Cross-linked toughened low-temperature hot-melt adhesive polyester chips and preparation method thereof

Abstract

The invention discloses a cross-linked toughened modified low-temperature hot-melt adhesive polyester chip and a preparation method thereof. A semi-continuous production synthesis device is used. During the esterification reaction process, different diols, triols and dibasic acids are introduced in three steps. Each esterification step is completed in stages by controlling the addition sequence and the reaction temperature, ensuring that the replaced alcohol and acid can generate specific esterification segments, thereby achieving the purpose of cross-linking and toughening modification. After the esterification is completed, the esterified product is introduced into a polycondensation reaction device through a 15-25 μm filter and nitrogen pressurization. The polycondensation reaction temperature, vacuum degree, stirring rate and final temperature are controlled to achieve preset values ​​before discharging. The intrinsic viscosity is ensured to be 0.450±0.005 dl / g and the melt index is achieved to be above 65 g / 10 min (160° C. / 2160 g). The high-temperature melt passes through a casting head, an underwater pelletizing device and a drying device, finally obtaining the cross-linked toughened modified low-temperature hot-melt adhesive polyester chip.

Description

Technical Field

[0001] The invention relates to a polyester chip and a preparation method thereof, in particular to a cross-linked toughened modified low-temperature hot melt adhesive polyester chip and a preparation method thereof. Background Art

[0002] In recent years, modified materials based on PET as a main chain have emerged in large numbers, with one area of ​​focus being low-temperature bonding. Low-temperature hot-melt filaments have long dominated this application, widely used in fabric bonding. With the continued advancement of PET adhesive development, a new modification direction has emerged: low-temperature hot-melt polyester chips for milling. This product eliminates the need for complex spinning processes and instead undergoes direct pulverization under liquid nitrogen cooling, resulting in simpler equipment and a more straightforward process, making it increasingly popular with downstream customers. However, while these low-temperature hot-melt polyester chips for milling often use PET chips with low intrinsic viscosity, their low intrinsic viscosity can lead to problems such as dusting, separation, and delamination during subsequent use, and their resistance to 40°C water washing is limited. The underlying reason for this is that conventional modified low-temperature hot-melt polyester chips for milling are too brittle and lack toughness, a common drawback of low-intrinsic-viscosity PET materials. Therefore, how to improve chip toughness without altering the overall intrinsic viscosity remains a key technical challenge for milling low-temperature hot-melt polyester chips. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a cross-linked toughened modified low-temperature hot melt adhesive polyester chip and a preparation method thereof. The polyester chip of the present invention is used to produce and process powdered hot melt adhesive. In addition to having the advantages of low melting range, high melt index, low bonding heat requirement, and high bonding strength, it also solves the problem of strong brittleness of PET at low intrinsic viscosity. When used by downstream customers, the strength of the multi-layer composite is significantly improved, and the time of resistance to 40°C water washing is greatly extended.

[0004] In order to achieve the above excellent product properties and to solve the existing usage problems of conventional low-temperature hot-melt adhesive polyester chips for grinding, the technical solution adopted by the present invention is: a cross-linked toughened modified low-temperature hot-melt adhesive polyester chip and a preparation method thereof. The chemical structure of the target product is as follows:

[0005]

[0006] Where m1:n1:z1=(10.1-58.5):(7.7-36.2):1

[0007] m2:n2:z2=(10.1-58.5):(7.7-36.2):1

[0008] m3:n3:z3=(10.1-58.5):(7.7-36.2):1

[0009] To achieve the above chemical structure, the following process control steps are required:

[0010] ① Add a certain amount of ethylene glycol and diethylene glycol to a beating kettle, and then add a certain amount of terephthalic acid solid powder to prepare a viscous slurry, which is then pumped into the esterification reactor through a slurry pump to start the first step of the esterification reaction; wherein the molar ratio of terephthalic acid to the total acid in the esterification reaction is 95%-99%, the molar ratio of ethylene glycol to the total alcohol in the esterification reaction is 46%-68.9%, and the molar ratio of diethylene glycol to the total alcohol in the esterification reaction is 30%-50%;

