A method for preparing thermosetting resin-based high modulus carbon fiber hot-melt prepreg

Abstract

The present invention discloses a method for preparing a thermosetting resin-based high-modulus carbon fiber hot-melt prepreg, which belongs to the technical field of high-performance fiber composite materials and comprises the following steps: (1) preparing a film; (2) threading and spreading high-modulus carbon fiber yarns; (3) hot pressing composite impregnation: during the hot pressing impregnation process, the number of flat rollers is ≥3, and the gap between the upper and lower rollers in each group of flat rollers gradually decreases along the hot pressing impregnation direction, with the minimum roller gap S min According to the formula #imgabs0#, where ρ F is the surface density of high modulus carbon fiber, R is the target percentage of resin matrix in prepreg product, m P is the mass per unit area of ​​release paper, S min The unit is mm. The method of the present invention mainly improves the preparation process of high-modulus hot-melt prepreg by establishing a method for setting the gap between the flat rollers and the temperature during the impregnation process. This method can save debugging time and raw materials, is easy to operate, and the prepared prepreg product has excellent apparent quality and mechanical properties.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance fiber composite materials, and in particular to a method for preparing a thermosetting resin-based high-modulus carbon fiber hot-melt prepreg. Background Art

[0002] Prepreg generally refers to a pre-impregnated sheet product made by impregnating a matrix with reinforcing fibers. It is a semi-finished material with advantages such as high strength, low density, good plasticity, easy processing, corrosion resistance, and long life. The hot melt method is commonly used to produce prepregs in the existing technology. This method first melts the resin at high temperature and then impregnates the reinforcing fibers through various methods to form the prepreg. The advantages of the hot melt method include high-precision control of the resin content, low environmental and human hazards, and low void content in the resulting composite material.

[0003] With the increasing application of resin-reinforced advanced composite materials in fields such as aerospace, more stringent requirements are being placed on the development and performance improvement of high-modulus carbon fiber composite materials. In the existing technology, the preparation process of high-modulus carbon fiber hot-melt prepreg is immature, the impregnation and debugging process easily wastes fiber and resin raw materials, and the quality of high-modulus carbon fiber prepreg is difficult to control during the impregnation and compounding process. Therefore, it is necessary to improve the preparation process of high-modulus carbon fiber hot-melt prepreg.

[0004] Chinese patent document CN102922855A discloses a method for preparing high-toughness hot-melt prepreg using a hot-melt resin matrix. The invention adds an appropriate amount of small-particle toughening powder in a specific manner during the prepreg preparation process. The powder particle size is 100 to 2000 mesh. This not only maintains the drapability of the prepreg, but also basically does not change the curing process parameters of the prepreg.

[0005] Chinese patent document CN107286585A discloses an epoxy hot melt adhesive for high modulus carbon fiber prepreg. The invention compensates for the insufficient toughness of existing epoxy hot melt adhesives by improving the components of the matrix resin. The epoxy hot melt adhesive includes the following components in proportions by weight: 35-55 parts of bisphenol F epoxy resin; 20-30 parts of medium molecular weight epoxy resin; 10-15 parts of modified epoxy resin; 3-5 parts of PVF resin; 2-4 parts of toughening agent; 0.3-2 parts of graphene; 7-10 parts of micro-powdered dicyandiamide; 1-4 parts of accelerator; and 0.1-0.5 parts of surfactant.

[0006] Chinese patent document CN111978727A discloses a high-strength and high-modulus hot-melt bismaleimide resin composition and prepreg. The composition comprises a bismaleimide resin monomer, a process modifier, an aromatic amine curing agent, inorganic nanoparticles and a thermoplastic resin. The resin matrix improves the modulus of the resin matrix through intermolecular forces and molecular stacking density angles. At the same time, a high-modulus thermoplastic resin is used as a rheology control component to meet the requirements of the hot-melt process while minimizing the loss of the resin matrix modulus. The resulting resin matrix has a higher compatibility with the high-strength carbon fiber.

[0007] However, the above methods all require the introduction of new substances to enhance the mechanical properties of the hot-melt prepreg, and do not involve process improvements. Summary of the Invention

[0008] In order to solve the problem that high modulus hot-melt prepreg products are prone to surface defects such as gaps, the present invention provides a method for preparing thermosetting resin-based high modulus carbon fiber hot-melt prepreg, and in particular establishes a method for setting the gap between the flat pressing rollers and the temperature during the impregnation process. This method improves the preparation process of high modulus hot-melt prepreg, can save debugging time and raw materials, is easy to operate, and the prepared prepreg product has excellent apparent quality and mechanical properties and good quality stability.

