JP2023008133A - Thermosetting resin composition, cured product, prepreg, and fiber-reinforced molding - Google Patents

Abstract

To improve production efficiency of a fiber-reinforced molding by curing the resin at low temperature and in a short time.SOLUTION: A thermosetting resin composition contains a resin containing a benzene ring structure and a reactive group in each molecule. In an infrared absorption spectrum after curing, the peak intensity of a peak having an absorption maximum in the region of 1500 cm-1±10 cm-1 is expressed as P1500, and the peak intensity of a peak having an absorption maximum in the region of 1560 cm-1±10 cm-1 is expressed as P1560, satisfying P1560/P1500≥0.2.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to thermosetting resin compositions, cured products, prepregs, and fiber-reinforced moldings.

In recent years, for the purpose of weight reduction and improvement of mechanical strength, composite materials (FRP) of reinforcing fiber base material such as carbon fiber and glass fiber and resin are widely used in various fields and applications (for example, patent documents 1, 2). In particular, in transportation equipment such as automobiles, railroads, and aircraft, there is a high demand for low fuel consumption, and the effect of reducing the weight of the aircraft is high, so FRP is expected as a metal substitute material for these applications.
Conventionally, thermosetting resins such as epoxy resins and phenolic resins have been used as matrix resins for FRP in many fields due to their excellent strength, rigidity, heat resistance, corrosion resistance, and the like. As the application development of FRP increases, the required properties, especially heat resistance, become more severe. In addition, in order to increase production efficiency, it is required to cure the matrix resin at a lower temperature and in a shorter time.

WO2019/167579 JP 2017-132896 A

Patent Documents 1 and 2 disclose thermosetting resin compositions having excellent heat resistance and excellent reactivity that can be cured in a short time.
However, in Patent Document 1, the curing temperature of the resin is as high as 210° C., and the curing time is 8 hours, which cannot be said to be efficient curing conditions. Moreover, in Patent Document 2, the curing temperature is as high as 200° C., which cannot be said to be low-temperature curing.
The present disclosure has been made in view of the above circumstances, and aims to improve production efficiency by curing at a low temperature in a short time.
The present disclosure can be implemented as the following forms.

A thermosetting resin composition containing a resin containing a benzene ring structure and a reactive group in the molecule,
In the infrared absorption spectrum after curing,
The peak intensity of the peak having an absorption maximum in the region of 1500 cm ⁻¹ ±10 cm ⁻¹ is represented as P ₁₅₀₀ ,
When the peak intensity of a peak having an absorption maximum in the region of 1560 cm ⁻¹ ±10 cm ⁻¹ is represented as P ₁₅₆₀ ,
_P1560 / _P1500 ≧0.2
A thermosetting resin composition.

The thermosetting resin composition of the present disclosure cures at a low temperature in a short period of time, thereby improving production efficiency.

1 is a cross-sectional view of a prepreg according to one embodiment of the present disclosure; FIG. FIG. 2 is a cross-sectional view of a fiber-reinforced compact according to one embodiment of the present disclosure; FIG. 3 is a cross-sectional view showing lamination and heat compression in one embodiment of the method for producing a fiber-reinforced molded body of the present disclosure. FIG. 4 is a cross-sectional view showing lamination and heat compression in one embodiment of the method for producing a fiber-reinforced molded body of the present disclosure. FIG. 5 is an IR chart of Examples 1 and 2. FIG. 6 is an IR chart of Examples 3 and 4. FIG. 7 is an IR chart of Examples 5, 7 and 6. FIG. FIG. 8 is an IR chart of Comparative Examples 1 and 2. FIG. 9 is an IR chart of Comparative Examples 3 and 4. FIG.

