Thermoplastic polyurethane hot melt adhesive capable of being heated by microwaves and application of thermoplastic polyurethane hot melt adhesive

Abstract

The invention belongs to the technical field of hot melt adhesives, and discloses a thermoplastic polyurethane hot melt adhesive capable of being heated by microwaves and application thereof.The thermoplastic polyurethane hot melt adhesive capable of being heated by microwaves contains thermoplastic polyurethane and a microwave absorbing material, the microwave absorbing material is carbonyl iron powder, or the microwave absorbing material is a mixture of carbon nanotubes and carbonyl iron powder, the content of carbon nanotubes in the thermoplastic polyurethane hot melt adhesive does not exceed 0.15 wt%; the application method comprises the following steps: heating the thermoplastic polyurethane hot melt adhesive capable of being heated by microwaves to 80-120 DEG C in a microwave heating manner, and melting and adhering the thermoplastic polyurethane hot melt adhesive to a to-be-adhered object. According to the invention, poor thermal degradation caused by too fast heating of the thermoplastic polyurethane capable of being heated by microwaves is relatively inhibited, so that the bonding effect is ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of hot melt adhesives and relates to a microwave-heatable thermoplastic polyurethane hot melt adhesive and application thereof. Background Art

[0002] As a high molecular polymer material that can be molded by heating, thermoplastic polyurethane hot melt adhesive is widely used in daily life and industrial fields due to its excellent performance. This hot melt adhesive does not use organic solvents and does not require water as a medium. Therefore, when used as an adhesive, there is no need to remove organic solvents or water. It can show excellent processing performance only by heating, which is very suitable for bonding operations in unmanned automated production lines.

[0003] Microwaves are a type of high-frequency electromagnetic wave that can penetrate into materials. When microwaves encounter dielectric materials (such as water, polar small-molecule organic solvents, etc.) in materials, they cause vibration and friction of the molecules in these materials, thereby generating heat. This microwave-induced heat will quickly raise the temperature of the material, achieving a heating effect.

[0004] Patent application CN108192529A discloses a new type of hot melt adhesive that can be heated by microwaves. Its raw materials include: 50-80 parts of a polymer matrix, 5-10 parts of a viscosity regulator, 5-20 parts of a tackifier, and 5-30 parts of a microwave absorbing material. The components of the polymer matrix include one or more of ethylene and its copolymers, polyurethane, polyacrylamide, polyester, polyolefin, and styrene. The microwave absorbing material includes one or more of metal oxides, graphite materials, ferroelectric materials, calcium carbonate, barium carbonate, and electrolytic stone.

[0005] Generally, the ideal bonding temperature of thermoplastic polyurethane hot melt adhesive is 80-120°C. However, the hot melt adhesive of patent application CN108192529A heats up very quickly under the action of microwaves and easily exceeds the ideal bonding temperature, resulting in failure to use the adhesive normally.

[0006] Therefore, it is necessary to develop a microwave-heatable thermoplastic polyurethane hot melt adhesive and its application that can solve the above problems. Summary of the invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and provide a microwave-heatable thermoplastic polyurethane hot melt adhesive and application thereof.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] The invention discloses a microwave-heatable thermoplastic polyurethane hot melt adhesive, which contains thermoplastic polyurethane (i.e. polyurethane which is in a molten state as the temperature rises) and a microwave absorbing material, wherein the microwave absorbing material is carbonyl iron powder.

[0010] As the preferred technical solution:

[0011] As the microwave-heatable thermoplastic polyurethane hot melt adhesive, the content of carbonyl iron powder in the thermoplastic polyurethane hot melt adhesive is 1-5wt%.

[0012] The present invention controls the content of carbonyl iron powder in the thermoplastic polyurethane hot melt adhesive to be 1-5wt%, which can ensure that the heating speed of the hot melt adhesive is fast and the physical properties of the thermoplastic polyurethane hot melt adhesive are excellent.

[0013] In the microwave-heatable thermoplastic polyurethane hot melt adhesive, the carbonyl iron powder is flaky carbonyl iron powder with a flake diameter of at least 3 μm.

[0014] Carbonyl iron powder is a product obtained by decomposing carbonyl iron at a certain temperature, and generally has two morphologies: spherical and flake. The present invention selects flake carbonyl iron powder because flake carbonyl iron powder with a flake diameter of at least 3 μm is more suitable for rapid microwave heating with controllable temperature rise. Exemplarily, the flake diameter of the flake carbonyl iron powder is 3 μm, 10 μm, 20 μm, and 25 μm.