[0009] The specific technical solutions adopted are as follows:

[0010] The present invention provides a method for preparing a thermosetting resin-based high-modulus carbon fiber hot-melt prepreg, comprising the following steps:

[0011] (1) Film preparation: The resin matrix is ​​made into upper and lower films by using a coating process. The surface density of the film is 10 to 200 g / m 2 ;

[0012] (2) High modulus carbon fiber threading and yarn spreading: The high modulus carbon fiber is fully spread and flattened through threading and yarn spreading to obtain a high modulus carbon fiber layer;

[0013] (3) Hot-pressing composite impregnation: The upper and lower adhesive films with release paper are respectively attached to the two sides of the high modulus carbon fiber layer to form a stacked structure of release paper, upper adhesive film, high modulus carbon fiber layer, lower adhesive film and release paper, and then subjected to hot-pressing impregnation by multiple sets of flat rollers, cooled, and the release paper is peeled off to prepare the thermosetting resin-based high modulus carbon fiber hot-melt prepreg; the surface density of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg is 125 to 600 g / m 2 ;

[0014] During the hot pressing and impregnation process, the number of flat rollers is ≥3, and each flat roller group includes an upper roller and a lower roller. The gap between the upper and lower rollers in each flat roller group gradually decreases along the hot pressing and impregnation direction, and the minimum roller gap S minSet according to the following formula, the unit is mm;

[0015]

[0016] Where, ρ F Is the surface density of high modulus carbon fiber, in g / m 2 Only numerical values ​​are taken, R is the target percentage of the resin matrix in the prepreg product, and the unit is 1, only numerical values ​​are taken, m P The unit area mass of release paper, in g / m 2 The meter only takes the numerical value, S min The unit is mm.

[0017] In the prior art, the gap setting method is mainly based on the theoretical thickness of a single layer after the prepreg is cured and the thickness of the release paper. However, this method has poor practicality and can easily lead to poor gap control, resulting in gaps, bubbles, and even wrinkles. The debugging time is long and the raw materials are greatly wasted. High-modulus carbon fiber is expensive and is not suitable for the existing method. The method of the present invention proposes a relationship between gap setting and multiple physical and chemical performance parameters of the prepreg raw materials. It has strong practicality, saves time and cost, is suitable for expensive high-modulus carbon fiber prepregs, and the prepared prepreg products have excellent apparent quality and mechanical properties.

[0018] Preferably, the number of the flat pressing rollers is 3, and along the hot pressing and impregnation direction, the gaps between the upper and lower pressing rollers in the 3 groups of flat pressing rollers are S1, S2 and S3 respectively; wherein,

[0019] S2+0.01≤S1≤S2+0.02;

[0020] S3+0.01≤S2≤S3+0.02;

[0021] S3=S min .

[0022] Preferably, the number of the flat pressing rollers is 5, and along the hot pressing and impregnation direction, the gaps between the upper and lower pressing rollers in the 5 groups of flat pressing rollers are S1, S2, S3, S4 and S5 respectively; wherein,

[0023] S1=S2+0.02mm,

[0024] S2=S3+0.02mm;

[0025] S4+0.01≤S3≤S4+0.02;

[0026] S5+0.01≤S4≤S5+0.02;

[0027] S5=S min .

[0028] The resin matrix includes at least one of epoxy resin, cyanate resin, phenolic resin, benzoxazine resin and bismaleimide resin.

[0029] The high modulus carbon fiber is a carbon fiber with a modulus higher than 350 GPa, including M40J carbon fiber, M40X carbon fiber, M46J carbon fiber, M50J carbon fiber, M55J carbon fiber, M60J carbon fiber or asphalt-based carbon fiber.

[0030] Preferably, in step (1), the coating parameters are: coating temperature 50-180° C., coating speed 5-15 m / min.

