisocyanate, isophorone diisocyanate, 1, 4-cyclohexane diisocyanate, hydrogenated methylene diphenyl isocyanate, hydrogenated toluene diisocyanate, cyclohexane dimethylene diisocyanate, norbornane diisocyanate, hexamethylene diisocyanate trimer, toluene diisocyanate dimer, TDI-trimethylolpropane adduct, toluene diisocyanate trimer, diphenylmethane diisocyanate trimer, toluene diisocyanate trimer, toluene diisocyanate trimer, toluene diisocyanate trimer, toluene diisocyanate, at least one isophorone diisocyanate trimer.

Illustratively, the polyalcohol is one or more selected from polyethylene glycol, polypropylene glycol and polytetrahydrofuran ether glycol.

Illustratively, the small molecule chain extender is selected from the group consisting of small molecule diols, small molecule diamines, and the like. Preferably, the small molecule diol comprises ethylene glycol, 1, 4-butanediol, 1, 6-hexanediol; the small molecular diamine comprises 3, 3-dichloro-4, 4-diphenylmethane diamine (MOCA) and 3, 5-dimethylthiotoluene-2, 4-diamine (DMTDA).

In the step A), the auxiliary agent comprises one or more of an antioxidant, an ultraviolet resistant agent, a nucleating agent, an anti-sticking agent, an antibacterial agent and the like.

Wherein, the antioxidant, the ultraviolet resistant agent, the nucleating agent, the anti-sticking agent, the anti-microbial agent and the like are conventional auxiliary agents known in the field.

In the step A), the mass part ratio of the isocyanate, the polyol, the micromolecular chain extender and the auxiliary agent is 25-35 parts of isocyanate, 50-65 parts of polyol, 5-10 parts of micromolecular chain extender and 0.5-5 parts of auxiliary agent.

Wherein the isocyanate comprises, by mass, 25 parts, 28 parts, 30 parts, 32 parts and 35 parts.

Wherein the polyol is 50 parts, 52 parts, 53 parts, 55 parts, 57 parts, 58 parts, 60 parts, 62 parts, 64 parts and 65 parts by mass.

The chain extender comprises, by mass, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts and 10 parts of a micromolecule chain extender.

Wherein the auxiliary agent comprises 0.5 part, 0.8 part, 1 part, 2 parts, 3 parts, 4 parts and 5 parts by weight.

Illustratively, the auxiliary agent comprises 0-5-2 parts of antioxidant, 0.5-1 part of lubricant and 0.5-2 parts of nucleating agent.

In the step A), the supercritical fluid is selected from one or more of a supercritical carbon dioxide fluid, a supercritical nitrogen fluid, a supercritical n-butane fluid and a supercritical cyclopentane fluid. The supercritical fluid may be commercially available. The addition of the supercritical fluid can cause the material to foam.

In step A), the mass ratio of the supercritical fluid to the polymer melt is 35-55:45-65, such as 40-50:50-60, such as 45: 55.

In the step A), the isocyanate, the polyol, the micromolecule chain extender and the auxiliary agent are injected into a charging barrel of the first extruder through a quantitative filling machine. The isocyanate, the polyol, the small molecular chain extender and the auxiliary agent are extruded into a first extruder after being injected into a cylinder of the first extruder, the mixing reaction of the material components is realized in the first extruder, a polymer melt is formed, then the supercritical fluid is injected into the tail end of the first extruder, and the supercritical fluid and the polymer melt are mixed at the tail end of the first extruder.

In the step A), the first extruder is a double-screw extruder.

In step a), the temperature parameters of the first extruder are shown in table 1 below:

TABLE 1

In the step B), the second extruder is a single-screw extruder.

In step B), the temperature parameters of the second extruder are shown in table 2 below:

TABLE 2

Temperature zone	1	2	3	4	5	6	7	8	9	10
											Temperature/. degree.C	80-140	80-140	80-140	80-140	80-140	80-140	70-130	70-130	70-130	70-130

In the step B), the mixture with lower temperature and uniform mixing can be directly foamed and produced after passing through a second extruder, so that the reduction of melt strength due to secondary extrusion is avoided, and the performance of the foamed beads is ensured.

