Environment-friendly hot-melt pressure-sensitive adhesive capable of degrading polylipoic acid groups and preparation method of environment-friendly hot-melt pressure-sensitive adhesive

Abstract

The invention discloses an environment-friendly hot-melt pressure-sensitive adhesive capable of degrading a polylipoic acid group and a preparation method of the environment-friendly hot-melt pressure-sensitive adhesive, and the environment-friendly hot-melt pressure-sensitive adhesive capable of degrading the polylipoic acid group is prepared from the following components in parts by weight: 80.5 to 88.5 parts of alpha-lipoic acid, 8.5 to 20 parts of vanillin and 0 to 1.4 parts of aluminum chloride hexahydrate. In the aspect of product performance, a vanillin system is added into lipoic acid, so that the stability of a polymer is improved, the side effect of closed-loop depolymerization of polylipoic acid after cooling is solved, and the comprehensive adhesive properties such as initial adhesion, stripping force and the like are very excellent; meanwhile, the polymer system has good compatibility and optical transparency, can meet the requirements of the hot melt adhesive on high transparency and attractive appearance of the adhesive in a specific application scene, and widens the application range of the adhesive. In the preparation process, the preparation conditions are low in energy consumption, the environmental pollution is small, the preparation is simple, special equipment is not needed, the used raw materials are commercially available products and are wide in source, and the large-scale industrial production potential is huge.

Description

Technical Field

[0001] The present invention relates to the technical field of hot melt adhesives, and in particular to an environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid and a preparation method thereof. Background Art

[0002] Adhesives are closely related to human life and production, and play a crucial role in the development process of modern human society. Among them, hot melt pressure-sensitive adhesives are widely used in the modern packaging and logistics fields due to their solvent-free and instant adhesion characteristics. However, the raw materials of traditional packaging adhesives mostly come from non-renewable resources such as petroleum, and their non-degradability and toxicity pose great hazards and potential risks to the environment and ecology. With the rapid development of industries such as logistics, the demand for environmentally friendly adhesives is also increasing day by day. In recent years, researchers have been constantly committed to developing degradable and non-toxic environmentally friendly adhesives, and have developed adhesives based on lignin, hyaluronic acid, chondroitin sulfate, etc. However, most of them are hydrogels, and their applications mostly focus on the medical field, and rarely involve packaging, daily use, etc.

[0003] Thioctic acid (TA) is a natural short-chain fatty acid containing carboxyl and disulfide bonds synthesized by plants, animals, and humans themselves. It has biodegradability. At a melting temperature of 70 °C, thioctic acid can be used to prepare supramolecular polymers through ring-opening polymerization reaction without adding additional solvents. However, due to the dithiol radicals at the active ends, it will cause its reverse ring-opening depolymerization, and the polythioctic acid itself has low tensile strength, which greatly limits its use. And the research progress of using it as a raw material for developing hot melt pressure-sensitive adhesives is not long. It has only started to develop in the field of pressure-sensitive adhesives in the past three or four years. The main problem is that its depolymerization has always troubled researchers. Therefore, if you want to prepare a hot melt pressure-sensitive adhesive with good performance, you must first solve the problem of its depolymerization. Currently, there are two methods. The first is to use the carboxyl group of thioctic acid to form supramolecular forces such as hydrogen bonds to stabilize the polythioctic acid network and prevent depolymerization. For example, a pressure-sensitive adhesive based on stabilized polythioctic acid can be achieved by adding malic acid. The second is to eliminate the cation radicals at the ends of the polythioctic acid chains. Some studies have used polyphenolic substances to eliminate free radicals, such as catechol. Some researchers have also used covalent cross-linking of free radicals and olefinic substances, such as pentaerythritol tetraacrylate. In addition, in the preparation process of the above-mentioned existing polythioctic acid-based degradable hot melt pressure-sensitive adhesives, they have large chemical pollution and complex synthesis, and are difficult to be industrially produced on a large scale.

