Preparation method of copolyamide hot melt adhesive with low VOC emission

Abstract

The invention discloses a preparation method of a copolyamide hot melt adhesive with low VOC (volatile organic compound) emission, which comprises five steps of feeding, salt forming reaction, polymerization reaction, pressure release and negative pressure stage, and is mainly characterized in that the low-VOC copolyamide hot melt adhesive is produced and synthesized by adjusting a production process, mainly adjusting a reaction process in the salt forming stage in a polyamide hot melt adhesive synthesis process. The copolyamide hot melt adhesive is synthesized by adopting a specific salt forming process and a synthesis route, and the VOC emission of copolyamide is low and does not exceed 10g / kg.

Description

Technical Field

[0001] The invention relates to a synthesis process and a preparation method of a copolyamide hot melt adhesive, in particular to a preparation method of a copolyamide hot melt adhesive with low VOC emission. Background Art

[0002] Hot melt adhesive is solid at room temperature. It is melted by heating and adheres to the adherend. After cooling, it forms an adhesive with a certain adhesive strength. Hot melt adhesive is a solvent-free, non-toxic adhesive with 100% solid content.

[0003] Hot melt adhesives are widely used in the textile, automotive and other industries. Car interiors, seats, coat racks and other fabrics and leathers are now basically bonded and laminated with hot melt adhesives. Due to environmental factors and the improvement of quality of life, the VOC requirements in car interiors are becoming more and more stringent. The VOC in car interiors mainly comes from the materials used in the car and its various auxiliary materials. Hot melt adhesive is one of the auxiliary materials - adhesive. This patent provides a low-VOC copolyamide hot melt adhesive for the automotive industry. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for synthesizing a low-VOC copolyamide hot melt adhesive, mainly by adjusting the production process, mainly adjusting the reaction process in the salt-forming stage during the synthesis of the polyamide hot melt adhesive to produce a low-VOC copolyamide hot melt adhesive.

[0005] The object of the present invention is to provide a method for preparing a copolyamide hot melt adhesive with low VOC emissions, comprising the following steps:

[0006] (1) Feeding: According to the ingredients of PA-203, feed the raw materials into the reactor and add 20-30% of the water in the feed amount;

[0007] (2) Salt-forming reaction: heating to 150-180°C, pressure 0.45MPa-0.95MPa, reaction time 4.5-6.0h;

[0008] (3) Polymerization reaction: After the salt-forming reaction in step 2 is completed, the temperature and pressure are continuously raised by the temperature control system and the pressure regulation system, the temperature is 265-275° C., the pressure is 1.65-1.70 MPa, and the temperature and pressure corresponding to this temperature are controlled by the temperature control system and the pressure regulation system for 7.0-8.0 hours;

[0009] (4) Depressurization: After the polymerization reaction in step 3 is completed, the pressure release rate is controlled by the pressure regulating system to reduce the pressure by 0.008-0.01 MPa every 30 seconds, that is, the pressure release rate is 0.008-0.01 MPa / 30s; the time for the pressure to decrease from 1.65-1.70 MPa to normal pressure OMpa is 1.3-1.8 hours;

[0010] (5) Negative pressure stage: After the pressure release process in step 4 is completed, the vacuum system is slowly opened, and the system pressure is adjusted through the vacuum system. The system pressure is adjusted to -0.08 to -0.06 MPa in 0.4 to 0.5 h, and the negative pressure reaction is carried out for 0.50 to 1.0 h.

[0011] Furthermore, the salt-forming reaction in step (2) comprises the following steps:

[0012] (a) Raise the temperature and pressure through the temperature control system and the pressure regulation system, the temperature is 150-155°C, the pressure is 0.45-0.50MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.0-1.5h;

[0013] (b) After step (a), the temperature and pressure are continuously raised by the temperature control system and the pressure regulating system, the temperature is 165-170°C, the pressure is 0.70-0.75MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulating system for 1.5-2.0h;

[0014] (c) After step (b), the temperature and pressure are further increased by the temperature control system and the pressure regulation system, the temperature is 175-180°C, the pressure is 0.90-0.95 MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulation system for 2.0-2.5 hours.

