Preparation process of supercritical foaming material and supercritical foaming material

Abstract

The application relates to the technical field of foaming materials, and particularly provides a preparation process of supercritical foaming material and the supercritical foaming material. The preparation process of the supercritical foaming material comprises the following steps: uniformly mixing polyurethane raw material components and then pouring the polyurethane raw material components into a mold to obtain a preformed material; and performing supercritical foaming on the preformed material to obtain the supercritical foaming material. The pouring method is adopted, and the problem that the rebound elasticity of foaming TPU is not high enough and the density is not low enough due to excessive internal stress generated by the existing method of melting and injection molding of thermoplastic TPU elastomer particles is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of foaming materials, in particular to a preparation process of supercritical foaming material and supercritical foaming material. BACKGROUND

[0002] Supercritical foaming material has many special advantages. Taking supercritical foaming thermoplastic polyurethane elastomer (TPU) as an example, it has the characteristics of fine and numerous cells, high resilience, and low density, and has been widely used in shoe materials, thermal insulation materials, shock-absorbing materials, noise-reducing materials, etc. In particular, in the field of shoe materials, supercritical foaming TPU as the midsole of sports shoes has been widely used in various running shoes.

[0003] For supercritical foaming material, pursuing better resilience and lower density has always been a hot topic in the industry and a research hotspot. SUMMARY

[0004] The inventors have found through a large number of analysis and research that the resilience and density of supercritical foaming TPU are related to the internal stress of the TPU material. The lower the internal stress of the TPU material, the better the resilience and the lower the density of the foaming TPU after supercritical foaming. In the prior art, the thermoplastic polyurethane elastomer needs to be melted, extruded, and injection molded before supercritical foaming. The inventors have found that the TPU material obtained after injection molding has high internal stress, which leads to insufficient resilience and insufficient low density of the TPU material after supercritical foaming.

[0005] To solve the above technical problems, the present application provides a preparation process of supercritical foaming material and supercritical foaming material.

[0006] The present application adopts the following technical solutions:

[0007] A preparation process of supercritical foaming material, comprising:

[0008] mixing polyurethane raw material components uniformly and pouring into a mold to obtain a preformed material;

[0009] supercritically foaming the preformed material to obtain the supercritical foaming material;

[0010] The polyurethane raw material components are composed of a polyurethane prepolymer and a first chain extender;

[0011] Alternatively, the polyurethane raw material components are composed of a second polymer polyol, a second isocyanate monomer, and a second chain extender.

[0012] Preferably, the polyurethane prepolymer is obtained by reacting a first polymeric polyol with a first polyisocyanate monomer at a molar ratio of hydroxyl groups in the first polymeric polyol to isocyanate groups in the first polyisocyanate monomer of 0.5-0.95:1.

[0013] Preferably, the first polymeric polyol and the second polymeric polyol are each selected from one or more of a polyether polyol and a polyester polyol.

[0014] Preferably, the molar ratio of isocyanate groups in the polyurethane prepolymer to active hydrogens in the first chain extender is 0.95-1.08:1.

[0015] Preferably, the molar ratio of hydroxyl groups in the second polymeric polyol, isocyanate groups in the second isocyanate monomer, and active hydrogens in the second chain extender is 0.5-0.95:1:0.15-0.6.

[0016] More preferably, the ratio of the number of moles of hydroxyl groups in the second polymeric polyol and active hydrogens in the second chain extender to the number of moles of isocyanate groups in the second isocyanate monomer is 1:0.95-1.1.

[0017] Preferably, the first chain extender and the second chain extender each contain no less than 2 active hydrogens in their molecular structure.

[0018] Preferably, the pressure of the pouring is 0.1-0.03 MPa.

[0019] Preferably, the supercritical foaming is a supercritical foaming process using one of supercritical CO2, supercritical N2, supercritical ethanol, supercritical propane, and supercritical butane.

[0020] A supercritical foaming material prepared by the preparation process of the supercritical foaming material of any of the above embodiments.

[0021] In summary, the present application has the following beneficial effects:

[0022] 1. The present application uses a pouring process to mix the raw material components of the thermoplastic polyurethane elastomer uniformly and then pours them into a mold. The raw material components react in the mold to form the thermoplastic polyurethane elastomer and form the desired shape. Compared to the molding method of using thermoplastic polyurethane prepolymer particles and performing melting and injection, the present application has lower internal stress, which can improve the resilience of the supercritical foaming TPU and reduce the density of the supercritical foaming TPU.

