阅读说明：本技术 一种包衣热塑性聚氨酯颗粒 (Coated thermoplastic polyurethane particle ) 是由 姜志国 潘小帆 姚明 张均 徐瑞芬 蒋国昌 李开军 于 2020-06-29 设计创作，主要内容包括：本申请提供一种包衣热塑性聚氨酯颗粒,其包括：芯核,所述芯核为热塑性聚氨酯固体颗粒；包衣层,所述包衣层设置在所述芯核的外表面上,且包覆所述芯核；所述包衣层为偏二氯乙烯聚合物。本申请的包衣热塑性聚氨酯颗粒带有PVDC包衣层,可以有效地保护芯核的热塑性聚氨酯颗粒,能够有效地阻隔水汽侵入,便于热塑性聚氨酯颗粒的运输和储存,避免了非常复杂的真空干燥预处理。同时,本申请的包衣热塑性聚氨酯颗粒制备过程简便,具有非常高的工业应用价值。(The present application provides a coated thermoplastic polyurethane particle comprising: a core, wherein the core is a thermoplastic polyurethane solid particle; a coating layer disposed on an outer surface of the core and coating the core; the coating layer is a vinylidene chloride polymer. The coated thermoplastic polyurethane particles have the PVDC coating layer, so that the thermoplastic polyurethane particles of the core can be effectively protected, the water vapor invasion can be effectively blocked, the transportation and the storage of the thermoplastic polyurethane particles are convenient, and the very complicated vacuum drying pretreatment is avoided. Meanwhile, the coated thermoplastic polyurethane particles are simple and convenient in preparation process and have very high industrial application value.)

1. A coated thermoplastic polyurethane particle comprising:

a core, wherein the core is a thermoplastic polyurethane solid particle;

a coating layer disposed on an outer surface of the core and coating the core; the coating layer is a vinylidene chloride polymer.

2. The coated thermoplastic polyurethane particle of claim 1, wherein the thermoplastic polyurethane solid particles have an average particle size of 0.5 to 10 mm.

3. The coated thermoplastic polyurethane particle of claim 1, wherein the thickness of the coating layer is 0.05 to 0.50 mm.

4. The coated thermoplastic polyurethane particles of claim 1, wherein the coating layer has a water vapor transmission rate of from 0 to 1.00g per square meter per 24 hours, as measured at 23 ℃.

5. The coated thermoplastic polyurethane particle of any one of claims 1 to 4, wherein the coating layer comprises from 3% to 15% of the total weight of the coated thermoplastic polyurethane particle.

6. The coated thermoplastic polyurethane particle of any one of claims 1-4, wherein the vinylidene chloride polymer is selected from one or more of a homopolymer of vinylidene chloride and a copolymer of vinylidene chloride.

7. The coated thermoplastic polyurethane particle of claim 6, wherein the vinylidene chloride polymer is selected from copolymers of vinylidene chloride, the co-monomer of which is selected from one or more of vinyl chloride, acrylonitrile and (meth) acrylates.

8. The coated thermoplastic polyurethane particle of claim 6, wherein the vinylidene chloride polymer has 85% to 100% by weight of units derived from vinylidene chloride, based on the total weight of the vinylidene chloride polymer.

Technical Field

The application relates to the technical field of high polymer materials, in particular to a Thermoplastic Polyurethane (TPU) particle coating composite structure.

Background

Thermoplastic Polyurethanes (TPU) are an emerging variety of the polyurethane family since the 21 st century. The TPU is suitable for modern plastic processing technologies (injection molding, extrusion molding, calendaring molding, blow molding, tape casting, spray molding, blade coating molding and the like) and equipment, and has the following advantages:

firstly, the TPU processing technology is simple, and the requirement on operators is low. The TPU processing process has no chemical reaction, is a process from solid melting to solidification molding, mainly depends on equipment and a mold, and has low requirements on the technical level of processing personnel.