[0015] Furthermore, step (3) is carried out in a polymerization reactor, and the volume of liquid in the polymerization reactor accounts for 60 to 90% of the volume of the polymerization reactor.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention adopts a specific salt-forming process and a synthetic route to synthesize a copolyamide hot melt adhesive. The VOC emission of the copolyamide is low, and its VOC emission does not exceed 10 g / kg.

[0018] (2) The polymerization reactor used in the present invention has efficient and controllable heat removal and mixing effects, and can efficiently control its internal flow field distribution and heat transfer rate according to the characteristics of different polymerization processes, thereby producing high-quality polymer products that meet market demand, thereby overcoming the limitations of existing polymerization reactors such as single function and unstable transfer performance.

[0019] (3) The pressure relief device of the present invention is to replace the high-pressure relief valve, the low-pressure relief valve and the negative pressure relief valve with an automatic regulating valve, the automatic valve is connected to the central control DCS system, and the pressure relief pipe row is equipped with a remote pressure gauge, which is connected to the central control DCS system. In this way, the program is automatically controlled, the number of operators and the labor intensity are reduced, the operation is accurate and efficient, and accidents caused by operator errors are eliminated. The valve opens and closes slowly and the operation is stable, so as to keep the pressure of the pressure relief pipeline stable, avoid drastic changes in the pipeline pressure to cause severe vibration, and cause pipeline rupture and safety accidents. According to the operating procedures, The DCS system has an automatic operation program, which can be prompted by the prompt light to facilitate the pressure release operation. The automatic pressure release device of the p-nitroaniline ammonolysis kettle uses an automatic control valve instead of a manual valve, and uses an automatic control program instead of manual operation to prevent operating errors. The regulating valve controls the opening and switching speed to ensure that the pressure in the pipeline rises and falls steadily, avoiding violent vibration of the pipeline and causing production accidents. The mist generated after the pressure release is blown out through the fan blades and then cooled by the coolant in the spiral tube, avoiding a large amount of mist and forming water droplets to flow out of the pressure release pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 is a flow chart of the preparation process of the present invention; DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0023] The terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover but not exclude other contents. The word "a" or "an" does not exclude the existence of a plurality. Unless otherwise specified, the meaning of "plurality" refers to more than two (including two), and similarly, "multiple groups" refers to more than two (including two).

[0024] The directional words appearing in the following description are all directions shown in the drawings, and do not limit the specific structure of the present application. For example, in the description of the present application, the directions or positional relationships indicated by the terms "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "inner", "outer", "axial", "radial", "circumferential", etc. are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present application.

[0025] In addition, the expressions of indicated directions such as the X direction, the Y direction, and the Z direction used to illustrate the operation and construction of the components of the present embodiment are not absolute but relative, and although these indications are appropriate when the components are in the positions shown in the figures, when these positions are changed, these directions should be interpreted differently to correspond to the changes.

[0026] In the description of the present application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, the "connected" or "connected" of a mechanical structure may refer to a physical connection, such as a fixed connection, a detachable connection or an integral connection. In addition to referring to a physical connection, the "connected" or "connected" of a circuit structure may also refer to an electrical connection or a signal connection. For example, it may be a direct connection, that is, a physical connection, or it may be an indirect connection through at least one intermediate element, as long as the circuit is connected. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0027] In order to facilitate the understanding of the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application are clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0028] The present invention provides a method for synthesizing a low-VOC copolyamide hot melt adhesive. Figure 1 The method is mainly to produce and synthesize low-VOC copolyamide hot melt adhesive by adjusting the production process (mainly adjusting the reaction process of the salt-forming stage in the synthesis process of polyamide hot melt adhesive). The present invention is based on the synthesis of copolyamide hot melt adhesive PA-203. It mainly includes the following steps:

[0029] (1) Feeding: According to the ingredients of PA-203, feed the raw materials into the reactor and add 20-30% of the feeding amount of water.