[0023] 2. In the pouring process of the present application, there is no special requirement for the raw material components of the polyurethane. It can be a combination of pre-prepared prepolymer raw materials and chain extenders, or a combination of polymeric polyols, polyisocyanate monomers, and chain extenders.

[0024] 3、In the pouring process of the present application, normal pressure pouring process or negative pressure pouring process can be used. The pre-formed material obtained by using negative pressure pouring process is better, the internal defects are better, the pre-formed material is more uniform and consistent, and higher resilience and lower density can be obtained.

[0025] 4、The present application uses a pouring process, and the raw material utilization rate is higher, which can reach 99% or more. The raw material utilization rate of the existing molding method using thermoplastic polyurethane prepolymer particles and melting and injection is about 95%. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described in detail below.

[0027] Throughout this specification, unless otherwise specifically indicated, the terms used herein are understood to have the meanings commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which the present application belongs. If there is a contradiction, the present specification is preferred.

[0028] The present application proposes a preparation process of supercritical foaming material, comprising:

[0029] After the polyurethane raw material components are mixed uniformly, they are poured into a mold to obtain a pre-formed material;

[0030] The pre-formed material is subjected to supercritical foaming to obtain a supercritical foaming material;

[0031] In the present application, the polyurethane raw material composition is not particularly limited and can be selected as needed. Specifically, the polyurethane raw material components can be composed of polyurethane prepolymer and first chain extender;

[0032] Alternatively, the polyurethane raw material components can be composed of second polymeric polyol, second isocyanate monomer and second chain extender.

[0033] In one preferred embodiment of the present application, the polyurethane prepolymer can be obtained by reacting a first polymeric polyol with a first polyisocyanate monomer, and the molar ratio of hydroxyl groups in the first polymeric polyol to isocyanate groups in the first polyisocyanate monomer can be 0.5-0.95:1. For example, the molar ratio can be 0.5:1, 0.53:1, 0.55:1, 0.57:1, 0.6:1, 0.63:1, 0.65:1, 0.68:1, 0.7:1, 0.72:1, 0.75:1, 0.78:1, 0.8:1, 0.83:1, 0.85:1, 0.87:1, 0.9:1, 0.92:1, 0.95:1, etc. The insufficient molar amount of hydroxyl groups relative to the molar amount of isocyanate groups can allow a certain amount of isocyanate groups to be contained in the molecular structure of the polyurethane prepolymer, so as to react with the first chain extender and be cured into a desired shape in the mold. More preferably, the molar ratio of hydroxyl groups in the first polymeric polyol to isocyanate groups in the first polyisocyanate monomer can be 0.65-0.9:1.

[0034] In one preferred embodiment of the present application, the first polymeric polyol and the second polymeric polyol are each selected from one or more of polyether polyols and polyester polyols. Polyether polyols and polyester polyols are conventional raw materials for preparing polyurethanes. Specifically, the polyether polyol can be selected from homopolymers or copolymers of polyethylene glycol (PEG), polypropylene glycol (PPG), or polytetramethylene glycol (PTMG), and the copolymer can be a PEG-PPG copolymer, a PEG-PTMG copolymer, etc. The polyester polyol can be a polycarbonate polyol, a polycaprolactone polyol, a 1,6-hexanedioic acid-1,4-butanediol diol, etc.

[0035] In one preferred embodiment of the present application, the molar ratio of isocyanate groups in the polyurethane prepolymer to active hydrogen in the first chain extender is 0.95-1.08:1. In the present application, the active hydrogen refers to the hydrogen atoms on the groups in the chain extender that can adduct with isocyanate, such as 1 active hydrogen on a hydroxyl group, 2 active hydrogens on a primary amino group, 1 active hydrogen on a secondary amino group, etc. Controlling the molar ratio of isocyanate groups in the polyurethane prepolymer to active hydrogen in the first chain extender in the above range, the molecular weight of the preform material after the reaction is relatively high. More preferably, the molar ratio of isocyanate groups in the polyurethane prepolymer to active hydrogen in the first chain extender is 0.96-1.05:1. For example, the molar ratio can be 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, etc. Still more preferably, the molar ratio is 0.96-1.02:1.

