High-transparency, ultraviolet-resistant and damp-heat aging-resistant copolyamide hot melt adhesive and preparation method thereof

Abstract

The invention discloses a high-transparency, ultraviolet-resistant and damp-heat aging-resistant copolyamide hot melt adhesive and a preparation method thereof. The high-transparency, ultraviolet-resistant and damp-heat aging-resistant copolyamide hot melt adhesive is prepared from the following raw materials: lactam, aliphatic dibasic acid, aliphatic diamine, alicyclic diamine, a molecular weight regulator and an antioxidant. The molar ratio of the lactam to the aliphatic dibasic acid to the sum of the aliphatic diamine and the alicyclic diamine is (1-2.5): 1: (0.95-1); the molar ratio of the aliphatic diamine to the alicyclic diamine is (1-4): 1. The copolyamide hot melt adhesive prepared by the preparation method disclosed by the invention has relatively good light transmittance and excellent damp-heat aging resistance and ultraviolet aging resistance on the premise of ensuring a bonding effect, and is moderate in softening point and melt index so as to facilitate sizing operation.

Description

Technical Field

[0001] The present invention relates to a copolyamide hot melt adhesive and a preparation method thereof, in particular to a highly transparent, ultraviolet-resistant, and moisture and heat aging-resistant copolyamide hot melt adhesive and a preparation method thereof. Background Art

[0002] With the popularization of the application of copolyamide hot melt adhesives in the fields of clothing, automobiles, electronic appliances, machinery, optics, etc., the demand for high transparency, ultraviolet resistance, and moisture and heat aging resistance of hot melt adhesives is increasing, while there are few reports on copolyamide hot melt adhesives that simultaneously meet the above functions in China.

[0003] Traditional copolyamide hot melt adhesives, due to the presence of flexible aliphatic chains and strong hydrogen bond interactions, the molecular chain arrangement tends to be regular, and they are a type of polymer that is easily crystallized, with poor transparency; moreover, the straight-chain structure of pure aliphatics is prone to aging under light conditions, and in addition, due to the amide bond being prone to absorbing water, the moisture and heat aging resistance of traditional linear aliphatic polyamides is not very excellent.

[0004] Summarizing recent reports on transparent polyamides: To prepare a polyamide hot melt adhesive with high transparency, it is necessary to control its crystallization performance, and its preparation methods can be divided into physical methods and chemical methods.

[0005] The physical method is to achieve transparency by hindering crystallization without changing the molecular structure. For example, a nucleating agent is added to the polymer to reduce the crystal size to less than the wavelength of visible light, or by a rapid cooling method (such as quenching) to prevent the molecular chains from crystallizing in time, and finally an amorphous polyamide is obtained. However, the transparent polyamide obtained by this method will lose its transparency when used at a higher temperature, so it is greatly limited in application.

[0006] The chemical method is to reduce the crystallization ability of polyamide through molecular structure design, making it amorphous or with a crystal size smaller than the wavelength of visible light (400 - 700 nm). Macroscopically, the polyamide will present a stable transparent state. The key to the molecular structure design of amorphous or microcrystalline polyamide materials is to hinder the crystallization of chain segments and reduce the crystal size. For example, Patent CN110540641A uses lactam, dibasic acid, and diamine composed of linear aliphatic diamine and branched aliphatic diamine as raw materials to prepare an aliphatic amorphous polyamide hot melt adhesive with good dimensional stability and transparency. However, the cohesive strength and mechanical properties of the product are reduced, and the overall linear structure determines the poor UV resistance, especially the poor aging resistance of the product. Another example is Patent CN112679729A, which introduces an aromatic structure with benzene rings on the basis of a linear aliphatic structure. Compared with the previous patent, the rigidity and stability of the benzene rings improve the strength and anti-aging properties of the product. However, the α-H in the conjugated structure of the benzene rings is very easy to absorb the energy in ultraviolet light, resulting in aging or yellowing, etc. Another Patent CN113015759A discloses an improved method for producing transparent polyamide. Although its main purpose is to improve the transparency stability of polyamide materials at high temperatures, its product is a material-grade resin rather than a hot melt adhesive, and its product is limited by the content / density of its own amide bonds. At higher temperature and humidity, its strength or mechanical properties will still drop significantly. Compared with material-grade polyamide resin, polyamide hot melt adhesive mainly plays an adhesive role and belongs to oligomers with a relatively small degree of polymerization in polymers. There are obvious differences between the two in system design, preparation, use, and application, etc.

