Flexible temperature-resistant PBO polymer and preparation process thereof

Abstract

The invention discloses a flexible temperature-resistant PBO polymer and a preparation process thereof.The preparation process comprises the steps that polyphosphoric acid is heated and then fed into a degassing kettle, 4, 6-diamino resorcinol hydrochloride, aromatic dicarboxylic acid and phosphorus pentoxide are added into the degassing kettle, degassing is conducted in the degassing kettle, prepolymerization and defoaming are conducted after degassing is completed, and a prepolymer material is obtained; the preparation method comprises the following steps: preparing a pre-polymer material, pressing the pre-polymer material into a screw extruder through a hydraulic machine, carrying out post-polymerization reaction on the pre-polymer material in the screw extruder, filtering through a filter, defoaming to obtain a post-polymer material, extruding the post-polymer material from a mold, and washing with water to obtain the flexible temperature-resistant PBO polymer. The PBO polymer prepared by the invention has temperature resistance similar to that of para-position PBO, but has lower requirements on preparation conditions, higher solubility in a polyphosphoric acid system and better processability of a polymerization stock solution, and the PBO polymer has the potential of being used for preparing low-cost ultrahigh-temperature-resistant paper or clothing fibers.

Description

Technical Field

[0001] The present invention discloses a flexible heat-resistant PBO polymer and a preparation process thereof, and specifically relates to a heat-resistant polyphenylene benzobisoxazole (PBO) polymer with a flexible chain and a polymerization process thereof, and belongs to the technical field of special polymer synthesis. Background Art

[0002] PBO is the abbreviation of polyphenylene bisoxazole. Para-PBO fiber is a high-performance fiber made by spinning para-PBO polymer. PBO fiber is a special organic fiber with the highest tensile strength, tensile modulus and thermal stability among all high-performance organic fibers. Its unique and excellent performance mainly comes from the particularity of its molecular structure. The heterocyclic structural unit of phenylene bisoxazole on the molecular chain provides high thermal stability and mechanical properties for PBO polymerization. PBO research began in the 1960s. In 1994, DOW and Toyobo of Japan cooperated in the development of PBO fiber. In 1998, a 180-ton / year PBO fiber production line was successfully realized. PBO fiber was launched on the market under the trade name of "Zylon" and is used to make high-performance composite materials, such as heat-resistant materials, impact-resistant and riot-proof materials and structural stealth materials, which are widely used in high-tech fields such as aerospace, aviation and national defense. At present, the PBO polymers on the market are usually prepared by polymerizing diaminodiphenol hydrochloride (DAR) and terephthalic acid (TPA) in polyphosphoric acid (PPA) to obtain high-strength, high-temperature-resistant rigid polymers. The use of terephthalic acid makes its molecular chain have extremely high rigidity and liquid crystal properties, which also makes its polymer solution dynamic viscosity extremely high (>20kPa.s), and has strict requirements on processing and extrusion conditions. Although the molded fiber has high strength and good heat resistance, it has high crystallinity, poor dyeability and poor flexibility. As a fiber for clothing, it is difficult to process and has poor comfort. There is also PBI fiber for heat-resistant clothing of the same level as PBO, but it is expensive and the technology is monopolized. Therefore, in the field of high-temperature protective fabrics, there is an urgent need for a more processable, comfortable and economical heat-resistant fiber to replace the existing PBO or PBI fiber.

[0003] In the prior art, patent CN202111546188.6 discloses a method for synthesizing a poly(p-phenylene benzobisoxazole) copolymer containing a flexible alkylene chain segment by gradually heating up the solution polycondensation reaction of monomers 4,6-diamino-1,3-benzenediol hydrochloride, terephthalic acid, adipic acid, and sebacic acid in a polyphosphoric acid system. The method retains the excellent properties of poly(p-phenylene benzobisoxazole), namely high tensile strength, high modulus, and high heat resistance, and improves its molding and processing properties. It has the characteristic of being meltable when heated and is suitable for the subsequent melt spinning preparation process, but the fiber has poor temperature resistance.

[0004] Patent CN202110155077.6 discloses a phenylene benzobisoxazole polymer obtained by copolymerizing 4,6-diaminoresorcinol with terephthalic acid and a dicarboxyl monomer capable of forming a flexible chain segment, which can make the fiber have both high strength and excellent toughness and significantly improved elongation at break, making it better used in the fields of rubber and anti-ballistic protection. In this patent, the proportion of flexible chain functional groups added is as low as 1%-10% of terephthalic acid to ensure that the fiber has higher strength on the basis of improving elongation. Its elongation is less than 5%, and the dynamic viscosity of the original solution is still very large.

