JP7368929B2 - Manufacturing method of fiber reinforced resin intermediate material - Google Patents

Description

The present invention is a fiber-reinforced resin obtained by attaching a resin powder containing volatile components to a reinforcing fiber base material, and then fusing the resin powder to the reinforcing fiber base material after passing through a step of removing the volatile components in the resin. The present invention relates to a manufacturing method for manufacturing an intermediate material.

Fiber-reinforced resins, which are composites made by impregnating resin into reinforcing fiber base materials made of reinforcing fibers such as carbon fibers, glass fibers, and natural fibers, are widely used in various fields and applications, and are used in aircraft parts, automobile parts, etc. Its application is also progressing to mechanically strong parts. In such mechanically strong parts, in order to exhibit the desired strength and characteristics, resin is impregnated into the reinforcing fiber base material at a predetermined fiber volume content, and the reinforcing fibers and resin are combined in the part. A product with fewer defects such as missing parts and voids where the two do not touch is required. Various methods for welding and impregnating resin powder onto reinforcing fiber base materials have been proposed as methods for molding fiber-reinforced resin molded products with fewer defects such as voids.

For example, in Patent Document 1, a resin is attached to the outer surface of a reinforcing fiber base material formed of spread reinforcing fibers, and the reinforcing fiber base material is impregnated with the resin by heating to a temperature higher than the melting point of the resin. A fiber-reinforced resin intermediate material has been proposed in which the reinforcing fiber base material has voids open to the outer surface and is semi-impregnated with the resin. In this fiber-reinforced resin intermediate material, the fiber-reinforced resin intermediate material made of a reinforcing fiber base material in a semi-impregnated state is produced by electrostatically depositing resin powder on the reinforcing fiber base material and heating it to impregnate it. It is considered good. In addition, during the heating operation, the resin powder adhering to the reinforcing fiber base material melts on the surface of the reinforcing fiber base material, but it maintains a distribution according to the microscopic adhesion status, so the entire surface of the reinforcing fiber base material is melted. It is said that no film-like molten layer covering the surface is formed. For this reason, fiber-reinforced resin intermediate materials have both shapeability and impregnability, so by laminating them, heating and pressurizing them, they can have a desired fiber volume content even if they have a complex shape. It is possible to form fiber-reinforced resin molded articles with sufficient impregnation and fewer defects such as voids.

Patent Document 2 describes a process of opening a reinforcing fiber bundle made of continuous monofilaments in a gas fluidization tank, and passing the opened reinforcing fibers under tension through a container filled with resin powder. A method for producing a fiber composite sheet has been proposed, which includes a step of attaching resin powder to reinforcing fibers, and a step of guiding the reinforcing fibers to which the resin powder has been attached to a heating device to form a sheet. In this method of manufacturing a fiber composite sheet, the reinforcing fibers opened in the opening process are passed under tension through a container filled with resin powder, so that the reinforcing fibers are coated with resin powder in the width direction. can be applied to a uniform thickness. Then, the reinforcing fibers to which the resin powder has adhered are guided to a heating device and formed into a sheet, so that a fiber composite sheet with uniform thickness in the width direction and excellent appearance and strength can be obtained. As this heating device, general heating means such as heating rolls, hot air, and far infrared rays can be used, and the heating temperature can be selected as appropriate depending on the type of resin powder, heating time, purpose of the fiber composite sheet, etc. .

Patent Document 3 describes a step of heating a sheet-like base material made of fibrous material to 50 to 300°C, then a step of attaching resin powder to one side of the sheet-like base material, and a step of attaching the resin powder to one side of the sheet-like base material. A step of heating the opposite side to a higher temperature than the surface on which the powder is present, then a step of making the resin powder exist in order to adjust the amount of resin in the sheet-like base material to which the resin powder has adhered, and then a step of making the sheet-like base material present with the resin powder. A prepreg manufacturing method has been proposed that includes a step of heating the material. According to this prepreg manufacturing method, it is possible to impregnate the sheet-like base material with the powder resin uniformly and well, so it is possible to obtain a prepreg with extremely few air bubbles in the base material and a void-free laminate. It is said that it can be done.