[0015] The thermoplastic polyurethane hot melt adhesive that can be heated by microwaves as described above, the thermoplastic polyurethane is the reaction product of a polymer polyol with a molecular weight of 1000-6000, a linear diol containing 2-12 carbon atoms, and a diisocyanate, and the polymer polyol is a polyether polyol and / or a polyester polyol.

[0016] The present invention also provides another microwave-heatable thermoplastic polyurethane hot melt adhesive, which contains thermoplastic polyurethane and microwave absorbing material, wherein the microwave absorbing material is a mixture of carbon nanotubes and carbonyl iron powder, and the content of carbon nanotubes in the thermoplastic polyurethane hot melt adhesive does not exceed 0.15wt%.

[0017] The present invention selects a mixture of carbon nanotubes and carbonyl iron powder as the microwave absorbing material because: carbon nanotubes and carbonyl iron powder both have good thermal conductivity, which can solve the problems of too fast heating, too high heating temperature, and exceeding the ideal bonding temperature caused by the introduction of a single material (carbon nanotubes) during microwave heating, and can also improve the efficiency of microwave heating.

[0018] The present invention controls the carbon nanotube content in the thermoplastic polyurethane hot melt adhesive to not exceed 0.15wt%. If the carbon nanotube content is too high, the thermoplastic polyurethane hot melt adhesive will heat very quickly under the action of microwaves, easily exceeding the ideal bonding temperature, and even causing heating and fire in severe cases.

[0019] As the preferred technical solution:

[0020] As described above, the thermoplastic polyurethane hot melt adhesive that can be heated by microwaves has a carbon nanotube content of not less than 0.05 wt %.

[0021] The present invention controls the content of carbon nanotubes in the thermoplastic polyurethane hot melt adhesive to be not less than 0.05wt%. If the content of carbon nanotubes is too low, the heating effect of microwaves on the thermoplastic polyurethane hot melt adhesive is extremely weak and the efficiency is low.

[0022] In the microwave-heatable thermoplastic polyurethane hot melt adhesive as described above, the carbon nanotubes have a tube length of at least 15 μm.

[0023] The present invention controls the tube length of the carbon nanotube to be at least 15 μm, because the carbon nanotube with a tube length of at least 15 μm is more suitable for controllable rapid microwave heating. Exemplarily, the tube length of the carbon nanotube is 15 μm, 20 μm, 25 μm, 30 μm.

[0024] As the microwave-heatable thermoplastic polyurethane hot melt adhesive, the content of carbonyl iron powder in the thermoplastic polyurethane hot melt adhesive is 1-5wt%.

[0025] The present invention controls the content of carbonyl iron powder in the thermoplastic polyurethane hot melt adhesive to be 1-5wt%, which can ensure that the heating speed of the hot melt adhesive is fast and the physical properties of the thermoplastic polyurethane hot melt adhesive are excellent.

[0026] In the microwave-heatable thermoplastic polyurethane hot melt adhesive, the carbonyl iron powder is flaky carbonyl iron powder with a flake diameter of at least 3 μm.

[0027] Carbonyl iron powder is a product obtained by decomposing carbonyl iron at a certain temperature, and generally has two morphologies: spherical and flake. The present invention selects flake carbonyl iron powder because flake carbonyl iron powder with a flake diameter of at least 3 μm is more suitable for rapid microwave heating with controllable temperature rise. Exemplarily, the flake diameter of the flake carbonyl iron powder is 3 μm, 10 μm, 20 μm, and 25 μm.

[0028] The thermoplastic polyurethane hot melt adhesive that can be heated by microwaves as described above, the thermoplastic polyurethane is the reaction product of a polymer polyol with a molecular weight of 1000-6000, a linear diol containing 2-12 carbon atoms, and a diisocyanate, and the polymer polyol is a polyether polyol and / or a polyester polyol.

[0029] The present invention also provides an application of a microwave-heatable thermoplastic polyurethane hot melt adhesive as described in any one of the above items, wherein the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating and then melt-bonded to the object to be bonded.

