Low shrinkage rate, high resilience supercritical polyurethane foamed beads and preparation method thereof

Abstract

The present invention relates to the technical field of polyurethane production, specifically to low-shrinkage, high-resilience supercritical polyurethane foam beads and a preparation method thereof. By optimizing the synthesis method of polyester polyol, the dibasic acid is added separately. Adipic acid is first put into the reaction kettle and reacts with small molecule alcohol. After the reaction is completed, purified terephthalic acid is put into the reaction kettle for reaction, resulting in polyester polyol. If adipic acid and purified terephthalic acid exist repeatedly and crosswise in the polyol structure, the solubility of carbon dioxide will be significantly reduced, affecting the subsequent cell formation and cell structure, and a better surface effect cannot be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane production, specifically to low-shrinkage, high-resilience supercritical polyurethane foamed beads and a preparation method thereof. Background Art

[0002] ETPU, namely foamed TPU, full name "high-resilience lightweight thermoplastic polyurethane elastomer", is the foam particle with the largest elasticity in the current market. ETPU has the advantages of light weight, high elasticity, wear resistance, good low-temperature performance, environmental protection, etc., and is widely used in high-end sports equipment, automobiles, health care and other fields. By bionics, it greatly improves the comfort of human movement and riding, and has a broad market prospect. At present, the supercritical physical foaming process is mostly adopted, and the foaming agents are mainly carbon dioxide and nitrogen. Since supercritical carbon dioxide has a better plasticizing effect on TPU, it is widely used.

[0003] When using carbon dioxide as the foaming agent for supercritical foaming, since the ETPU matrix is still in the high-elastic state during the rapid pressure relief stage, the skeleton strength is relatively poor. At the same time, due to the large difference in the carbon dioxide concentration in the ETPU cell and the carbon dioxide concentration in the external atmosphere, the internal carbon dioxide will quickly diffuse outward, easily causing problems such as product shriveling and surface wrinkles. Patent CN 118546425 A mentions adding an additional pressure-holding and curing kettle in the foaming stage. After the first foaming is completed, it is cured in the pressure-holding and curing kettle. After the strength of the ETPU reaches the required level, it is then discharged for drying and packaging. This process greatly prolongs the entire foaming cycle.

[0004] By increasing the glass transition temperature (Tg) of TPU itself, after the foaming pressure is relieved, the ETPU can quickly enter the glass state from the high-elastic state, the molecular chain segments are frozen, the rigidity of the system skeleton is strengthened, the supportability is better, and the basic structure skeleton can be ensured not to be affected during the carbon dioxide diffusion and cell gas exchange, the shrinkage rate is reduced, and the resilience of the foamed beads is also improved. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the purpose of the present invention is to provide a low-shrinkage, high-resilience supercritical polyurethane foamed bead. By introducing a benzene ring structure into the soft segment of TPU, the glass transition temperature of TPU itself can be increased, and at the same time, the polarity of TPU is enhanced, keeping the product with better strength.

[0006] Another purpose of the present invention is to provide a preparation method of low-shrinkage, high-resilience supercritical polyurethane foamed beads. By optimizing the synthesis method of polyester polyol, the dibasic acid is added separately. Adipic acid is first put into the reaction kettle and reacts with small molecule alcohol. After the reaction is completed, purified terephthalic acid is then put into the reaction kettle for reaction, so as to obtain polyester polyol.

[0007] The present invention is implemented by the following technical solutions:

[0008] The preparation method of the low shrinkage rate and high resilience supercritical polyurethane foam beads includes the following steps:

[0009] (1) Add dibasic acid, diol and catalyst into the reactor, start stirring, under nitrogen protection, carry out esterification reaction at 200 - 210 °C for 2 - 3 h, then add purified terephthalic acid, and then carry out transesterification reaction at 220 - 230 °C under the condition of a pressure of 0.09 - 0.1 MPa to obtain polyester diol;

