Polyester polyol for moisture-curing polyurethane hot melt adhesive as well as preparation method and application of polyester polyol

Abstract

The invention provides polyester polyol for a moisture-curing polyurethane hot melt adhesive as well as a preparation method and application of the polyester polyol. The polyester polyol is prepared from carboxylic acid and / or carboxylic acid derivative and polyol through esterification reaction, and the polyester polyol contains 20-300ppm of enol compound by mass. The moisture-curing polyurethane hot melt adhesive prepared from the polyester polyol has high viscosity stability at high temperature, and can be used for preparing moisture-curing reaction type polyurethane hot melt adhesive and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparing polyester polyols, and in particular relates to a polyester polyol for moisture-curing polyurethane hot melt adhesive, and a preparation method and application thereof. Background Art

[0002] Polyester polyols are important raw materials for the preparation of polyurethane resins, among which polyurethane adhesives are one of the important application directions. Specific product types include one-component adhesives, two-component adhesives, solvent adhesives and water-based adhesives, etc. The terminal application scenarios cover home life, automotive transportation, electronic products and sanitary products, etc.

[0003] Moisture-curing polyurethane hot melt adhesive (hereinafter referred to as HMPUR) is widely used in fields such as woodworking, textiles, and automobiles. It is a solvent-free, environmentally friendly adhesive, and its consumption continues to grow. HMPUR usually requires heating and melting for gluing. Due to the presence of free isocyanate functional groups in its chemical structure, side reactions will occur during the heating process, leading to an increase in viscosity and even surface curing and crusting, which will affect the construction performance of the adhesive and result in abnormal phenomena such as difficulty in controlling the amount of glue applied, clogging of equipment, and protrusion of particles in the product after gluing. EP0248658A uses isocyanate blocking technology to stabilize the blocked isocyanate functional groups in the adhesive. However, during the gluing process, it needs to be heated to a higher temperature to cause a deblocking reaction to regenerate the isocyanate functional groups. The gluing conditions are more stringent, and part of the blocking agent will volatilize, affecting the occupational health environment at the construction site, and part will remain in the glue liquid, generally having an adverse effect on the key application performance of the adhesive's initial adhesion strength.

[0004] Therefore, developing a polyester polyol that can stabilize the viscosity of HMPUR under high temperature conditions has important practical significance. Summary of the Invention

[0005] In order to overcome the deficiencies in the prior art, one of the objectives of the present invention is to provide a polyester polyol, wherein a moisture-curing polyurethane hot melt adhesive prepared using the polyester polyol has the characteristic of high viscosity stability at high temperatures.

[0006] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0007] A polyester polyol containing an enol compound in an amount of 20-300 ppm by mass, preferably 50-300 ppm by mass;

[0008] The structure of the enol compound is as follows:

[0009]

[0010] Wherein, n=1-8.

[0011] The inventors surprisingly discovered during their research that the viscosity stability of moisture-curing polyurethane hot melt adhesive at high temperatures is related to the above-mentioned enol compound. They further determined through experiments the quantitative range of the above-mentioned enol compound that needs to be controlled in order to control the high-temperature viscosity stability, and further derived a method for controlling this range.

[0012] The above-mentioned enol compound is produced by a side reaction of intramolecular dehydration of polyols such as butanediol and hexanediol at high temperature. The present invention controls the content of the compound within the range of the present invention by a one-step heating process combined with control of vacuum timing.

[0013] The n value in the enol compound is 2 less than the carbon number of the polyol. For example, if the diol in the raw material is butanediol, the enol compound is butanediol, and the n value is 2; if the diol in the raw material is hexanediol, the enol compound is hexanediol, and the n value is 4, and so on.

[0014] Existing technologies typically avoid continuous high-temperature reactions. For example, they initially conduct an esterification reaction at a constant temperature of 140-150°C before raising the temperature to a higher temperature. Under these conditions, the dehydration rate of polyols to form enols is slow. Furthermore, under vacuum, the generated enols are partially removed from the reaction system. Therefore, the timing of the vacuum is also a key factor affecting the enol content. The present invention simultaneously controls both temperature and vacuum timing, leveraging their synergistic effects to control the enol content within the disclosed range.

[0015] In one embodiment of the present invention, the polyester polyol is prepared by esterification of carboxylic acid and / or carboxylic acid derivatives with polyol; preferably, the carboxylic acid derivatives include one or more of anhydrides, esters, and acid chlorides.

[0016] In one embodiment of the present invention, the carboxylic acid and / or carboxylic acid derivative comprises aliphatic and / or aromatic carboxylic acids and carboxylic acid derivatives having carbon numbers of C4-C14, preferably comprising one or more of succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and tetradecanedioic acid, more preferably comprising one or more of succinic acid, adipic acid, and dodecanedioic acid. The above raw materials are commonly used raw materials for preparing polyester polyols.

