Polyester hot melt adhesive, preparation method thereof and application of polyester hot melt adhesive in field of easy-to-peel labels

Abstract

The invention belongs to the technical field of preparation of hot melt adhesives, and relates to a polyester hot melt adhesive, a preparation method thereof and application in the field of easy-to-peel labels, the structural formula of the polyester hot melt adhesive is shown in the specification, and the preparation method comprises the following steps: controlling copolyester with a melting point lower than 160 DEG C and a cross-linking agent with a molecular chain containing beta-thioacid ester bonds to generate a cross-linking reaction to obtain the polyester hot melt adhesive; the polyester hot melt adhesive can be applied to the field of labels; the problems of adhesive recovery residues, insufficient adhesion, health harm and material adaptation limitation are solved.

Description

Technical Field

[0001] This invention belongs to the field of hot melt adhesive preparation technology, and relates to a polyester hot melt adhesive, its preparation method, and its application in the field of easy-to-peel labels. Background Technology

[0002] As plastic pollution worsens, improving waste recycling systems has become a crucial aspect of green development. Polyethylene terephthalate (PET), due to its excellent properties, is widely used in plastic bottles and packaging. Its recycling can significantly reduce reliance on petroleum-based raw materials and decrease carbon footprint, offering both economic and environmental value. However, the purity of recycled PET (r-PET) directly determines the quality of subsequent products such as food-grade packaging and textiles. The adhesives used for labels on PET bottles / packaging surfaces have become a core obstacle to the efficient and high-value recycling of PET.

[0003] Currently, commonly used adhesives for label bonding include EVA-based hot melt adhesives, water-based acrylic adhesives, solvent-based adhesives, and some modified hot melt adhesives. These adhesives often fail to effectively peel off during the cleaning and crushing processes of recycled PET, or leave residues after peeling. This leads to yellowing and carbonization impurities during r-PET processing, severely affecting purity and quality. Adding complex impurity removal processes significantly increases energy consumption and processing costs. While existing technologies have proposed improvements to address "easy peeling," they still have many shortcomings and cannot simultaneously meet the requirements of "high bonding strength," "environmentally friendly and harmless," and "adaptability to multiple recycling scenarios."

[0004] Some easy-peel hot melt adhesives exhibit significant selectivity regarding label materials, and the adhesive and label are difficult to separate after peeling. For example, the polyester-based easy-peel hot melt adhesive disclosed in patent application CN117089308A requires heating to above 80-85℃ to peel off the label. This temperature is higher than the softening point of polyvinyl chloride (PVC) labels, easily causing the hot melt adhesive to stick to the PVC label after peeling, making effective separation impossible and resulting in resource waste. Furthermore, this type of hot melt adhesive is only suitable for labels made of non-PVC materials, severely limiting its applicability.

[0005] Furthermore, easy-peel hot melt adhesives are difficult to meet the requirements of high-bonding-strength applications. For example, the EVA-type easy-peel hot melt adhesive disclosed in patent CN106833435B reduces peel strength by adding tackifying resins, waxes, pentaerythritol stearate, and other components. Although this achieves easy peeling, it also results in insufficient bonding strength. In packaging scenarios where high bonding stability is required, such as heavy-duty packaging and long-term storage packaging, it cannot meet the actual usage needs and has poor versatility.

[0006] Some washable hot melt adhesives are prone to generating volatile organic compounds (VOCs) during use, which can harm the health of operators. For example, the alkaline water-washable hot melt adhesive disclosed in patent application CN106085351A contains small molecule additives such as plasticizers in its formula. These additives are easily volatilized during the heating and use of the hot melt adhesive, generating VOCs, which pose a direct threat to the health of operators who are exposed to them for a long time, and do not meet the current environmental protection and health production requirements.

[0007] Another type of green label adhesive suffers from poor adhesion and insufficient stability. For example, the starch-based green label adhesive disclosed in patent application CN106675515A, which uses Bletilla striata and sweet potato extract as raw materials, can remove labels in warm water. However, this type of adhesive has low bonding strength and cannot withstand the external forces during packaging and transportation. Furthermore, its long curing time affects production efficiency, and it is also prone to mold growth, making it unsuitable for humid storage environments and unable to meet the requirements of actual industrial packaging.

[0008] In addition, existing technologies also use polyacrylate self-adhesive labels. Although the adhesive layer structure can be destroyed by weak acid treatment to achieve peeling, this type of self-adhesive is more sensitive to temperature and oil, has insufficient long-term adhesion, and the labels are easy to fall off during use. It has a short service life and cannot be adapted to PET packaging scenarios that require long-term storage, such as the long-term storage of food and daily chemical products.

[0009] In summary, the shortcomings of existing label adhesives in terms of "no residue after PET recycling", "high bonding strength compatibility", "environmentally friendly and VOC-free", and "stable use in multiple scenarios" hinder the efficient and high-value recycling of PET bottles and packaging. It is urgent to overcome the limitations of existing technologies and solve the above problems. Summary of the Invention

[0010] The purpose of this invention is to solve the problems existing in the prior art and to provide a polyester hot melt adhesive, its preparation method, and its application in the field of easy-to-peel labels.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A polyester hot melt adhesive, with the following structural formula:

[0013]

[0014] Where R1 is a C2-C6 methylene group; R2 is... R3 is a C1-C4 methylene group. R4 is R5 represents C2 methylene, C3 methylene, C4 methylene, and C6 methylene. R6 is a C4 methylene, C6 methylene,

[0015] The number-average molecular weight of the polyester hot melt adhesive is 20,000–25,000 g / mol; First structural formula: x1 / (x1+y1)=0.4–0.6, y1 / (x1+y1)=0.4–0.6; Second structural formula: x2 / (x2+y2+z1)=0.35–0.52, y2 / (x2+y2+z1)=0.03–0.1, z1 / (x2… +y2+z1)=0.48~0.62; The third structural formula: x3 / (x3+y3+z2+n)=0.585~0.76, y3 / (x3+y3+z2+n)=0.0325~0.08, z2 / (x3+y3+z2+n)=0.18~0.3325, n / (x3+y3+z2+n)=0.01~0.035.

[0016] As a preferred technical solution:

[0017] The polyester hot melt adhesive described above has a tensile shear strength ≥7MPa for PVC sheets and ≥5MPa for PET sheets; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 20-25N / 25mm.

[0018] As described above, the open time of the polyester hot melt adhesive is 90 to 150 seconds. The open time is defined as the length of time from melting to cooling and being usable for bonding. The open time should not be too long or too short.

[0019] The present invention also provides a method for preparing polyester hot melt adhesive, wherein a copolyester with a melting point below 160°C undergoes a crosslinking reaction with a crosslinking agent containing β-thioester bonds in its molecular chain to obtain polyester hot melt adhesive.

[0020] As a preferred technical solution:

[0021] The preparation method of the polyester hot melt adhesive described above, wherein the molecular chain of the copolyester contains carbon-carbon double bonds;

[0022] The chemical structural formula of the crosslinking agent is:

[0023]

[0024] Crosslinking reaction refers to the reaction between the carbon-carbon double bonds of the copolyester and the thiol end groups of the crosslinking agent.

[0025] The method for preparing a polyester hot melt adhesive as described above involves obtaining a copolyester from a diol and a diacid via esterification and polycondensation reactions.

[0026] Among them, the diol includes diol A, which is an aliphatic diol of C2 to C6. If the number of carbon atoms in diol A is greater than 6, then there are too many methylene groups in diol A, resulting in excessive flexibility and a significant impact on the crystallization rate of the copolyester. This causes the open time of the polyester hot melt adhesive to be too long during use, affecting processing.

[0027] Dicarboxylic acids include terephthalic acid and dicarboxylic acid A, which is a dicarboxylic acid with a carbon-carbon double bond.

[0028] In the preparation method of the polyester hot melt adhesive described above, the diol A is ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol.

[0029] Dicarboxylic acid A is maleic acid, itaconic acid, fumaric acid, zeaxanthin, or citraconic acid.

[0030] In the preparation method of the polyester hot melt adhesive described above, diacid A accounts for 40-60% of the total molar amount of diacids. The introduction of diacid A helps to disrupt the regularity of the molecular chain and reduce the crystallization rate and crystallinity of the copolyester. The fact that diacid A accounts for 40-60% of the total molar amount of diacids is beneficial to control the melting point and open time of the copolyester within the range suitable for hot melt adhesives.

[0031] In the preparation method of the polyester hot melt adhesive described above, the diacid also includes diacid B, which accounts for 45-55% of the total molar amount of the diacid, and diacid A accounts for 3-10% of the total molar amount of the diacid. The introduction of diacid B helps to disrupt the regularity of the molecular chain and reduce the crystallization rate and crystallinity of the copolyester. The fact that diacid B accounts for 45-55% of the total molar amount of the diacid is beneficial to control the melting point and open time of the copolyester within a range suitable for hot melt adhesives. The introduction of diacid A, which accounts for 3-10% of the total molar amount of the diacid, can, on the one hand, assist in disrupting the regularity of the molecular chain and reduce the crystallization rate and crystallinity of the copolyester, and on the other hand, introduce carbon-carbon double bonds as reaction sites for crosslinking agents.

