JP7387963B2 - Prepreg, prepreg manufacturing method, molded body, and molded body manufacturing method - Google Patents

Description

The present invention relates to a prepreg, a prepreg manufacturing method, a molded article, and a molded article manufacturing method.

Fiber reinforced plastics (FRP) are used as high-strength, lightweight materials in various fields such as aerospace and automobiles. Examples of the fiber-reinforced resin include a base material using reinforcing fibers impregnated with resin, and examples of the base material using reinforcing fibers include nonwoven fabrics, woven fabrics, and knitted fabrics.

Although fiber-reinforced resins have high strength and are lightweight, it is known that they have poor moldability and are difficult to form into complex shapes.
As a method for shaping a composite material using fiber-reinforced resin, for example, Patent Document 1 discloses a method in which a mesh-like knitted structure having a longitudinal knitting structure using carbon fiber strands is shaped and then impregnated with resin. A cured fiber reinforced composite material is disclosed. Further, Patent Document 2 discloses a composite material component in which the knitted fabric layer is strengthened by inserting warp threads into the knitted fabric layer while imparting a profile that follows a desired shape, and is then impregnated with a matrix. As described above, progress is being made in the development of a technique for obtaining a desired shape by first shaping a reinforcing fiber base material and then impregnating it with resin.

Unexamined Japanese Patent Publication No. 2016-17120 JP2017-218688A

However, while fiber-reinforced resin has high strength, it is difficult to obtain elasticity, and a prepreg that is a base material impregnated with resin before being shaped is used to form a shape that includes a recessed part with a top plate part and a vertical wall part. It is difficult to mold it into In particular, when forming into a shape in which the ratio of the depth D to the opening diameter d (D/d) of the recess is large, such as in deep drawing, the base material within the prepreg may break due to the force applied during forming. be. Further, depending on the type of base material, although a molded body can be obtained without breaking, the molded body may have a direction in which it is weak against stress, and the durability of the obtained molded body as a whole is required.
Therefore, the present invention provides a prepreg that is less prone to breakage of the base material during molding and has excellent durability when formed into a molded product, a method for producing the prepreg, a molded product using the prepreg, and a method for producing the prepreg, and a molded product using the prepreg. The objective is to provide a manufacturing method.

The above problem is solved by the following means. That is,

[1] A molding base material knitted by weft knitting using reinforcing fibers,
A resin impregnated into at least a portion of the molding base material and containing at least one selected from the group consisting of a room temperature curable resin, a thermosetting resin, and a thermoplastic resin;
has
The bending strength Bc in the course direction of the molding base material when the molded product obtained by pressing using a heat press machine at 150 °C, 4 kg/cm ² , and 120 minutes is measured at 23 °C, and the molding A prepreg in which the bending strength Bw in the wale direction, the bending elastic modulus Mc in the course direction, and the bending elastic modulus Mw in the wale direction of the base material satisfy the following condition 1 and/or the following condition 2.
Condition 1: The absolute value of the difference between the Bc and the Bw is 30% or less of the average value of the Bc and the Bw. Condition 2: The absolute value of the difference between the Mc and the Mw is 30% or less of the average value of the Bc and the Bw. 30% or less of the average value [2] The molding base material has a first stitch row in which the stitches are diagonal with respect to the wale direction, and a stitch row adjacent to the first stitch row, and in which the stitches are in the wale direction. On the other hand, the prepreg according to [1], which repeatedly has a second stitch row obliquely running on the opposite side of the first stitch row.
[3] The reinforcing fiber is glass fiber, carbon fiber, silicon carbide fiber, metal fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, basalt fiber, polyparaphenylene benzobis oxazole fiber, polyarylate fiber, polyacetal fiber, The prepreg according to [1] or [2], which contains at least one selected from the group consisting of polyvinyl alcohol fibers, fluororesin fibers, cellulose fibers, and nylon fibers.
[4] The weft knitting includes at least one selected from the group consisting of rubber knitting, ridge knitting, pearl knitting, flat knitting, bag knitting, double-sided knitting, Milano rib, and pique knitting [1] to [3] The prepreg according to any one of the above.
[5] The prepreg according to any one of [1] to [4], wherein the reinforcing fiber is a multifilament made of a plurality of single fibers.
[6] The prepreg according to [5], wherein the multifilament is a drawn yarn obtained by aligning a plurality of single fibers and/or a twisted yarn processed by twisting.

[7] A method for producing the prepreg according to any one of [1] to [6], comprising:
A step of manufacturing a forming base material knitted by weft knitting using reinforcing fibers by alternately repeating the following first step and the following second step using a flat knitting machine;
Impregnating at least a portion of the molding base material with a resin material containing at least one selected from the group consisting of a room temperature curable resin, a thermosetting resin, and a thermoplastic resin;
A method for producing a prepreg having the following.
First step: Step of forming a first stitch row in which the stitches are oblique to the wale direction by moving the carriage with the needle bed of the flat knitting machine swung to one side Second step: The above-mentioned By moving the carriage in the opposite direction to the first step with the needle bed swung in the opposite direction to the first step, the stitches are adjacent to the first stitch row and in the wale direction. On the other hand, the step of forming a second stitch row diagonally opposite to the first stitch row [8] The method for manufacturing a prepreg according to [6],
A step of manufacturing a forming base material knitted by weft knitting using reinforcing fibers by alternately repeating the following first step and the following second step using a flat knitting machine;
Impregnating at least a portion of the molding base material with a resin material containing at least one selected from the group consisting of a room temperature curable resin, a thermosetting resin, and a thermoplastic resin;
A method for producing a prepreg having the following.
First step: A step of moving the carriage of the flat knitting machine in one direction to form a first stitch row in which the stitches are oblique to the wale direction.Second step: Moving the carriage of the flat knitting machine to the first step. forming a second stitch row that is adjacent to the first stitch row and in which the stitches run diagonally on the opposite side of the first stitch row with respect to the wale direction by moving in the opposite direction.