Japanese Patent Application Publication No. 2016-78360 Japanese Patent Application Publication No. 06-287318 Japanese Patent Application Publication No. 11-240967

As described in Patent Document 1, in order to mold a fiber-reinforced resin molded product with few defects such as voids, it is important to mold a fiber-reinforced resin intermediate material that is rich in shapeability and impregnability. In addition, as described in the molding of a fiber composite sheet described in Patent Document 2 or the prepreg molding described in Patent Document 3, resin powder is applied to a sheet-like base material made of spread reinforcing fibers or fibrous materials. It is important to apply it evenly. However, when a fiber-reinforced resin molded product is molded from a fiber-reinforced resin intermediate material or sheet-like base material to which resin powder is evenly adhered, the fiber-reinforced resin molded product has problems with mechanical strength and homogeneity. In some cases, countermeasures are required.

In view of these conventional problems, the present invention provides a fiber-reinforced resin intermediate material that can produce fiber-reinforced resin molded products that are resistant to defects such as voids, have excellent mechanical strength, and have uniform properties. The purpose is to provide a manufacturing method.

The present inventors have discovered that, depending on the manufacturing method or manufacturing process, the resin powder used for manufacturing fiber-reinforced resin molded products may contain 0.1% or more by weight of volatile components derived from raw materials. The present invention was developed based on the knowledge that the volatile components gasify during the molding process of fiber-reinforced resin molded products and remain as voids inside the molded product, which adversely affects the strength and homogeneity of the fiber-reinforced resin molded products. completed.

The method for producing a fiber-reinforced resin intermediate material according to the present invention includes attaching a resin powder containing a volatile component to a reinforcing fiber base material formed of reinforcing fibers, and heating the resin powder to transfer the resin powder to the reinforcing fibers. A method for producing a fiber-reinforced resin intermediate material which is fused to a base material, the method comprising: first heating a reinforcing fiber base material to which the resin powder has been adhered at a predetermined temperature at which the resin powder exhibits weight loss; , heating the resin powder until it reaches a saturated weight reduction rate, and then heating the reinforcing fiber base material to which the resin powder is attached at a predetermined temperature higher than the melting point of the resin powder. A method for producing a fiber-reinforced resin intermediate material, which comprises fusing the above-mentioned reinforcing fiber base material to the above-mentioned reinforcing fiber base material. Here, the fiber-reinforced resin intermediate material is heated and pressurized to form a fiber-reinforced resin molded product, and the saturated weight reduction rate refers to While heating at a constant temperature below the highest temperature in the temperature range selected when shaping the fiber-reinforced resin molded product, the weight loss rate with respect to the heating time is measured, and the weight loss rate is almost constant. When a weight loss rate is expressed as follows, it refers to the weight loss rate.

Further, in the method for producing a fiber-reinforced resin intermediate material according to the present invention, resin powder containing a volatile component is attached to a reinforcing fiber base material formed of reinforcing fibers, and the resin powder is heated to A method for producing a fiber-reinforced resin intermediate material which is fused to a reinforcing fiber base material, in which the saturated weight reduction rate of the resin powder is first determined, and the heating temperature and time that indicate the saturated weight reduction rate are determined. The volatile components contained in the resin powder are evaporated first, and then the reinforcing fiber base material to which the resin powder is attached is heated to a predetermined temperature higher than the melting point of the resin powder to remove the resin. A method for producing a fiber-reinforced resin intermediate material by fusing powder to the reinforcing fiber base material. Here, the fiber-reinforced resin intermediate material is heated and pressurized to form a fiber-reinforced resin molded product, and the saturated weight reduction rate refers to While heating at a constant temperature below the highest temperature in the temperature range selected when shaping the fiber-reinforced resin molded product, the weight loss rate with respect to the heating time is measured, and the weight loss rate is almost constant. When a weight loss rate is expressed as follows, it refers to the weight loss rate.

In the above invention, it is preferable that the content of the volatile components after the volatile component evaporation treatment is 1,000 ppm or less in terms of weight ratio.

In the production of fiber-reinforced resin intermediate materials, the present invention first performs a step of removing volatile components from a reinforcing fiber base material to which resin powder containing volatile components has adhered, and then fuses the resin powder to the reinforcing fiber base material. A fiber-reinforced resin intermediate material is produced. Therefore, when manufacturing fiber-reinforced resin molded products using such a fiber-reinforced resin intermediate material, it is possible to eliminate adverse effects such as the generation of voids caused by volatile components contained in the resin powder, and improve strength and homogeneity. It is possible to produce fiber-reinforced resin molded products with excellent properties.

