Polyurethane combined polyether with high heat resistance and low shrinkage and preparation method thereof

Abstract

The invention discloses high-heat-resistance low-shrinkage polyurethane combined polyether and a preparation method thereof, and belongs to the technical field of polyurethane materials. According to the technical scheme, the flame-retardant polyurethane foam material is prepared from the following raw materials in parts by weight: 60 to 85 parts of polyol, 5 to 15 parts of a cross-linking agent, 0.5 to 3 parts of a catalyst, 1 to 4 parts of a foam stabilizer, 3 to 10 parts of a flame retardant, 1 to 5 parts of an anti-shrinking agent and 0.2 to 1 part of an antioxidant. The polyol is a compound system of polyether polyol and polyester polyol, the polyether polyol accounts for 60-80 wt% of the polyol component, and the polyester polyol accounts for 20-40 wt% of the polyol component. According to the invention, by optimizing the synergistic ratio of the polyol system and the functional auxiliary agent, the heat resistance and the low shrinkage are synchronously improved, and the comprehensive mechanical properties of the material are ensured at the same time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane materials, and particularly relates to a high-heat-resistance and low-shrinkage polyurethane combined polyether and a preparation method thereof. BACKGROUND

[0002] Polyurethane materials are widely used in the fields of building, automobile, electronics, furniture and the like due to their excellent heat preservation and insulation, mechanical properties and forming processability. The combined polyether is one of the core raw materials of the polyurethane material, and the performance thereof directly determines the quality of the final polyurethane product. With the expansion of application scenarios, especially the increasing application demand in high-temperature environments, the existing polyurethane combined polyether has the problems of insufficient heat resistance and large shrinkage under high temperature.

[0003] In the prior art, in order to improve the heat resistance of the polyurethane, the crosslinking density is usually increased or heat-resistant fillers are added, but this often leads to an increase in material brittleness and an increase in processing difficulty; and the method for reducing the shrinkage rate is mostly dependent on adjusting the foaming process, and the effect is limited and the stability is poor. Therefore, developing a polyurethane combined polyether with high heat resistance and low shrinkage and balanced mechanical properties has become a technical problem to be solved in the field. SUMMARY

[0004] The application provides a high-heat-resistance and low-shrinkage polyurethane combined polyether and a preparation method thereof, and the heat resistance and low shrinkage are simultaneously improved by optimizing the synergistic ratio of the polyol system and the functional additives, while the comprehensive mechanical properties of the material are ensured.

[0005] The technical scheme of the application is as follows: In a first aspect, a high-heat-resistance and low-shrinkage polyurethane combined polyether is disclosed, and the raw materials include the following components in parts by weight: 60-85 parts of polyol, 5-15 parts of crosslinking agent, 0.5-3 parts of catalyst, 1-4 parts of foam stabilizer, 3-10 parts of flame retardant, 1-5 parts of anti-shrinkage agent, and 0.2-1 part of antioxidant; The polyol is a compounded system of polyether polyol and polyester polyol, the polyether polyol has good flexibility and processability, the polyester polyol can improve the heat resistance and mechanical strength of the material, and the balance between flexibility and heat resistance can be achieved by compounding the two in proportion. The polyether polyol accounts for 60-80 wt% of the polyol component, and the polyester polyol accounts for 20-40 wt% of the polyol component; the polyether polyol is glycerol-initiated epoxy propane-epoxy ethane copolymer polyether, and the hydroxyl value is 350-450 mgKOH / g; the polyester polyol is adipic acid-ethylene glycol / propylene glycol copolymer polyester, and the hydroxyl value is 280-380 mgKOH / g.

[0006] Preferably, the cross-linking agent is compounded by trimethylolpropane and diethanolamine in a weight ratio of 2:1, trimethylolpropane is a trihydric alcohol cross-linking agent, which can significantly increase the cross-linking density; diethanolamine as a nitrogen-containing cross-linking agent can not only increase the cross-linking point, but also react with isocyanate to form urea bond, further improving the heat resistance.

