Crosslinked polyurethane material plasticizing transformation method, prepared regenerated polyurethane material and application

Abstract

The invention discloses a cross-linked polyurethane material plasticizing transformation method, a prepared regenerated polyurethane material and application, and belongs to the technical field of high polymer materials. The cross-linked polyurethane material plasticizing transformation method provided by the invention comprises the following steps: by taking a boric acid compound, a hydroxyl compound and a cross-linked polyurethane material as raw materials, carrying out in-situ reaction on the boric acid compound and the hydroxyl compound to generate a boron-oxygen polymer, and then carrying out heat exchange reaction on the cross-linked polyurethane material and the boron-oxygen polymer to obtain the cross-linked polyurethane material. The regenerated polyurethane material is prepared. Based on the reaction principle of dynamic exchange between a borate bond and a carbamate bond, a borate cross-linked polymer is mixed into cross-linked polyurethane, a boron-oxygen covalent bond is implanted into a molecular chain segment of polyurethane through an exchange reaction, and an original irreversible cross-linked polyurethane network is converted into a reversible cross-linked polymer network, so that the reversible cross-linked polymer network is formed; therefore, repeated processing can be carried out, and plasticity is shown.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and more particularly to a method for plasticizing and transforming a cross-linked polyurethane material, and the prepared recycled polyurethane material and its application. Background Art

[0002] Polyurethane (PU) is a polymer material produced through the polymerization reaction of polyols and isocyanates. Polyurethane is primarily used as a foam material. Depending on the raw material types and dosages used, soft, semi-rigid, and rigid polyurethane foams can be produced with varying densities and properties, each with its own distinct characteristics. Polyurethane is a block copolymer composed of soft and hard segments. The soft segments are composed of oligomeric polyols (typically polyethers or polyether diols), while the hard segments are composed of polyisocyanates or other small molecule chain extenders.

[0003] Due to its unique structure, polyurethane possesses excellent physical and chemical properties, including high mechanical strength, low thermal conductivity, good dimensional stability, and superior chemical resistance. It has been widely used in a variety of industries, including construction, automobiles, and furniture, and occupies an important position. However, the widespread use of polyurethane has also brought about environmental problems such as waste disposal and resource recycling. Traditional cross-linked polyurethane materials, such as rigid polyurethane foam, are typical thermosetting polymers. Once their cross-linked structure is formed, it is difficult to reprocess or recycle due to the high degree of cross-linking of the molecular network. As a result, a large amount of polyurethane materials are landfilled or incinerated, resulting in resource waste and environmental pollution.

[0004] Since the molecular structure of materials such as polyurethane rigid foam is a cross-linked network configuration composed of irreversible covalent bonds, the thermal motion of molecular chain segments is restricted by the cross-linking points, making them insoluble in organic solvents and unable to melt when heated, making them difficult to reuse through repeated thermal processing. Summary of the Invention

[0005] In response to the above problems, the present invention proposes a method for plasticizing and transforming a cross-linked polyurethane material, as well as a prepared recycled polyurethane material and its application. The present invention is based on the reaction principle of dynamic exchange between borate bonds and carbamate bonds. A borate cross-linked polymer is mixed into the cross-linked polyurethane, and boron-oxygen covalent bonds are implanted into the molecular chain segments of the polyurethane through an exchange reaction, thereby transforming the originally irreversibly cross-linked polyurethane network into a reversibly cross-linked polymer network, which can be repeatedly processed and exhibits plasticity.

[0006] A first object of the present invention is to provide a method for plasticizing a cross-linked polyurethane material, comprising the following steps: Boric acid compounds, hydroxyl compounds and cross-linked polyurethane materials are used as raw materials. The boric acid compounds and hydroxyl compounds react in situ to generate boron oxide polymers. Then, the cross-linked polyurethane materials and the boron oxide polymers undergo heat exchange reaction to prepare recycled polyurethane materials.