In the step C), the temperature in the foaming melting cavity is 100-150 ℃, such as 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃ and 150 ℃, and the lowest pressure is 2-8MPa, such as 2MPa, 3MPa, 4MPa, 5MPa, 6MPa, 7MPa and 8 MPa.

In the step C), the foaming melting cavity is a cavity for foaming, the foaming melting cavity is internally provided with different pressure layers, and the inlet and outlet drift diameters of the different pressure layers are different, so that the polymer melt can pass through the different pressure layers in the melting cavity and generate rapid pressure drop so as to meet the requirement that a mixture with lower temperature and uniform mixing is foamed in the foaming melting cavity.

In the step C), pressure drop is generated in the process that the mixture with lower temperature and uniform mixing enters the foaming melting cavity, and the supercritical fluid in the mixture can generate gas along with the reduction of the pressure, so that pre-foaming in the foaming melting cavity is realized, and a pre-foaming melt formed by mixing micro-bubbles and the mixture is formed.

In step D), during the underwater pelletizing, the temperature of water is kept at 25-65 ℃, such as 25 ℃, 30 ℃, 35 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃ and 65 ℃, and the pressure of a pelletizing water system is kept at 0.05-0.6MPa, such as 0.05MPa, 0.1MPa, 0.2MPa, 0.3MPa, 0.4MPa, 0.5MPa and 0.6 MPa.

In the step D), the temperature of the underwater pelletizing die head is 80-130 ℃, and the pressure is 1-4MPa, such as 1MPa, 2MPa, 3MPa and 4 MPa.

In the step E), infrared heating is adopted for drying, for example, and infrared heating is also adopted for conveying the foamed thermoplastic polyurethane elastomer beads, so that the materials can be cured and reach a stable state in the conveying process, and the production efficiency is improved.

Wherein the infrared heating temperature is 40-100 ℃.

< expanded thermoplastic polyurethane elastomer beads >

As mentioned above, the present invention also provides a foamed thermoplastic polyurethane elastomer bead prepared by the above method.

Wherein the yield of the method is 200-500kg/h, such as 200, 250, 300, 350, 400, 450 or 500 kg/h.

Wherein the particle diameter of the foaming thermoplastic polyurethane elastomer bead is 4-6mm, the closed porosity is more than 96%, the bulk density is 0.108-0.255kg/L, and the bulk density is 80-106 g/L.

< apparatus for continuously producing expanded thermoplastic polyurethane elastomer beads >

As mentioned above, the present invention further provides an apparatus for continuously preparing foamed thermoplastic polyurethane elastomer beads, which includes a feeding unit, a first extruder, a second extruder, a foaming melting chamber, an underwater pelletizing unit and a conveying unit, wherein the feeding unit is connected to the first extruder, the first extruder is connected to the second extruder, the second extruder is connected to the foaming melting chamber, the foaming melting chamber is connected to the underwater pelletizing unit through a pipeline, and the underwater pelletizing unit is connected to the conveying unit.

The first extruder comprises a first feeding hole and a second feeding hole, the first feeding hole is formed in one end of the first extruder and used for adding isocyanate, polyol, a small molecular chain extender and an auxiliary agent, and the second feeding hole is formed in the other end of the first extruder and used for adding a supercritical fluid.

The feeding unit comprises an isocyanate feeding pipeline, a polyol feeding pipeline, a micromolecule chain extender feeding pipeline and an auxiliary agent feeding pipeline, wherein the isocyanate feeding pipeline, the polyol feeding pipeline, the micromolecule chain extender feeding pipeline and the auxiliary agent feeding pipeline are respectively connected with a first feeding hole of the first extruder.

The feeding unit further comprises a supercritical fluid feeding pipeline, and the supercritical fluid feeding pipeline is connected with the second feeding hole of the first extruder.

Wherein the first extruder is a twin-screw extruder.

Wherein the first extruder is connected with the second extruder through a pipeline.

Wherein, the second extruder is connected with the foaming melting cavity.

Wherein the second extruder is a single screw extruder.

The foaming melting cavity is a cavity for foaming, different pressure layers are arranged inside the foaming melting cavity, and the inlet and outlet drift diameters of the different pressure layers are different.