[0007] Preferably, the catalyst is a compounded system of delayed amine catalyst and organic tin catalyst, with a weight ratio of 3:1; the delayed amine catalyst is N,N-dimethylcyclohexylamine, and the organic tin catalyst is dibutyltin dilaurate; the delayed amine catalyst can avoid the uneven cell caused by too fast reaction, and the organic tin catalyst can efficiently catalyze the reaction of isocyanate and hydroxyl, both of which can ensure the smooth reaction and improve the structure density of the product.

[0008] Preferably, the foam stabilizer is an organic silicon surfactant, model DC-193, which can effectively reduce the surface tension of the system and improve the cell structure; the flame retardant is compounded by triphenyl phosphate and aluminum hydroxide in a weight ratio of 1:2, which has both gas phase and condensed phase flame retardant effects, and improves the safety performance of the material; the anti-shrinkage agent is polymethyl methacrylate micro powder with a particle size of 5-10 μm, which matches the cell structure and can fill the gap between cells to inhibit shrinkage; the antioxidant is hindered phenolic antioxidant 1010, which can delay the thermal oxidative aging of the material and prolong the service life.

[0009] Preferably, the preparation method of the polyether polyol comprises the following steps: 1) feeding and nitrogen replacement: vacuum suction of glycerol, trimethylolpropane, sucrose, potassium hydroxide and silicone oil into the polymerization kettle, and nitrogen replacement for three times; 2) temperature rising copolymerization: temperature rising to 70-80℃, adding 30% of the total amount of propylene oxide and ethylene oxide, controlling the reaction temperature at 85-87℃, and the pressure ≤0.3MPa; 3) curing and dehydration: curing for 3-4h under the condition of-0.15~-0.2MPa, and temperature rising and dehydration to moisture <0.3%; 4) secondary polymerization: adding the remaining propylene oxide and ethylene oxide, controlling the temperature at 105-110℃, and curing for 3-3.5h under the condition of-0.15MPa; 5) neutralization and drying: temperature lowering to 85-90℃, adding phosphoric acid and water for neutralization to pH 5.0-8.0, and dehydrating and drying to obtain the polyether polyol; The weight parts of each raw material are as follows: glycerol 40-50 parts trimethylolpropane 40-50 parts sucrose 15-20 parts potassium hydroxide 10-18 parts 10-20 parts silicone oil 30-40 parts of propylene oxide 30-40 parts of ethylene oxide.

[0010] Preferably, the method for preparing the polyester polyol includes the following steps: 1) Esterification reaction: Polyol and dicarboxylic acid are added to the reactor at a molar ratio of 1:1.05 and esterification reaction is carried out at 140-200℃. The top temperature of the fractionation column is controlled at 100-102℃, and the by-product water is removed by distillation under normal pressure. When the acid value drops to 20-30 mg KOH / g, the temperature is raised to 200-230℃ and held for 1-2 hours. The polyol is ethylene glycol or propylene glycol, and the diacid is adipic acid; 2) Polycondensation reaction: Vacuum is drawn and the vacuum degree is gradually increased to -0.08MPa. The pressure is reduced to remove trace amounts of water and excess diol compounds, so that the reaction proceeds in the direction of generating low acid value polyester polyol. The reaction temperature is controlled at 200-230℃ and the reaction time is 2-4h. The reaction is terminated when the acid value is ≤3mg KOH / g and the hydroxyl value reaches the target value.

[0011] Secondly, a method for preparing the aforementioned high heat-resistant, low-shrinkage polyurethane composite polyether is disclosed, comprising the following steps: 1) Add the polyol to the reactor, heat to 60-70℃, stir at 300-500 r / min, and keep stirring for 25-35 min; 2) Then add the crosslinking agent, anti-shrinkage agent and antioxidant in sequence, maintain the temperature at 60-70℃, and stir for 60-70 minutes to ensure that the materials are fully dispersed; 3) Cool down to 40-50℃, add catalyst, foam stabilizer and flame retardant, stir for 45-60min, and adjust the stirring speed to 600-800r / min; 4) After stirring, perform vacuum degassing treatment with a vacuum degree of -0.08 to -0.09 MPa and a degassing time of 30-40 min; 5) After degassing, cool to room temperature, filter, and seal in packaging to obtain high heat resistance and low shrinkage polyurethane composite polyether.