[0030] In the prior art, when microwave heating is performed on a microwave-heatable thermoplastic polyurethane hot melt adhesive, if the time is too short, the ideal bonding temperature cannot be reached, and if the time is too long, the ideal bonding temperature will be exceeded, resulting in overheating. Overheating often destroys the molecular chain structure of the thermoplastic polyurethane, thereby causing poor bonding effect, and even burning in severe cases. The present invention relatively suppresses the microwave-heatable thermoplastic polyurethane from being heated too quickly to produce undesirable thermal degradation, so as to ensure the bonding effect.

[0031] Beneficial effects:

[0032] (1) The present invention uses a mixture of carbon nanotubes and carbonyl iron powder as the microwave absorbing material, which can improve the efficiency of microwave heating and is conducive to achieving uniform dispersion of the microwave absorbing material in the hot melt adhesive.

[0033] (2) The carbon nanotubes and carbonyl iron powder used in the present invention both have good thermal conductivity. By controlling the content of the microwave absorbing material, the obtained microwave-heatable thermoplastic polyurethane hot melt adhesive can have a good heating effect without burning due to excessive microwave heating. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0035] The test methods of the relevant performance indicators in the following embodiments and comparative examples and the specific processes of the relevant experiments are as follows:

[0036] Average tube length of carbon nanotubes: Five fields of view were randomly selected using a scanning electron microscope, five tube lengths were randomly measured in each field of view, and the average value of the 25 tube length data was calculated.

[0037] Average flake diameter of flaky carbonyl iron powder: The longest distance value in the flaky material is recorded as the flake diameter. Five fields of view are randomly selected using a scanning electron microscope, and five flake diameters are randomly measured in each field of view. The average value of the 25 flake diameter data is calculated.

[0038] Adhesion experiment: A film (length 200mm, width 50mm, thickness 0.1mm) of microwave-heatable thermoplastic polyurethane hot melt adhesive was made and placed between the surfaces to be bonded of two objects to be bonded (microfiber leather of Jiangsu Huafeng Microfiber Material Co., Ltd., product number DHKCO-120Y08, thickness 1.2mm, black color, length 400mm after cutting, width 75mm). A pressure of 2kg was applied to the upper and lower surfaces of the two objects to be bonded, and microwave heating was performed. The frequency of microwave heating was 2450MHz, and the power was 15KW. Microwave heating was performed until the film was just heated to the target temperature. At this time, microwave heating was stopped and the film was cooled naturally to obtain a bond. A bonded sample with a length of 250mm and a width of 50mm was cut out. The test was divided into two regions along the length direction, one region with a length of 200mm, which was the adhesive region, and the other region with a length of 50mm, which was the adhesive-free region. Refer to ISO The bond strength of bonded specimens is determined by the method disclosed in Section 6 of 2411-2000.

[0039] Example 1

[0040] A microwave-heatable thermoplastic polyurethane hot melt adhesive is composed of thermoplastic polyurethane (produced by Lubrizol Specialty Chemicals (Shanghai) Co., Ltd., with a brand name of ESTANE UB310 TPU), carbon nanotubes (produced by Zhongke Jinyan (Beijing) Technology Co., Ltd., with a model name of CNT107 and an average tube length of 15 μm) and flaky carbonyl iron powder (produced by Sichuan Xinjinchun Metal Materials Co., Ltd., with a model name of FMX-60 and an average sheet diameter of 3 μm); wherein the content of the carbon nanotubes is 0.05 wt%, and the content of the carbonyl iron powder is 1 wt%.

[0041] The preparation method of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: thermoplastic polyurethane, carbon nanotubes and flaky carbonyl iron powder are screw extruded in a screw extruder to obtain the microwave-heatable thermoplastic polyurethane hot melt adhesive.

[0042] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0043] In the bonding experiment, the target temperature was 120°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 44 seconds, and the bonding strength of the bonded sample was 25N.

[0044] Comparative Example 1

[0045] A method for preparing a microwave-heatable thermoplastic polyurethane hot melt adhesive is basically the same as that in Example 1, except that the flaky carbonyl iron powder is replaced with an equal mass of carbon nanotubes (the same as in Example 1).

[0046] In the bonding experiment, the target temperature was 120°C. However, after 2s of microwave heating, the film temperature only reached 48°C and had not yet melted. After 3s of microwave heating, the film temperature had reached 188°C. The microwave-heatable thermoplastic polyurethane hot melt adhesive could not be heated to the target temperature. Microwave heating was stopped after 3s, and the bonding strength of the bonded sample was 0.1N.