[0005] Although the above patents can increase the flexibility of PBO or change the processability, they are all based on making small improvements in elongation and processability on the basis of PBO's high strength and high modulus. The fiber elongation is less than 10%, and it is not a modification of the fiber for clothing fabrics. The flexibility of the fiber still does not meet the requirements for clothing fabrics. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation process of a flexible and heat-resistant PBO polymer. On the basis of the existing polymerization process, the flexibility and processing performance of the PBO polymer are improved by adaptive selection and compounding of aromatic dicarboxylic acid monomers, so that it is more suitable for the field of clothing and industrial non-woven fabrics than the existing PBO polymer containing flexible segments, and meets the spinning performance and index requirements of PBO fibers in this field. To this end, the present invention also provides a flexible and heat-resistant PBO polymer obtained by the preparation process.

[0007] The invention is achieved through the following technical scheme: a preparation process of a flexible and heat-resistant PBO polymer, wherein polyphosphoric acid is heated and then sent into a degassing kettle, 4,6-diaminoresorcinol hydrochloride, aromatic dicarboxylic acid and phosphorus pentoxide are added into the degassing kettle, degassed in the degassing kettle, and after degassing, the prepolymerized material is sent into a mixing kettle for prepolymerization and degassing to obtain a prepolymerized material; then the temperature of the mixing kettle is increased, the prepolymerized material is pressed into a storage tank, and then the prepolymerized material is pressed into a screw extruder through a hydraulic press, the prepolymerized material undergoes a post-polymerization reaction in the screw extruder, and then filtered through a filter and degassed to obtain a post-polymerized material, and then the post-polymerized material is extruded from a mold, and washed with water to obtain a flexible and heat-resistant PBO polymer.

[0008] The aromatic dicarboxylic acid is a mixture of at least one non-functional linear symmetrical aromatic dicarboxylic acid monomer and terephthalic acid, and the molar ratio of at least one non-functional linear symmetrical aromatic dicarboxylic acid monomer to terephthalic acid is 0.2-3:0-1.

[0009] The mass ratio of 4,6-diaminoresorcinol hydrochloride to aromatic dicarboxylic acid added to the degassing kettle is 1:0.97-1.05.

[0010] In the degassing kettle, the added amounts of polyphosphoric acid and phosphorus pentoxide are calculated according to the solid content of the prepolymerized material and the mass percentage of phosphorus pentoxide at the end of the reaction, so that the solid content of the prepolymerized material is 3-20%.

[0011] The non-functional group linear symmetric aromatic dicarboxylic acid monomer includes isophthalic acid, 4,4'-diphenyl ether dicarboxylic acid or 3,4'-diphenyl ether dicarboxylic acid.

[0012] The reaction temperature of the prepolymerization is controlled at 80-120°C.

[0013] The temperature range of the screw extruder is controlled at 200-280°C.

[0014] The thermal decomposition temperature of the flexible temperature-resistant PBO polymer is ≥600°C, the limiting oxygen index (LOI) is ≥50%, and the intrinsic viscosity η is ≤15dL / g.

[0015] A flexible temperature-resistant PBO polymer is prepared by adopting the preparation process.

[0016] The reaction formula involved in the present invention is as follows: Wherein, R is isophthalic acid, 4,4'-diphenyl ether dicarboxylic acid or 3,4'-diphenyl ether dicarboxylic acid.

[0017] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The present invention provides for the first time a flexible, heat-resistant PBO polymer suitable for use in the processing of clothing and industrial non-woven fabrics. Although the prior art has disclosed that the combination of terephthalic acid and dicarboxyl monomers can provide a flexible segment for the PBO polymer, it can only improve the flexibility and processing performance of the PBO polymer to a certain extent, and slightly improve the fiber elongation, and is still difficult to be used in the field of clothing and industrial non-woven fabrics. The present invention innovatively utilizes a specific compound combination of aromatic dicarboxylic acid monomers to introduce a greater degree of flexible segments, making the stock solution have a lower dynamic viscosity and better processability, and its fibers are more suitable for contact with the human body. Therefore, it is more suitable for the field of clothing and industrial non-woven fabrics and meets the spinning performance and index requirements of PBO fibers in this field.

