A group-modified phenol-aldehyde resin and a method for producing a high-strength phenol-aldehyde fiber

Abstract

The application discloses a group modified phenolic resin and a method for preparing high-strength phenolic fiber, and belongs to the technical field of composite materials.The group modified phenolic resin prepared in a unique way is placed in a spinning tank together with a linear polymer, and is heated and melted; pressure is applied under an inert atmosphere so that the melt is sprayed through a spinning assembly to form phenolic fiber filaments; the phenolic fiber filaments are collected on a collecting roller; the obtained phenolic fiber filaments are soaked in a cross-linking and curing liquid, and are subjected to the procedures of cross-linking and curing by temperature rising, cleaning and drying, so that high-strength phenolic fiber is obtained.The application can improve the spinnability and spinning continuity in the process of melt spinning, solve the problems of melt point mismatch and easy decomposition of the phenolic resin in the traditional blending modification method, improve the mechanical strength of the obtained phenolic fiber filaments, and further bring benefits to the subsequent cross-linking and curing process, so that high-strength phenolic fiber is finally obtained.

Description

Technical Field

[0001] This invention belongs to the field of composite material technology, specifically relating to a group-modified phenolic resin and a method for preparing high-strength phenolic fibers. Background Technology

[0002] Phenolic fiber is an organic fiber with a three-dimensional cross-linked structure. As an organic fiber with important practical value, it is also a precursor to fibers such as carbon fiber, graphite fiber, and activated carbon fiber. Phenolic fiber is an organic fiber with a highly cross-linked structure prepared from thermoplastic or thermosetting phenolic resins. It can withstand instantaneous temperatures up to 2500℃ and long-term operating temperatures of 150-180℃, exhibiting excellent thermal insulation properties. Melt spinning from thermoplastic phenolic resin is a commonly used process for preparing phenolic fiber. However, the number-average molecular weight of the phenolic resin used in melt spinning is low, and the molecular chains are formed only by linear connections between benzene rings and methylene groups. This results in extremely low strength of the phenolic fiber precursor, with a tensile strength generally around 10 MPa. This makes it prone to breakage during spinning, affecting the continuity of the spinning process. Furthermore, the low strength of the phenolic fiber precursor also presents operational difficulties for subsequent cross-linking and curing processes. Currently, the improvement of the spinnability of phenolic resin is mostly achieved by directly melt-blending phenolic resin with linear polymers. During the melt-blending process, the matching degree of melting points between phenolic resin and linear polymer needs to be considered. If the temperature is too low, the two will not melt completely, and if the temperature is too high, the phenolic resin may decompose. In the cross-linking and curing process, formaldehyde is often chosen as the cross-linking agent, which has the problem of high toxicity. Summary of the Invention

[0003] To address the technical problems existing in the prior art, this invention provides a group-modified phenolic resin and a method for preparing high-strength phenolic fibers using this group-modified phenolic resin. On the one hand, it adjusts the melting point of the phenolic resin, solving the problems of melting point mismatch and easy decomposition of phenolic resin in traditional blending modification methods. On the other hand, it increases the complexity of the phenolic resin molecular chain, improving the spinnability of the resin itself, enhancing the mechanical properties of the phenolic fiber precursor, and strengthening the operability of the crosslinking and curing process. This invention uses a process of melt blending a self-synthesized group-modified thermoplastic phenolic resin with a linear polymer and preparing high-strength phenolic fiber precursors through melt spinning. The precursors are then placed in a crosslinking curing solution and cured in a single heating process to produce phenolic fibers with high mechanical strength. This achieves a continuous and efficient melt spinning process for phenolic fibers. Simultaneously, the use of other methylene donors as crosslinking agents reduces the harmful effects of formaldehyde, providing a new approach for the preparation of high-strength phenolic fibers.

[0004] The technical approach adopted in this invention is as follows:

[0005] A group-modified phenolic resin has the following molecular structural formula:

[0006]

[0007] Where n1≥1, n2≥1, n1+n2=8~15, and the R group is one of -OH, -OR1, -NHCOR, -B(OR1)2, and -B(OH)2.