[0032] Alternatively, the diol may also include diol B, which accounts for 20-35% of the total molar amount of the diol, and diacid A, which accounts for 5-10% of the total molar amount of the diacid. The introduction of diol B helps to disrupt the regularity of the molecular chain, thereby reducing the crystallization rate and crystallinity of the copolyester. The fact that diol B accounts for 20-35% of the total molar amount of the diol is beneficial for controlling the melting point and open time of the copolyester within a range suitable for hot melt adhesives. The introduction of diacid A, which accounts for 5-10% of the total molar amount of the diacid, can, on the one hand, assist in disrupting the regularity of the molecular chain and reducing the crystallization rate and crystallinity of the copolyester, and on the other hand, introduce carbon-carbon double bonds as reaction sites for crosslinking agents.

[0033] Dicarboxylic acid B is a straight-chain aliphatic dicarboxylic acid of C3 to C6, an aliphatic dicarboxylic acid with a main chain of C3 to C5 and a methyl side group, or a heterocyclic dicarboxylic acid.

[0034] Diol B is a heterocyclic diol;

[0035] When diacid B or diol B is absent from the raw materials, a large amount of diacid A needs to be added to disrupt the regularity of the molecular chain, thereby controlling the crystallization rate and melt viscosity of the copolyester. However, since diacid A contains double bonds, these double bonds are prone to free radical reactions between carbon-carbon double bonds during polymerization. Therefore, stabilizers need to be added to inhibit this reaction. Adding a large amount of diacid A requires adding a large amount of stabilizer, and excessive stabilizer addition will also inhibit the transesterification reaction during polymerization, which is not conducive to the growth of the molecular chain. This results in a low molecular weight of the copolyester, and consequently, low bonding strength of the hot melt adhesive.

[0036] By introducing diacid B or diol B, the amount of diacid A can be reduced, allowing diacid A to primarily function as a linker with the crosslinking agent, thus avoiding excessive use of stabilizer.

[0037] In the preparation method of the polyester hot melt adhesive described above, the diol B is 1,4-cyclohexanediethanol, isosorbide, isomannitol, isoidulol, isoidulose-2,5-diethanol, 2,5-furandiethanol, 2,2-dimethyl-1,3-propanediol, or 2-methyl-1,3-propanediol.

[0038] Dicarboxylic acid B is malonic acid, succinic acid, glutaric acid, adipic acid, methylmalonic acid, methylsuccinic acid, 2,3-dimethylsuccinic acid, 3,3-dimethylglutaric acid, 2,2-dimethylglutaric acid, 2,4-dimethylglutaric acid, furan-2,5-dicarboxylic acid, furan-2,4-dicarboxylic acid, furan-3,4-dicarboxylic acid, or isoturoyl-2,5-dicarboxylic acid.

[0039] The specific preparation steps of the copolyester in the above-described method for preparing a polyester hot melt adhesive are as follows:

[0040] (1) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 210-230℃ and a pressure of 0.1-0.33MPa until the esterification water output reaches 95-98% of the theoretical water output.

[0041] (2) Add a polycondensation catalyst to the reaction system of step (1) and react for 2 to 3 hours at a temperature of 260 to 280°C and a pressure of 60 to 100 Pa to obtain a copolyester.

[0042] In the preparation method of the polyester hot melt adhesive described above, the ratio of the total molar amount of diol to the total molar amount of diacid is 1.1 to 1.5:1; the amount of esterification catalyst added is 100 to 300 ppm of the total molar amount of diacid; the stabilizer is 5 to 15% of the mass of diacid A; and the amount of polycondensation catalyst added is 500 to 1000 ppm of the total molar amount of diacid.

[0043] The esterification catalyst is one or more of tetrabutyl titanate, titanium dioxide, and zinc acetate; the stabilizer is 4-methoxyphenol or methoxyhydroquinone; the polycondensation catalyst is one or more of titanium-based catalysts, antimony-based catalysts, and metal acetates; the titanium-based catalyst is tetrabutyl titanate or isopropyl titanate; the antimony-based catalyst is antimony trioxide; and the metal acetate is one or more of zinc acetate, magnesium acetate, manganese acetate, calcium acetate, sodium acetate, and cobalt acetate.

[0044] The preparation method of the polyester hot melt adhesive as described above is as follows: First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 5 to 10 minutes under ultraviolet light with a wavelength of 350 to 400 nm and a power of 300 W or more. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The amount of crosslinking agent added is 0.5 to 1‰ of the total molar amount of the dibasic acid added when preparing the copolyester.

[0045] Under ultraviolet light, thiols generate sulfur free radicals, which attack the carbon-carbon double bonds of copolyesters to generate thioether products and regenerate a sulfur free radical. This "attack-transfer" cycle repeats continuously, making the reaction highly efficient until the free radicals are exhausted and the reaction stops.

[0046] The preparation method of the polyester hot melt adhesive as described above includes the following specific preparation process: mixing copolyester, crosslinking agent, and thermal initiator, heating to 140-170°C to melt the copolyester, and reacting for 3-10 minutes; wherein, the amount of crosslinking agent added is 0.5-1‰ of the total molar amount of dibasic acid added during the preparation of copolyester; the amount of thermal initiator added is 0.5-3% of the total mass of copolyester and crosslinking agent; the thermal initiator can be benzoyl peroxide or dicumyl peroxide.

[0047] The hot melt adhesive prepared by this method is in a molten state and can be used directly, or it can be allowed to cool and then melted before use.

[0048] The preparation method of the polyester hot melt adhesive as described above, wherein the crosslinking agent is prepared by mixing dithiol, acrylate and photoinitiator in a solvent (tetrahydrofuran), reacting under ultraviolet light with a wavelength of 350-400nm and a power of 300W or higher for 5-15 minutes, and then extracting to obtain the crosslinking agent.

[0049] Under ultraviolet light, the thiol group of the dithiol reacts with the double bond in the acrylate to form a β-thioester bond.

[0050] In the preparation method of the polyester hot melt adhesive described above, the molar ratio of dithiol to acrylate is 2.5 to 3.5:1; the amount of photoinitiator added is 1 to 3% of the total mass of dithiol and acrylate.

[0051] In the preparation method of the polyester hot melt adhesive described above, the dithiol is 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 2,3-butanedithiol or bis(2-mercaptoethyl) ether.

[0052] The acrylate is 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, or dipropylene glycol diacrylate;

[0053] The photoinitiator is α,α-dimethoxy-α-phenylacetophenone or 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetophenone.

[0054] The present invention also provides an application of a polyester hot melt adhesive for adhering a label to a PET bottle using a polyester hot melt adhesive as described in any of the preceding claims.

[0055] As a preferred technical solution:

[0056] The application of polyester hot melt adhesive as described above involves the following steps: heating the polyester hot melt adhesive to melt and then coating it onto a PET bottle, followed by pressing a label onto the polyester hot melt adhesive; or, the specific process involves preparing a polyester hot melt adhesive web and placing it onto a PET bottle, then covering the label onto the polyester hot melt adhesive web and hot-pressing the label. The preparation method of the polyester hot melt adhesive web is existing technology, and the references are CN101240148A and CN101967733A.

[0057] As described in any of the preceding claims, when a label is adhered to a PET bottle, the PET bottle is then immersed in a weak acid solution at a temperature of 70–90°C and a pH of 3–3.5 for 24–36 hours. The label then detaches from the PET bottle, and the polyester hot melt adhesive separates from the label.

[0058] Invention principle:

[0059] This invention uses terephthalic acid and diol A as basic raw materials to prepare polyester, and then introduces diacid A to disrupt the regularity of the polyester, thereby obtaining a low-melting-point copolyester. At the same time, diacid A has carbon-carbon double bonds, while the crosslinking agent has mercapto end groups (the end groups of dithiols are mercapto). The carbon-carbon double bonds of diacid A and the mercapto end groups of the crosslinking agent will undergo a crosslinking reaction under the initiation of ultraviolet light, thereby giving the prepared hot melt adhesive a crosslinked structure. This will result in high cohesive energy and high bonding strength of the hot melt adhesive.

[0060] The crosslinking agent of this invention contains β-thioester bonds, and different copolyester molecular chains are connected by the crosslinking agent. In a weak acid solution with a pH of 3 to 3.5 at 70 to 90°C, the acidic environment can cause the β-thioester bonds in the polyester hot melt adhesive to break, thereby reducing the cohesive force of the polyester hot melt adhesive and reducing the bonding strength. At the same time, the temperature of 70 to 90°C reduces the interfacial forces between the polyester hot melt adhesive and other objects. Therefore, after the label is adhered to the PET bottle with the polyester hot melt adhesive, if the PET bottle is placed in a weak acid solution with a pH of 3 to 3.5 at 70 to 90°C for 24 to 36 hours, the label will fall off the PET bottle, and the polyester hot melt adhesive and the label will separate (the polyester hot melt adhesive is completely peeled off without residue).

