A polyester polyol, a method for preparing the same, and use thereof

Abstract

The application discloses polyester polyol, a preparation method thereof and application of the polyester polyol, and raw materials of the polyester polyol comprise the following components: a) dicarboxylic acid or anhydride, 50-90 mol parts, b) dihydric alcohol, 100-130 mol parts, and c) cyclic alkyl-containing trihydric alcohol, 4-16 mol parts, wherein the cyclic alkyl-containing trihydric alcohol has the following general structural formula: R1 is selected from C3-C10 cyclic alkyl, and R2 is selected from C1-C6 alkylene. In the synthesis process, the cyclic alkyl-containing trihydric alcohol is introduced as a comonomer, a network crosslinking structure is formed by using trihydroxy, and the mechanical strength and heat resistance of the moisture-curable polyurethane hot melt adhesive are enhanced; the polyester polyol prepared in the application has long open time, plasticizer migration resistance and extremely low odor characteristics, and provides high-quality raw material basis for high-performance moisture-curable polyurethane materials.

Description

Technical Field

[0001] This invention belongs to the field of polyester polyols, specifically relating to a polyester polyol, its preparation method and its application. Background Technology

[0002] Moisture-curing polyurethane hot melt adhesives (PUR hot melt adhesives) are environmentally friendly adhesives based on isocyanate-terminated polyurethane prepolymers. Their common applications include woodworking furniture, automotive manufacturing, electronics assembly, and textiles and apparel. For PUR hot melt adhesives, the choice of raw material polyol is crucial. Compared to polyether polyols, polyester polyols have more rigid molecular chains and higher cohesive energy. This structural characteristic allows PUR hot melt adhesives prepared from them to maintain good dimensional stability and cohesive strength, and are less prone to creep.

[0003] When PUR hot melt adhesives are used in electronic components or fabric lamination, structural stability is required at high ambient temperatures. To improve the heat resistance of PUR hot melt adhesives, the industry often introduces trifunctional monomers (such as trimethylolpropane) as branching points during the synthesis of polyester polyols, increasing the entanglement and cohesive energy of the molecular chains. This three-dimensional crosslinked network macroscopically manifests as a significant increase in the heat distortion temperature of the hot melt adhesive, thus solving the technical problem of adhesive layer softening and detachment at high temperatures. However, this strategy often exacerbates the tendency of the molecular chains to arrange themselves in a regular pattern, leading to a further acceleration of the crystallization rate of the polyester polyol. This means that as heat resistance improves, the open time of the PUR hot melt adhesive is gradually compressed. Therefore, how to break the ordered stacking of chain segments in the molecular structure design, while maintaining a high crosslinking density and suppressing physical crystallization, has become a technical bottleneck in the development of polyester polyols for PUR hot melt adhesives. Patent CN101805584B discloses a high-temperature resistant, long-open-time, single-component, moisture-curing polyurethane adhesive. The formulation incorporates a polyester-organosilicon copolyester, introducing benzene rings to disrupt the ordered structure of the main chain. The addition of neopentyl glycol alters the polymer's mechanical properties. Subsequently, the polyester polyol is copolymerized with polyborosilane to prepare a hydroxyl-terminated polyester-organosilicon copolyester. This structure can extend the adhesive's open time and improve its resistance to hydrolysis, temperature, and chemical corrosion. However, this process has significant limitations: the organosilicon segments and the polyester polyol / polyurethane main chain differ greatly in polarity, making them highly susceptible to micro-phase separation during synthesis or storage. This results in a cloudy and layered adhesive solution, severely impacting the final bond strength.

[0004] Meanwhile, PUR hot melt adhesives are often used to bond soft polyvinyl chloride (PVC) or artificial leather substrates containing large amounts of plasticizers (such as phthalates). During hot pressing, plasticizer molecules in the substrate are activated by heat, diffusing and migrating into the adhesive layer, causing swelling and strength reduction. Therefore, conventional PUR hot melt adhesives have long faced the challenge of resisting plasticizer migration. To suppress plasticizer migration, patent CN108368232B uses a polyurethane composition containing polyisocyanates and specific aldehyde imine groups for substrates and capping layers sensitive to plasticizer migration. The aldehyde imine groups on the curing agent reduce odor and migration, improving compatibility and storage stability. However, aldehyde imines must be hydrolyzed to generate active primary amines before reacting with isocyanate groups. This means that its curing process is highly dependent on the moisture in the environment. In low-temperature, low-humidity (such as winter) construction environments, the hydrolysis rate of aldehyde imines will be significantly reduced, resulting in excessively long curing times, seriously affecting construction efficiency and initial strength.

[0005] Furthermore, as consumers demand "strict low-odor" products in sensitive sectors such as automobiles and home furnishings, environmental standards for PUR are becoming increasingly stringent. However, polyester polyols synthesized using traditional processes often retain a large amount of low-molecular-weight monomers. For example, residual diol monomers not only have volatile odors themselves, but more importantly, their active hydroxyl groups competitively consume isocyanate groups (-NCO), interfering with the wet curing kinetics of the PUR system, leading to incomplete cross-linking network construction and thus reducing the final cohesive strength of the material. Residual cyclic ketones and ethers have a high thermodynamic volatility and, as the main source of irritating odors, these low-molecular-weight substances are continuously released into the environment during product storage and use, limiting the application of PUR hot melt adhesives in high-end environmentally friendly fields.

[0006] Therefore, developing a polyester polyol that combines long open time, resistance to plasticizer migration, and low odor is of great application value for improving the overall performance of PUR hot melt adhesives. Summary of the Invention

[0007] To address the aforementioned shortcomings in the prior art, this invention provides a polyester polyol and its preparation method.

[0008] Another object of the present invention is to provide the application of the above-mentioned polyester polyol in the preparation of moisture-curing polyurethane hot melt adhesive.

[0009] The polyester polyol described in this invention incorporates cycloalkyl triols, utilizing trihydroxy groups to form a network crosslinking structure. This not only enhances the mechanical strength and heat resistance of the PUR hot melt adhesive but also slows down the physical crystallization rate of the polyester polyol, allowing the adhesive to maintain a molten viscous flow state for a longer period after application. Furthermore, this application unexpectedly discovered that the polyurethane hot melt adhesive prepared using the polyester polyol of this application also exhibits good resistance to plasticizer migration and low volatile organic compound (VOC) emissions.

[0010] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0011] A polyester polyol, wherein the polyester polyol comprises a raw material containing the following components:

[0012] a) Dicarboxylic acid or anhydride, 50-90 molar parts, for example 50, 60, 70, 80, 90 molar parts or any value between two of them, but not limited thereto, preferably 60-80 molar parts;

[0013] b) Diol, 100-130 molar parts, for example 100, 110, 120, 130 molar parts or any value between two of them, but not limited thereto, preferably 110-120 molar parts;

[0014] c) A cycloalkyl triol, 4-16 molar parts, for example 4, 8, 10, 12, 14, 16 molar parts or any value between two of them, but not limited thereto, preferably 6-14 molar parts;

[0015] Among them, component c) contains a cycloalkyl triol with the following general formula:

[0016]

[0017] R1 is selected from C3-C10 cycloalkyl groups, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, etc., preferably cyclohexyl. R2 is selected from C1-C6 alkylene groups, such as methylene, ethylene, propylene, butylene, pentylene, hexylene, etc., preferably methylene.