[0007] The present invention, based on an exchange reaction between carbamate and borate, inserts dynamic boron-oxygen bonds into polyurethane molecular segments. This allows the polyurethane molecular segments to undergo structural reorganization through the dynamic exchange reaction of the boron-oxygen bonds. The dynamic polymer additive enables plasticization of cross-linked polyurethane materials, such as rigid polyurethane foam, overcoming the scientific difficulty of reprocessing conventional cross-linked polymers and enabling secondary processing and reuse of the cross-linked polyurethane materials. The method of the present invention can be used to recycle and reuse cross-linked polyurethane materials, such as waste rigid polyurethane foam, contributing to the sustainable development of polyurethane materials.

[0008] In a preferred embodiment of the present invention, the mass ratio of the cross-linked polyurethane material to the boron oxide polymer is 1:0.05-50.

[0009] In a preferred embodiment of the present invention, the reaction temperature of the heat exchange reaction is 160° C. to 220° C., the reaction time is 0.5 h to 2 h, and the pressure is 0.1 MPa to 10 MPa.

[0010] In a preferred embodiment of the present invention, the molar ratio of the boron hydroxyl group in the boric acid compound to the alkylhydroxyl group in the hydroxyl compound is 1:1-1.2.

[0011] In a preferred embodiment of the present invention, the in-situ reaction temperature is 40° C. to 160° C., and the reaction time is 0.5 h to 6 h.

[0012] In a preferred embodiment of the present invention, the boronic acid compound is one or more of boric acid, alkylboronic acid and arylboronic acid.

[0013] In a preferred embodiment of the present invention, the hydroxy compound is a monohydroxy compound, a polyol compound, a polyester polyol or a polyether polyol.

[0014] The second object of the present invention is to provide a recycled polyurethane material prepared by the above method.

[0015] The third object of the present invention is to provide applications of the above-mentioned recycled polyurethane material in automobile manufacturing, textiles, electronic appliances, and adhesives.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The dynamic cross-linked polyurethane recovery method provided by the present invention has the advantages of easy operation, readily available and inexpensive raw materials, and flexible and diverse formulations and products. Compared to traditional polyurethane recovery methods such as alcoholysis, it offers significant advantages. Dynamic bond implantation technology directly converts non-moldable polyurethane materials into reproducible, dynamically cross-linked polyurethane materials. This material can then be thermally processed into polyurethane devices of various shapes and forms, and exhibits self-healing capabilities based on the dynamic reversible nature of the boron-oxygen bond. This method is simple, low-cost, significantly reduces environmental pollution, and improves the recovery rate of polyurethane, providing a new solution for the sustainable use of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the reaction for preparing recycled polyurethane material according to the present invention.

[0018] Figure 2 The present invention provides a flow chart for preparing recycled polyurethane materials.

[0019] Figure 3 This is a physical picture of the recycled polyurethane material tablet in Example 1.

[0020] Figure 4 This is a physical picture of the dumbbell-shaped spline of the recycled polyurethane material in Example 1.

[0021] Figure 5 This is the stress-strain diagram of the spline of Example 1.

[0022] Figure 6 The stress-strain diagram of the specimen in Example 4 before and after repeated processing.

[0023] Figure 7 The circular piece is obtained by hot pressing the recycled polyurethane material of Example 5.

[0024] Figure 8 This is the frequency sweep curve of the recycled polyurethane material in Example 5. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] Materials such as polyurethane rigid foam have a high degree of cross-linking, and coupled with the presence of rigid structures such as aromatic rings in the polymer molecules, the material cannot exhibit plasticity even when heated at high temperatures until it decomposes, and is susceptible to thermal oxidative degradation.

[0027] In order to solve the problem that cross-linked polyurethane materials such as polyurethane rigid foam are difficult to repeatedly heat-process, the present invention has developed a method for implanting a dynamic borate cross-linking network into the polyurethane structure to achieve plasticization of the cross-linked polyurethane. Specifically, based on the exchange reaction between carbamate and borate groups, a borate soft segment is inserted into the polyurethane hard segment cross-linking network. On the one hand, the cross-linking degree of the cross-linked polyurethane is reduced. On the other hand, the dynamic boron-oxygen bond on the molecular chain is used to achieve the transformation and reorganization of the polyurethane cross-linking network structure, synergistically promoting the transformation of the cross-linked polyurethane into a plasticizable and reprocessable direction.