[0036] In one preferred embodiment of the present application, the molar ratio of the hydroxyl groups in the second polymeric polyol, the isocyanate groups in the second isocyanate monomer, and the active hydrogen in the second chain extender is 0.5-0.95:1:0.15-0.6. More preferably, the molar ratio of the hydroxyl groups in the second polymeric polyol, the isocyanate groups in the second isocyanate monomer, and the active hydrogen in the second chain extender is 0.6-0.9:1:0.15-0.5. More preferably, the ratio of the moles of the hydroxyl groups in the second polymeric polyol and the moles of the active hydrogen in the second chain extender to the moles of the isocyanate groups in the second isocyanate monomer is 1:0.95-1.1. The moles of the hydroxyl groups in the second polymeric polyol is equal to the moles of the active hydrogen, therefore, the ratio of the moles of the active hydrogen in the second polymeric polyol and the moles of the active hydrogen in the second chain extender to the moles of the isocyanate groups in the second isocyanate monomer is 1:0.95-1.1. More preferably, the molar ratio is 1:0.95-1.05, for example, the molar ratio can be 1:0.95, 1:0.96, 1:0.97, 1:0.98, 1:0.99, 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05, etc.

[0037] In the present application, the first polyisocyanate monomer and the second polyisocyanate monomer are not particularly limited and can be selected from TDI, MDI, HDI, IPDI, HMDI, etc.

[0038] In one preferred embodiment of the present application, the first chain extender and the second chain extender each contain no less than 2 active hydrogens in their molecular structure. The chain extender containing no less than 2 active hydrogens can play a chain extending role. For example, the first chain extender and the second chain extender can each be independently selected from small molecule diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, etc., or small molecule diamines such as ethylenediamine, N,N’-dimethylethylenediamine, N,N’-dimethylpropanediamine, N-methylethylenediamine, etc.

[0039] In one preferred embodiment of the present application, the pouring pressure is 0.1-0.03 MPa. When the pouring pressure is 0.1 MPa, it is normal pressure pouring. When the pouring pressure is lower than 0.1 MPa, for example, 0.03-0.09 MPa, it is negative pressure pouring. Compared with normal pressure pouring, negative pressure pouring has a faster and more uniform pouring speed. More preferably, the pouring is negative pressure pouring and the pouring pressure is 0.03-0.08 MPa.

[0040] In one preferred embodiment of the present application, the supercritical foaming is supercritical foaming using a supercritical fluid. Specifically, the supercritical fluid can be selected from one of supercritical CO2, supercritical N2, supercritical ethanol, supercritical propane and supercritical butane. Specifically, the supercritical foaming process is not particularly limited, and specifically can be as follows: the preformed material is placed in a high-pressure reaction kettle and sealed, supercritical fluid is introduced and pressurized to a saturated state (pressure 8-30 MPa, temperature 40-65℃, pressure holding time 12-36h), and the supercritical fluid is rapidly released to obtain a swollen material; the swollen material is removed and placed in a constant temperature device to foam to obtain a foamed material, the foaming temperature is 80-120℃, and the foaming time is 0.1-5min. The foamed material can further be subjected to the following process steps: after the foamed material is dried, it is placed in a pressure holding container, CO2 and N2 mixed gas (volume ratio 1:9-9:1) is introduced, the pressure is increased to not more than 5MPa, pressure holding is performed for 20-36h, and the pressure is released.

[0041] The present application also provides a supercritical foamed material prepared by the preparation process of the supercritical foamed material according to any one of the above embodiments.

[0042] The supercritical foamed material of the present application can be applied to the technical fields of shock-absorbing materials, sound-absorbing materials, waterproof materials, etc., such as shoe materials, waterproof layers, etc.

[0043] The technical solutions of the present application will be described in detail below in combination with examples and comparative examples.

[0044] Example 1

[0045] Each raw material is subjected to pre-dewatering treatment.

[0046] PTMG-2000 (2000 represents the average molecular weight) and IPDI are added to a container in a molar ratio of hydroxyl groups to isocyanate groups of 0.7:1, heated to 80℃ and reacted for 1 hour, then PTMG and IPDI are added in an amount of 0.15% of dibutyltin dilaurate, and the reaction is continued for 2 hours to obtain a polyurethane prepolymer.