[0007] In summary, how to prepare a copolyamide hot melt adhesive with high transparency, UV resistance, and resistance to wet heat aging has become an urgent problem to be solved. Summary of the Invention

[0008] The purpose of the present invention is to solve the above technical problems. Starting from the perspective of polymer synthesis and design, through chemical methods, a copolyamide hot melt adhesive with high transparency, UV resistance, and resistance to wet heat aging is prepared, which is expected to promote the application and development of copolyamide hot melt adhesives in fields such as wire and cable bonding and battery encapsulation films.

[0009] The technical solution adopted by the present invention is as follows: A preparation method of a copolyamide hot melt adhesive with high transparency, UV resistance, and resistance to wet heat aging, the steps are as follows: (1) Add lactam, aliphatic dibasic acid, aliphatic diamine, alicyclic diamine, molecular weight regulator, antioxidant, and water into a reaction kettle according to a preset ratio; (2) Replace with nitrogen for 1 - 3 times, then slowly heat up to 130°C, start stirring, and continue to heat up to 190°C. During this period, keep the pressure rising continuously. React for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255°C - 265°C; (3) Release to atmospheric pressure and stir - react for 1 h under the conditions of a temperature of 255°C - 265°C; (4) Evacuate to vacuum. Under the conditions of a vacuum degree < 200 Pa and a temperature of 250°C - 260°C, conduct polycondensation reaction again for 0.5 h - 1 h; (5) Break the vacuum and discharge the product under nitrogen protection to obtain the product.

[0010] In the above step (1), the molar ratio of lactam: aliphatic dicarboxylic acid: the sum of aliphatic diamine and alicyclic diamine is 1 - 2.5:1:0.95 - 1, and the molar ratio of aliphatic diamine: alicyclic diamine is 1 - 4:1; in the system of the present invention, if the addition amount of alicyclic diamine is too much or too little, it will have obvious adverse effects on the aging resistance performance and bonding strength of the product, etc., and will also affect the processing and transportation performance of the hot - melt adhesive.

[0011] The above lactam is caprolactam, laurolactam, or a mixture of both; The above aliphatic dicarboxylic acid is a long - carbon - chain aliphatic dicarboxylic acid, the carbon chain length in its molecular chain ≥ 10, and it is composed of sebacic acid, dodecanedioic acid, and tridecanedioic acid blended together; The above aliphatic diamine is a long - carbon - chain aliphatic diamine, the carbon chain length in its molecular chain ≥ 10, and it is composed of decanediamine and dodecanediamine blended together; The above alicyclic diamine includes two rings connected by an alkylene group containing 1 - 6 carbon atoms, and each ring is substituted by an amine group and an alkyl group that may be the same or different and may contain 1 - 6 carbon atoms. Specifically, it can be selected from 1,3 - cyclohexanedimethanamine (HXDA), 4,4’ - diaminodicyclohexylmethane (PACM), bis(3 - methyl - 4 - aminocyclohexyl)methane (DMDC); The above molecular weight regulator is stearic acid; its addition amount is 0.3% - 0.5% of the total mass of lactam, dicarboxylic acid, and diamine raw materials; The above antioxidant grade is selected from one of 1010, 168, 1098, or S - 682, and its addition amount is 0.2% - 0.5% of the total mass of lactam, dicarboxylic acid, and diamine raw materials.

[0012] The present invention also provides a copolymer polyamide hot - melt adhesive with high transparency, ultraviolet resistance, and resistance to damp - heat aging, which is prepared by the above - mentioned preparation method.

[0013] The innovation of the present invention lies in: starting from the polymer composition and structure, alicyclic diamines, aliphatic diamines with long carbon chains, dibasic acids, lactams, etc. are randomly copolymerized into the polyamide hot-melt adhesive system by means of multiple melt polycondensation; the introduction of the alicyclic system and the way of multiple random copolymerization jointly hinder crystallization or reduce the microcrystal size, which is beneficial to the transparency of the product; in addition, the introduction of this rigid alicyclic group ensures the cohesive strength of the hot-melt adhesive matrix, that is, the bonding performance; the use of a mixture of multiple long carbon chain dibasic acids and diamines reduces the density of amide bonds, reduces the hydrogen bonds between molecules, and the overall performance shifts towards the non-polar carbon chain direction, resulting in a decrease in water absorption rate and crystallinity, and improving the resistance to wet heat aging of the material.