[0012] Preferably, the heating rate in step 1) is less than 8°C / h to avoid local overheating caused by excessively rapid heating. Step 1) is carried out under nitrogen protection to prevent the raw materials from oxidizing upon contact with air.

[0013] Preferably, in step 2), a crosslinking agent is first added to the reactor in step 1), and the mixture is stirred at a speed of 300-500 r / min for 15-20 min until homogeneous. Then, an anti-shrinkage agent and an antioxidant are added, and the stirring speed is increased to 550-560 r / min. The stirring is continued for 60-70 min. The anti-shrinkage agent is a pre-treated anti-shrinkage agent, specifically dehydrated at a low temperature of 40-60℃ for 2.5 h. This treatment can reduce the amount of anti-shrinkage agent used. Without pretreatment, the activity of the polyether polyol will be reduced.

[0014] Preferably, in step 3), the cooling rate is less than 8℃ / h. First, the temperature is lowered to 40-50℃, the catalyst is added to the reactor, and the stirring speed is 300-500r / min for 15-20min to mix evenly. Then, the foam stabilizer and flame retardant are added, the stirring speed is increased to 600-800r / min, and the stirring is carried out for 45-60min.

[0015] Compared with the prior art, the present invention has the following advantages: 1. This invention optimizes the blending of polyether polyol and polyester polyol, combined with the synergistic effect of specific crosslinking agents and anti-shrinkage agents, to achieve a heat distortion temperature of 120-140℃ and a room temperature shrinkage rate of ≤0.3% for polyurethane products. The heat resistance and low shrinkage are significantly superior to existing technologies.

[0016] 2. A compound catalyst system is used to ensure a stable reaction, resulting in products with uniform pores, dense structure, tensile strength ≥3.5MPa, elongation at break ≥150%, and excellent comprehensive mechanical properties.

[0017] 3. The preparation process is simple, the raw materials are readily available, no special equipment is required, and the production cost is controllable. It can be widely used in fields with high requirements for heat resistance and dimensional stability, such as building insulation, automotive interiors, and electronic packaging, and has significant industrial application value. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions will be clearly and completely described below in conjunction with the embodiments of this invention. The invention will be further explained below in conjunction with the embodiments and comparative examples. Unless otherwise specified, the process methods used in the embodiments and comparative examples are conventional methods in the art. The parts involved in the raw materials in the embodiments and comparative examples are all parts by mass.

[0019] The preparation methods of the polyether polyol and polyester polyol in the examples are as follows: The method for preparing the polyether polyol includes the following steps: 1) Feeding and nitrogen purging: Glycerin (42 parts), trimethylolpropane (48 parts), sucrose (15 parts), potassium hydroxide (13.5 parts) and silicone oil (16 parts) are vacuum-introduced into the polymerization reactor, and nitrogen purging is performed three times; 2) Heating copolymerization: Heat to 70℃, add 30% of the total amount of propylene oxide (35 parts) and ethylene oxide (35 parts), that is, add propylene oxide (10.5 parts) and ethylene oxide (10.5 parts). Control the reaction temperature at 85℃ and the pressure at 0.3MPa. 3) Curing and dehydration: Curing at -0.2 MPa for 3 hours, then heating and dehydrating to a moisture content of 0.2%; 4) Secondary polymerization: Add the remaining propylene oxide and ethylene oxide, control the temperature at 105℃, and mature for 3 hours under -0.15MPa conditions; 5) Neutralization and drying: Cool to 85℃, add phosphoric acid and water for neutralization, neutralize pH to 6.0, dehydrate and dry to obtain polyether polyol with hydroxyl value of 400mgKOH / g.