[0018] In component a) of the present invention, the dicarboxylic acid or anhydride is selected from C4-C14 dicarboxylic acids or anhydrides, preferably one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and tetradecanoic acid, preferably adipic acid.

[0019] In component b) of the present invention, the diol is selected from C2-C14 diols, preferably one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,4-pentanediol, 2-methyl-1,4-butanediol, neopentanediol, 1,5-pentanediol, 1,5-hexanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,6-heptanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, diethylene glycol, and dipropylene glycol, preferably 2-methyl-1,3-propanediol.

[0020] In this invention, preferably, component c) the cycloalkyl triol is selected from one or more of the following structures, more preferably structure C2.

[0021]

[0022] Preferably, component c) can be prepared using known methods. In some preferred embodiments of the present invention, the preparation method of component c) is as follows: using cycloalkylpropionaldehyde and alkyl aldehyde as raw materials, an aldol condensation reaction is carried out to synthesize a cycloalkyl-substituted dihydroxyaldehyde intermediate. This intermediate is then subjected to hydrogenation reduction under Raney nickel catalysis, and purified by post-treatment to obtain a cycloalkyl-containing triol. The structural formula of the cycloalkylpropionaldehyde is:

[0023]

[0024] R1 is selected from C3-C10 cycloalkyl groups, preferably cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and more preferably cyclohexyl.

[0025] The alkyl aldehydes are C1-C6 aldehydes, such as formaldehyde, acetaldehyde, n-propionaldehyde, or n-butyraldehyde.

[0026] The structure of the cycloalkyl-substituted dihydroxyaldehyde intermediate is as follows:

[0027]

[0028] R1 is selected from C3-C10 cycloalkyl groups, preferably cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and more preferably cyclohexyl. R2 is selected from C1-C6 alkylene groups, preferably methylene, ethylene, propylene, butylene, pentylene, hexylene, and more preferably methylene.

[0029] In this invention, the molar ratio of cycloalkylpropionaldehyde to alkylaldehyde is 2.2-2.6:1; preferably 2.3-2.5:1.

[0030] The reaction of cycloalkylpropionaldehyde and alkylaldehyde uses water as a solvent and diethylamine as a weak organic base catalyst.

[0031] The molar ratio of water, diethylamine and alkyl aldehyde is 15-25:0.1-0.4:1, preferably 18-22:0.2-0.3:1.

[0032] Preferably, the reaction temperature of cycloalkylpropionaldehyde and alkylaldehyde is 60-100℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, etc., and the reaction time is 2-6h, such as 2h, 3h, 4h, 5h, 6h, etc.; preferably, the reaction temperature is 70-90℃ and the reaction time is 3-5h.

[0033] Preferably, the hydrogenation reduction reaction is carried out in ethanol as a solvent.

[0034] Preferably, the molar ratio of the intermediate to Raney nickel is 3.0-6.0:1, more preferably 3.5-5.5:1.

[0035] Preferably, the reaction temperature of the hydrogenation reduction reaction is 100-150℃, such as 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc., and the reaction time is 4-9h, such as 4h, 5h, 6h, 7h, 8h, 9h, etc.; preferably, the reaction temperature is 120-140℃ and the reaction time is 5-8h.

[0036] Preferably, the reaction pressure of the hydrogenation reduction reaction is 3MPa-5MPa (gauge pressure).

[0037] Preferably, after the reaction is complete, the mixture is cooled to room temperature, the pressure is released, the reaction solution is removed, the catalyst is removed by diatomaceous earth filtration, and the filtrate is evaporated to remove ethanol and water, yielding a crude product. The crude product is added to a small amount of ethyl acetate and heated until completely dissolved. Insoluble impurities are removed by filtration while hot. After the filtrate cools, the precipitated white needle-like or flaky crystals are collected by filtration and dried to obtain C.

[0038] Preferably, the heating temperature after adding a small amount of ethyl acetate to the crude product is 60-90℃, such as 60℃, 70℃, 80℃, 90℃, etc.; preferably, the reaction temperature is 70-80℃.

[0039] On the other hand, the present invention also provides a method for preparing polyester polyols, comprising the following steps:

[0040] 1) Under nitrogen protection, components a), b), and c) are added sequentially to the reactor. The reaction temperature is 150℃-190℃, for example, 150℃, 160℃, 170℃, 180℃, 190℃, but not limited thereto; the reaction time is 2.0-6.0h, for example, 2.0h, 3.0h, 4.0h, 5.0h, 6.0h, but not limited thereto; preferably, the reaction temperature is controlled at 160℃-180℃ and the reaction time is 3.0-5.0h.

[0041] 2) Increase the reaction temperature to 195℃-240℃ for the reaction, such as 200℃, 210℃, 220℃, 230℃, 240℃, but not limited thereto; until the acid value of the product is ≤20mgKOH / g, preferably ≤17.2mgKOH / g; preferably, the reaction temperature is 210℃-230℃, preferably, in step 2), the reaction time is 5.0-10.0h, such as 5.0h, 6.0h, 7.0h, 8.0h, 9.0h, 10.0h, but not limited thereto, more preferably the reaction time is 6.0-9.0h.

[0042] 3) Add a catalyst and reduce the pressure in the reactor to -0.09MPa to -0.03MPa (gauge pressure), for example -0.09MPa, -0.07MPa, -0.05MPa, -0.03MPa, but not limited to this; then react at a reaction temperature of 200℃-250℃, for example 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, but not limited to this; the reaction time is 4.0-10.0h, for example 4.0h, 5.0h, 6.0h, 7.0h, 8.0h, 9.0h, 10.0h, but not limited to this.

[0043] Preferably, in step 3), the reaction pressure is -0.08MPa to -0.04MPa (gauge pressure), the reaction temperature is 210℃ to 240℃, and the reaction time is 6.0 to 8.0h.

[0044] In step 3), the acid value of the polyester polyol product obtained from the reaction needs to be controlled between 0.05-5.00 mgKOH / g and the hydroxyl value between 30-150 mgKOH / g.

[0045] 4) After the polyesterification reaction is completed, the crude polyester polyol is refined and purified.

[0046] Preferably, in step 4), purification is carried out by vacuum devolatilization, with the reactor pressure being -0.09 to -0.05 MPa (gauge pressure), for example -0.09 MPa, -0.08 MPa, -0.07 MPa, -0.06 MPa, or -0.05 MPa, but not limited thereto; the reactor temperature being 130-180℃, for example 130℃, 140℃, 150℃, 160℃, 170℃, or 180℃, but not limited thereto; and the extraction time being 4.0-30.0 h, for example 4.0 h, 5.0 h, 10.0 h, 15.0 h, 20.0 h, 25.0 h, or 30.0 h, but not limited thereto; preferably, the reactor pressure is controlled to -0.08 to -0.06 MPa (gauge pressure), the reactor temperature is reduced to 150-170℃, and the extraction time is 6.0-24.0 h.

[0047] Preferably, the polyester polyol has an acid value of 0.02-3.00 mgKOH / g, a hydroxyl value of 20-130 mgKOH / g, a residual diol content of <1000 ppm, a cyclic ketone content of <500 ppm, and a cyclic ether content of <600 ppm.

