Thermoplastic polyurethane and process for its preparation

Abstract

The application discloses a preparation method of thermoplastic polyurethane, and the thermoplastic polyurethane is of a star multi-arm structure. The thermoplastic polyurethane with the structure has the characteristics of low processing temperature, fast product forming speed and good extrusion stability in the field of injection molding and extrusion products, can effectively make up for the shortcomings of the existing thermoplastic polyurethane, and can be widely used in the fields of shoe materials, clothing, medical products, industrial products, consumer electronics and the like.

Description

Technical Field

[0001] This invention relates to a novel thermoplastic polyurethane and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU) is a high-performance polymer synthetic material with excellent comprehensive properties. It has excellent mechanical properties such as high strength, high elasticity, high abrasion resistance and high flexibility, as well as resistance to oil, solvents and chemicals. It can be plasticized by heating and dissolved by solvents, and has a variety of processing methods. In addition, it is easy to transport, has low VOC emissions, and is environmentally friendly. It is widely used in clothing, footwear, heat sealing, printing, leather, handicrafts or electronic products and other fields.

[0003] Patent CN110527479B discloses a hyperbranched thermoplastic polyurethane adhesive and its application in fire hoses. This invention involves reacting PTMEG with MDI to obtain an NCO-terminated prepolymer 1. A portion of prepolymer 1 reacts with excess diisopropanolamine to obtain an OH-terminated prepolymer 2. Prepolymer 1 and prepolymer 2 react to obtain a prepolymer 3. Finally, excess diisopropanolamine is added to prepolymer 3 for end-capping, resulting in a hydroxyl-terminated thermoplastic polyurethane adhesive with a hyperbranched structure. The prepared adhesive exhibits good thermal stability and can effectively improve its bonding strength with the bonded materials. However, in the preparation of the hyperbranched TPU, the reaction controllability is poor, and cross-linking reactions easily occur, rendering the product unusable. Furthermore, a large amount of diisopropanolamine residue remains during the preparation process, severely affecting product performance.

[0004] Patent CN112480361A discloses a method for preparing a breathable thermoplastic polyurethane film. This invention uses citric acid, diol, and gallic acid to prepare a hyperbranched polyester polyol, which is then reacted with diisocyanate and a small-molecule chain extender to prepare a thermoplastic polyurethane elastomer. The film made from this elastomer exhibits good hydrophilicity, mechanical properties, and breathability, and has application value in medical supplies, clothing, home furnishings, and food packaging. The hyperbranched structure in this invention exists only in the polyester polyol, while the TPU molecular chain is linear.

[0005] Patent CN 112341803 B discloses a hyperbranched TPU hydrophilic film and its preparation method. This invention uses Eucommia ulmoides seed oil, formic acid, hydrogen peroxide, and hydroxyl compounds to prepare a hyperbranched bio-oil-based polyol, which is then reacted with diisocyanate and a small molecule chain extender to prepare TPU. The resulting TPU film exhibits excellent hydrophilic and breathable properties and utilizes biorenewable resources. However, the hyperbranched structure in this invention exists only in the bio-oil-based polyol; the TPU molecular chain remains linear.

[0006] Conventional TPU molecular chains are linear structures that can be repeatedly processed. However, there are no literature reports on how to prepare a TPU with good controllability, a star-shaped multi-arm structure, and reprocessability. Summary of the Invention

[0007] The purpose of this invention is to provide a novel thermoplastic polyurethane and its preparation method. A star-shaped multi-arm TPU is prepared by multi-step controllable reactions of monofunctional / bifunctional / multifunctional raw materials. Thermoplastic polyurethane with this structure exhibits advantages such as low processing temperature, fast molding speed, and good extrusion stability in injection molding and extrusion products, effectively overcoming the shortcomings of existing thermoplastic polyurethanes.

[0008] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0009] A novel thermoplastic polyurethane, the preparation method of which includes the following steps:

[0010] I. The reaction of diisocyanate and bifunctional macromolecular compound yields prepolymer A with diisocyanate-terminated ends;

[0011] II. Prepolymer A reacts with a monofunctional small molecule compound to obtain prepolymer B, which is capped with a single isocyanate group.

[0012] III. Prepolymer B is mixed and reacted with a multifunctional small molecule chain extender to obtain a novel thermoplastic polyurethane.