[0010] (2) Mix antioxidant, catalyst, light stabilizer and the polyester diol obtained in step (1) and heat to 130 - 150 °C, and mix evenly; heat isocyanate to 45 - 55 °C; heat chain extender to 45 - 55 °C; meter the heated raw materials and inject them into the extruder through a high - speed stirring head, the mixed materials are fully reacted and plasticized in the screw, and after granulation through an underwater cutting system, low shrinkage rate and high resilience supercritical polyurethane are obtained;

[0011] (3) Add low shrinkage rate and high resilience supercritical polyurethane and water according to a mass ratio of 1:2 into the autoclave, then introduce carbon dioxide fluid into the autoclave, heat up to 110 - 130 °C, with a pressure of 6 - 9 MPa, after reaching the set temperature and set pressure, directly release the pressure to atmospheric pressure or maintain for a certain time at the set temperature and set pressure and then release the pressure to atmospheric pressure, and dry to obtain low shrinkage rate and high resilience supercritical polyurethane foam beads;

[0012] The catalyst is one of organic bismuth catalysts, organic tin catalysts, and titanate catalysts;

[0013] The antioxidant is one or more of phenolic antioxidants, amine antioxidants, and phosphite antioxidants.

[0014] In step (1), the dosage of purified terephthalic acid is 5 - 10% of the sum of the mass of dibasic acid and purified terephthalic acid, the dosage of dibasic acid is 90 - 95% of the sum of the mass of dibasic acid and purified terephthalic acid, the dibasic acid is one or two of adipic acid and azelaic acid in any proportion, preferably adipic acid; the diol is one or several of ethylene glycol, 1,4 - butanediol, 1,2 - propanediol, 1,3 - propanediol in any proportion, preferably 1,4 - butanediol.

[0015] In step (2), the mass percentages of each raw material are:

[0016] Polyester diol 59% - 70%

[0017] Isocyanate 23% - 30%

[0018] Chain extender: 6% - 11%

[0019] Antioxidant: 0.1% - 0.3%

[0020] Light stabilizer: 0.1% - 0.8%

[0021] Catalyst: 0.008% - 0.05%.

[0022] For the polyester - type diol mentioned above, aliphatic aggregates exist, aromatic aggregates exist, and aliphatic and aromatic do not alternate, specifically as follows:

[0023] .

[0024] The isocyanate mentioned above is one of 4,4'-diphenylmethane diisocyanate and 1,6 - hexamethylene diisocyanate (HDI), and HDI is preferred.

[0025] The chain extender is one or both of 1,2 - propanediol and 1,4 - butanediol (BDO), and BDO is preferred.

[0026] The phenolic antioxidant is one of 1010 or 1076; the amine - type antioxidant is 445; the phosphite - type antioxidant is one of 168 or 626. The antioxidant is preferably 1010.

[0027] The light stabilizer is one of 944, 622, and LS - 144.

[0028] The organobismuth - type catalyst is catalyst DY - 20; the organotin - type catalyst is T - 12. The catalyst is preferably T - 12.

[0029] The low - shrinkage, high - resilience supercritical polyurethane foam beads described in the present invention are prepared by the preparation method of the low - shrinkage, high - resilience supercritical polyurethane foam beads mentioned above.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] (1) By introducing a benzene ring structure into the TPU soft segment, the present invention can increase the glass transition temperature of TPU itself, and at the same time enhance the polarity of TPU, maintaining better strength of the product. After the foaming pressure is released, it can quickly restore high skeletal strength to ensure that the product can resist the shrinkage stress caused by gas exchange.

[0032] (2) The present invention optimizes the synthesis method of polyester polyol. The dibasic acid is added separately. Adipic acid is first put into the reaction kettle and reacts with small molecule alcohol. After the reaction is completed, purified terephthalic acid is put into the reaction kettle for reaction, resulting in polyester polyol. If adipic acid and purified terephthalic acid exist repeatedly and crosswise in the polyol structure, the solubility of carbon dioxide will be significantly reduced, affecting the subsequent cell formation and cell structure, and a better surface effect cannot be obtained.

