JP2018154773A - Fiber-reinforced composite resin sheet and molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fiber-reinforced composite resin sheet with excellent adhesion between carbon fiber and polypropylene and with excellent thermal stability, and provide a carbon fiber-reinforced composite material with excellent mechanical properties applicable for a structure material.SOLUTION: A fiber-reinforced composite resin sheet contains a matrix component of the following polypropylene (A), and a reinforced fiber of carbon fiber (B). The polypropylene (A) contains an acid-modified polypropylene (A-1) with an acid amount of 1.0-5.0%, of 0.3-9.0 mass%, and an un-acid-modified polypropylene (A-2) of 91.0-99.7 mass%, with the acid amount of 0.006-0.2% in terms of maleic anhydride.SELECTED DRAWING: None

Description

  The present invention relates to a fiber reinforced composite resin sheet and a molded product made of polypropylene and carbon fiber. More specifically, the present invention relates to a fiber-reinforced composite resin sheet that has an excellent balance between mechanical properties and thermal stability and is suitable for stamping molding.

One method for forming a carbon fiber reinforced composite material is to use a fiber reinforced composite resin sheet obtained by impregnating a thermoplastic resin composition into a carbon fiber aggregate such as a carbon fiber bundle or a carbon fiber fabric. For example, carbon fiber is obtained by laminating a fiber reinforced composite resin sheet or by dispersing a sheet piece formed by cutting a fiber reinforced composite resin sheet on a mold or the like, and then heating and pressure cooling this. And the thermoplastic resin composition which is a matrix resin are integrated. A carbon fiber reinforced composite material using a thermoplastic resin composition is excellent in impact resistance and has a short molding time, and is therefore optimal for automotive parts and the like. (Patent Document 1)
In recent years, carbon fiber reinforced composite materials have been required to be lighter and more economical, and light weight olefin resins, particularly polypropylene resins, are preferably used as matrix resins.

  For example, it is disclosed that a carbon fiber thermoplastic resin prepreg using maleic anhydride-modified polypropylene and polypropylene containing no acid group is excellent in releasability. (Patent Document 2)

JP-A-9-155862 JP 2014-234509 A

  However, although the technique disclosed in Patent Document 5 is excellent in strength development and mold release properties, it is molded using an autoclave and does not mention whether it has thermal stability suitable for stamping molding.

  An object of this invention is to provide the fiber reinforced composite resin sheet which has the thermal stability suitable for stamping shaping | molding, and the outstanding mechanical characteristic applicable to a structural material in view of a prior art.

As a result of intensive studies to solve the above problems, the present inventors have found that a specific acid-modified polypropylene resin and an unmodified polypropylene resin may be used in a certain ratio, and have completed the present invention. . That is, the gist of the present invention resides in the following [1] to [7].
[1] A fiber-reinforced composite resin sheet in which the matrix component is the following polypropylene (A) and the reinforcing fibers are carbon fibers (B). Propylene (A): Acid-modified polypropylene (A-1) 0.3 to 9.0% by mass with an acid amount of 1.0 to 5.0%, and non-acid-modified polypropylene (A-2) 91.0 The amount of acid is 0.006 to 0.2% in terms of maleic anhydride.
[2] The fiber-reinforced composite resin sheet according to the above [1], comprising 35 to 75% by mass of polypropylene (A) and 25 to 65% by mass of carbon fiber (B).
[3] The fiber-reinforced composite resin sheet according to the above [1] or [2], wherein the fiber length of the carbon fiber (B) is 10 mm or more.
[4] The fiber-reinforced composite resin sheet according to any one of [1] to [3], wherein the carbon fibers (B) are carbon fibers that are aligned in one direction.
[5] The fiber-reinforced composite resin sheet according to any one of the above [1] to [4], wherein two or more layers containing polypropylene (A) and carbon fibers (B) aligned in one direction are laminated.
[6] The fiber-reinforced composite resin sheet according to any one of [1] to [5], wherein the weight loss when heated at 300 ° C. for 1 hour in a nitrogen atmosphere is 1% or less.
[7] A molded product obtained by press-molding the fiber-reinforced composite resin sheet according to any one of [1] to [6].