[0013] In this invention, the reactions of diisocyanate with bifunctional macromolecular compounds, prepolymer A with monofunctional small molecule compounds, and prepolymer B with polyfunctional small molecule chain extenders can all employ conventional methods in the art without particular limitations. For example, in some specific embodiments, the molar ratio of diisocyanate to bifunctional macromolecular compounds is approximately 2:1, the molar ratio of isocyanate groups to monofunctional small molecule compounds in prepolymer A is approximately 2:1, the molar ratio of isocyanate groups to active hydrogen in mono / bifunctional compounds in diisocyanate is approximately 4:3, and the molar ratio of isocyanate groups to active hydrogen in polyfunctional small molecule chain extenders in prepolymer B is approximately 1:1.

[0014] The diisocyanate described in this invention is at least one of aromatic diisocyanates and aliphatic diisocyanates, such as toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, terephthalic diisocyanate, naphthalene diisocyanate, 1,4-cyclohexane diisocyanate, phenylmethylene diisocyanate, cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, tetramethyl-methylene diisocyanate, norbornene diisocyanate, dimethylbiphenyl diisocyanate, methylcyclohexyl diisocyanate, dimethyl diphenylmethane diisocyanate, and lysine diisocyanate, preferably at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and terephthalic diisocyanate.

[0015] The number-average molecular weight of the bifunctional macromolecular compound of the present invention is preferably 800-6000 g / mol, more preferably 1000-4000 g / mol, and is selected from at least one of polyether polyols, aliphatic polyester polyols, and aromatic polyester polyols, for example, preferably one or more of polytetrahydrofuran diol, polybutylene adipate diol, polycarbonate diol, poly(1,6-hexanediol terephthalate) diol, and polypropylene oxide diol.

[0016] The molecular weight of the monofunctional small molecule compound described in this invention is preferably 32-170 g / mol, and it is at least one of a monofunctional alcohol and a monofunctional amine. The monofunctional alcohol includes: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 3-buten-1-ol, 3-butyn-1-ol, 2-methyl-3-buten-2-ol, 2-methyl-3-butyn-2-ol, propargyl alcohol, 2-methyl-2-propanol, and 1-tert-butoxy. -2-propanol, 1-pentanol, 2-pentanol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, phenol, 2-hydroxybiphenyl, 3-hydroxybiphenyl, 4-hydroxybiphenyl, 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine; monofunctional amines include: butylamine, tert-butylamine, pentanol, hexylamine, aniline, aziridine, pyrrolidine, piperidine, morpholine. Preferably, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, tert-butanol, 2-methyl-2-propanol, 1-tert-butoxy-2-propanol, 1-pentanol, 1-hexanol, 1-heptanol, 1-octanol, phenol, 2-hydroxypyridine, butylamine, tert-butylamine, pentanol, hexylamine;

[0017] The molecular weight of the multifunctional small molecule chain extender of the present invention is preferably 92-276 g / mol, and it is at least one of the polyols with at least three functionalities; such as at least one of trimethylolpropane, 2-hydroxymethylpropanediol, 2-hydroxyethylbutanediol, 3-hydroxyethylpentanediol, glycerol, pentaerythritol, 2-hydroxyethyl-4-hydroxypropyloctanediol, tetrahydroxyethylheptanediol, triethanolamine, and triisopropanolamine, preferably at least one of trimethylolpropane, 2-hydroxymethylpropanediol, glycerol, pentaerythritol, 2-hydroxyethyl-4-hydroxypropyloctanediol, tetrahydroxyethylheptanediol, and triethanolamine.

[0018] The novel thermoplastic polyurethane described in this invention has a star-shaped multi-arm structure and features low processing temperature, fast product molding speed, and good extrusion stability. It can be widely used in footwear, apparel, medical products, industrial products, consumer electronics, and other fields.