Wherein the underwater pelletizing system is an underwater pelletizing system for preparing expanded thermoplastic polyurethane elastomer beads known in the art, for example, the underwater pelletizing unit comprises a die head, a pelletizer and a dehydrator, the die head is connected with the pelletizer, the pelletizer is used for pelletizing the pre-foamed solution, and the pelletizer is connected with the dehydrator through a pelletizing water pipe.

The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.

The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.

In the description of the present invention, it should be noted that the terms "first", "second", etc. are used for descriptive purposes only and do not indicate or imply relative importance.

The particle densities in the following examples were measured by densitometer.

The expansion ratios in the following examples were measured by a volume method.

The bulk densities in the following examples were measured by the GB/T-6286 test method.

The rebound resilience in the following examples was measured by a falling ball rebound tester.

The "parts" used in the following examples are all referred to as "parts by mass" unless otherwise specified.

The temperature parameters of the first extruder used in the following examples are shown in table 1 below:

TABLE 1

The temperature parameters of the second extruder used in the following examples are shown in table 2 below:

TABLE 2

Temperature zone	1	2	3	4	5	6	7	8	9	10
											Temperature/. degree.C	80-140	80-140	80-140	80-140	80-140	80-140	70-130	70-130	70-130	70-130

The method of the following examples is carried out in the apparatus shown in fig. 1, as shown in fig. 1, the apparatus comprises a feeding unit, a first extruder 2, a second extruder 3, a foaming melting chamber 1, an underwater pelletizing unit and a conveying unit (not shown), wherein the feeding unit is connected with the first extruder 2, the first extruder 2 is connected with the second extruder 3 through a pipeline 12, the second extruder 3 is connected with the foaming melting chamber 1, the foaming melting chamber 1 is connected with a die head 4 in the underwater pelletizing unit through a pipeline, the die head 4 is connected with a pelletizer 6, a pelletizing water pipe 10 supplies water for the pelletizer 6, and pelletized beads are conveyed to a dehydrator 7 along with the pelletizing water pipe 10 to obtain beads; the packages are subsequently transported by the transport unit.

The foaming melting cavity is a cavity for foaming, different pressure layers are arranged inside the foaming melting cavity, and the inlet and outlet drift diameters of the different pressure layers are different. Therefore, the polymer melt can pass through different pressure layers in the melting cavity and generate rapid pressure drop so as to meet the requirement that the mixture with lower temperature and uniform mixing is foamed in the foaming melting cavity.

Wherein, first extruder includes first feed inlet 5 and second feed inlet 202, first feed inlet 5 sets up the one end at first extruder 2 for the joining of isocyanate, polyol, micromolecular chain extender and auxiliary agent, second feed inlet 202 sets up the other end at first extruder 2 for the joining of supercritical fluid.

The feeding unit comprises an isocyanate feeding pipeline, a polyol feeding pipeline, a micromolecule chain extender feeding pipeline and an auxiliary agent feeding pipeline, wherein the isocyanate feeding pipeline, the polyol feeding pipeline, the micromolecule chain extender feeding pipeline and the auxiliary agent feeding pipeline are respectively connected with a first feeding hole 5 of the first extruder.

Wherein the feeding unit further comprises a supercritical fluid feeding pipeline, and the supercritical fluid feeding pipeline is connected with the second feeding hole 202 of the first extruder.

Wherein the first extruder 2 is a twin-screw extruder.

Wherein the second extruder 3 is a single screw extruder.

Wherein the first extruder 2 is connected to the third feed opening 8 of the second extruder 3 via a line 12.

Wherein, granule cutting unit includes die head 4, pelleter 6 and hydroextractor 7 under water, die head 4 is connected with pelleter 6, pelleter 6 is used for realizing the granulation of prefoaming melt, pelleter 6 is connected with hydroextractor 7 through cutting grain water pipe 10.