  According to the present invention, it is possible to obtain a fiber-reinforced composite resin sheet having good adhesion between carbon fiber and polypropylene and excellent in thermal stability, and having excellent mechanical properties applicable to structural materials. A fiber reinforced composite material can be obtained.

Hereinafter, the present invention will be described in detail.
In the fiber-reinforced composite resin sheet of the present invention, the matrix component is polypropylene (A), and the reinforcing fibers are carbon fibers (B). Because the matrix component is polypropylene, it achieves moldability and excellent chemical resistance. Further, excellent mechanical properties are realized by using carbon fiber as the reinforcing fiber.

  Polypropylene (A) includes acid-modified polypropylene (A-1) and non-acid-modified polypropylene (A-2). The acid-modified polypropylene (A-1) can increase the interfacial strength between the polypropylene (A) and the carbon fiber (B), and exhibits excellent mechanical properties. Moreover, the outstanding mechanical characteristic of a polypropylene is not impaired by including the polypropylene (A-2) which is not acid-modified.

  The acid component contained in the acid-modified polypropylene (A-1) used in the present invention is not particularly limited, and examples thereof include carboxylic anhydrides, unsaturated sulfonic acids, and unsaturated phosphoric acids, and maleic anhydride is preferable. The acid amount of the acid-modified polypropylene (A-1) is 1.0 to 5.0%, preferably 1.5 to 4.0%, more preferably 2.0 to 3.0%. In addition, when using multiple types of resin as a component (A-1), it is preferable that the average content calculated | required by these weighted averages exists in said range.

When the acid amount of the acid-modified polypropylene (A-1) is 1.0% or more, sufficient adhesion with the carbon fiber (B) is obtained, and good mechanical properties are obtained when a molded body described later is obtained. It is done. On the other hand, if the acid amount is extremely increased, the processability is impaired and the characteristics as polypropylene tend to be lost, but the acid amount is 5.0% or less, without impairing the characteristics as polypropylene, That is, the heat resistance, strength / impact resistance, chemical resistance, and the like of a molded product produced using the same can be maintained, and the molded product can be handled without causing an increase in volatile components accompanying an increase in low molecular weight components.
The acid-modified polypropylene (A-1) may contain a partial structure other than propylene or an acid component in the molecule as long as the effects of the present invention are not impaired. Examples of the monomer constituting the partial structure include α-olefins, conjugated dienes, and non-conjugated dienes.

  Examples of the α-olefin include ethylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene, 4,4 dimethyl- 1-hexene, 1-nonene, 1-octene, 1-heptene, 1-hexene, 1-decene, 1-undecene, 1-dodecene and other C2-C12 α-olefins excluding propylene, etc. Examples of the conjugated diene and non-conjugated diene include butadiene, ethylidene norbornene, dicyclopentadiene, 1,5-hexadiene, and the like. These can select one type or two or more types.

  Or (meth) acrylic acid esters, hydroxyl group-containing vinyls, epoxy group-containing vinyls, isocyanate group-containing vinyls, aromatic vinyls, amides, aminoalkyl (meth) acrylates, etc. .

  The weight average molecular weight of the acid-modified polypropylene (A-1) is usually 1,000 to 500,000, preferably 20,000 to 80,000.

Component (A-1) can be produced by a known method. Appl. Polym. Sci. 53, 239 (1994), it is obtained by heating and mixing a propylene resin, maleic anhydride and an organic peroxide in an organic solvent.
The acid content of component (A-1) can be calculated from the acid value determined by the method described in JIS K0070.

  Non-acid-modified polypropylene (A-2) includes, for example, a propylene homopolymer, a block or random copolymer of propylene and at least one α-olefin, conjugated diene, non-conjugated diene, or the like. .