A preferred example of the present disclosure will now be presented.
- The said resin is a thermosetting resin composition which has two or more said reactive groups in one molecule.
- The thermosetting resin composition, wherein the resin is two or more kinds.
- The thermosetting resin composition, wherein the reactive group is selected from the group consisting of a cyanate group, a hydroxyl group, and an epoxy group.
- A cured product obtained by curing a thermosetting resin composition.
- A prepreg in which a fiber base material is impregnated with a thermosetting resin composition.
- A fiber-reinforced molded article in which a fiber base material is integrated with the resin of the thermosetting resin composition.
- A fiber-reinforced molded body,
A fiber-reinforced molded article having a flexural strength of 400 MPa or more and a flexural modulus of 50 GPa or more as measured according to JIS K7074 A method.
・According to JIS K7074 A method, the bending elastic modulus measured at a measurement atmosphere temperature of 23 ° C. is M ₂₃ ,
A fiber-reinforced molded article that satisfies the following relational expression, where M60 is the flexural modulus measured at an ambient temperature of ₆₀ °C while complying with JIS K7074 A method.

(M ₆₀ /M ₂₃ )×100≧90

The present disclosure will be described in detail below. In this specification, the description using "-" for the numerical range includes the lower limit and the upper limit unless otherwise specified. For example, the description “10-20” includes both the lower limit “10” and the upper limit “20”. That is, "10-20" has the same meaning as "10 or more and 20 or less".

1. Thermosetting resin composition A thermosetting resin composition is suitably used, for example, for producing fiber-reinforced moldings. A thermosetting resin composition contains a resin containing a benzene ring structure and a reactive group in the molecule.
The thermosetting resin composition has an infrared absorption spectrum after curing,
The peak intensity of the peak having an absorption maximum in the region of 1500 cm ⁻¹ ±10 cm ⁻¹ is represented as P ₁₅₀₀ ,
When the peak intensity of a peak having an absorption maximum in the region of 1560 cm ⁻¹ ±10 cm ⁻¹ is represented as P ₁₅₆₀ ,
P ₁₅₆₀ /P ₁₅₀₀ ≧0.2 Relational expression (1)
is.

The above relational expression (1) is
_P1560 / _P1500 ≧0.4
is preferred,
_P1560 / _P1500 ≧0.9
is more preferred.
In addition, P ₁₅₆₀ /P ₁₅₀₀ ≤ 1.5
is preferably satisfied.

The resin that can be contained in the thermosetting resin composition is not particularly limited as long as it satisfies the above relational expression (1) after curing. 1 type or 2 types or more may be sufficient as resin. The resin preferably has a plurality of reactive groups in one molecule before curing. The reactive groups are preferably selected from the group consisting of cyanate groups, hydroxyl groups and epoxy groups.
The resin is preferably selected from the group consisting of mixed resins of cyanate resin and phenol resin, and mixed resins of cyanate resin, epoxy resin and phenol resin. Further, a mixed resin of a cyanate resin and an epoxy resin or a mixed resin of an epoxy resin and a phenol resin may be used as long as the relational expression (1) is satisfied. As long as the relational expression (1) is satisfied, the resin is not limited to a mixed resin in which different kinds of resins are mixed, and may be a single resin such as a cyanate resin, an epoxy resin, or a phenol resin.
The cyanate resin used in this resin composition is a thermosetting resin having a cyanate group (cyanato group) and is also called a cyanate monomer. Physical properties of the cyanate resin before curing are not particularly limited. Those having a benzene ring and a plurality of cyanate groups in one molecule before curing are preferred. For example, a cyanate resin having the following physical properties is preferably employed.
・Melting point: 75°C or higher and 85°C or lower ・Viscosity: 0.010 Pa s or higher and 0.015 Pa s or lower (80°C)

As the epoxy resin, for example, a bisphenol A solid resin is preferably used. Those having a benzene ring and a plurality of epoxy groups in one molecule before curing are preferred. The physical properties of the epoxy resin are not particularly limited. For example, epoxy resins having the following physical properties are preferably employed.
・Epoxy equivalent: 400 g/eq to 1000 g/eq ・Softening point: 60 ° C to 100 ° C ・Viscosity: 0.10 Pa s to 0.30 Pa s (25 ° C)

As the phenolic resin, for example, a novolac type powdered phenolic resin is preferably used. Physical properties of the phenol resin are not particularly limited. For example, phenol resins having the following physical properties are preferably employed.
・Melting point: 80°C or higher and 100°C or lower

In addition, various powder additives such as pigments, antibacterial agents, ultraviolet absorbers, and curing agents are added to the thermosetting resin composition within a range that does not affect the viscosity and reactivity of the thermosetting resin composition. You may When no additive is added to the thermosetting resin composition, the thermosetting resin composition consists of a thermosetting resin.