[0031] Preferably, in step (2), the high modulus carbon fiber threading and spreading process is specifically as follows: in the threading process, the high modulus carbon fiber wire angle is controlled to reduce friction, so that the high modulus carbon fiber does not have hair balls and broken wires; in the spreading process, the high modulus carbon fiber is passed through several groups of spreading combs and spreading roller groups in sequence, and in each group of spreading combs and spreading roller groups, the spreading comb is arranged in the front and the spreading roller group is arranged in the back; in the spreading process, the yarn frame withdrawal tension is controlled to be 0~1N, and the width is limited to 60~300mm.

[0032] In step (3), according to the viscosity-temperature curve of the resin, a suitable flat roller impregnation temperature is selected so that the viscosity of the resin matrix is ​​5000-10000 m·Pas during the hot pressing impregnation process. The resin at this viscosity is in good composite state with the high modulus carbon fiber, is easy to wet the fiber, and is not easy to flow. Along the hot pressing impregnation direction, the temperature of the pressure roller remains unchanged or shows a trend of first increasing and then decreasing (the change range does not exceed 10°C).

[0033] Preferably, the speed of hot press impregnation is 1-7 m / min.

[0034] More preferably, the viscosity of the resin matrix during the hot pressing impregnation process is 7000-8000 m·Pas.

[0035] Furthermore, the preparation method of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg also includes a winding step, and the specific operation is: peeling off the release paper on one side of the prepreg product after cooling in step (3), covering it with a protective film, and winding it on a winder. The winding tension is preferably 12-20 kg.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] The gap setting method in the prior art is usually set according to the overall thickness of the prepreg, without considering the difference in fiber and resin content. The debugging time is too long, thus resulting in high cost of raw material waste. The present invention improves the hot pressing composite impregnation step in the prepreg preparation process, and proposes a method for setting the gap between the flat rollers and a method for setting the temperature during the impregnation process. The synergistic effect of the two parameters can improve the surface defects of the prepreg, save debugging time and raw materials, and be easy to operate. The prepared prepreg product has excellent apparent quality and mechanical properties, uniform apparent density, and good quality stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Schematic diagram of the hot pressing composite impregnation process.

[0039] Figure 2 This is an optical image of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg in Example 1.

[0040] Figure 3 This is an optical picture of the prepreg in Comparative Example 1.

[0041] Figure 4 This is an optical picture of the prepreg in Comparative Example 2.

[0042] In the figure, 1 is a high modulus carbon fiber layer; 40 is an upper adhesive film with a release paper on the upper surface; 41 is a lower adhesive film with a release paper on the lower surface; 50 is a first upper pressing roller; 51 is a first lower pressing roller; 52 is a second upper pressing roller; 53 is a second lower pressing roller; 54 is a third upper pressing roller; 55 is a third lower pressing roller; 56 is a fourth upper pressing roller; 57 is a fourth lower pressing roller; 58 is a fifth upper pressing roller; 59 is a fifth lower pressing roller; 6 is a hot pressing plate. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the examples and accompanying drawings. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0044] The target percentage content R of the resin matrix in the prepreg products of Example 1-2 and Comparative Example 1-2 is 36%, and the target percentage content R of the resin matrix in the prepreg product of Example 3 is 34%.

[0045] Example 1

[0046] (1) Film preparation: Cyanate ester resin was made into upper and lower films by coating process. The coating parameters were: coating temperature 55°C, coating speed 10m / min, and the surface density was 55g / m 2 The upper and lower films have a unit area mass of 120g / m 2 Release papers are respectively attached to one side surface of the upper and lower films;

[0047] (2) High modulus carbon fiber threading and yarn spreading: M55J grade high modulus carbon fiber (surface density 195g / m 2 ) is fully unfolded and flattened through yarn threading and yarn spreading; first, the yarn threading process controls the wire angle of the M55J-grade high modulus carbon fiber to reduce the friction between it and the equipment components, so that it does not have hair balls or broken yarns during the yarn threading process; secondly, the M55J-grade high modulus carbon fiber is passed through several groups of yarn spreading combs and yarn spreading roller groups in sequence. In each group of yarn spreading combs and yarn spreading roller groups, the yarn spreading combs are set in front and the yarn spreading roller group is set in the back; during the yarn spreading process, the yarn withdrawal tension of the creel is controlled to 0N, and the width is limited to 300mm;