  Examples of the α-olefin include ethylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene, 4,4. Examples thereof include α-olefins having 2 to 12 carbon atoms excluding propylene such as dimethyl-1-hexene, 1-nonene, 1-octene, 1-heptene, 1-hexene, 1-decene, 1-undecene and 1-dodecene. It is done. Examples of the conjugated diene and non-conjugated diene include butadiene, ethylidene norbornene, dicyclopentadiene, 1,5-hexadiene, and the like. These monomers other than propylene may be used alone or in combination of two or more.

  The weight average molecular weight of a component (A-2) is 30,000-500,000 normally, Preferably it is 150,000-500,000.

  Polypropylene (A) contains 0.3 to 9.0% by mass of acid-modified polypropylene (A-1) and 91.0 to 99.7% by mass of non-acid-modified polypropylene (A-2). 1) It is preferable to contain 0.6-6.0 mass% and (A-2) 94.0-99.4 mass%, (A-1) 0.8-3.0 mass% and (A- 2) It is more preferable that 97.0-99.2 mass% is included. When the acid-modified polypropylene (A-1) is 0.3% by mass or more, sufficient adhesion with the carbon fiber (B) can be obtained, and good mechanical properties can be obtained when a molded body described later is obtained. On the other hand, when the amount of acid-modified polypropylene is extremely increased, the processability is impaired and the characteristics as polypropylene tend to be lost. However, when (A-1) is 9.0% by mass or less, Without damaging the characteristics, that is, maintaining the heat resistance, strength / impact resistance, chemical resistance, etc. of molded products manufactured using the same, and without increasing the volatile components accompanying the increase in low molecular weight components It can be handled.

  The acid amount of polypropylene (A) is 0.006 to 0.2% in terms of maleic anhydride. 0.01 to 0.15% is preferable, and 0.02 to 0.05% is more preferable.

  When the acid amount of the polypropylene (A) is 0.006% by mass or more, the carbon fiber (B) and sufficient adhesiveness can be obtained, and good mechanical properties can be obtained when a molded body described later is obtained. On the other hand, if the acid amount is extremely increased, the processability is impaired and the characteristics as polypropylene tend to be lost. However, when the acid amount of (A) is 0.2% or less, the characteristics as polypropylene are reduced. Handle the product without damage, that is, maintain the heat resistance, strength / impact resistance, chemical resistance, etc. of the molded product manufactured using the product without causing an increase in volatile components due to an increase in low molecular weight components. Can do.

  Polypropylene (A) may contain other components. Optional other components include, for example, inorganic fillers, flame retardants, conductivity-imparting agents, crystal nucleating agents, ultraviolet absorbers, antioxidants, vibration agents, antibacterial agents, insect repellents, deodorants, anti-coloring agents, and heat stability. Agents, mold release agents, antistatic agents, plasticizers, lubricants, colorants, pigments, dyes, foaming agents, antifoaming agents, or coupling agents.

  There is no restriction | limiting in particular in the carbon fiber (B) used for this invention, What is necessary is just to select suitably from well-known things. Examples of the carbon fiber include PAN-based carbon fiber and pitch-based carbon fiber, and PAN-based carbon fiber is preferable from the balance of strength and elastic modulus. The average single fiber fineness of the single fibers constituting the carbon fiber is preferably 0.30 dtex or more and 2.4 dtex or less, more preferably 1.0 dtex or more and 2.4 dtex or less. By setting the average single fiber fineness to 1.0 dtex or more, it is possible to achieve both good adhesive strength and releasability with a smaller acid content of the matrix resin due to a reduction in the interface area between the carbon fiber and the matrix resin. Moreover, by setting it to 2.4 dtex or less, it is possible to suppress firing spots on the cross section of the carbon fiber even with an appropriate flame resistance time, there is no decrease in the strand strength and elastic modulus, and the mechanical properties of the carbon fiber reinforced composite material may be decreased. It is preferable because it is not present.