When a mixed resin of a cyanate resin and a phenol resin is used as the resin, the cyanate resin is preferably 30 parts by mass or more and 70 parts by mass or less when the total of the cyanate resin and the phenol resin is 100 parts by mass. , 40 parts by mass or more and 60 parts by mass or less, and more preferably 45 parts by mass or more and 55 parts by mass or less.

When a mixed resin of cyanate resin, epoxy resin and phenol resin is used as the resin, the ratio of each resin is as follows when the total of cyanate resin, epoxy resin and phenol resin is 100 parts by mass. preferable.

<Preferred range>
Cyanate resin: 7 to 96 parts by mass Epoxy resin: 2 to 60 parts by mass Phenolic resin: 2 to 70 parts by mass

<More preferable range>
Cyanate resin: 10 to 94 parts by mass Epoxy resin: 3 to 55 parts by mass Phenolic resin: 3 to 60 parts by mass

<Further preferable range>
Cyanate resin: 12 to 92 parts by mass Epoxy resin: 4 to 50 parts by mass Phenolic resin: 4 to 58 parts by mass

2. Cured Product The cured product is obtained by curing the above-described “thermosetting resin composition”.

3. Prepreg Prepreg is obtained by impregnating a fiber base material with the thermosetting resin composition described in the section "1. Thermosetting resin composition". Prepregs are used as intermediates (precursors) for the production of fiber-reinforced moldings.
An example of a prepreg is shown in FIG. The prepreg 10 shown in FIG. 1 is obtained by heating and compressing the fiber base material 11 together with the thermosetting resin 15 , and the fiber base material 11 is impregnated with the thermosetting resin 15 . The thermosetting resin 15 impregnating the fiber base material 11 is in a solid state before starting the curing reaction. The thermosetting resin 15 does not necessarily impregnate the inside of the fiber base material 11 uniformly.

Although the fiber base material 11 consists of one layer in the prepreg 10 of FIG. 1, the prepreg may consist of a plurality of layers. The fiber base material 11 is not particularly limited. Examples of the fiber base material 11 include woven fabrics and non-woven fabrics made of glass fiber, aramid fiber, basalt fiber, carbon fiber, and the like. A carbon fiber fabric is preferable because it is excellent in light weight and high rigidity. As the carbon fiber fabric, a weaving method in which the fibers are not unidirectional is preferable. For example, plain weave, twill weave, satin weave composed of warp and weft, and triaxial weave composed of yarns in three directions are preferable. is. The carbon fiber fabric preferably has a fiber weight of 50 g/m ² to 600 g/m ² from the viewpoint of impregnation with the thermosetting resin 15 and rigidity of the fiber-reinforced molding.

The shape of the thermosetting resin 15 is not particularly limited. The thermosetting resin 15 is preferably in the form of a solid powder before heating and compression in the production of the prepreg 10 . Specific shapes of the powder are exemplified by spherical, acicular, flake and the like.
When the prepreg 10 is produced, the powder of the thermosetting resin 15 is arranged so as to be in contact with the fiber base material 11 . The thermosetting resin 15 is heated and compressed together with the fiber base material 11 and melted to impregnate the fiber base material 11, and then cooled and solidified. In this solidified state, the thermosetting resin 15 has not undergone a curing reaction and is uncured.

