A low-reactivity polyester polyol, its preparation method and application

Abstract

The invention discloses a low-reactivity polyester polyol and a preparation method thereof, wherein the low-reactivity polyester polyol is prepared by esterification and polycondensation of 100 molar parts of a dibasic acid / anhydride, 90-150 molar parts of a primary hydroxyl polyol and 1-50 molar parts of a non-primary hydroxyl sulfur-containing polyol. The curing time and the operable time of a two-component polyurethane adhesive product prepared by using the polyester polyol of the invention are moderate, and the product has the characteristics of being easy to clean.

Description

Technical Field

[0001] The invention belongs to the field of polyester polyol and polyurethane, and specifically relates to a low-reactivity polyester polyol and a preparation method and application thereof. Background Art

[0002] Polyurethane adhesives are adhesives containing urethane groups and / or isocyanate groups in their molecular chains. They have excellent performance and are therefore widely used in many industrial and civil fields. Two-component polyurethane adhesives are the most important category of polyurethane adhesives, usually consisting of a main agent (hydroxyl component or polyurethane prepolymer with terminal NCO) and a curing agent (component containing free isocyanate groups or polyols / amines). During use, the two components need to be mixed and cured under certain conditions to produce a higher bonding strength.

[0003] Polyester polyols, as one of the raw materials for preparing polyurethane adhesives, are mainly obtained by condensation polymerization of polyols with polyacids or anhydrides in the presence or absence of catalysts. They can provide polyurethane materials with better adhesive strength and weather resistance.

[0004] However, the reaction rate of polyester polyol and isocyanate has an important influence on the curing time of two-component polyurethane adhesive. If the reaction rate of polyester polyol and isocyanate is too slow, the curing rate of both is slow, the curing time of the adhesive is long, but the initial adhesion strength is weak; if the reaction rate of polyester polyol and isocyanate is too fast, the curing rate of both is fast, the curing time of the adhesive is short, resulting in a short operating time. When the reaction rate of polyester polyol and isocyanate is slow, the polymerization reaction can be accelerated by adding a catalyst. In comparison, an excessively high reaction rate is more difficult to control.

[0005] In order to reduce the reaction rate of polyester polyols and isocyanates and extend the operation time and construction time of two-component adhesives, researchers have done a lot of research. B. Fortunato et al. reduced the reactivity of polyester polyols and isocyanates by adding phosphorus-containing additives and complex esterification catalysts, but such acidic additives will reduce the hydrolysis resistance of polyurethane adhesives; Patent CN 1759132A reduces the reactivity by contacting polyester polyols prepared with tin catalysts with oxygen, but this method may cause the polyester polyol product to oxidize and increase the color number. At the same time, this method increases the post-processing process and the process is cumbersome.

[0006] In summary, the reactivity of polyester polyol products has an important influence on the curing time and workable time of two-component polyurethane adhesives. Therefore, it is particularly important to develop a polyester polyol with low reactivity. Summary of the invention

[0007] The present invention provides a low-reactivity polyester polyol and a preparation method thereof. The polyester polyol prepared by the present invention has a moderate reaction rate with an isocyanate monomer, and the obtained two-component polyurethane adhesive has a moderate curing speed and a suitable operating time, and the adhesive has the characteristic of being easy to clean.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] On the one hand, the low-reactivity polyester polyol provided by the present invention is composed of the following components:

[0010] A) dibasic acid / anhydride: 100 parts by mole;

[0011] B) primary hydroxyl polyol: 90-150 mol parts, preferably 100-130 mol parts;

[0012] C) Non-primary hydroxyl sulfur-containing polyol: 1-50 mole parts, preferably 10-40 mole parts.