[0020] The preparation method of the polyester polyol includes the following steps: 1) Esterification reaction: Ethylene glycol and adipic acid are added to the reactor at a molar ratio of 1:1.05 and esterification reaction is carried out at 180℃. The temperature at the top of the fractionation column is controlled at 100℃. The by-product water generated is removed by atmospheric pressure. When the acid value drops to 25mg KOH / g, the temperature is raised to 200℃ and held for 1.5h.

[0021] 2) Polycondensation reaction: Vacuum is drawn and gradually increased to -0.08 MPa to remove trace amounts of water and excess diol compounds, directing the reaction towards the formation of low-acid-value polyester polyols. The reaction temperature is controlled at 200℃, and the reaction time is 3 hours. The reaction is terminated when the acid value is ≤3 mg KOH / g and the hydroxyl value reaches the target value of 320 mg KOH / g, yielding polyester polyols.

[0022] Example 1 The high heat-resistant, low-shrinkage polyurethane composite polyether comprises the following components by weight: 50 parts polyether polyol, 20 parts polyester polyol, 6 parts trimethylolpropane (crosslinking agent), 3 parts diethanolamine (crosslinking agent), 1.2 parts N,N-dimethylcyclohexylamine (delayed amine catalyst), 0.4 parts dibutyltin dilaurate (organotin catalyst), 2 parts DC-193 (foam stabilizer), 2 parts triphenyl phosphate (flame retardant), 4 parts aluminum hydroxide (flame retardant), 3 parts polymethyl methacrylate micropowder (anti-shrinkage agent, micropowder particle size of 5μm), and 0.5 parts antioxidant 1010.

[0023] The specific preparation method is as follows: (1) Under nitrogen protection, polyether polyol and polyester polyol were added to the reactor, heated to 65°C at a rate of 7°C / h, stirred at 300 r / min, and kept at the temperature for 30 min. (2) Add trimethylolpropane and diethanolamine, stir at 400 r / min for 18 min, then add polymethyl methacrylate micro powder and antioxidant 1010, stir at 65℃ and 550 r / min for 60 min; the anti-shrinkage agent polymethyl methacrylate micro powder has been treated, specifically by dehydration at 60℃ for 2.5 h. (3) Cool down to 45℃ at a rate of 7℃ / h, add N,N-dimethylcyclohexylamine and dibutyltin dilaurate, stir at 400r / min for 18min to mix evenly, then add DC-193 foam stabilizer, triphenyl phosphate and aluminum hydroxide, stir at 700r / min for 50min. (4) After stirring, vacuum degassing is performed at a vacuum degree of -0.085MPa for 30 minutes. (5) Cool to room temperature, filter and seal in packaging to obtain high heat resistance and low shrinkage polyurethane composite polyether.

[0024] Example 2 The high heat-resistant, low-shrinkage polyurethane composite polyether comprises the following components by weight: The composition includes 48 parts polyether polyol, 12 parts polyester polyol, 4 parts trimethylolpropane (crosslinking agent), 2 parts diethanolamine (crosslinking agent), 0.9 parts N,N-dimethylcyclohexylamine (delayed amine catalyst), 0.3 parts dibutyltin dilaurate (organotin catalyst), 1.5 parts DC-193 (foam stabilizer), 1 part triphenyl phosphate (flame retardant), 2 parts aluminum hydroxide (flame retardant), 2 parts polymethyl methacrylate micropowder (anti-shrinkage agent, micropowder particle size of 8μm), and 0.3 parts antioxidant 1010.

[0025] The specific preparation method is as follows: (1) Under nitrogen protection, polyether polyol and polyester polyol were added to the reactor, heated to 60°C at a rate of 6°C / h, stirred at 400 r / min, and kept at the temperature for 35 min. (2) Add trimethylolpropane and diethanolamine, stir at 300 r / min for 20 min, then add polymethyl methacrylate micro powder and antioxidant 1010, stir at 60℃ and 550 r / min for 70 min; the anti-shrinkage agent polymethyl methacrylate micro powder has been treated, specifically by dehydration at 60℃ for 2.5 h. (3) Cool down to 40℃ at a rate of 6℃ / h, add N,N-dimethylcyclohexylamine and dibutyltin dilaurate, stir at 300r / min for 20min to mix evenly, then add DC-193 foam stabilizer, triphenyl phosphate and aluminum hydroxide, stir at 600r / min for 60min; (4) After stirring, vacuum degassing is performed at a vacuum degree of -0.08MPa for 30 minutes. (5) Cool to room temperature, filter and seal in packaging to obtain high heat resistance and low shrinkage polyurethane composite polyether.