[0017] In one embodiment of the present invention, the polyol component comprises a C3-C10 polyol, preferably a C3-C10 diol, more preferably one or more of 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, octanediol, and decanediol, and further preferably 1,4-butanediol and / or 1,6-hexanediol. The above raw materials are commonly used in the preparation of polyester polyols.

[0018] In one embodiment of the present invention, the polyester polyol has a hydroxyl value of 10-500 mg KOH / g and an acid value of 0-5 mg KOH / g; preferably, the hydroxyl value is 21-56 mg KOH / g and the acid value is 0-2 mg KOH / g.

[0019] Another object of the present invention is to provide a method for preparing polyester polyol.

[0020] A method for preparing polyester polyols, wherein the method is a vacuum melt polycondensation method for preparing the above-mentioned polyester polyols.

[0021] In one embodiment of the present invention, the preparation method is: adding carboxylic acid and / or carboxylic acid derivatives and polyols to a reaction kettle, heating, reacting at a constant temperature, opening a vacuum, reacting until the hydroxyl value and acid value reach the target value, returning to normal pressure, cooling and packaging the material; preferably, heating to 190-230°C, preferably 220-230°C, and maintaining a constant temperature for reaction; preferably, when the acid value is ≤10mg KOH / g, preferably when the acid value is 1-7mg KOH / g, opening the vacuum; preferably, the vacuum degree is -0.09 to -0.10Mpa, preferably the vacuum degree is -0.090 to -0.095Mpa.

[0022] Another object of the present invention is to provide an application of polyester polyol.

[0023] An application of a polyester polyol, wherein the polyester polyol is the polyester polyol described above, or is a polyester polyol prepared by the above preparation method, and the polyester polyol is used to prepare polyurethane rigid foams, coatings, elastomers, and adhesives, preferably used to prepare polyurethane adhesives, and more preferably used to prepare moisture-curing reactive polyurethane hot melt adhesives, water-based or oil-based polyurethane adhesives, and two-component polyurethane adhesives.

[0024] In one embodiment of the present invention, the terminal applications of the polyester polyol include woodworking flat adhesive, woodworking edge banding adhesive, woodworking covering adhesive, textile adhesive, automotive interior adhesive, automotive exterior adhesive, mobile phones / Bluetooth headsets / VR glasses, food soft packaging, and electronic adhesive.

[0025] Compared with the prior art, the present invention has the following positive effects:

[0026] The moisture-curing polyurethane hot melt adhesive prepared using this polyester polyol exhibits high viscosity stability at high temperatures. The positive effects of the present invention are demonstrated in the examples and comparative examples. After storage at 130°C, the viscosity of the moisture-curing polyurethane hot melt adhesive prepared using the polyester polyol of the present invention increased by 8-15%, while the viscosity of the comparative example increased by 25-32% under the same conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is the gas chromatogram of butenol;

[0028] Figure 2 This is the gas chromatography spectrum of butenol in the polyester polyol prepared in Example 1. DETAILED DESCRIPTION

[0029] In order to better understand the technical solutions of the present invention, the present invention is further described below with reference to the following embodiments, but the present invention is not limited to the following embodiments.

[0030] Source information of raw materials in the following examples:

[0031] Succinic acid was purchased from Bioamber, adipic acid was purchased from Shenma, sebacic acid, dodecanedioic acid, and tetradecanedioic acid were purchased from Shandong Kaisai, butanediol was purchased from Wanhua Chemical, hexanediol and nonanediol were purchased from Zhejiang Boju; cyclohexanedimethanol was purchased from Eastman, MDI-100 was purchased from Wanhua Chemical, and TIPT (tetraisopropyl titanate) was purchased from Boreck. All raw materials were industrial grade and commonly used in this field. Unless otherwise specified, all raw materials were obtained through commercial channels.

[0032] Acid value determination: Reference standard HG / T 2708-1995;

[0033] Determination of hydroxyl value: Reference standard HG / T 2709-1995;

[0034] Enol content: An Agilent gas chromatograph was used for testing. The sample was vaporized, separated by a chromatographic column, and detected by a flame ion detector. Working curves were established using standard samples such as butenol and hexenol, and the enol content was quantitatively determined using the external standard method.

[0035] Initial viscosity: Tested using a Brookfield CAP2000+ lamina viscometer. The viscometer is heated to 130°C. After the adhesive sample passes the test, take a sample and test it directly.

[0036] Viscosity after high temperature: Tested using a Brookfield CAP2000+ lamina viscometer. Place the qualified adhesive in an oven, open to air, at 130°C for 3 hours, then take a sample and test the viscosity at 130°C.

[0037] Examples 1-9

[0038] Preparation of polyester polyols: Under nitrogen, add the raw materials listed in the table below to a reactor in sequence. Heat the mixture to 190-230°C and allow the reaction to continue. When the acid value reaches ≤20 mg KOH / g, add 30 ppm TIPT catalyst and continue the reaction until the acid value reaches ≤10 mg KOH / g. Vacuum the reaction until the acid and hydroxyl values ​​reach the desired values. Nitrogen is then introduced to restore the pressure to normal, and the mixture is cooled and discharged. Specific formulations and process conditions are shown in the table below. The resulting polyester polyols are designated POL A-I.