[0013] In the present invention, the dibasic acid in component A is selected from aliphatic dicarboxylic acids or aromatic dicarboxylic acids having 2-20 carbon atoms, and the acid anhydride is selected from aliphatic acid anhydrides or aromatic acid anhydrides having 4-20 carbon atoms; in some specific embodiments, the dibasic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, furandicarboxylic acid, phthalic acid, isophthalic acid or terephthalic acid, and the dibasic acid is more preferably succinic acid and / or adipic acid; the acid anhydride is selected from one or more of succinic anhydride, glutaric anhydride, adipic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride or phthalic anhydride, and the acid anhydride is more preferably succinic anhydride.

[0014] In the present invention, the primary hydroxyl polyol of component B is selected from polyols having 2 to 20 carbon atoms, and the hydroxyl groups on the polyols are all primary hydroxyl groups; in some specific embodiments, the component B is selected from one or more of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, dodecanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, glycerol, and pentaerythritol; in some more preferred embodiments, the component B is selected from one or more of 1,4-butanediol and 1,6-hexanediol.

[0015] In the present invention, the non-primary hydroxyl sulfur-containing polyol of component C is selected from one or more of 1,1-dithiodipropan-2-ol, 3,3-dithiodibutan-2-ol, 1,1-trithiodibutan-2-ol, 4,5-dihydroxy-1,2-dithiane, 3,4-dihydroxy-1,2-dithiane, and 1,2,7,8-tetrahydroxy-4,5,10,11-tetrathiocyclododecane; preferably, the component C is 1,1-dithiodipropan-2-ol.

[0016] Among them, compared with primary hydroxyl polyols, secondary hydroxyl and tertiary hydroxyl polyols have lower reactivity. Therefore, when preparing polyester polyols, it is easier to form polyester polyols with secondary hydroxyl or tertiary hydroxyl groups at the end.

[0017] The acid value of the polyester polyol in the present invention is 0.01-10.00 mg KOH / g, and the hydroxyl value is 10-200 mg KOH / g; in some preferred embodiments, the acid value of the polyester polyol is 0.03-5.00 mg KOH / g, and the hydroxyl value of the polyester polyol is 30-150 mg KOH / g; in some more preferred embodiments, the acid value of the polyester polyol is 0.05-2.00 mg KOH / g, and the hydroxyl value of the polyester polyol is 56-112 mg KOH / g.

[0018] On the other hand, the present invention also provides a method for preparing a polyester polyol, comprising the following steps: 1) in the presence of an inert gas, mixing the component A and the component B, and reacting at 140-160° C. for 0.5 h-1.5 h; 2) heating to 170-180° C. for 0.5 h-1.0 h, adding component C, and continuing to react for 0.5-1.0 h; 3) heating to 210-230° C., optionally adding a catalyst for reaction, and then continuing to react under vacuum (e.g., -0.09 MPa) until the acid value of the system is 0.01-10.00 mg KOH / g and the hydroxyl value is 10-200 mg KOH / g, to obtain the polyester polyol.

[0019] In the polyester polyol provided by the present invention, the amount of the catalyst is 0-500 ppm, preferably 40-300 ppm, based on the total mass of the component A), the component B) and the component C).

[0020] In some specific embodiments, the catalyst is selected from one or more of a titanium catalyst, a tin catalyst or an antimony catalyst; the titanium catalyst is selected from n-butyl titanate, tetraisopropyl titanate or titanium dioxide; the tin catalyst is selected from dibutyltin dilaurate, stannous octoate or stannous chloride; the antimony catalyst is selected from antimony acetate, antimony trioxide or antimony glycol; in some preferred embodiments, the catalyst uses a titanium catalyst, more preferably n-butyl titanate or tetraisopropyl titanate.

[0021] In another aspect, the present invention further provides a two-component polyurethane adhesive, wherein the polyurethane adhesive is composed of the following components:

[0022] Main agent: low-reactivity polyester polyol;

[0023] Curing agent: polyisocyanate compound.

[0024] In the present invention, the mass ratio of the low-reactivity polyester polyol to the polyisocyanate compound in the two-component polyurethane adhesive is 1:0.1-2.