[0018] (2) The flexible and heat-resistant PBO polymer prepared by the method of the present invention not only has higher flexibility and processing performance, but also has a lower intrinsic viscosity. The dynamic viscosity of the stock solution with the same solid content is also lower, but the temperature resistance is still excellent. Although the limiting oxygen index is reduced, it still has excellent flame retardant properties. Therefore, this type of flexible chain PBO polymer has better processing performance. Under the same dynamic viscosity requirements, a higher solid content polymer stock solution can be obtained, which is also more helpful to improve spinning efficiency and reduce spinning costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the thermogravimetric analysis spectrum of the flexible temperature-resistant PBO polymer in Example 4 of the present invention. DETAILED DESCRIPTION

[0020] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0021] Embodiment 1: Step 1: Degassing, prepolymerization and degassing 1167kg of polyphosphoric acid was heated at 80℃ for 60 minutes, then put into a degassing kettle, and then 389kg of 4,6-diaminoresorcinol hydrochloride, 151.65kg of terephthalic acid, 151.65kg of isophthalic acid and 792.85kg of phosphorus pentoxide were added, and degassed in the degassing kettle for 2 hours. After degassing, the degassed materials were sent to a mixing kettle, prepolymerized at 80℃ for 3 hours, and then defoamed at 100℃ for 2 hours to obtain a prepolymerized material.

[0022] In this step, the molar ratio of terephthalic acid to isophthalic acid is 1:1.

[0023] Step 2: Post-polymerization and degassing After degassing, the temperature of the mixing kettle is raised to 110°C, and the prepolymerized material is pressed into a storage tank. The prepolymerized material is then pressed into a screw extruder through a hydraulic press that can precisely control the flow rate. The hydraulic press controls the discharge speed to 10 ml / min and the screw temperature to 230°C. The prepolymerized material undergoes a post-polymerization reaction in the screw extruder, and then is degassed after being filtered through a filter. The prepolymerized material is extruded through a mold and washed with water to obtain a flexible, temperature-resistant PBO polymer, wherein the solid content of the polymerization stock solution is 16%.

[0024] Embodiment 2: Step 1: Degassing, prepolymerization and degassing 1157 kg of polyphosphoric acid was heated at 100°C for 60 minutes, then put into a degassing kettle, and then 385.66 kg of 4,6-diaminoresorcinol hydrochloride, 100.24 kg of terephthalic acid, 311.62 kg of 4,4'-diphenyl ether dicarboxylic acid and 786.06 kg of phosphorus pentoxide were added, and degassed in the degassing kettle for 2 hours. After degassing, the degassed materials were sent to a mixing kettle, prepolymerized at 120°C for 3 hours, and then defoamed at 100°C for 2 hours to obtain a prepolymerized material.

[0025] In this step, the molar ratio of terephthalic acid to isophthalic acid is 1:2 Step 2: Post-polymerization and degassing After degassing, the temperature of the mixing kettle is raised to 120°C, and the prepolymerized material is pressed into a storage tank. The prepolymerized material is then pressed into a screw extruder through a hydraulic press that can precisely control the flow rate. The hydraulic press controls the discharge speed to 10 ml / min and the screw temperature to 220°C. The prepolymerized material undergoes a post-polymerization reaction in the screw extruder, and then is filtered through a filter for degassing, extruded through a mold, and washed with water to obtain a flexible, temperature-resistant PBO polymer, wherein the solid content of the polymerization stock solution is 19.52%.

[0026] Embodiment 3: Step 1: Degassing, prepolymerization and degassing 1124 kg of polyphosphoric acid was heated at 100°C for 60 minutes, then put into a degassing kettle, and then 374.66 kg of 4,6-diaminoresorcinol hydrochloride, 97.38 kg of terephthalic acid, 97.38 kg of isophthalic acid, 151.37 kg of 4,4'-diphenyl ether dicarboxylic acid and 763.64 kg of phosphorus pentoxide were added, and degassed in the degassing kettle for 2 hours. After degassing, the degassed materials were sent to a mixing kettle, prepolymerized at 80-120°C for 3 hours, and then defoamed at 100°C for 2 hours to obtain a prepolymerized material.

[0027] In this step, the molar ratio of terephthalic acid, isophthalic acid and 4,4'-diphenyl ether dicarboxylic acid is 1:1:1.