② the TPU processing efficiency is high. Taking the TPU injection molding process as an example, compared with the time required for the Cast Polyurethane (CPU) process, as shown in table 1, the overall frame calculation shows that the TPU processing efficiency is 10 times higher than that of the CPU.

The TPU processing technology has good environmental protection performance and high yield. No solvent or liquid micromolecular chemicals are used in the TPU processing process, and the processing environment meets the environmental protection requirement.

Fourthly, the finished TPU processed product has stable quality and less leftover materials.

For the reasons above, TPU materials are increasingly popular with enterprises in the production, processing and application fields of the polyurethane industry, gradually replacing traditional Cast Polyurethane (CPU).

TABLE 1 comparison of the time required for CPU casting and TPU injection moulding

At present, the application field of polyurethane materials is more and more extensive due to the simple processing characteristic and excellent use performance of TPU, but the development speed of TPU is limited due to the moisture absorption tendency. The reason for the moisture absorption of TPU is that the molecular structure contains urethane bonds, has high polarity, and can adsorb moisture through hydrogen bonds, resulting in high moisture absorption rate. The water absorption of the TPU can reach 0.1-1.5% in the process of storage and transportation (generally 3-12 months). If the moisture absorption rate of the TPU is more than 1%, in the process of processing and forming, the water degradation of the urethane bond can be caused at the temperature of 120-220 ℃, and the water gasification foaming is caused, so that the compactness of the product is influenced, and the defects of appearance and performance are brought.

The traditional TPU processing needs vacuum drying pretreatment, the process parameters of the TPU processing are-0.095-0.100 MPa in vacuum degree, 60-110 ℃ in temperature and 3-12 hours in time. Such a process requires the addition of specialized equipment (conical vacuum dryers), reduces production efficiency, increases energy consumption, requires more labor and may result in the risk of thermal degradation of the material. The coated thermoplastic polyurethane particles of the present application are effective in solving this problem.

Disclosure of Invention

This application is through PVDC coating TPU granule, solves the high problem of current TPU granule water absorption rate. The problems that the existing TPU particles are high in requirements on transportation and storage conditions, short in storage time, required to be dehydrated in vacuum before use, high in product processing diseases and the like are solved.

The present application provides a coated thermoplastic polyurethane particle, comprising:

a core, said core being a solid particle of thermoplastic polyurethane,

a coating layer disposed on an outer surface of the core and coating the core; the coating layer is a vinylidene chloride polymer.

In one embodiment, the thermoplastic polyurethane solid particles have an average particle size of 0.5 to 10 mm.

In one embodiment, the coating layer has a thickness of … - … mm.

In one embodiment, the vinylidene chloride polymer is selected from one or more of homopolymers of vinylidene chloride and copolymers of vinylidene chloride.

In one embodiment, the vinylidene chloride polymer is selected from copolymers of vinylidene chloride, the comonomer of which is selected from one or more of vinyl chloride, acrylonitrile and (meth) acrylates.

In one embodiment, the vinylidene chloride polymer has 85% to 100% by weight units derived from vinylidene chloride, based on the total weight of the vinylidene chloride polymer.

In one embodiment, the coating has a water vapor transmission rate of from 0 to 1.00 grams per square meter per 24 hours measured at 23 ℃.

In one embodiment, the coating layer comprises 3% to 15% of the total weight of the coated thermoplastic polyurethane particles.

The coated thermoplastic polyurethane particles have the PVDC coating layer, so that the thermoplastic polyurethane particles of the core can be effectively protected, the water vapor invasion can be effectively blocked, the transportation and the storage of the thermoplastic polyurethane particles are convenient, and the very complicated vacuum drying pretreatment is avoided. Meanwhile, the coated thermoplastic polyurethane particles are simple and convenient in preparation process and have very high industrial application value.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a barrier overcoat of a thermoplastic polyurethane of the present application.

Wherein the reference numerals are as follows: 1 is TPU matrix particles and 2 is a PVDC coating layer.