[9] A molded article of the prepreg according to any one of [1] to [6],
A molded body including a recessed portion having a top plate portion and a vertical wall portion.
[10] The molded article according to [9], wherein the recess has a ratio (D/d) of depth D to opening diameter d of 0.5 or more.
[11] The molded article according to [9] or [10], wherein the top plate portion is flat.

[12] By molding the prepreg according to any one of [1] to [6] or the prepreg obtained by the prepreg manufacturing method according to [7] or [8], the top plate portion and the vertical A method for producing a molded body, comprising a molding step of shaping it into a shape including a recessed portion having a wall.
[13] The molding step includes a step of shaping by at least one molding method selected from the group consisting of press molding, hand lay-up molding, autoclave molding, RTM molding, pultrusion molding, and sheet winding molding [12] ] The method for producing a molded article.
[14] The method for producing a molded article according to [12], wherein the forming step is a step of performing deep drawing.
[15] The method for producing a molded body according to [14], wherein in the molding step, a punch die having a flat molding surface forming the top plate portion is used.
[16] The prepreg molded article according to any one of [1] to [6].

According to the present invention, there is provided a prepreg whose base material is less prone to breakage during molding and which has excellent durability when formed into a molded object, a method for producing the prepreg, a molded object using the prepreg, and a method for producing the prepreg, and a molded object using the prepreg. A manufacturing method is provided.

FIG. 2 is a schematic diagram partially showing an example of a knitted fabric having diagonal stitches. FIG. 3 is an end view schematically showing an example of a recess in the molded body. It is an X-ray CT image of a molded article obtained by molding prepreg 2 using mold 3 in Example 2. 2 is an X-ray CT image of a molded article obtained by molding using mold 2 in Comparative Example 2.

Embodiments of the present invention will be described below. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the embodiments.

In the numerical ranges described step by step in this specification, the upper limit value or lower limit value described in one numerical range may be replaced with the upper limit value or lower limit value of another numerical range described step by step. good. Further, in the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced with the value shown in the Examples.

In this embodiment, each component may contain multiple types of corresponding substances. In this embodiment, when referring to the amount of each component in the composition, if there are multiple types of substances corresponding to each component in the composition, unless otherwise specified, the multiple types present in the composition means the total amount of substances.

In this specification, the term "process" is used not only to refer to an independent process, but also to include any process that is not clearly distinguishable from other processes as long as the intended purpose of the process is achieved. .

[Prepreg]
The prepreg of this embodiment includes a molding base material knitted by weft knitting using reinforcing fibers, and at least a portion of the molding base material is impregnated with a room temperature curable resin, a thermosetting resin, and a thermosetting resin. a resin containing at least one selected from the group consisting of plastic resins, and pressed using a heat press machine at 150°C, 4 kg/cm ² for 120 minutes, and then pressed at 23°C. The bending strength Bc in the course direction, the bending strength Bw in the wale direction, the bending modulus Mc in the course direction, and the bending modulus Mw in the wale direction of the molding base material when measured under the following condition 1 and/or the following Condition 2 is satisfied.
Condition 1: The absolute value of the difference between Bc and Bw is 30% or less of the average value of Bc and Bw. Condition 2: The absolute value of the difference between Mc and Mw is 30% or less of the average value of Mc and Mw. The prepreg of this embodiment satisfies at least one selected from the group consisting of Condition 1 and Condition 2 above.
Hereinafter, the ratio (%) of the absolute value of the difference between Bc and Bw to the average value of Bc and Bw is also referred to as "strength anisotropy after molding", and the ratio of Mc and Mw to the average value of Mc and Mw is also referred to as "strength anisotropy after molding". The ratio (%) of the absolute value of the difference is also referred to as "elastic modulus anisotropy after molding."

Here, the bending strength and bending elastic modulus of the prepreg after being formed are measured in accordance with JIS K 7017 (1999) as follows.
First, a prepreg to be measured is pressed using a heat press machine (As One Corporation, model number: H300-15) at a temperature of 150° C., a pressure of 4 kg/cm ² , and a time of 120 minutes to obtain a molded body.
Next, the obtained molded body was tested using an Autograph precision universal testing machine (Shimadzu Corporation, model number AG-100kNX) at a temperature of 23°C, a relative humidity of 50%, an air pressure of 86 kPa or more and 106 kPa or less, and a bending speed of 1 mm/min. A three-point bending test is performed under the conditions of , distance between fulcrums: 20 mm, and indenter diameter: 5 mm, and the bending strength and bending elastic modulus in each direction are determined.