It is a graph showing an example of a saturated weight loss rate curve of PPS resin.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated. The present invention provides a fiber-reinforced resin made by attaching a resin powder containing a volatile component to a reinforcing fiber base material formed of reinforcing fibers, and heating the resin powder to fuse the resin powder to the reinforcing fiber base material. This invention relates to a method of manufacturing a finger intermediate material. After first performing a volatile component removal step of removing volatile components contained in the resin powder, the reinforcing fiber base material is heated to a predetermined temperature higher than the melting point of the resin powder to strengthen the resin powder. This invention involves manufacturing a fiber-reinforced resin intermediate material by fusing it to a fiber base material. That is, the present invention is characterized by performing a volatile component removal step. Note that the step of removing volatile components of the adhered resin powder and the step of fusing the resin powder to the reinforcing fiber base material do not necessarily need to be separate steps. Depending on the temperature selected, removal of volatile components and fusing to the reinforcing fiber base material may be performed in one step.

In the present invention, the volatile component removal step refers to determining the saturated weight reduction rate of the resin powder attached to the reinforcing fiber base material, and based on the saturated weight reduction rate, the content of the volatile components in the resin powder attached to the reinforcing fiber base material. This is the process of removing volatile components. That is, it is first necessary to determine the saturated weight loss rate of the resin powder to be used. The saturated weight loss rate refers to the rate at which a reinforcing fiber base material to which resin powder is attached is heated at a constant temperature below the highest temperature in the temperature range selected when forming a fiber-reinforced resin molded product. When the weight loss rate with respect to heating time is measured and the weight loss rate is approximately constant, it is referred to as the weight loss rate. Furthermore, fiber-reinforced resin molded products are
A product made by heating and pressurizing a fiber-reinforced resin intermediate material to shape it. Furthermore, the resin powder for which the saturated weight loss rate is to be determined is one that has been previously dried using a drying method suitable for the resin. The temperature at which a fiber-reinforced resin molded product is formed is the temperature at which the fiber-reinforced resin intermediate material produced according to the present invention is heated and pressurized after production to be shaped into a predetermined fiber-reinforced resin molded product. Yes, and refers to the temperature at the time of shaping.

FIG. 1 shows a graph in which the resin powder to be adhered to the reinforcing fiber base material was heated at a predetermined temperature and the weight loss rate was determined with respect to the heating time. The resin powder consists of PP S resin (melting point 280°C) with an average particle size of 40 μm. In FIG. 1, the horizontal axis represents heating time and the vertical axis represents weight loss rate. According to FIG. 1, at a temperature of 280 to 300°C, the weight loss rate curve becomes almost parallel to the horizontal axis, indicating that a saturated state is reached where the weight loss rate is almost constant regardless of the heating time. On the other hand, when the heating temperature was 350°C and 400°C, the weight loss rate increased linearly, and the slope of the weight loss rate curve at 400°C was greater than the slope at 350°C. When the weight loss rate shows a linear increase, it is understood that the resin component of the resin powder itself is decomposed and volatilized.

In Figure 1, when comparing the weight loss rate curve at a heating temperature of 300 °C (curve a) and the weight loss rate curve at a heating temperature of 280 °C (curve b), the slope of curve a is greater than the slope of curve b, and it reaches saturation at about 350 seconds. state, and the saturated weight reduction rate is approximately 0.16%. On the other hand, the b curve reaches a saturated state in about 500 seconds, and the saturated weight loss rate is about 0.18%. In the temperature range where the weight loss rate is saturated and shows the saturated weight loss rate, the higher the heating temperature, the faster the saturated state is reached. Under these heating conditions, dichlorobenzene, γ-butyrolactone, xylene, etc. were detected, and it is understood that volatile components derived from the raw materials of the resin powder were volatilized. The boiling points of the above components are 174°C for dichlorobenzene, 204°C for γ-butyrolactone, and 139°C for xylene.

When a predetermined fiber-reinforced resin molded product is formed using a fiber-reinforced resin intermediate material made of PPS resin, it is generally formed at a forming temperature of 300 to 340°C. Therefore, in the case of a reinforcing fiber base material to which resin powder made of PPS resin is attached, the present invention first performs a volatile component removal step at a temperature of 280 to 300°C for 350 to 500 seconds, and then The resin powder is fused to the reinforcing fiber base material at a predetermined temperature equal to or higher than the melting point of the resin powder to produce a fiber-reinforced resin intermediate material. The fiber-reinforced resin intermediate material thus produced is preferably shaped into a predetermined fiber-reinforced resin molded product at 300 to 340°C. According to such a fiber-reinforced resin intermediate material, it is possible to eliminate the generation of voids and the deterioration of strength or homogeneity due to gases generated from volatile components contained during shaping of a fiber-reinforced resin molded product.