  As will be described later, the fiber-reinforced composite resin sheet of the present invention is preferably produced by impregnating a matrix resin into a carbon fiber aggregate such as a carbon fiber bundle or a carbon fiber fabric. As the carbon fiber aggregate, in addition to the carbon fiber bundle, a woven fabric such as plain weave, twill weave and satin weave produced using the carbon fiber bundle, a state in which the fiber bundle is laminated in one direction or at different angles. Examples thereof include a stitching sheet such as a non-crimp fabric that is stitched so as not to loosen one, a non-woven fabric, a mat-like material, and a unidirectional material in which reinforcing fiber bundles are aligned in one direction.

  When the carbon fiber (B) is a carbon fiber bundle, the number of filaments of the carbon fiber (B) constituting the carbon fiber bundle is not particularly limited, but is desirably 1000 or more and 100,000 or less, and one kind is used alone. Two or more types may be used in combination.

The method for producing the fiber-reinforced composite resin sheet of the present invention is not particularly limited.
1) A method in which polypropylene (A) is heated and melted in an extruder, and a carbon fiber aggregate is spread and impregnated therein.
2) A method of pulverizing polypropylene (A) prepared in advance, dispersing it on the surface of the carbon fiber assembly, and melting it,
3) A method of forming a polypropylene (A) film prepared in advance and laminating it on a carbon fiber assembly,
4) A method of fiberizing polypropylene (A) prepared in advance and using this and carbon fiber as a mixed yarn,
5) A method of shaping a molding material containing polypropylene (A) and carbon fiber (B) to form a sheet. 6) A method of laminating sheets obtained by the above methods 1) to 5).

The method of impregnating the molten resin of 1) above with an extruder has the advantage that it is not necessary to process the resin in advance, but it is difficult to produce a sheet with stable quality.
The method 2) of dispersing the powdered resin in the fiber layer is advantageous in that it is easily impregnated, but it is difficult to uniformly disperse the powder in the fiber layer.
The method of laminating the resin of the above 3) needs to be processed into a film, but is preferred because it tends to produce a relatively good quality.
The method using the polypropylene fiber of the above 4) requires fiber processing.
In the method of forming a sheet by shaping a molding material containing polypropylene (A) and carbon fiber (B) in 5) above, the carbon fiber is shortened and the mechanical properties are inferior.
The method 6) is preferable because the anisotropy can be adjusted by stacking, and the characteristics suitable for the member can be easily adjusted. In this case, sheets manufactured by a plurality of different methods may be laminated.

  The ratio of the polypropylene (A) to the carbon fiber (B) is preferably composed of 35 to 75% by mass of the polypropylene (A) and 25 to 65% by mass of the carbon fiber (B), and (A) 45 to 55% by mass ( B) More preferably, it consists of 45 to 55% by mass. The more carbon fiber (B) can express the excellent mechanical properties of the carbon fiber, but if too much, the processability may be inferior.

The fiber length of the carbon fiber (B) is preferably 10 mm or more, more preferably 20 mm or more. The upper limit is not particularly limited and may be continuous fiber, but from the viewpoint of facilitating molding of a more complicated shape, discontinuous fiber is preferable, 50 mm or less is preferable, and 30 mm or less is more preferable.
The carbon fibers (B) are preferably aligned in one direction. By using the aligned ones, it is easy to demonstrate the excellent mechanical properties of carbon fibers.

  In the fiber-reinforced composite resin sheet of the present invention, it is preferable to laminate two or more layers containing polypropylene (A) and carbon fiber (B). By laminating two or more layers in different directions, it is possible to reduce the anisotropy of mechanical properties.