The above prepreg uses a molding base material that is a knitted fabric base material of reinforcing fibers knitted by weft knitting, and has a small strength anisotropy after molding and/or an elastic modulus anisotropy after molding. , the base material is less likely to break during molding, and has excellent durability when formed into a molded product. Although the reason is not certain, it is assumed as follows.
As mentioned above, knitted fabric base materials knitted by weft knitting have better stretchability compared to textile base materials and warp knitted base materials such as the fiber reinforced composite material disclosed in Patent Document 1. . Therefore, when forming into a shape that includes a concave portion with a large ratio of depth D to opening diameter d (D/d), such as by deep drawing, for example, when forming a prepreg using a woven or warp-knitted base material, the base material In contrast, in prepregs using knitted fabric base materials knitted by weft knitting, the base materials are less likely to break during molding.
In addition, even if a knitted fabric base material is knitted by weft knitting, if a forming base material that is a conventional general weft knitted fabric is used, the characteristics of the course direction and wale direction of a molded article made of prepreg will change. was found to be significantly different. Molded objects with significantly different properties in the course direction and wale direction are likely to crack in the direction with lower strength between the course direction and the wale direction, resulting in lower durability during use as a whole, so their uses are limited. It is thought that it will come. In particular, when used as a molded body having a flat part and a recessed part, such as an automobile member, it is considered that each of the flat part and the recessed part is required to have durability against stress from all directions.
On the other hand, the prepreg of this embodiment uses a knitted fabric base material of reinforcing fibers knitted by weft knitting as a molding base material, and also has strength anisotropy after molding and/or elastic modulus after molding. Anisotropy is 30% or less. As a result, the base material for molding has high elasticity and the concentration of force applied during molding is suppressed, making it difficult for the base material to break. At the same time, the difference in properties between the course direction and the wale direction is small, so it can be used from any direction. It is assumed that it can withstand stress and has high overall durability during use. By increasing the overall durability, it can be used for automobiles, aircraft, railways, building materials, bridges, and other structures that need to withstand stress from all directions. Expands the uses of molded objects.

In the prepreg of this embodiment, both the strength anisotropy after molding and the elastic modulus anisotropy after molding may be 30% or less, and the strength anisotropy after molding may be 30% or less, and the strength anisotropy after molding may be 30% or less. The elastic modulus anisotropy may exceed 30%, and the strength anisotropy after molding may exceed 30% and the elastic modulus anisotropy after molding may be 30% or less.
The prepreg of this embodiment has both strength anisotropy after molding and elastic modulus anisotropy after molding of 30, from the viewpoint of further suppressing breakage during molding and further improving durability when formed into a molded product. % or less.

The strength anisotropy after molding is preferably 30% or less, and more preferably 20% or less from the viewpoint of further suppressing breakage during molding and further improving durability when formed into a molded product. , more preferably 10% or less.
The bending strength Bc in the course direction of the molded product is preferably 50 MPa to 400 MPa, more preferably 75 MPa to 300 MPa, from the viewpoint of moldability, prevention of breakage during molding, and improvement of durability of the molded product. More preferably, it is 100 MPa to 200 MPa.
The bending strength Bw in the wale direction of the molded product is preferably 50 MPa to 400 MPa, more preferably 75 MPa to 300 MPa, from the viewpoint of moldability, prevention of breakage during molding, and improvement of durability of the molded product. More preferably, it is 100 MPa to 200 MPa.

The elastic modulus anisotropy after molding is preferably 30% or less, and from the viewpoint of further suppressing breakage during molding and further improving the durability of the molded product, it is more preferably 20% or less. It is preferably 10% or less, and more preferably 10% or less.
The bending elastic modulus Mc in the course direction of the molded product is preferably 3 GPa to 30 GPa, more preferably 5 GPa to 30 GPa, from the viewpoint of moldability, prevention of breakage during molding, and improvement of durability of the molded product. , 10 GPa to 30 GPa is more preferable.
The bending elastic modulus Mw in the wale direction of the molded body is preferably 3 GPa to 30 GPa, more preferably 5 GPa to 30 GPa, from the viewpoint of moldability, prevention of breakage during molding, and improvement of durability of the molded body. , 10 GPa to 30 GPa is more preferable.

The method of suppressing the strength anisotropy after molding and/or the elastic modulus anisotropy after molding is not particularly limited. (hereinafter also referred to as "diagonal stitches").
Hereinafter, as an example of the above prepreg, a prepreg using a knitted fabric having diagonal stitches as a molding base material will be described.

(Molding base material)
FIG. 1 is a schematic diagram partially showing an example of a knitted fabric having diagonal stitches. The knitted fabric 100 shown in FIG. The stitch row 112 and a second stitch row 114 diagonally running on the opposite side are repeated.

In a knitted fabric having diagonal stitches, the diagonal angle of the stitches is not particularly limited, and for example, in a natural state (i.e., a state where no external force such as tensile stress is applied in a specific direction), The range is 30 degrees to 60 degrees with respect to the wale direction.
In addition, in FIG. 1, all the stitch rows are configured by repeating the first stitch row 112 and the second stitch row 114, but the present invention is not limited to this. From the viewpoint of keeping the strength anisotropy after molding and/or the elastic modulus anisotropy after molding low, the repetition of the first stitch row and the second stitch row among the stitch rows constituting the base material is important. The ratio is preferably 70% or more, more preferably 85% or more, and even more preferably 95% or more.
In addition, in FIG. 1, in each stitch row, all the stitches in the course direction C are diagonal; however, this is not limited to this, and the proportion of diagonal stitches in all the stitches constituting each stitch row is is preferably 70% or more, more preferably 85% or more, and even more preferably 95% or more.