[0026] Example 3 The high heat-resistant, low-shrinkage polyurethane composite polyether comprises the following components by weight: The composition includes 60 parts polyether polyol, 25 parts polyester polyol, 10 parts trimethylolpropane (crosslinking agent), 5 parts diethanolamine (crosslinking agent), 2.1 parts N,N-dimethylcyclohexylamine (delayed amine catalyst), 0.7 parts dibutyltin dilaurate (organotin catalyst), 4 parts DC-193 (foam stabilizer), 3 parts triphenyl phosphate (flame retardant), 6 parts aluminum hydroxide (flame retardant), 5 parts polymethyl methacrylate micropowder (anti-shrinkage agent, micropowder particle size of 10μm), and 1 part antioxidant 1010.

[0027] The specific preparation method is as follows: (1) Under nitrogen protection, polyether polyol and polyester polyol were added to the reactor, heated to 70°C at a rate of 7°C / h, stirred at 500 r / min, and kept at the temperature for 25 min. (2) Add trimethylolpropane and diethanolamine, stir at 500 r / min for 15 min, then add polymethyl methacrylate micro powder and antioxidant 1010, stir at 70℃ and 560 r / min for 60 min; the anti-shrinkage agent polymethyl methacrylate micro powder has been treated, specifically by dehydration at 60℃ for 2.5 h. (3) Cool down to 50℃ at a rate of 6℃ / h, add N,N-dimethylcyclohexylamine and dibutyltin dilaurate, stir at 500r / min for 15min until evenly mixed, then add DC-193 foam stabilizer, triphenyl phosphate and aluminum hydroxide, stir at 800r / min for 45min. (4) After stirring, vacuum degassing is performed at a vacuum degree of -0.09MPa for 30 minutes. (5) Cool to room temperature, filter and seal in packaging to obtain high heat resistance and low shrinkage polyurethane composite polyether.

[0028] Comparative Example 1 Unlike Example 1, no anti-shrinkage agent, polymethyl methacrylate micro powder, was added; the other raw materials and preparation methods were the same as in Example 1.

[0029] Comparative Example 2 Unlike Example 1, the polyol component is 70 parts of a single polyether polyol (hydroxyl value 400 mg KOH / g), and the remaining raw materials and preparation methods are the same as in Example 1.

[0030] Comparative Example 3 Unlike Example 1, the crosslinking agent was only 9 parts of trimethylolpropane (without diethanolamine), and the other raw materials and preparation methods were the same as in Example 1.

[0031] Comparative Example 4 Unlike Example 1, only 1.6 parts of N,N-dimethylcyclohexylamine were used as the catalyst (without adding organotin catalyst), and the remaining raw materials and preparation methods were the same as in Example 1.

[0032] Comparative Example 5 Unlike Example 1, polymethyl methacrylate micro powder, an anti-shrinkage agent, was added with a particle size of 15 μm. The other raw materials and preparation methods were the same as in Example 1.

[0033] Comparative Example 6 Unlike Example 1, the raw materials and preparation method were the same as in Example 1, consisting of 63 parts of polyether polyol (hydroxyl value 400 mg KOH / g) and 7 parts of polyester polyol (hydroxyl value 320 mg KOH / g).

[0034] The combined polyethers prepared in the examples and comparative examples were mixed with polymethylene polyphenyl polyisocyanate (MDI) at a weight ratio of 1:1.05 and foamed to obtain foamed products. The relevant performance tests of the foamed products are shown in Table 1.