[0030] (2) Salt-forming reaction: the temperature is raised to 150-180°C, the pressure is 0.45MPa-0.95MPa, and the reaction time is 4.5-6.0h. The specific salt-forming process is as follows:

[0031] (a) Raise the temperature and pressure through the temperature control system and the pressure regulation system, the temperature is 150-155°C, the pressure is 0.45-0.50MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.0-1.5h;

[0032] (b) After step (a), the temperature and pressure are continuously raised by the temperature control system and the pressure regulating system, the temperature is 165-170°C, the pressure is 0.70-0.75MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulating system for 1.5-2.0h;

[0033] (c) After step (b), the temperature and pressure are further increased by the temperature control system and the pressure regulation system, the temperature is 175-180°C, the pressure is 0.90-0.95 MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulation system for 2.0-2.5 hours.

[0034] (3) Polymerization reaction: After the salt-forming reaction in step (2) is completed, the temperature and pressure are continuously raised by the temperature control system and the pressure regulating system, and the temperature is 265-275° C. and the pressure is 1.65-1.70 MPa. The temperature control system and the pressure regulating system are used to control the corresponding pressure of this temperature for 7.0-8.0 h.

[0035] (4) Depressurization: After the polymerization reaction in step (3) is completed, the pressure release rate is controlled by the pressure regulating system to reduce the pressure by 0.008-0.01 MPa every 30 seconds, that is, the pressure release rate is 0.008-0.01 MPa / 30s; the time for the pressure to decrease from 1.65-1.70 MPa to normal pressure OMpa is 1.3-1.8 hours.

[0036] (5) Negative pressure stage: After the depressurization process in step (4) is completed, the vacuum system is slowly opened, and the system pressure is adjusted through the vacuum system. The system pressure is adjusted to -0.08 to -0.06 MPa in 0.4 to 0.5 h, and the negative pressure reaction is carried out for 0.50 to 1.0 h.

[0037] The innovation of the present invention is that a specific salt-forming process and a synthetic route are used to synthesize the copolyamide hot melt adhesive. The VOC emission of the copolyamide is low, and the VOC emission does not exceed 10g / kg.

[0038] The test standards are as follows:

[0039] Melt index test standard: GB / T 3682-2000

[0040] Melting point test standard: GB / T 19466.3-2004

[0041] VOC test standard: GB / T 33372-2020

[0042] The technical indicators of conventional PA-203 are shown in Table 1:

[0043] Melting point 125-130℃ Melt Index 30-35g / 10min VOC 100-150g / kg

[0044] Table-1

[0045] Example 1

[0046] A total of 5000 kg of PA-203 raw materials were put into a reactor, and 1000 kg (20%) of water was added; after salt formation reaction, polymerization reaction, pressure release, and negative pressure stages, the corresponding PA-203 copolyamide hot melt adhesive was obtained. The specific reaction process is as follows:

[0047] (1) Salt-forming reaction:

[0048] The temperature and pressure are increased by the temperature control system and the pressure regulation system, the temperature is 150°C, the pressure is 0.45MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.5h;

[0049] The temperature and pressure continue to rise through the temperature control system and the pressure regulation system, the temperature is 166°C, the pressure is 0.70MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.5h;

[0050] The temperature and pressure are continued to be increased through the temperature control system and the pressure regulation system, the temperature is 175°C, the pressure is 0.90MPa, and the pressure corresponding to this temperature is controlled for 2.5h through the temperature control system and the pressure regulation system.

[0051] (2) Polymerization reaction: The temperature and pressure are continuously raised through the temperature control system and the pressure regulation system, the temperature is 270°C, the pressure is 1.65 MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 8.0 h

[0052] (3) Depressurization: The pressure regulating system is used to control the pressure release rate to drop by 0.01 MPa every 30 seconds, that is, the pressure release rate is 0.01 MPa / 30s; the time for the pressure to drop from 1.65 MPa to normal pressure OMPa is 1.7 hours.

[0053] (4) Negative pressure stage: After the depressurization process is completed, slowly open the vacuum system, adjust the system pressure through the vacuum system, adjust the system pressure to -0.06MPa in 0.4h, and carry out negative pressure reaction for 0.60h.