[0014] The copolymerized polyamide hot-melt adhesive prepared by the present invention has good light transmittance and excellent resistance to wet heat aging on the premise of ensuring the bonding effect, especially excellent resistance to ultraviolet aging, and the softening point and melt index are moderate, which is convenient for sizing operation, and is very suitable for fields such as hot-melt interlining, wire and cable, and photovoltaic electronic packaging. Specific embodiments Example 1

[0016] A preparation method of a copolymerized polyamide hot-melt adhesive with high transparency, ultraviolet resistance, and resistance to wet heat aging is as follows: (1) Add 226.3 g of caprolactam, 121.4 g of sebacic acid, 138.2 g of dodecanedioic acid, 195.5 g of tridecanedioic acid, 68.9 g of decanediamine, 120.2 g of dodecanediamine, 210.4 g of 4,4'-diaminodicyclohexylmethane, 3.2 g of stearic acid, 5 g of antioxidant, and an appropriate amount of water into a high-pressure reactor with numerical control heating; (2) After purging with nitrogen 3 times, slowly raise the temperature to 130 °C, start stirring, and continue to raise the temperature to 190 °C. During this period, keep the pressure rising continuously, and react for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255 °C - 265 °C; (3) Release the pressure to atmospheric pressure and stir and react for 1 h under the condition of a temperature of 255 °C - 265 °C; (4) Evacuate to a vacuum, and carry out a second polycondensation reaction for 0.5 h - 1 h under the conditions of a vacuum degree < 200 Pa and a temperature of 250 °C - 260 °C until the melt index meets the requirements; (5) Break the vacuum, discharge the material under nitrogen protection, draw into strips, cut underwater, and dry to obtain the product.

[0017] The product sample obtained through Example 1 is marked as A1. Example 2

[0018] A preparation method of a copolymerized polyamide hot-melt adhesive with high transparency, ultraviolet resistance, and resistance to wet heat aging is as follows: (1) Add 394.6 g of laurolactam, 80.9 g of sebacic acid, 92.1 g of dodecanedioic acid, 293.2 g of tridecanedioic acid, 103.4 g of decanediamine, 200.4 g of dodecanediamine, 84.1 g of 4,4'-diaminodicyclohexylmethane, 6 g of stearic acid, 4 g of antioxidant, and an appropriate amount of water into a high-pressure reactor with numerical control heating; (2) After purging with nitrogen three times, slowly raise the temperature to 130 °C, start stirring, and continue to raise the temperature to 190 °C. During this period, keep the pressure rising continuously, and react for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255 °C - 265 °C; (3) Release the pressure to atmospheric pressure, and stir and react for 1 h under the condition of a temperature of 255 °C - 265 °C; (4) Evacuate to a vacuum, and carry out a re-polycondensation reaction for 0.5 h - 1 h under the conditions of a vacuum degree < 200 Pa and a temperature of 250 °C - 260 °C until the melt index meets the requirements; (5) Break the vacuum, and discharge, draw into strands, underwater pelletize, and dry under nitrogen protection to obtain the product.

[0019] The product sample obtained through Example 2 is labeled as A2. Example 3

[0020] A preparation method of a copolymerized polyamide hot melt adhesive with high transparency, ultraviolet resistance, and resistance to hygrothermal aging is as follows: (1) Add 113.2 g of caprolactam, 197.3 g of laurolactam, 101.1 g of sebacic acid, 115.2 g of dodecanedioic acid, 366.5 g of tridecanedioic acid, 172.3 g of decanediamine, 100.2 g of dodecanediamine, 119.2 g of bis(3-methyl-4-aminocyclohexyl)methane, 5 g of stearic acid, 4 g of antioxidant, and an appropriate amount of water into a high-pressure reactor with numerical control heating; (2) After purging with nitrogen three times, slowly raise the temperature to 130 °C, start stirring, and continue to raise the temperature to 190 °C. During this period, keep the pressure rising continuously, and react for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255 °C - 265 °C; (3) Release the pressure to atmospheric pressure, and stir and react for 1 h under the condition of a temperature of 255 °C - 265 °C; (4) Evacuate to a vacuum, and carry out a re-polycondensation reaction for 0.5 h - 1 h under the conditions of a vacuum degree < 200 Pa and a temperature of 250 °C - 260 °C until the melt index meets the requirements; (5) Break the vacuum, and discharge, draw into strands, underwater pelletize, and dry under nitrogen protection to obtain the product.

