A chain extender and its preparation method and cast polyurethane

Abstract

The present invention provides a chain extender and a preparation method thereof and a cast polyurethane, comprising the following steps: adding caprolactone and vacuum dehydrating to obtain dehydrated caprolactone, then transferring to a dropping kettle and keeping it warm at 40°C for standby use, stirring a monoprimary amine ammonia compound in a reactor and heating it to 70°C, then dropping dehydrated caprolactone, keeping the material in the reactor warm at 75°C for 120 minutes after the dropping is completed, and discharging the material to obtain a chain extender. The cast polyurethane product of the present invention has a uniform structure, a long operation time, strong tensile strength, high elongation at break, low compression permanent deformation, etc., giving the cast elastomer excellent comprehensive performance. It is easier to realize the process of large-scale polyurethane products and manufacture large-scale cast polyurethane products.

Description

Technical Field

[0001] The invention belongs to the field of chemistry, and in particular relates to a chain extender and a preparation method thereof and a cast polyurethane. Technical Background

[0002] Cast polyurethane elastomer (CPU) is a product produced by pouring a liquid reaction mixture into a mold. As a major branch of polyurethane, its soft and hard two-phase structure gives it good mechanical, physical and chemical properties. CPU is mainly composed of three parts: polyol, isocyanate and chain extender crosslinker. In addition, certain functional additives are also added.

[0003] Existing chain extenders and crosslinkers are mainly divided into two types: amines and alcohols. Diamine chain extenders are mainly used in the production of TDI series elastomer products, and can be divided into aromatic diamines and aliphatic diamines. The diamines used in CPU products are mainly aromatic diamines, because aliphatic diamines are more active and react quickly with isocyanates, resulting in rapid gelation, which is not suitable for casting into large devices. The activity of alcohol chain extenders is much lower than that of ammonia, and they are mainly used in MDI with higher activity. However, when making large CPU products, the reaction speed during the casting process cannot be too fast, otherwise the product will show a fault, resulting in uneven overall force on the product and greatly reducing the service life; the reaction speed in the later stage cannot be too slow, otherwise the product will age after ripening on the outside, and the product will not be fully ripened in the middle, resulting in a decrease in mechanical properties. In the case of unmodified polyols and isocyanates available on the market, the use of suitable chain extenders to cast large polyurethane products has great practical application significance. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to prepare a casting material with a gel time greater than 25 minutes so that it can cast a large polyurethane elastomer of more than 400KG and ensure that the internal components of the product are uniform and the mechanical properties of the product are excellent.

[0005] The present invention solves the technical problem by adopting the following technical solutions:

[0006] A method for preparing a chain extender comprises the following steps:

[0007] Caprolactone is added and vacuum dehydrated to obtain dehydrated caprolactone, which is then transferred to a dropping kettle and kept warm at 40°C for standby use. Aniline is stirred and heated to 70°C in the reactor, and then dehydrated caprolactone is added dropwise. After the addition is completed, the material in the reactor is kept warm at 75°C for 120 minutes, and the chain extender is obtained by discharging the material.

[0008] In a further improvement, the mass ratio of caprolactone to aniline is 228-456:93.

[0009] As a further improvement, the time for adding the dehydrated caprolactone dropwise is 130 minutes.

[0010] A chain extender prepared by the above-mentioned chain extender preparation method.

[0011] A cast polyurethane, comprising a polyurethane prepolymer and a chain extender; the mass ratio of the polyurethane prepolymer to the chain extender is 10-20:4.97-10.45; the chain extender is as described in claim 1.

[0012] As a further improvement, the preparation method of the polyurethane prepolymer is as follows:

[0013] Put polycaprolactone polyol into the reaction kettle and heat it to 120°C, vacuum dehydrate for 2h, cool it to 55°C, add diphenylmethane diisocyanate, heat it to 70°C and react for 2h, detect NCO%, and when the content reaches 5.8≤NC0%≤8, the polyurethane prepolymer is obtained.

[0014] As a further improvement, the mass ratio of the polycaprolactone polyol to diphenylmethane diisocyanate is 400:147.82-190.63.

[0015] Further improvement, the production method of the cast polyurethane is as follows:

[0016] Heat the mold sprayed with the release agent to 110°C and keep it warm for later use; add the polyurethane prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80°C, start stirring at the same time, vacuum degassing for 2h, break the vacuum with nitrogen, open the dry air valve for later use; add the chain extender to the chain extender storage tank of the casting machine and keep it warm at 70°C, start stirring at the same time, vacuum degassing for 2h, break the vacuum with nitrogen, open the dry air valve for later use; adjust the polyurethane prepolymer discharge speed to 10-20kg / min, the chain extender discharge speed to 4.97-10.45kg / min, and the casting speed to 20.45-27kg / min; open the mixing pouring head, pour the polyurethane prepolymer and the chain extender into the mold, fill the mold with materials, keep the reaction at 110°C for 90min, and then demould; after demoulding, transfer the product to an 80°C oven for aging for 10 hours, and then cool it at room temperature to obtain a cast polyurethane.

