JP2003277525A - Polypropylene-based composite material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene-based composite material which reduces production time and production cost, and enables coating. <P>SOLUTION: The polypropylene-based composite material is a composite material of polypropylene and carbon fibers, and the polypropylene is modified with 1.0-15 wt.%, based on the entire amount of the polymer, unsaturated acid or its derivative, and the weight ratio of the polypropylene to the carbon fibers is in the range of 30:70 to 70:30, and the number average molecular weight of the polypropylene is in the range of 3,000-50,000. The carbon fibers are provided with sizing treatment to introduce functional groups on their surfaces. A molded product is obtained by filling a preform composed of the above carbon fibers in a specifically shaped mold, impregnating the preform with the above polypropylene, and then curing the polypropylene. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to polypropylene and carbon fiber (unidirectional fiber, woven fabric, or braided long fiber).
And a polypropylene-based composite material comprising

[0002]

2. Description of the Related Art Conventionally, composite materials such as carbon fiber reinforced epoxy resin and carbon fiber reinforced polyamide have been known in order to impart high rigidity to plastics.

Although the carbon fiber reinforced epoxy resin has high rigidity, it has a large specific gravity and is not very suitable for fields requiring lightness such as exterior panels of automobiles and aero parts. Further, since the epoxy resin is a thermosetting resin, it takes 2 hours or more to cure and the molding cycle becomes long, and the life of curability is limited to about 3 months even in a refrigerator. There are problems such as low storability.

Compared with the carbon fiber reinforced epoxy resin, polypropylene has a small specific gravity and also has bending resistance to withstand repeated bending in a portion such as a hinge. Therefore, exterior panels of automobiles, aero parts, etc. It is suitable as a material. Further, since the polypropylene is a thermoplastic resin, the molding time is as short as 10 minutes or less, there is no limit to the usable period, and there is no need to store it in the refrigerator.
It also has the advantage of being extremely excellent in storability.

On the other hand, the carbon fiber reinforced polypropylene has a problem that when the molten polypropylene is impregnated into the carbon fiber, the wettability between the polypropylene and the carbon fiber is low and pores are easily formed. In order to prevent the formation of the voids, it is necessary to finely pulverize polypropylene pellets to improve the wettability.

However, it takes a long time to finely pulverize polypropylene pellets, resulting in an increase in manufacturing cost.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polypropylene-based composite material which eliminates such inconveniences and has no voids, which can reduce the manufacturing time and the manufacturing cost.

[0008]

In order to achieve the above object, the polypropylene-based composite material of the present invention is a composite material comprising polypropylene and carbon fiber, and the polypropylene is 1.0 to 10% of the total amount of the polymer. It is characterized by being modified with 15% by weight of an unsaturated acid or a derivative thereof, and the weight ratio of the polypropylene to the carbon fiber is in the range of 30:70 to 70:30.

The polypropylene is modified with an unsaturated acid or a derivative thereof in an amount within the above range to introduce an oxygen bond into the surface of the polypropylene, which facilitates reaction at the oxygen bond portion. A suitable wettability can be obtained. Therefore, according to the polypropylene-based composite material of the present invention, there are no voids, and it is not necessary to pulverize the polypropylene at the stage of pelleting, and the manufacturing time and the manufacturing cost can be significantly reduced.

If the amount of the unsaturated acid or its derivative used for modifying the polypropylene is less than 1.0% by weight of the total polypropylene, the effect of improving the wettability with the carbon fiber cannot be obtained. On the other hand, when the amount of the unsaturated acid or its derivative exceeds 15% by weight, fluidity is increased and the polypropylene is hard to be held between the carbon fibers, and the polypropylene-based composite material cannot be obtained.

In the polypropylene-based composite material, if the polypropylene content exceeds 70 parts by weight and the carbon fiber content is less than 30 parts by weight, desired rigidity cannot be obtained. Further, when the content of the polypropylene is less than 30 parts by weight and the content of the carbon fibers exceeds 70 parts by weight, the function as a resin is impaired.

In the polypropylene-based composite material,
By sufficiently improving the wettability with polypropylene by surface-treating carbon fiber as described below, it is more expensive than unmodified polypropylene and has a low mechanical strength, and is of a polypropylene modified with an unsaturated acid or its derivative. In some cases, the object of the present invention can be achieved even when the amount is less than 30% by weight.