[0025] In the present invention, the polyisocyanate compound is selected from one or more of polymethylene polyphenyl isocyanate (PAPI), TDI trimer, HDI trimer, HDI biuret, IPDI trimer, TDI-TMP adduct, TDI-glycerol adduct, triphenylmethane triisocyanate (TTI), tri(4-phenylisocyanate) thiophosphate and dimethyltriphenylmethane tetraisocyanate (JQ-5); more preferably one or more of TDI trimer or TDI-TMP adduct.

[0026] The present invention has the following beneficial effects:

[0027] 1) The present invention uses a sulfur-containing polyol having a secondary hydroxyl group or a tertiary hydroxyl group at the end to prepare a polyester polyol containing a portion of secondary hydroxyl groups or tertiary hydroxyl groups at the end, thereby reducing its reaction rate with an isocyanate monomer;

[0028] 2) The present invention can effectively increase the proportion of terminal secondary hydroxyl groups or tertiary hydroxyl groups by adding secondary hydroxyl or tertiary hydroxyl polyols in the later stage of the experiment;

[0029] 3) The reaction rate between the polyester polyol and the isocyanate compound provided by the present invention is moderate, and the curing time and the operable time of the two-component adhesive can be adjusted;

[0030] 4) The two-component polyurethane adhesive prepared using the polyester polyol provided by the present invention can be wiped with a GSH solution, thereby breaking the disulfide bonds, enhancing the crosslinking degree and hydrophilicity of the adhesive, and making it easier to clean. DETAILED DESCRIPTION

[0031] In order to better understand the technical solution of the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0032] The raw materials used in the following examples and comparative examples are all commercial chemicals.

[0033] The product performance in the embodiments and comparative examples of the present invention was measured using the following method:

[0034] Determination of acid value: refer to chemical industry standard HG / T 2708-1995;

[0035] Determination of hydroxyl value: refer to chemical industry standard HG / T 2709-1995;

[0036] The test method for the reactivity of polyester polyols refers to HG / T 2707-95 and is optimized:

[0037] formula:

[0038] Polyester polyol: 100g;

[0039] (where R is the isocyanate index and OH is the hydroxyl value of the polyester polyol);

[0040] Experimental steps: Place the weighed polyester polyol and MDI in a 70°C oven at a constant temperature for 2 hours, pour MDI into the polyester polyol, start timing, stir at 700r / min for 1 minute, and then use a viscometer to test the viscosity of the system until the viscosity reaches 200,000cP, stop timing, and record the time as T. The longer the time T, the lower the reaction activity of the polyester polyol.

[0041] The peel and removal properties of polyurethane adhesives are evaluated by:

[0042] Solvent wiping resistance test: The 316L stainless steel substrate coated with polyurethane adhesive was immersed in a 10mM reduced glutathione solution (GSH). After 30 minutes, the wiping characteristics of the adhesive were tested according to the reference standard GB / T23989-2009. Acetone was selected as the solvent.

[0043] Examples 1-4 are preparations of low-activity polyester polyols

[0044] Example 1

[0045] Preparation of polyester polyol A

[0046] Mix 11.81kg of succinic acid and 10.36kg of 1,4-butanediol evenly, raise the temperature to 150℃ and keep the temperature constant for 1.0h; continue to raise the temperature to 175℃ and keep the temperature constant for 1.0h; add 3.76kg of 1,1-dithiodipropane-2-ol and react for 1.0h; raise the temperature to 220℃, add 2.59g of tetraisopropyl titanate and react for 1.0h, open the vacuum to -0.090MPa, remove the reaction product water and excess alcohol monomer, and when the acid value and hydroxyl value are qualified, cool and discharge the material to obtain polyester polyol A with an acid value of 0.01mg KOH / g and a hydroxyl value of 56.1mg KOH / g.