4. Fiber reinforced molding 20
(1) Structure of Fiber-Reinforced Molded Body 20 An example of the fiber-reinforced molded body 20 is shown in FIG. The fiber-reinforced molded body 20 is formed by integrating a fiber base material 11 with a resin 15 of a thermosetting resin composition.
For the thermosetting resin composition and the fiber base material 11, the descriptions in "1. Thermosetting resin composition" and "3. Prepreg" are cited as they are. The fiber base material 11 may have a single layer or multiple layers, and the number of layers is determined according to the application of the fiber-reinforced molding 20 and the like. In one form of FIG. 2, the fiber base material 11 consists of four layers.

(2) Physical Properties of Fiber-Reinforced Molded Body 20 (2.1) Bending Strength The bending strength (JIS K7074 A method) of the fiber-reinforced molded body 20 is not particularly limited. From the viewpoint of high strength, the bending strength of the fiber-reinforced molded body 20 is preferably 400 MPa or higher, more preferably 650 MPa or higher, and even more preferably 800 MPa or higher at a measurement ambient temperature of 23°C. A higher bending strength is desirable, but it is usually 1200 MPa or less.

(2.2) Bending Elastic Modulus The bending elastic modulus (JIS K7074 A method) of the fiber-reinforced molding 20 is not particularly limited. The flexural modulus of the fiber-reinforced molded body 20 is preferably 50 GPa or more at a measurement ambient temperature of 23° C. from the viewpoint of high rigidity. A higher flexural modulus is desirable, but it is usually 100 GPa or less.

(2.3) Retention rate of bending strength When the bending strength measured at a measurement atmosphere temperature of ₂₃ ° C. is S23 and the bending strength measured at a measurement atmosphere temperature of ₆₀ ° C. is S60, the following relational expression (2 ) is preferably satisfied.
(S ₆₀ /S ₂₃ )×100≧90 Relational expression (2)

The above relational expression (2) is
_(S60 / _S23 )×100≧95
is preferred,
(S ₆₀ /S ₂₃ )×100≧97
is more preferred.
In addition, (S ₆₀ /S ₂₃ ) × 100 ≤ 120
is more preferred.

(2.4) Retention rate of flexural modulus When the flexural modulus measured at a measurement atmosphere temperature of ₂₃ ° C. is M23, and the flexural modulus measured at a measurement ambient temperature of ₆₀ ° C. is M60, the following relationship It is preferable to satisfy formula (3).
(M ₆₀ /M ₂₃ )×100≧90 Relational expression (3)

The above relational expression (3) is
(M ₆₀ /M ₂₃ )×100≧95
is preferred,
(M ₆₀ /M ₂₃ )×100≧97
is more preferred.
In addition, (M ₆₀ /M ₂₃ ) × 100 ≤ 120
is preferred.

(3) Manufacturing Method of Fiber-Reinforced Molded Body 20 The fiber-reinforced molded body 20 is produced, for example, by heating and compressing the fiber base material 11 in contact with the powder of the thermosetting resin 15 with a mold to obtain a thermosetting resin. It is manufactured by impregnating the fiber base material 11 with the resin 15 and hardening it.

The manner in which the thermosetting resin 15 is arranged is not particularly limited. For example, when the fiber base material 11 is a single layer, it is arranged on at least one of the upper surface and the lower surface of the fiber base material 11 . When the fiber base material 11 has multiple layers, it is arranged on at least one of the top surface, the bottom surface, and the laminated surface (between the fiber base materials 11) in the multiple layers.
In addition, when the thermosetting resin 15 is arranged on the laminated surface (between the fiber base materials 11) of the multiple layers of the fiber base material 11, it is not limited to one laminated surface (between one fiber base material 11). (between all the fiber base materials) or every predetermined number of layers (between the predetermined number of fiber base materials 11). It is appropriately determined according to the number of layers of the base material 11 and the like.
Further, when the thermosetting resin 15 is arranged in contact with the upper or lower surface of the single-layer fiber base material 11 or the uppermost or lowermost surface of the multi-layer fiber base material 11, for convenience of work, the thermosetting resin 15 is A release sheet may be placed between the adhesive resin 15 and the mold surface of the mold.