[0028] Step 2: Post-polymerization and degassing After degassing, the temperature of the mixing kettle is raised to 110°C, and the prepolymerized material is pressed into a storage tank. The prepolymerized material is then pressed into a screw extruder through a hydraulic press that can precisely control the flow rate. The hydraulic press controls the discharge speed to 10 ml / min and the screw temperature to 250°C. The prepolymerized material undergoes a post-polymerization reaction in the screw extruder, and then is degassed after being filtered through a filter. The prepolymerized material is extruded through a mold and washed with water to obtain a flexible, temperature-resistant PBO polymer, wherein the solid content of the polymerization stock solution is 17.86%.

[0029] Embodiment 4: Step 1: Degassing, prepolymerization and degassing 1124 kg of polyphosphoric acid was heated at 100°C for 60 minutes, then put into a degassing kettle, and then 379.66 kg of 4,6-diaminoresorcinol hydrochloride, 269.13 kg of terephthalic acid, 26.91 kg of isophthalic acid, 41.83 kg of 3,4'-diphenyl ether dicarboxylic acid and 773.83 kg of phosphorus pentoxide were added, and degassed in the degassing kettle for 2 hours. After degassing, the degassed materials were sent to a mixing kettle, prepolymerized at 80-120°C for 2 hours, and then defoamed at 100°C for 2 hours to obtain a prepolymerized material.

[0030] In this step, the molar ratio of terephthalic acid, isophthalic acid and 3,4'-diphenyl ether dicarboxylic acid is 1:0.1:0.1.

[0031] Step 2: Post-polymerization and degassing After degassing, the temperature of the mixing kettle is raised to 110°C, and the prepolymerized material is pressed into a storage tank. The prepolymerized material is then pressed into a screw extruder through a hydraulic press that can precisely control the flow rate. The hydraulic press controls the discharge speed to 10ml / min and the screw temperature to 280°C. The prepolymerized material undergoes a post-polymerization reaction in the screw extruder, and then is degassed after being filtered through a filter. The prepolymerized material is extruded through a mold and washed with water to obtain a flexible, temperature-resistant PBO polymer, in which the solid content of the polymerization stock solution is 16.6%.

[0032] The characteristic thermogravimetric test of the flexible temperature-resistant PBO polymer was carried out, such as Figure 1 As shown in the figure, it can be seen that the thermal decomposition temperature of this polymer is 636°C.

[0033] Embodiment 5: Step 1: Degassing, prepolymerization and degassing 1167kg of polyphosphoric acid was heated at 80°C for 60 minutes, then put into a degassing kettle, and then 389kg of 4,6-diaminoresorcinol hydrochloride, 303.30kg of isophthalic acid and 792.85kg of phosphorus pentoxide were added, and degassed in the degassing kettle for 2 hours. After degassing, the degassed materials were sent to a mixing kettle, prepolymerized at 80-120°C for 3 hours, and then defoamed at 90°C for 2 hours to obtain a prepolymerized material.

[0034] Step 2: Post-polymerization and degassing After degassing, the temperature of the mixing kettle is raised to 110°C, and the prepolymerized material is pressed into a storage tank. The prepolymerized material is then pressed into a screw extruder through a hydraulic press that can precisely control the flow rate. The hydraulic press controls the discharge speed to 10 ml / min and the screw temperature to 230°C. The prepolymerized material undergoes a post-polymerization reaction in the screw extruder, and then is degassed after being filtered through a filter. The prepolymerized material is extruded through a mold and washed with water to obtain a flexible, temperature-resistant PBO polymer, wherein the solid content of the polymerization stock solution is 16%.

[0035] Comparative Example 1: This comparative example adopts the same preparation process as Example 5, with the only difference being that the isophthalic acid in Example 5 is replaced by an equal amount of terephthalic acid, and the feed amounts of other materials and the control parameters of each process are all the same, thereby obtaining a PBO polymer, wherein the solid content of the polymerization stock solution is 16%.

[0036] Comparative Example 2: This comparative example adopts the same preparation process as Example 5, with the only difference being that the isophthalic acid in Example 5 is replaced by 288.14 kg of terephthalic acid and 15.16 kg of isophthalic acid, the molar ratio of terephthalic acid to isophthalic acid is 1:0.1, and the feed amounts of other materials and the control parameters of each process are all equal, thereby obtaining a PBO polymer, wherein the solid content of the polymerization stock solution is 16%.