[0033] (3) The present invention optimizes the synthesis method of polyester polyol to obtain a polyol with a special structure. In this polyol, the aliphatic segments aggregate with each other, better providing the solubility of carbon dioxide and promoting the foaming effect. The aromatic segments aggregate with each other, increasing the glass transition temperature of the product and enhancing the strength of the product itself. If the aliphatic segments and aromatic segments appear alternately, the solubility of carbon dioxide will be greatly affected, resulting in poor foaming. Specific embodiments

[0034] To make the object and technical solution of the present invention clearer and more understandable, the present invention will be further described in detail.

[0035] Example 1

[0036] The low shrinkage rate, high resilience supercritical polyurethane foaming beads are made of the following raw materials in mass percentages:

[0037] Polyester diol: 69.63%

[0038] HDI: 23.38%

[0039] BDO: 6.45%

[0040] 1010: 0.2%

[0041] 622: 0.3%

[0042] T-12: 0.04%.

[0043] The molecular weight of the polyester diol is 1000.

[0044] The component ratio of terephthalic acid / adipic acid is 5% / 95%. The component of the diol is 1,4-butanediol.

[0045] Preparation process:

[0046] Add adipic acid, 1,4-butanediol and catalyst T-12 into the reactor, stir evenly, under nitrogen protection, carry out esterification reaction at 200 °C for 2 h, then add purified terephthalic acid, and then carry out transesterification reaction at 220 °C and a pressure of 0.09 MPa to obtain polyester diol;

[0047] Mix the polyester diol, 1010, T-12, and 622, heat them to 135°C, and mix them thoroughly; heat the HDI to 55°C; heat the BDO to 45°C; after accurately measuring the heated raw materials, inject them into the extruder through a high-speed stirring head. The mixed materials are fully reacted and plasticized in the screw, and then granulated through an underwater cutting system to obtain the final product.

[0048] The outflow temperature of the product obtained in Example 1 is 140°C. Add 1000 g of the above product and 2000 g of water into a 50 L reaction and foaming kettle at the same time. Then, introduce 400 g of carbon dioxide fluid into the autoclave, raise the temperature to 110°C, maintain the pressure at 9 MPa, quickly open the discharge valve of the autoclave, and quickly release the pressure to obtain low-shrinkage and high-resilience supercritical polyurethane foamed beads. The pressure release rate is 4 MPa / s. Discharge and dry.

[0049] Example 2

[0050] The low-shrinkage and high-resilience supercritical polyurethane foamed beads are made from the following raw materials by mass percentage:

[0051] Polyester diol: 59.67%

[0052] HDI: 29.28%

[0053] BDO: 10.51%

[0054] 1010: 0.2%

[0055] 622: 0.3%

[0056] T-12: 0.04%.

[0057] The molecular weight of the polyester diol is 1000.

[0058] Terephthalic acid / adipic acid is 10% / 90%. The diol component is 1,4-butanediol.

[0059] Preparation process:

[0060] Add adipic acid, 1,4-butanediol, and catalyst T-12 into the reactor, stir evenly, under nitrogen protection, carry out the esterification reaction at 200°C for 2 h, then add purified terephthalic acid, and then carry out the transesterification reaction at 230°C and a pressure of 0.1 MPa to obtain the polyester diol;

[0061] Mix the polyester diol, 1010, T-12, and 622, and heat them to 145°C, then mix them evenly; heat the HDI to 45°C; heat the BDO to 55°C; after accurately measuring the heated raw materials, inject them into the extruder through a high-speed stirring head. The mixed materials are fully reacted and plasticized in the screw, and then granulated through an underwater cutting system to obtain the final product.

[0062] The product obtained in Example 2 has an outflow temperature of 163°C. Add 1000 g of the above product and 2000 g of water into a 50 L reaction foaming kettle at the same time, then introduce 400 g of carbon dioxide fluid into the autoclave, heat it to 130°C, maintain the pressure at 9 MPa, quickly open the discharge valve of the autoclave, and quickly release the pressure to obtain low-shrinkage, high-elasticity supercritical polyurethane foaming beads. The pressure release rate is 4 MPa / s. Discharge and dry.