[0011] ② During the esterification process in step ①, the feed port of the diesterification reactor is opened, a certain amount of 1,2-propylene glycol is added and stirring is started, and then a certain amount of adipic acid is added, the reactor is covered and the temperature is increased to carry out a simultaneous esterification reaction; wherein the molar ratio of adipic acid to the total acid in the esterification reaction is 1%-5%, and the molar ratio of 1,2-propylene glycol to the total alcohol in the esterification reaction is 1%-5%;

[0012] ③ After the raw materials added in ① and ② have reacted completely, the material from reaction ① is introduced into the material from reaction ②, the temperature is increased and stirring is started, and esterification is continued for 30-50 minutes. Then, a certain amount of glycerol is added from the material pipeline. During the addition process, stirring and heating are kept on, and the temperature is controlled to be constant for the third step of esterification reaction; wherein the molar ratio of glycerol to the total alcohol in the esterification reaction is 0.1%-1%, and the molar ratio of total acid to total alcohol in the three esterification reactions is 1:(1.25-1.45);

[0013] ④ After the reaction in step ③ is completed, add the catalyst, toner, and antioxidant from the auxiliary agent port. When the slurry temperature stabilizes to 255-265°C, the materials in the diesterification reactor are pressed into the polycondensation reactor through a 15-25μm stainless steel filter using high-purity nitrogen;

[0014] ⑤ After the mixed slurry enters the polycondensation kettle, the temperature begins to rise and low vacuum is drawn; the reaction temperature is controlled at 245-265℃, and a negative pressure polymerization reaction is carried out, requiring the vacuum degree to be ≤30Pa. At the final temperature of 260-265℃, the stirring polycondensation current and power are controlled by the equipment to synthesize a polyester chip melt with an intrinsic viscosity of 0.440-0.460dl / g, and then pass through a casting head, an underwater pelletizer, a dryer, and a vibrating screen to finally obtain a cross-linked, toughened, and modified low-temperature hot melt adhesive polyester chip.

[0015] The cross-linked toughened modified low-temperature hot melt adhesive polyester chips and the preparation method thereof are characterized in that the molar ratio of the alkyd acid in the three-step esterification reaction is required to be greater than 1, the esterification temperature of the first and second steps is controlled at 200-220°C, after the slurry of the first esterification kettle and the diesterization kettle is mixed, the esterification temperature of the diesterization kettle is controlled at 220-240°C, and the temperature of the third step is controlled at 240-260°C.

[0016] The catalyst is a chelated titanium catalyst with a titanium content of 3%-7%, and the added amount is 100-200ppm of the theoretical polyester chip output; the toner is a fluorescent whitening agent, and the added amount is 60-90ppm of the theoretical polyester chip output; the antioxidants are 1010 and DLTP, wherein the added amount of antioxidant 1010 is 400-800ppm of the theoretical polyester output, and the added amount of antioxidant DLTP is 100-200ppm of the theoretical polyester chip output.

[0017] The cross-linked toughened and modified low-temperature hot-melt adhesive polyester chips are prepared by the above preparation method.

[0018] The beneficial effects of the present invention are:

[0019] 1. Through the step-by-step esterification operation, the modified diols, triols and dibasic acids can be introduced into the esterified segments in a targeted manner, ensuring that different segments exert different physical properties. This is the basis for product process control and subsequent special performance. In particular, the cross-linking effect of the triol and the intermolecular force of 1,2-propylene glycol are the main sources of increased toughness and reduced brittleness of the target product.