[0021] The product sample obtained through Example 3 is labeled as A3. Example 4

[0022] A preparation method of a high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging-resistant copolyamide hot melt adhesive comprises the following steps: (1) Add 282.9 g of caprolactam, 40.5 g of sebacic acid, 69.1 g of dodecanedioic acid, 122.2 g of tridecanedioic acid, 172.368.9 g of decanediamine, 60.1 g of dodecanediamine, 42.7 g of 1,3-cyclohexanedimethanamine, 3 g of stearic acid, 2 g of antioxidant, and an appropriate amount of water into a high-pressure reactor with numerical control heating; (2) After replacing the nitrogen three times, slowly raise the temperature to 130 °C, start stirring, and continue to raise the temperature to 190 °C. During this period, keep the pressure rising continuously, and react for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255 °C - 265 °C; (3) Release the pressure to atmospheric pressure, and stir and react for 1 h under the condition of a temperature of 255 °C - 265 °C; (4) Evacuate to a vacuum, and conduct a second polycondensation reaction for 0.5 h - 1 h under the conditions of a vacuum degree < 200 Pa and a temperature of 250 °C - 260 °C until the melt index meets the requirements; (5) Break the vacuum, and discharge, extrude, underwater pelletize, and dry the product under nitrogen protection to obtain the product.

[0023] The product sample obtained through Example 4 is labeled as A4. Example 5

[0024] A preparation method of a high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging-resistant copolyamide hot melt adhesive comprises the following steps: (1) Add 226.3 g of caprolactam, 197.3 g of laurolactam, 202.3 g of sebacic acid, 92.1 g of dodecanedioic acid, 146.6 g of tridecanedioic acid, 120.6 g of decanediamine, 140.3 g of dodecanediamine, 143.1 g of bis(3-methyl-4-aminocyclohexyl)methane, 6 g of stearic acid, 4 g of antioxidant, and an appropriate amount of water into a high-pressure reactor with numerical control heating; (2) After replacing the nitrogen three times, slowly raise the temperature to 130 °C, start stirring, and continue to raise the temperature to 190 °C. During this period, keep the pressure rising continuously, and react for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255 °C - 265 °C; (3) Release the pressure to atmospheric pressure, and stir and react for 1 h under the condition of a temperature of 255 °C - 265 °C; (4) Evacuate to a vacuum, and conduct a second polycondensation reaction for 0.5 h - 1 h under the conditions of a vacuum degree < 200 Pa and a temperature of 250 °C - 260 °C until the melt index meets the requirements; (5) Break the vacuum, and discharge, extrude, underwater pelletize, and dry the product under nitrogen protection to obtain the product.

[0025] The product sample obtained from Example 5 is labeled as A5.

[0026] Comparative Example 1 Compared with Example 1, the main difference lies in the ratio of aliphatic diamine and alicyclic diamine. The alicyclic diamine is slightly added in excess. Specifically, the addition amount of 4,4'-diaminodicyclohexylmethane is 315.6 g, and the usage amounts and proportions of other raw materials remain unchanged.

[0027] The product sample obtained from Comparative Example 1 is labeled as D1.

[0028] Comparative Example 2 Compared with Example 2, the main difference lies in the ratio of aliphatic diamine and alicyclic diamine. The aliphatic diamine is slightly added in excess. Specifically, the addition amount of sebac diamine is 172.3 g, and the usage amounts and proportions of other raw materials remain unchanged.

[0029] The product sample obtained from Comparative Example 2 is labeled as D2.

[0030] Index and performance test The samples A1 - A5, D1 and D2 obtained from the above-mentioned examples and comparative examples, and a commercially available conventional amorphous copolyamide hot melt adhesive (model 2130) are subjected to relevant index and performance tests. Among them, the softening point test standard refers to: GB / T 15332 - 1994; the melt index test standard refers to: GB / T 3682.1 - 2018; the peel strength test refers to: FZ / T 01085 - 2009; the transparency test refers to: GB / T 2410 - 2008; the yellowing index (ΔYI) after heat and humidity aging and ultraviolet light aging both refer to: GB2409 - 80.

[0031] The specific results are shown in Table 1 below: Table 1: Index and performance test table.

[0032] From Table 1 above, it can be clearly seen that the copolyamide hot melt adhesives (A1 - A5) prepared within the range of raw material selection and ratio design of the present invention are as convenient for sizing and ensure the bonding effect as the commercially available conventional amorphous copolyamide hot melt adhesives. However, in terms of light transmittance, ultraviolet aging resistance, and heat and humidity aging resistance performance, they are significantly improved and perform excellently. The comparative example samples D1 and D2 are supplementary verification tests, and in the ratio design of diamine, they exceed the recommended range of the present invention. In D1, the alicyclic diamine is added in excess, and although the product has a significant improvement in light transmittance, ultraviolet aging resistance, and heat and humidity aging resistance performance, it cannot meet the basic bonding performance; in D2, the alicyclic diamine is less, although it can meet the basic bonding performance, the light transmittance is less improved, and the ultraviolet aging resistance and heat and humidity aging resistance performance cannot meet the requirements.