[0048] In this invention, steps 1) and 2) are carried out under normal pressure.

[0049] In this invention, the catalyst in step 3) is a phthalate catalyst, preferably one or more of tetraisopropyl titanate, tetrabutyl titanate, and tetraethyl titanate. Preferably, the catalyst in this invention is tetraisopropyl titanate. The amount of catalyst added is 4-400 ppm, for example, 4 ppm, 50 ppm, 100 ppm, 200 ppm, 300 ppm, or 400 ppm, but not limited thereto; preferably 30 ppm-300 ppm, based on the total mass of the polyester polyol raw materials.

[0050] In this invention, the acid value of the polyester polyol is 0.02-3.00 mgKOH / g, for example, 0.05 mgKOH / g, 0.1 mgKOH / g, 0.15 mgKOH / g, 0.2 mgKOH / g, 0.5 mgKOH / g, 1.0 mgKOH / g, 1.5 mgKOH / g, 2.0 mgKOH / g, 2.5 mgKOH / g, 3.0 mgKOH / g, but not limited thereto; the hydroxyl value is 20-130 mgKOH / g, for example, 20 mgKOH / g, 40 mgKOH / g, 60 mgKOH / g, 80 mgKOH / g, 100 mgKOH / g, 120 mgKOH / g, 130 mgKOH / g, but not limited thereto; preferably, the acid value of the polyester polyol is 0.08-2.00 mgKOH / g, and the hydroxyl value is 50-110 mgKOH / g.

[0051] In this invention, residual diols are removed from the polyester polyols through post-treatment. Residual diols refer to component b) monomers remaining in the product after the polyester polyol synthesis is completed. The residual diol content of the long open time, low odor polyester polyol is <1000ppm; preferably, the residual diol content of the polyester polyol is <950ppm.

[0052] In this invention, the cyclic ketone of the polyester polyol refers to the cyclic oligoketone generated by the decarboxylation-dehydration reaction of component a) at high temperature during the synthesis of the polyester polyol. The cyclic ketone content of the long open time and low odor polyester polyol is <500ppm; preferably, the cyclic ketone content of the polyester polyol is <470ppm.

[0053] Taking adipic acid as an example, the chemical equation for the self-condensation of adipic acid to form cyclopentanone byproduct is shown below:

[0054]

[0055] In this invention, the cyclic ether of the polyester polyol refers to the cyclic oligoether formed by the intramolecular dehydration reaction of component b) during the synthesis of the polyester polyol, and the content of the cyclic ether of the polyester polyol is <600ppm; preferably, the content of the cyclic ether of the long open time, low odor polyester polyol is <540ppm.

[0056] Taking 1,4-butanediol as an example, the following is a schematic equation for the formation of tetrahydrofuran byproduct from a diol via intramolecular dehydration:

[0057]

[0058] In this invention, the VOC emission of the polyester polyol is <40mg / kg, preferably <35mg / kg.

[0059] Another object of the present invention is to provide the use of the polyester polyol in the preparation of PUR hot melt adhesive.

[0060] A PUR hot melt adhesive is obtained by reacting raw materials comprising the following parts by weight:

[0061] A: Polyester polyol: 20-40 parts by weight, for example 20, 30, or 40 parts by weight, but not limited thereto; preferably 25-35 parts by weight;

[0062] B: Polyether polyol: 10-30 parts by weight, for example, 10, 20, or 30 parts by weight, but not limited thereto; preferably 15-35 parts by weight;

[0063] C: Tackifying resin: 5-25 parts by weight, for example, 5, 10, 15, 20, 25 parts by weight, but not limited thereto; preferably 10-20 parts by weight;

[0064] D: Isocyanate: 25-45 parts by weight, for example, 25, 30, 35, 40, or 45 parts by weight, but not limited thereto; preferably 30-40 parts by weight;

[0065] The polyester polyol mentioned herein is the polyester polyol described in this invention or the polyester polyol prepared by the preparation method described in this invention.

[0066] In some specific embodiments, the polyether polyol in component B includes one or more of polyethylene oxide polyol (PEG), polypropylene oxide polyol (PPG), and polytetrahydrofuran polyol (PTMEG), preferably polypropylene oxide polyol PPG.

[0067] In some specific embodiments, the tackifying resin in component C includes one or more of petroleum resin, hydrogenated petroleum resin, terpene resin, hydrogenated terpene resin, and monomer resin; preferably, terpene resin.

[0068] In some specific embodiments, the isocyanate in component D includes one or more of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), isophorone diisocyanate (IPDI), terephthalic diisocyanate (PPDI), terephthalic diisocyanate (XDI), tetramethyl diisocyanate (TMXDI), and 1,4-cyclohexane diisocyanate (CHDI); preferably MDI.

[0069] Furthermore, the present invention also provides a method for preparing the PUR hot melt adhesive:

[0070] A) Mix polyester polyol, polyether polyol and tackifying resin.

[0071] B) Add isocyanate to the mixture, stir and react under vacuum, and discharge the material after the NCO% content reaches the theoretical value.

[0072] Preferably, the reaction temperature in step B) is 80-120°C.

[0073] In some specific embodiments, the mixture needs to be dehydrated before adding isocyanate. This can be done by dehydrating the polyester polyol, polyether polyol and tackifying resin separately before mixing, or by mixing the polyester polyol, polyether polyol and tackifying resin first and then dehydrating the mixture.

[0074] Compared with the prior art, the above-described technical solution of the present invention has at least the following beneficial effects:

[0075] (1) This invention provides a polyester polyol with a long open time and low odor. By introducing a cycloalkyl-containing triol as a comonomer during the synthesis process, the branching degree of the polymer chain segments is improved, thereby effectively enhancing the mechanical strength and heat resistance of the PUR hot melt adhesive. Secondly, by introducing cycloalkyl groups with large volume and high rigidity into the polyester polyol molecular chain, a unique "rigid roadblock" effect is formed, which effectively hinders the regular arrangement and compact stacking of the molecular chain, slows down the physical crystallization rate of the polyol, and significantly extends the open time of the PUR hot melt adhesive, solving the technical problem of balancing high strength and high heat resistance with a long construction window.

[0076] (2) The cycloalkyl group introduced in this invention has a unique rigid spatial configuration. In the polyurethane curing network, these rigid alicyclic structures tend to aggregate with each other to form a highly dense "rigid micro-region", which constructs a physical barrier layer, effectively reduces the compatibility between the adhesive layer and the plasticizer, and significantly inhibits the migration of the plasticizer.

[0077] (3) The preparation process adopted in this invention can fully remove unreacted small molecule diol monomers and volatile byproducts such as cyclic ketones and cyclic ester ethers. After post-processing, the residual diol content in the obtained polyester polyol can be reduced to below 1000 ppm, the content of cyclic ketone byproducts can be reduced to below 500 ppm, the content of cyclic ether byproducts can be reduced to below 600 ppm, and the VOC emission can be reduced to below 40 mg / kg, which significantly improves the problems of strong odor and high VOC emission of traditional polyester polyols and their polyurethane products. Detailed Implementation

[0078] The present invention will be further described below with reference to specific embodiments. The embodiments described herein are merely illustrative and do not limit the scope of the invention.