[0020] 2. At the same time, the introduction of a large amount of diethylene glycol to replace traditional ethylene glycol can greatly improve the fluidity of polyester chips in semi-fluid and fluid states, ensuring that the target product can achieve at least double the melt index of 30g / 10min (160℃ / 2160g) of conventional milling low-temperature hot melt adhesive polyester chips while enhancing the apparent toughness;

[0021] 3. By introducing an appropriate amount of 1,2-propylene glycol monomer, the bonding strength of the ground powder can be further improved. Compared with the conventional low-temperature hot-melt adhesive polyester chips for grinding powder of the same quality, the bonding strength of the target product can be improved by more than 10%;

[0022] 4. By introducing adipic acid, diethylene glycol, 1,2-propylene glycol, and propylene glycol, the melting range of the target product is significantly reduced, which is also the structural basis for ensuring the product's excellent ironing and bonding properties. Moreover, the above mixed alcohols not only change the melting point, but also improve the target product's anti-hydrolysis performance through the synergistic effect between the alcohols, and enhance its stability in 40°C water. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments:

[0024] The present invention provides a method for preparing a cross-linked toughened and modified low-temperature hot-melt adhesive polyester chip, comprising the following steps:

[0025] ① Add a certain amount of ethylene glycol and diethylene glycol to a beating kettle, and then add a certain amount of terephthalic acid solid powder to prepare a viscous slurry, which is then pumped into the esterification reactor through a slurry pump to start the first step of the esterification reaction; wherein the molar ratio of terephthalic acid to the total acid in the esterification reaction is 95%-99%, the molar ratio of ethylene glycol to the total alcohol in the esterification reaction is 46%-68.9%, and the molar ratio of diethylene glycol to the total alcohol in the esterification reaction is 30%-50%;

[0026] ② During the esterification process in step ①, the feed port of the diesterification reactor is opened, a certain amount of 1,2-propylene glycol is added and stirring is started, and then a certain amount of adipic acid is added, the reactor is covered and the temperature is increased to carry out a simultaneous esterification reaction; wherein the molar ratio of adipic acid to the total acid in the esterification reaction is 1%-5%, and the molar ratio of 1,2-propylene glycol to the total alcohol in the esterification reaction is 1%-5%;

[0027] ③ After the raw materials added in ① and ② have reacted completely, the material from reaction ① is introduced into the material from reaction ②, the temperature is increased and stirring is started, and esterification is continued for 30-50 minutes. Then, a certain amount of glycerol is added from the material pipeline. During the addition process, stirring and heating are kept on, and the temperature is controlled to be constant for the third step of esterification reaction; wherein the molar ratio of glycerol to the total alcohol in the esterification reaction is 0.1%-1%, and the molar ratio of total acid to total alcohol in the three esterification reactions is 1:(1.25-1.45);

[0028] ④ After the reaction in step ③ is completed, add the catalyst, toner, and antioxidant from the auxiliary agent port. When the slurry temperature stabilizes to 255-265°C, the materials in the diesterification reactor are pressed into the polycondensation reactor through a 15-25μm stainless steel filter using high-purity nitrogen;

[0029] ⑤ After the mixed slurry enters the polycondensation kettle, the temperature begins to rise and low vacuum is drawn; the reaction temperature is controlled at 245-265℃, and a negative pressure polymerization reaction is carried out, requiring the vacuum degree to be ≤30Pa. At the final temperature of 260-265℃, the stirring polycondensation current and power are controlled by the equipment to synthesize a polyester chip melt with an intrinsic viscosity of 0.440-0.460dl / g, and then pass through a casting head, an underwater pelletizer, a dryer, and a vibrating screen to finally obtain a cross-linked, toughened, and modified low-temperature hot melt adhesive polyester chip.

[0030] In terms of esterification control, the molar ratio of alcohol and acid in the three-step esterification reaction is required to be greater than 1, the esterification temperature of the first and second steps is controlled at 200-220℃, after the slurry of the first esterification kettle and the second esterification kettle is mixed, the esterification temperature of the second esterification kettle is controlled at 220-240℃, and the temperature of the third step is controlled at 240-260℃.

[0031] The catalyst used in the reaction system is a chelated titanium catalyst, the toner is a fluorescent whitening agent, and the antioxidants are 1010 and DLTP.