  The fiber-reinforced composite resin sheet of the present invention preferably has a thermal weight loss of 1% or less when heated at 300 ° C. for 1 hour in a nitrogen atmosphere, and more preferably 0.7% or less. When the thermal weight reduction is within this range, when the fiber reinforced composite resin sheet is preheated, volatile matter is hardly generated and molding defects are hardly generated. Here, the decrease in thermal weight when heated at 300 ° C. for 1 hour is measured by TG / DTA. Specific examples of the apparatus include TG / DTA6200 manufactured by SII Nano Technology. Measurement conditions are as follows: a nitrogen flow rate is set to 200 ml / min, an inert gas atmosphere is maintained, the temperature is raised from 40 ° C. to 300 ° C. at 20 ° C. per minute, and the weight change after holding at 300 ° C. for 1 hour is measured.

  The molded product of the present invention is obtained by press molding a fiber reinforced composite resin sheet. Examples of press molding include stamping molding and heating / cooling press. The stamping molding of the present invention is a method in which a fiber reinforced composite resin sheet is preheated to the melting point of polypropylene (A) or more and placed in a mold and press molded. The heating / cooling press is a method in which a fiber-reinforced composite resin sheet is placed in a mold, hot press molding is performed at or above the melting point of polypropylene (A), and cooling press molding is performed at or below the crystallization temperature. As preheating temperature or the temperature of a heating press, 180-320 degreeC is preferable and 230-280 degreeC is more preferable. The stamping molding mold temperature or cooling press temperature is preferably 40 to 150 ° C, more preferably 80 to 130 ° C. By being within this range, it is easy to obtain a good molded product.

The following examples further illustrate the present invention in detail.
The present invention is not limited to these examples.
The raw materials used in the following examples, the production method of the fiber-reinforced composite resin sheet, and the evaluation method are shown below.

<Raw material>
Acid-modified polypropylene (A-1-1)
Maleic anhydride modified polypropylene Yumex 1001 (acid modified amount 2.27%, weight average molecular weight 40,000) manufactured by Sanyo Chemical Industries, Ltd.
Acid-modified polypropylene (A-1-2)
Maleic anhydride-modified polypropylene Made by Mitsubishi Chemical Corporation Modic P958V (acid modification amount 0.14%)
Non-acid-modified polypropylene (A-2)
Novatec PP MA04A (MFR40g / 10min) manufactured by Nippon Polypro Co., Ltd.
Carbon fiber (B)
PAN-based carbon fiber by Mitsubishi Rayon Co., Ltd. PYROFIL TR50S15L AD, average single fiber fineness: 0.67Dtex, number of filaments: 15,000, strand strength: 500 kgf / mm @ 2, a strand elastic modulus: 24.5tonf / mm ^2, sizing agents :Epoxy resin)

<Evaluation method>
(1) Thermal weight reduction A 10 mg sample was cut out from the fiber reinforced composite resin sheet, and the temperature was increased at 20 ° C. per minute from 40 ° C. to 300 ° C. using a TG / DTA6200 manufactured by SII Nanotechnology. Then, the weight change after holding at 300 ° C. for 1 hour was measured.
(2) Flexural strength and flexural modulus Using a material cut into a length of 100 mm and a width of 25 mm in parallel with the fibers of the surface layer, the radius of the fulcrum is 2 mm, the radius of the indenter is 5 mm, the distance between the fulcrums is 80 mm, and the test speed is 5 mm per minute. A three-point bending test was conducted to measure bending strength and bending elastic modulus.
(3) Impact strength By conducting a Charpy impact test in accordance with JIS K7077 flat-wise using a material cut into a length of 80 mm and a width of 10 mm in parallel to the surface fibers, the impact strength in the 0 ° direction can be reduced. It was measured. Moreover, it implemented similarly using what was cut out by length 80mm and width 10mm in the orthogonal direction with the fiber of surface layer, and measured the impact strength of a 90 degree direction. The absolute value of the difference in impact strength between 0 ° and 90 ° was described as the difference in impact strength.
(4) Stamping Molding Appearance The surface of the stamping molding was visually observed and evaluated as x when white haze was generated and ◯ when it did not occur.