[0079] Main raw material sources

[0080] The main raw materials used in the preparation examples and embodiments include: adipic acid purchased from Huafeng Chemical Co., Ltd.; diethylamine and Raney nickel catalyst purchased from Maclean's Company; trimethylolpropane purchased from Jiangsu Baichuan Co., Ltd.; azelaic acid, tetraisopropyl titanate, 3-cyclopentylpropanal, and 3-cyclohexylpropanal purchased from Aladdin; dodecanoic acid purchased from Shandong Kaisai Biotechnology Co., Ltd.; paraformaldehyde, n-butyraldehyde, diethylene glycol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, ethanol, and ethyl acetate purchased from Inokai Co., Ltd.; diatomaceous earth purchased from Shandong Zhengxing New Materials Co., Ltd.; MDI-100, neopentyl glycol, 1,4-butanediol, and WANOLC2010D purchased from Wanhua Chemical Co., Ltd.; and tackifying resin T100, a terpene resin purchased from Shangrao Sinan Resin Co., Ltd. Unless otherwise specified, all raw materials used were obtained through commercial channels.

[0081] Main testing methods

[0082] The test methods involved in the products of the embodiments and comparative examples include:

[0083] Acid value: The acid value test for polyester polyol products refers to HG / T2708-1995;

[0084] Hydroxyl value: The hydroxyl value test for polyester polyol products refers to HG / T2709-2022;

[0085] Moisture content: Moisture testing for polyester polyol products should refer to GB / T6283-2008;

[0086] Color code: Color code testing for polyester polyol products refers to GB / T3143-1982;

[0087] Content of residual small molecule alcohols, cyclic ketones, and cyclic ethers: Quantitative detection was performed by gas chromatography-mass spectrometry (GC-MS) using an internal standard method combined with a standard curve. Target compounds for residual small molecule alcohols include 1,4-butanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and diethylene glycol; target compounds for residual cyclic ketones include cyclopentanone; and target compounds for residual cyclic ethers include tetrahydrofuran.

[0088] NMR:¹H NMR was measured using a Bruker AV400 instrument. 10 mg of sample was dissolved in 0.5 mL of deuterated dimethyl sulfoxide (DMSO-d6), and the solvent peak at 2.50 ppm was used for calibration.

[0089] Peel strength: After dust and oil removal, PVC sheets are bonded using molten PUR hot melt adhesive, with a bonding area of ​​15×25mm. After bonding, the sheets are cured at 25℃ and 50%RH for 24 hours, and then tested using a tensile testing machine with a 180° peel method. Three samples are tested for each type of PUR, and the average value is taken.

[0090] Heat resistance: Six samples of each PUR were prepared according to the peel force test method and cured at 25℃ and 50% humidity for 24 hours. Three samples were used for initial peel force testing, and the average value was taken. The remaining three samples were placed in an 85℃ oven for constant temperature aging for 7 days. After cooling to room temperature, the peel force was tested. The peel force retention rate was calculated as the ratio (%) of the peel force after aging to the initial peel force, which was used to characterize the heat resistance of the material. The average value was taken.

[0091] Open time: The open time test for PUR hot melt adhesives is conducted in accordance with ASTM D4497-1994 (2004).

[0092] Plasticizer migration: Three samples were prepared for each PUR sample according to the peel strength test method. The samples were placed in an 85℃ oven for constant temperature aging for 7 days, and then cooled to room temperature. The adhesive layer at the bonding area was carefully peeled off, and the adhesive layer sample was accurately weighed. Ethyl acetate was used as the extraction solvent, and ultrasonic extraction was performed at room temperature for 60 min. The extract was filtered through a 0.22μm organic filter membrane and analyzed by gas chromatography-mass spectrometry (GC-MS). The plasticizer content was quantitatively detected by the internal standard method combined with the standard curve method. The PVC plasticizers included dibutyl phthalate (DBP), dioctyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), and dioctyl adipate (DOA). The test result of a single sample was the sum of the contents of the above five target plasticizers. The arithmetic mean of the total contents of the three parallel samples was then obtained, and the resulting value was the final total amount of plasticizer migration in the sample.

[0093] VOC Testing: Referring to ISO 16000-9 standard, the VOC release of polyester polyols and PUR was determined using a small-environment chamber / simulated release combined with adsorption tube sampling-thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS), according to the specified C6–C... 16 The total of all volatile organic compounds within the range is calculated.

[0094] Preparation Example 1

[0095] This preparation example provides a method for synthesizing a C1-containing cycloalkyl triol, as follows:

[0096] 1) In a three-necked flask equipped with a stirrer, thermometer and reflux condenser, add 72g paraformaldehyde, 360g water and 18g diethylamine;

[0097] 2) Start stirring and heat in a 60°C water bath until the paraformaldehyde is completely dissolved. Slowly add 140g of 3-cyclopentylpropanal and stir the reaction for 6 hours in a water bath.

[0098] 3) After cooling the reaction solution, the lower layer of oily substance was removed to obtain 168g of the intermediate 2,2-dihydroxymethylcyclopentylpropionaldehyde;

[0099] 4) Dissolve 2,2-dihydroxymethylcyclopentylpropionaldehyde in 161g of ethanol and pour the solution into a high-pressure reactor. Then add 8.5g of Raney nickel catalyst, seal the reactor, purge the air inside the reactor with nitrogen, and then purge the nitrogen with hydrogen.

[0100] 5) Start stirring, heat to 125°C, continuously introduce hydrogen gas, maintain pressure at 3.5 MPa, and react for 6.5 h;

[0101] 6) After the reaction is complete, cool to room temperature, release the pressure and take out the reaction solution. Remove the catalyst by diatomaceous earth filtration, remove ethanol and water by rotary evaporation of the filtrate, and obtain the crude product.

[0102] 7) Add the crude product to a small amount of ethyl acetate, heat to 75°C until completely dissolved, and filter while hot to remove insoluble impurities. After the filtrate cools, filter and collect the precipitated white needle-like or flaky crystals, and dry to obtain 134g of Cl with a number-average molecular weight (Mn) of 188g / mol. 1 H-NMR‌ (400MHz, DMSO): δ4.10(br,3H),3.40(d,6H,J=7.1Hz),1.32(d,2H,J=4.1Hz),1.35-1.64(m,9H).

[0103] Preparation Example 2

[0104] This preparation example provides a method for synthesizing C2-containing cycloalkyl triols, as detailed below:

[0105] 1) In a three-necked flask equipped with a stirrer, thermometer and reflux condenser, add 78g paraformaldehyde, 450g water and 29g diethylamine;

[0106] 2) Start stirring and heat in an 80°C water bath until the polyacetaldehyde is completely dissolved. Slowly add 168g of 3-cyclohexylpropionaldehyde and stir the reaction in a water bath for 4 hours.

[0107] 3) After cooling the reaction solution, the lower layer of oily substance was removed to obtain 210g of intermediate 2,2-dihydroxymethylcyclohexylpropionaldehyde;

[0108] 4) Dissolve 2,2-dihydroxymethylcyclohexylpropionaldehyde in 283g of ethanol and pour the solution into a high-pressure reactor. Then add 11.6g of Raney nickel catalyst, seal the reactor, purge the air inside the reactor with nitrogen, and then purge the nitrogen with hydrogen.