[0032] The chelated titanium catalyst is required to have a titanium content of 3%-7% and be added in an amount of 100-200 ppm based on the theoretical polyester chip yield. The fluorescent brightener is added in an amount of 60-90 ppm based on the theoretical polyester chip yield, while the antioxidant 1010 is added in an amount of 400-800 ppm based on the theoretical polyester yield, and the antioxidant DLTP is added in an amount of 100-200 ppm based on the theoretical polyester chip yield.

[0033] The cross-linked toughened and modified low-temperature hot-melt adhesive polyester chips are prepared by the above preparation method.

[0034] Compared with existing products, conventional grinding low-temperature hot melt adhesive polyester chips have the following shortcomings:

[0035] 1. The lowest melting range of conventional low-temperature hot-melt polyester chips for grinding is currently around 100-120°C. Later processing requires more heat and longer ironing time. However, the melting range of this product can continue to drop by more than 10°C, which can greatly reduce ironing heat consumption and ironing residence time.

[0036] 2. When the same amount of conventional milled powder is processed into powder with low-temperature hot-melt polyester chips, the bonding strength of this product is increased by more than 10%;

[0037] 3. The melt index of conventional low-temperature hot-melt adhesive polyester chips for grinding is generally 30-35g / 10min (160℃ / 2160g). The melt index of this product can reach above 60g / 10min (160℃ / 2160g). Good fluidity can combine with the material surface faster during ironing, increasing the bonding contact area.

[0038] 4. When the same amount of conventional grinding low-temperature hot-melt adhesive polyester chips and this product are bonded according to the same process, the latter can withstand 40°C water washing time twice as long as the former, reaching 40 minutes, and the peel strength decay is less than 30%.

[0039] The polyester chips prepared by the present invention solve these pain points and difficulties in use, and it is necessary to implement synchronous control of various indicators in the synthesis of the product of the present invention:

[0040] 1. Structural control of target products

[0041] Through the three-step esterification method, the flexibility of the semi-continuous production line is fully utilized to control the order of feeding, the reaction vessel for feeding, and the reaction temperature, and to directionally generate modified chain segments of polyester chips, ultimately achieving structural control of the target product and achieving the desired modification purpose.

[0042] 2. Melting range control technology solution:

[0043] By introducing homologues of ethylene glycol, alternative acids to terephthalic acid and stable triols, the chain structure of conventional PET polyester is changed, thereby achieving an ultra-low melting range of the target product. The realization of this melting range control also lays the foundation for reducing the ironing temperature and compressing the ironing time in subsequent use.

[0044] 3. Rong melt index control technology solution:

[0045] By introducing a large amount of diethylene glycol to replace traditional ethylene glycol, the fluidity of polyester chips in semi-fluid and fluid states is further improved. The melt index of less than 10g / 10min (160℃ / 2160g) of conventional low-melting-point hot-melt wire has increased by more than six times, and the melt index of 35g / 10min (160℃ / 2160g) of conventional low-temperature hot-melt adhesive polyester chips for grinding has increased by nearly 1 times to more than 60g / 10min (160℃ / 2160g). With the same ironing time, the contact area of ​​the materials is larger, which is also the key to ensuring the reliability of the bond.

[0046] 4. Technical solution for controlling bonding reliability:

[0047] By introducing an appropriate amount of 1,2-propylene glycol monomer, the bonding strength of the ground powder can be further improved. Compared with the conventional low-temperature hot-melt adhesive polyester chips for grinding of the target product of the same quality, the bonding strength can be improved by more than 10%.

[0048] 5. Technical solution for 40℃ water washing resistance:

[0049] By introducing propylene glycol and 1,2-propylene glycol in the esterification stage, cross-linking and molecular entanglement of the polyester long chain are achieved, and the apparent toughness is significantly enhanced; at the same time, the introduction of a variety of ethylene glycol alternatives to alcohols makes the product molecular structure more complex and the hydrolysis resistance of the chain segments is enhanced. The most intuitive manifestation in use is the enhanced water washability.