In the polypropylene-based composite material of the present invention, the polypropylene has a number average molecular weight of 3,000 to
It is characterized by being in the range of 50,000. The number average molecular weight of the polypropylene is related to the content of the unsaturated acid or its derivative, and when the content of the unsaturated acid or its derivative is less than 1.0% by weight, the number average molecular weight is 50,000.
And the content of the unsaturated acid or its derivative exceeds 15% by weight, the number average molecular weight becomes small. Further, if the number average molecular weight of the polypropylene is less than 3000, sufficient impact resistance may not be obtained in the polypropylene-based composite material, and if it exceeds 50,000, the fluidity becomes low and the carbon fiber becomes empty when impregnated. Holes are easily formed.

In the polypropylene-based composite material of the present invention, the carbon fiber is characterized by being subjected to a sizing treatment for introducing a functional group on the surface. Since the carbon fiber has been subjected to the sizing treatment, it is possible to obtain more suitable wettability with the polypropylene.

The polypropylene-based composite material of the present invention is obtained by filling a mold having a predetermined shape with a preform composed of the carbon fiber, impregnating the preform with the polypropylene, and then curing the polypropylene. It can be used as a molded body.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in more detail.

The polypropylene-based composite material of this embodiment contains 1.0 to 15% by weight, preferably 3 to 15% by weight of the total amount of the polymer.
It is modified with 12% by weight of an unsaturated acid or its derivative and has a number average molecular weight of 3,000 to 50,000, preferably 3,000.
20,000 polypropylene and carbon fiber 30:
It is mixed in a weight ratio in the range of 70 to 70:30.

Since the polypropylene is modified with the unsaturated acid or the derivative thereof in the amount in the above range, excellent wettability with the carbon fiber can be obtained.
The polypropylene may be obtained by any manufacturing method and is modified with an unsaturated acid or a derivative thereof in an amount in the above range, and only one polypropylene having a number average molecular weight in the above range is used. They may be used alone or in combination of two or more.

As the unsaturated acid or its derivative for modifying polypropylene, maleic acid, maleic anhydride,
Acrylic acid, or a low molecular weight compound containing a carboxylic acid group such as methacrylic acid, an unsaturated low molecular weight compound containing a sulfo group such as sulfonic acid, an unsaturated low molecular weight compound containing a phospho group such as phosphonic acid, or those The derivatives thereof can be mentioned. Among these, low molecular weight compounds containing a carboxylic acid group are preferable, and maleic acid, maleic anhydride, acrylic acid, methacrylic acid and the like are particularly preferable. As the acid used for modification, one of these may be selected and used, or two or more thereof may be selected and used in combination.

The carbon fiber may be of any type, but since it has a high strength, polyacrylonitrile (PAN) made from polyacrylonitrile is used as a raw material.
It is preferable to use carbon-based carbon fibers. Further, it is preferable that the carbon fiber is subjected to a sizing treatment so that a functional group such as a carboxyl group or a phenolic hydroxyl group is introduced on the surface thereof. The carbon fiber can obtain excellent wettability with the polypropylene by the sizing treatment.

The sizing treatment can also be carried out by treating the carbon fiber with a liquid modified polyolefin. Examples of the liquid modified polyolefin include a toluene solution of chlorine modified polypropylene, a toluene solution of maleic anhydride modified polypropylene, and a terminal modified hydrogenated polybutadiene. When the chlorine content of the chlorine-modified polypropylene exceeds 30% by weight, it is easily deteriorated by heat.
It is preferably in the range of% by weight. In addition, prior to the sizing treatment, the carbon fiber may have a carboxyl group or a hydroxyl group introduced on its surface by a known method such as an anodic oxidation method.

In the polypropylene-based composite material of the present embodiment, for example, a preform formed by aligning the carbon fibers in the length direction is filled in a mold of a predetermined shape, the mold is closed, and then the preform is melted. It can be used as a molded product obtained by impregnating the polypropylene in the state and curing the polypropylene.

In this embodiment, the polypropylene is
Since it is modified with the unsaturated acid or its derivative as described above, it is finely pulverized during the polymerization of propylene and can be easily impregnated into the preform of the carbon fiber even if it is not pulverized. However, the polypropylene is added in order to improve the impregnation further.
It is preferable that the powder is pulverized in advance and then melted.