[0109] 5) Start stirring, heat to 150°C, continuously introduce hydrogen gas, maintain pressure at 4.0 MPa, and react for 4 hours;

[0110] 6) After the reaction is complete, cool to room temperature, release the pressure and take out the reaction solution. Remove the catalyst by diatomaceous earth filtration, remove ethanol and water by rotary evaporation of the filtrate, and obtain the crude product.

[0111] 7) Add the crude product to a small amount of ethyl acetate, heat to 90°C until completely dissolved, and filter while hot to remove insoluble impurities. After the filtrate cools, filter and collect the precipitated white needle-like or flaky crystals, and dry to obtain 145g of C2 with a number-average molecular weight (Mn) of 202g / mol. 1H-NMR‌ (400MHz, DMSO): δ4.11(br,3H),3.43(d,6H,J=7.0Hz),1.32(d,2H,J=6.0Hz),1.35-1.58(m,11H).

[0112] Preparation Example 3

[0113] This preparation example provides a method for synthesizing C3-containing cycloalkyl triols, as follows:

[0114] 1) In a three-necked flask equipped with a stirrer, thermometer and reflux condenser, add 84g n-butyraldehyde, 478g water and 36g diethylamine;

[0115] 2) Start stirring and heat in a 100°C water bath until the n-butyraldehyde is completely dissolved. Slowly add 175g of 3-cyclohexylpropanal and stir the reaction in a water bath for 2 hours.

[0116] 3) After cooling the reaction solution, the lower layer of oily substance was removed to obtain 236g of intermediate 2,2-dihydroxybutylcyclohexylpropionaldehyde;

[0117] 4) Dissolve 2,2-dihydroxybutylcyclohexylpropionaldehyde in 283g of ethanol and pour the solution into a high-pressure reactor. Then add 11.6g of Raney nickel catalyst, seal the reactor, purge the air inside the reactor with nitrogen, and then purge the nitrogen with hydrogen.

[0118] 5) Start stirring, heat to 100°C, continuously introduce hydrogen gas, maintain pressure at 4.0 MPa, and react for 9 hours;

[0119] 6) After the reaction is complete, cool to room temperature, release the pressure and take out the reaction solution. Remove the catalyst by diatomaceous earth filtration, remove ethanol and water by rotary evaporation of the filtrate, and obtain the crude product.

[0120] 7) Add the crude product to a small amount of ethyl acetate, heat to 60°C until completely dissolved, and filter while hot to remove insoluble impurities. After the filtrate cools, filter and collect the precipitated white needle-like or flaky crystals, and dry to obtain 158g of C3 with a number-average molecular weight (Mn) of 286g / mol. 1 H-NMR‌ (400MHz, DMSO): δ4.21(br,1H), δ4.11(br,2H), 3.41(d,2H, J=7.0Hz), 3. 45-3.73(dd,4H),1.59-1.88(m,12H),1.32(d,2H,J=6.0Hz),1.35-1.58(m,11H).

[0121] Comparative Example 1

[0122] 1) Under nitrogen protection, 10.2 kg adipic acid, 10.4 kg 2-methyl-1,3-propanediol and 1.13 kg trimethylolpropane were added sequentially to the reactor, the reaction temperature was raised to 170℃, and the reaction time was 4.0 h.

[0123] 2) Increase the reaction temperature to 215℃ and react for 7.5 hours until the acid value of the product is measured to be 15.8 mg KOH / g;

[0124] 3) After adding 202 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.07 MPa (gauge pressure), and then the reaction temperature was maintained at 225℃ for 7.0 h. During the reaction, the acid value of the product was measured to be 2.51 mg KOH / g and the hydroxyl value was 90 mg KOH / g, thus obtaining crude polyester polyol.

[0125] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.06 MPa (gauge pressure), lowering the reactor temperature to 155°C, and the extraction time to 15.0 h. The product is tested and found to have an acid value of 0.11 mg KOH / g, a hydroxyl value of 62 mg KOH / g, a residual diol content of 699 ppm, a cyclic ketone content of 315 ppm, a cyclic ether content of 376 ppm, and a VOC emission of 24 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a low-odor polyester polyol.

[0126] Comparative Example 2

[0127] 1) Under nitrogen protection, 11 kg of adipic acid, 10.1 kg of 1,4-butanediol and 0.67 kg of trimethylolpropane were added sequentially to the reactor, the reaction temperature was raised to 175°C, and the reaction time was 3.5 h.

[0128] 2) Increase the reaction temperature to 210℃ and react for 6.8 hours until the acid value of the product is measured to be 13.4 mg KOH / g;

[0129] 3) After adding 55 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.08 MPa (gauge pressure), and then the reaction temperature was maintained at 215℃ for 7.5 h. During the reaction, the acid value of the product was measured to be 1.32 mg KOH / g and the hydroxyl value was 65 mg KOH / g, thus obtaining crude polyester polyol.

[0130] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.08 MPa (gauge pressure), lowering the reactor temperature to 163°C, and the extraction time to 18.0 h. The product is tested and found to have an acid value of 0.16 mg KOH / g, a hydroxyl value of 69 mg KOH / g, a residual diol content of 526 ppm, a cyclic ketone content of 218 ppm, a cyclic ether content of 237 ppm, and a VOC emission of 22 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a low-odor polyester polyol.

[0131] Comparative Example 3

[0132] 1) Under nitrogen protection, 14.7 kg azelaic acid, 13.9 kg 3-methyl-1,5-pentanediol and 1.61 kg trimethylolpropane were added sequentially to the reactor, the reaction temperature was raised to 170℃, and the reaction time was 4.0 h.

[0133] 2) Increase the reaction temperature to 220℃ and react for 7.5 hours until the acid value of the product is measured to be 17.2 mg KOH / g;

[0134] 3) After adding 108 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.06 MPa (gauge pressure), and then the reaction temperature was maintained at 225℃ for 7.0 h. During the reaction, the acid value of the product was measured to be 0.88 mg KOH / g and the hydroxyl value was 46 mg KOH / g, thus obtaining crude polyester polyol.

[0135] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.07 MPa (gauge pressure), lowering the reactor temperature to 177°C, and the extraction time to 29.0 h. The product was tested and found to have an acid value of 1.08 mg KOH / g, a hydroxyl value of 22 mg KOH / g, a residual diol content of 246 ppm, a cyclic ketone content of 115 ppm, a cyclic ether content of 124 ppm, and a VOC release of 11 mg / kg. The reactor pressure was then restored to normal and the product was cooled before discharge, yielding a low-odor polyester polyol.

[0136] Comparative Example 4

[0137] 1) Under nitrogen protection, 20.7 kg of terephthalic acid, 13.8 kg of diethylene glycol and 4.58 kg of trimethylolpropane were added sequentially to the reactor, the reaction temperature was raised to 190℃, and the reaction time was 6.0 h.

[0138] 2) Increase the reaction temperature to 240℃ and react for 10.0 h until the acid value of the product is 12.5 mg KOH / g;

[0139] 3) After adding 400 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.09 MPa (gauge pressure), and then the reaction temperature was maintained at 250℃ for 10.0 h. During the reaction, the acid value of the product was measured to be 0.35 mg KOH / g and the hydroxyl value was 34 mg KOH / g, thus obtaining crude polyester polyol.