[0061] Beneficial effects:

[0062] (1) This invention allows a crosslinking agent containing β-thioester bonds to undergo a crosslinking reaction with copolyester. During the PET recycling stage, the weak acid environment can break the β-thioester bonds, enabling the label to be removed from the PET bottle and the polyester hot melt adhesive to separate from the label. This solves the problem that existing label adhesives are difficult to effectively peel off during PET recycling, leave residues after peeling, or have hot melt adhesive sticking to the label after peeling, resulting in low PET recycling purity and affecting the quality of r-PET.

[0063] (2) In this invention, the copolyester molecular chain contains carbon-carbon double bonds, which react with the mercapto end group of the crosslinking agent to form a crosslinking structure. This crosslinking structure can enhance the cohesive energy of the hot melt adhesive, solving the problem that existing easy-peel hot melt adhesives reduce peel strength in order to achieve easy peeling, resulting in insufficient bonding strength and inability to adapt to high bonding stability requirements.

[0064] (3) When preparing copolyester, the amount of diacid A with carbon-carbon double bonds can be reduced by introducing diacid B or diol B. There is no need to add a large amount of stabilizer, and no small molecule additives such as plasticizers are added in the formula. VOCs are not easily generated during the use of hot melt adhesive, which solves the problem that existing washable hot melt adhesives generate VOCs due to the presence of small molecule additives, which endangers the health of operators.

[0065] (4) This invention obtains a low-melting-point copolyester by adjusting the composition of copolyester raw materials, and achieves label peeling by combining it with a weak acid environment. It does not require high-temperature heating and will not cause PVC and other labels to soften. It can be used for labels of various materials such as PVC. It solves the problem that some existing easy-to-peel hot melt adhesives require high-temperature peeling, are selective for label materials, and can only be used for non-PVC labels, thus limiting their applicability. Attached Figure Description

[0066] Figure 1 The crosslinking agent prepared in Example A1 1 H NMR spectrum;

[0067] Figure 2 The copolyester obtained in Example B9 1 H NMR spectrum. Detailed Implementation

[0068] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0069] The following are the test methods for the relevant performance indicators in each embodiment:

[0070] Melting point: Tested according to GB / T 19466.1-2004 standard, the DSC test temperature is 30-200℃, the heating rate is 10℃ / min, and the test procedure of heating-cooling-reheating is adopted.

[0071] Opening time: Tested according to HG / T 3716-2003 standard.

[0072] Tensile shear strength of polyester hot melt adhesive on PVC or PET sheets: tested according to GB / T 7124-2008 standard.

[0073] After the PVC film is bonded to the PET sheet with polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is tested according to the GB / T2792-1998 standard; the peel angle is 180°.

[0074] The PVC sheet is manufactured by Dongguan Rihui Plastic Products Co., Ltd., with item number 04 and a thickness of 2mm; the PVC film is manufactured by Dongguan Rihui Plastic Products Co., Ltd., with item number 04 and a thickness of 0.2mm; the PET sheet is manufactured by Yangzhou Sanwei New Materials Co., Ltd., with item number PET and a thickness of 2mm.

[0075] Number-average molecular weight: The test was conducted according to the method mentioned in the literature (Synthesis process and properties of long-chain branched PBST copolyester [D]. Zhejiang: Zhejiang University, 2014.).

[0076] The values ​​of x1, y1, x2, y2, z1, x3, y3, z2, and n were calculated according to the method mentioned in the literature (Study on Synthesis and Copolymerization Modification of Bio-based Aromatic Polyesters Based on 2,5-Furfurylic Acid [D]. University of Chinese Academy of Sciences, 2018.).

[0077] In Examples A1 to A6, the general structural formula of the crosslinking agent prepared is as follows:

[0078]

[0079] In Examples C1 to C14, the PET bottle is manufactured by Qingzhou Yihao Plastic Products Co., Ltd., and has a diameter of 30mm; the weak acid solution is an aqueous acetic acid solution; the label is a PVC film (manufacturer: Dongguan Rihui Plastic Products Co., Ltd., item number 04, thickness 0.2mm).

[0080] The specific process of Method 1, which uses polyester hot melt adhesive to adhere a label to a PET bottle, is as follows: The polyester hot melt adhesive is heated to 10°C above its melting point and then applied to the PET bottle; the label is then placed on top of the polyester hot melt adhesive and pressed down. The amount of polyester hot melt adhesive applied is 25 g / m². 2 The pressing pressure is 0.5 MPa, and the holding time is 10 seconds.

[0081] Method 2, which involves attaching labels to PET bottles using polyester hot melt adhesive, involves the following steps: First, a polyester hot melt adhesive web is made and placed on the PET bottle. Then, the label is placed on the polyester hot melt adhesive web, and finally, a hot melt adhesive labeling machine with a hot-pressing function is used to hot-press the label. The amount of polyester hot melt adhesive applied is 25 g / m². 2 The hot-pressing temperature is 10°C above the melting point of the polyester hot melt adhesive, the hot-pressing pressure is 0.5MPa, and the holding time is 10s.

[0082] Example A1

[0083] A method for preparing a crosslinking agent, the specific steps of which are as follows:

[0084] (1) Preparation of materials;

[0085] Dithiols: 1,2-ethanedithiol;

[0086] Acrylates: Dipropylene glycol diacrylate;

[0087] Photoinitiator: α,α-dimethoxy-α-phenylacetophenone;

[0088] Solvent: Tetrahydrofuran;

[0089] (2) Preparation of crosslinking agent;

[0090] Dithiol, acrylate, and photoinitiator were mixed in a solvent and reacted under ultraviolet light with a wavelength of 360 nm and a power of 300 W for 11 min. The crosslinking agent was obtained by extraction. The molar ratio of dithiol to acrylate was 3:1, the mass of the photoinitiator was 3% of the total mass of dithiol and acrylate, and the mass of the solvent was 95% of the total mass of dithiol and acrylate.

[0091] In the final crosslinking agent's structural formula, R5 is a C2 methylene group, and R6 is... Crosslinking agent 1 HNMR spectrum as follows Figure 1 As shown.

[0092] Example A2

[0093] A method for preparing a crosslinking agent, the specific steps of which are as follows:

[0094] (1) Preparation of materials;

[0095] Dithiols: 1,3-propanedithiol;

[0096] Acrylate: 1,6-hexanediol diacrylate;

[0097] Photoinitiator: 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone;

[0098] Solvent: Tetrahydrofuran;

[0099] (2) Preparation of crosslinking agent;

[0100] Dithiol, acrylate, and photoinitiator were mixed in a solvent and reacted under ultraviolet light with a wavelength of 350 nm and a power of 300 W for 5 min. The crosslinking agent was obtained by extraction. The molar ratio of dithiol to acrylate was 2.5:1, the mass of the photoinitiator was 1% of the total mass of dithiol and acrylate, and the mass of the solvent was 90% of the total mass of dithiol and acrylate.

[0101] In the final crosslinking agent, R5 is a C3 methylene group and R6 is a C6 methylene group.

[0102] Example A3

[0103] A method for preparing a crosslinking agent, the specific steps of which are as follows:

[0104] (1) Preparation of materials;

[0105] Dithiols: 1,4-Butanedithiol;

[0106] Acrylates: Neopentyl glycol diacrylate;

[0107] Photoinitiator: 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone;

[0108] Solvent: Tetrahydrofuran;

[0109] (2) Preparation of crosslinking agent;

[0110] Dithiol, acrylate, and photoinitiator were mixed in a solvent and reacted under ultraviolet light with a wavelength of 390 nm and a power of 300 W for 7 min. The crosslinking agent was obtained by extraction. The molar ratio of dithiol to acrylate was 2.5:1, the mass of the photoinitiator was 2% of the total mass of dithiol and acrylate, and the mass of the solvent was 91% of the total mass of dithiol and acrylate.

[0111] In the final crosslinking agent's structural formula, R5 is a C4 methylene group, and R6 is...

[0112] Example A4

[0113] A method for preparing a crosslinking agent, the specific steps of which are as follows:

[0114] (1) Preparation of materials;

[0115] Dithiols: 1,6-hexanedithiol;

[0116] Acrylates: Neopentyl glycol diacrylate;

[0117] Photoinitiator: α,α-dimethoxy-α-phenylacetophenone;

[0118] Solvent: Tetrahydrofuran;

[0119] (2) Preparation of crosslinking agent;

[0120] Dithiol, acrylate, and photoinitiator were mixed in a solvent and reacted under ultraviolet light with a wavelength of 400 nm and a power of 300 W for 13 min. The crosslinking agent was obtained by extraction. The molar ratio of dithiol to acrylate was 2.5:1, the mass of the photoinitiator was 1.5% of the total mass of dithiol and acrylate, and the mass of the solvent was 85% of the total mass of dithiol and acrylate.

[0121] In the final crosslinking agent's structural formula, R5 is a C6 methylene group, and R6 is...