Example 1
1 part by mass of acid-modified polypropylene (A-1-1) and 95 parts by mass of non-acid-modified polypropylene (A-2) were put into a single screw extruder (product name: PMS30 manufactured by IKG Corporation). A resin film having a thickness of 40 μm was obtained. This resin film is laminated on both sides of the carbon fiber (B), which is aligned so that the fiber basis weight is 100 g / m 2 by the drum wind method, and is sandwiched between the light sides of the release paper CFP-45 manufactured by Lintec Corporation from both sides. Then, it was impregnated with a heating roll to obtain a unidirectional prepreg having a fiber content of 51% by mass.
A slit prepreg is made by cutting the unidirectional prepreg at an angle of 45 ° with the fiber axis so that the fiber length is 25 mm, and the fiber direction of the unidirectional prepreg is 0, 45, 90, -45, -45. , 90, 45, 0, 0, 45, 90, -45, -45, 90, 45, 220 ° C in a press mold having a 300 × 300 mm cavity with 16 layers stacked at 0 °. The mixture was hot-pressed at 0.3 MPa for 10 minutes and cooled and pressed at 30 ° C. and 1 MPa for 2 minutes to obtain a pseudo-isotropic fiber-reinforced composite resin sheet.
The fiber reinforced composite resin sheet was preheated with an IR heater set at 230 ° C. for 10 minutes, charged in a 310 × 310 mm flat plate mold set at 130 ° C., and stamped with a pressurizing force of 200 tons.

(Examples 2-3 and Comparative Example 1)
A fiber reinforced composite resin sheet was prepared and evaluated in the same manner as in Example 1 except that the blending of polypropylene (A) was changed as described in Table 1. The results are shown in Table 1.

The fiber-reinforced composite resin sheets of Examples 1 and 2 have a small difference in impact strength between 0 ° and 90 ° and a small anisotropy. In addition, since the thermal weight loss is small, the stamping molding appearance is excellent.
The fiber-reinforced composite resin sheet of Example 3 shows higher bending strength / flexural modulus than Comparative Example 1. In addition, since the thermal weight loss is small, the stamping molding appearance is excellent.
Since Comparative Example 1 is a fiber-reinforced composite resin sheet outside the scope of the present invention, the thermal weight loss is large and the stamping molding appearance is inferior.

<Discussion>
Since it is a fiber reinforced composite resin sheet having an excellent balance between mechanical properties and thermal stability, thermal decomposition hardly occurs during stamping molding, and good products can be obtained under a wide range of molding conditions. Furthermore, when there are few acid-modified polypropylene resins (A-1), a molded article with few anisotropy of mechanical characteristics, especially impact strength is obtained. As a result, the variation to be considered is reduced, and it is considered that a more reliable component design is possible.

Claims (7)

A fiber-reinforced composite resin sheet in which the matrix component is the following polypropylene (A) and the reinforcing fibers are carbon fibers (B).
Polypropylene (A): Acid-modified polypropylene (A-1) having an acid amount of 1.0 to 5.0%, 0.3 to 9.0% by mass, and acid-modified polypropylene (A-2) 91.0 The amount of acid is 0.006 to 0.2% in terms of maleic anhydride.   The fiber-reinforced composite resin sheet according to claim 1, comprising 35 to 75% by mass of polypropylene (A) and 25 to 65% by mass of carbon fiber (B).   The fiber reinforced composite resin sheet according to claim 1 or 2, wherein the fiber length of the carbon fiber (B) is 10 mm or more.   The fiber reinforced composite resin sheet according to any one of claims 1 to 3, wherein the carbon fibers (B) are carbon fibers aligned in one direction.   The fiber-reinforced composite resin sheet according to claim 1, wherein two or more layers containing polypropylene (A) and carbon fiber (B) are laminated.   The fiber-reinforced composite resin sheet according to claim 1, wherein the weight loss when heated at 300 ° C. for 1 hour in a nitrogen atmosphere is 1% or less.   A molded product obtained by press-molding the fiber-reinforced composite resin sheet according to claim 1.