[0063] Example 3

[0064] The low-shrinkage, high-elasticity supercritical polyurethane foaming beads are made from the following raw materials in mass percentages:

[0065] Polyester diol: 60.67%

[0066] HDI: 28.82%

[0067] BDO: 9.97%

[0068] 1010: 0.2%

[0069] 622: 0.3%

[0070] T-12: 0.04%.

[0071] The molecular weight of the polyester diol is 1000.

[0072] The terephthalic acid component / adipic acid is 8% / 92%. The diol component is 1,4-butanediol.

[0073] Preparation process:

[0074] Add adipic acid, 1,4-butanediol, and catalyst T-12 into the reactor, stir evenly, under nitrogen protection, carry out the esterification reaction at 210°C for 3 h, then add refined terephthalic acid, and then carry out the transesterification reaction at 225°C under the condition of a pressure of 0.09 MPa to obtain the polyester diol;

[0075] The polyester diol, 1010, T-12, and 622 were mixed and heated to 135°C, and thoroughly mixed evenly; the HDI was heated to 50°C; the BDO was heated to 50°C; the heated raw materials were accurately metered and then injected into the extruder through a high-speed stirring head. The mixed materials were fully reacted and plasticized in the screw, and then granulated through an underwater cutting system to obtain the final product.

[0076] The product obtained in Example 3 had an outflow temperature of 155°C. 1000 g of the above product and 2000 g of water were simultaneously added into a 50 L reaction foaming kettle, and then 400 g of carbon dioxide fluid was introduced into the autoclave. The temperature was raised to 110°C, and the pressure was maintained at 6 MPa. The discharge valve of the autoclave was quickly opened, and the pressure was quickly released to obtain low shrinkage rate and high resilience supercritical polyurethane foamed beads, and the pressure release rate was 4 MPa / s. Then it was discharged and dried.

[0077] Comparative Example 1

[0078] The polyurethane foamed beads were made from the following raw materials in mass percentages:

[0079] Polyester diol: 69.63%

[0080] HDI: 23.38%

[0081] BDO: 6.45%

[0082] 1010: 0.2%

[0083] 622: 0.3%

[0084] T-12: 0.04%.

[0085] The molecular weight of the polyester diol described above was 1000.

[0086] The terephthalic acid component / adipic acid was 15% / 85%. The diol component was 1,4-butanediol.

[0087] Preparation process:

[0088] Adipic acid, 1,4-butanediol, and catalyst T-12 were added to the reactor and stirred evenly. Under nitrogen protection, an esterification reaction was carried out at 205°C for 2.5 h, and then purified terephthalic acid was added. Then, a transesterification reaction was carried out at 230°C and a pressure of 0.1 MPa to obtain the polyester diol;

[0089] The polyester diol, 1010, T-12, and 622 were mixed and heated to 135°C, and thoroughly mixed evenly; the HDI was heated to 55°C; the BDO was heated to 45°C; the heated raw materials were accurately metered and then injected into the extruder through a high-speed stirring head. The mixed materials were fully reacted and plasticized in the screw, and then granulated through an underwater cutting system to obtain the final product.

[0090] The outlet temperature of the product obtained in Comparative Example 1 was 140°C. 1000 g of the above product and 2000 g of water were simultaneously added into a 50 L reaction and foaming kettle. Then, 400 g of carbon dioxide fluid was introduced into the autoclave, and the temperature was raised to 110°C. While maintaining the pressure at 9 MPa, the discharge valve of the autoclave was quickly opened, and rapid pressure relief was carried out to obtain low-shrinkage, high-resilience supercritical polyurethane foamed beads. The pressure relief rate was 4 MPa / s. The beads were discharged and dried.