[0019] The technical solution provided by this invention has the following beneficial effects:

[0020] This invention prepares a star-shaped multi-arm TPU by using monofunctional / bifunctional / multifunctional raw materials through a multi-step controllable reaction. This multi-arm TPU has a high overall molecular weight, resulting in excellent mechanical properties, while the molecular weight of each individual arm is relatively low. The processing temperature is related to the molecular weight of each individual arm, thus the processing temperature of the multi-arm TPU is not high. The star-shaped multi-arm TPU exhibits stronger hard segment aggregation effect, and combined with its high molecular weight, it allows for faster molding speeds, effectively improving the processing efficiency of injection molded products. Furthermore, the multi-arm structure effectively stabilizes the viscosity of the TPU system in the molten state, which is beneficial to the extrusion processing stability of the products. In summary, the star-shaped multi-arm TPU effectively overcomes the shortcomings of existing thermoplastic polyurethanes and can be widely used in footwear, apparel, medical products, industrial products, consumer electronics, and other fields. Detailed Implementation

[0021] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the invention to the following embodiments. Various substitutions or modifications made based on ordinary technical knowledge and conventional methods in the art without departing from the above-described methodological spirit of the invention should be included within the scope of the invention.

[0022] Test method:

[0023] The test standard for tensile strength and elongation at break is ASTM D412.

[0024] Cooling time for injection molding of 2mm standard test piece: Under certain injection molding conditions, the cooling time required for the gate of the test piece to not undergo plastic deformation when injection molding a 2mm standard test piece (125mm*65mm*2mm). Other injection molding conditions such as injection temperature, injection pressure, holding time, mold temperature, etc. are kept the same in all examples and comparative examples, and the difference in cooling time is compared.

[0025] Extruded pipe diameter deviation: Under certain extrusion conditions, when extruding standard pipe (inner diameter 6mm, outer diameter 8mm), the average pipe diameter deviation displayed by the real-time diameter measuring instrument is compared. The extrusion conditions such as extrusion temperature and extrusion speed are kept the same in all embodiments and comparative examples, and the pipe diameter deviation is compared.

[0026] Example 1

[0027] A star-shaped multi-arm thermoplastic polyurethane, the raw materials for which are prepared include the following components:

[0028] (1) Diisocyanate: Diphenylmethane diisocyanate, 3.6 mol;

[0029] (2) Bifunctional macromolecular compound: polytetrahydrofuran diol, with a number average molecular weight of 2000 g / mol, 1.8 mol;

[0030] (3) Monofunctional small molecule compound: 1-octanol, 1.8 mol;

[0031] (4) Multifunctional small molecule chain extender: pentaerythritol, 0.45 mol.

[0032] The preparation method includes the following steps:

[0033] 1) At 100℃, a bifunctional macromolecular compound is added to the diisocyanate. After the reaction is complete, NCO-terminated prepolymer A is obtained.

[0034] 2) At the same temperature as in step 1), add a monofunctional small molecule compound to prepolymer A. After the reaction is complete, NCO-terminated prepolymer B is obtained.

[0035] 3) At 80°C, the multifunctional small molecule chain extender is thoroughly mixed with the prepolymer B in step 2) and reacted completely to obtain a star-shaped multi-arm thermoplastic polyurethane.

[0036] The properties of the prepared star-shaped multi-arm thermoplastic polyurethane are shown in Table 1.

[0037] Comparative Example 1

[0038] Raw materials for preparing linear thermoplastic polyurethane elastomers:

[0039] (1) Diisocyanate: Diphenylmethane diisocyanate, 3.6 mol;

[0040] (2) Other macromolecular diols: polytetrahydrofuran diol, with a number average molecular weight of 2000 g / mol, 1.8 mol;

[0041] (3) Small molecule chain extender: 1,4-butanediol, 1.8 mol.

[0042] The preparation method includes the following steps:

[0043] 1) Mix other macromolecular diols and small molecule chain extenders evenly to obtain a mixture;

[0044] 2) At 100°C, diisocyanate is added to the mixture in step 1), and the mixture is thoroughly mixed and reacted completely to obtain the thermoplastic polyurethane with the linear structure.

[0045] The properties of the prepared linear thermoplastic polyurethane elastomer are shown in Table 1.

[0046] Example 2

[0047] A star-shaped multi-arm thermoplastic polyurethane, the raw materials for which are prepared include the following components:

[0048] (1) Diisocyanate: Dicyclohexylmethane diisocyanate, 4.2 mol;

[0049] (2) Bifunctional macromolecular compound: polycarbonate diol, number average molecular weight of 1000 g / mol, 2.1 mol;

[0050] (3) Monofunctional small molecule compound: 2-methyl-2-propanol, 2.1 mol;

[0051] (4) Multifunctional small molecule chain extender: glycerol, 0.7 mol.