[0048] (3) Hot pressing composite impregnation: Figure 1 As shown, the upper and lower adhesive films 40 and 41 with release paper are respectively attached to the two sides of the high modulus carbon fiber layer 1 to form a stacked structure of release paper, upper adhesive film, high modulus carbon fiber layer, lower adhesive film and release paper. Then, the structure is passed through 5 sets of flat rollers for hot pressing and impregnation. Each set of flat rollers includes an upper roller and a lower roller. Along the hot pressing and impregnation direction, the gap between the upper and lower rollers in the 5 sets of rollers gradually decreases, and the smallest roller gap S is 0. min According to the formula, it is set to 0.36mm. Specifically, the gap between the first upper pressing roller 50 and the first lower pressing roller 51 is 0.43mm, the gap between the second upper pressing roller 52 and the second lower pressing roller 53 is 0.41mm, the gap between the third upper pressing roller 54 and the third lower pressing roller 55 is 0.39mm, the gap between the fourth upper pressing roller 56 and the fourth lower pressing roller 57 is 0.38mm, and the gap between the fifth upper pressing roller 58 and the fifth lower pressing roller 59 is 0.36mm. During the hot pressing impregnation process, the resin viscosity is controlled at 6000-7000m·Pas. Along the hot pressing impregnation direction, the temperature of the five groups of pressing rollers is set to 60°C, the temperature of the hot pressing plate 6 is the same as the temperature of the pressing roller group on its left side, and the hot pressing impregnation speed is 1-4m / min. After the hot pressing impregnation is completed, it is further cooled at 10°C.

[0049] (4) Peel off and recycle the release paper on one side of the prepreg product after cooling in step (3), cover it with a protective film, and wind it on a winder with a winding tension of 15 kg.

[0050] The test results show that the optical image of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg prepared in this embodiment is as follows: Figure 2 As shown, the prepreg has good surface quality, no surface defects such as bubbles and gaps, and uniform apparent density with a surface density of 305g / m 2 ; The tensile strength is 2332.7MPa; the tensile modulus is 319.95GPa.

[0051] Comparative Example 1

[0052] The only difference between the preparation method of the prepreg in this comparative example and the preparation method of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg in Example 1 is that along the hot pressing and impregnation direction, the gaps between the upper and lower pressing rollers in the five groups of flat pressing rollers are 0.38 mm, 0.36 mm, 0.34 mm, 0.32 mm, and 0.30 mm, respectively.

[0053] The test results show that the optical image of the prepreg of this comparative example is as follows: Figure 3 As shown, the prepreg has poor apparent quality and has many bubble structures. The tensile strength is 1980.3 MPa and the tensile modulus is 288.56 GPa.

[0054] Comparative Example 2

[0055] The only difference between the preparation method of the prepreg in this comparative example and the preparation method of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg in Example 1 is that along the hot pressing and impregnation direction, the gaps between the upper and lower pressing rollers in the five groups of flat pressing rollers are 0.48 mm, 0.46 mm, 0.44 mm, 0.42 mm, and 0.40 mm, respectively.

[0056] The test results show that the optical image of the prepreg of this comparative example is as follows: Figure 4 As shown, the prepreg has poor apparent quality and has many gaps. The tensile strength is 2158.5 MPa and the tensile modulus is 298.64 GPa.

[0057] Example 2

[0058] The difference between the preparation methods of thermosetting resin-based high modulus carbon fiber hot-melt prepreg in this embodiment and in embodiment 1 is that the surface density of M55J grade high modulus carbon fiber is 145g / m 2 Along the hot pressing and impregnation direction, the gaps between the upper and lower pressing rollers in the five sets of flat pressing rollers are 0.38mm, 0.36mm, 0.34mm, 0.32mm, and 0.30mm respectively.

[0059] The test results show that the thermosetting resin-based high modulus carbon fiber hot-melt prepreg prepared in this embodiment has good appearance quality and an area density of 227g / m 2 ; There are no surface defects such as bubbles and gaps, the apparent density is uniform, the tensile strength is 2300MPa; the tensile modulus is 343GPa.

[0060] Example 3

[0061] The preparation method of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg in this embodiment differs from that in embodiment 1 only in that:

[0062] The resin matrix is ​​epoxy resin, and the surface density of M55J grade high modulus carbon fiber is 100g / m 2 , the wire withdrawal tension is 1N;

[0063] Along the hot pressing and impregnation direction, the gaps between the upper and lower pressing rollers in the five sets of flat pressing rollers are 0.32mm, 0.30mm, 0.28mm, 0.26mm, and 0.24mm respectively; the hot pressing and impregnation temperature is 80°C, the speed is 1-5m / min; and the winding tension is 12Kg.