Examples of methods for controlling the bending strength Bc in the course direction and the bending strength Bw in the wale direction include a method of adjusting the material, shape, fineness, etc. of the reinforcing fibers in the molding base material.
Further, as a method of controlling the bending elastic modulus Mc in the course direction and the bending elastic modulus Mw in the wale direction, for example, a method of adjusting the material, shape, fineness, etc. of the reinforcing fiber in the molding base material can be mentioned.

Types of weft knitting in the molding base material include, for example, rubber knitting, ridge knitting, pearl knitting, flat knitting, bag knitting, double-sided knitting, Milano rib, and pique knitting, among which rubber knitting, ridged knitting, double-sided knitting Knitting is preferred, and rubber knitting is more preferred.
The basis weight of the molding base material is not particularly limited, and examples thereof include 50 g/m ² to 1000 g/m ² , preferably 100 g/m ² to 700 g/m ² , and 100 g/m ² to 500 g/m 2 . ^m2 is more preferred.
The reinforcing fibers used in the molding base material will be explained below.

<Reinforcing fiber>
Examples of the reinforcing fiber material include glass fiber, carbon fiber, silicon carbide fiber, metal fiber, aramid fiber, ultra-high molecular weight polyethylene fiber, basalt fiber, polyparaphenylene benzobis oxazole fiber (i.e., PBO fiber), Examples include polyarylate fibers, polyacetal fibers (eg, high-strength PVA fibers), polyvinyl alcohol fibers, fluororesin fibers, cellulose fibers, and nylon fibers. Among these, the reinforcing fibers are preferably glass fibers, carbon fibers, metal fibers, and aramid fibers, and more preferably glass fibers.

The reinforcing fibers may be monofilaments that are single fibers used as they are, or may be multifilaments that are composed of a plurality of single fibers. Multifilaments include, for example, substantially untwisted aligned yarn made of multiple single fibers aligned, crimped yarn that is crimped, twisted yarn that is twisted, and spun yarn that is spun. Examples include thread. From the viewpoint of suppressing the strength anisotropy after molding and/or the elastic modulus anisotropy after molding, it is preferable to use multifilaments as reinforcing fibers, and among them, it is preferable to use aligned threads and/or twisted threads. More preferably, it is even more preferable to use a drawn thread.
The number of filaments in the multifilament is not particularly limited, and may range from 50 to 1000, preferably from 100 to 800, more preferably from 200 to 800. Further, among the multifilaments, the number of filaments in the drawn yarn is preferably 100 to 500, more preferably 200 to 400.

The single fiber diameter of the fiber used for the reinforcing fiber is, for example, in the range of 0.1 μm to 10 μm, preferably in the range of 0.5 μm to 9 μm, and more preferably in the range of 2 μm to 7 μm. .
The fineness of the reinforcing fibers is, for example, in the range of 1.0 tex to 100 tex, preferably in the range of 10 tex to 70 tex, and more preferably in the range of 20 tex to 70 tex.

<Method for manufacturing base material for molding>
The molding base material is manufactured using, for example, a flat knitting machine. The gauge number of the flat knitting machine is not particularly limited, and examples thereof include 10 gauge to 22 gauge, and preferably 12 gauge to 22 gauge.
Methods for manufacturing a molding base material that is a knitted fabric with diagonal stitches using a flat knitting machine include a method of performing "furi knitting" in which the needle bed is shaken during the process of manufacturing the knitted fabric, and a method of performing "furi knitting" in which the needle bed is shaken in the process of manufacturing the knitted fabric, and a method in which the fabric is aligned as reinforcing fibers. Examples include methods using threads and/or twisted threads, and these methods may be combined. Among these, especially when using crimped yarn and/or spun yarn as the reinforcing fiber, it is preferable to manufacture the molding base material by the above-mentioned swing knitting method.

The method of performing swing knitting includes, for example, a first step of forming a first stitch row in which the stitches are oblique to the wale direction by moving the carriage with the needle bed swinging to one side; By moving the carriage in the opposite direction to the first step with the needle bed swung in the opposite direction to the first step, the needle bed is moved in the opposite direction to the first step so that the stitch row is adjacent to the first stitch row and the stitch is An example of a method is to alternately repeat the steps of forming a second stitch row obliquely on the opposite side of the second stitch row.