An embodiment of the method for manufacturing the fiber-reinforced molding 20 shown in FIG. 2, in which the fiber base material 11 is composed of four layers, will be described with reference to FIG. In the following description of the manufacturing method, for the plurality of fiber base materials 11, in order to make it easier to grasp the vertical positional relationship, a plurality of reference numerals such as "11A" are used by combining "11" and "alphabet". A fibrous substrate 11 is shown.

In the embodiment shown in FIG. 3, when laminating the four fiber base materials 11A to 11D, the lower two fiber base materials 11A and 11B and the upper two fiber base materials 11C and 11D A thermosetting resin 15 is placed between the fiber bases 11 (between the fiber bases 11B and 11C).
The amount of the thermosetting resin 15 is preferably adjusted so that the VF value (%) of the fiber reinforced molded body 20 is 40%-75%. The VF value (%) is a value calculated by (total weight of fiber base/density of fiber)/(volume of fiber-reinforced molding)×100.

A laminate of fiber base materials 11A to 11D in which thermosetting resin 15 is placed between fiber base materials 11B and 11C and laminated is placed with lower mold 31 of heated mold 30. It is sandwiched between upper molds 32 and heated and compressed. The mold 30 is heated to a temperature at which the thermosetting resin 15 can be melted and cured by heating means such as an electric heater.

The pressure (compression) of the fiber base materials 11A to 11D during heat compression by the mold 30 is performed so that the fiber base materials 11A to 11D can be well impregnated after the thermosetting resin 15 between the fiber base materials 11 is melted. 2 MPa to 20 MPa is preferable in order to
Further, the compression rate (%) of the fiber base materials 11A to 11D is (the gap between the mold surface of the lower mold 31 and the mold surface of the upper mold 32)/(total thickness of all layers of the fiber base material)×100. It is a calculated value, preferably 60%-100%.

Heating of the laminate by the mold 30 melts the thermosetting resin 15 between the fiber bases 11 (between the fiber bases 11B and 11C), and the molten thermosetting resin 15 melts into the laminate. compression impregnates the lower fiber base materials 11B, 11A and the upper fiber base materials 11C, 11D. Then, by curing the thermosetting resin impregnated into the fiber base materials 11A to 11D, the fiber base materials 11A to 11D are integrated in a compressed state and shaped into the mold surface shapes of the lower mold 31 and the upper mold 32. The fiber-reinforced molded body 20 shown in FIG. 2 is obtained.

FIG. 4 shows an embodiment in which four fiber base materials 11A to 11D are laminated, thermosetting resins 15A, 15B, and 15C are placed between all the fiber base materials, and heat-compressed by a mold 30. FIG.
The amount (total amount) of the thermosetting resin, the heating temperature of the mold 30, the pressure applied to the laminate, etc. are as described in the embodiment of FIG.

1. Measurement of Infrared Absorption Spectra of Cured Resins Various cured resins were prepared and IR was measured.
(1) Production of cured resin product (1.1) Resins used in production of cured resin product Resins used in production of cured resin product are as follows. In the examples, no additive was added to the resin. In the examples, the resin itself corresponds to the "thermosetting resin composition" in the present disclosure.

<Resin used>
・ Cyanate resin: manufactured by Mitsubishi Gas Chemical Company, Inc., product name: CYTESTER TA, average particle size: 100 μm (used after crushing in a mortar)
・ Epoxy resin: manufactured by Mitsubishi Chemical Corporation, product name: jER-1001, average particle size: 100 μm (used after crushing in a mortar)
・ Phenolic resin 1: manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-50235D, average particle size: 90 μm (used after crushing in a mortar)
・ Phenolic resin 2: manufactured by Sumitomo Bakelite Co., Ltd., product name: PR-55236, average particle size: 30 μm

(1.2) Example 1-7
Resin cured products of Examples 1-7 were produced using the resins shown in Table 1. The cured resin was used for IR measurements.
Specifically, 10 g of the resin mixed at the resin ratio shown in Table 1 was put on the lower mold of the mold heated to 150 ° C., the mold was closed, and heat compression was performed at a pressure of 5 MPa for 10 minutes. , to prepare a cured resin. A spacer with a thickness of 1 mm was inserted between the upper mold and the lower mold to adjust the mold clearance. Phenolic Resin 1 was used in Examples 1-7.