[0028] A method for plasticizing a cross-linked polyurethane material comprises the following steps: Boric acid compounds, hydroxyl compounds and cross-linked polyurethane materials are used as raw materials. The boric acid compounds and hydroxyl compounds react in situ to generate borane polymers. Then, the cross-linked polyurethane materials and the borane polymers undergo heat exchange reaction under a protective gas atmosphere to prepare recycled polyurethane materials.

[0029] The present invention utilizes the component exchange reaction between the carbamate bond and the borate bond in the polyurethane molecular structure to implant the dynamic boron-oxygen bond in the borane polymer into the cross-linked polyurethane material, thereby converting the traditional thermosetting polymer polyurethane into a reproducible dynamic cross-linked polyurethane. The specific reaction diagram is shown in FIG. Figure 1 As shown, formula (1) is a cross-linked polyurethane, which is mainly a recycled polyurethane prepared by reacting an isocyanate monomer with a hydroxyl monomer and an additive (one or more of a catalyst, water, and a foam leveler). The polyurethane material and the synthetic raw materials and components are not specifically limited. Any polymer with a carbamate bond can be plasticized by the present invention. The present invention synthesizes a cross-linked polyurethane as a research object. As a compound of formula (1), it is prepared by mixing component A and component B, wherein component A is diphenylmethane diisocyanate (MDI) and component B is a polyether mixture (polyether, ethylene glycol, water, A33 catalyst).

[0030] Specifically, in the following examples, the cross-linked polyurethane used was obtained according to the following preparation method: 50 wt% of MDI, 40 wt% of polypropylene glycol 400, 6 wt% of ethylene glycol, 0.5 wt% of water and 3.5 wt% of A33 catalyst were weighed according to mass percentage, and the polypropylene glycol 400, ethylene glycol, water and A33 catalyst were uniformly mixed at room temperature to prepare a white material.

[0031] The white material was added to diphenylmethane diisocyanate (MDI) as the black material, and the two were rapidly stirred and mixed at room temperature in a volume ratio of 1:1.1. Stirring was stopped when foam began to be generated. After standing for 3 hours, a cross-linked polyurethane was obtained. The polyurethanes used in the following examples were all obtained according to this method.

[0032] Formula (2) is a polymer dynamically cross-linked by boron-oxygen bonds, namely a boron-oxygen polymer, which is prepared by reacting boric acid with hydroxyl compounds such as ethylene glycol and polymer polyols.

[0033] Formula (3) and formula (4) are polyurethane materials obtained by the blending reaction of the cross-linked polyurethane material of formula (1) and the boroxy polymer of formula (2). During the preparation process, the cross-linked polyurethane material of formula (1) and the boroxy polymer of formula (2) can be directly mixed and heated for reaction. The boroxy polymer of formula (2) can be synthesized in advance and then directly mixed and heated with the cross-linked polyurethane material of formula (1), or the boroxy polymer of formula (2) can be generated in situ by directly adding boric acid compounds, hydroxyl compounds and other reaction raw materials to the cross-linked polyurethane material of formula (1). Figure 2 As shown, the recycled polyurethane material prepared according to the preparation method of the present invention has relatively high transparency.

[0034] In a preferred embodiment of the present invention, the mass ratio of the cross-linked polyurethane material to the boron oxide polymer is 1:0.05-50.

[0035] In the process of preparing the recycled polyurethane material of formula (3), the cross-linked polyurethane material of formula (1) and the boron oxide polymer of formula (2) can be fully mixed by a dispersing and blending device such as a crusher, a mixer, a grinder, a ball mill, a sand mill, etc., and then placed in a mold for hot pressing. Preferably, the reaction temperature of the heat exchange reaction is 160° C. to 220° C., the reaction time is 0.5 h to 2 h, and the pressure is 0.1 MPa to 10 MPa.