[0004] In summary, a new type of environmentally friendly hot melt pressure-sensitive adhesive based on polythioctic acid that can avoid reverse ring-opening depolymerization caused by dithiol radicals at the active ends and improve comprehensive adhesion properties such as initial adhesion and peel strength has not been found yet. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, one of the objectives of the present invention is to provide an environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid and a preparation method thereof.

[0006] Another objective of the present invention is to provide a preparation method of an environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid.

[0007] One of the objectives of the present invention is achieved by the following technical solution: An environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid is prepared from the following components by weight: 80.5 - 88.5 parts of α-lipoic acid, 8.5 - 20 parts of vanillin, and 0 - 1.4 parts of aluminum chloride hexahydrate.

[0008] Further, the environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid is characterized in that it is prepared from the following components by weight: 80.5 - 85.5 parts of α-lipoic acid, 10 - 15 parts of vanillin, and 0.5 - 1 part of aluminum chloride hexahydrate.

[0009] Further, the environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid is prepared from the following components by weight: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 part of aluminum chloride hexahydrate.

[0010] Another objective of the present invention is achieved by the following technical solution: A preparation method of an environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid includes the following steps:

[0011] (1) Material preparation: Weigh α-lipoic acid, vanillin, and aluminum chloride hexahydrate according to the formula amount for standby use.

[0012] (2) Feeding: Add the α-lipoic acid, vanillin, and aluminum chloride hexahydrate in step (1) into a reaction vessel at room temperature, gradually heat up, and continuously stir to obtain a molten blend.

[0013] (3) Polymerization reaction: Control the temperature in the reaction vessel to be 115 - 125 °C, and the heat preservation reaction time to be 0.8 - 1.2 h to make the molten blend in step (2) react fully.

[0014] (4) Cooling: After the molten blend in step (3) has reacted fully, cool it to room temperature to obtain an environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid.

[0015] Further, in step (1), the formula amount is the following components by weight: 80.5 - 88.5 parts of α-lipoic acid, 8.5 - 20 parts of vanillin, and 0 - 1.4 parts of aluminum chloride hexahydrate.

[0016] Further, in step (1), the formulation amounts are components in the following parts by weight: 80.5 - 85.5 parts of α-lipoic acid, 10 - 15 parts of vanillin, and 0.5 - 1 part of aluminum chloride hexahydrate.

[0017] Further, in step (1), the formulation amounts are components in the following parts by weight: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 part of aluminum chloride hexahydrate.

[0018] Further, in step (2), the stirring condition is 250 - 350 r / s.

[0019] Further, in step (3), the temperature inside the reaction vessel is controlled at 120 °C, and the heat preservation reaction time is 1 h.

[0020] Further, in step (4), the cooling temperature refers to cooling to room temperature.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] In terms of product performance, the present invention prepares a polythioctic acid polymer system by adding a vanillin system to lipoic acid, improves the stability of the polymer, solves the side effect of ring-opening depolymerization of polythioctic acid after cooling, and has excellent comprehensive bonding properties such as initial adhesion and peel strength, and can replace the existing polythioctic acid-based hot melt pressure-sensitive adhesive and be used as a new type of adhesive; at the same time, the polymer system has good compatibility and optical transparency, can meet the requirements of high transparency and beauty of the colloid for hot melt adhesives in specific application scenarios, and improves the scope of application of the adhesive.

[0023] In terms of the preparation process, the preparation conditions of the present invention have low energy consumption, little environmental pollution, simple preparation without special equipment. Compared with other environmentally friendly pressure-sensitive adhesives involving complex reactions, it does not require solvents and complex pretreatment processes, and all raw materials used are commercially available products with wide sources, and has great potential for large-scale industrial production. Specific Embodiments

[0024] Next, in combination with specific embodiments, the present invention will be further described. It should be noted that, on the premise of no conflict, the following-described embodiments or technical features can be arbitrarily combined to form new embodiments.

[0025] In the present invention, unless otherwise specified, all parts and percentages are in weight units, and the equipment and raw materials used can be purchased from the market or are commonly used in the art. The methods in the following embodiments are conventional methods in the art unless otherwise specified.