[0122] Example A5

[0123] A method for preparing a crosslinking agent, the specific steps of which are as follows:

[0124] (1) Preparation of materials;

[0125] Dithiols: 2,3-Butanedithiol;

[0126] Acrylate: 1,4-Butanediol diacrylate;

[0127] Photoinitiator: α,α-dimethoxy-α-phenylacetophenone;

[0128] Solvent: Tetrahydrofuran;

[0129] (2) Preparation of crosslinking agent;

[0130] Dithiol, acrylate, and photoinitiator were mixed in a solvent and reacted under ultraviolet light with a wavelength of 370 nm and a power of 300 W for 15 min. The crosslinking agent was obtained by extraction. The molar ratio of dithiol to acrylate was 3.5:1, the mass of the photoinitiator was 3% of the total mass of dithiol and acrylate, and the mass of the solvent was 93% of the total mass of dithiol and acrylate.

[0131] In the final crosslinking agent's structural formula, R5 is... R6 is a C4 methylene group.

[0132] Example A6

[0133] A method for preparing a crosslinking agent, the specific steps of which are as follows:

[0134] (1) Preparation of materials;

[0135] Dithiols: bis(2-mercaptoethyl) ether;

[0136] Acrylate: 1,4-Butanediol diacrylate;

[0137] Photoinitiator: 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylphenylacetone;

[0138] Solvent: Tetrahydrofuran;

[0139] (2) Preparation of crosslinking agent;

[0140] Dithiol, acrylate, and photoinitiator were mixed in a solvent and reacted under ultraviolet light with a wavelength of 380 nm and a power of 300 W for 10 min. The crosslinking agent was obtained by extraction. The molar ratio of dithiol to acrylate was 2.5:1, the mass of the photoinitiator was 2.5% of the total mass of dithiol and acrylate, and the mass of the solvent was 89% of the total mass of dithiol and acrylate.

[0141] In the final crosslinking agent's structural formula, R5 is... R6 is a C4 methylene group.

[0142] Example B1

[0143] A method for preparing a copolyester, comprising the following specific steps:

[0144] (1) Material preparation;

[0145] Diol: Ethylene glycol;

[0146] Dicarboxylic acid: composed of terephthalic acid and maleic acid, with maleic acid accounting for 40% of the total molar amount of terephthalic acid and maleic acid;

[0147] Esterification catalyst: Tetrabutyl titanate;

[0148] Stabilizer: 4-Methoxyphenol;

[0149] Polycondensation catalyst: Tetrabutyl titanate;

[0150] (2) Preparation of copolyester;

[0151] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 215°C and a pressure of 0.15 MPa until the esterification water output reaches 95% of the theoretical water output.

[0152] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2 hours at a temperature of 260°C and a pressure of 60 Pa to obtain a copolyester.

[0153] The molar ratio of diol to diacid is 1.5:1, the molar amount of esterification catalyst is 100 ppm of the molar amount of diacid, the mass of stabilizer is 5% of the mass of maleic acid, and the molar amount of polycondensation catalyst is 500 ppm of the molar amount of diacid.

[0154] The final copolyester has a melting point of 151℃ and can also be used directly as a hot melt adhesive. In this case, the open time of the hot melt adhesive is 97s. The tensile shear strength of the hot melt adhesive on PVC sheets is 6.5MPa and on PET sheets is 4.4MPa. After the PVC film is bonded to the PET sheet with hot melt adhesive, the peel strength of the PVC film to the PET sheet is 19N / 25mm.

[0155] Example B2

[0156] A method for preparing a copolyester, comprising the following specific steps:

[0157] (1) Material preparation;

[0158] Diol: 1,3-propanediol;

[0159] Dicarboxylic acid: composed of terephthalic acid and itaconic acid, with the molar amount of itaconic acid being 45% of the total molar amount of terephthalic acid and itaconic acid;

[0160] Esterification catalyst: Titanium dioxide;

[0161] Stabilizer: 4-Methoxyphenol;

[0162] Polycondensation catalyst: Antimony trioxide;

[0163] (2) Preparation of copolyester;

[0164] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 210°C and a pressure of 0.25 MPa until the esterification water output reaches 96% of the theoretical output.

[0165] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 3 hours at a temperature of 270°C and a pressure of 70 Pa to obtain a copolyester.

[0166] The molar ratio of diol to diacid is 1.3:1, the molar amount of esterification catalyst is 150 ppm of the molar amount of diacid, the mass of stabilizer is 10% of the mass of itaconic acid, and the molar amount of polycondensation catalyst is 1000 ppm of the molar amount of diacid.

[0167] The final copolyester has a melting point of 145℃.

[0168] Example B3

[0169] A method for preparing a copolyester, comprising the following specific steps:

[0170] (1) Material preparation;

[0171] Diol: 1,5-pentanediol;

[0172] Dicarboxylic acid: composed of terephthalic acid and fumaric acid, with the molar amount of fumaric acid being 55% of the total molar amount of terephthalic acid and fumaric acid;

[0173] Esterification catalyst: Tetrabutyl titanate;

[0174] Stabilizer: Methoxyhydroquinone;

[0175] Polycondensation catalyst: manganese acetate;

[0176] (2) Preparation of copolyester;

[0177] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 225°C and a pressure of 0.33 MPa until the esterification water output reaches 96% of the theoretical water output.

[0178] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.5 h at a temperature of 280 °C and a pressure of 90 Pa to obtain a copolyester.

[0179] The molar ratio of diol to diacid is 1.1:1, the molar amount of esterification catalyst is 300 ppm of the molar amount of diacid, the mass of stabilizer is 7% of the mass of fumaric acid, and the molar amount of polycondensation catalyst is 700 ppm of the molar amount of diacid.

[0180] The final copolyester has a melting point of 118℃.

[0181] Example B4

[0182] A method for preparing a copolyester, comprising the following specific steps:

[0183] (1) Material preparation;

[0184] Diol: 1,6-hexanediol;

[0185] Dicarboxylic acid: composed of terephthalic acid and medaconic acid, with the molar amount of medaconic acid being 60% of the total molar amount of terephthalic acid and medaconic acid;

[0186] Esterification catalyst: Zinc acetate;

[0187] Stabilizer: 4-Methoxyphenol;

[0188] Polycondensation catalyst: isopropyl titanate;

[0189] (2) Preparation of copolyester;

[0190] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 220°C and a pressure of 0.3 MPa until the esterification water output reaches 98% of the theoretical output.

[0191] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.1 h at a temperature of 265 °C and a pressure of 100 Pa to obtain a copolyester.

[0192] The molar ratio of diol to diacid is 1.2:1, the molar amount of esterification catalyst is 200 ppm of the molar amount of diacid, the mass of stabilizer is 15% of the mass of diacid, and the molar amount of polycondensation catalyst is 600 ppm of the molar amount of diacid.

[0193] The final copolyester has a melting point of 109℃.

[0194] Example B5

[0195] A method for preparing a copolyester, comprising the following specific steps:

[0196] (1) Material preparation;

[0197] Diol: 1,4-Butanediol;

[0198] Dicarboxylic acid: composed of terephthalic acid and citralic acid, with citralic acid accounting for 50% of the total molar amount of terephthalic acid and citralic acid;

[0199] Esterification catalyst: Titanium dioxide;

[0200] Stabilizer: Methoxyhydroquinone;

[0201] Polycondensation catalyst: Zinc acetate;

[0202] (2) Preparation of copolyester;

[0203] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 230°C and a pressure of 0.2 MPa until the esterification water output reaches 97% of the theoretical output.

[0204] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.7 h at a temperature of 275 °C and a pressure of 80 Pa to obtain a copolyester.

[0205] The molar ratio of diol to diacid is 1.4:1, the molar amount of esterification catalyst is 250 ppm of the molar amount of diacid, the mass of stabilizer is 11% of the mass of citralic acid, and the molar amount of polycondensation catalyst is 800 ppm of the molar amount of diacid.

[0206] The final copolyester has a melting point of 125℃.

[0207] Example B6

[0208] A method for preparing a copolyester, comprising the following specific steps:

[0209] (1) Material preparation;

[0210] Diol: Ethylene glycol;

[0211] Dicarboxylic acid: Composed of terephthalic acid, maleic acid and malonic acid, with maleic acid accounting for 3% of the total molar amount of terephthalic acid, maleic acid and malonic acid, and malonic acid accounting for 55% of the total molar amount of terephthalic acid, maleic acid and malonic acid.

[0212] Esterification catalyst: Tetrabutyl titanate;

[0213] Stabilizer: 4-Methoxyphenol;

[0214] Polycondensation catalyst: Zinc acetate;

[0215] (2) Preparation of copolyester;

[0216] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 230°C and a pressure of 0.1 MPa until the esterification water output reaches 95% of the theoretical output.

[0217] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2 hours at a temperature of 260°C and a pressure of 60 Pa to obtain a copolyester.

[0218] The molar ratio of diol to diacid is 1.5:1, the molar amount of esterification catalyst is 100 ppm of the molar amount of diacid, the mass of stabilizer is 5% of the mass of maleic acid, and the molar amount of polycondensation catalyst is 500 ppm of the molar amount of diacid.

[0219] The final copolyester has a melting point of 130℃.