[0036] In a preferred embodiment of the present invention, the amounts of the boric acid compound and the hydroxyl compound are followed by reacting the borohydroxyl compound and the alkanehydroxyl compound in a molar ratio of 1:1 to 1.2 to obtain a dynamic borate ester network connected by boron-oxygen bonds, in which theoretically no free hydroxyl residues are present or the influence of trace residual hydroxyl residues is negligible.

[0037] In a preferred embodiment of the present invention, the in-situ reaction temperature is between 40° C. and 160° C., and the reaction time is between 0.5 h and 6 h. During the reaction, the boric acid compound and the hydroxyl compound are controlled to react on the surface of the polyurethane material.

[0038] In a preferred embodiment of the present invention, the boronic acid compound is one or more of boric acid, alkylboronic acids (e.g., monoboronic acid compounds such as methylboronic acid, ethylboronic acid, propylboronic acid, and isopropylboronic acid, and polyboronic acid compounds such as 1,4-diboronic acid and 1,6-diboronic acid), and arylboronic acids (e.g., phenylboronic acid, methylphenylboronic acid, aminophenylboronic acid, and carboxylphenylboronic acid). The present invention does not impose a specific limit on the number of boronic acid groups in the molecule; it is typically 1-3.

[0039] In a preferred embodiment of the present invention, the hydroxy compound is a monohydroxy compound (such as methanol, ethanol, isopropanol), a polyol compound (such as ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, glycerol, pentaerythritol), a polyester polyol [such as polypropylene glycol (PPG), polyethylene glycol, hydroxy-terminated polybutylene succinate] or a polyether polyol.

[0040] The hydroxyl-terminated polybutylene adipate used in the present invention was purchased from Jining Huakai Resin Co., Ltd., model number PBA1000; the hydroxyl-terminated polycaprolactone was purchased from Xuzhou Yihuiyang New Materials Co., Ltd., model number PCL1000.

[0041] Example 1 Step 1. Take a clean 200mL beaker, add 18.55g of boric acid and 80.00g of PPG-400 at room temperature, stir thoroughly and heat to dissolve, then place in a vacuum oven at 120°C for 2h to obtain a solid state dynamic cross-linked polymer, i.e., a boroxypolymer. When adding the materials, the reaction between the boric acid and the hydroxyl functional group of PPG is controlled. The resulting boroxypolymer is theoretically formed by reversible cross-linking of boron-oxygen bonds, ignoring the influence of a very small amount of unreacted functional groups that may remain in the system.

[0042] Step 2: Weigh 20.00 g of polyurethane and 8.00 g of the synthesized boron oxide polymer, crush and mix them using a grinder, and place the evenly mixed reactants in a nitrogen atmosphere at 200° C. for 30 minutes to obtain a treated recycled polyurethane material.

[0043] Example 2 Step 1. Take a clean 200mL beaker, add 6.183g of boric acid and 66.67g of end-hydroxy polybutylene adipate (molecular weight 1000) at room temperature, stir thoroughly and heat to dissolve, then place in a vacuum oven at 120°C to react for 2 hours to obtain a solid state dynamic cross-linked polymer, namely, a boroxy polymer. When adding the materials, control the reaction between boric acid and the hydroxyl functional groups of PPG. The resulting boroxy polymer is theoretically formed by reversible cross-linking of boron-oxygen bonds, ignoring the influence of a very small amount of unreacted functional groups that may remain in the system.

[0044] Step 2: Weigh 20.00 g of polyurethane and 8.00 g of the synthesized boron oxide polymer, stir them briefly and extrude them together using a single-screw extruder. During the process, the components undergo heat exchange reaction simultaneously, the reaction temperature is controlled at 180°C, and the residence time is 1 hour to obtain the treated recycled polyurethane material.

[0045] Example 3 Step 1. Take a clean 200mL beaker, add 6.183g of boric acid and 40.00g of terminal hydroxyl polycaprolactone (molecular weight 1000) at room temperature, stir thoroughly and heat to dissolve, then place in a vacuum oven at 120°C to react for 2 hours to obtain a solid state dynamic cross-linked polymer, namely, a boroxy polymer. When adding the materials, control the reaction between boric acid and the hydroxyl functional groups of PPG. The resulting boroxy polymer is theoretically formed by reversible cross-linking of boron-oxygen bonds, ignoring the influence of a very small amount of unreacted functional groups that may remain in the system.