Detailed Description

The technical solution of the present invention is further explained below according to specific embodiments. The scope of protection of the invention is not limited to the following examples, which are set forth for illustrative purposes only and are not intended to limit the invention in any way.

As shown in fig. 1, the present application discloses a coated thermoplastic polyurethane particle comprising:

a core 1, wherein the core 1 is a thermoplastic polyurethane solid particle,

a coating layer 2, the coating layer 2 being disposed on an outer surface of the core 1 and coating the core 1; the coating layer 2 is a vinylidene chloride polymer.

In the coated thermoplastic polyurethane particles herein, the plastic polyurethane particles (TPU particles) are solid particles, in regular or irregular shapes, including but not limited to rice grain, mung bean, cylinder, sphere, cuboid, cube, and the like. In one embodiment, the TPU particles (1) have an average particle size of from 0.5 to 10mm, as measured according to ASTM D1921-1989 Standard test method for particle size of plastics (Sieve analysis).

In the coated thermoplastic polyurethane particles, the water vapor transmission rate of the coating layer is 0-1.00 g/square meter.24 h, measured at 23 ℃. In one embodiment, the coating layer 2 is a vinylidene chloride polymer. The inventor of the application finds that some coating materials in the prior art, such as controlled release coating agents used for urea and the like, cannot meet the requirement that the water vapor transmission rate of a TPU coating is not more than 1.00 (g/square meter.24 h,23 ℃); meanwhile, urea controlled release coating agents and the like have great influence on the performance degradation of TPU, and cannot be used for TPU coating. However, the inventors of the present application have found that the thermoplastic polyurethane particles of the core can be effectively protected and the moisture intrusion can be effectively blocked by using a vinylidene chloride Polymer (PVDC) as a coating layer of the thermoplastic polyurethane particles. The PVDC coating layer can prevent water vapor from being conducted to TPU particles, and the storage and transportation moisture resistance of the TPU particles is improved; the moisture absorption rate of TPU particles is reduced, the drying procedure of the subsequent processing of TPU is simplified, energy and time are saved, and the processing efficiency of TPU is improved; the degradation and foaming diseases caused by moisture absorption of raw materials in the TPU processing process are avoided, and the quality of TPU products is improved.

In one embodiment, the vinylidene chloride polymer is selected from one or more of homopolymers of vinylidene chloride and copolymers of vinylidene chloride. Preferably, the vinylidene chloride polymer is selected from copolymers of vinylidene chloride, the co-monomer of which is selected from one or more of vinyl chloride, acrylonitrile and (meth) acrylates. Preferably, in the vinylidene chloride polymer, the units derived from vinylidene chloride constitute from 85% to 100% by weight, based on the total weight of the vinylidene chloride polymer.

In the coated thermoplastic polyurethane particles herein, the coating layer comprises from 3% to 15%, such as from 5% to 10%, etc., of the total weight of the coated thermoplastic polyurethane particle. In one embodiment, the coating layer has a thickness of 0.05 to 0.50 mm.

The method of forming the coated thermoplastic polyurethane particles of the present application may comprise the steps of:

providing a PVDC coating;

providing TPU particles;

a PVDC coating layer was formed on the TPU particles. This step may be performed using a hot fluidized bed coating process.

Wherein, the hot fluidized bed coating process can be carried out as follows:

firstly, preheating a vulcanizing bed. Preparation of bottom-jet fluidized bed coating machine: and starting the bottom-jet fluidized bed coating machine, and preheating the inlet air induction temperature of the bottom-jet fluidized bed coating machine to 60-110 ℃.

② preparing PVDC coating agent. PVDC is weighed and heated to 50-90 ℃.

③ feeding TPU particles. Weighing TPU granules, and feeding into a bottom-jet fluidized bed coating machine.

④ coating section, adjusting the air volume of induced draft fan of vulcanizing bed to 200m³And h, preheating TPU particles for 5-20 minutes at the induced air temperature of the inlet of the fluidized bed, pumping the PVDC coating agent in the step ② by using a peristaltic pump, and keeping the bottom spraying flow of the bottom spraying fluidized bed coating machine at 3-30 mL/min and the bottom spraying air pressure at 0.2 MPa.