[0008] A method for preparing high-strength phenolic fibers using phenolic resin modified with the above-mentioned groups includes the following steps:

[0009] 1) Phenolic fiber precursor preparation steps: The group-modified phenolic resin and linear polymer are placed in a spinning tank and heated to melt. Pressure is applied under an inert atmosphere to make the melt sprayed out through the spinneret to form phenolic fiber precursor. The phenolic fiber precursor is then taken in on the take-up roller.

[0010] 2) Phenolic fiber precursor curing step: The obtained phenolic fiber precursor is immersed in cross-linking curing solution, and after heating, cross-linking curing, washing and drying, high-strength phenolic fiber is obtained.

[0011] Preferably, the linear polymer in step 1) is one or a mixture of polyamide, polyethylene, polypropylene, polyoxymethylene, and polycarbonate.

[0012] Preferably, the linear polymer in step 1) accounts for 0.1% to 10% by mass.

[0013] Preferably, the heating and melting temperature in step 1) is 120-170°C, and the process is carried out under an inert atmosphere.

[0014] Preferably, the inert atmosphere in step 1) is a nitrogen atmosphere, the pressure is 50-250 kPa, and the rotation speed of the take-up roller is 600-2000 r / min.

[0015] Preferably, the crosslinking curing solution in step 2) is a mixed solution of hydrochloric acid, hexamethylenetetramine and deionized water.

[0016] Preferably, in step 2), the mass fraction of hydrochloric acid in the crosslinking curing solution is 5% to 20%, and the mass fraction of hexamethylenetetramine is 10% to 30%.

[0017] Preferably, the soaking conditions in step 2) are: room temperature soaking pretreatment for 0 to 2 hours, and the heating conditions are: heating rate of 10 to 50°C / h, holding temperature of 90 to 180°C, and holding time of 2 to 12 hours.

[0018] Preferably, in step 2), the washing process involves repeatedly rinsing the fibers with deionized water until the pH of the washing solution is close to 7; the drying process involves drying the fibers in a blower oven at a temperature below 65°C.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) This invention adjusts the structure of phenolic resin without affecting its performance, introduces groups on the benzene ring of phenolic resin, improves its matching degree with linear polymer spinning modifiers during melt blending, improves the spinnability and spinning continuity during melt spinning, solves the problems of melting point mismatch and easy decomposition of phenolic resin in traditional blending modification methods, improves the mechanical strength of the obtained phenolic fiber precursor, and brings benefits to the subsequent cross-linking and curing process, and finally obtains high-strength phenolic fiber.

[0021] (2) In this invention, hexamethylenetetramine is selected as the methylene donor in the crosslinking and curing process, which reduces the harm caused by formaldehyde. While simplifying the process and reducing equipment costs, the mechanical strength of phenolic fiber is guaranteed. The prepared phenolic fiber filament has a smooth surface and a tensile strength of up to 25.26 MPa. The tensile strength of the fiber monofilament is 362.65 MPa. Attached Figure Description

[0022] Figure 1 This is an electron microscope image of the phenolic fiber precursor prepared in Example 1 of the present invention. Detailed Implementation

[0023] To make the various technical features, advantages, or effects of the present invention more apparent and understandable, a detailed description is provided below in conjunction with the accompanying drawings.

[0024] Example 1

[0025] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=4, R group is -OH) was placed in a spinning tank, and 0.1% polyethylene was added. The mixture was stirred and heated to 120℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 250 kPa, and a take-up roller speed of 2000 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 15:18:67. The temperature was increased to 140℃ at a heating rate of 15℃ / h and held for 3h. The fibers were then removed, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 24.55 MPa, and the tensile strength of the fiber monofilament was 290.86 MPa.

[0026] Example 2

[0027] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=6, R group is -OH) was placed in a spinning tank, and 10% polyethylene was added. The mixture was stirred and heated to 135℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 50 kPa, and a take-up roller speed of 600 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 15:15:70 and pretreated at room temperature for 0.5 h. Then, the temperature was increased to 110℃ at a heating rate of 25℃ / h and held for 5 h. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 20.23 MPa, and the tensile strength of the fiber monofilament was 306.54 MPa.

[0028] Example 3

[0029] Self-synthesized thermoplastic phenolic resin (n1=7, n2=8, R group is -B(OH)2) was placed in a spinning tank, and 5% nylon 6 was added. The mixture was stirred and heated to 170℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, 100KPa pressure, and a take-up roller speed of 1300r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 14:16:70 and pretreated at room temperature for 1 hour. Then, the temperature was increased to 160℃ at a heating rate of 15℃ / h and held for 8 hours. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 18.89MPa, and the tensile strength of the fiber monofilament was 287.35MPa.