[0046] Step 2: Weigh 20.00 g of polyurethane and 12.00 g of the synthesized borane polymer, stir and mix briefly, and then use a twin-screw extruder to extrude the two. During the process, the components undergo heat exchange reaction simultaneously. Under a nitrogen atmosphere, the reaction temperature is controlled at 200° C. and the residence time is 30 min to obtain the treated polyurethane material.

[0047] Example 4 Step 1. Take a clean 200mL beaker, add 18.55g of boric acid and 32.00g of PPG-1000 at room temperature, stir thoroughly, and then place in a vacuum oven at 120°C for 2 hours to obtain a solid state dynamic cross-linked polymer, i.e., a boroxypolymer. When adding the materials, the reaction between the boric acid and the hydroxyl functional groups of PPG is controlled. The resulting boroxypolymer is theoretically formed by reversible cross-linking of boron-oxygen bonds, ignoring the influence of a very small amount of unreacted functional groups that may remain in the system.

[0048] Step 2: Weigh 20.00 g of polyurethane and 12.00 g of the synthesized boron oxide polymer, crush them using a grinder, blend them evenly, and then place them in a mold for hot pressing. Control the reaction temperature to 180°C, the pressure to 0.2 MPa, and the residence time to 1 h to obtain the treated recycled polyurethane material.

[0049] Example 5 Take a clean 200mL beaker, add 20.00g of polyurethane, 4.64g of boric acid, and 8.00g of PPG-1000, stir thoroughly, and place in a vacuum oven at 120°C for reaction for 2h. Then place the reactants in a mold for hot pressing, control the reaction temperature to 180°C, the pressure to 0.2MPa, and the residence time to 1h to obtain the treated recycled polyurethane material.

[0050] Example 6 Step 1. Take a clean 200mL beaker, add 18.55g of boric acid and 32.00g of PPG-1000 at room temperature, stir thoroughly, and place in a vacuum oven at 40°C for 6 hours to obtain a solid state dynamic cross-linked polymer, i.e., a boroxypolymer. When adding the materials, the reaction between the boric acid and the hydroxyl functional group of PPG is controlled. The resulting boroxypolymer is theoretically formed by reversible cross-linking of boron-oxygen bonds, ignoring the influence of a very small amount of unreacted functional groups that may remain in the system.

[0051] Step 2: Weigh 20.00 g of polyurethane and 1.00 g of the synthesized boron oxide polymer, crush them using a grinder, blend them evenly, and then place them in a mold for hot pressing. Control the reaction temperature to 220°C, the pressure to 0.1 MPa, and the residence time to 0.5 h to obtain the treated recycled polyurethane material.

[0052] Example 7 Step 1. Take a clean 200mL beaker, add 18.55g of boric acid and 32.00g of PPG-1000 at room temperature, stir thoroughly, and then place in a vacuum oven at 160°C for 0.5h to obtain a solid state dynamic cross-linked polymer, i.e., a boroxypolymer. When adding the materials, the boric acid is controlled to react with the hydroxyl functional groups of PPG. The resulting boroxypolymer is theoretically formed by reversible cross-linking of boron-oxygen bonds, ignoring the influence of a very small amount of unreacted functional groups that may remain in the system.

[0053] Step 2: Weigh 2.00 g of polyurethane and 100.00 g of the synthesized borane polymer, crush them using a grinder, blend them evenly, and then place them in a mold for hot pressing. Control the reaction temperature to 160° C., the pressure to 0.1 MPa, and the residence time to 2 h to obtain the treated recycled polyurethane material.

[0054] Comparative Example 1 Directly heat-process the polyurethane foam material. The cross-linked polyurethane is placed in a circular mold with a diameter of 20 mm and hot-pressed using a hot press. The temperature is set to 200°C, the pressure is 0.3 MPa, and the hot pressing time is 10 minutes. The resulting disc is 20 mm in diameter and has a brittle and hard texture. The components are unevenly distributed and opaque, and the appearance is like a compressed biscuit ( Figure 6 ).