[0047] Example 2

[0048] Preparation of polyester polyol B

[0049] Mix 10.01kg of succinic anhydride and 9.01kg of 1,4-butanediol evenly, raise the temperature to 140℃ and keep the temperature constant for 1.5h; continue to raise the temperature to 180℃ and keep the temperature constant for 0.5h; add 6.01kg of 1,1-dipropylene glycol-2-ol and react for 1.0h; raise the temperature to 230℃, add 1.00g of tetraisopropyl titanate and react for 0.5h, open the vacuum to -0.090MPa, remove the reaction product water and excess alcohol monomer, and when the acid value and hydroxyl value are qualified, cool and discharge the material to obtain polyester polyol B with an acid value of 0.1mg KOH / g and a hydroxyl value of 149.6mg KOH / g.

[0050] Example 3

[0051] Preparation of Polyester Polyol C

[0052] 14.61 kg of adipic acid and 15.36 kg of 1,6-hexanediol were mixed evenly, and the temperature was raised to 160°C and kept constant for 0.5 h; the temperature was further raised to 180°C and the reaction was kept constant for 0.75 h; 1.50 kg of 1,1-dipropylene dithioate was added and the reaction was continued for 0.75 h; the temperature was raised to 210°C, 5.35 g of n-butyl titanate was added and the reaction was continued for 0.75 h, and the vacuum was opened to -0.090 MPa to remove the reaction product water and excess alcohol monomer. When the acid value and hydroxyl value were qualified, the temperature was lowered and the material was discharged to obtain polyester polyol C with an acid value of 2.5 mg KOH / g and a hydroxyl value of 37.4 mg KOH / g.

[0053] Example 4

[0054] Preparation of polyester polyol D

[0055] 14.61 kg of adipic acid and 10.64 kg of 1,6-hexanediol were mixed evenly, and the temperature was raised to 145°C and kept constant for 1.5 hours; the temperature was further raised to 170°C and the reaction was kept constant for 0.75 hours; 7.51 kg of 1,1-dipropylene glycol-2-ol was added and the reaction was continued for 0.50 hours; the temperature was raised to 210°C, 9.83 g of n-butyl titanate was added and the reaction was continued for 0.75 hours, and the vacuum was opened to -0.090 MPa to remove the reaction product water and excess alcohol monomers. When the acid value and hydroxyl value were qualified, the temperature was lowered and the material was discharged to obtain polyester polyol D, whose acid value was 10.0 mg KOH / g and hydroxyl value was 11.2 mg KOH / g.

[0056] Comparative Examples 1-5 are preparations of conventional polyester polyols

[0057] Comparative Example 1

[0058] Preparation of polyester polyol E

[0059] 11.81 kg of succinic acid and 10.36 kg of 1,4-butanediol were mixed evenly, and the temperature was raised to 150°C and kept constant for 1.0 h; the temperature was further raised to 175°C and the reaction was continued at the constant temperature for 1.0 h; the temperature was raised to 220°C, 2.22 g of tetraisopropyl titanate was added, and the reaction was continued for 1.0 h. The vacuum was opened to -0.090 MPa to remove the reaction product water and excess alcohol monomer. When the acid value and hydroxyl value were qualified, the temperature was lowered and the material was discharged to obtain polyester polyol E with an acid value of 0.01 mg KOH / g and a hydroxyl value of 56.1 mg KOH / g.

[0060] Comparative Example 2

[0061] Preparation of polyester polyol F

[0062] Mix 10.01 kg of succinic anhydride and 9.01 kg of 1,4-butanediol evenly, raise the temperature to 150°C and keep the temperature constant for 1.0 h; continue to raise the temperature to 175°C and react at the constant temperature for 1.0 h; raise the temperature to 220°C, add 1.90 g of tetraisopropyl titanate, react for 1.0 h, open the vacuum to -0.090 MPa, remove the reaction product water and excess alcohol monomer, and when the acid value and hydroxyl value are qualified, cool the material and obtain polyester polyol F with an acid value of 0.1 mg KOH / g and a hydroxyl value of 149.6 mg KOH / g.