[0140] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.09 MPa (gauge pressure), lowering the reactor temperature to 180°C, and the extraction time to 30.0 h. The product is tested and found to have an acid value of 0.05 mg KOH / g, a hydroxyl value of 24 mg KOH / g, a residual diol content of 189 ppm, a cyclic ketone content of 57 ppm, a cyclic ether content of 66 ppm, and a VOC emission of 10 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a low-odor polyester polyol.

[0141] Example 1

[0142] 1) Under nitrogen protection, 7.3 kg adipic acid, 9 kg 2-methyl-1,3-propanediol and 0.75 kg Cl were added sequentially to the reactor, the reaction temperature was raised to 150℃, and the reaction time was 2.0 h;

[0143] 2) Increase the reaction temperature to 200℃ and react for 5.0 h until the acid value of the product is 16.5 mg KOH / g;

[0144] 3) After adding 4 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.03 MPa (gauge pressure), and then the reaction temperature was maintained at 200℃ for 4.0 h. During the reaction, the acid value of the product was measured to be 5 mg KOH / g and the hydroxyl value was 150 mg KOH / g, thus obtaining crude polyester polyol.

[0145] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.05 MPa (gauge pressure), lowering the reactor temperature to 130°C, and the extraction time to 4.0 h. The product is tested and found to have an acid value of 3.00 mg KOH / g, a hydroxyl value of 130 mg KOH / g, a residual diol content of 950 ppm, a cyclic ketone content of 470 ppm, a cyclic ether content of 540 ppm, and a VOC release of 35 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0146] Example 2

[0147] 1) Under nitrogen protection, 10.2 kg adipic acid, 10.4 kg 2-methyl-1,3-propanediol and 1.13 kg Cl were added sequentially to the reactor, the reaction temperature was raised to 170℃, and the reaction time was 4.0 h;

[0148] 2) Increase the reaction temperature to 215℃ and react for 7.5 hours until the acid value of the product is measured to be 15.7 mg KOH / g;

[0149] 3) After adding 202 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.07 MPa (gauge pressure), and then the reaction temperature was maintained at 225℃ for 7.0 h. During the reaction, the acid value of the product was measured to be 2.21 KOH / g and the hydroxyl value was 85 mg KOH / g. The reactor pressure was restored to normal and the product was cooled and discharged to obtain crude polyester polyol.

[0150] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.06 MPa (gauge pressure), lowering the reactor temperature to 155°C, and the extraction time to 15.0 h. The product is tested and found to have an acid value of 0.15 mg KOH / g, a hydroxyl value of 66 mg KOH / g, a residual diol content of 681 ppm, a cyclic ketone content of 344 ppm, a cyclic ether content of 379 ppm, and a VOC release of 26 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0151] Example 3

[0152] 1) Under nitrogen protection, 10.2 kg adipic acid, 10.4 kg 2-methyl-1,3-propanediol and 2.63 kg Cl were added sequentially to the reactor, the reaction temperature was raised to 170℃, and the reaction time was 4.0 h;

[0153] 2) Increase the reaction temperature to 215℃ and react for 7.5 hours until the acid value of the product is 15.5 mg KOH / g;

[0154] 3) After adding 202 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.07 MPa (gauge pressure), and then the reaction temperature was maintained at 225℃ for 7.0 h. During the reaction, the acid value of the product was measured to be 2.17 KOH / g and the hydroxyl value was 83 mg KOH / g. The reactor pressure was restored to normal and the product was cooled and discharged to obtain crude polyester polyol.

[0155] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.06 MPa (gauge pressure), lowering the reactor temperature to 155°C, and the extraction time to 15.0 h. The product is tested and found to have an acid value of 0.08 mg KOH / g, a hydroxyl value of 59 mg KOH / g, a residual diol content of 653 ppm, a cyclic ketone content of 325 ppm, a cyclic ether content of 356 ppm, and a VOC emission of 25 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0156] Example 4

[0157] 1) Under nitrogen protection, 11 kg of adipic acid, 10.1 kg of 1,4-butanediol and 0.67 kg of C2 were added to the reactor in sequence, the reaction temperature was raised to 175℃, and the reaction time was 3.5 h;

[0158] 2) Increase the reaction temperature to 210℃ and react for 6.8 hours until the acid value of the product is measured to be 14.6 mg KOH / g;

[0159] 3) After adding 55 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.08 MPa (gauge pressure), and then the reaction temperature was maintained at 215℃ for 7.5 h. During the reaction, the acid value of the product was measured to be 1.66 KOH / g and the hydroxyl value was 73 mg KOH / g. The reactor pressure was restored to normal and the product was cooled and discharged to obtain crude polyester polyol.

[0160] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.08 MPa (gauge pressure), lowering the reactor temperature to 163°C, and the extraction time to 18.0 h. The product is tested and found to have an acid value of 0.13 mg KOH / g, a hydroxyl value of 64 mg KOH / g, a residual diol content of 559 ppm, a cyclic ketone content of 209 ppm, a cyclic ether content of 230 ppm, and a VOC release of 19 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0161] Example 5

[0162] 1) Under nitrogen protection, 10.9 kg adipic acid, 10.1 kg 1,4-butanediol and 2.02 kg C2 were added sequentially to the reactor, the reaction temperature was raised to 175℃, and the reaction time was 3.5 h;

[0163] 2) Increase the reaction temperature to 210℃ and react for 6.8 hours until the acid value of the product is measured to be 14.3 mg KOH / g;

[0164] 3) After adding 55 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.08 MPa (gauge pressure), and then the reaction temperature was maintained at 215℃ for 7.5 h. During the reaction, the acid value of the product was measured to be 1.79 KOH / g and the hydroxyl value was 69 mg KOH / g. The reactor pressure was restored to normal and the product was cooled and discharged to obtain crude polyester polyol.

[0165] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.08 MPa (gauge pressure), lowering the reactor temperature to 163°C, and the extraction time to 18.0 h. The product is tested and found to have an acid value of 0.14 mg KOH / g, a hydroxyl value of 55 mg KOH / g, a residual diol content of 536 ppm, a cyclic ketone content of 186 ppm, a cyclic ether content of 205 ppm, and a VOC release of 15 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0166] Example 6

[0167] 1) Under nitrogen protection, 10.9 kg adipic acid, 10.1 kg 1,4-butanediol and 2.02 kg C2 were added sequentially to the reactor, the reaction temperature was raised to 175℃, and the reaction time was 3.5 h;

[0168] 2) Increase the reaction temperature to 210℃ and react for 6.8 hours until the acid value of the product is measured to be 14.1 mg KOH / g;

[0169] 3) After adding 55 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.08 MPa (gauge pressure), and then the reaction temperature was maintained at 215℃ for 7.5 h. During the reaction, the acid value of the product was measured to be 1.55 KOH / g and the hydroxyl value was 63 mg KOH / g. The reactor pressure was restored to normal and the product was cooled and discharged to obtain crude polyester polyol.