[0055] The polyurethane materials obtained in Examples 1 to 4 were taken out and placed in a circular mold (diameter 50 mm). The materials were hot pressed using a hot press. The temperature was set to 200°C, the pressure was 0.3 MPa, and the hot pressing time was 10 min. Transparent polyurethane discs with a diameter of 50 mm and uniform texture were obtained. This shows that the method of the present invention can convert non-heat-processable polyurethane into a polyurethane plastic that can be repeatedly heat-processed. Figure 3 shown.

[0056] Use a cutter to cut the polyurethane disc obtained by heat pressing to obtain dumbbell-shaped splines, such as Figure 4 As shown. The tensile properties of the dumbbell-shaped splines of Example 1 and Example 4 were tested using an electronic universal testing machine at a rate of 1 mm / min until the splines broke, and the broken splines were placed back into the mold and hot-pressed again to obtain dumbbell-shaped splines. The stress-strain curves of the materials are shown as follows: Figure 5 and Figure 6As shown. Figure 5 It can be seen that the tensile strength of the sample obtained in Example 1 is about 5.7 MPa, the elongation at break is about 50%, and the Young's modulus is 20 MPa, while the elongation at break of the sample in Example 4 with a higher proportion of soft segments reaches 230%, the tensile strength is 1.5 MPa, and the Young's modulus is 0.6 MPa. The samples in each embodiment can be repeatedly processed, such as Figure 6 As shown in the figure, the tensile properties of the samples after repeated processing remain basically unchanged.

[0057] The sample obtained in Example 5 was repeatedly processed using a hot press to obtain Figure 7 The disc with a diameter of 20 mm and a thickness of 0.3 mm was subjected to frequency sweep at 200°C using a rotational rheometer, and the following results were obtained: Figure 8 The frequency sweep curve is shown. It was found that the shear modulus of the material was stable at around 50 kPa, while the untreated polyurethane still had a high hardness even at 200°C, making it impossible to hot-press mold and difficult to perform corresponding tests.

[0058] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0059] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for plasticizing a cross-linked polyurethane material, characterized in that: The following steps are involved: Boric acid compounds, hydroxyl compounds and cross-linked polyurethane materials are used as raw materials. The boric acid compounds and hydroxyl compounds react in situ to generate boron oxide polymers. Then, the cross-linked polyurethane materials and the boron oxide polymers undergo heat exchange reaction to prepare recycled polyurethane materials.

2. The method for plasticizing a cross-linked polyurethane material according to claim 1, wherein: The mass ratio of the cross-linked polyurethane material to the boron oxide polymer is 1:0.05~50.

3. The cross-linked polyurethane material plasticization transformation method according to claim 1, characterized in that: The reaction temperature of the heat exchange reaction is 160° C. to 220° C., the reaction time is 0.5 h to 2 h, and the pressure is 0.1 MPa to 10 MPa.

4. The method for plasticizing and transforming a cross-linked polyurethane material according to claim 1, wherein: The molar ratio of the boron hydroxyl group in the boric acid compound to the alkylhydroxyl group in the hydroxyl compound is 1:1 to 1.

2.

5. The method for plasticizing and transforming a cross-linked polyurethane material according to claim 1, characterized in that: The in-situ reaction temperature is 40°C~160°C, and the reaction time is 0.5h~6h.

6. The cross-linked polyurethane material plasticization transformation method according to claim 1, characterized in that: The boronic acid compound is one or more of boric acid, alkylboronic acid and arylboronic acid.

7. The method for plasticizing and transforming a cross-linked polyurethane material according to claim 1, characterized in that: The hydroxy compound is a monohydroxy compound, a polyol compound, a polyester polyol or a polyether polyol.

8. A recycled polyurethane material prepared by the method according to any one of claims 1 to 7.

9. Use of the recycled polyurethane material according to claim 8 in automobile manufacturing materials, textile materials, electronic and electrical appliance materials, and adhesive materials.

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