[0050] Example 1

[0051] ① Add 480 kg of ethylene glycol and 900 kg of diethylene glycol into the beating kettle, and then add 1970 kg of terephthalic acid solid powder to prepare a viscous slurry. Pump it into the esterification reactor through the slurry pump and control the esterification temperature at 220 ° C to start the first step of the esterification reaction;

[0052] ② During the esterification process in step ①, open the diesterification reactor feed port, add 60 kg of 1,2-propylene glycol and start stirring, then add 85 kg of adipic acid, cover and start heating, control the internal temperature at 220°C, and carry out the simultaneous esterification reaction;

[0053] ③ After the reaction of the raw materials added in ① and ② is complete, the materials from reaction ① are introduced into the materials from reaction ②, the temperature is increased and stirred, and the temperature in the diester reactor is controlled at 235°C. After continuing the esterification for 30-50 minutes, 16 kg of glycerol is added from the material pipeline. During the addition process, stirring and heating are kept on, and the temperature in the diester reactor is controlled at 250°C to carry out the third step of esterification reaction;

[0054] ④ After the reaction in step ③ is completed, 250g of chelated titanium catalyst, 150g of fluorescent whitening agent, 1000g of antioxidant 1010 and 250g of antioxidant DLTP are added from the auxiliary agent port. When the slurry temperature stabilizes to 255-265°C, the materials in the diesterification reactor are pressed into the polycondensation reactor by high-purity nitrogen through a 15-25μm stainless steel filter;

[0055] ⑤ After the mixed slurry enters the polycondensation kettle, the temperature begins to rise and low vacuum is drawn; the reaction temperature is controlled at 260°C, and a negative pressure polymerization reaction is carried out, requiring the vacuum degree to be ≤30Pa. At the final temperature of 260°C, the stirring polycondensation current and power are controlled by the equipment to synthesize a polyester chip melt with a characteristic viscosity of 0.448dl / g. After passing through a casting head, an underwater pelletizer, a dryer, and a vibrating screen, a cross-linked, toughened, and modified low-temperature hot melt adhesive polyester chip is finally obtained.

[0056] Follow steps ① to ④ to implement 2-4 other examples. See Table 1 for specific data:

[0057] Table 1:

[0058] Parameter items Example 1 Example 2 Example 3 Example 4 4-Benzenedicarboxylic acid / Kg 1970 1910 1950 1940 Adipic acid / Kg 85 20 70 50 Ethylene glycol / Kg 480 700 600 550 Diethylene glycol / Kg 900 530 700 650 1,2-Propanediol / Kg 60 12 40 50 Glycerol / Kg 16 2 8 10

[0059] The cross-linked, toughened, and modified low-temperature hot-melt adhesive polyester chips of the present invention have a higher melt index, a lower melting range, high toughness, and low brittleness compared to conventional low-melting-point hot-melt polyester chips. Customers can experience better fluidity and better bonding reliability during use, and the ironing time and ironing temperature are significantly shortened and reduced, especially with significantly improved resistance to 40°C water washing.

[0060] The following is explained in conjunction with specific embodiments:

[0061] For the cross-linked toughened low-temperature hot-melt adhesive polyester chips in Examples 1-4 above, all test samples used the same powder dosage, the thickness of the bonded fabric was uniformly selected to be 40D, the ironing time was 13 seconds, the ironing temperature was 115°C, and the peel strength was tested before and after washing at 40°C for 40 minutes. The test results are summarized in Table 2 below:

[0062] Table 2:

[0063]

[0064] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The scope of the patent of the present invention cannot be limited by these embodiments alone. That is, any equivalent changes or modifications made to the spirit disclosed by the present invention still fall within the scope of the patent of the present invention.