[0026] The present invention provides an environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid, which is prepared from the following components in parts by weight: 80.5 - 88.5 parts of α-lipoic acid, 8.5 - 20 parts of vanillin, and 0 - 1.4 parts of aluminum chloride hexahydrate.

[0027] As a further embodiment, the environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid is characterized in that it is prepared from the following components in parts by weight: 80.5 - 85.5 parts of α-lipoic acid, 10 - 15 parts of vanillin, and 0.5 - 1 part of aluminum chloride hexahydrate.

[0028] As the most preferred embodiment, the environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid is prepared from the following components in parts by weight: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 part of aluminum chloride hexahydrate.

[0029] The present invention also provides a preparation method of the above-mentioned environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid, which specifically includes the following steps:

[0030] (1) Material preparation: Weigh α-lipoic acid, vanillin, and aluminum chloride hexahydrate according to the formula amount for later use;

[0031] (2) Feeding: Add the α-lipoic acid, vanillin, and aluminum chloride hexahydrate in step (1) into a reaction vessel at room temperature, gradually heat up, and continuously stir to obtain a molten blend;

[0032] (3) Polymerization reaction: Control the temperature in the reaction vessel to be 115 - 125 °C, and the heat preservation reaction time to be 0.8 - 1.2 h to make the molten blend in step (2) react fully;

[0033] (4) Cooling: After the molten blend in step (3) has reacted fully, cool it to room temperature to obtain the environmentally friendly hot melt pressure-sensitive adhesive based on degradable polythioctic acid.

[0034] As a further embodiment, in step (1), the formula amount is the following components in parts by weight: 80.5 - 88.5 parts of α-lipoic acid, 8.5 - 20 parts of vanillin, and 0 - 1.4 parts of aluminum chloride hexahydrate.

[0035] As a further embodiment, in step (1), the formula amount is the following components in parts by weight: 80.5 - 85.5 parts of α-lipoic acid, 10 - 15 parts of vanillin, and 0.5 - 1 part of aluminum chloride hexahydrate.

[0036] As a further embodiment, in step (1), the formula amount is the following components in parts by weight: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 part of aluminum chloride hexahydrate.

[0037] As a further embodiment, in step (2), the stirring condition is 250 - 300 r / s.

[0038] As a further embodiment, in step (3), the temperature inside the reaction vessel is controlled at 120 °C, and the heat preservation reaction time is 1 h.

[0039] As a further embodiment, in step (4), the cooling temperature refers to natural cooling to room temperature.

[0040] The following are specific embodiments of the present invention. Except for special limitations, the raw materials, equipment, etc. used in the following embodiments can be obtained by purchasing.

[0041] Examples 1 - 4 and Comparative Examples 1 - 9

[0042] Weigh the raw materials according to the ratios in Table 1 below, and prepare the pressure - sensitive adhesive according to the preparation method after Table 1 to obtain the pressure - sensitive adhesives of different examples. For details, see Table 1:

[0043] Table 1 Raw material ratio table of Examples 1 - 4

[0044]

[0045] The preparation method of the hot - melt pressure - sensitive adhesive of Examples 1 - 4 includes the following steps:

[0046] (1) Material preparation: Weigh α - lipoic acid, vanillin, and aluminum chloride hexahydrate according to the formula amounts in Table 1 for standby;

[0047] (2) Feeding: Add α - lipoic acid, vanillin, and aluminum chloride hexahydrate in step (1) into the reaction vessel at room temperature, gradually heat up, and continuously stir to obtain a molten blend; in step (2), the stirring condition is 250 - 350 r / s.

[0048] (3) Polymerization reaction: Control the temperature inside the reaction vessel at 120 °C, and keep the heat preservation reaction time for 1 h to make the molten blend in step (2) react fully;

[0049] (4) Cooling: After the molten blend in step (3) has reacted fully, cool it to room temperature to obtain an environmentally friendly hot - melt pressure - sensitive adhesive based on degradable polythioctic acid. In step (4), the cooling refers to cooling to room temperature.