[0035] The specific standards used in the test are as follows: Heat distortion temperature GB / T 1634.2-2019 "Determination of load distortion temperature of plastics - Part 2: Plastics and hard rubber"; Room temperature shrinkage rate GB / T 39818-2021 Determination of shrinkage rate of thermosetting molding materials in plastics; Tensile strength GB / T 1040.2-2022 "Determination of tensile properties of plastics - Part 2: Test conditions for molded and extruded plastics"; Elongation at break (GB / T 6344-2008) - Determination of tensile strength and elongation at break of flexible foam polymer materials.

[0036] Table 1 Performance Testing of Foamed Products

[0037] Examples 1-3 all exhibited excellent heat distortion temperature (125-133℃) and low shrinkage rate (≤0.28%), indicating that the present invention significantly improves the heat resistance and dimensional stability of the material through the synergistic effect of polyether / polyester polyol compound system, specific crosslinking agent combination and anti-shrinkage agent.

[0038] The shrinkage rate of Comparative Example 1 (without anti-shrinkage agent) increased significantly (0.95%), indicating that the anti-shrinkage agent plays a key role in inhibiting cell shrinkage.

[0039] The heat resistance of Comparative Example 2 (single polyether polyol) decreased significantly (105℃), indicating that the introduction of polyester polyol is crucial to improving heat resistance.

[0040] Comparative Example 3 (without diethanolamine) showed a decrease in both heat resistance and mechanical properties, indicating that diethanolamine, as a nitrogen-containing crosslinking agent, can not only increase the number of crosslinking points but also form urea bond structures, further improving heat resistance.

[0041] The decrease in tensile strength and elongation at break in Comparative Example 4 (without organotin catalyst) indicates that the combination system of organotin catalyst and amine catalyst plays an important role in promoting complete reaction and improving material density.

[0042] In Comparative Example 5, the shrinkage rate increased significantly (0.75%) as the particle size of the anti-shrinkage agent increased, indicating that the particle size of the anti-shrinkage agent has a significant effect on inhibiting foam shrinkage.

[0043] In Comparative Example 6, the polyether / polyester blend ratio was unbalanced, resulting in a decrease in room temperature shrinkage, tensile strength, and elongation at break. This indicates that the polyether / polyester blend ratio plays an important role in improving the dimensional stability and strength of the material.

[0044] In summary, this invention achieves a balanced improvement in heat resistance, low shrinkage, and mechanical properties through various technical means, including optimization of the polyol system, compounding of crosslinking agents and catalysts, and synergistic effects of functional additives. It has significant technological advancements and industrial application value.

Claims

1. A high heat-resistant, low-shrinkage polyurethane composite polyether, characterized in that, By weight, the raw materials comprise the following components: Polyol 60-85 parts, crosslinking agent 5-15 parts, catalyst 0.5-3 parts, foam stabilizer 1-4 parts, flame retardant 3-10 parts, anti-shrinkage agent 1-5 parts, antioxidant 0.2-1 parts; The polyol is a compound system of polyether polyol and polyester polyol, wherein the polyether polyol accounts for 60-80 wt% of the polyol component and the polyester polyol accounts for 20-40 wt% of the polyol component; the polyether polyol is a glycerol-based propylene oxide-ethylene oxide copolymer polyether with a hydroxyl value of 350-450 mg KOH / g; the polyester polyol is an adipic acid-ethylene glycol / propylene glycol copolymer polyester with a hydroxyl value of 280-380 mg KOH / g.

2. The high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 1, characterized in that, The crosslinking agent is a mixture of trimethylolpropane and diethanolamine in a weight ratio of 2:

1.

3. The high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 1, characterized in that, The catalyst is a composite system of a delayed amine catalyst and an organotin catalyst in a weight ratio of 3:1; the delayed amine catalyst is N,N-dimethylcyclohexylamine, and the organotin catalyst is dibutyltin dilaurate.

4. The high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 1, characterized in that, The foam stabilizer is an organosilicon surfactant, model DC-193; the flame retardant is a mixture of triphenyl phosphate and aluminum hydroxide in a weight ratio of 1:2; the anti-shrinkage agent is polymethyl methacrylate micro powder with a particle size of 5-10 μm; and the antioxidant is hindered phenolic antioxidant 1010.