[0017] Compared with the prior art, the present invention has the following main advantages:

[0018] 1. Large-scale cast polyurethane products have uniform structure, long operation time, strong tensile strength, high elongation at break, low compression permanent deformation, etc., which give the cast elastomer excellent comprehensive performance. It is easier to realize the process of large-scale polyurethane products and make large-scale cast polyurethane products.

[0019] 2. The chain extender structure contains a secondary amino group and a hydroxyl group, has mild reactivity, can be used as a chain extender for polyurethane products, and has the characteristics of compatibility between hardness and toughness. DETAILED DESCRIPTION

[0020] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the present technical field.

[0021] Unless otherwise specified, all reagents and materials used in the present invention are commercially available.

[0022] Polycaprolactone polyol: PCL 2202C from Juren New Materials Co., Ltd.

[0023] Methylene diphenyl diisocyanate: Wanhua Chemical Group Co., Ltd. MDI

[0024] 3,3'-Dichloro-4,4'-diaminodiphenylmethane: Suzhou Xiangyuan Special Fine Chemical Co., Ltd. MOCA

[0025] Example 1

[0026] A method for preparing a chain extender, the method being as follows:

[0027] In the dehydration kettle, 228 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 174.5 mgKOH / g, and the hydroxyl value was 174.6 mgKOH / g, and the chain extender P1 was obtained.

[0028] A method for preparing a polyurethane prepolymer, the method being as follows:

[0029] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 5.8≤NC0%≤6, polyurethane prepolymer K1 was obtained.

[0030] A method for preparing cast polyurethane, the method being as follows:

[0031] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 300kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 20kg / min, the chain extender discharge speed to 4.97kg / min, and the pouring speed to 24.97kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 22min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 90A and the weight is 549kg. The cast polyurethane product F1 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0032] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0033] Example 2

[0034] A method for preparing a chain extender, the method being as follows:

[0035] In the dehydration kettle, 456 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 102.1 mgKOH / g, and the hydroxyl value was 102.2 mgKOH / g, and the chain extender P2 was obtained.

[0036] A method for preparing a polyurethane prepolymer, the method being as follows:

[0037] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 5.8≤NC0%≤6, polyurethane prepolymer K2 was obtained.

[0038] A method for preparing cast polyurethane, the method being as follows:

[0039] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 500kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 15kg / min, the chain extender discharge speed to 9.83kg / min, and the pouring speed to 24.83kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 22min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 87A and the weight is 546kg. The cast polyurethane product F2 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0040] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0041] Example 3

[0042] A method for preparing a chain extender, the method being as follows:

[0043] In the dehydration kettle, 456 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 102.1 mgKOH / g, and the hydroxyl value was 102.2 mgKOH / g, and the chain extender P3 was obtained.

[0044] A method for preparing a polyurethane prepolymer, the method being as follows:

[0045] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 190.63 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 7.8≤NC0%≤8, polyurethane prepolymer K3 was obtained.

[0046] A method for preparing cast polyurethane, the method being as follows:

[0047] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 500kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 10kg / min, the chain extender discharge speed to 10.45kg / min, and the pouring speed to 20.45kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 21min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 88A and the weight is 552kg. The cast polyurethane product F3 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0048] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0049] Example 4

[0050] A method for preparing a chain extender, the method being as follows:

[0051] In the dehydration kettle, 228 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 174.5 mgKOH / g, and the hydroxyl value was 174.6 mgKOH / g, and the chain extender P4 was obtained.

[0052] A method for preparing a polyurethane prepolymer, the method being as follows:

[0053] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 190.63 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 7.8≤NC0%≤8, polyurethane prepolymer K4 was obtained.

[0054] A method for preparing cast polyurethane, the method being as follows:

[0055] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 300kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 500kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 15kg / min, the chain extender discharge speed to 9.17kg / min, and the pouring speed to 24.17kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 23min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 91A and the weight is 555kg. The cast polyurethane product F4 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0056] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0057] Comparative Example 1

[0058] A method for preparing a chain extender, the method being as follows:

[0059] In the dehydration kettle, 228 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 186 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 270.9 mgKOH / g, and the hydroxyl value was 271 mgKOH / g, and the chain extender P5 was obtained.

[0060] A method for preparing a polyurethane prepolymer, the method being as follows:

[0061] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 190.63 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 7.8≤NC0%≤8, polyurethane prepolymer K5 was obtained.