Specifically, for example, if the flat knitting machine is a double-row needle bed type, first, the rear needle bed is moved (racked) by one stitch relative to the front needle bed, and then the carriage passes through the machine. A first stitch row in which the stitches are oblique to the wale direction is formed (first step). Subsequently, the rear needle bed is moved (racked) by one stitch in the direction opposite to the first step with respect to the front needle bed, and in this state, the carriage is passed in the direction opposite to the first step. Thereby, a second stitch row is formed which is adjacent to the first stitch row and in which the stitches run diagonally on the opposite side of the first stitch row with respect to the wale direction (second step). By repeating the first step and the second step alternately (that is, moving the rear needle bed by one stitch from side to side alternately each time the carriage reciprocates), the first stitch row and A knitted fabric having the second stitch row repeatedly is formed.
Note that the moving distance of the needle bed is not limited to 1 stitch, and includes, for example, 1/4 pitch to 2 pitches (that is, 1/4 stitch to 2 stitches), and 3/4 pitch to 1 stitch. The pitch (ie between 3/4 stitches and 1 stitch) is preferred.

In the method of using aligned yarns and/or twisted yarns as reinforcing fibers, it is easier to form diagonal stitches by performing swing knitting, and it is easier to adjust the diagonal angle. Row stitches may be formed. Although it is not clear why diagonal stitches are formed by using aligned threads and/or twisted threads, it is presumed that it is due to the slippery surface of the threads.
From the viewpoint of forming diagonal stitches without performing swing knitting, the material of the drawn yarn and twisted yarn is preferably glass fiber, the number of filaments is preferably 200 to 400, and the single fiber diameter is 2 μm. The thickness is preferably 7 μm.

(resin)
Next, the resin will be explained.
In the prepreg, at least a part of the molding base material is impregnated with a resin, and preferably 80% or more of the molding base material is impregnated with the resin, and 95% or more of the molding base material is impregnated with the resin. It is more preferable that the molding base material is impregnated with a resin, and it is even more preferable that the entire molding base material is impregnated with a resin.

The resin that the prepreg has includes at least one selected from the group consisting of room temperature curable resins, thermosetting resins, and thermoplastic resins.
Examples of room temperature curable resins and thermosetting resins include epoxy resins, vinyl ester resins, methyl methacrylate resins (ie, MMA resins), acrylic resins, unsaturated polyester resins, and phenolic resins. Furthermore, examples of the thermoplastic resin include polyetheretherketone resin and polyphenylene sulfide resin.
Among these, the resin preferably contains at least one selected from the group consisting of phenol resin, epoxy resin, and unsaturated polyester resin, and more preferably contains phenol resin and epoxy resin.

The ratio of the resin to the entire prepreg is not particularly limited, and is preferably 30% by mass to 80% by mass, more preferably 40% by mass to 70% by mass, and even more preferably 50% by mass to 60% by mass.

<Prepreg manufacturing method>
Prepreg is manufactured through a process of impregnating at least a portion of a molding base material with a resin material.
The method of impregnating at least a portion of the molding base material with the resin material is not particularly limited, and for example, the method of immersing the molding base material in a pre-cured resin, or applying the uncured resin to the molding base material. methods, methods of laminating a laminate film coated with uncured resin onto a molding base material, methods of immersing a molding base material in a molten resin material, and methods of applying a molten resin material to a molding base material. Among them, methods include immersing the molding base material in uncured resin, applying uncured resin to the molding base material, and laminating a laminate film coated with uncured resin onto the molding base material. is preferred, and a method of immersing the molding base material in a resin before curing is more preferred.

The resin material used in the above step may contain a resin containing at least one selected from the group consisting of room temperature curable resin, thermosetting resin, and thermoplastic resin, and may contain components other than resin. You may do so. In addition, when the resin material contains components other than resin, the resin content in the entire resin material is preferably 80% by mass or more, more preferably 90% by mass or more, and 95% by mass or more. It is even more preferable that there be.

[Molded object]
The molded article of this embodiment is a prepreg molded article mentioned above. The molded body includes a recessed portion having a top plate portion and a side wall portion.
FIG. 2 is an end view schematically showing an example of a recess in the molded body.
The recessed portion 10 shown in FIG. 2 includes a top plate portion 12 and a vertical wall portion 14 adjacent to the periphery of the top plate portion 12. Although the top plate portion 12 of the recess 10 shown in FIG. 2 is a plane parallel to the opening surface 16, the top plate portion 12 is not limited to this, and may be a plane that is not parallel to the opening surface or may be a curved surface. . Moreover, although the end face of the vertical wall part 14 shown in FIG. 2 is a straight line from the opening surface 16 side of the recessed part 10 to the top plate part 12 side, it is not limited to this, and may be a curved line.

The ratio (D/d) of the depth D to the opening diameter d in the recess 10 is preferably 0.5 or more, more preferably 0.5 to 4.0, and 0.5 to 1.2. It is more preferable that
The value of the opening diameter d is not particularly limited, and may be, for example, in the range of 5 mm to 100 mm, preferably in the range of 10 mm to 50 mm, and more preferably in the range of 20 mm to 30 mm. Further, the value of the depth D is not particularly limited, and for example, it is in the range of 5 mm to 100 mm, preferably in the range of 10 mm to 50 mm, and more preferably in the range of 10 mm to 30 mm. .

Here, the opening diameter d represents the equivalent circle diameter of the opening surface 16 of the recess 10. Further, the depth D represents the distance from the opening surface 16 of the recess 10 to the top plate portion 12. If the top plate is not parallel to the opening surface or has a curved surface, the depth D represents the farthest distance from the opening surface 16 to the top plate 12.