Considering the productivity of the fiber-reinforced resin intermediate material, it is preferable that the time for the volatile component removal step be short. Comparing the above curves a and b from this point of view, it is preferable to perform the volatile component removal step based on curve a. However, the volatile component removal step can also be carried out at, for example, 350° C. (c line). In this case, the volatile component removal step is performed by selecting an appropriate treatment time based on the saturated weight reduction rate of 0.17%. In other words, considering that the shape of the weight loss rate curve differs depending on the matrix resin used, the saturated weight loss will occur in a temperature range below the highest temperature selected when shaping a fiber-reinforced resin molded product. Based on this, a volatile component removal step can be performed to remove volatile components originating from the powder resin. This volatile component removal process is performed with the powder resin attached to the reinforcing fiber base material (with microscopic gaps between the resin powders), so the volatile components originating from the powder resin are efficiently removed. Can be removed. The content of volatile components after the volatile components are evaporated in the volatile component removal step is preferably 1,000 ppm or less in terms of weight ratio.

In the present invention, it is preferable to use an electrostatic adhesion method for adhering the resin powder to the reinforcing fiber base material. Resin powder having an average particle diameter of 1 to 500 μm can be used. Electrostatic adhesion of the resin powder is performed by spraying the resin powder in a charged state onto the reinforcing fiber base material so that the resin powder adheres to the outer surface of the reinforcing fiber base material. This electrostatic adhesion is preferably carried out in a dry state without using a solvent, but even if a solvent is included, it can be used as long as the resin is pulverized within the above average particle diameter range. When observed macroscopically, such resin powder adheres to the surface of the reinforcing fiber base material with a uniform thickness and uniform distribution. When observed microscopically, the surface of the reinforcing fiber base material formed from a large number of bundled reinforcing fibers has parts to which resin powder has adhered in one layer or multiple layers, or to which resin powder has adhered. There are parts that I haven't done. Therefore, the voids existing inside the reinforcing fibers are open to the outer surface of the reinforcing fiber base material, and the reinforcing fibers have voids that are open to the outer surface. A fiber-reinforced resin intermediate material is obtained by heating a reinforcing fiber base material to which the resin powder has adhered in such a state to a temperature higher than the melting point of the resin powder and fusing the resin powder to the reinforcing fiber base material. It is possible to sufficiently exhaust the air and gas remaining inside the molded product even when molded using the resin, and it is possible to mold a fiber-reinforced resin molded product that has excellent shapeability and handling properties, and is less likely to have defects such as voids. . In addition, this state is based on the outer diameter of the reinforcing fibers forming the reinforcing fiber base material and the bulk density of the reinforcing fiber base material, so that the fiber volume content of the reinforcing fiber base material becomes a predetermined value. can be produced by electrostatically depositing a resin powder having an average particle size of . Moreover, the outer surface of the reinforcing fiber base material refers to the open surface of the reinforcing fiber base material.

The resin powder targeted in the present invention contains volatile components derived from its raw materials and/or from the resin manufacturing method or manufacturing process. The resin is not limited to thermoplastic resins. For example, a thermosetting resin that exhibits thermoplastic resin-like behavior when the portion that undergoes a curing reaction is 10% or less can also be targeted by the present invention. Thermoplastic resins include polycarbonate (PC), polysulfone (PSU), polyethersulfone (PES), polyamideimide (PAI), polyetherimide (PEI), polyamide resins (PA6, PA11, PA66), polybutylene terephthalate ( PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyetherketoneketone (PEKK), etc. can be used. As the thermosetting resin, phenol resin, polyimide resin, etc. can be used.

The reinforcing fibers forming the reinforcing fiber base material are preferably carbon fibers, and glass fibers, natural fibers, aramid fibers, boron fibers, polyethylene fibers, and reinforced polypropylene fibers can be used. The reinforcing fiber base material may be made of filamentous or woven reinforcing fibers using reinforcing fibers, or discontinuous reinforcing fibers randomly oriented in two or three dimensions. I can do it. For example, a UD sheet can be used as the fibrous reinforcing fiber base material. The fiber-reinforced resin intermediate material may be a single layer or a laminated material.