⑤ drying and solidifying, keeping the temperature of the air inlet of the bottom jet fluidized bed coating machine at 60-110 ℃, and adjusting the air quantity of the induced draft fan to 100-200 m³H, bottom sprayingThe coated granules are dried in the fluidized bed for 3-30 minutes.

Sixthly, a cooling section, wherein the temperature of a cold area is between room temperature and 50 ℃, and the cooling time is 5 to 30 min.

After the PVDC coated TPU particles are prepared, they can be subjected to a series of tests:

(1) PVDC content calculation. PVDC weight/(TPU weight + PVDC weight).

(2) Storage accelerated experiments. The accelerated test is carried out in a constant temperature and humidity box, the test temperature is 75 ℃, the relative humidity is 75%, and the standard package is stored for 7 days.

(3) And (4) preparing a sample. An injection molding machine is used to prepare injection molding samples for testing. The temperature of the injection molding machine from the charging barrel to the nozzle is 80 ℃, 140 ℃, 180 ℃, 210 ℃ and 200 ℃ in sequence. The screw pressure was 15 MPa. The mold temperature was 15 ℃. Dwell time 30 s.

(4) Visual appearance quality was observed.

(5) And (4) testing the number average molecular weight. Samples were taken from the injection molded bars and the number average molecular weight was measured using liquid chromatography (GPC).

(6) And (6) testing hardness. The test is carried out according to GB T2411-2008 plastic and hard rubber indentation hardness (Shore hardness) standard measured by a hardness tester.

(7) Tensile strength and elongation at break. 500g injection molding machine, according to GB T1701 and 2001 hard rubber tensile strength and elongation at break determination "sample preparation test.

(8) And setting criteria. And taking the hardness, the tensile strength, the elongation at break and the change rate of the original technical index as criteria, wherein the change rates are not more than 10%. When the change rate of the three technical indexes is less than 10%, the PVDC coated TPU particles can effectively block the water vapor invasion.

The present invention is further illustrated by the following specific examples.

Comparative example 1

This comparative example 1 provides uncoated TPU particles. The average particle size of the TPU particles is 3.0 mm; surface uncoated PVDC; PVDC weight percent was 0.

Comparative example 1 was placed in a constant temperature and humidity chamber and accelerated storage was simulated. And then, drying by adopting a conical vacuum dryer for (0.098-0.1 MPa, 60-110 ℃ and 0.5-12 h).

In this comparative example, a plastic injection molding machine was used to prepare an injection molded sample for testing. The temperature of the injection molding machine from the charging barrel to the nozzle is 80 ℃, 140 ℃, 180 ℃, 210 ℃ and 200 ℃ in sequence. The screw pressure was 15 MPa. The mold temperature was 15 ℃. Dwell time 30 s.

The injection-molded samples were sampled and evaluated for visual surface appearance, number-average molecular weight, hardness, water absorption, tensile strength and elongation at break, and comprehensive evaluation was conducted.

Comparative example 2

This comparative example provides uncoated TPU particles. The average particle size of the TPU particles is 3.0 mm; surface uncoated PVDC; PVDC weight percent was 0.

Comparative example 2 was placed in a constant temperature and humidity chamber and accelerated storage was simulated.

In this comparative example 2, an injection molded sample was prepared for testing using a plastic injection molding machine. The temperature of the injection molding machine from the charging barrel to the nozzle is 80 ℃, 140 ℃, 180 ℃, 210 ℃ and 200 ℃ in sequence. The screw pressure was 15 MPa. The mold temperature was 15 ℃. Dwell time 30 s.

The injection-molded samples were sampled and evaluated for visual surface appearance, number-average molecular weight, hardness, water absorption, tensile strength and elongation at break, and comprehensive evaluation was conducted.