(1.3) Comparative Example 1-4
Resin cured products of Comparative Examples 1-4 were produced using the resins shown in Table 1. The cured resin was used for IR measurements.
Specifically, 10 g of the resin mixed at the resin ratio shown in Table 1 was put on the lower mold of the mold heated to 150 ° C., the mold was closed, and heat compression was performed at a pressure of 5 MPa for 10 minutes. , to prepare a cured resin. A spacer with a thickness of 1 mm was inserted between the upper mold and the lower mold to adjust the mold clearance. Comparative Example 1 used phenol resin 2, and Comparative Examples 2 and 3 used phenol resin 1.

(2) IR measurement of cured resin (2.1) Measurement method FT/IR-6700 type A manufactured by JASCO Corporation was used for measurement. Measurement was performed by the ATR method with 20 integration times, a resolution of 4 cm ⁻¹ , and a measurement frequency range of 400 cm ⁻¹ to 4,000 cm ⁻¹ . The IR chart is shown in Figure 5-9.
(2.2) Calculation of Absorbance Peak Intensity Ratio An absorbance peak (reference peak) derived from a structure that does not change before and after heat curing was used as a reference. The intensity ratio (object peak intensity/reference peak intensity) of the absorbance peak (target peak) appearing after curing with respect to the reference peak was determined. A peak near 1,507 cm ⁻¹ (1500 cm ⁻¹ ±10 cm ⁻¹ ) derived from a benzene ring was used as a reference peak. For each peak intensity, the value of the peak height in the IR chart was adopted.
Table 2 shows specific wavenumbers of the reference peak and the target peak used in Examples 1-7 and Comparative Examples 1-4.
The peak near 1207 cm ⁻¹ in Comparative Example 1 is different from the other peaks in that it has a fairly broad peak shape and is considered to be derived from hydroxyl groups (—OH).

(3) Measurement results Table 1 also shows the absorbance peak intensity ratio of each resin. In Example 1-7, the ratio of the peak intensity near 1,560 cm ⁻¹ to the peak intensity near 1,507 cm ⁻¹ , that is, P ₁₅₆₀ /P ₁₅₀₀ was 0.2 or more.
On the other hand, in Comparative Example 1-4, the ratio of the peak intensity near 1,560 cm ⁻¹ to the peak intensity near 1,507 cm ⁻¹ , that is, P ₁₅₆₀ /P ₁₅₀₀ was 0.2 or less.

2. Evaluation of fiber reinforced molded body (1) Fabrication of fiber reinforced molded body (1.1) Example 1-6
As a fiber base material for reinforcement, four carbon fiber fabrics (manufactured by Teijin Limited, product name: W-3101, weight per unit area: 200 g/m ² , thickness: 0.22 mm) cut into 250 mm × 200 mm sheets were prepared. The weight per sheet of the carbon fiber fabric after cutting was 10 g. Two fiber base materials were laminated, and 30 g of a resin mixed at the resin ratio shown in Table 1 was uniformly placed thereon. Furthermore, a pre-molding laminate was produced by laminating the remaining two fiber base materials thereon. Phenolic Resin 1 was used in Examples 1-6.
Next, the pre-molded laminate is placed on the molding surface of the lower mold of the mold heated to 150 ° C., and then the mold is closed and heated and compressed at a pressure of 5 MPa for 10 minutes to form a solid thermosetting resin. Melt hardened. After the solid thermosetting resin is melted, pressure is applied, and the fiber base material of each layer is impregnated with the resin, the thermosetting is completed, so that the fiber consists of a laminated integral product of the fiber base material and the thermosetting resin. A reinforced molded body (composite molded body) was produced.