[0054] The technical indicators of PA-203 hot melt adhesive obtained through the above reaction process are shown in Table 2:

[0055] Melting point 127℃ Melt Index 30g / 10min VOC 8g / kg

[0056] Table 2

[0057] Example 2

[0058] A total of 5000 kg of PA-203 raw materials were put into a reactor, and 1250 kg (25%) of water was added; after salt formation reaction, polymerization reaction, pressure release, and negative pressure stages, the corresponding PA-203 copolyamide hot melt adhesive was obtained. The specific reaction process is as follows:

[0059] (1) Salt-forming reaction:

[0060] The temperature and pressure are raised by the temperature control system and the pressure regulating system, the temperature is 155°C, the pressure is 0.50MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulating system for 1.5h;

[0061] The temperature and pressure continue to rise through the temperature control system and the pressure regulation system, the temperature is 165℃, the pressure is 0.70MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 2.0h;

[0062] The temperature and pressure were continued to rise through the temperature control system and the pressure regulation system, the temperature was 177°C and the pressure was 0.92MPa, and the pressure corresponding to this temperature was controlled for 2.2h through the temperature control system and the pressure regulation system.

[0063] (2) Polymerization reaction: The temperature and pressure are continuously raised through the temperature control system and the pressure regulation system, the temperature is 273°C, the pressure is 1.65 MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 7.0 h

[0064] (3) Depressurization: The pressure regulating system is used to control the pressure release rate to drop by 0.008 MPa every 30 seconds, that is, the pressure release rate is 0.008 MPa / 30s; the time for the pressure to drop from 1.65 MPa to normal pressure OMPa is 1.7 hours.

[0065] (4) Negative pressure stage: After the depressurization process is completed, slowly open the vacuum system, adjust the system pressure through the vacuum system, adjust the system pressure to -0.07MPa in 0.5h, and carry out negative pressure reaction for 0.50h.

[0066] The technical indicators of PA-203 hot melt adhesive obtained through the above reaction process are shown in Table 3:

[0067] Melting point 125℃ Melt Index 32g / 10min VOC 6g / kg

[0068] Table 3

[0069] Example 3

[0070] A total of 5000 kg of PA-203 raw materials were put into a reactor, and 1500 kg (30%) of water was added. After salt formation reaction, polymerization reaction, pressure release, and negative pressure stages, the corresponding PA-203 copolyamide hot melt adhesive was obtained. The specific reaction process is as follows:

[0071] (1) Salt-forming reaction:

[0072] The temperature and pressure are raised by the temperature control system and the pressure regulating system, the temperature is 155°C, the pressure is 0.50MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulating system for 1.0h;

[0073] The temperature and pressure continue to rise through the temperature control system and the pressure regulation system, the temperature is 170℃, the pressure is 0.75MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.7h;

[0074] The temperature and pressure are continued to be increased through the temperature control system and the pressure regulation system, the temperature is 180°C and the pressure is 0.95MPa, and the pressure corresponding to this temperature is controlled for 2.3h through the temperature control system and the pressure regulation system.

[0075] (2) Polymerization reaction: The temperature and pressure are continued to be raised through the temperature control system and the pressure regulation system, the temperature is 275°C, the pressure is 1.70 MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulation system for 7.5 hours.

[0076] (3) Depressurization: The pressure regulating system is used to control the depressurization rate to be 0.01 MPa per 30 seconds, i.e., the depressurization rate is 0.01 MPa / 30s. The time for the pressure to decrease from 1.70 MPa to normal pressure OMPa is 1.4 hours.

[0077] (4) Negative pressure stage: After the depressurization process is completed, slowly open the vacuum system, adjust the system pressure through the vacuum system, adjust the system pressure to -0.08MPa in 0.4h, and carry out negative pressure reaction for 0.80h.