[0039] Preparation of moisture-curable polyurethane hot melt adhesive: Under nitrogen protection, the polyester polyol of the present invention and MDI-100 are added to a reactor in a molar ratio of 1:2.2, and heated and stirred at 120°C to react until the NCO% content reaches the theoretical value. The material is discharged and stored in a nitrogen-sealed container.

[0040] Comparative Example 1

[0041] The preparation method of polyester polyol was referred to as Example 3, except that the temperature was first raised to 150° C. and kept at this temperature for 2 h, and then the temperature was raised to 220° C. and kept at this temperature for reaction.

[0042] A moisture-curing polyurethane hot melt adhesive was synthesized using the same preparation method as in Example 3.

[0043] Comparative Example 2

[0044] The method for preparing polyester polyols is similar to that of Example 3, except that vacuum is started when the acid value is 22.5 mg / KOH / g.

[0045] A moisture-curing polyurethane hot melt adhesive was synthesized using the same preparation method as in Example 3.

[0046] The data from the Examples and Comparative Examples demonstrate that the moisture-curing polyurethane hot-melt adhesive prepared using the polyester polyols obtained in the present invention exhibits higher viscosity stability at high temperatures. Compared to Example 3, Comparative Examples 1 and 2, which altered the heating schedule and vacuum timing, respectively, resulted in polyester polyols with enol contents below the range of the present invention. The resulting polyurethane hot-melt adhesive exhibited a higher viscosity growth rate at high temperatures.

[0047]

[0048]

[0049] Those skilled in the art will appreciate that, based on the teachings of this specification, some modifications or adjustments may be made to the present invention, and these modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A polyester polyol, characterized in that The polyester polyol contains an enol compound in an amount of 20-300 ppm by mass; The structure of the enol compound is as follows: Wherein, n=1-8.

2. The polyester polyol according to claim 1, wherein The polyester polyol is prepared by esterification reaction of carboxylic acid and / or carboxylic acid derivatives with polyol; Preferably, the carboxylic acid derivative comprises one or more of anhydride, ester, and acid chloride.

3. The polyester polyol according to claim 1 or 2, characterized in that The carboxylic acid and / or carboxylic acid derivatives include aliphatic and / or aromatic carboxylic acids and carboxylic acid derivatives having carbon numbers of C4-C14, preferably include one or more of succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid, and tetradecanedioic acid, more preferably include one or more of succinic acid, adipic acid, and dodecanedioic acid.

4. The polyester polyol according to any one of claims 1 to 3, characterized in that The polyol component comprises a polyol having a carbon number of C3-C10, preferably a diol having a carbon number of C3-C10, more preferably one or more of 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, octanediol, and decanediol, and further preferably 1,4-butanediol and / or 1,6-hexanediol.

5. The polyester polyol according to any one of claims 1 to 4, characterized in that The polyester polyol has a hydroxyl value of 10 to 500 mg KOH / g and an acid value of 0 to 5 mg KOH / g; preferably, the hydroxyl value is 21 to 56 mg KOH / g and the acid value is 0 to 2 mg KOH / g.

6. A method for preparing a polyester polyol, wherein the polyester polyol according to any one of claims 1 to 5 is prepared by the method, characterized in that: The preparation method is a vacuum melt polycondensation method.

7. The preparation method according to claim 6, characterized in that The preparation method comprises the following steps: adding carboxylic acid and / or carboxylic acid derivatives and polyols into a reaction kettle, heating, reacting at a constant temperature, opening a vacuum, reacting until the hydroxyl value and acid value reach target values, restoring the pressure, cooling, and packaging the product. Preferably, the temperature is raised to 190-230°C, preferably 220-230°C, and the reaction is maintained at a constant temperature; Preferably, when the acid value is ≤10 mg KOH / g, preferably when the acid value is 1 to 7 mg KOH / g, the vacuum is turned on; Preferably, the vacuum degree is -0.09 to -0.10 MPa, and preferably the vacuum degree is -0.090 to -0.095 MPa.

8. Use of a polyester polyol, wherein the polyester polyol is the polyester polyol according to any one of claims 1 to 5, or the polyester polyol prepared by the preparation method according to claim 6 or 7, characterized in that: The polyester polyol is used to prepare polyurethane rigid foams, coatings, elastomers, and adhesives, preferably used to prepare polyurethane adhesives, and more preferably used to prepare moisture-curing reactive polyurethane hot melt adhesives, water-based or oil-based polyurethane adhesives, and two-component polyurethane adhesives.

9. The use according to claim 8, characterized in that The terminal applications of the polyester polyol include woodworking flat adhesive, woodworking edge banding adhesive, woodworking covering adhesive, textile adhesive, automotive interior adhesive, automotive exterior adhesive, mobile phones / Bluetooth headsets / VR glasses, food soft packaging, and electronic adhesive.

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