[0037] Comparative Example 3: This comparative example adopts the same preparation process as Example 5, with the only difference being that the isophthalic acid in Example 5 is replaced by 300.27 kg of terephthalic acid and 4.71 kg of 4,4'-diphenyl ether dicarboxylic acid, the molar ratio of terephthalic acid to 4,4'-diphenyl ether dicarboxylic acid is 9.9:0.1, and the feed amounts of other materials and the control parameters of each process are all equal, thereby obtaining a PBO polymer, wherein the solid content of the polymerization stock solution is 16%.

[0038] The performance of the flexible heat-resistant PBO polymers of Examples 1 to 5 and the PBO polymers of Comparative Examples 1 to 3 was tested. The test method and test results are as follows: The intrinsic viscosity η was tested using the Ubbelohde viscometer 5-point method. 0.008 g of the resin was weighed and dissolved in 25 ml of methanesulfonic acid at a water bath temperature of 29.7°C.

[0039] The limiting oxygen index is tested according to the standard GB / T5454-1997.

[0040] The thermal decomposition temperature test is carried out according to the standard GB / T 33047.1-2016.

[0041] Table 1 Test results of resins in examples and comparative examples It can be seen from the test results shown in Table 1 above that the flexible chain PBO polymer obtained from a specific molar ratio of terephthalic acid to aromatic dicarboxylic acid has a lower intrinsic viscosity, and the dynamic viscosity of the stock solution with the same solid content is also lower, but the temperature resistance is still excellent. Although the limiting oxygen index has decreased, it still has excellent flame retardant properties. This type of flexible chain PBO polymer has better processing performance, and a higher solid content polymer stock solution can be obtained under the same dynamic viscosity requirements, which helps to improve spinning efficiency and reduce spinning costs.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A process for preparing a flexible temperature-resistant PBO polymer, characterized in that: The polyphosphoric acid is heated and then sent to a degassing kettle, and then 4,6-diaminoresorcinol hydrochloride, aromatic dicarboxylic acid and phosphorus pentoxide are added to the degassing kettle, and degassed in the degassing kettle. After the degassing is completed, the prepolymerized material is sent to a mixing kettle for prepolymerization and degassing to obtain a prepolymerized material; then the temperature of the mixing kettle is increased, and the prepolymerized material is pressed into a storage tank, and then the prepolymerized material is pressed into a screw extruder through a hydraulic press, and the prepolymerized material is subjected to a post-polymerization reaction in the screw extruder, and then filtered through a filter and degassed to obtain a post-polymerized material, and then the post-polymerized material is extruded from a mold, and after washing with water, a flexible temperature-resistant PBO polymer is obtained; The aromatic dicarboxylic acid is a mixture of at least one non-functional linear symmetrical aromatic dicarboxylic acid monomer and terephthalic acid, and the molar ratio of at least one non-functional linear symmetrical aromatic dicarboxylic acid monomer to terephthalic acid is 0.2-3:0-1.

2. The preparation process according to claim 1, characterized in that: The mass ratio of 4,6-diaminoresorcinol hydrochloride to aromatic dicarboxylic acid added to the degassing kettle is 1:0.97-1.

05.

3. The preparation process according to claim 1, characterized in that: In the degassing kettle, the added amounts of polyphosphoric acid and phosphorus pentoxide are calculated according to the solid content of the prepolymerized material and the mass percentage of phosphorus pentoxide at the end of the reaction, so that the solid content of the prepolymerized material is 3-20%.

4. The preparation process according to claim 1, characterized in that: The non-functional group linear symmetric aromatic dicarboxylic acid monomer includes isophthalic acid, 4,4'-diphenyl ether dicarboxylic acid or 3,4'-diphenyl ether dicarboxylic acid.

5. The preparation process according to claim 1, characterized in that: The reaction temperature of the prepolymerization is controlled at 80-120°C.

6. The preparation process according to claim 1, characterized in that: The temperature range of the screw extruder is controlled at 200-280°C.

7. The preparation process according to claim 1, characterized in that: The thermal decomposition temperature of the flexible temperature-resistant PBO polymer is ≥600°C, the limiting oxygen index (LOI) is ≥50%, and the intrinsic viscosity η is ≤15dL / g.

8. A flexible temperature-resistant PBO polymer, characterized in that: The invention is prepared by the preparation process according to any one of claims 1 to 7.

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