When the top plate portion 12 is flat, the equivalent circle diameter dt of the top plate portion 12 is not particularly limited, and may be, for example, in the range of 0.05 to 1 times the opening diameter d, and may be 0.1 to 1 times the opening diameter d. The range is preferably 0.3 times to 1 time, more preferably 0.3 times to 1 time.
The shapes of the opening surface 16 and the top plate portion 12 are not particularly limited, and examples thereof include circular, elliptical, polygonal, and the like.

The molded body may include at least one recess having a top plate portion and a side wall portion, and may include two or more of the recesses. Further, when the molded body includes two or more recesses, the two or more recesses may have the same shape or different shapes.

<Method for manufacturing molded body>
The molded body is manufactured by molding the prepreg described above and shaping it into a shape including a recessed portion having a top plate portion and a vertical wall portion.
Examples of the molding method applied in the above molding process include press molding, hand lay-up molding, autoclave molding, RTM molding, pultrusion molding, sheet winding molding, etc. Among them, press molding and autoclave molding are preferable, and press molding is more preferable. Further, the forming method applied in the above forming step is more preferably a deep drawing process among press forming.

In the step of performing deep drawing, for example, deep drawing is performed using a deep drawing mold. As the deep drawing mold, for example, a mold having a convex punch die, a concave die, and a holder is used. When using the above-mentioned deep drawing mold, for example, the prepreg is held between a punch die and a die and the prepreg is held in place by a holder, and the prepreg is molded.
The convex surface of the punch mold serves as a molding surface for forming the top plate portion and vertical wall portion of the recessed portion to be formed. That is, the punch mold has, for example, a molding surface that forms the top plate portion of the recess and a molding surface that forms the vertical wall portion of the recess. Therefore, for example, when producing a molded body having a concave portion with a flat top plate by deep drawing, the deep drawing mold is a mold having a punch die with a flat molding surface forming the top plate. Use a mold.

The molding conditions for producing the molded body are not particularly limited. The molding temperature may be, for example, 80° C. to 180° C., the molding pressure may be, for example, 0.5 kg/cm ² to 10 kg/cm ² , and the molding time may be, for example, 30 minutes to 180 minutes.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples, but the present invention is not limited to the Examples below. The materials, usage amounts, proportions, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present embodiment. Note that unless otherwise specified, "parts" means "parts by mass."

[Example 1]
<Manufacture of base material for molding>
As the reinforcing fibers, crimped glass fibers (crimped multifilament, single fiber diameter: 6 μm, number of filaments: 800) with a fineness of 70.0 tex were used.
Using a 14-gauge flat knitting machine, rubber knitting was knitted while racking the needle head from side to side, and the stitches were made diagonally from side to side with respect to the wale direction. Specifically, the carriage is moved while the needle bed is swung one stitch in one direction, and then the carriage is moved in the opposite direction while the needle bed is swung one stitch in the opposite direction. Ta.
As a result, the stitches are adjacent to the first stitch row diagonally at 45° with respect to the wale direction, and the stitches are on the opposite side of the first stitch row with respect to the wale direction. A molding base material 1 (fabric weight: 370 g/m ² ), which is a knitted fabric base material repeatedly having a second stitch row obliquely oriented at 45°, was obtained.

<Manufacture of prepreg>
Using epoxy resin (epoxy resin sheet for prepreg production manufactured by Sanyurec Co., Ltd. Product name: DRS-028-100) as a resin material, by impregnating the entire molding base material 1 as follows, the ratio of resin to the entire prepreg Prepreg 1 having 50% by mass was obtained.
Specifically, prepreg 1 was obtained by pasting an epoxy resin sheet on the surface of a molding base material in a state in which it was in close contact with it from above and below, and laminating it at 100° C. using a thermal laminator.
When the bending strength of the obtained prepreg 1 was measured using the method described above, the bending strength Bc in the course direction was 157.00 MPa, the bending strength Bw in the wale direction was 158.50 MPa, and the strength anisotropy after molding was was 1.0%.
In addition, when the bending elastic modulus of the obtained prepreg 1 was measured using the method described above, the bending elastic modulus Mc in the course direction was 10.05 GPa, and the bending elastic modulus Mw in the wale direction was 10.25 GPa. The elastic modulus anisotropy was 2.0%.
Therefore, since the molded article obtained using the prepreg 1 has low strength anisotropy and elastic modulus anisotropy, it is considered to have excellent overall durability and be used for various purposes.

[Example 2]
<Manufacture of base material for molding>
Glass fibers with a fineness of 67.5 tex (multifilament aligned yarn, single fiber diameter: 9 μm, number of filaments: 400) were used as reinforcing fibers.
Using a 16-gauge flat knitting machine, knitting was carried out using all-needle rubber knitting with one glass fiber. Specifically, the carriage was reciprocated without shaking the needle bed.
As a result, the stitches are adjacent to the first stitch row diagonally at about 45° with respect to the wale direction, and the stitches are on the opposite side of the first stitch row with respect to the wale direction. A molding base material 2 (fabric weight: 577 g/m ² ), which is a knitted fabric base material repeatedly having a second stitch row obliquely moved by about 45°, was obtained.