Example 1:

adding 65 parts of polyol (polyether polyol with the molecular weight of 1000), 27 parts of isocyanate (MDI), 5 parts of small molecular alcohol (1, 4-butanediol), 1.5 parts of antioxidant (antioxidant 1010), 0.5 part of lubricant (wax powder) and 1 part of nucleating agent (talcum powder) into a first extruder, controlling the temperature of the first extruder according to the temperature in table 1, adding supercritical carbon dioxide fluid at the tail end of the first extruder at the rate of 110kg/h, controlling the total yield of finished products at 250kg/h, controlling the temperature of a second extruder according to the temperature in table 2 after materials enter the second extruder, enabling the materials to enter a foaming melting cavity, adjusting the particle density by adjusting the pressure of the melting cavity, for example, the lowest pressure of the melting cavity is 2MPa, and controlling the temperature and pressure of granulating water during underwater granulating to ensure full and regular particles, for example, the temperature of the granulating water is 35 ℃, the pressure of the granulating water is 0.3MPa, the die head pressure is 2.5MPa, the die head temperature is 80-130 ℃, the conveying equipment temperature is 55 ℃, and the passing test particle density is 0.108 kg/L.

Example 2:

adding 65 parts of polyol (polyether polyol with the molecular weight of 1000), 27 parts of isocyanate (MDI), 5 parts of small molecular alcohol (1, 4-butanediol), 1.5 parts of antioxidant (antioxidant 1010), 0.5 part of lubricant (wax powder) and 1 part of nucleating agent (silicon dioxide) into a first extruder, controlling the temperature of the extruder according to the temperature in table 1, adding supercritical carbon dioxide fluid at the tail end of the first extruder at the rate of 125kg/h, controlling the total yield of finished products at 300kg/h, gradually reducing the temperature of materials after the materials enter a second extruder, controlling the parameters in table 2, enabling the materials to enter a foaming melting cavity after passing through a die head, adjusting the particle density by adjusting the pressure of the melting cavity, for example, the lowest pressure of the melting cavity is 2.5MPa, and controlling the temperature and the pressure of granulating water during underwater granulating to ensure that the particles are full and regular, for example, the temperature of the granulating water is 35 ℃, the pressure is 0.4MPa, the die head pressure is 2MPa, the die head temperature is 80-130 ℃, the conveying equipment temperature is 60 ℃, and the passing test shows that the particle density is 0.171 kg/L.

Example 3:

adding 65 parts of polyol (polyether polyol with the molecular weight of 1000), 27 parts of isocyanate (MDI), 5 parts of small molecular alcohol (1, 4-butanediol), 1.5 parts of antioxidant (antioxidant 1010), 0.5 part of lubricant (wax powder) and 1 part of nucleating agent (silicon dioxide) into a first extruder, controlling the temperature of the extruder according to the temperature in table 1, adding supercritical carbon dioxide fluid at the tail end of the first extruder at the rate of 140kg/h, controlling the total yield of finished products at 350kg/h, gradually reducing the temperature of materials after the materials enter a second extruder, controlling the parameters in table 2, enabling the materials to enter a foaming melting cavity after passing through a die head, adjusting the pressure of the melting cavity to adjust the particle density, for example, the lowest pressure of the melting cavity is 2MPa, controlling the temperature and pressure of granulating water during underwater granulating to ensure that particles are full and regular, for example, the temperature of the granulating water is 40 ℃, the pressure is 0.3MPa, the die head pressure is 2.5MPa, the die head temperature is 80-130 ℃, the conveying equipment temperature is 40 ℃, and the passing test shows that the particle density is 0.129 kg/L.

Example 4:

adding 65 parts of polyol (polyether polyol with the molecular weight of 1000), 27 parts of isocyanate (MDI), 5 parts of small molecular alcohol (1, 4-butanediol), 1.5 parts of antioxidant (antioxidant 1010), 0.5 part of lubricant (wax powder) and 1 part of nucleating agent (silicon dioxide) into a first extruder, controlling the temperature of the extruder according to the temperature in table 1, adding supercritical carbon dioxide fluid at the tail end of the first extruder at the rate of 80kg/h, controlling the total yield of finished products at 250kg/h, gradually reducing the temperature of the materials after the materials pass through a die head and enter a second extruder, controlling the materials according to the parameters in table 2, enabling the materials to enter a foaming melting cavity, adjusting the particle density by adjusting the pressure of the melting cavity, for example, the lowest pressure of the melting cavity is 2.5MPa, and controlling the temperature and the pressure of granulating water during underwater granulating to ensure that the particles are full and regular, for example, the temperature of the granulating water is 55 ℃, the pressure is 0.5MPa, the die head pressure is 2MPa, the die head temperature is 80-130 ℃, the conveying equipment temperature is 40 ℃, and the passing test shows that the particle density is 0.165 kg/L.