5. The high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 1, characterized in that, The method for preparing the polyether polyol includes the following steps: 1) Feeding and nitrogen purging: Glycerol, trimethylolpropane, sucrose, potassium hydroxide and silicone oil are vacuum-inhaled into the polymerization reactor, and nitrogen purging is performed three times; 2) Heating copolymerization: Heat to 70-80℃, add 30% of the total amount of propylene oxide and ethylene oxide, control the reaction temperature at 85-87℃, and the pressure ≤0.3MPa; 3) Curing and dehydration: Curing at -0.15~-0.2MPa for 3-4 hours, then heating and dehydrating until the moisture content is <0.3%; 4) Secondary polymerization: Add the remaining propylene oxide and ethylene oxide, control the temperature at 105-110℃, and mature at -0.15MPa for 3-3.5h; 5) Neutralization and drying: Cool to 85-90℃, add phosphoric acid and water to neutralize to pH 5.0-8.0, dehydrate and dry to obtain polyether polyol; The specific weight proportions of the above raw materials are as follows: 40-50 parts glycerin 40-50 parts of trimethylolpropane 15-20 parts sucrose 10-18 parts of potassium hydroxide 10-20 parts silicone oil 30-40 parts of propylene oxide 30-40 parts of ethylene oxide.

6. The high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 1, characterized in that, The preparation method of the polyester polyol includes the following steps: 1) Esterification reaction: The polyol and the dicarboxylic acid are added to the reactor at a molar ratio of 1:1.05 and the esterification reaction is carried out at 140-200℃. The top temperature of the fractionation column is controlled at 100-102℃ and the by-product water generated is removed by distillation at atmospheric pressure. When the acid value drops to 20-30mgKOH / g, the temperature is raised to 200-230℃ and held for 1-2 hours. The polyol is ethylene glycol or propylene glycol, and the diacid is adipic acid; 2) Polycondensation reaction: Vacuum is drawn and the vacuum degree is gradually increased to -0.08MPa. The pressure is reduced to remove trace amounts of water and excess diol compounds, so that the reaction proceeds in the direction of generating low acid value polyester polyol. The reaction temperature is controlled at 200-230℃ and the reaction time is 2-4h. The reaction is terminated when the acid value is ≤3mg KOH / g and the hydroxyl value reaches the target value.

7. The method for preparing the high heat-resistant, low-shrinkage polyurethane composite polyether according to any one of claims 1-6, characterized in that, Includes the following steps: 1) Add the polyol to the reactor, heat to 60-70℃, stir at 300-500 r / min, and keep stirring for 25-35 min; 2) Then add the crosslinking agent, anti-shrinkage agent and antioxidant in sequence, maintain the temperature at 60-70℃, and stir for 60-70 minutes to ensure that the materials are fully dispersed; 3) Cool down to 40-50℃, add catalyst, foam stabilizer and flame retardant, stir for 45-60min, and adjust the stirring speed to 600-800r / min; 4) After stirring, perform vacuum degassing treatment with a vacuum degree of -0.08 to -0.09 MPa and a degassing time of 30-40 min; 5) After degassing, cool to room temperature, filter, and seal in packaging to obtain high heat resistance and low shrinkage polyurethane composite polyether.

8. The method for preparing the high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 7, characterized in that, In step 1), the heating rate is less than 8℃ / h, and step 1) is carried out under nitrogen protection.

9. The method for preparing the high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 7, characterized in that, In step 2), first add the crosslinking agent to the reaction vessel in step 1), stir at 300-500 r / min for 15-20 min to mix evenly, then add the anti-shrinkage agent and antioxidant, increase the speed to 550-560 r / min, and continue stirring for 60-70 min.

10. The method for preparing the high heat-resistant, low-shrinkage polyurethane composite polyether as described in claim 7, characterized in that, In step 3), if the cooling rate is less than 8℃ / h, first cool down to 40-50℃, add the catalyst to the reactor, stir at 300-500r / min for 15-20min to mix evenly, then add the foam stabilizer and flame retardant, increase the speed to 600-800r / min, and stir for 45-60min.

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