[0063] Comparative Example 3

[0064] Preparation of polyester polyol G

[0065] Mix 11.81kg of succinic acid and 10.36kg of 1,4-butanediol evenly, raise the temperature to 150℃ and keep the temperature constant for 1.0h; continue to raise the temperature to 175℃ and keep the temperature constant for 1.0h; add 3.16kg of 1,1-dithiodimethanol and react for 1.0h; raise the temperature to 220℃, add 2.53g of tetraisopropyl titanate and react for 1.0h, open the vacuum to -0.090MPa, remove the reaction product water and excess alcohol monomer, and when the acid value and hydroxyl value are qualified, cool and discharge the material to obtain polyester polyol G with an acid value of 0.01mg KOH / g and a hydroxyl value of 56.1mg KOH / g.

[0066] Application Examples 1-10

[0067] Preparation of two-component polyurethane adhesive

[0068] The low-activity polyester polyol and the polyisocyanate compound are mixed evenly according to the proportion, and the bubbles are removed. The adhesive is evenly coated on the surface of the PVC substrate, and the curing time of the polyurethane adhesive is recorded.

[0069] Table Application Example 1-10 Formula of Thermoplastic Polyurethane Elastomer

[0070]

[0071]

[0072] Performance Testing

[0073] Reactivity of polyester polyols

[0074] The reactivity of the polyester polyols of the examples and comparative examples was tested according to the above method, and the results are shown in the following table. As can be seen from the table, the time for the viscosity of the polyester polyol prepared in the examples and the MDI reaction system to reach 20000 cP is longer than that of the polyester polyol of the comparative example, indicating that the reaction rate of the polyester polyol prepared in the examples and MDI is slower; at the same time, the reactivity of the polyester polyol prepared using the sulfur-containing polyol with primary hydroxyl groups is also higher than that of the polyester polyol prepared using the non-primary hydroxyl polyol. In summary, it can be explained that the introduction of non-primary hydroxyl polyols can effectively reduce the reactivity of polyester polyols.

[0075] Table 4. Reactivity of polyester polyols prepared in Examples and Comparative Examples

[0076]

[0077] Two-component polyurethane adhesive properties

[0078] The curing time and easy-to-clean characteristics of the two-component polyurethane adhesive prepared using the polyester polyols of the examples and comparative examples are shown in the following table, where the polyol raw materials of PU-A to PU-D are the low-activity polyester polyols of the present invention. It can be seen from the table that the two-component adhesive prepared using the low-activity polyester polyols of the present invention has a long curing time at room temperature and a long operable time, indicating that the polyester polyol prepared using the non-primary hydroxyl sulfur-containing polyol has a low reaction activity; at the same time, the comparison data shows that the polyurethane adhesive prepared using the sulfur-containing polyester polyol prepared by the present invention is easy to clean after being treated with GSH, which is mainly because the disulfide bonds can be broken under the action of GSH to form thiol groups, so that the cross-linked network of the adhesive is partially destroyed and easier to clean.

[0079] Table 2 Properties of polyurethane adhesives prepared in Examples and Comparative Examples

[0080]

Claims

1. A low-reactivity polyester polyol prepared from the following components: A) dibasic acid / anhydride: 100 parts by mole; B) primary hydroxyl polyol: 90-150 mol parts; C) non-primary hydroxyl sulfur-containing polyol: 1-50 mol parts; The non-primary hydroxyl sulfur-containing polyol of component C is selected from one or more of 1,1-dithiodipropane-2-ol, 3,3-dithiodibutane-2-ol, 4,5-dihydroxy-1,2-dithiane, 3,4-dihydroxy-1,2-dithiane, and 1,2,7,8-tetrahydroxy-4,5,10,11-tetrathiocyclododecane; The preparation method of the low-reactivity polyester polyol comprises the following steps: 1) in the presence of an inert gas, mixing the component A and the component B, and reacting at 140-160° C. for 0.5 h-1.5 h; 2) heating to 170-180° C. for 0.5 h-1.0 h, adding component C, and continuing to react for 0.5-1.0 h; 3) heating to 210-230° C., optionally adding a catalyst for reaction, and then continuing to react under vacuum until the acid value of the system is 0.01-10.00 mg KOH / g and the hydroxyl value is 10-200 mg KOH / g, thereby obtaining the polyester polyol.