<Example 1>
Immediately after polymerization, the unpelletized PPS resin was pulverized and processed into a fine powder with an average particle size of approximately 40 μm. This resin powder was attached to a plain-woven PAN-based carbon fiber base material (fabric weight 198 g/m ² ) so that Vf (volume fiber content) was 50%. The carbon fiber base material to which the resin powder was attached was placed in an oven heated to 300°C, held for 350 seconds, and then taken out. As a result, the volatile components of the attached resin powder were removed and the resin powder was fused to the reinforcing fiber base material to obtain a fiber reinforced resin intermediate base material. Sixteen sheets of this fiber-reinforced resin intermediate base material were laminated and heated and pressurized at a heating temperature of 320° C. and a pressure of 3 MPa to produce a plate-shaped fiber-reinforced resin molded product. The bending strength was measured in accordance with ASTM D790 and was found to be 883 MPa. When the cross section of the test piece was observed, there were no defects such as voids. Cross-sectional observation was performed using an optical microscope.

<Comparative example 1>
Immediately after polymerization, the unpelletized PPS resin was pulverized and processed into a fine powder with an average particle size of approximately 40 μm. This resin powder was attached to a plain-woven PAN-based carbon fiber base material (fabric weight 198 g/m ² ) so that Vf (volume fiber content) was 50%. The carbon fiber base material to which the resin powder was attached was placed in an oven heated to 300°C, held for 30 seconds, and then taken out. As a result, a fiber-reinforced resin intermediate base material in which the resin powder was fused to a reinforcing fiber base material was obtained, although the weight change rate predicted from Figure 1 was small and removal of volatile components from the resin powder was insufficient. Ta. Sixteen sheets of this fiber-reinforced resin intermediate base material were laminated and heated and pressurized at a heating temperature of 320° C. and a pressure of 3 MPa to produce a plate-shaped fiber-reinforced resin molded product. The bending strength was measured in accordance with ASTM D790 and was found to be 743 MPa. When the cross section of the test piece was observed, multiple voids with diameters of several tens of μm were observed inside.

Claims (3)

A fiber-reinforced resin intermediate material is obtained by attaching a resin powder containing a volatile component to a reinforcing fiber base material formed of reinforcing fibers, and heating the resin powder to fuse the resin powder to the reinforcing fiber base material. A method of manufacturing,
First, a reinforcing fiber base material to which the resin powder is attached is heated at a predetermined temperature at which the resin powder shows weight loss until a saturated weight loss rate of the resin powder is reached,
Next, the reinforcing fiber base material to which the resin powder is attached is heated at a predetermined temperature higher than the melting point of the resin powder within a time period until the saturated weight reduction rate is reached. A method for producing a fiber-reinforced resin intermediate material which is fused to a reinforcing fiber base material.
Here, the fiber-reinforced resin intermediate material is heated and pressurized to form a fiber-reinforced resin molded product, and the saturated weight reduction rate refers to While heating at a constant temperature below the highest temperature in the temperature range selected when shaping the fiber-reinforced resin molded product, the weight loss rate with respect to the heating time is measured, and the weight loss rate is almost constant. When a weight loss rate is expressed as follows, it refers to the weight loss rate. The volatile component refers to a component that volatilizes when the resin powder is heated until it reaches a saturated weight reduction rate. A fiber-reinforced resin intermediate material is obtained by attaching a resin powder containing a volatile component to a reinforcing fiber base material formed of reinforcing fibers, and heating the resin powder to fuse the resin powder to the reinforcing fiber base material. A method of manufacturing,
First, the saturated weight reduction rate of the resin powder is determined, and the volatile components contained in the resin powder are volatilized based on the heating temperature and time that indicate the saturated weight reduction rate.
Next, the reinforcing fiber base material to which the resin powder is attached is heated to a predetermined temperature higher than the melting point of the resin powder within the time required to reach the saturation weight reduction rate of the resin powder. A method for producing a fiber-reinforced resin intermediate material by fusing powder to the reinforcing fiber base material. 3. The manufacturing method according to claim 1, wherein the amount of volatile components contained in the resin after the volatile component volatilization treatment is 1,000 ppm or less in terms of weight ratio.

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