[0170] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.08 MPa (gauge pressure), lowering the reactor temperature to 168°C, and the extraction time to 25.0 h. The product is tested and found to have an acid value of 0.10 mg KOH / g, a hydroxyl value of 56 mg KOH / g, a residual diol content of 360 ppm, a cyclic ketone content of 132 ppm, a cyclic ether content of 144 ppm, and a VOC release of 11 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0171] Example 7

[0172] 1) Under nitrogen protection, 14.7 kg azelaic acid, 13.9 kg 3-methyl-1,5-pentanediol and 3.43 kg C3 were added sequentially to the reactor, the reaction temperature was raised to 170℃, and the reaction time was 4.0 h;

[0173] 2) Increase the reaction temperature to 220℃ and react for 7.5 hours until the acid value of the product is measured to be 13.8 mg KOH / g;

[0174] 3) After adding 108 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.06 MPa (gauge pressure), and then the reaction temperature was maintained at 225℃ for 7.0 h. During the reaction, the acid value of the product was measured to be 0.86 KOH / g and the hydroxyl value was 55 mg KOH / g. The reactor pressure was restored to normal and the product was cooled and discharged to obtain crude polyester polyol.

[0175] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.07 MPa (gauge pressure), lowering the reactor temperature to 177°C, and the extraction time to 28.0 h. The product was tested and found to have an acid value of 1.13 mg KOH / g, a hydroxyl value of 28 mg KOH / g, a residual diol content of 255 ppm, a cyclic ketone content of 109 ppm, a cyclic ether content of 120 ppm, and a VOC release of 9 mg / kg. The reactor pressure was then restored to normal and the product was cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0176] Example 8

[0177] 1) Under nitrogen protection, 15 kg of terephthalic acid, 13.8 kg of diethylene glycol and 4.58 kg of C3 were added to the reactor in sequence, the reaction temperature was raised to 190℃, and the reaction time was 6.0 h.

[0178] 2) Increase the reaction temperature to 240℃ and react for 10.0 h until the acid value of the product is 13.5 mg KOH / g;

[0179] 3) After adding 400 ppm tetraisopropyl titanate (based on the total mass of polyester polyol raw materials), the pressure of the reactor was reduced to -0.09 MPa (gauge pressure), and then the reaction temperature was maintained at 250℃ for 10.0 h. During the reaction, the acid value of the product was measured to be 0.05 KOH / g and the hydroxyl value was 30 mg KOH / g. The reactor pressure was restored to normal and the temperature was lowered before discharging to obtain crude polyester polyol.

[0180] 4) After the polyesterification reaction, the crude polyester polyol is subjected to a vacuum devolatilization process to remove residual unreacted monomers from the reactor. This process is characterized by controlling the reactor pressure to -0.09 MPa (gauge pressure), lowering the reactor temperature to 180°C, and the extraction time to 30.0 h. The product is tested and found to have an acid value of 0.02 mg KOH / g, a hydroxyl value of 20 mg KOH / g, a residual diol content of 183 ppm, a cyclic ketone content of 53 ppm, a cyclic ether content of 62 ppm, and a VOC release of 6 mg / kg. The reactor pressure is then restored to normal and the product is cooled before discharge, yielding a polyester polyol with a long open time and low odor.

[0181] Application examples

[0182] 1) According to the synthesis formula in Table 1, the long open time, low odor polyester polyol, polyether polyol and tackifying resin synthesized in the embodiments of the present invention are mixed together and subjected to vacuum dehydration treatment at 120°C.

[0183] 2) Cool the mixture to 100℃, add isocyanate, stir and react under -0.10MPa vacuum, and discharge the material after the NCO% content reaches the theoretical value to obtain PUR1-12.

[0184] Table 1. Formulation of PUR1-12 (parts by weight)

[0185]

[0186] Performance testing

[0187] The residual diol content, cyclic ketone content, cyclic ether content, and VOC emission of polyester polyols were determined using the above method, as well as the peel strength, heat resistance, open time, plasticizer migration, and VOC emission of PUR. The results are shown in Table 2. From the data in the table, it can be seen that:

[0188] a) Comparisons between Comparative Example 1 and Example 2, Comparative Example 2 and Example 4, Comparative Example 3 and Example 7, and Comparative Example 4 and Example 8 show that using cycloalkyl-containing triols as raw materials in the synthesis of polyester polyols significantly prolongs the open time of the PUR hot melt adhesive, with the longest open time reaching approximately 14 minutes. The main reason is that cycloalkyl groups have a larger volume and rigidity; introducing them into the polyester polyol molecular chain creates more significant steric hindrance than trimethylolpropane, effectively reducing the crystallization tendency of the molecular chain, thus allowing the adhesive to maintain its tackiness for a longer period after coating. Simultaneously, the dense hydrophobic microdomains constructed by the cycloalkyl groups effectively block the outward migration of plasticizers from the substrate, significantly reducing the amount of plasticizer migration on the PUR film, down to a minimum of 25 mg / kg. In addition, by adding a specific high-vacuum extraction process after the synthesis of polyester polyol, the residual amount of oligomers in polyester polyol can be effectively reduced. The residual diol content is as low as 183 ppm, the cyclic ketone content is as low as 53 ppm, and the cyclic ether content is as low as 62 ppm. PUR synthesized from this raw material has low VOC characteristics, with a VOC release of as low as 31 mg / kg.

[0189] (b) The comparison results between Examples 2 and 3, and Examples 4 and 5, show that increasing the proportion of cycloalkyl triols in the polyester polyol synthesis process can significantly improve the peel strength and heat resistance of PUR hot melt adhesive, prolong the open time of PUR hot melt adhesive, and reduce the amount of plasticizer migration on the adhesive film. This indicates that as the content of trihydroxy structural units in the polyester polyol molecular chain increases, the three-dimensional network structure is strengthened, effectively improving the mechanical strength and heat resistance of the material; at the same time, the increase in the proportion of cycloalkyl groups effectively hinders the orderly arrangement and close packing of molecular chains, greatly slowing down the physical crystallization rate of polyester polyol molecular chains, thereby significantly prolonging the open time after adhesive coating, and solving the technical problem of balancing high strength and high heat resistance with a long application window.

[0190] Table 2 Performance test results of polyester polyols and PUR

[0191]

[0192] The present invention has been illustrated with the above embodiments to explain the detailed method of the present invention. However, the present invention is not limited to the detailed method described above, that is, it does not mean that the present invention must rely on the detailed method described above to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polyester polyol, characterized in that, The polyester polyol comprises the following raw materials: a) Dicarboxylic acid or acid anhydride, 50-90 molar parts, preferably 60-80 molar parts; b) Diol, 100-130 molar parts, preferably 110-120 molar parts; c) Triols containing cycloalkyl groups, 4-16 molar parts, preferably 6-14 molar parts; Among them, component c) contains a cycloalkyl triol with the following general formula: R1 is selected from C3-C10 cycloalkyl groups, preferably cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and more preferably cyclohexyl. R2 is selected from C1-C6 alkylene groups, preferably methylene, ethylene, propylene, butylene, pentylene, hexylene, and more preferably methylene.