2. The low-reactivity polyester polyol according to claim 1, characterized in that: A) dibasic acid / anhydride: 100 parts by mole; B) primary hydroxyl polyol: 100-130 mol parts; C) Non-primary hydroxyl sulfur-containing polyol: 10-40 molar parts.

3. The low-reactivity polyester polyol according to claim 1, characterized in that: The dibasic acid in the component A is selected from aliphatic dicarboxylic acids or aromatic dicarboxylic acids having 2 to 20 carbon atoms, and the acid anhydride is selected from aliphatic acid anhydrides or aromatic acid anhydrides having 4 to 20 carbon atoms.

4. The low-reactivity polyester polyol according to claim 3, characterized in that: The dibasic acid is selected from one or more of succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, furandicarboxylic acid, phthalic acid, isophthalic acid or terephthalic acid; the acid anhydride is selected from one or more of succinic anhydride, glutaric anhydride, adipic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride or phthalic anhydride.

5. The low-reactivity polyester polyol according to any one of claims 1 to 4, characterized in that: The primary hydroxyl polyol of component B is selected from polyols having 2 to 20 carbon atoms, and all hydroxyl groups on the polyols are primary hydroxyl groups.

6. The low-reactivity polyester polyol according to claim 5, characterized in that: The component B is selected from one or more of ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,6-hexanediol, dodecanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, glycerol, and pentaerythritol.

7. The low-reactivity polyester polyol according to any one of claims 1 to 4, characterized in that: The component C is 1,1-dipropylene glycol-2-dithioate.

8. The low-reactivity polyester polyol according to any one of claims 1 to 4, characterized in that: The polyester polyol has an acid value of 0.01-10.00 mg KOH / g and a hydroxyl value of 10-200 mg KOH / g.

9. The low-reactivity polyester polyol according to claim 8, characterized in that: The acid value of the polyester polyol is 0.03-5.00 mg KOH / g, and the hydroxyl value of the polyester polyol is 30-150 mg KOH / g.

10. The low-reactivity polyester polyol according to claim 8, characterized in that: The acid value of the polyester polyol is 0.05-2.00 mg KOH / g, and the hydroxyl value of the polyester polyol is 56-112 mg KOH / g.

11. The low-reactivity polyester polyol according to any one of claims 1 to 4, characterized in that: The amount of the catalyst used is 0-500 ppm based on the total weight of the component A), the component B) and the component C).

12. The low-reactivity polyester polyol according to claim 11, characterized in that: The amount of the catalyst used is 40-300 ppm based on the total weight of the component A), the component B) and the component C).

13. The low-reactivity polyester polyol according to any one of claims 1 to 4, characterized in that: The catalyst is selected from one or more of titanium catalysts, tin catalysts or antimony catalysts; the titanium catalyst is selected from n-butyl titanate, tetraisopropyl titanate or titanium dioxide; the tin catalyst is selected from dibutyltin dilaurate, stannous octoate or stannous chloride; the antimony catalyst is selected from antimony acetate, antimony trioxide or ethylene glycol antimony.

14. A two-component polyurethane adhesive, the polyurethane adhesive consisting of the following components: Main agent: a low-reactivity polyester polyol as described in any one of claims 1 to 13; Curing agent: polyisocyanate compound.

15. The two-component polyurethane adhesive according to claim 14, characterized in that: The mass ratio of the low-reactivity polyester polyol to the polyisocyanate compound in the two-component polyurethane adhesive is 1:0.1-2.

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