When the polypropylene is pulverized beforehand, the maximum particle size is less than 200 μm, preferably 50 μm.
Less than The maximum particle size of polypropylene is 200μ
If it exceeds m, when impregnated into the carbon fiber preform, molten polypropylene may be clogged between the fibers to form pores.

The polypropylene-based composite material of this embodiment may contain a resin other than polypropylene within a range that does not significantly impair the effects of the polypropylene.
As the resin, for example, high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-α
Examples thereof include olefin copolymer rubber and styrene-butene copolymer rubber.

The polypropylene-based composite material of the present embodiment may use various additives generally used for olefin-based polymers, if necessary. Examples of the additive include a neutralizing agent, a weathering agent, an antioxidant, a heat stabilizer, an ultraviolet absorber, a flame retardant, a nucleating agent, a processability improving agent, a lubricant, an antistatic agent, and a pigment. .

Next, examples and comparative examples will be shown.

[0028]

Examples 1 to 4 First, polypropylene (trade name: J700G) manufactured by Idemitsu Petrochemical Co., Ltd. was mixed with maleic anhydride so as to be in the range of 1.0 to 15% by weight based on the total amount of the polymer. In addition, a known method (Japanese Patent Laid-Open No. 54-12
No. 4095), and four types of maleic anhydride-modified polypropylene were prepared.

The maleic anhydride content, resin fluidity and number average molecular weight of each maleic anhydride modified polypropylene are shown in Table 1.
Shown in. The fluidity of the resin is an index of the impregnability of the maleic anhydride-modified polypropylene into the carbon fibers.

When the maleic anhydride contained in the maleic anhydride-modified polypropylene exceeded 6.0% by weight, the resin fluidity was too large to be measured.

Next, a preform obtained by aligning long fibers of PAN-based carbon fiber (trade name: IM600) manufactured by Toho Tenax Co., Ltd. in the fiber direction is filled in a predetermined mold, and then the mold is closed to form the preform. Each of the above-mentioned maleic anhydride-modified polypropylenes in a molten state was impregnated. The weight ratio of the maleic anhydride-modified polypropylene to the carbon fiber was set to 40:60 in all cases.

Then, the maleic anhydride-modified polypropylene was cured at 200 ° C. to form four types of carbon fiber reinforced polypropylene moldings. Each molded product has a flat plate shape, 400 mm x 500 mm, and a thickness of 2 mm.
It has the size of.

Next, with respect to the obtained four types of molded articles,
The impregnating property of the maleic anhydride-modified polypropylene with respect to the carbon fiber was evaluated, and the specific gravity, elastic modulus, and coatability were measured. The results are also shown in Table 1.

The impregnating property was evaluated by observing the cross section of the molded body with eyes or with a microscope. The specific gravity was measured according to JIS K 7117, and the elastic modulus was measured according to JIS K 7073.

As for the coating property, after washing the flat plate-shaped molded body with pure water, Nippon Bee Chemical Co., Ltd. primer (trade name: RB109), Nippon Bee Chemical Co., Ltd. base coat (product name: R212S), Nippon Bee Chemical Co., Ltd. clear coat (trade name: R28)
The sample prepared by sequentially coating 8) and baking at 120 ° C. for 30 minutes was evaluated by conducting a cross-cut test 48 hours later. The result is the ratio of the number of grids (n) where the coating is not peeled off (n) to the total number of grids (100) (n /
100).

[0036]

[Comparative Example 1] Carbon fiber was used in the same manner as in the above-mentioned example except that an epoxy resin (trade name: EP828) manufactured by Japan Epoxy Resin Co., Ltd. was used in place of the maleic anhydride-modified polypropylene used in the above-mentioned example. A reinforced epoxy resin molding was formed.

Then, the obtained molded product was evaluated for the impregnating property of the epoxy resin with respect to the carbon fiber in exactly the same manner as in the above example, and the specific gravity, elastic modulus and coatability were measured. The results are shown in Table 1.

[0038]

Comparative Example 2 An attempt was made to form a carbon fiber reinforced polypropylene molded article in exactly the same manner as in the above Example except that the polypropylene used in the above Example was not modified at all. Since it was as low as (g / 10 minutes), the impregnation property with respect to the carbon fiber was poor and a molded product could not be obtained. The results are shown in Table 1.