2. The polyester polyol according to claim 1, characterized in that, In component a), the dicarboxylic acid or anhydride is selected from C4-C14 dicarboxylic acids or anhydrides, preferably one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, and tetradecanoic acid, more preferably adipic acid. And / or, in component b), the diol is selected from C2-C14 diols, preferably one or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1,4-butanediol, 1,4-pentanediol, 2-methyl-1,4-butanediol, neopentanediol, 1,5-pentanediol, 1,5-hexanediol, 2-methyl-1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,6-heptanediol, 2-methyl-1,6-hexanediol, 3-methyl-1,6-hexanediol, diethylene glycol, and dipropylene glycol, preferably 2-methyl-1,3-propanediol; And / or, component c) the cycloalkyl-containing triol is selected from one or more of the following structures, more preferably structure C2; 。 3. The polyester polyol according to claim 1 or 2, characterized in that, The preparation method of component c) is as follows: using cycloalkylpropionaldehyde and alkylaldehyde as raw materials, a hydroxyl condensation reaction is carried out to synthesize a cycloalkyl-substituted dihydroxyaldehyde intermediate; then the intermediate is subjected to a hydrogenation reduction reaction under Raney nickel catalysis, and the cycloalkyl-containing triol is obtained by post-treatment purification. The structural formula of the cycloalkylpropionaldehyde is: R1 is selected from C3-C10 cycloalkyl groups, preferably cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and more preferably cyclohexyl; The alkyl aldehyde is a C1-C6 aldehyde, preferably formaldehyde, acetaldehyde, n-propionaldehyde or n-butyraldehyde; The structure of the cycloalkyl-substituted dihydroxyaldehyde intermediate is as follows: R1 is selected from C3-C10 cycloalkyl groups, preferably cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl, and more preferably cyclohexyl. R2 is selected from C1-C6 alkylene groups, preferably methylene, ethylene, propylene, butylene, pentylene, hexylene, and more preferably methylene.

4. The polyester polyol according to claim 3, characterized in that, The molar ratio of the cycloalkylpropionaldehyde to the alkylaldehyde is 2.2-2.6:1; preferably 2.3-2.5:

1. And / or, the reaction of cycloalkylpropionaldehyde and alkylaldehyde uses water as a solvent and diethylamine as an organic weak base catalyst. And / or, the molar ratio of water, diethylamine and alkyl aldehyde is 15-25:0.1-0.4:1, preferably 18-22:0.2-0.3:1; And / or, the reaction temperature of cycloalkylpropionaldehyde and alkylaldehyde is 60-100℃, and the reaction time is 2-6h; preferably, the reaction temperature is 70-90℃, and the reaction time is 3-5h. And / or, the hydrogenation reduction reaction is carried out in ethanol as a solvent; And / or, the molar ratio of the intermediate to Raney nickel is 3.0-6.0:1, preferably 3.5-5.5:1; And / or, the reaction temperature of the hydrogenation reduction reaction is 100-150℃, and the reaction time is 4-9h; preferably, the reaction temperature is 120-140℃, and the reaction time is 5-8h. And / or, the reaction pressure of the hydrogenation reduction reaction is 3MPa-5MPa (gauge pressure).

5. The method for preparing polyester polyol according to any one of claims 1-4, characterized in that, Includes the following steps: 1) Under nitrogen protection, components a), b), and c) are added sequentially to the reactor, and the reaction is carried out at 150℃-190℃ for 2.0-6.0 hours. 2) Increase the reaction temperature to 195℃-240℃ and continue the reaction until the acid value of the product is ≤20mgKOH / g, preferably ≤17.2mgKOH / g; 3) Add a catalyst and reduce the pressure in the reactor to -0.09MPa~-0.03MPa (gauge pressure), then react at a reaction temperature of 200℃-250℃ for a reaction time of 4.0-10.0h; 4) After the polyesterification reaction is completed, the crude polyester polyol is refined and purified.

6. The preparation method according to claim 5, characterized in that, In step 1), the reaction temperature is controlled at 160℃-180℃, and the reaction time is 3.0-5.0h; Preferably, in step 2), the reaction temperature is 210℃-230℃, and the reaction time is 5.0-10.0h, more preferably 6.0-9.0h; Preferably, in step 3), the reaction pressure is -0.08MPa to -0.04MPa (gauge pressure), the reaction temperature is 210℃ to 240℃, and the reaction time is 6.0 to 8.0h; Preferably, in step 3), the acid value of the polyester polyol product obtained from the reaction needs to be controlled at 0.05-5.00 mgKOH / g, and the hydroxyl value at 30-150 mgKOH / g; Preferably, in step 4), purification is carried out by vacuum devolatilization, with the reactor pressure being -0.09 MPa to -0.05 MPa (gauge pressure), the reactor temperature being 130-180°C, and the extraction time being 4.0-30.0 h; more preferably, the reactor pressure is controlled to -0.08 to -0.06 MPa (gauge pressure), the reactor temperature is reduced to 150-170°C, and the extraction time is 6.0-24.0 h; Preferably, the polyester polyol has an acid value of 0.02-3.00 mgKOH / g, a hydroxyl value of 20-130 mgKOH / g, a residual diol content of <1000 ppm, a cyclic ketone content of <500 ppm, and a cyclic ether content of <600 ppm. Preferably, steps 1) and 2) are carried out under normal pressure; Preferably, the catalyst in step 3) is a phthalate catalyst, preferably one or more of tetraisopropyl titanate, tetrabutyl titanate, and tetraethyl titanate. More preferably, the catalyst is tetraisopropyl titanate. Preferably, the amount of catalyst added is 4-400 ppm, more preferably 30 ppm-300 ppm, based on the total mass of the polyester polyol raw materials; Preferably, the polyester polyol has an acid value of 0.02-3.00 mgKOH / g and a hydroxyl value of 20-130 mgKOH / g; Preferably, the polyester polyol has an acid value of 0.08-2.00 mgKOH / g and a hydroxyl value of 50-110 mgKOH / g.

7. Use of a polyester polyol according to any one of claims 1-3 or a polyester polyol prepared by any one of claims 4-6 in the preparation of PUR hot melt adhesive.

8. A PUR hot melt adhesive, obtained by reacting raw materials comprising the following parts by weight: A: Polyester polyol: 20-40 parts by weight, preferably 25-35 parts by weight; B: Polyether polyol: 10-30 parts by weight, preferably 15-35 parts by weight; C: Tackifying resin: 5-25 parts by weight, preferably 10-20 parts by weight; D: Isocyanate: 25-45 parts by weight, preferably 30-40 parts by weight; The polyester polyol is the polyester polyol according to any one of claims 1-3 or the polyester polyol prepared by the preparation method according to any one of claims 4-6.

9. The hot melt adhesive according to claim 8, characterized in that, Component B contains polyether polyols including one or more of polyethylene oxide polyols, polypropylene oxide polyols, and polytetrahydrofuran polyols, preferably polypropylene oxide polyols; And / or, the tackifying resin in component C includes one or more of petroleum resin, hydrogenated petroleum resin, terpene resin, hydrogenated terpene resin, and monomer resin; preferably, terpene resin. And / or, the isocyanate in component D includes one or more of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, isophorone diisocyanate, terephthalic diisocyanate, terephthalic diisocyanate, tetramethyl diisocyanate, and 1,4-cyclohexane diisocyanate; preferably diphenylmethane diisocyanate.

10. The method for preparing the PUR hot melt adhesive according to claim 9, characterized in that, A) Mix polyester polyol, polyether polyol and tackifying resin. B) Add isocyanate to the mixture, stir and react under vacuum, and discharge the material after the NCO% content reaches the theoretical value; Preferably, the reaction temperature in step B) is 80-120°C.

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