[0220] Example B7

[0221] A method for preparing a copolyester, comprising the following specific steps:

[0222] (1) Material preparation;

[0223] Diol: 1,3-propanediol;

[0224] Dicarboxylic acid: Composed of terephthalic acid, itaconic acid and succinic acid, with itaconic acid accounting for 9% of the total molar amount of terephthalic acid, itaconic acid and succinic acid, and succinic acid accounting for 50% of the total molar amount of terephthalic acid, itaconic acid and succinic acid.

[0225] Esterification catalyst: Titanium dioxide;

[0226] Stabilizer: 4-Methoxyphenol;

[0227] Polycondensation catalyst: isopropyl titanate;

[0228] (2) Preparation of copolyester;

[0229] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 215°C and a pressure of 0.2 MPa until the esterification water output reaches 96% of the theoretical water output.

[0230] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 3 hours at a temperature of 270°C and a pressure of 70 Pa to obtain a copolyester.

[0231] The molar ratio of diol to diacid is 1.3:1, the molar amount of esterification catalyst is 200 ppm of the molar amount of diacid, the mass of stabilizer is 15% of the mass of itaconic acid, and the molar amount of polycondensation catalyst is 700 ppm of the molar amount of diacid.

[0232] The final copolyester has a melting point of 135℃.

[0233] Example B8

[0234] A method for preparing a copolyester, comprising the following specific steps:

[0235] (1) Material preparation;

[0236] Diol: 1,5-pentanediol;

[0237] Dicarboxylic acid: Composed of terephthalic acid, fumaric acid and methylmalonic acid, with the molar amount of fumaric acid being 10% of the total molar amount of terephthalic acid, fumaric acid and methylmalonic acid, and the molar amount of methylmalonic acid being 52% of the total molar amount of terephthalic acid, fumaric acid and methylmalonic acid.

[0238] Esterification catalyst: Zinc acetate;

[0239] Stabilizer: Methoxyhydroquinone;

[0240] Polycondensation catalyst: calcium acetate;

[0241] (2) Preparation of copolyester;

[0242] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 220°C and a pressure of 0.15 MPa until the esterification water output reaches 98% of the theoretical water output.

[0243] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.5 h at a temperature of 275 °C and a pressure of 80 Pa to obtain a copolyester.

[0244] The molar ratio of diol to diacid is 1.1:1, the molar amount of esterification catalyst is 300 ppm of the molar amount of diacid, the mass of stabilizer is 7% of the mass of fumaric acid, and the molar amount of polycondensation catalyst is 600 ppm of the molar amount of diacid.

[0245] The final copolyester has a melting point of 123℃.

[0246] Example B9

[0247] A method for preparing a copolyester, comprising the following specific steps:

[0248] (1) Material preparation;

[0249] Diol: 1,4-Butanediol;

[0250] Dicarboxylic acid: composed of terephthalic acid, itaconic acid and adipic acid, with the molar amount of itaconic acid being 5% of the total molar amount of terephthalic acid, itaconic acid and adipic acid, and the molar amount of adipic acid being 45% of the total molar amount of terephthalic acid, itaconic acid and adipic acid;

[0251] Esterification catalyst: Tetrabutyl titanate;

[0252] Stabilizer: Methoxyhydroquinone;

[0253] Polycondensation catalyst: Antimony trioxide;

[0254] (2) Preparation of copolyester;

[0255] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 210°C and a pressure of 0.3 MPa until the esterification water output reaches 98% of the theoretical output.

[0256] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 3 hours at a temperature of 265°C and a pressure of 100 Pa to obtain a copolyester.

[0257] The molar ratio of diol to diacid is 1.2:1, the molar amount of esterification catalyst is 250 ppm of the molar amount of diacid, the mass of stabilizer is 10% of the mass of diacid, and the molar amount of polycondensation catalyst is 700 ppm of the molar amount of diacid.

[0258] The final copolyester has a melting point of 127℃, such as Figure 2 The image shows the nuclear magnetic resonance spectrum of the prepared copolyester.

[0259] Example B10

[0260] A method for preparing a copolyester, comprising the following specific steps:

[0261] (1) Material preparation;

[0262] Diol: 1,6-hexanediol;

[0263] Dicarboxylic acid: Composed of terephthalic acid, citralic acid and glutaric acid, with citralic acid accounting for 7% of the total molar amount of terephthalic acid, citralic acid and glutaric acid, and glutaric acid accounting for 47% of the total molar amount of terephthalic acid, citralic acid and glutaric acid.

[0264] Esterification catalyst: Zinc acetate;

[0265] Stabilizer: 4-Methoxyphenol;

[0266] Polycondensation catalyst: Tetrabutyl titanate;

[0267] (2) Preparation of copolyester;

[0268] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 225°C and a pressure of 0.33 MPa until the esterification water output reaches 97% of the theoretical output.

[0269] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.7 h at a temperature of 280 °C and a pressure of 65 Pa to obtain a copolyester.

[0270] The molar ratio of diol to diacid is 1.4:1, the molar amount of esterification catalyst is 150 ppm of the molar amount of diacid, the mass of stabilizer is 11% of the mass of citralic acid, and the molar amount of polycondensation catalyst is 1000 ppm of the molar amount of diacid.

[0271] The final copolyester has a melting point of 137°C.

[0272] Example B11

[0273] A method for preparing a copolyester, comprising the following specific steps:

[0274] (1) Material preparation;

[0275] Diol: Composed of ethylene glycol and 1,4-cyclohexanediethanol, wherein the molar amount of 1,4-cyclohexanediethanol is 35% of the total molar amount of ethylene glycol and 1,4-cyclohexanediethanol.

[0276] Dicarboxylic acid: composed of terephthalic acid and maleic acid, with the molar amount of maleic acid being 10% of the total molar amount of terephthalic acid and maleic acid;

[0277] Esterification catalyst: Tetrabutyl titanate;

[0278] Stabilizer: 4-Methoxyphenol;

[0279] Polycondensation catalyst: Antimony trioxide;

[0280] (2) Preparation of copolyester;

[0281] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 210°C and a pressure of 0.2 MPa until the esterification water output reaches 95% of the theoretical output.

[0282] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2 hours at a temperature of 260°C and a pressure of 60 Pa to obtain a copolyester.

[0283] The molar ratio of diol to diacid is 1.1:1, the molar amount of esterification catalyst is 100 ppm of the molar amount of diacid, the mass of stabilizer is 5% of the mass of maleic acid, and the molar amount of polycondensation catalyst is 500 ppm of the molar amount of diacid.

[0284] The final copolyester has a melting point of 150°C.

[0285] Example B12

[0286] A method for preparing a copolyester, comprising the following specific steps:

[0287] (1) Material preparation;

[0288] Diol: Composed of 1,3-propanediol and isosorbide, with the molar amount of isosorbide being 23% of the total molar amount of 1,3-propanediol and isosorbide;

[0289] Dicarboxylic acid: composed of terephthalic acid and citralic acid, with citralic acid accounting for 8% of the total molar amount of terephthalic acid and citralic acid;

[0290] Esterification catalyst: Titanium dioxide;

[0291] Stabilizer: 4-Methoxyphenol;

[0292] Polycondensation catalyst: Tetrabutyl titanate;

[0293] (2) Preparation of copolyester;

[0294] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 225°C and a pressure of 0.33 MPa until the esterification water output reaches 95% of the theoretical output.

[0295] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 3 hours at a temperature of 275°C and a pressure of 65 Pa to obtain a copolyester.

[0296] The molar ratio of diol to diacid is 1.2:1, the molar amount of esterification catalyst is 170 ppm of the molar amount of diacid, the mass of stabilizer is 7.5% of the mass of citralic acid, and the molar amount of polycondensation catalyst is 900 ppm of the molar amount of diacid.

[0297] The final copolyester has a melting point of 145℃.

[0298] Example B13

[0299] A method for preparing a copolyester, comprising the following specific steps:

[0300] (1) Material preparation;

[0301] Diol: Composed of 1,4-butanediol and isomannitol, with the molar amount of isomannitol being 20% ​​of the total molar amount of 1,4-butanediol and isomannitol;

[0302] Dicarboxylic acid: composed of terephthalic acid and itaconic acid, with the molar amount of itaconic acid being 7% of the total molar amount of terephthalic acid and itaconic acid;

[0303] Esterification catalyst: Zinc acetate;

[0304] Stabilizer: 4-Methoxyphenol;

[0305] Polycondensation catalyst: isopropyl titanate;

[0306] (2) Preparation of copolyester;

[0307] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 230°C and a pressure of 0.3 MPa until the esterification water output reaches 98% of the theoretical output.

[0308] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.5 h at a temperature of 270 °C and a pressure of 100 Pa to obtain a copolyester.

[0309] The molar ratio of diol to diacid is 1.3:1, the molar amount of esterification catalyst is 300 ppm of the molar amount of diacid, the mass of stabilizer is 8% of the mass of itaconic acid, and the molar amount of polycondensation catalyst is 700 ppm of the molar amount of diacid.

[0310] The final copolyester has a melting point of 140℃.

