Polyester polyol as well as preparation method and application thereof

Abstract

The invention discloses polyester polyol. The polyester polyol comprises the following raw materials: A) 100 mol parts of ester of carboxylic acid or carboxylic acid derivative; b) 100 to 400 parts by mole of a polyol; and C) 10-100 mol parts of polyol containing a benzene ring and a cyclic acetal structure. The moisture-curing polyurethane adhesive prepared by taking the polyester polyol provided by the invention as a raw material has excellent bonding strength and impact toughness during use.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polyester polyols, more particularly, to a polyester polyol, a preparation method thereof and an application thereof in the field of moisture-curable polyurethane hot melt adhesives. BACKGROUND

[0002] Moisture-curable polyurethane hot melt adhesive (PUR) is an important reactive hot melt adhesive, and its basic component is an isocyanate-terminated prepolymer. It is applied in a molten state, rapidly forms initial strength after cooling, and then the -NCO groups at the end of the prepolymer react with moisture in the air to form a network crosslinked structure, thereby improving the bonding strength, durability, corrosion resistance and heat resistance of the adhesive layer, and is widely used in the fields of automobile manufacturing, shoe materials, textiles, packaging, wood processing, electronic component packaging, etc.

[0003] At present, the commercially available moisture-curable polyurethane hot melt adhesive still has the problem of low initial bonding strength. The introduction of rigid structures (such as naphthalene, biphenyl, aliphatic ring, piperazine ring, etc.) into the polyester polyol can improve the initial bonding strength of the adhesive, but the introduction of these structures will also make the adhesive layer brittle, and cracking will easily occur under dynamic load or thermal expansion and contraction, thereby affecting the bonding performance.

[0004] Patent CN115651597B improves the bonding strength of polyurethane adhesive by introducing adamantane and biphenyl structures into the polyester polyol, but adamantane and biphenyl are both very rigid structures, which may cause the polyurethane adhesive to become more brittle and have poor impact resistance. When the bonded structure is subjected to external force, bonding failure may occur.

[0005] Therefore, it is very meaningful to develop a polyester polyol and use it to prepare a moisture-curable polyurethane hot melt adhesive, which has excellent bonding performance and good impact toughness. SUMMARY

[0006] In view of the above, the present application develops a new type of polyester polyol, and a moisture-curable polyurethane hot melt adhesive prepared therefrom has excellent initial bonding strength and impact toughness.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] On the one hand, the present application provides a polyester polyol, the raw materials of which include:

[0009] (A) esterification product of carboxylic acid or carboxylic acid derivative: 100 mol parts;

[0010] (B) aliphatic polyol: 100-400 mol parts;

[0011] (C) polyol containing benzene ring and cyclic acetal structure: 10-100 moles.

[0012] In the polyester polyol described in the present application, the ester of component A carboxylic acid or carboxylic acid derivative specifically includes one or more of dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl sebacate, dimethyl undecanedioate, dimethyl dodecanedioate, dimethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, dimethyl furandicarboxylate, preferably one or more of dimethyl succinate, dimethyl adipate.

[0013] In the polyester polyol described in the present application, component B is a C2-C 12 aliphatic polyol, specifically including one or more of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, dodecanediol, 1,4-cyclohexanedimethanol, glycerol, trimethylolpropane, pentaerythritol, preferably C2-C6polyol, preferably including one or more of ethylene glycol, diethylene glycol, 1,4-butanediol, 1,6-hexanediol.

[0014] In the polyester polyol described in the present application, component C is a diol containing a benzene ring and a cyclic acetal structure, and the structure is shown in the following formula I:

[0015]

[0016] wherein R1 is selected from C1-C 10 alkyl or absent, preferably C1-C3linear alkyl or absent, more preferably -CH2- or absent; R2 and R3 are independently selected from any one of hydrogen, C1-C 10 alkyl, C1-C 10 alkoxy, preferably independently selected from any one of -H, -CH3, -OCH3; R5 is selected from hydrogen or C1-C 10 alkyl, preferably selected from hydrogen or C1-C3linear alkyl, more preferably selected from any one of -H, -CH3, -CH2CH3.