[0062] A method for preparing cast polyurethane, the method being as follows:

[0063] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 400kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 18kg / min, the chain extender discharge speed to 7.09kg / min, and the pouring speed to 25.09kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 22min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 95A and the weight is 551kg. The cast polyurethane product F5 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0064] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0065] Comparative Example 2

[0066] A method for preparing a chain extender, the method being as follows:

[0067] In the dehydration kettle, 114 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 270.8 mgKOH / g, and the hydroxyl value was 271 mgKOH / g, and the chain extender P6 was obtained.

[0068] A method for preparing a polyurethane prepolymer, the method being as follows:

[0069] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 5.8≤NC0%≤6, polyurethane prepolymer K6 was obtained.

[0070] A method for preparing cast polyurethane, the method being as follows:

[0071] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 200kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 20kg / min, the chain extender discharge speed to 5.91kg / min, and the pouring speed to 25.91kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 21min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 93A and the weight is 544kg. The cast polyurethane product F6 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0072] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0073] Comparative Example 3

[0074] A method for preparing a chain extender, the method being as follows:

[0075] In the dehydration kettle, 570 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 84.6 mgKOH / g, and the hydroxyl value was 84.7 mgKOH / g, and the chain extender P7 was obtained.

[0076] A method for preparing a polyurethane prepolymer, the method being as follows:

[0077] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, the temperature was raised to 70°C and reacted for 2 hours, and the NCO% was detected. When the content reached 5.8≤NC0%≤6, the polyurethane prepolymer K7 was obtained.

[0078] A method for preparing cast polyurethane, the method being as follows:

[0079] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 500kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 10kg / min, the chain extender discharge speed to 9.47kg / min, and the pouring speed to 19.47kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 28min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 84A and the weight is 545kg. The cast polyurethane product F7 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0080] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0081] Comparative Example 4

[0082] A method for preparing a chain extender, the method being as follows:

[0083] In the dehydration kettle, 570 kg of caprolactone was heated to 50 ° C and vacuum-dehydrated for 120 minutes, then transferred to the dropping kettle and kept at 40 ° C for standby use. In the reactor, 93 kg of aniline was stirred and heated to 70 ° C. After the temperature of the reactor stabilized, caprolactone was added dropwise, and the dropping speed was controlled to be 130 minutes. The materials in the reactor were kept at 75 ° C for 120 minutes and discharged. The amine value was tested to be 84.6 mgKOH / g, and the hydroxyl value was 84.7 mgKOH / g, and the chain extender P8 was obtained.

[0084] A method for preparing a polyurethane prepolymer, the method being as follows:

[0085] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 5.8≤NC0%≤6, polyurethane prepolymer K8 was obtained.

[0086] A method for preparing cast polyurethane, the method being as follows:

[0087] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 500kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 11kg / min, the chain extender discharge speed to 13.89kg / min, and the pouring speed to 24.89kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 22min. Demould after 90min of reaction. After demoulding, transfer the product to an 80℃ oven for aging for 10 hours and then cool it at room temperature. There is no defect on the surface. The room temperature hardness is 83A and the weight is 547kg. The cast polyurethane product F8 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0088] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0089] Comparative Example 5

[0090] 1.4 butanediol was used as the chain extender P9.

[0091] A method for preparing a polyurethane prepolymer, the method being as follows:

[0092] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 5.8≤NC0%≤6, polyurethane prepolymer K9 was obtained.

[0093] A method for preparing cast polyurethane, the method being as follows:

[0094] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 500kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 100kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 70℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 24kg / min, the chain extender discharge speed to 3.08kg / min, and the pouring speed to 27.08kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 20min. Demolding after 90min of reaction. Due to the slow reaction, the product is difficult to demould and the surface of the product has defects. Transfer to 80℃ oven for aging for 10 hours and then cool at room temperature. The room temperature hardness is 95A and the weight is 541kg. The cast polyurethane product F9 is obtained. The product is cut into Type 1 specimens according to the national standard GB / T 528.

[0095] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0096] Comparative Example 6

[0097] MOCA was used as the chain extender P10.

[0098] A method for preparing a polyurethane prepolymer, the method being as follows:

[0099] 400 kg of polycaprolactone polyol 2202C was put into the reactor and heated to 120°C, vacuum dehydrated for 2 hours, cooled to 55°C, 147.82 kg of diphenylmethane diisocyanate was added, heated to 70°C and reacted for 2 hours, and NCO% was detected. When the content reached 5.8≤NC0%≤6, polyurethane prepolymer K10 was obtained.