[0050] Comparative Example 1

[0051] Compared with Example 3, the difference in the formula of Comparative Example 1 is that the amount of vanillin used is too small. The specific formula usage ratio is as follows: α - lipoic acid 85.1 parts, vanillin 8 parts, and aluminum chloride hexahydrate 0.7 parts. The rest of the preparation method is the same as that of Example 3.

[0052] Comparative Example 2

[0053] Compared with Example 3, the formulation difference of Comparative Example 2 lies in that the dosage of vanillin is too small. The specific formulation dosage ratio is as follows: 85.1 parts of α-lipoic acid, 21 parts of vanillin, and 0.7 part of aluminum chloride hexahydrate. The remaining preparation methods are the same as those of Example 3.

[0054] Comparative Example 3

[0055] Compared with Example 3, the formulation of Comparative Example 3 uses malic acid instead of vanillin and then removes aluminum chloride hexahydrate. The specific formulation is as follows: 85.1 parts of α-lipoic acid and 14.2 parts of malic acid. The remaining ratio dosages and preparation methods are the same as those of Example 3.

[0056] Comparative Example 4

[0057] Compared with Example 3, the formulation difference of Comparative Example 4 lies in that malic acid is used instead of vanillin. The specific formulation is as follows: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 part of aluminum chloride hexahydrate. The remaining ratio dosages and preparation methods are the same as those of Example 3.

[0058] Comparative Example 5

[0059] Compared with Example 3, the formulation difference of Comparative Example 5 lies in that the dosage of aluminum chloride hexahydrate is too large. The specific formulation is as follows: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 1.5 parts of aluminum chloride hexahydrate. The remaining ratio dosages and preparation methods are the same as those of Example 3.

[0060] Comparative Example 6

[0061] Compared with Example 3, the difference in the preparation method of Comparative Example 6 is that in step (2), the stirring process is cancelled. The remaining ratio dosages and preparation methods are the same as those of Example 3.

[0062] Comparative Example 7

[0063] Compared with Example 3, the difference in the preparation method of Comparative Example 7 is that in step (3), the temperature in the reaction vessel is controlled at 110 °C. The ratio dosages and preparation methods are the same as those of Example 3.

[0064] Comparative Example 8

[0065] Compared with Example 3, the difference in the preparation method of Comparative Example 8 is that in step (3), the temperature in the reaction vessel is controlled at 130 °C. The ratio dosages and preparation methods are the same as those of Example 3.

[0066] Effect Evaluation and Performance Detection

[0067] 1. The performance of the hot melt pressure-sensitive adhesives prepared in each example and comparative example was detected. The detection items and results are shown in Table 1.

[0068] The hot melt adhesives prepared in each example were coated with a coater. Using Gracian release paper (gram weight, 70 g / ㎡; release force 100 g / 25 mm) as the base paper and coated paper (gram weight 80 g / ㎡) as the face paper, self-crosslinking hot melt adhesive samples with a thickness of 17 grams per square meter were prepared. The adhesive film was stored in a standard environment and left standing for 48 hours for testing. The temperature of the testing environment was 23°C and the humidity was 50%.

[0069] 1. Initial tack test

[0070] The HMJY-034 type initial tack tester was used to characterize the initial tack performance of the prepared pressure-sensitive tape. The test was carried out according to the test standard of GB4852-2002. The test angle was 30 degrees. The prepared pressure-sensitive tape was cut into strips with a length of 100 mm × width of 25 mm. The auxiliary rolling section was 100 mm. A series of steel balls with different diameters were rolled down from the inclined plane. The initial tack of the sample was the largest steel ball number that stopped on the inclined plane. Each sample was tested 3 times, and the test result was the median value (the number of the test steel ball) of the steel ball numbers of the 3 test results.

[0071] 2. 180° peel strength performance

[0072] The universal material testing machine was used to characterize the 180° peel strength performance of the prepared pressure-sensitive tape. The test was carried out according to the test standard of GB2792-2014. The prepared pressure-sensitive tape was cut into strips with a size of 200 mm x 25 mm, pasted on a 304 stainless steel plate, and rolled back and forth 3 times with a 2 kg pressure roller. After standing for 20 minutes, the test was carried out. During the test, the tape was clamped by the upper fixture and peeled upward. The peeling speed was 300 mm / min, and the tensile mechanical strength during the measurement was measured. Each group of samples was measured three times, and the test result was the average value of the mechanical strength of the same group of tapes.