[0047] By comparing Comparative Example 1 with Example 1, it can be seen that the bonding strength of the microwave-heatable thermoplastic polyurethane hot melt adhesive prepared in Comparative Example 1 between the two objects to be bonded is greatly reduced when used. This is because too many carbon nanotubes are used in this comparative example, and the heating speed of the thermoplastic polyurethane hot melt adhesive is extremely fast under the action of microwaves, which easily exceeds the ideal bonding temperature, causing the thermoplastic polyurethane hot melt adhesive to age and degrade, and ultimately causing the bonding strength of the test sample to be greatly reduced.

[0048] Example 2

[0049] A method for preparing a microwave-heatable thermoplastic polyurethane hot melt adhesive is basically the same as that in Example 1, except that the carbon nanotubes are replaced by flaky carbonyl iron powder of equal mass (the same as in Example 1).

[0050] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0051] In the bonding experiment, the target temperature was 120°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 232s. The bonding strength of the bonded sample was 26N.

[0052] By comparing Example 2 with Example 1, it can be seen that the microwave-heatable thermoplastic polyurethane hot melt adhesive prepared in Example 2 has low heating efficiency and long heating time during application. This is because the microwave absorbing material used in Example 2 is carbon-based iron powder, which will weaken the microwave absorption capacity of the prepared thermoplastic polyurethane hot melt adhesive, resulting in low heating efficiency and long heating time.

[0053] Example 3

[0054] A method for preparing a microwave-heatable thermoplastic polyurethane hot melt adhesive is basically the same as Example 1, except that the average tube length of the carbon nanotubes is 10 μm, the manufacturer is Shandong Carbon Peak New Material Technology Co., Ltd., and the brand is TF-210.

[0055] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0056] In the bonding experiment, the target temperature was 120°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 52 seconds, and the bonding strength of the bonded sample was 25N.

[0057] Example 4

[0058] A method for preparing a microwave-heatable thermoplastic polyurethane hot melt adhesive is basically the same as Example 1, except that the carbon nanotubes are replaced by spherical carbonyl iron powder of equal mass (purchased from Xinxiang Sanyi Metal Materials Co., Ltd., the product name is carbonyl iron powder, and the particle size is 2000 mesh).

[0059] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0060] In the bonding experiment, the target temperature was 120°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 60s. The bonding strength of the bonded sample was 25N.

[0061] Comparative Example 2

[0062] A method for preparing a microwave-heatable thermoplastic polyurethane hot melt adhesive is basically the same as Example 4, except that the spherical carbonyl iron powder is replaced by an equal mass of spherical iron oxide (with an average diameter of 7.5 μm).

[0063] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0064] In the bonding experiment, the target temperature was 120°C. However, after 2s of microwave heating, the film temperature only reached 50°C and had not yet melted. After 3s of microwave heating, the film temperature had reached 202°C. The microwave-heatable thermoplastic polyurethane hot melt adhesive could not be heated to the target temperature. Microwave heating was stopped after 3s, and the bonding strength of the bonded sample was 3N.

[0065] By comparing Example 3 and Example 4, it can be seen that the microwave-heatable thermoplastic polyurethane hot melt adhesive prepared in Example 3 has reduced bonding strength between two objects to be bonded when used. This is because the spherical iron oxide used in Comparative Example 2 causes the thermoplastic polyurethane hot melt adhesive to heat extremely quickly under the action of microwaves, which easily exceeds the ideal bonding temperature, causing aging and degradation of the thermoplastic polyurethane hot melt adhesive, and ultimately greatly reducing the bonding strength of the test sample.

[0066] Example 5

[0067] A microwave-heatable thermoplastic polyurethane hot melt adhesive is composed of thermoplastic polyurethane (produced by Lubrizol Specialty Chemicals (Shanghai) Co., Ltd., with a brand name of ESTANE UB310 TPU), carbon nanotubes (produced by Zhongke Jinyan (Beijing) Technology Co., Ltd., with a model name of CNT105 and an average tube length of 20 μm) and flaky carbonyl iron powder (produced by Sichuan Xinjinchun Metal Materials Co., Ltd., with a model name of FMZ-60 and an average flake diameter of 5 μm); wherein the content of the carbon nanotubes is 0.08 wt%, and the content of the carbonyl iron powder is 2 wt%.

