JP-7856911-B2 - Glass-reinforced resin molded products

Inventors

• 貫井 洋佑

Assignees

• 日東紡績株式会社

Dates

Publication Date

20260512

Application Date

20220328

Priority Date

20210531

Claims (6)

1. A glass-reinforced resin molded product comprising a glass reinforcing material in an amount of 10.0 to 90.0% by mass relative to the total amount of the glass-reinforced resin molded product, and a thermoplastic resin, The glass reinforcing material includes flattened cross-sectional glass fibers having a flattened cross-sectional shape in which the ratio of the major axis to the minor axis (major axis/minor axis) is in the range of 3.0 to 10.0. The content C of the flattened cross-section glass fibers relative to the total amount of the glass-reinforced resin molded product is in the range of 10.0 to 80.0% by mass. The major axis D of the flattened cross-section glass fiber is in the range of 30.0 to 55.0 μm. The proportion P of glass reinforcing materials having a length in the range of 50 to 100 μm, relative to the total number of glass reinforcing materials having a length of 50 μm or more, is in the range of 4 to 50%. A glass-reinforced resin molded product characterized in that C, D, and P satisfy the following formula (1). 0.46 ≦ P/(C×D) 1/2 ≦ 0.99 (1)
2. A glass-reinforced resin molded article according to claim 1, characterized in that C is in the range of 20.0 to 70.0% by mass, D is in the range of 30.0 to 50.0 μm, P is in the range of 10 to 40%, and C, D, and P satisfy the following formula (2). 0.54 ≦ P/(C×D) 1/2 ≦ 0.72 ... (2)
3. A glass-reinforced resin molded article according to claim 1 or claim 2, characterized in that the flattened cross-sectional glass fibers have a flattened cross-sectional shape in which the ratio of the major axis to the minor axis is in the range of 5.0 to 8.0.
4. A glass-reinforced resin molded article according to any one of claims 1 to 3, characterized in that the thermoplastic resin is one thermoplastic resin selected from the group consisting of polycarbonate, polybutylene terephthalate, polyetheretherketone, or polyamide.
5. A glass-reinforced resin molded article according to claim 4, characterized in that the thermoplastic resin is polycarbonate or polyamide.
6. A glass-reinforced resin molded article according to claim 4, characterized in that the thermoplastic resin is a polyamide.

Description

This invention relates to glass-reinforced resin molded articles. Conventionally, glass-reinforced resin molded articles containing flat-section glass fibers with a flattened cross-sectional shape are known as glass reinforcing materials (see, for example, Patent Documents 1 and 2). Glass-reinforced resin molded articles containing flat-section glass fibers as glass reinforcement material exhibit superior dimensional stability and reduced warping compared to glass-reinforced resin molded articles containing circular-section glass fibers, and also have superior mechanical properties and surface smoothness. Therefore, they are used in lightweight, thin, and compact components such as portable electronic device casings. As described in Patent Documents 1 and 2, attempts have been made to increase the fiber length of the flat-section glass fibers contained in glass-reinforced resin molded articles containing flat-section glass fibers in order to improve their mechanical properties. Japanese Patent Publication No. 2015-105359Japanese Patent Publication No. 2010-222486 Next, embodiments of the present invention will be described in more detail. The glass-reinforced resin molded product of this embodiment is a glass-reinforced resin molded product comprising 10.0 to 90.0% by mass of glass reinforcing material and 90.0 to 10.0% by mass of thermoplastic resin, wherein the glass reinforcing material comprises flat cross-sectional glass fibers having a flat cross-sectional shape with a ratio of major axis to minor axis (major axis/minor axis) in the range of 3.0 to 10.0, the content C of the flat cross-sectional glass fibers in the total amount of the glass-reinforced resin molded product being in the range of 10.0 to 80.0% by mass, the major axis D of the flat cross-sectional glass fibers being in the range of 30.0 to 55.0 μm, and the ratio P of glass reinforcing materials having a length in the range of 50 to 100 μm to the total number of glass reinforcing materials having a length of 50 μm or more contained in the glass-reinforced resin molded product being in the range of 4 to 50%, and C, D, and P satisfy the following formula (1). 0.46 ≦ P/(C×D) 1/2 ≦ 0.99 ... (1) Here, the larger P is, the less anisotropy the shrinkage rate becomes, but the absolute value of the shrinkage rate in the TD direction tends to worsen. Also, the larger C is, the larger the value of P becomes, and while the absolute value of the shrinkage rate in the TD direction decreases, the anisotropy of the shrinkage rate tends to worsen. Also, the larger D is, the larger the value of P tends to become, and while the anisotropy of the shrinkage rate decreases, the absolute value of the shrinkage rate in the TD direction also tends to decrease. Equation (1) is presumed to reflect these trends and express the balance between the reduction of shrinkage rate anisotropy and the reduction of the absolute value of the shrinkage rate in the TD direction. The glass-reinforced resin molded product of this embodiment can be obtained, for example, by kneading the glass reinforcing material and the thermoplastic resin in a twin-screw kneader and performing injection molding using the resulting resin pellets. In the glass-reinforced resin molded product of this embodiment, for example, flat-section glass fibers, circular-section glass fibers, glass flakes, glass powder, glass beads, etc., can be used as the glass reinforcing material. The glass composition of the glass forming the flattened cross-section glass fibers or the circular cross-section glass fibers is not particularly limited. In the glass-reinforced resin molded product of this embodiment, possible glass compositions for the glass fibers include the most common E glass composition, a high-strength, high-modulus glass composition, a high-modulus, easy-to-manufacture glass composition, and a low-dielectric-constant, low-dielectric-loss-tangent glass composition. From the viewpoint of improving the strength of the glass-reinforced resin molded product, the glass composition of the glass fibers is preferably the high-strength, high-modulus glass composition or the high-modulus, easy-to-manufacture glass composition. From the viewpoint of reducing the dielectric constant and dielectric-loss-tangent of the glass-reinforced resin molded product and thereby reducing the transmission loss of high-frequency signals passing through the glass-reinforced resin molded product, the glass composition of the glass fibers is preferably the low-dielectric-constant, low-dielectric-loss-tangent glass composition. The E glass composition is composed of SiO₂ in the range of 52.0 to 56.0 mass%, Al₂O₃ in the range of 12.0 to 16.0 mass%, MgO and CaO in total in the range of 20.0 to 25.0 mass%, and B₂O₃ in the range of 5.0 to 10.0 mass%, relative to the total amount of glass fibers. The high-strength, high-modulus glass composition is a composition that includes SiO₂ in the range of 60.0 to 70.0 mass % , Al₂O₃ in the range of