Claims

1. A preparation method of a high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive, characterized in that, It includes the following steps: (1) Add lactam, aliphatic dicarboxylic acid, aliphatic diamine, alicyclic diamine, molecular weight regulator, antioxidant and water into a reaction kettle according to a preset ratio; (2) Replace with nitrogen for 1 - 3 times, then slowly heat up to 130°C, start stirring, and continue to heat up to 190°C. During this period, keep the pressure rising continuously. React for 1.5 h under the conditions of a pressure of 1.45 MPa - 1.55 MPa and a temperature of 255°C - 265°C; (3) Release to atmospheric pressure and stir - react for 1 h under the condition of a temperature of 255°C - 265°C; (4) Evacuate to vacuum, and carry out polycondensation reaction again for 0.5 h - 1 h under the conditions of a vacuum degree < 200 Pa and a temperature of 250°C - 260°C; (5) Break the vacuum and discharge the product under nitrogen protection to obtain the product; In the step (1), the molar ratio of lactam: the sum of aliphatic dicarboxylic acid, aliphatic diamine and alicyclic diamine is 1 - 2.5:1:0.95 - 1, and the molar ratio of aliphatic diamine: alicyclic diamine is 1 - 4:

1.

2. The preparation method of the high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 1, characterized in that: The alicyclic diamine includes two rings connected by an alkylene group containing 1 - 6 carbon atoms, and each ring is substituted by an amine group and an alkyl group which may be the same or different and contains 1 - 6 carbon atoms.

3. The preparation method of the high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 1 or 2, characterized in that: The alicyclic diamine is selected from one of 1,3 - cyclohexanedimethanamine, 4,4’ - diaminodicyclohexylmethane, bis(3 - methyl - 4 - aminocyclohexyl)methane.

4. The preparation method of the high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 1, characterized in that: The aliphatic dicarboxylic acid and aliphatic diamine are of long carbon chains, and the carbon chain length in their molecular chains is ≥ 10.

5. The preparation method of the high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 1 or 4, characterized in that: The aliphatic dicarboxylic acid is composed of a blend of sebacic acid, dodecanedioic acid and tridecanedioic acid; the aliphatic diamine is composed of a blend of decanediamine and dodecanediamine.

6. The preparation method of the high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 1 or 4, characterized in that: The lactam is caprolactam, laurolactam, or a mixture of both.

7. The preparation method of the high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 1, characterized in that: The molecular weight regulator is stearic acid, and its addition amount is 0.3% - 0.5% of the total mass of the lactam, dicarboxylic acid and diamine raw materials; the antioxidant grade is selected from one of 1010, 168, 1098 or S - 682, and its addition amount is 0.2% - 0.5% of the total mass of the lactam, dicarboxylic acid and diamine raw materials.

8. A high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive, characterized in that: The raw material composition includes lactam, aliphatic dicarboxylic acid, aliphatic diamine, alicyclic diamine, molecular weight regulator, antioxidant; the molar ratio of lactam: the sum of aliphatic dicarboxylic acid, aliphatic diamine and alicyclic diamine is 1 - 2.5:1:0.95 - 1; and the molar ratio of aliphatic diamine: alicyclic diamine is 1 - 4:

1.

9. The high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 8, characterized in that: The alicyclic diamine is selected from one of 1,3 - cyclohexanedimethanamine, 4,4’ - diaminodicyclohexylmethane, bis(3 - methyl - 4 - aminocyclohexyl)methane.

10. The high-transparency, ultraviolet-resistant, and moisture- and heat-resistant aging copolymeramide hot melt adhesive according to claim 9, characterized in that: The aliphatic dibasic acid is composed of a blend of sebacic acid, dodecanedioic acid, and tridecanedioic acid; the aliphatic diamine is composed of a blend of decanediamine and dodecanediamine; the lactam is caprolactam, laurolactam, or a mixture of both; the molecular weight regulator is stearic acid, and its addition amount is 0.3% - 0.5% of the total mass of the lactam, dibasic acid, and diamine raw materials; the antioxidant grade is selected from one of 1010, 168, 1098, or S-682, and its addition amount is 0.2% - 0.5% of the total mass of the lactam, dibasic acid, and diamine raw materials.