[0100] A method for preparing cast polyurethane, the method being as follows:

[0101] Heat the mold sprayed with release agent to 110℃ and keep it warm for later use. Add 550kg prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80℃. Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Add 100kg chain extender to the chain extender storage tank of the casting machine and keep it warm at 110℃ (the melting point of MOCA is 102-108℃). Start stirring at the same time. Vacuum degassing for 2h. Break the vacuum with nitrogen. Open the dry air valve for later use. Adjust the prepolymer discharge speed to 24kg / min, the chain extender discharge speed to 4.42kg / min, and the casting speed to 28.42kg / min. Open the mixing pouring head, pour the prepolymer and chain extender into the mold, and fill the mold with materials after pouring for 20min. After 90 minutes of reaction, the mold was removed. Due to the too fast reaction, the bottom layer of the product solidified too quickly, the surface had defects and obvious stratification. It was transferred to an 80°C oven for aging for 10 hours and then cooled at room temperature. The room temperature hardness was 95A and the weight was 541 kg. The cast polyurethane product F10 was obtained. The product was cut into Type 1 specimens according to the national standard GB / T 528.

[0102] The tensile strength, elongation at break and permanent deformation at break of the test piece are tested according to Type 1 test piece of GB / T 528;

[0103] The test method for the performance of cast polyurethane elastomer test pieces is as follows:

[0104] The tensile strength and elongation at break of the test piece are tested according to GB / T 528, and the compression set is tested according to Type 1 specimen of GB / T 7759-1996, and the test condition is 70℃ / 22h; the hardness of the test piece is tested according to GB / T 531.1;

[0105] Table 1 Performance of cast elastomer test pieces prepared in Examples and Comparative Examples

[0106]

[0107] As can be seen from the above table, Examples 1-4 have strong tensile strength, high elongation at break and low compression set, and the cast polyurethane has balanced mechanical properties. However, Comparative Examples 1-2 have low elongation at break due to less grafted caprolactone, large compression set, and poor elastomeric properties. Comparative Examples 3-4 have more grafted caprolactone, and the hardness decreases, which greatly affects the tensile strength of the product, and has a greater impact on the elongation at break and compression set. Comparative Example 5 has a too slow reaction speed, which affects demoulding, and defects are generated on the surface of the product itself. Although the cut strips are free of defects, the mechanical properties are extremely poor, which may be related to incomplete aging. Comparative Example 6 has a too fast reaction speed, and the cut sample strips have obvious stratification, resulting in uneven cast polyurethane, and extremely poor tensile strength and elongation at break.

[0108] Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and describes these embodiments in detail in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A cast polyurethane, characterized in that: The cast polyurethane comprises a polyurethane prepolymer and a chain extender; the mass ratio of the polyurethane prepolymer to the chain extender is 10-20:4.97-10.45; the preparation method of the chain extender is as follows: Caprolactone is added and vacuum dehydrated to obtain dehydrated caprolactone, which is then transferred to a dropping kettle and kept at 40°C for standby use. Aniline is stirred and heated to 70°C in the reactor, and then dehydrated caprolactone is added dropwise. After the addition is completed, the material in the reactor is kept at 75°C for 120 minutes, and the chain extender is obtained by discharging the material; the mass ratio of caprolactone to aniline is 228-456:93; the time for dropping dehydrated caprolactone is 130 minutes; the preparation method of the polyurethane prepolymer is as follows: Put polycaprolactone polyol into the reaction kettle and heat it to 120°C, vacuum dehydrate for 2h, cool it to 55°C, add diphenylmethane diisocyanate, heat it to 70°C and react for 2h, detect NCO%, and when the content reaches 5.8≤NC0%≤8, the polyurethane prepolymer is obtained; the mass ratio of the polycaprolactone polyol to diphenylmethane diisocyanate is 400:147.82-190.63; the production method of the cast polyurethane is as follows: Heat the mold sprayed with the release agent to 110°C and keep it warm for later use; add the polyurethane prepolymer to the prepolymer storage tank of the casting machine and keep it warm at 80°C, start stirring at the same time, vacuum degassing for 2h, break the vacuum with nitrogen, open the dry air valve for later use; add the chain extender to the chain extender storage tank of the casting machine and keep it warm at 70°C, start stirring at the same time, vacuum degassing for 2h, break the vacuum with nitrogen, open the dry air valve for later use; adjust the polyurethane prepolymer discharge speed to 10-20kg / min, the chain extender discharge speed to 4.97-10.45kg / min, and the casting speed to 20.45-27kg / min; open the mixing pouring head, pour the polyurethane prepolymer and the chain extender into the mold, fill the mold with materials, keep the reaction at 110°C for 90min, and then demould; after demoulding, transfer the product to an 80°C oven for aging for 10 hours, and then cool it at room temperature to obtain a cast polyurethane.

Images