[0078] The technical indicators of PA-203 hot melt adhesive obtained through the above reaction process are shown in Table 4:

[0079] Melting point 126℃ Melt Index 34g / 10min VOC 5g / kg

[0080] Table 4

[0081] Example 4

[0082] A total of 5000 kg of PA-203 raw materials were put into a reactor, and 1300 kg (26%) of water was added; after salt formation reaction, polymerization reaction, pressure release, and negative pressure stages, the corresponding PA-203 copolyamide hot melt adhesive was obtained. The specific reaction process is as follows:

[0083] (1) Salt-forming reaction:

[0084] The temperature and pressure are raised by the temperature control system and the pressure regulating system, the temperature is 155°C, the pressure is 0.45MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulating system for 1.0h;

[0085] The temperature and pressure continue to rise through the temperature control system and the pressure regulation system, the temperature is 170℃, the pressure is 0.70MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.5h;

[0086] The temperature and pressure are continued to be increased through the temperature control system and the pressure regulation system, the temperature is 180°C and the pressure is 0.90MPa, and the pressure corresponding to this temperature is controlled for 2.0h through the temperature control system and the pressure regulation system.

[0087] (2) Polymerization reaction: The temperature and pressure are continuously raised through the temperature control system and the pressure regulation system, the temperature is 265°C, the pressure is 1.65 MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 7.0 h

[0088] (3) Depressurization: The pressure regulating system is used to control the pressure release rate to drop by 0.01 MPa every 30 seconds, that is, the pressure release rate is 0.01 MPa / 30s; the time for the pressure to drop from 1.65 MPa to normal pressure OMPa is 1.3 hours.

[0089] (4) Negative pressure stage: After the depressurization process is completed, slowly open the vacuum system, adjust the system pressure through the vacuum system, adjust the system pressure to -0.08MPa in 0.5h, and carry out negative pressure reaction for 1.0h.

[0090] The technical indicators of PA-203 hot melt adhesive obtained through the above reaction process are shown in Table 5:

[0091]

[0092]

[0093] Table 5

[0094] Comparative Example 1

[0095] A total of 5000 kg of PA-203 raw materials were put into a reactor, and 1000 kg (20%) of water was added; after salt formation reaction, polymerization reaction, pressure release, and negative pressure stages, the corresponding PA-203 copolyamide hot melt adhesive was obtained. The specific reaction process is as follows:

[0096] (1) Salt-forming reaction:

[0097] The temperature and pressure are increased by the temperature control system and the pressure regulation system, the temperature is 145°C, the pressure is 0.45MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.0h;

[0098] The temperature and pressure continue to rise through the temperature control system and the pressure regulation system, the temperature is 170℃, the pressure is 0.70MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 2.0h;

[0099] The temperature and pressure are continued to be increased through the temperature control system and the pressure regulation system, the temperature is 180°C, the pressure is 0.95MPa, and the pressure corresponding to this temperature is controlled for 2.5h through the temperature control system and the pressure regulation system.

[0100] (2) Polymerization reaction: The temperature and pressure are continuously raised through the temperature control system and the pressure regulation system, the temperature is 275°C, the pressure is 1.70 MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 8.0 h

[0101] (3) Depressurization: The pressure regulating system is used to control the depressurization rate to be 0.008 MPa per 30 seconds, i.e., the depressurization rate is 0.008 MPa / 30s. The time for the pressure to decrease from 1.70 MPa to normal pressure OMPa is 1.8 hours.

[0102] (4) Negative pressure stage: After the depressurization process is completed, slowly open the vacuum system, adjust the system pressure through the vacuum system, adjust the system pressure to -0.08MPa in 0.5h, and carry out negative pressure reaction for 1.0h.

[0103] The technical indicators of PA-203 hot melt adhesive obtained through the above reaction process are shown in Table 6:

[0104] Comparative Example 1 PA-203 Technology

[0105] Melting point 128℃ Melt Index 31g / 10min VOC 120g / kg

[0106] Table 6

[0107] Comparative Example 2

[0108] A total of 5000 kg of PA-203 raw materials were put into a reactor, and 1500 kg (30%) of water was added; after salt formation reaction, polymerization reaction, pressure release, and negative pressure stages, the corresponding PA-203 copolyamide hot melt adhesive was obtained. The specific reaction process is as follows:

[0109] (1) Salt-forming reaction:

[0110] The temperature and pressure are raised by the temperature control system and the pressure regulating system, the temperature is 155°C, the pressure is 0.45MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulating system for 1.5h;

[0111] The temperature and pressure continue to rise through the temperature control system and the pressure regulation system, the temperature is 170℃, the pressure is 0.60MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 2.0h;

[0112] The temperature and pressure are continued to be increased through the temperature control system and the pressure regulation system, the temperature is 180°C and the pressure is 0.95MPa, and the pressure corresponding to this temperature is controlled for 2.5h through the temperature control system and the pressure regulation system.