(1.2) Example 7
As a fiber base material for reinforcement, four carbon fiber fabrics (manufactured by Teijin Limited, product name: W-3101, weight per unit area: 200 g/m ² , thickness: 0.22 mm) cut into 250 mm × 200 mm sheets were prepared. The weight per sheet of the carbon fiber fabric after cutting was 10 g. One fiber base material was placed on a release-treated PET film, and 7.5 g of the powdered resin mixed at the ratio of Example 7 was generally evenly placed on the fiber base material. This laminate was heated in an oven at 100° C. for 10 minutes, then taken out and allowed to cool, thereby producing a prepreg in which the fiber base material was melt-impregnated with the resin. In Example 7, Phenolic Resin 1 was used.
A laminate of four prepregs prepared in the same manner was placed on the molding surface of the lower mold of the mold heated to 150 ° C., and then the mold was closed and heat-compressed at a pressure of 5 MPa for 10 minutes to obtain a fiber. A fiber-reinforced molded article (composite molded article) consisting of a laminated integral product of a base material and a thermosetting resin was produced.

(1.3) Comparative Example 1-4
As a fiber base material for reinforcement, four carbon fiber fabrics (manufactured by Teijin Limited, product name: W-3101, weight per unit area: 200 g/m ² , thickness: 0.22 mm) cut into 250 mm × 200 mm sheets were prepared. The weight per sheet of the carbon fiber fabric after cutting was 10 g. Two fiber base materials are laminated, 30 g of a resin mixed at the resin ratio shown in Table 1 is generally uniformly placed thereon, and the remaining two reinforcing fiber base materials are further laminated thereon. A pre-molding laminate was produced. Comparative Example 1 used phenol resin 2, and Comparative Examples 2 and 3 used phenol resin 1.
Next, the pre-molded laminate is placed on the molding surface of the lower mold of the mold heated to 150 ° C., and then the mold is closed and heated and compressed at a pressure of 5 MPa for 10 minutes to form a solid thermosetting resin. Melt hardened. After the solid thermosetting resin is melted, pressure is applied, and the fiber base material of each layer is impregnated with the resin, the thermosetting is completed, so that the fiber consists of a laminated integral product of the fiber base material and the thermosetting resin. A reinforced molded body (composite molded body) was produced. Comparative Example 1 used phenol resin 2, and Comparative Examples 2 and 3 used phenol resin 1.
In Comparative Example 4, after heating for 10 minutes, the fiber-reinforced molded article was significantly deformed when it was removed from the mold, and a good fiber-reinforced molded article could not be obtained.

(2) Physical Properties of Fiber-Reinforced Molded Article (2.1) Measuring Method of Flexural Strength and Flexural Modulus A test piece of 15 mm×100 mm cut out from the fiber-reinforced molded article was used for the measurement. The flexural strength and flexural modulus were measured at ambient temperatures of 23° C. and 60° C. according to JIS K7074 A method. The property retention rate was calculated by dividing the value obtained at 60°C by the value obtained at 23°C.
That is, ₍ M60/ _M23 )×100 was obtained, where M23 is the flexural modulus measured at an atmospheric temperature of ₂₃ °C, and M60 is the flexural modulus measured at an atmospheric temperature of ₆₀ °C.
Also, the bending strength measured at a measurement ambient temperature of ₂₃ °C was defined as S23, and the bending strength measured at a measurement ambient temperature of ₆₀ °C was defined as S60, and ( _S60 / _S23 ) x 100 was obtained.

(2.2) Appearance Evaluation Method Appearance was visually confirmed. Appearance was determined by visually confirming whether or not defects such as deformation and non-uniform resin impregnation exist on the surface of the fiber-reinforced molded body. Evaluation is as follows.

A: No problem B: Partial (area ratio of 30% or less) non-uniform impregnation C: Large deformation exceeding 30% area ratio and/or large non-uniform impregnation exceeding 30% area ratio case

(3) Measurement results Table 3 shows the measurement results.