[0311] Example B14

[0312] A method for preparing a copolyester, comprising the following specific steps:

[0313] (1) Material preparation;

[0314] Diol: Composed of 1,5-pentanediol and isoadiol, with the molar amount of isoadiol being 30% of the total molar amount of 1,5-pentanediol and isoadiol;

[0315] Dicarboxylic acid: composed of terephthalic acid and fumaric acid, with the molar amount of fumaric acid being 5% of the total molar amount of terephthalic acid and fumaric acid;

[0316] Esterification catalyst: Tetrabutyl titanate;

[0317] Stabilizer: Methoxyhydroquinone;

[0318] Polycondensation catalyst: Zinc acetate;

[0319] (2) Preparation of copolyester;

[0320] (a) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 220°C and a pressure of 0.1 MPa until the esterification water output reaches 99% of the theoretical water output.

[0321] (b) Add a polycondensation catalyst to the reaction system of step (a) and react for 2.2 h at a temperature of 280 °C and a pressure of 70 Pa to obtain a copolyester;

[0322] The molar ratio of diol to diacid is 1.5:1, the molar amount of esterification catalyst is 200 ppm of the molar amount of diacid, the mass of stabilizer is 11.5% of the mass of fumaric acid, and the molar amount of polycondensation catalyst is 1000 ppm of the molar amount of diacid.

[0323] The final copolyester has a melting point of 135℃.

[0324] Example C1

[0325] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0326] (1) Material preparation;

[0327] Copolyester: prepared from Example B1;

[0328] Organic solvent: chloroform;

[0329] Crosslinking agent: prepared from Example A1;

[0330] (2) Preparation of polyester hot melt adhesive;

[0331] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 10 minutes under ultraviolet light with a wavelength of 350 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 0.5‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B1, and the mass of the copolyester is 50% of the mass of the organic solvent.

[0332] The final structure of the polyester hot melt adhesive is as follows:

[0333]

[0334] The number-average molecular weight of the polyester hot melt adhesive is 21000 g / mol, x1 / (x1+y1)=0.59, and y1 / (x1+y1)=0.41.

[0335] The open time of the prepared polyester hot melt adhesive is 95s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7MPa, and the tensile shear strength on PET sheets is 5MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 21N / 25mm.

[0336] After the label was adhered to the PET bottle using method 1 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 70°C and pH 3.2 for 30 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0337] After adhering the label to a PET bottle using the copolyester of Example B1 via Method 1, the PET bottle was immersed in a weakly acidic solution at 70°C and pH 3.2 for 30 hours. The label detached from the PET bottle. However, the adhesive strength of the copolyester of Example B1 was relatively low, making it unsuitable for label applications. The reason for the lower adhesive strength compared to Example C1 is that the copolyester molecular chains in the polyester hot melt adhesive of Example C1 are linked by a crosslinking agent, which improves the adhesive strength. Furthermore, due to the presence of β-thioester bonds in the crosslinking agent, the acidic environment can cause the β-thioester bonds in the polyester hot melt adhesive to break, thereby reducing the cohesive force of the polyester hot melt adhesive and lowering the adhesive strength. Therefore, after adhering the label to the PET bottle using the polyester hot melt adhesive of Example C1, immersing the PET bottle in a weakly acidic solution at 70°C and pH 3.2 for 30 hours resulted in the label detaching from the PET bottle and the separation of the polyester hot melt adhesive from the label.

[0338] Comparative Example 1

[0339] A method for preparing a polyester hot melt adhesive is basically the same as in Example C1, except that in step (2), ultraviolet light irradiation is not performed, but stirring is performed at a speed of 200 r / min for 10 minutes.

[0340] The obtained polyester hot melt adhesive is a mixture of the copolyester obtained in Example B1 and the crosslinking agent obtained in Example A1.

[0341] The open time of the prepared polyester hot melt adhesive is 102s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 6.2MPa, and the tensile shear strength on PET sheets is 4.2MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 17N / 25mm.

[0342] Compared with Example C1, the crosslinking agent in Comparative Example 1 did not react with the double bonds in the copolyester molecular chain, thus failing to produce a crosslinked structure. It played a plasticizing role in the polyester hot melt adhesive, affecting the crystallization of the hot melt adhesive and reducing the cohesive force of the polyester hot melt adhesive, thereby resulting in lower bonding strength.

[0343] Example C2

[0344] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0345] (1) Material preparation;

[0346] Copolyester: prepared from Example B2;

[0347] Organic solvent: hexafluoroisopropanol;

[0348] Crosslinking agent: prepared from Example A3;

[0349] (2) Preparation of polyester hot melt adhesive;

[0350] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 5 minutes under ultraviolet light with a wavelength of 360 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 0.7‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B2, and the mass of the copolyester is 70% of the mass of the organic solvent.

[0351] The final structure of the polyester hot melt adhesive is as follows:

[0352]

[0353] The number-average molecular weight of the polyester hot melt adhesive is 22000 g / mol, x1 / (x1+y1)=0.56, and y1 / (x1+y1)=0.44.

[0354] The open time of the prepared polyester hot melt adhesive is 115s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7.2MPa, and the tensile shear strength on PET sheets is 5.5MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 21.5N / 25mm.

[0355] After the label was adhered to the PET bottle using method 1 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 80°C and pH 3 for 36 hours. The label detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0356] Example C3

[0357] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0358] (1) Material preparation;

[0359] Copolyester: prepared from Example B3;

[0360] Organic solvent: dichloromethane;

[0361] Crosslinking agent: prepared from Example A5;

[0362] (2) Preparation of polyester hot melt adhesive;

[0363] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 5 minutes under ultraviolet light with a wavelength of 370 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 0.8‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B3, and the mass of the copolyester is 60% of the mass of the organic solvent.

[0364] The final structure of the polyester hot melt adhesive is as follows:

[0365]

[0366] The number-average molecular weight of the polyester hot melt adhesive is 20000 g / mol, x1 / (x1+y1)=0.47, and y1 / (x1+y1)=0.53.

[0367] The open time of the prepared polyester hot melt adhesive is 125s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 8MPa, and the tensile shear strength on PET sheets is 7.1MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 22N / 25mm.

[0368] After the label was adhered to the PET bottle using method 2 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 85°C and pH 3.2 for 28 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0369] Example C4

[0370] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0371] (1) Material preparation;

[0372] Copolyester: prepared from Example B4;

[0373] Organic solvent: chloroform;

[0374] Crosslinking agent: prepared from Example A4;

[0375] (2) Preparation of polyester hot melt adhesive;

[0376] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 6 minutes under ultraviolet light with a wavelength of 380 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 1‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B4, and the mass of the copolyester is 80% of the mass of the organic solvent.

[0377] The final structure of the polyester hot melt adhesive is as follows:

[0378]

[0379] The number-average molecular weight of the polyester hot melt adhesive is 22000 g / mol, x1 / (x1+y1)=0.43, and y1 / (x1+y1)=0.57.

[0380] The open time of the prepared polyester hot melt adhesive is 150s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7.5MPa, and the tensile shear strength on PET sheets is 6.5MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 22.3N / 25mm.

[0381] After the label was adhered to the PET bottle using method 2 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 90°C and pH 3 for 33 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0382] Example C5

[0383] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0384] (1) Material preparation;

[0385] Copolyester: prepared from Example B5;

[0386] Organic solvent: dichloromethane;

[0387] Crosslinking agent: prepared from Example A6;

[0388] (2) Preparation of polyester hot melt adhesive;

[0389] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 7 minutes under ultraviolet light with a wavelength of 400 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 0.8‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B5, and the mass of the copolyester is 75% of the mass of the organic solvent.

[0390] The final structure of the polyester hot melt adhesive is as follows:

[0391]

[0392] The number-average molecular weight of the polyester hot melt adhesive is 25000 g / mol, x1 / (x1+y1)=0.54, and y1 / (x1+y1)=0.46.

[0393] The open time of the prepared polyester hot melt adhesive is 100s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 8.2MPa, and the tensile shear strength on PET sheets is 7.1MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 25N / 25mm.

[0394] After the label was adhered to the PET bottle using method 2 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 78°C and pH 3.5 for 24 hours. The label detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0395] Example C6

[0396] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0397] (1) Material preparation;

[0398] Copolyester: prepared from Example B6;

[0399] Organic solvent: chloroform;

[0400] Crosslinking agent: prepared from Example A5;

[0401] (2) Preparation of polyester hot melt adhesive;

[0402] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 6 minutes under ultraviolet light with a wavelength of 360 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 0.6‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B6, and the mass of the copolyester is 65% of the mass of the organic solvent.

[0403] The final structure of the polyester hot melt adhesive is as follows:

[0404]

[0405] The number-average molecular weight of the polyester hot melt adhesive is 21000 g / mol, x2 / (x2+y2+z1)=0.41, y2 / (x2+y2+z1)=0.02, and z1 / (x2+y2+z1)=0.57.

[0406] The open time of the prepared polyester hot melt adhesive is 90s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7.8MPa, and the tensile shear strength on PET sheets is 5.5MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 22.8N / 25mm.

[0407] After the label is adhered to the PET bottle with polyester hot melt adhesive, the PET bottle is immersed in a weak acid solution at 80°C and pH 3.1 for 34 hours. The label then detaches from the PET bottle, and the polyester hot melt adhesive separates from the label.