[0017] R1 is absent in the present application, which means that the hydroxyl group is directly connected to the benzene ring.

[0018] In the polyester polyol described in the present application, the synthesis of component C, the diol containing a benzene ring and a cyclic acetal structure, can be prepared by referring to the method in the literature Green Chem., 2020, 22, 1275-1290 or patent CN112920160B, or ordered from the manufacturer.

[0019] The polyester polyol comprises 100 moles of component A, 100-400 moles of component B, preferably 100-200 moles, and 10-100 moles of component C, preferably 40-90 moles.

[0020] In another aspect, the application provides a preparation method of the polyester polyol, which comprises the following steps: mixing component A, component B, component C and a catalyst under nitrogen protection, controlling the reaction temperature to be 120-220 DEG C, reacting for 2-14 hours under normal pressure, then reducing the pressure to-0.095 to-0.098 MPaG, continuing the reaction for 2-10 hours at 120-220 DEG C, and ending the reaction and cooling and discharging the product after the hydroxyl value and the acid value are qualified.

[0021] In the preparation method of the polyester polyol, the catalyst comprises at least one of titanium-based, tin-based, bismuth-based, antimony-based and germanium-based catalysts, and can be at least one of n-butyl titanate, tetraisopropyl titanate and dibutyltin dilaurate, and is preferably tetraisopropyl titanate.

[0022] In the preparation method of the polyester polyol, the catalyst is used in an amount of 5-500 ppm, preferably 20-300 ppm, based on the total mass of component A, component B and component C.

[0023] In the preparation method of the polyester polyol, the reaction is ended and the product is cooled and discharged when the acid value of the final polyester polyol is 0.01-10 mg KOH / g, preferably 0.01-5 mg KOH / g, and more preferably 0.02-2 mg KOH / g, and the hydroxyl value is 10-200 mg KOH / g, preferably 20-150 mg KOH / g, and more preferably 30-120 mg KOH / g.

[0024] In another aspect, the application provides an application of the polyester polyol in the field of polyurethane hot melt adhesives.

[0025] Specifically, the application provides a preparation method of a polyurethane hot melt adhesive, which comprises the following steps: under nitrogen protection, the polyester polyol is added into a reaction kettle, and the temperature is kept at 100-120 DEG C for 0.5-2 hours, then an isocyanate monomer is added and stirring is started, and the target polyurethane hot melt adhesive is prepared after the reaction is completed.

[0026] In the preparation method of the polyurethane hot melt adhesive, the mixing molar ratio of the OH group in the polyester polyol to the NCO group in the isocyanate monomer is 1:(1.5-3), and the molar ratio is preferably 1:(2.0-2.3).

[0027] The isocyanate monomer in the polyurethane hot melt adhesive preparation method is selected from one or more of toluene diisocyanate, diphenyl methane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dicyclohexyl methane diisocyanate and cyclohexane diisocyanate, and preferably diphenyl methane diisocyanate.

[0028] In the polyurethane hot melt adhesive preparation method, when the reaction reaches 2.0-5.0 wt% of theoretical NCO, preferably 2.3-4.5 wt%, it is considered that the reaction has reached the end point.

[0029] The polyurethane hot melt adhesive preparation method has the following beneficial effects:

[0030] (1) The benzene ring and cyclic acetal structure are introduced into the structure of the polyester polyol, which can increase the adhesion between the adhesive polyurethane hot melt adhesive and the substrate, and make the adhesive polyurethane hot melt adhesive have excellent bonding strength.

[0031] (2) The six-membered heterocyclic ring of the cyclic acetal structure has a boat type and a chair type conformation, and can absorb external energy by conformation transformation of the six-membered non-planar ring under the action of external force or applied energy, improve molecular motion, and ensure that the adhesive has high bonding strength while improving the toughness of the polyurethane hot melt adhesive. DETAILED DESCRIPTION

[0032] In order to better understand the technical solutions of the present application, the content of the present application will be further described below in combination with examples, but the content of the present application is not limited to the following examples.