Examples 1-7 satisfy the following requirement (a). On the other hand, Comparative Examples 1-4 do not satisfy the requirement (a).
・Requirement (a): P ₁₅₆₀ /P ₁₅₀₀ ≥ 0.2

In Example 1-7, which satisfies the requirement (a), the curing temperature was relatively low at 150° C., the curing time was relatively short at 10 minutes, and a fiber-reinforced molded article with good appearance and high heat resistance was obtained. was taken. That is, the fiber-reinforced moldings of Examples 1-7 exhibited high values of M ₆₀ /M ₂₃ and S ₆₀ /S ₂₃ and had high heat resistance. In addition, the fiber-reinforced molded article of Example 1-7 had a flexural strength of 400 MPa or more and a flexural modulus of 50 GPa or more at a measured atmospheric temperature of 23° C., and had good physical properties.
It was confirmed that the fiber-reinforced molded article of Comparative Example 1-3, which did not satisfy the requirement (a), exhibited low values of M ₆₀ /M ₂₃ and S ₆₀ /S ₂₃ , indicating low heat resistance.
In addition, the fiber-reinforced molded article of Comparative Example 2-3 was inferior in appearance.
Moreover, in Comparative Example 4, significant deformation occurred, and a good fiber-reinforced molded article could not be obtained. Therefore, the flexural strength and flexural modulus of the fiber-reinforced molding could not be measured.

3. Effects of Examples The fiber-reinforced moldings of Examples 1-6 could be produced by curing at a low temperature for a short period of time. The fiber-reinforced molded article produced in Example 1-6 had good flexural strength and flexural modulus at a measured atmospheric temperature of 60° C., and had high heat resistance.
The prepreg of Example 7 could be cured at a low temperature in a short time. The fiber-reinforced molded article produced in Example 7 had good flexural strength and flexural modulus at a measured atmospheric temperature of 60°C, and high heat resistance.

The present disclosure is not limited to the embodiments detailed above, and various modifications or alterations are possible.

DESCRIPTION OF SYMBOLS 10... Prepreg 11... Fiber base material 15... Thermosetting resin 20... Fiber reinforced molding 30... Mold 31... Lower mold 32... Upper mold

Claims (9)

A thermosetting resin composition containing a resin containing a benzene ring structure and a reactive group in the molecule,
In the infrared absorption spectrum after curing,
The peak intensity of the peak having an absorption maximum in the region of 1500 cm ⁻¹ ±10 cm ⁻¹ is represented as P ₁₅₀₀ ,
When the peak intensity of a peak having an absorption maximum in the region of 1560 cm ⁻¹ ±10 cm ⁻¹ is represented as P ₁₅₆₀ ,
_P1560 / _P1500 ≧0.2
A thermosetting resin composition. 2. The thermosetting resin composition according to claim 1, wherein said resin has a plurality of said reactive groups in one molecule. 3. The thermosetting resin composition according to claim 1, wherein two or more kinds of said resins are used. 4. The thermosetting resin composition according to any one of claims 1 to 3, wherein said reactive group is selected from the group consisting of cyanate group, hydroxyl group and epoxy group. A cured product obtained by curing the thermosetting resin composition according to any one of claims 1 to 4. A prepreg in which a fiber base material is impregnated with the thermosetting resin composition according to any one of claims 1 to 4. A fiber-reinforced molded article in which a fiber base material is integrated with the resin of the thermosetting resin composition according to any one of claims 1 to 4. The fiber-reinforced molded article according to claim 7,
A fiber-reinforced molded article having a flexural strength of 400 MPa or more and a flexural modulus of 50 GPa or more as measured according to JIS K7074 A method. According to JIS K7074 A method, the bending elastic modulus measured at a measurement atmosphere temperature of 23 ° C. is defined as M ₂₃ ,
The fiber-reinforced molded article according to claim 8, which also satisfies the following relational expression, where M60 is the flexural modulus measured at an atmospheric temperature of ₆₀ °C while conforming to JIS K7074 A method.

(M ₆₀ /M ₂₃ )×100≧90

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