[0052] The preparation method includes the following steps:

[0053] 1) At 140℃, a bifunctional macromolecular compound was added to the diisocyanate. After the reaction was complete, NCO-terminated prepolymer A was obtained.

[0054] 2) At the same temperature as in step 1), add a monofunctional small molecule compound to prepolymer A. After the reaction is complete, NCO-terminated prepolymer B is obtained.

[0055] 3) At a temperature of 120°C, the multifunctional small molecule chain extender is thoroughly mixed with the prepolymer B in step 2) and reacted completely to obtain a star-shaped multi-arm thermoplastic polyurethane.

[0056] The properties of the prepared star-shaped multi-arm thermoplastic polyurethane are shown in Table 1.

[0057] Example 3

[0058] A star-shaped multi-arm thermoplastic polyurethane, the raw materials for which are prepared include the following components:

[0059] (1) Diisocyanate: diphenylmethane diisocyanate, 4.5 mol;

[0060] (2) Bifunctional macromolecular compound: polybutylene adipate diol, with a number average molecular weight of 800 g / mol and 2.25 mol;

[0061] (3) Monofunctional small molecule compound: 2-methyl-3-buten-2-ol, 2.25 mol;

[0062] (4) Multifunctional small molecule chain extender: Trimethylolpropane, 0.75 mol.

[0063] The preparation method includes the following steps:

[0064] 1) At 60°C, a bifunctional macromolecular compound is added to the diisocyanate. After the reaction is complete, NCO-terminated prepolymer A is obtained.

[0065] 2) At the same temperature as in step 1), add a monofunctional small molecule compound to prepolymer A. After the reaction is complete, NCO-terminated prepolymer B is obtained.

[0066] 3) At a temperature of 60°C, the multifunctional small molecule chain extender is thoroughly mixed with the prepolymer B in step 2) and reacted completely to obtain a star-shaped multi-arm thermoplastic polyurethane.

[0067] The properties of the prepared star-shaped multi-arm thermoplastic polyurethane are shown in Table 1.

[0068] Example 4

[0069] A star-shaped multi-arm thermoplastic polyurethane, the raw materials for which are prepared include the following components:

[0070] (1) Diisocyanate: Dicyclohexylmethane diisocyanate, 3.2 mol;

[0071] (2) Bifunctional macromolecular compound: polyoxypropylene glycol, number average molecular weight is 6000 g / mol, 1.6 mol;

[0072] (3) Monofunctional small molecule compound: 1-tert-butoxy-2-propanol, 1.6 mol;

[0073] (4) Multifunctional small molecule chain extender: glycerol, 0.533 mol.

[0074] The preparation method includes the following steps:

[0075] 1) At 80°C, a bifunctional macromolecular compound is added to the diisocyanate. After the reaction is complete, NCO-terminated prepolymer A is obtained.

[0076] 2) At the same temperature as in step 1), add a monofunctional small molecule compound to prepolymer A. After the reaction is complete, NCO-terminated prepolymer B is obtained.

[0077] 3) At a temperature of 90°C, the multifunctional small molecule chain extender is thoroughly mixed with the prepolymer B in step 2) and reacted completely to obtain a star-shaped multi-arm thermoplastic polyurethane.

[0078] The properties of the prepared star-shaped multi-arm thermoplastic polyurethane are shown in Table 1.

[0079] Example 5

[0080] A star-shaped multi-arm thermoplastic polyurethane, the raw materials for which are prepared include the following components:

[0081] (1) Diisocyanate: Hexamethylene diisocyanate, 5.1 mol;

[0082] (2) Bifunctional macromolecular compound: Poly(1,6-hexanediol terephthalate) diol, with a number average molecular weight of 4000 g / mol and 2.55 mol;

[0083] (3) Monofunctional small molecule compound: 2-hydroxypyridine, 2.55 mol;

[0084] (4) Multifunctional small molecule chain extender: triisopropanolamine, 0.85 mol.

[0085] The preparation method includes the following steps:

[0086] 1) At 90°C, a bifunctional macromolecular compound is added to the diisocyanate. After the reaction is complete, NCO-terminated prepolymer A is obtained.