Example 5:

adding 65 parts of polyol (polyether polyol with the molecular weight of 1000), 27 parts of isocyanate (MDI), 5 parts of small molecular alcohol (1, 4-butanediol), 1.5 parts of antioxidant (antioxidant 1010), 0.5 part of lubricant (wax powder) and 1 part of nucleating agent (talcum powder) into a first extruder, controlling the temperature of the extruder according to the temperature in table 1, adding supercritical carbon dioxide fluid at the tail end of the first extruder at the rate of 150kg/h, controlling the total yield of finished products at 400kg/h, gradually reducing the temperature of materials after the materials enter a second extruder, controlling the parameters in table 2, enabling the materials to enter a foaming melting cavity after passing through a die head, adjusting the particle density by adjusting the pressure of the melting cavity, for example, the lowest pressure of the melting cavity is 3MPa, controlling the temperature and the pressure of granulating water during underwater granulating to ensure that particles are full and the particle shape is regular, for example, the temperature of the granulating water is 60 ℃, the pressure is 0.5MPa, the die head pressure is 3MPa, the die head temperature is 80-130 ℃, the conveying equipment temperature is 80 ℃, and the passing test shows that the particle density is 0.255 kg/L.

Comparative example 1

Adding 65 parts of polyol (1000 molecular weight polyether), 27 parts of isocyanate (MDI), 5 parts of small molecular alcohol (1,4 butanediol), 1.5 parts of antioxidant (1010), 0.5 part of lubricant (wax powder) and 1 part of nucleating agent (talcum powder) into a first extruder, controlling the temperature of the first extruder according to the temperature in table 1, adding supercritical carbon dioxide fluid into the tail end of the first extruder at the rate of 25kg/h, controlling the total yield of finished products at 100kg/h, controlling the temperature of a second extruder according to the temperature in table 2 after materials enter the second extruder, and controlling the temperature and pressure of a granulating grain during underwater granulating so as to ensure full granules and granular shape, wherein the temperature and the pressure of the granulating grain are controlled, for example, the temperature of the granulating grain is 35 ℃, the regular pressure is 6MPa, the pressure of a die head is 10MPa, the temperature of the die head is 80-130 ℃, and the density of the granules is 0.160kg/L through testing.

TABLE 3

	Example 1	Example 2	Example 3	Example 4	Example 5	Comparative example 1
							Extrusion output	250	300	350	250	400	100
Die pressure/MPa	2.5	2	2.5	2	3	10
							Granulation pressure/MPa	0.3	0.4	0.3	0.5	0.5	6
Water temperature/DEG C of granulated pellets	35	35	40	55	60	35
							Melt chamber pressure/MPa	2	2.5	2	2.5	3	Is free of
Conveying apparatus/. degree C	55	60	40	40	80	Is free of
							Density of granules/kg/L	0.108	0.171	0.129	0.165	0.255	0.160
Particle size/mm	6	5.2	4.4	5.5	4.1	5.2
							Expansion ratio	13	8.4	11	9	5.1	7.9
Bulk density g/L	75	96	80	104	133	100
							The rebound resilience%	60	70	55	58	59	62

As can be seen from Table 1, in examples 1-5, the density of the obtained expanded TPU beads is between 0.108 and 0.255kg/L, the particle roundness is better, the surface is smooth, other properties completely meet the requirements of the invention, the uniformity of the particle cells in different examples is different, and meanwhile, in the continuous preparation process of the expanded TPU beads, all sampling test results fluctuate within 3%. Compared with the comparative example 1, the pressure of the granulating system of the comparative example 1 is higher, which is mainly caused by the resistance of screw conveying, so that the conveying efficiency is low, and if the material injection (high yield) is too fast, the material is overflowed at the material injection port and cannot be completely foamed, so that the material uniformity is poor, and therefore, the production efficiency of the examples 1 to 5 can be greatly improved.

The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.