[0073] 3. Compatibility and optical transparency performance

[0074] The hot melt adhesive was observed with the naked eye at room temperature. According to the turbidity and transparency of the colloid, it was divided into good, general, poor, transparent, and opaque.

[0075] Table 2 shows the performance test data of the hot melt adhesives in each example

[0076]

[0077]

[0078] As shown in the above table, in terms of product performance, the polythioctic acid polymer system prepared by adding vanillin to thioctic acid in the present invention improves the stability of the polymer, solves the side effect of ring-opening depolymerization of polythioctic acid after cooling, and has excellent comprehensive adhesion properties such as initial adhesion and peel strength. It can replace the existing polythioctic acid-based hot melt pressure-sensitive adhesive and be used as a new type of adhesive. At the same time, the polymer system has good compatibility and optical transparency, can meet the requirements of high transparency and beauty of the colloid in specific application scenarios of hot melt adhesives, and expands the scope of application of the adhesive.

[0079] In terms of the preparation process, the preparation conditions of the present invention have low energy consumption and little environmental pollution. The preparation is simple and does not require special equipment. Compared with other environmentally friendly pressure-sensitive adhesives involving complex reactions, such as starch-based pressure-sensitive adhesives, etc., which require complex chemical treatment and modification (enzyme, acid-base treatment, etc.) of raw materials to eliminate a large number of hydroxyl groups in them before further synthesizing the pressure-sensitive adhesive to reduce the influence of external water on the starch-based pressure-sensitive adhesive, the preparation process of the present invention obviously does not require solvents and complex pretreatment processes. All raw materials used are commercially available products with wide sources, and there is great potential for large-scale industrial production.

[0080] Specifically, compared with Example 3, the amount of vanillin system added in Comparative Examples 1-2 is too large or too small. From the test results, the amount range of the vanillin system has a certain impact on the initial adhesion or / and peel performance of the hot melt adhesive, and it is necessary to balance the two performance requirements.

[0081] Compared with Example 3, Comparative Example 3 is a conventional polythioctic acid-based hot melt pressure-sensitive adhesive made of malic acid. The test results show that although the initial adhesion and 180° peel strength can meet the conventional use requirements of the adhesive, after one week under the same detection conditions, the initial adhesion of the hot melt adhesive is ball No. 8 and the peel strength is 20 N / inch. It can be seen that the existing polythioctic acid-based hot melt pressure-sensitive adhesive has the problem that the initial adhesion and peel performance continuously decline over time. However, the hot melt adhesive of the present invention has more excellent initial adhesion, does not show performance degradation over time, and has high colloid compatibility and high film optical transparency.

[0082] Compared with Example 3, in Comparative Example 4, aluminum chloride hexahydrate is further added to the vanillin system, and metal ion Al 3+ is added to form coordination bonds with carboxyl and other sites to construct aluminum coordination bonds to enhance the internal cohesion and mechanical strength of the system, thereby improving its peel performance, and the initial adhesion does not decrease significantly.

[0083] Compared with Example 3, in Comparative Example 5, the amount of aluminum chloride hexahydrate was increased. The test results showed that excessive aluminum chloride hexahydrate could further increase the cohesive force of the polymer, but its initial adhesion decreased. Although the peel strength was greatly improved and the maximum peel force could exceed 20 N / inch, the tape was damaged due to the high peel force, which was not conducive to the practical application of the colloid. It can be seen that the amount of aluminum chloride hexahydrate should not be too large.

[0084] Compared with Example 3, if the stirring in the reaction vessel in Comparative Example 6 was insufficient, it would lead to the inhomogeneity of the system and cause crystallization and hardening and loss of viscosity after cooling, indicating that sufficient stirring was required during the preparation process.

[0085] Compared with Example 3, in Comparative Examples 7-8, the temperature in the reaction vessel was not within the range defined in the present invention. Too low a temperature in the reaction vessel affected the polymerization rate of lipoic acid, while too high a temperature caused the volatilization of lipoic acid and the denaturation of substances, thus affecting the overall performance of the polymer system.