[0030] Example 4

[0031] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=4, R group is -B(OH)2) was placed in a spinning tank, and 2% polypropylene was added. The mixture was stirred and heated to 160℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 105 kPa, and a take-up roller speed of 1200 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 16:16:68 and pretreated at room temperature for 1.5 h. Then, the temperature was increased to 150℃ at a heating rate of 15℃ / h and held for 3 h to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 26.78 MPa, and the tensile strength of the fiber monofilament was 327.23 MPa.

[0032] Example 5

[0033] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=8, R group is -NHCOCH3) was placed in a spinning tank, and 2% by mass of nylon 66 was added. The mixture was stirred and heated to 170℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 90 kPa, and a take-up roller speed of 1000 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 18:15:67. The fibers were pretreated and soaked at room temperature for 1 h, and then heated to 180℃ at a heating rate of 15℃ / h and held for 3 h. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the phenolic fibers can reach 340.26 MPa.

[0034] Example 6

[0035] Self-synthesized thermoplastic phenolic resin (n1=5, n2=9, R group is -OCH3) was placed in a spinning tank, and 4% polyoxymethylene was added. The mixture was stirred and heated to 165℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 90 kPa, and a take-up roller speed of 1200 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 15:15:67 and pretreated for 1 hour at room temperature. Then, the temperature was increased to 160℃ at a heating rate of 15℃ / h and held for 2 hours. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 20.76 MPa, and the tensile strength of the fiber monofilament was 322.65 MPa.

[0036] Example 7

[0037] Self-synthesized group-modified thermoplastic phenolic resin (n1=5, n2=9, R group is -OCH3) was placed in a spinning tank, and 2% polyoxymethylene and 2% polyethylene were added by mass. The mixture was stirred and heated to 170℃. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 100KPa, and a take-up roller speed of 1200r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 15:18:67 and pretreated for 2 hours at room temperature. Then, the temperature was increased to 170℃ at a heating rate of 15℃ / h and held for 2 hours. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 25.26MPa, and the tensile strength of the fiber monofilament was 362.65MPa.

[0038] Example 8

[0039] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=5, R group is -OH) was placed in a spinning tank, and 4% polyethylene and 2% nylon 6 by mass were added. The mixture was stirred and heated to 165℃, and melt spun under a nitrogen atmosphere, 120 kPa pressure, and a take-up roller speed of 1200 r / min to obtain phenolic precursor fibers. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 18:15:70 and pretreated by soaking at room temperature for 0.5 h. Then, the temperature was raised to 180℃ at a heating rate of 25℃ / h and held for 5 h. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 21.96 MPa, and the tensile strength of the fiber monofilament was 307.96 MPa.

[0040] Example 9

[0041] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=5, R group is -OH) was placed in a spinning tank, and 4% polyethylene and 2% nylon 6 were added. The mixture was stirred and heated to 165℃, and melt spun under a nitrogen atmosphere, 120 kPa pressure, and a take-up roller speed of 1200 r / min to obtain phenolic precursor fibers. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 5:10:85 and pretreated for 0.5 h at room temperature. Then, the temperature was increased to 180℃ at a heating rate of 25℃ / h and held for 12 h. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 25.88 MPa, and the tensile strength of the fiber monofilament was 310.02 MPa.

[0042] Example 10

[0043] Self-synthesized group-modified thermoplastic phenolic resin (n1=4, n2=5, R group is -OH) was placed in a spinning tank, and 4% polyethylene and 2% nylon 6 by mass were added. The mixture was stirred and heated to 165℃, and melt spun under a nitrogen atmosphere, 120 kPa pressure, and a take-up roller speed of 1200 r / min to obtain phenolic precursor fibers. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 20:30:50 and pretreated at room temperature for 0.5 h. Then, the temperature was increased to 90℃ at a heating rate of 50℃ / h and held for 5 h. After that, the fibers were taken out, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic fiber precursor was 20.24 MPa, and the tensile strength of the fiber monofilament was 288.08 MPa.