[0408] Example C7

[0409] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0410] (1) Material preparation;

[0411] Copolyester: prepared from Example B7;

[0412] Organic solvent: hexafluoroisopropanol;

[0413] Crosslinking agent: prepared from Example A2;

[0414] (2) Preparation of polyester hot melt adhesive;

[0415] First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 8 minutes under ultraviolet light with a wavelength of 370 nm and a power of 300 W. Finally, the organic solvent is removed under reduced pressure to obtain the polyester hot melt adhesive. The molar amount of the crosslinking agent is 0.5‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B7, and the mass of the copolyester is 55% of the mass of the organic solvent.

[0416] The final structure of the polyester hot melt adhesive is as follows:

[0417]

[0418] The number-average molecular weight of the polyester hot melt adhesive is 23000 g / mol, x2 / (x2+y2+z1)=0.39, y2 / (x2+y2+z1)=0.08, and z1 / (x2+y2+z1)=0.53.

[0419] The open time of the prepared polyester hot melt adhesive is 130s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7.8MPa, and the tensile shear strength on PET sheets is 6MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 22.1N / 25mm.

[0420] After the label is adhered to the PET bottle using polyester, the PET bottle is immersed in a weak acid solution at 75°C and pH 3.4 for 26 hours. The label then detaches from the PET bottle, and the polyester hot melt adhesive separates from the label.

[0421] Example C8

[0422] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0423] (1) Material preparation;

[0424] Copolyester: prepared from Example B8;

[0425] Thermal initiator: benzoyl peroxide;

[0426] Crosslinking agent: prepared from Example A1;

[0427] (2) Preparation of polyester hot melt adhesive;

[0428] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 140°C for 10 minutes. The amount of crosslinking agent added was 0.5‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B8. The amount of thermal initiator added was 0.5% of the total mass of the copolyester and crosslinking agent.

[0429] The final structure of the polyester hot melt adhesive is as follows:

[0430]

[0431] The number-average molecular weight of the polyester hot melt adhesive is 24000 g / mol, x2 / (x2+y2+z1)=0.38, y2 / (x2+y2+z1)=0.08, and z1 / (x2+y2+z1)=0.54.

[0432] The open time of the prepared polyester hot melt adhesive is 125s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 8MPa, and the tensile shear strength on PET sheets is 7MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 23.7N / 25mm.

[0433] After the label was adhered to the PET bottle using method 2 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 70°C and pH 3.5 for 36 hours. The label detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0434] Example C9

[0435] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0436] (1) Material preparation;

[0437] Copolyester: prepared from Example B9;

[0438] Thermal initiator: dicumyl peroxide;

[0439] Crosslinking agent: prepared from Example A6;

[0440] (2) Preparation of polyester hot melt adhesive;

[0441] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 160°C for 7 minutes. The amount of crosslinking agent added was 0.8‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B9. The amount of thermal initiator added was 0.9% of the total mass of the copolyester and crosslinking agent.

[0442] The final structure of the polyester hot melt adhesive is as follows:

[0443]

[0444] The number-average molecular weight of the polyester hot melt adhesive is 22000 g / mol, x2 / (x2+y2+z1)=0.49, y2 / (x2+y2+z1)=0.03, and z1 / (x2+y2+z1)=0.48.

[0445] The open time of the prepared polyester hot melt adhesive is 130s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7MPa and the tensile shear strength on PET sheets is 5MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 22.5N / 25mm.

[0446] After the label was adhered to the PET bottle using method 2 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 78°C and pH 3.1 for 32 hours. The label detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0447] Example C10

[0448] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0449] (1) Material preparation;

[0450] Copolyester: prepared from Example B10;

[0451] Thermal initiator: dicumyl peroxide;

[0452] Crosslinking agent: prepared from Example A1;

[0453] (2) Preparation of polyester hot melt adhesive;

[0454] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 165°C for 5 minutes. The amount of crosslinking agent added was 0.7‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B10. The amount of thermal initiator added was 2.5% of the total mass of the copolyester and crosslinking agent.

[0455] The final structure of the polyester hot melt adhesive is as follows:

[0456]

[0457] The number-average molecular weight of the polyester hot melt adhesive is 20000 g / mol, x2 / (x2+y2+z1)=0.46, y2 / (x2+y2+z1)=0.05, and z1 / (x2+y2+z1)=0.49.

[0458] The open time of the prepared polyester hot melt adhesive is 150s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7MPa, and the tensile shear strength on PET sheets is 5MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 20N / 25mm.

[0459] After the label was adhered to the PET bottle using method 2 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 75°C and pH 3.2 for 33 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0460] Example C11

[0461] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0462] (1) Material preparation;

[0463] Copolyester: prepared from Example B11;

[0464] Thermal initiator: dicumyl peroxide;

[0465] Crosslinking agent: prepared from Example A4;

[0466] (2) Preparation of polyester hot melt adhesive;

[0467] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 170°C for 3 minutes. The amount of crosslinking agent added was 0.9‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B11. The amount of thermal initiator added was 3% of the total mass of the copolyester and crosslinking agent.

[0468] The final structure of the polyester hot melt adhesive is as follows:

[0469]

[0470] The number-average molecular weight of the polyester hot melt adhesive is 25000 g / mol, x3 / (x3+y3+z2+n)=0.59, y3 / (x3+y3+z2+n)=0.07, z2 / (x3+y3+z2+n)=0.32, and n / (x3+y3+z2+n)=0.02.

[0471] The final polyester hot melt adhesive has an open time of 90s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 8MPa, and the tensile shear strength on PET sheets is 6.2MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 24.4N / 25mm.

[0472] After the label was adhered to the PET bottle using method 1 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 90°C and pH 3 for 24 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0473] Example C12

[0474] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0475] (1) Material preparation;

[0476] Copolyester: prepared from Example B12;

[0477] Thermal initiator: benzoyl peroxide;

[0478] Crosslinking agent: prepared from Example A5;

[0479] (2) Preparation of polyester hot melt adhesive;

[0480] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 163°C for 6 minutes. The amount of crosslinking agent added was 1‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B12. The amount of thermal initiator added was 2% of the total mass of the copolyester and crosslinking agent.

[0481] The final structure of the polyester hot melt adhesive is as follows:

[0482]

[0483] The number-average molecular weight of the polyester hot melt adhesive is 23000 g / mol, x3 / (x3+y3+z2+n)=0.72, y3 / (x3+y3+z2+n)=0.07, z2 / (x3+y3+z2+n)=0.19, and n / (x3+y3+z2+n)=0.02.

[0484] The open time of the prepared polyester hot melt adhesive is 100s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7.9MPa, and the tensile shear strength on PET sheets is 6MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 23.5N / 25mm.

[0485] After the label was adhered to the PET bottle using method 1 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 85°C and pH 3.3 for 26 hours. The label detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0486] Example C13

[0487] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0488] (1) Material preparation;

[0489] Copolyester: prepared from Example B13;

[0490] Thermal initiator: benzoyl peroxide;

[0491] Crosslinking agent: prepared from Example A3;

[0492] (2) Preparation of polyester hot melt adhesive;

[0493] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 160°C for 7 minutes. The amount of crosslinking agent added was 0.6‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B13. The amount of thermal initiator added was 1.5% of the total mass of the copolyester and crosslinking agent.

[0494] The final structure of the polyester hot melt adhesive is as follows:

[0495]

[0496] Among them, the number-average molecular weight of the polyester hot melt adhesive is 24000 g / mol, x3 / (x3+y3+z2+n)=0.76, y3 / (x3+y3+z2+n)=0.07, z2 / (x3+y3+z2+n)=0.16, and n / (x3+y3+z2+n)=0.01.

[0497] The open time of the prepared polyester hot melt adhesive is 110s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 8.1MPa, and the tensile shear strength on PET sheets is 6.1MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 25N / 25mm.

[0498] After the label was adhered to the PET bottle using method 1 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 82°C and pH 3.4 for 30 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

[0499] Example C14

[0500] A method for preparing a polyester hot melt adhesive, the specific steps of which are as follows:

[0501] (1) Material preparation;

[0502] Copolyester: prepared from Example B14;

[0503] Thermal initiator: dicumyl peroxide;

[0504] Crosslinking agent: prepared from Example A2;

[0505] (2) Preparation of polyester hot melt adhesive;

[0506] The copolyester, crosslinking agent, and thermal initiator were mixed and heated to 155°C for 8 minutes. The amount of crosslinking agent added was 0.65‰ of the molar amount of the dibasic acid added when preparing the copolyester of Example B14. The amount of thermal initiator added was 1.7% of the total mass of the copolyester and crosslinking agent.

[0507] The final structure of the polyester hot melt adhesive is as follows:

[0508]

[0509] The number-average molecular weight of the polyester hot melt adhesive is 22000 g / mol, x3 / (x3+y3+z2+n)=0.7, y3 / (x3+y3+z2+n)=0.08, z2 / (x3+y3+z2+n)=0.21, and n / (x3+y3+z2+n)=0.01.