[0033] The main raw materials used in the examples or comparative examples are described as follows: dimethyl succinate, dimethyl adipate and dimethyl terephthalate are purchased from Shandong Changyuan Chemical Co., Ltd. If no special instructions are given, the raw materials used in the examples or comparative examples are obtained from commercial channels.

[0034] The product performance in the examples and comparative examples of the present application is determined by the following methods:

[0035] Acid value determination: reference standard HG / T 2708-1995.

[0036] Hydroxyl value determination: reference standard HG / T 2709-1995.

[0037] Peeling strength: use a dispensing machine to uniformly apply adhesive to the surface of low-carbon steel, then use a press to bond the PVC sample and low-carbon steel, the bonding area is 25 mm wide and 200 mm long, the PVC sample is 250 mm long and 25 mm wide. After bonding for 1 h at 25℃ / 50RH%, test according to standard DIN 28510-1 2014, the separation peeling rate is 50 mm / min.

[0038] Shear impact strength: using two aluminum alloy metal sheet reference standards GB / T 6328-2021 to make samples, the bonding area width is 20 mm, the length is 30 mm, the thickness is 1.5 mm, and the impact speed is 2 m / s after 24 h under the condition of 25℃ / 50RH% according to the standard GB / T6328-2021 for testing.

[0039] Synthesis method of component C, polyol containing benzene ring and cyclic acetal structure:

[0040] According to the synthesis method of reference literature Green Chem., 2020, 22, 1275-1290, 3-methoxy-4-hydroxybenzaldehyde and glycerol were added into a single-necked flask in equimolar amount, heated and dissolved, then phosphoric acid was added, vacuumized and stirred for 4 hours. White solid was obtained at the end of the reaction, which was washed with water and dried in an oven at 60℃ for 3 hours to obtain solid powder C1 (hydrogen spectrum data: 1 H NMR (400 MHz, DMSO-d6) δ = 8.99 (s, 1H), 7.02 (s, 1H), 6.84 (d, J = 8.4 Hz, 1H), 6.74 (d, J = 8.1 Hz, 1H), 5.41 (s, 1H), 4.98 (d, J = 5.3 Hz, 1H), 4.04-3.89 (m, 4H), 3.77 (s, 3H), 3.48 (d, J = 5.0 Hz, 1H)).

[0041] Using the same method, 3-methoxy-4-hydroxybenzaldehyde was replaced by other aldehyde-containing monomers (p-hydroxybenzaldehyde, 3-(hydroxymethyl)-4-methylbenzaldehyde, 4-hydroxymethylbenzaldehyde), and glycerol was replaced by other alcohol substances (2-ethyl-1,2,3-propanetriol (cas number 59359-44-3), 2-methyl-1,2,3-propanetriol (cas number 25245-58-3)), and finally polyols C2-C4 containing benzene ring and cyclic acetal structure were obtained. The structures and hydrogen spectrum data of components C2-C4 used in the examples are as follows.

[0042]

[0043] C2: 1 H NMR (400 MHz, DMSO-d6) δ = 9.12 (s, 1H), 7.36-7.28 (m, 2H), 6.85-6.77 (m, 2H), 5.54-5.49 (m, 1H), 4.59 (s, 1H), 3.79 (s, 0H), 3.72 (d, J = 12.3 Hz, 2H), 1.60 (q, J = 7.4 Hz, 2H), 0.90 (t, J = 7.4 Hz, 3H)).

[0044] C3: ( 1 H NMR (400MHz, DMSO-d6) δ = 7.40 (dt, J = 1.9, 0.9Hz, 1H), 7.29 (ddd, J = 8.0, 1.9, 0.6Hz, 1H), 7.07 (dq, J = 8.2, 1.0Hz, 1H), 5.49 (d, J = 0.6Hz, 1H) ,4.79(t,J=5.5Hz,1H),4.57(dd,J=5.5,1.1Hz,2H),4.33(s,1H),3.77(s,1H),3.66(d,J=12.4Hz,2H),2.32(d,J=1.0Hz,3H),1.21(s,3H)).