[0091] Comparative Example 2

[0092] The polyurethane foamed beads were made from raw materials in the following mass percentages:

[0093] Polyester diol: 59.67%

[0094] HDI: 29.28%

[0095] BDO: 10.51%

[0096] 1010: 0.2%

[0097] 622: 0.3%

[0098] T-12: 0.04%.

[0099] The molecular weight of the polyester diol described above was 1000.

[0100] Terephthalic acid / adipic acid was 0% / 100%. The diol component was 1,4-butanediol.

[0101] Preparation process:

[0102] Adipic acid, 1,4-butanediol, and catalyst T-12 were added to a reactor and stirred evenly. Under nitrogen protection, an esterification reaction was carried out at 200°C, and a transesterification reaction was carried out at 230°C under a pressure of 0.1 MPa to obtain polyester diol;

[0103] The polyester diol, 1010, T-12, and 622 were mixed and heated to 145°C and mixed evenly; HDI was heated to 45°C; BDO was heated to 55°C; the heated raw materials were accurately metered and then injected into an extruder through a high-speed stirring head. The mixed materials were fully reaction-plasticized in the screw and granulated through an underwater cutting system to obtain the final product.

[0104] The outlet temperature of the product obtained in Comparative Example 2 was 163°C. 1000 g of the above product and 2000 g of water were simultaneously added into a 50 L reaction and foaming kettle. Then, 400 g of carbon dioxide fluid was introduced into the autoclave, and the temperature was raised to 130°C. The pressure was maintained at 9 MPa. The discharge valve of the autoclave was quickly opened, and the pressure was quickly released to obtain low shrinkage rate and high resilience supercritical polyurethane foamed beads. The pressure release rate was 4 MPa / s. The obtained beads were quickly transferred to a pressure-holding kettle with a carbon dioxide concentration of 50% and a temperature of 30°C and left for 12 h, then discharged and dried.

[0105] Comparative Example 3

[0106] The polyurethane foamed beads were made from raw materials with the following mass percentages:

[0107] Polyester diol: 59.67%

[0108] HDI: 29.28%

[0109] BDO: 10.51%

[0110] 1010: 0.2%

[0111] 622: 0.3%

[0112] T-12: 0.04%.

[0113] The molecular weight of the polyester diol described was 1000.

[0114] The terephthalic acid component / adipic acid was 0% / 100%. The diol component was 1,4-butanediol.

[0115] Preparation process:

[0116] Adipic acid, 1,4-butanediol, and catalyst T-12 were added to the reactor, stirred evenly, and under nitrogen protection, an esterification reaction was carried out at 210°C, and a transesterification reaction was carried out at 230°C under a pressure of 0.09 MPa to obtain polyester diol;

[0117] The polyester diol, 1010, T-12, and 622 were mixed and heated to 135°C and mixed evenly; HDI was heated to 55°C; BDO was heated to 45°C; the heated raw materials were accurately metered and then injected into the extruder through a high-speed stirring head. The mixed materials were fully reacted and plasticized in the screw and granulated through an underwater cutting system to obtain the final product.

[0118] The outlet temperature of the product obtained in Comparative Example 3 was 163°C. 1000 g of the above product and 2000 g of water were simultaneously added into a 50 L reaction and foaming kettle. Then, 400 g of carbon dioxide fluid was introduced into the autoclave, and the temperature was raised to 130°C while maintaining the pressure at 6 MPa. The discharge valve of the autoclave was quickly opened, and the pressure was quickly released to obtain low-shrinkage, high-resilience supercritical polyurethane foamed beads, with a pressure release rate of 4 MPa / s.

[0119] After the beads were placed at room temperature for 2 days, tests were carried out: The main particle detection indexes in the examples and comparative examples were particle density, bulk density, ball-drop resilience, and whether there was shrinkage in appearance.

[0120] The test data of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1.