[0113] (2) Polymerization reaction: The temperature and pressure are continuously raised through the temperature control system and the pressure regulation system, the temperature is 275°C, the pressure is 1.70 MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 8.0 h

[0114] (3) Depressurization: The pressure regulating system is used to control the depressurization rate to be 0.008 MPa per 30 seconds, i.e., the depressurization rate is 0.008 MPa / 30s. The time for the pressure to decrease from 1.65 MPa to normal pressure OMPa is 1.8 hours.

[0115] (4) Negative pressure stage: After the depressurization process is completed, slowly open the vacuum system, adjust the system pressure through the vacuum system, adjust the system pressure to -0.08MPa in 0.5h, and carry out negative pressure reaction for 1.0h.

[0116] The technical indicators of PA-203 hot melt adhesive obtained through the above reaction process are shown in Table 7:

[0117]

[0118]

[0119] Table 7

[0120] Those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0121] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a copolyamide hot melt adhesive with low VOC emission, characterized in that: The following steps are involved: (1) Feeding: According to the ingredients of PA-203, feed the raw materials into the reactor and add 20-30% of the water in the feed amount; (2) Salt-forming reaction: heating to 150-180°C, pressure 0.45MPa-0.95MPa, reaction time 4.5-6.0h; (3) Polymerization reaction: After the salt-forming reaction in step 2 is completed, the temperature and pressure are continuously raised by the temperature control system and the pressure regulation system, the temperature is 265-275° C., the pressure is 1.65-1.70 MPa, and the temperature and pressure corresponding to this temperature are controlled by the temperature control system and the pressure regulation system for 7.0-8.0 hours; (4) Depressurization: After the polymerization reaction in step 3 is completed, the pressure release rate is controlled by the pressure regulating system to reduce the pressure by 0.008-0.01 MPa every 30 seconds, that is, the pressure release rate is 0.008-0.01 MPa / 30s; the time for the pressure to decrease from 1.65-1.70 MPa to normal pressure OMpa is 1.3-1.8 hours; (5) Negative pressure stage: After the pressure release process in step 4 is completed, the vacuum system is slowly opened, and the system pressure is adjusted through the vacuum system. The system pressure is adjusted to -0.08 to -0.06 MPa in 0.4 to 0.5 h, and the negative pressure reaction is carried out for 0.50 to 1.0 h.

2. The method for preparing a copolyamide hot melt adhesive with low VOC emission according to claim 1, characterized in that: The salt-forming reaction in step (2) comprises the following steps: (a) Raise the temperature and pressure through the temperature control system and the pressure regulation system, the temperature is 150-155°C, the pressure is 0.45-0.50MPa, and the corresponding pressure of this temperature is controlled by the temperature control system and the pressure regulation system for 1.0-1.5h; (b) After step (a), the temperature and pressure are continuously raised by the temperature control system and the pressure regulating system, the temperature is 165-170°C, the pressure is 0.70-0.75MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulating system for 1.5-2.0h; (c) After step (b), the temperature and pressure are further increased by the temperature control system and the pressure regulation system, the temperature is 175-180°C, the pressure is 0.90-0.95 MPa, and the pressure corresponding to this temperature is controlled by the temperature control system and the pressure regulation system for 2.0-2.5 hours.

3. The method for preparing a copolyamide hot melt adhesive with low VOC emission according to claim 1, characterized in that: The step (3) is carried out in a polymerization reactor, and the volume of liquid in the polymerization reactor accounts for 60 to 90% of the volume of the polymerization reactor.

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