<Manufacture of prepreg>
Prepreg 2 was obtained in the same manner as prepreg 1, except that molding base material 2 was used instead of molding base material 1, in which the ratio of resin to the entire prepreg was 60% by mass.
When the bending strength of the obtained prepreg 2 was measured by the method described above, the bending strength Bc in the course direction was 133.0 MPa, the bending strength Bw in the wale direction was 160.0 MPa, and the strength anisotropy after molding was was 18.4%.
In addition, when the bending elastic modulus of the obtained prepreg 1 was measured using the method described above, the bending elastic modulus Mc in the course direction was 10.9 GPa, and the bending elastic modulus Mw in the wale direction was 11.7 GPa. The elastic modulus anisotropy was 7.1%.
Therefore, since the molded article obtained using the prepreg 2 has low strength anisotropy and elastic modulus anisotropy, it is considered to have excellent overall durability and be used for various purposes.

<Rupture test (manufacture of molded body)>
In order to form into a deep drawing shape, a deep drawing mold was prepared based on the test jig shape of Method B specified in JIS L 1096:2010. Specifically, a mold 1 that forms a recess with an opening diameter d of 25 mm and a depth D of 10 mm (that is, a punch mold having a molding surface that forms a recess with an opening diameter d of 25 mm and a depth D of 10 mm) is used. deep drawing mold), a mold 2 that forms a recess with an opening diameter d of 25 mm and a depth D of 20 mm (that is, a molding surface that forms a recess with an opening diameter d of 25 mm and a depth D of 20 mm). (a deep drawing mold including a punch die having a punch die), and a mold 3 forming a recess with an opening diameter d of 25 mm and a depth D of 30 mm (that is, a recess with an opening diameter d of 25 mm and a depth D of 30 mm). A deep drawing mold (including a punch mold having a forming surface for forming a deep drawing mold) was prepared. Note that each of the recesses formed by the molds 1 to 3 has a circular opening and a curved top plate.
Using molds 1 to 3, molded bodies were produced under the conditions of a molding temperature of 150°C, a molding pressure of 4 kg/cm ² , and a molding time of 120 minutes, and the presence or absence of breakage of the molding base material in the obtained molded bodies was determined. , confirmed using an X-ray CT device (Bruker Co., Ltd., model number: skyscan2211, tube voltage: 50 kV, exposure time: 550 ms, detector: flat panel).
As a result, it was confirmed that all of the molded products were neatly molded without any breakage of the molding base material.
FIG. 3 shows an X-ray CT image of a molded product obtained by molding the prepreg 2 using the mold 3. From the X-ray CT image of FIG. 3, it can be seen that in the prepreg 2 molded body produced using the mold 3, the mesh structure of the recessed portions is nearly uniform.

[Comparative example 1]
<Manufacture of base material for molding>
As the reinforcing fibers, crimped glass fibers (crimped multifilament, single fiber diameter: 6 μm, number of filaments: 800) with a fineness of 70.0 tex were used.
Using a 16-gauge flat knitting machine, knitting was carried out using all-needle rubber knitting with one glass fiber. Specifically, the carriage was reciprocated without shaking the needle bed.
As a result, a molding base material C1 (fabric weight: 528 g/m ² ), which is a knitted fabric base material in which the stitches do not run obliquely with respect to the wale direction, was obtained.

<Manufacture of prepreg>
Using a phenol resin (manufactured by Risho Kogyo Co., Ltd.) as a resin material, the entire molding base material C1 was impregnated in the following manner to obtain a prepreg C1 in which the ratio of resin to the entire prepreg was 60% by mass. .
Specifically, the pre-molding base material was impregnated with a pre-cured phenol resin by hand coating, and the resin ratio was adjusted to 60% by mass using a mangle.
When the bending strength of the obtained prepreg C1 was measured by the method described above, the bending strength Bc in the course direction was 81.74 MPa, the bending strength Bw in the wale direction was 198.8 MPa, and the strength anisotropy after forming was found to be 81.74 MPa. was 83.4%.
In addition, when the bending elastic modulus of the obtained prepreg 1 was measured using the method described above, the bending elastic modulus Mc in the course direction was 5.0 GPa, and the bending elastic modulus Mw in the wale direction was 13.4 GPa. The elastic modulus anisotropy was 91.3%.

[Comparative example 2]
<Preparation of base material for molding>
A textile base material was prepared as the molding base material C2.
In addition, the above-mentioned textile base material uses glass fiber as a reinforcing fiber.

<Manufacture of prepreg>
Using phenol resin (manufactured by Risho Kogyo Co., Ltd.) as a resin material, the entire molding base material C2 was impregnated in the following manner to obtain a prepreg C2 in which the ratio of resin to the entire prepreg was 60% by mass. .
Specifically, the pre-molding base material was impregnated with a pre-cured phenol resin by hand coating, and the resin ratio was adjusted to 60% by mass using a mangle.

<Rupture test (manufacture of molded body)>
In the same manner as in Example 2, molded bodies were produced using molds 1 to 3, and the presence or absence of breakage of the molding base material in the obtained molded bodies was confirmed.
As a result, breakage of the molding base material was confirmed for all molded bodies.
FIG. 4 shows an X-ray CT image of a molded product obtained by molding using the mold 2. From the X-ray CT image in FIG. 4, it can be seen that in the prepreg C2 molded body produced using mold 2, the molding base material clearly breaks.