[0044] Comparative Example 1

[0045] Conventional phenolic resin was placed in a spinning tank and heated to 120°C. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, 250 kPa pressure, and a take-up roller speed of 2000 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 15:18:67, and heated to 140°C at a heating rate of 15°C / h, and held for 3 hours. The fibers were then removed, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic precursor fibers was 10.66 MPa, and the tensile strength of the single filament fibers was 80.67 MPa.

[0046] Comparative Example 2

[0047] Conventional phenolic resin was placed in a spinning tank, and 4% (w / w) of polyoxymethylene was added. The mixture was stirred and heated to 165°C. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 90 kPa, and a take-up roller speed of 1200 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 15:15:67 and pretreated at room temperature for 1 hour. The temperature was then increased to 160°C at a rate of 15°C / h and held for 5 hours. After that, the fibers were removed, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic precursor fibers was 13.98 MPa, and the tensile strength of the single filament fibers was 120.16 MPa.

[0048] Comparative Example 3

[0049] Conventional phenolic resin was placed in a spinning tank, and 15% (w / w) of nylon 66 was added. The mixture was stirred and heated to 170°C. Phenolic precursor fibers were obtained by melt spinning under a nitrogen atmosphere, a pressure of 90 kPa, and a take-up roller speed of 1000 r / min. The obtained phenolic precursor fibers were placed in a crosslinking curing solution with a mass ratio of hydrochloric acid: hexamethylenetetramine: deionized water of 18:15:67 and pretreated by soaking at room temperature for 1 hour. The temperature was then increased to 180°C at a rate of 15°C / h and held for 3 hours. The fibers were then removed, washed, and dried to obtain phenolic fibers with a crosslinked structure. The tensile strength of the prepared phenolic precursor fibers was 11.58 MPa, and the tensile strength of the single filament fibers was 88.33 MPa.

[0050] The performance test results of the products prepared by the above embodiments and comparative examples show that the tensile strength and single filament tensile strength of the phenolic fiber precursor prepared by the technical solution of the present invention in the embodiments are significantly better than those in the comparative examples.

[0051] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. A method for preparing high-strength phenolic fibers using group-modified phenolic resin, characterized in that, Includes the following steps: 1) Preparation steps of phenolic fiber precursor: Modified phenolic resin and linear polymer are placed in a spinning tank and heated to melt. Pressure is applied under an inert atmosphere to expel the melt through a spinneret to form phenolic fiber precursors. The phenolic fiber precursors are then taken in on a take-up roller. The molecular structure of the modified phenolic resin is as follows: Where n1≥1, n2≥1, n1+n2=8~15, and the R group is one of -OH, -OCH3, -NHCOCH3, and -B(OH)2; The linear polymer is one or more of polyamide, polyethylene, polypropylene, polyoxymethylene, and polycarbonate; 2) Phenolic fiber precursor curing step: The obtained phenolic fiber precursor is immersed in cross-linking curing solution, and after heating, cross-linking curing, washing and drying, high-strength phenolic fiber is obtained.

2. The method as described in claim 1, characterized in that, The linear polymer mentioned in step 1) accounts for 0.1% to 10% by mass.

3. The method as described in claim 1, characterized in that, The heating and melting temperature described in step 1) is 120~170℃, and the process is carried out under an inert atmosphere.

4. The method as described in claim 1, characterized in that, The inert atmosphere mentioned in step 1) is a nitrogen atmosphere, the pressure is 50-250 kPa, and the rotation speed of the take-up roller is 600-2000 r / min.

5. The method as described in claim 1, characterized in that, The cross-linking curing solution mentioned in step 2) is a mixed solution of hydrochloric acid, hexamethylenetetramine and deionized water.

6. The method as described in claim 5, characterized in that, In step 2), the mass fraction of hydrochloric acid in the crosslinking curing solution is 5%~20%, and the mass fraction of hexamethylenetetramine is 10%~30%.

7. The method as described in claim 1, characterized in that, The soaking conditions in step 2) are: room temperature soaking pretreatment for 0~2h, and the heating conditions are: heating rate of 10~50℃ / h, holding temperature of 90~180℃, and holding time of 2h~12h.

8. The method as described in claim 1, characterized in that, In step 2), the washing process involves repeatedly rinsing the fibers with deionized water until the pH of the washing solution is close to 7; the drying process involves drying the fibers in a forced-air oven at a temperature below 65°C.

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