Claims

1. A method for preparing cross-linked toughened low-temperature hot melt adhesive polyester chips, characterized in that: The following steps are involved: ① Add a certain amount of ethylene glycol and diethylene glycol to a beating kettle, and then add a certain amount of terephthalic acid solid powder to prepare a viscous slurry, which is then pumped into the esterification reactor through a slurry pump to start the first step of the esterification reaction; wherein the molar ratio of terephthalic acid to the total acid in the esterification reaction is 95%-99%, the molar ratio of ethylene glycol to the total alcohol in the esterification reaction is 46%-68.9%, and the molar ratio of diethylene glycol to the total alcohol in the esterification reaction is 30%-50%; ② During the esterification process in step ①, the feed port of the diesterification reactor is opened, a certain amount of 1,2-propylene glycol is added and stirring is started, and then a certain amount of adipic acid is added, the reactor is covered and the temperature is increased to carry out a simultaneous esterification reaction; wherein the molar ratio of adipic acid to the total acid in the esterification reaction is 1%-5%, and the molar ratio of 1,2-propylene glycol to the total alcohol in the esterification reaction is 1%-5%; ③ After the raw materials added in ① and ② have reacted completely, the material from reaction ① is introduced into the material from reaction ②, the temperature is increased and stirring is started, and the esterification is continued for 30-50 minutes. Then, a certain amount of glycerol is added from the material pipeline. Stirring and heating are kept on during the addition process to carry out the third step of esterification reaction; wherein the molar ratio of glycerol to the total alcohol in the esterification reaction is 0.1%-1%, and the molar ratio of total acid to total alcohol in the three esterification reactions is 1:(1.25-1.45); ④ After the reaction in step ③ is completed, add the catalyst, toner, and antioxidant from the auxiliary agent port. When the slurry temperature stabilizes to 255-265°C, the materials in the diesterification reactor are pressed into the polycondensation reactor through a 15-25μm stainless steel filter using high-purity nitrogen; ⑤ After the mixed slurry enters the polycondensation kettle, the temperature begins to rise and low vacuum is drawn; the reaction temperature is controlled at 245-265℃, and a negative pressure polymerization reaction is carried out, requiring the vacuum degree to be ≤30Pa. At the final temperature of 260-265℃, the stirring polycondensation current and power are controlled by the equipment to synthesize a polyester chip melt with an intrinsic viscosity of 0.440-0.460dl / g, and then pass through a casting head, an underwater pelletizer, a dryer, and a vibrating screen to finally obtain a cross-linked, toughened, and modified low-temperature hot melt adhesive polyester chip.

2. The method for preparing the cross-linked toughened low-temperature hot melt adhesive polyester chips according to claim 1, characterized in that: The molar ratio of alcohol and acid in the three-step esterification reaction is required to be greater than 1. The esterification temperature of the first and second steps is controlled at 200-220℃. After the slurry of the first esterification kettle and the second esterification kettle is mixed, the esterification temperature of the second esterification kettle is controlled at 220-240℃. The temperature of the third step is controlled at 240-260℃.

3. The method for preparing the cross-linked toughened low-temperature hot melt adhesive polyester chips according to claim 1, characterized in that: The catalyst is a chelated titanium catalyst, the toner is a fluorescent whitening agent, and the antioxidants are 1010 and DLTP.

4. The method for preparing the cross-linked toughened low-temperature hot melt adhesive polyester chips according to claim 3, characterized in that: The titanium content of the chelated titanium catalyst is 3%-7%, and the added amount is 100-200ppm of the theoretical polyester chip output.

5. The method for preparing the cross-linked toughened low-temperature hot melt adhesive polyester chips according to claim 3, characterized in that: The amount of the fluorescent whitening agent added is 60-90 ppm of the theoretical polyester chip output, the amount of the antioxidant 1010 added is 400-800 ppm of the theoretical polyester output, and the amount of the antioxidant DLTP added is 100-200 ppm of the theoretical polyester chip output.

6. A cross-linked, toughened and modified low-temperature hot-melt adhesive polyester chip prepared by the preparation method according to any one of claims 1 to 5.

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