From the above results, it was found that when using a forming base material that is a knitted fabric base material of reinforcing fibers knitted by weft knitting, the strength anisotropy after forming and/or the elastic modulus anisotropy after forming is 30% or less. It has been found that by using a prepreg having the following properties, the base material is less likely to break during molding, and the molded product has excellent durability.

10 Recessed portion 12 Top plate portion 14 Vertical wall portion 16 Opening surface 100 Knitted fabric 112 First stitch row 114 Second stitch row

Claims (15)

A molding base material knitted by weft knitting using reinforcing fibers,
A resin impregnated into at least a portion of the molding base material and containing at least one selected from the group consisting of a room temperature curable resin, a thermosetting resin, and a thermoplastic resin;
has
The forming base material has a first stitch row in which the stitches are oblique to the wale direction, and is adjacent to the first stitch row, and the stitches are adjacent to the first stitch row in the wale direction. repeating a second row of stitches diagonally on the opposite side;
The bending strength Bc in the course direction of the molding base material when the molded product obtained by pressing using a heat press machine at 150 °C, 4 kg/cm ² , and 120 minutes is measured at 23 °C, and the molding A prepreg in which the bending strength Bw in the wale direction, the bending elastic modulus Mc in the course direction, and the bending elastic modulus Mw in the wale direction of the base material satisfy the following condition 1 and/or the following condition 2.
Condition 1: The absolute value of the difference between the Bc and the Bw is 30% or less of the average value of the Bc and the Bw. Condition 2: The absolute value of the difference between the Mc and the Mw is 30% or less of the average value of the Bc and the Bw. 30% or less of average value The reinforcing fibers include glass fibers, carbon fibers, silicon carbide fibers, metal fibers, aramid fibers, ultra-high molecular weight polyethylene fibers, basalt fibers, polyparaphenylene benzobis oxazole fibers, polyarylate fibers, polyacetal fibers, and polyvinyl alcohol fibers. The prepreg according to claim 1, comprising at least one selected from the group consisting of , fluororesin fibers, cellulose fibers, and nylon fibers. 3. The weft stitch includes at least one selected from the group consisting of rubber stitch, ridge stitch, pearl stitch, flat stitch, bag stitch, double-sided stitch, Milan rib, and pique stitch. prepreg. The prepreg according to any one of claims 1 to 3 , wherein the reinforcing fiber is a multifilament made of a plurality of single fibers. 5. The prepreg according to claim 4 , wherein the multifilament is a drawn yarn obtained by aligning a plurality of single fibers and/or a twisted yarn processed by twisting. A method for manufacturing the prepreg according to any one of claims 1 to 5 , comprising:
A step of manufacturing a forming base material knitted by weft knitting using reinforcing fibers by alternately repeating the following first step and the following second step using a flat knitting machine;
Impregnating at least a portion of the molding base material with a resin material containing at least one selected from the group consisting of a room temperature curable resin, a thermosetting resin, and a thermoplastic resin;
A method for producing a prepreg having the following.
First step: Step of forming a first stitch row in which the stitches are oblique to the wale direction by moving the carriage with the needle bed of the flat knitting machine swung to one side Second step: The above-mentioned By moving the carriage in the opposite direction to the first step with the needle bed swung in the opposite direction to the first step, the stitches are adjacent to the first stitch row and in the wale direction. On the other hand, forming a second stitch row diagonally opposite to the first stitch row. A method for manufacturing the prepreg according to claim 5 , comprising:
A step of manufacturing a forming base material knitted by weft knitting using reinforcing fibers by alternately repeating the following first step and the following second step using a flat knitting machine;
Impregnating at least a portion of the molding base material with a resin material containing at least one selected from the group consisting of a room temperature curable resin, a thermosetting resin, and a thermoplastic resin;
A method for producing a prepreg having the following.
First step: A step of moving the carriage of the flat knitting machine in one direction to form a first stitch row in which the stitches are oblique to the wale direction.Second step: Moving the carriage of the flat knitting machine to the first step. forming a second stitch row that is adjacent to the first stitch row and in which the stitches run diagonally on the opposite side of the first stitch row with respect to the wale direction by moving in the opposite direction. A molded article of the prepreg according to any one of claims 1 to 5 ,
A molded body including a recessed portion having a top plate portion and a vertical wall portion. The molded article according to claim 8 , wherein the recess has a ratio (D/d) of depth D to opening diameter d of 0.5 or more. The molded article according to claim 8 or 9 , wherein the top plate portion is flat. By molding the prepreg according to any one of claims 1 to 5 or the prepreg manufacturing method according to claim 6 or 7 , the top plate portion and the vertical wall portion can be formed. 1. A method for manufacturing a molded body, comprising a molding step of shaping the body into a shape including a concave portion. 12. The molding step includes a step of shaping by at least one molding method selected from the group consisting of press molding, hand lay-up molding, autoclave molding, RTM molding, pultrusion molding, and sheet winding molding. A method for producing a molded article. The method for manufacturing a molded article according to claim 11 , wherein the forming step is a step of performing deep drawing. 14. The method for producing a molded body according to claim 13 , wherein in the molding step, a punch mold having a flat molding surface forming the top plate portion is used. A molded article of prepreg according to any one of claims 1 to 5 .