[0068] The preparation method of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: thermoplastic polyurethane, carbon nanotubes and flaky carbonyl iron powder are screw extruded in a screw extruder to obtain the microwave-heatable thermoplastic polyurethane hot melt adhesive.

[0069] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0070] In the bonding experiment, the target temperature was 110°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 30 seconds. The bonding strength of the bonded sample was 23N.

[0071] Example 6

[0072] A microwave-heatable thermoplastic polyurethane hot melt adhesive is composed of thermoplastic polyurethane (produced by Lubrizol Specialty Chemicals (Shanghai) Co., Ltd., with a brand name of ESTANE UB310 TPU), carbon nanotubes (produced by Zhongke Jinyan (Beijing) Technology Co., Ltd., with a model name of CNT105 and an average tube length of 20 μm) and flaky carbonyl iron powder (produced by Sichuan Xinjinchun Metal Materials Co., Ltd., with a model name of FMZ-60 and an average flake diameter of 5 μm); wherein the content of the carbon nanotubes is 0.1 wt%, and the content of the carbonyl iron powder is 3 wt%.

[0073] The preparation method of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: thermoplastic polyurethane, carbon nanotubes and flaky carbonyl iron powder are screw extruded in a screw extruder to obtain the microwave-heatable thermoplastic polyurethane hot melt adhesive.

[0074] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0075] In the bonding experiment, the target temperature was 100°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 17 seconds, and the bonding strength of the bonded sample was 22N.

[0076] Example 7

[0077] A microwave-heatable thermoplastic polyurethane hot melt adhesive is composed of thermoplastic polyurethane (produced by Zhejiang Huafeng Thermoplastic Polyurethane Co., Ltd., with a brand name of ESTANE UB310 TPU), carbon nanotubes (produced by Beijing Zhongke Jinyan Technology Co., Ltd., with a model name of CNT103 and an average tube length of 50 μm) and flaky carbonyl iron powder (produced by Sichuan Xinjinchun Metal Materials Co., Ltd., with a model name of FHC-5 and an average sheet diameter of 10 μm); wherein the content of the carbon nanotubes is 0.15 wt%, and the content of the carbonyl iron powder is 5 wt%.

[0078] The preparation method of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: thermoplastic polyurethane, carbon nanotubes and flaky carbonyl iron powder are screw extruded in a screw extruder to obtain the microwave-heatable thermoplastic polyurethane hot melt adhesive.

[0079] The application process of the microwave-heatable thermoplastic polyurethane hot melt adhesive is as follows: the microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.

[0080] In the bonding experiment, the target temperature was 80°C, and the time taken for the microwave-heatable thermoplastic polyurethane hot melt adhesive to just heat up to the target temperature was 10 seconds. The bonding strength of the bonded sample was 19N.

Claims

1. A microwave-heatable thermoplastic polyurethane hot melt adhesive, comprising thermoplastic polyurethane and a microwave absorbing material, characterized in that: The microwave absorbing material is carbonyl iron powder.

2. The microwave-heatable thermoplastic polyurethane hot melt adhesive according to claim 1, characterized in that: The microwave absorbing material is a mixture of carbon nanotubes and carbonyl iron powder, and the content of the carbon nanotubes in the thermoplastic polyurethane hot melt adhesive does not exceed 0.15wt%.

3. The microwave-heatable thermoplastic polyurethane hot melt adhesive according to claim 2, characterized in that: The content of carbon nanotubes in the thermoplastic polyurethane hot melt adhesive is not less than 0.05wt%.

4. The microwave-heatable thermoplastic polyurethane hot melt adhesive according to claim 2, characterized in that: The carbon nanotubes have a tube length of at least 15 μm.

5. A microwave-heatable thermoplastic polyurethane hot melt adhesive according to any one of claims 1 to 4, characterized in that: The content of carbonyl iron powder in the thermoplastic polyurethane hot melt adhesive is 1-5wt%.

6. A microwave-heatable thermoplastic polyurethane hot melt adhesive according to any one of claims 1 to 4, characterized in that: The carbonyl iron powder is a flake carbonyl iron powder, and the flake diameter is at least 3 μm.

7. The use of a microwave-heatable thermoplastic polyurethane hot melt adhesive as claimed in any one of claims 1 to 6, characterized in that: The microwave-heatable thermoplastic polyurethane hot melt adhesive is heated to 80-120° C. by microwave heating, and then melt-bonded to the object to be bonded.