[0064] The test results show that the thermosetting resin-based high modulus carbon fiber hot-melt prepreg prepared in this embodiment has good surface quality, no surface defects such as bubbles and gaps, and uniform apparent density with an area density of 152g / m 2 ; Tensile strength is 1983MPa; Tensile modulus is 328GPa.

[0065] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg, characterized in that: The following steps are involved: (1) Film preparation: The resin matrix is ​​made into upper and lower films by using a coating process. The surface density of the film is 10~200g / m 2 ; (2) High modulus carbon fiber threading and spreading: The high modulus carbon fiber is fully spread and flattened through threading and spreading to obtain a high modulus carbon fiber layer; (3) Hot-pressing composite impregnation: The upper and lower adhesive films with release paper are respectively attached to the two sides of the high modulus carbon fiber layer to form a stacked structure of release paper, upper adhesive film, high modulus carbon fiber layer, lower adhesive film and release paper. After hot-pressing and impregnation with multiple sets of flat rollers, the mixture is cooled and the release paper is peeled off to prepare the thermosetting resin-based high modulus carbon fiber hot-melt prepreg. The surface density of the thermosetting resin-based high modulus carbon fiber hot-melt prepreg is 125~600 g / m 2 ; During the hot pressing and impregnation process, the number of flat rollers is ≥3, and each flat roller group includes an upper roller and a lower roller. The gap between the upper and lower rollers in each flat roller group gradually decreases along the hot pressing and impregnation direction, and the minimum roller gap S min Press the button to set; ； Where, ρ F Is the surface density of high modulus carbon fiber, in g / m 2 Only numerical values ​​are taken, R is the target percentage of the resin matrix in the prepreg product, and the unit is 1, only numerical values ​​are taken, m P The unit area mass of release paper, in g / m 2 The meter only takes the numerical value, S min The unit is mm.

2. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: There are three groups of flat rollers. Along the hot pressing and impregnation direction, the gaps between the upper and lower rollers in the three groups of flat rollers are S1, S2 and S3 respectively. S2+0.01≤S1≤S2+0.02; S3+0.01≤S2≤S3+0.02; S3=S min 。 3. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: There are 5 groups of flat rollers. Along the hot pressing and impregnation direction, the gaps between the upper and lower rollers in the 5 groups of flat rollers are S1, S2, S3, S4 and S5 respectively; wherein, S1=S2+0.02mm, S2=S3+0.02mm; S4+0.01≤S3≤S4+0.02; S5+0.01≤S4≤S5+0.02; S5=S min 。 4. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: The resin matrix includes at least one of epoxy resin, cyanate resin, phenolic resin, benzoxazine resin and bismaleimide resin.

5. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: The high modulus carbon fiber is a carbon fiber with a modulus higher than 350 GPa, including M40J carbon fiber, M40X carbon fiber, M46J carbon fiber, M50J carbon fiber, M55J carbon fiber, M60J carbon fiber or pitch-based carbon fiber.

6. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: In step (1), the coating parameters are: coating temperature 50~180℃, coating speed 5~15 m / min.

7. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: In step (2), the high modulus carbon fiber threading and spreading process is specifically as follows: in the threading process, the high modulus carbon fiber wire angle is controlled to reduce friction, so that the high modulus carbon fiber does not have hair balls and broken wires; in the spreading process, the high modulus carbon fiber is passed through several groups of spreading combs and spreading roller groups in sequence, and in each group of spreading combs and spreading roller groups, the spreading comb is set in the front and the spreading roller group is set in the back; in the spreading process, the yarn frame withdrawal tension is controlled to be 0~1N, and the width is limited to 60~300 mm.

8. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, wherein: In step (3), the viscosity of the resin matrix during the hot pressing impregnation process is 5000-10000 m•Pas; the speed of the hot pressing impregnation is 1-7 m / min.

9. The method for preparing a thermosetting resin-based high modulus carbon fiber hot-melt prepreg according to claim 1, characterized in that: The method further includes a winding step, wherein the specific operation is: peeling off the release paper on one side of the prepreg product after cooling in step (3), covering it with a protective film, and winding it on a winding machine.

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