[0047] The above polyurethane prepolymer and 1,4-butanediol are mixed in a molar ratio of isocyanate to hydroxyl groups of 0.99:1, then poured into a mold under normal pressure, and reacted to obtain a preformed material.

[0048] The preformed material is placed in a high-pressure reactor, supercritical CO2 is introduced to a pressure of 22 MPa, the temperature is maintained at 55-58°C, and the pressure is maintained for 15 hours. The supercritical CO2 is rapidly released to obtain a swollen material. The swollen material is removed and placed in a constant temperature device to foam at 105°C for 1 minute to obtain a pre-foamed material. The pre-foamed material is dried and placed in a pressure maintaining container. A mixture of CO2 and N2 gas (volume ratio 1:1) is introduced, the pressure is increased to 2.2 MPa, and the pressure is maintained for 24 hours. The gas is removed to obtain a supercritical foamed material.

[0049] Example 2

[0050] In Example 1, the atmospheric pressure casting is replaced by negative pressure casting at 0.07 MPa, and the remaining steps remain unchanged.

[0051] Example 3

[0052] In Example 1, the atmospheric pressure casting is replaced by negative pressure casting at 0.035 MPa, and the remaining steps remain unchanged.

[0053] Example 4

[0054] In Example 2, the molar ratio of isocyanate in the polyurethane prepolymer and hydroxyl in 1,4-butanediol is adjusted to 0.98:1, and the remaining steps remain unchanged.

[0055] Example 5

[0056] Each raw material is pre-dehydrated.

[0057] Polycarbonate diol-2000, 1,4-butanediol and HMDI are mixed in a molar ratio of 0.78:0.23:1, and 0.12% of dibutyltin dilaurate based on the total weight of the reaction raw materials is added and mixed uniformly. The mixture is cast into a mold under negative pressure at 0.08 MPa, and the reaction is carried out to obtain a preformed material.

[0058] The preformed material is foamed according to the supercritical foaming method in Example 1 to obtain a supercritical foamed material.

[0059] Example 6

[0060] In Example 5, the molar ratio of polycarbonate diol-2000, 1,4-butanediol and HMDI is adjusted to 0.8:0.2:1, and the remaining steps remain unchanged.

[0061] Example 7

[0062] Polycarbonate diol-2000 and IPDI are added to a container in a molar ratio of hydroxyl and isocyanate groups of 0.8:1, and the temperature is raised to 80°C for 1 hour. Dibutyltin dilaurate is added in an amount of 0.15% based on the weight of polycarbonate diol-2000 and IPDI, and the reaction is continued for 2 hours to obtain a polyurethane prepolymer.

[0063] The polyurethane prepolymer and 1,6-hexanediol described above were mixed at an isocyanate and hydroxyl molar ratio of 0.98:1 and cast into a mold under a reduced pressure of 0.06 MPa, reacted, and a preform was obtained.

[0064] The preform was foamed according to the supercritical foaming method of Example 1, and a supercritical foamed material was obtained.

[0065] Comparative Example 1

[0066] The polyurethane prepolymer and 1,4-butanediol described above were added to a twin-screw extruder at an isocyanate and hydroxyl molar ratio of 0.99:1, extruded at 150-210°C, and injection molded into pellets. Temperature zone control: first zone temperature 150-160°C, second zone temperature 160-170°C, third zone temperature 180-190°C, fourth zone temperature 190-200°C, fifth zone temperature 200-210°C, sixth zone temperature 190-200°C, seventh zone temperature 180-190°C, eighth zone temperature 180-190°C, ninth zone temperature 180-190°C, and die temperature 175-180°C.

[0067] The pellets obtained above were dried to remove water, and injection molded. Cylinder temperature 180-230°C, injection pressure 52 MPa, holding pressure 27 MPa, injection speed 100%, injection time 36 s, screw rotation speed 32 r / min, and mold temperature 30°C. Temperature zone control: first zone temperature 180-190°C, second zone temperature 190-200°C, third zone temperature 200-210°C, fourth zone temperature 210-220°C, fifth zone temperature 220-230°C, sixth zone temperature 220-230°C, seventh zone temperature 200-210°C, eighth zone temperature 190-200°C, ninth zone temperature 190-200°C, and die temperature 185°C.