[0510] The open time of the prepared polyester hot melt adhesive is 132s; the tensile shear strength of the polyester hot melt adhesive on PVC sheets is 7.5MPa, and the tensile shear strength on PET sheets is 5.8MPa; after the PVC film is bonded to the PET sheet with the polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 24N / 25mm.

[0511] After the label was adhered to the PET bottle using method 1 with polyester hot melt adhesive, the PET bottle was immersed in a weak acid solution at 80°C and pH 3.5 for 27 hours. The label then detached from the PET bottle, and the polyester hot melt adhesive separated from the label.

Claims

1. A polyester hot melt adhesive, characterized in that, The structural formula is: Wherein, R1 is a C2-C6 methylene group; R2 is... R3 is a C1-C4 methylene group. R4 is R5 represents C2 methylene, C3 methylene, C4 methylene, and C6 methylene. R6 is a C4 methylene, C6 methylene, The number-average molecular weight of the polyester hot melt adhesive is 20,000–25,000 g / mol; the value of x1 / (x1+y1) ranges from 0.4 to 0.

6. The range of x² / (x²+y²+z₁) is 0.35 to 0.52, and the range of y² / (x²+y²+z₁) is 0.03 to 0.

1. The values ​​of x³ / (x³+y³+z²+n) range from 0.585 to 0.76, the values ​​of y³ / (x³+y³+z²+n) range from 0.0325 to 0.08, and the values ​​of z² / (x³+y³+z²+n) range from 0.18 to 0.3325.

2. The polyester hot melt adhesive according to claim 1, characterized in that, The tensile shear strength of polyester hot melt adhesive on PVC sheets is ≥7MPa, and the tensile shear strength on PET sheets is ≥5MPa; after the PVC film is bonded to the PET sheet with polyester hot melt adhesive, the peel strength of the PVC film to the PET sheet is 20~25N / 25mm.

3. The polyester hot melt adhesive according to claim 1, characterized in that, The open time of polyester hot melt adhesive is 90–150 seconds.

4. A method for preparing the polyester hot melt adhesive according to any one of claims 1 to 3, characterized in that, A copolyester with a melting point controlled below 160℃ undergoes a crosslinking reaction with a crosslinking agent containing β-thioester bonds in its molecular chain to obtain a polyester hot melt adhesive.

5. The method for preparing a polyester hot melt adhesive according to claim 4, characterized in that, The molecular chain of copolyester contains carbon-carbon double bonds; The chemical structural formula of the crosslinking agent is: Crosslinking reaction refers to the reaction between the carbon-carbon double bonds of the copolyester and the thiol end groups of the crosslinking agent.

6. The method for preparing a polyester hot melt adhesive according to claim 5, characterized in that, Copolyesters are prepared by esterification and polycondensation of diols and diacids; Among them, the diol includes diol A, which is an aliphatic diol of C2 to C6. Dicarboxylic acids include terephthalic acid and dicarboxylic acid A, which is a dicarboxylic acid with a carbon-carbon double bond.

7. The method for preparing a polyester hot melt adhesive according to claim 6, characterized in that, Diol A is ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, or 1,6-hexanediol; Dicarboxylic acid A is maleic acid, itaconic acid, fumaric acid, zeaxanthin, or citraconic acid.

8. The method for preparing a polyester hot melt adhesive according to claim 6, characterized in that, Dicarboxylic acid A accounts for 40-60% of the total molar amount of dicarboxylic acids.

9. The method for preparing a polyester hot melt adhesive according to claim 6, characterized in that, Dicarboxylic acids also include dicarboxylic acid B, which accounts for 45-55% of the total molar amount of dicarboxylic acids, while dicarboxylic acid A accounts for 3-10% of the total molar amount of dicarboxylic acids. Alternatively, the diol may also include diol B, which accounts for 20-35% of the total molar amount of the diol, and diacid A accounts for 5-10% of the total molar amount of the diacid. Dicarboxylic acid B is a straight-chain aliphatic dicarboxylic acid of C3 to C6, an aliphatic dicarboxylic acid with a main chain of C3 to C5 and a methyl side group, or a heterocyclic dicarboxylic acid. Diol B is a heterocyclic diol.

10. A method for preparing a polyester hot melt adhesive according to claim 9, characterized in that, Diol B is 1,4-cyclohexanediethanol, isosorbide, isomannitol, isoidulol, isoidulose-2,5-diethanol, 2,5-furandiethanol, 2,2-dimethyl-1,3-propanediol, or 2-methyl-1,3-propanediol. Dicarboxylic acid B is malonic acid, succinic acid, glutaric acid, adipic acid, methylmalonic acid, methylsuccinic acid, 2,3-dimethylsuccinic acid, 3,3-dimethylglutaric acid, 2,2-dimethylglutaric acid, 2,4-dimethylglutaric acid, furan-2,5-dicarboxylic acid, furan-2,4-dicarboxylic acid, furan-3,4-dicarboxylic acid, or isoturoyl-2,5-dicarboxylic acid.

11. A method for preparing a polyester hot melt adhesive according to claim 6, characterized in that, The specific preparation steps of copolyester are as follows: (1) Add the dicarboxylic acid, diol, esterification catalyst and stabilizer into the reactor and react at a temperature of 210-230℃ and a pressure of 0.1-0.33MPa until the esterification water output reaches 95-98% of the theoretical water output. (2) Add a polycondensation catalyst to the reaction system of step (1) and react for 2 to 3 hours at a temperature of 260 to 280°C and a pressure of 60 to 100 Pa to obtain a copolyester.

12. The method for preparing a polyester hot melt adhesive according to claim 11, characterized in that, The ratio of the total molar amount of diol to the total molar amount of diacid is 1.1 to 1.5:1; the amount of esterification catalyst added is 100 to 300 ppm of the total molar amount of diacid; the stabilizer is 5 to 15% of the mass of diacid A; and the amount of polycondensation catalyst added is 500 to 1000 ppm of the total molar amount of diacid. The esterification catalyst is one or more of tetrabutyl titanate, titanium dioxide, and zinc acetate; the stabilizer is 4-methoxyphenol or methoxyhydroquinone; and the polycondensation catalyst is one or more of titanium-based catalysts, antimony-based catalysts, and metal acetates.

13. The method for preparing a polyester hot melt adhesive according to claim 5, characterized in that, The specific preparation process of polyester hot melt adhesive is as follows: First, the copolyester is dissolved in an organic solvent, then a crosslinking agent is added, and the reaction is carried out for 5 to 10 minutes under ultraviolet light with a wavelength of 350 to 400 nm and a power of 300 W or more. Finally, the organic solvent is removed under reduced pressure to obtain polyester hot melt adhesive. The amount of crosslinking agent added is 0.5 to 1‰ of the total molar amount of dibasic acid added when preparing the copolyester.

14. The method for preparing a polyester hot melt adhesive according to claim 5, characterized in that, The specific preparation process of polyester hot melt adhesive is as follows: copolyester, crosslinking agent and thermal initiator are mixed and heated to 140-170℃ for 3-10 minutes; wherein, the amount of crosslinking agent added is 0.5-1‰ of the total molar amount of dibasic acid added when preparing copolyester; the amount of thermal initiator added is 0.5-3% of the total mass of copolyester and crosslinking agent.

15. A method for preparing a polyester hot melt adhesive according to claim 5, characterized in that, The preparation method of the crosslinking agent is as follows: after mixing dithiol, acrylate and photoinitiator in a solvent, the mixture is reacted under ultraviolet light with a wavelength of 350-400nm and a power of 300W or more for 5-15 minutes, and then the crosslinking agent is obtained by extraction.

16. The method for preparing a polyester hot melt adhesive according to claim 15, characterized in that, The molar ratio of dithiol to acrylate is 2.5–3.5:1; the amount of photoinitiator added is 1–3% of the total mass of dithiol and acrylate.

17. A method for preparing a polyester hot melt adhesive according to claim 15, characterized in that, The dithiols are 1,2-ethanedithiol, 1,3-propanedithiol, 1,4-butanedithiol, 1,6-hexanedithiol, 2,3-butanedithiol or bis(2-mercaptoethyl) ether. The acrylate is 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, or dipropylene glycol diacrylate; The photoinitiator is α,α-dimethoxy-α-phenylacetophenone or 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylacetophenone.

18. An application of a polyester hot melt adhesive, characterized in that, The label is adhered to the PET bottle using a polyester hot melt adhesive as described in any one of claims 1 to 3.

19. The application of the polyester hot melt adhesive according to claim 18, characterized in that, The specific process is as follows: heat the polyester hot melt adhesive until it melts and then coat it onto the PET bottle, and then cover the label on the polyester hot melt adhesive and press it; or, the specific process is as follows: make the polyester hot melt adhesive into a polyester hot melt adhesive film and place it on the PET bottle, then cover the label on the polyester hot melt adhesive film, and then hot press the label together.

20. The application of a polyester hot melt adhesive according to any one of claims 18-19, characterized in that, After the label is adhered to the PET bottle, the PET bottle is immersed in a weak acid solution with a temperature of 70-90℃ and a pH of 3-3.5 for 24-36 hours. The label will then detach from the PET bottle, and the polyester hot melt adhesive will separate from the label.

Images