[0045] C4: ( 1 H NMR (400MHz, DMSO-d6) δ=7.54–7.46(m,2H),7.33(dq,J=7.6,0.9Hz,2H),5.52(d,J=0.6Hz,1H),5.18(t,J =5.7Hz,1H),4.64(dt,J=5.6,1.0Hz,2H),4.33(s,1H),3.75(d,J=12.4Hz,2H),3.65(s,1H),1.21(s,3H)).

[0046] Examples 1-8

[0047] In a 30L stainless steel reactor equipped with a stirring, heating, temperature measuring, distillation column, and vacuum system, components A, B, C, and tetraisopropyl titanate (30ppm, based on the total mass of components A, B, and C) were added according to the feed amounts shown in Table 1. The mixture was heated to 180°C and stirred for 6 hours under nitrogen protection. Then, the temperature was increased to 210°C, and the vacuum system was turned on, with the pressure controlled at -0.095MPaG. The reaction continued until the acid hydroxyl value was qualified. The mixture was then cooled and discharged to obtain polyester polyol, denoted as POL 1-8. The hydroxyl acid value index is shown in Table 1.

[0048] Comparative Example 1

[0049] In a 30L stainless steel reactor equipped with a stirring, heating, temperature measuring, distillation column, and vacuum system, 12 mol of ethylene glycol, 10 mol of dimethyl succinate, and tetraisopropyl titanate (30 ppm, based on the total mass of components A and B) were added sequentially according to the feed amounts shown in Table 1. The mixture was heated to 180°C and stirred for 6 hours under nitrogen protection. Then, the temperature was increased to 210°C, and the vacuum system was turned on, controlling the pressure at -0.095 MPaG. The reaction continued until the acid hydroxyl value was qualified. The mixture was then cooled and discharged to obtain polyester polyol, denoted as POL9. The hydroxyl acid value index is shown in Table 1.

[0050] Comparative Example 2

[0051] Using the same process and dosage as in Example 4, C4 was replaced with V of the same mole fraction, denoted as POL 10. Specific indicators are shown in Table 1.

[0052] Comparative Example 3

[0053] Using the same process and dosage as in Example 5, C2 was replaced with the same mole fraction of IV, denoted as POL 11. Specific indicators are shown in Table 1.

[0054] Table 1. Composition and parameters of polyester polyols

[0055]

[0056] In Table 1, Ⅰ represents dimethyl succinate, Ⅱ represents dimethyl adipate, EG represents ethylene glycol, DEG represents diethylene glycol, HDO represents 1,6-hexanediol, Ⅳ represents 4,4'-dihydroxymethylbiphenyl (Shanghai Yuanye), and Ⅴ represents 1,4-bis(2-hydroxyethyl)piperazine (Aladdin).

[0057] Application Example 1-11

[0058] Under nitrogen protection, polyester POL 1-11 / MDI was added to a 2L round-bottom glass flask equipped with a stirrer at a ratio of 1:2.2 (mol / mol). The reaction was carried out at 120℃ for 2 hours. After the reaction was completed, the product was discharged into a well-sealed glass bottle. The resulting polyurethane hot melt adhesive is designated as PUR 1-11, and its application performance is shown in Table 2.

[0059] Table 2 Performance characterization results of polyurethane hot melt adhesive

[0060]

[0061] As can be seen from the above embodiments, the adhesives PUR 1 to PUR 8 containing benzene rings and cyclic acetal structures have higher peel strength and shear impact strength, that is, the polyester polyol of the present invention can improve the bonding strength and impact toughness of moisture-curing polyurethane hot melt adhesive.