[0087] 2) At the same temperature as in step 1), add a monofunctional small molecule compound to prepolymer A. After the reaction is complete, NCO-terminated prepolymer B is obtained.

[0088] 3) At 100°C, the multifunctional small molecule chain extender is thoroughly mixed with the prepolymer B in step 2) and reacted completely to obtain a star-shaped multi-arm thermoplastic polyurethane.

[0089] The properties of the prepared star-shaped multi-arm thermoplastic polyurethane are shown in Table 1.

[0090] Table 1 Properties of thermoplastic polyurethane

[0091]

[0092]

Claims

1. A method for preparing thermoplastic polyurethane, comprising the following steps: I. The reaction of diisocyanate and bifunctional macromolecular compound yields prepolymer A with double-terminated isocyanate groups; II. Prepolymer A reacts with a monofunctional small molecule compound to obtain prepolymer B, which is capped with a single isocyanate group. III. Prepolymer B reacts with a multifunctional small molecule chain extender to obtain thermoplastic polyurethane.

2. The preparation method according to claim 1, wherein, The diisocyanate is at least one of aromatic diisocyanate and aliphatic diisocyanate.

3. The preparation method according to claim 2, wherein, The diisocyanate is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, terephthalic diisocyanate, naphthalene diisocyanate, 1,4-cyclohexane diisocyanate, phenylenediamine diisocyanate, cyclohexane diisocyanate, trimethyl-1,6-hexamethylene diisocyanate, tetramethyl-m-phenylenediamine diisocyanate, norbornene diisocyanate, dimethylbiphenyl diisocyanate, methylcyclohexyl diisocyanate, dimethyldiphenylmethane diisocyanate, and lysine diisocyanate.

4. The preparation method according to claim 1, wherein, The number-average molecular weight of the bifunctional macromolecular compound is 800–6000 g / mol.

5. The preparation method according to claim 1, wherein, The number-average molecular weight of the bifunctional macromolecular compound is 1000–4000 g / mol.

6. The preparation method according to any one of claims 1-5, wherein, The bifunctional macromolecular compound is selected from at least one of polyether polyols, aliphatic polyester polyols, and aromatic polyester polyols.

7. The preparation method according to claim 6, wherein, The bifunctional macromolecular compound is selected from one or more of polytetrahydrofuran diol, polybutylene adipate diol, polycarbonate diol, poly(1,6-hexanediol terephthalate) diol, and polypropylene oxide diol.

8. The preparation method according to claim 1, wherein, The molecular weight of the monofunctional small molecule compound is 32–170 g / mol.

9. The preparation method according to claim 1 or 8, wherein, The monofunctional small molecule compound is at least one of monofunctional alcohols and monofunctional amines, wherein the monofunctional alcohols include: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 3-buten-1-ol, 3-butyn-1-ol, 2-methyl-3-buten-2-ol, 2-methyl-3-butyn-2-ol, propargyl alcohol, 2-methyl-2-propanol, 1-tert-butoxy-2-propanol, 1-pentanol, 2-pentanol. The alcohol, 3-pentanol, 1-hexanol, 2-hexanol, 3-hexanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-octanol, 2-octanol, 3-octanol, 4-octanol, phenol, 2-hydroxybiphenyl, 3-hydroxybiphenyl, 4-hydroxybiphenyl, 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, and monofunctional amines include at least one of butylamine, tert-butylamine, pentylamine, hexylamine, aniline, aziridine, pyrrolidine, piperidine, and morpholine.

10. The preparation method according to claim 1, wherein, The molecular weight of the multifunctional small molecule chain extender is 92–276 g / mol.

11. The preparation method according to claim 1 or 10, wherein, The multifunctional small molecule chain extender is at least one of a polyol with at least three functionalities.

12. The preparation method according to claim 11, wherein, The multifunctional small molecule chain extender is selected from at least one of trimethylolpropane, 2-hydroxymethylpropanediol, 2-hydroxyethylbutanediol, 3-hydroxyethylpentanediol, glycerol, pentaerythritol, 2-hydroxyethyl-4-hydroxypropyloctanediol, tetrahydroxyethylheptanediol, triethanolamine, and triisopropanolamine.

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