[0068] Comparative Example 2

[0069] In Comparative Example 1, the polyurethane prepolymer and 1,4-butanediol were added to a twin-screw extruder at an isocyanate and hydroxyl molar ratio of 0.99:1, directly injection molded into a mold, and molded. Cylinder temperature 180-230°C, injection pressure 52 MPa, holding pressure 27 MPa, injection speed 100%, injection time 36 s, and screw rotation speed 32 r / min. Temperature zone control: first zone temperature 150-160°C, second zone temperature 180-190°C, third zone temperature 200-210°C, fourth zone temperature 200-210°C, fifth zone temperature 220-230°C, sixth zone temperature 220-230°C, seventh zone temperature 200-210°C, eighth zone temperature 190-200°C, ninth zone temperature 190-200°C, and die temperature 185°C.

[0070] Comparative Example 3

[0071] Each raw material was pre-treated by dehydration. The molar ratio of polycarbonate diol-2000, 1,4-butanediol and HMDI was 0.78:0.23:1.

[0072] Polycarbonate diol-2000 and HMDI were added into a container, and the temperature was raised to 80℃ for 1 hour, then polycarbonate diol-2000 and HMDI were added again with 0.12% of dibutyltin dilaurate by weight, and the reaction was continued for 2 hours to obtain a polyurethane prepolymer.

[0073] The above polyurethane prepolymer and 1,4-butanediol were added into a twin-screw extruder, and granulation and molding were carried out according to the granulation and molding methods of Comparative Example 1 to obtain a supercritical foaming material.

[0074] Performance test

[0075] Ball rebound resilience: tested according to the method of GB / T6670-2008.

[0076] Density: tested by KW-300A microcomputer electronic densimeter.

[0077] The results are shown in Table 1 below.

[0078] Table 1

[0079] Ball rebound, % Density / g / cm 3 <!-- 5 -->]]> Example 1 72 0.153 Example 2 73 0.148 Example 3 73 0.146 Example 4 71 0.150 Comparative Example 1 69 0.163 Comparative Example 2 66 0.171 Example 5 69 0.187 Example 6 70 0.184 Example 7 68 0.190 Comparative Example 3 66 0.198

[0080] From the results of Table 1, it can be seen that the supercritical foaming material obtained by the supercritical foaming material preparation process of the present application has the characteristics of better resilience and lower density.

[0081] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the specification, and as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A process for preparing a supercritical foaming material, characterized in that: include: The polyurethane raw material components are mixed evenly and then poured into a mold to obtain a preformed material; The pouring pressure is 0.1-0.03MPa; performing supercritical foaming on the preformed material to obtain the supercritical foamed material; The polyurethane raw material components are composed of a polyurethane prepolymer and a first chain extender; the polyurethane prepolymer is obtained by reacting a first polymer polyol with a first polyisocyanate monomer at a molar ratio of hydroxyl groups in the first polymer polyol to isocyanate groups in the first polyisocyanate monomer of 0.5-0.95:1; the molar ratio of isocyanate groups in the polyurethane prepolymer to active hydrogen in the first chain extender is 0.95-1.08:1; Alternatively, the polyurethane raw material component consists of a second polymer polyol, a second isocyanate monomer and a second chain extender; the molar ratio of the hydroxyl group in the second polymer polyol, the isocyanate group in the second isocyanate monomer and the active hydrogen in the second chain extender is 0.5-0.95:1:0.15-0.

6.

2. The preparation process of the supercritical foaming material according to claim 1, wherein The first polymer polyol and the second polymer polyol are respectively selected from one or more of polyether polyols and polyester polyols.

3. The preparation process of the supercritical foaming material according to claim 2, wherein The ratio of the molar number of hydroxyl groups in the second polymer polyol and the active hydrogen in the second chain extender to the molar number of isocyanate groups in the second isocyanate monomer is 1:0.95-1.

1.

4. The preparation process of the supercritical foaming material according to claim 1, wherein The molecular structures of the first chain extender and the second chain extender respectively contain no less than 2 active hydrogen atoms.

5. The preparation process of the supercritical foaming material according to claim 1, wherein The supercritical foaming is a supercritical foaming process using one of supercritical CO2, supercritical N2, supercritical ethanol, supercritical propane and supercritical butane.

6. A supercritical foaming material, characterized in that: The supercritical foaming material is prepared by the preparation process of the supercritical foaming material according to any one of claims 1 to 5.