Claims

1. A polyester polyol, characterized in that, Its raw materials include: (A) Esterifications of carboxylic acids or carboxylic acid derivatives: 100 molar parts; (B)C2~C 12 Aliphatic polyols: 100-400 molar parts, preferably 100-200 molar parts; (C) Polyols containing benzene rings and cyclic acetal structures: 10-100 molar parts, preferably 40-90 molar parts; The structure of the diol containing a benzene ring and a cyclic acetal structure in component C is shown in Formula I: Among them, R1 is selected from C1 to C2. 10 Alkyl groups may be absent, and R2 and R3 are independently selected from hydrogen, C1 to C3. 10 Alkyl groups, C1-C 10 R5 is selected from any of the alkoxy groups, where R5 is selected from hydrogen or C1 to C2. 10 Alkyl groups.

2. The polyester polyol according to claim 1, characterized in that, In the structure of component C, R1 is selected from a straight-chain alkyl group of C1 to C3 or is not present, R2 and R3 are independently selected from any one of -H, -CH3, and -OCH3, and R5 is selected from hydrogen or a straight-chain alkyl group of C1 to C3; preferably, R1 is -CH2- or is not present, and R5 is selected from any one of -H, -CH3, and -CH2CH3.

3. The polyester polyol according to claim 1 or 2, characterized in that, Component A includes one or more of the following: dimethyl succinate, dimethyl glutarate, dimethyl adipate, dimethyl sebacate, dimethyl undecanoate, dimethyl dodecanoate, dimethyl phthalate, dimethyl isophthalate, dimethyl terephthalate, and dimethyl furanate. And / or, component B includes one or more of ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 2-ethyl-2-butyl-1,3-propanediol, dodecanediol, 1,4-cyclohexanediol, glycerol, trimethylolpropane, and pentaerythritol, more preferably including one or more of ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6-hexanediol.

4. The method for preparing polyester polyol according to any one of claims 1-3, characterized in that, The process includes the following steps: Under nitrogen protection, components A, B, and C are mixed with the catalyst and reacted at atmospheric pressure. The pressure is then reduced to -0.095 to -0.098 MPaG, and the reaction continues for a period of time. Once the hydroxyl value and acid value are within acceptable limits, the reaction is terminated, and the product is cooled and discharged.

5. The preparation method according to claim 4, characterized in that, After mixing components A, B, and C with the catalyst, the mixture was reacted at atmospheric pressure and 120-220℃ for 2-14 hours, and then the reaction was continued at 120-220℃ for 2-10 hours after depressurization.

6. The preparation method according to claim 4 or 5, characterized in that, The catalyst includes at least one of titanium-based, tin-based, bismuth-based, antimony-based, and germanium-based catalysts, preferably selected from at least one of tetrabutyl titanate, tetraisopropyl titanate, and dibutyltin dilaurate.

7. The polyester polyol obtained by the preparation method according to any one of claims 4-6, characterized in that, The polyester polyol has an acid value of 0.01–10 mg KOH / g, preferably 0.01–5 mg KOH / g, more preferably 0.02–2 mg KOH / g, and a hydroxyl value of 10–200 mg KOH / g, preferably 20–150 mg KOH / g, more preferably 30–120 mg KOH / g.

8. A moisture-curing polyurethane hot melt adhesive, characterized in that, The hot melt adhesive is prepared by mixing and reacting the polyester polyol and isocyanate as described in any one of claims 1-3, specifically including the following steps: under nitrogen protection, the above-mentioned polyester polyol is added to the reaction vessel, kept at a constant temperature for a period of time, isocyanate monomer is added to it and stirring is started, and the reaction is carried out until the theoretical NCO is reached, so as to prepare polyurethane hot melt adhesive.

9. The hot melt adhesive according to claim 8, characterized in that, After the polyester polyol is added to the reactor, it is kept at 100-120℃ for 0.5-2 hours before the isocyanate monomer is added.

10. The hot melt adhesive according to claim 8 or 9, characterized in that, The isocyanate monomer is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, naphthalene diisocyanate, terephthalic diisocyanate, dicyclohexylmethane diisocyanate, and cyclohexane diisocyanate.

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