[0086] Generally speaking, the comprehensive adhesion properties such as the initial adhesion and peel force of this lipoic acid-vanillin hot melt pressure-sensitive adhesive are very excellent, and it has high compatibility and good optical transparency. It has good application prospects in daily consumption adhesions such as specific packaging, labels, and sticky notes with high requirements for the high transparency and beauty of the colloid. Its degradable performance will greatly relieve the burden on environmental pollution.

[0087] The above embodiments are only the preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention belong to the scope of protection required by the present invention.

Claims

1. A degradable polylipoic acid-based environmentally friendly hot melt pressure-sensitive adhesive, characterized in that: The invention is prepared from the following components in parts by weight: 80.5-88.5 parts of alpha-lipoic acid, 8.5-20 parts of vanillin and 0-1.4 parts of aluminum chloride hexahydrate.

2. The degradable polylipoic acid-based environmentally friendly hot melt pressure-sensitive adhesive according to claim 1, characterized in that: The invention is prepared from the following components in parts by weight: 80.5-85.5 parts of alpha-lipoic acid, 10-15 parts of vanillin and 0.5-1 part of aluminum chloride hexahydrate.

3. The degradable polylipoic acid-based environmentally friendly hot melt pressure-sensitive adhesive according to claim 1, characterized in that: The invention is prepared from the following components in parts by weight: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 parts of aluminum chloride hexahydrate.

4. A method for preparing a degradable polylipoic acid-based environmentally friendly hot melt pressure-sensitive adhesive, characterized in that: The steps include: (1) Preparation: Weigh α-lipoic acid, vanillin, and aluminum chloride hexahydrate according to the formula and set aside; (2) Adding materials: adding α-lipoic acid, vanillin and aluminum chloride hexahydrate in step (1) into a reaction container at room temperature, gradually heating the mixture while continuously stirring to obtain a molten blend; (3) Polymerization reaction: controlling the temperature in the reaction vessel to 115-125° C. and keeping the reaction temperature for 0.8-1.2 h, so that the molten blend in step (2) is fully reacted; (4) Cooling: After the molten blend in step (3) is fully reacted, it is cooled to room temperature to obtain a degradable polylipoic acid-based environmentally friendly hot melt pressure-sensitive adhesive.

5. The method for preparing the degradable polylipoic acid-based environment-friendly hot melt pressure-sensitive adhesive according to claim 4, characterized in that: In step (1), the formula comprises the following components in parts by weight: 80.5-88.5 parts of α-lipoic acid, 8.5-20 parts of vanillin, and 0-1.4 parts of aluminum chloride hexahydrate.

6. The method for preparing the degradable polylipoic acid-based environment-friendly hot melt pressure-sensitive adhesive according to claim 1, characterized in that: In step (1), the formula comprises the following components in parts by weight: 80.5-85.5 parts of α-lipoic acid, 10-15 parts of vanillin, and 0.5-1 part of aluminum chloride hexahydrate.

7. The method for preparing the degradable polylipoic acid-based environment-friendly hot melt pressure-sensitive adhesive according to claim 1, characterized in that: In step (1), the formula comprises the following components in parts by weight: 85.1 parts of α-lipoic acid, 14.2 parts of vanillin, and 0.7 parts of aluminum chloride hexahydrate.

8. The method for preparing the degradable polylipoic acid-based environment-friendly hot melt pressure-sensitive adhesive according to claim 4, characterized in that: In step (2), the stirring condition is 250-350 r / s.

9. The method for preparing the degradable polylipoic acid-based environment-friendly hot melt pressure-sensitive adhesive according to claim 4, characterized in that: In step (3), the temperature in the reaction container is controlled to be 120° C., and the insulation reaction time is 1 hour.

10. The method for preparing the degradable polylipoic acid-based environment-friendly hot melt pressure-sensitive adhesive according to claim 4, characterized in that: In step (4), the cooling temperature refers to natural cooling to room temperature.

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