[0039]

Comparative Example 3 A maleic anhydride-modified polypropylene was prepared by adding maleic anhydride to the polypropylene used in the above Example in an amount of 0.5% by weight based on the total amount of the polymer. A carbon fiber reinforced polypropylene molding was formed in exactly the same manner as in the above example.

Table 1 shows the maleic anhydride content, resin fluidity, and number average molecular weight of the maleic anhydride-modified polypropylene used in this comparative example.

Then, the obtained molded product was evaluated for the impregnating property of the epoxy resin with respect to the carbon fiber in exactly the same manner as in the above example, and the specific gravity, elastic modulus and coatability were measured. The results are also shown in Table 1.

[0042]

[Table 1]

From Table 1, the molded products of Examples 1 to 4 made of carbon fiber reinforced polypropylene have a practically sufficient elastic modulus, and are compared with the molded product of Comparative Example 1 made of carbon fiber reinforced epoxy resin. It is clear that the specific gravity is small and the paintability is excellent.

In addition, the molded products of Examples 1 to 4 were different from the molded products of Comparative Examples 2 and 3 in which the content of maleic anhydride was less than 1.0% by weight. It is clear that the carbon fiber has excellent impregnation property.

[0045]

[Example 5] The same procedure as in Example 3 except that the PAN-based carbon fibers used in Examples 1 to 4 were pre-sized with a modified polypropylene (trade name: Supercron 851L) manufactured by Nippon Paper Industries Co., Ltd. , A carbon fiber reinforced polypropylene molded body was formed. In Example 3 and this example, the maleic anhydride-modified polypropylene has the same maleic anhydride content of 6.0% by weight.

Then, the obtained molded body was evaluated for the impregnating ability of the maleic anhydride-modified polypropylene with respect to the carbon fiber in the same manner as in the above-mentioned Examples, and the specific gravity, elastic modulus and coatability were measured. The molded body of this example obtained by subjecting the carbon fiber to the sizing treatment has a higher impregnation property with respect to the carbon fiber of the maleic anhydride-modified polypropylene than the molded body of Example 3 not subjected to the sizing treatment. Was very good.

Table 2 shows the specific gravity, elastic modulus, coating property and impregnating property of the molded body of Example 3 and the molded body of this Example.

[0048]

[Table 2]

From Table 2, it can be seen that the molded body of this example obtained by subjecting the carbon fiber to the sizing treatment has substantially the same specific gravity and elastic modulus as those of the molded body of Example 3 not subjected to the sizing treatment. It is clear that it is also excellent in sex.

As described above, the polypropylene-based composite material of the present embodiment can reduce the manufacturing time and the manufacturing cost, has a practically sufficient elastic modulus, and has a small specific gravity so that it is lightweight and has good coating properties. Is also excellent. Therefore, the polypropylene-based composite material of the present embodiment is applied to two-wheeled vehicles, four-wheeled vehicles, especially sports cars, race cars, electric vehicles and other fenders, exterior panels such as door panels, wheel covers, tire covers, and other exterior panels, four-wheeled vehicles. It can be suitably used for aero parts such as front and rear wings and skirts.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29K 105: 06 B29C 67/14 P (72) Inventor Yoshihisa Saeki 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (reference) 4F072 AA04 AB22 AB28 AB30 AC05 AD04 AD53 AD54 4F205 AA11J AD02 AD16 AH17 HA19 HA22 HA44 HC17 HE21 HM01 4J002 BB211 DA016 GN00

Claims (4)

[Claims] 1. A composite material comprising polypropylene and carbon fiber, wherein the polypropylene is 1.0% of the total amount of the polymer.
Modified with an unsaturated acid or a derivative thereof in an amount of up to 15% by weight, and the weight ratio of the polypropylene to the carbon fiber is 30:
A polypropylene-based composite material, which is in the range of 70 to 70:30. 2. The polypropylene has a number average molecular weight of 3
The polypropylene-based composite material according to claim 1, which is in a range of 000 to 50,000. 3. The carbon fibers are unidirectional fibers, woven fabrics, or braided long fibers, which have been subjected to a sizing treatment for introducing a functional group on the surface.
Alternatively, the polypropylene-based composite material according to claim 2. 4. A molded article obtained by filling a mold having a predetermined shape with the carbon fiber preform, impregnating the preform with the polypropylene, and then curing the polypropylene. The polypropylene-based composite material according to any one of claims 1 to 3, which is characterized by the above-mentioned.