[0121] Table 1 Test data of Examples 1-3 and Comparative Examples 1-3

[0122]

[0123] It can be seen from the above detection data that as the addition ratio of terephthalic acid in the dibasic acid increases, the product effect is improved. However, as the content of terephthalic acid increases, the bulk density shows a downward trend because the excessive content of purified terephthalic acid leads to a decrease in the dissolved amount of carbon dioxide and poor foaming effect.

Claims

1. A method for preparing low shrinkage and high resilience supercritical polyurethane foam beads, characterized in that: The following steps are involved: (1) Add the dibasic acid, diol and catalyst into the reactor, start stirring, and carry out esterification reaction at 200-210°C for 2h-3h under nitrogen protection, then add refined terephthalic acid, and then carry out ester exchange reaction at 220-230°C and pressure of 0.09-0.1MPa to obtain polyester diol; In the step (1), the amount of purified terephthalic acid is 5-10% of the sum of the mass of the dibasic acid and the purified terephthalic acid, the amount of the dibasic acid is 90-95% of the sum of the mass of the dibasic acid and the purified terephthalic acid, the dibasic acid is a mixture of one or two of adipic acid or azelaic acid in any proportion, and the diol is a mixture of one or more of ethylene glycol, 1,4-butanediol, 1,2-propylene glycol, and 1,3-propylene glycol in any proportion; (2) The antioxidant, catalyst, light stabilizer and the polyester diol obtained in step (1) are mixed and heated to 130-150° C. and mixed thoroughly; the isocyanate is heated to 45-55° C.; the chain extender is heated to 45-55° C.; the heated raw materials are metered and injected into the extruder through a high-speed stirring head, the mixed material is reacted and plasticized in the screw, and granulated by an underwater cutting system to obtain a low shrinkage and high resilience supercritical polyurethane; (3) adding low shrinkage, high resilience supercritical polyurethane and water in a mass ratio of 1:2 into an autoclave, then introducing carbon dioxide fluid into the autoclave, raising the temperature to 110-130°C and the pressure to 6-9MPa, and after reaching the set temperature and set pressure, directly releasing the pressure to normal pressure or maintaining the set temperature and set pressure for a certain period of time and then releasing the pressure to normal pressure, and drying to obtain low shrinkage, high resilience supercritical polyurethane foam beads; The catalyst is one of an organic bismuth catalyst, an organic tin catalyst, and a titanate catalyst; The antioxidant is one or more of phenolic antioxidants, amine antioxidants and phosphite antioxidants.

2. The method for preparing low shrinkage and high resilience supercritical polyurethane foam beads according to claim 1, characterized in that: In the step (2), the mass percentage of each raw material is: Polyester diol 59%-70% Isocyanate 23%-30% Chain extender 6%-11% Antioxidant 0.1-0.3% Light stabilizer 0.1-0.8% Catalyst 0.008%-0.05%.

3. The method for preparing low shrinkage and high resilience supercritical polyurethane foam beads according to claim 1, characterized in that: The isocyanate is one of 4,4'-diphenylmethane diisocyanate and 1,6-hexamethylene diisocyanate.

4. The method for preparing low shrinkage and high resilience supercritical polyurethane foam beads according to claim 1, characterized in that: The chain extender is one or both of 1,2-propylene glycol and 1,4-butanediol.

5. The method for preparing low shrinkage and high resilience supercritical polyurethane foam beads according to claim 1, characterized in that: The phenolic antioxidant is one of 1010 and 1076; the amine antioxidant is 445; and the phosphite antioxidant is one of 168 and 626.

6. The method for preparing low shrinkage and high resilience supercritical polyurethane foam beads according to claim 1, characterized in that: The light stabilizer is one of 944, 622 and LS-144.

7. The method for preparing low shrinkage and high resilience supercritical polyurethane foam beads according to claim 1, characterized in that: The organic bismuth catalyst is catalyst DY-20; the organic tin catalyst is T-12.

8. A low shrinkage, high resilience supercritical polyurethane foam beads, characterized in that: The low shrinkage and high resilience supercritical polyurethane foam beads are prepared by the preparation method of any one of claims 1 to 7.

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