JP2002088656A - Carbon fiber bundle for molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon fiber bundle for molding, excellent in weaving performance and suitable for RIM molding. SOLUTION: This carbon fiber bundle for molding is characterized by being stuck with a water-soluble polyamide resin having 10-30 wt.% saturated water absorption and >=170% tensile elongation at break so as to satisfy the relationship: [saturated water absorption (wt.%)]×[add-on (wt.%)]<=40.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon fiber bundle excellent in weaving and suitable for RIM molding.

[0002]

2. Description of the Related Art Conventionally, reaction injection molding (hereinafter referred to as RIM molding) is known as a method for producing fiber reinforced plastics. Polyamide (nylon), epoxy, This is a molding method in which an unreacted raw material liquid of a matrix resin made of urethane or the like is injected, and a reaction is caused and solidified while impregnating the raw material liquid for fiber reinforcement in a mold. In RIM molding, polyurethane, polyurea, polyamide, epoxy, unsaturated polyester, dicyclopentadiene, etc. are used as matrix resin. Among them, RIM polyamide is formed by anionic polymerization of ε-caprolactam, Caprolactam and alkali metals,
An anion catalyst which is a reaction product with an alkaline earth metal, a Grignard reagent and the like is used.

In order to obtain a carbon fiber reinforced thermoplastic resin molded article obtained by RIM molding with high mechanical properties and efficiently, it is necessary to obtain a cloth in which a carbon fiber bundle having a large number of filaments is woven at a high density. It is important that the curing is not inhibited during the RIM molding process and that the step of removing moisture affecting the curing is omitted.

Further, in order to form a sizing agent having high spreadability and weaving property with a carbon fiber bundle having a large number of filaments, a small sizing agent having a soft property and having a high resin elongation requires a small amount of a sizing agent to be applied. Convergence cannot be maintained at the same time.

On the other hand, a sizing agent is usually attached to the surface of the reinforcing fiber. This sizing agent loosely bonds the fibers together, keeps the fibers from separating from each other, improves the processability, improves the wettability between the fibers and the matrix resin, and improves the adhesion at the interface. It has the effect of improving it. Sizing agents for carbon fibers used as reinforcing fibers for FRP include those based on a water-soluble epoxy resin and those based on a polyamide resin.

[0006] The epoxy group of the epoxy sizing agent reacts with the catalyst in the raw material of the RIM polyamide, resulting in a shortage of the catalyst required for polyamide polymerization and consequently deactivation. For this reason, curing of the resin is hindered, resulting in poor moldability and deterioration of physical properties.

The polyamide-based sizing agent does not deactivate the catalyst and is suitable for polyamide RIM molding. However, the sized carbon fiber has a hard yarn quality and deteriorates weaving properties.

For this reason, a method of sizing a carbon fiber using a water-soluble polyamide having a polyethylene oxide structure has conventionally been adopted, as disclosed in Japanese Patent Application Laid-Open No. 9-3777. However, there is a concern that the water absorption of the surfactant added at the same time affects the physical properties of the molded article.

[0009]

SUMMARY OF THE INVENTION In view of the background of the prior art, an object of the present invention is to provide a forming carbon fiber bundle which is excellent in weaving properties and is suitable for RIM molding.

[0010]

The present invention employs the following means in order to solve the above-mentioned problems. That is, in the carbon fiber bundle for molding of the present invention, the water-soluble polyamide resin having a saturated water absorption of not less than 10% by weight and not more than 30% by weight and a tensile elongation at break of not less than 170% is the saturated water absorption (weight%). ) And the amount of adhesion (% by weight) so as to satisfy 40 or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is directed to the above object, ie, a carbon fiber bundle excellent in weaving properties and suitable for RIM molding.
That is, the moisture affected by the curing agent, suitable for processing woven fabrics and the like used as a substrate, spreading property, paying attention to a carbon fiber bundle that satisfies a bundle property, and applying a specific polyamide resin to the surface of the carbon fiber bundle. Surprisingly, they found that they could solve such a problem at once.

The water-soluble polyamide resin used in the present invention satisfies all the conditions that the saturated water absorption is 10% by weight or more and 30% by weight or less, the glass transition temperature is 25 ° C., and the tensile elongation at break is 170%. A water-soluble polyamide resin is used. That is, an aqueous solution containing the specific water-soluble polyamide resin preferably in an amount of 0.1 to 5% by weight, more preferably 0.2 to 1% by weight, is used as a sizing agent, and adheres to the surface of the carbon fiber bundle. It is to be covered.

It is known that the cause of curing inhibition in the RIM molding process is greatly affected by moisture, and for that purpose, it is essential that the saturated water absorption is 10% by weight or more and 30% by weight or less. When the saturated water absorption is less than 10% by weight, the water solubility is low, the stability as a sizing agent is low, and when used in an aqueous solvent system, it is necessary to add a highly hydrophilic emulsifier, When such an emulsifier is added, the emulsifier absorbs R
This deactivates the curing agent during IM molding. When the saturated water absorption exceeds 30% by weight, the water solubility increases,
Although it is easy to use and process, the water-soluble polyamide resin film after adhesion over time absorbs and absorbs water,
As a result, the amount of water contained during M molding increases, and the curing agent during RIM molding is deactivated.

Here, the saturated water absorption is the ratio (%) of the saturated water absorption (weight) to the absolute dry weight at a temperature of 25 ° C. and a humidity of 65%.

The tensile elongation at break is defined as 50 mm long × 10 m wide × 150 μm thick formed by hot pressing.
m-250 μm film, test length 50 mm, tensile speed 2
The tensile elongation at break when a tensile test is performed at cm / min.

The carbon fiber bundle for molding of the present invention is formed by coating the surface thereof with the water-soluble polyamide resin. Such a water-soluble polyamide resin has a product of the saturated water absorption (% by weight) and the attached amount of 40 or less, preferably 2 or less.
It must be adhered so as to satisfy the condition of being 0 or less.

That is, if the saturated water absorption is less than 10% by weight, the stability as a sizing agent is inferior. If the saturated water absorption exceeds 30% by weight, the water absorption over time increases, and water absorption proceeds during processing. As a result, curing may be insufficient, and a stable molded product may not be obtained.
On the other hand, when the product of the saturated water absorption (% by weight) and the amount of adhesion exceeds 40, the water absorption of the sizing agent increases, and the curing may be insufficient. Note that the lower limit of this product is preferably 2, and more preferably 3, from the viewpoint of the sizing property and the stability of the sizing agent.

Further, the carbon fibers used in RIM molding are fragile, so that they must be handled in bundles with high convergence, and it is practically important to have flexibility. To obtain a sizing agent having high spreading property and weaving property with a carbon fiber bundle having a large number of filaments, a glass transition temperature ≦ 2
If it has a soft property of 5 ° C. and does not have a high resin elongation, it is not possible to simultaneously maintain sufficient convergence with a small amount of sizing agent.

In order to maintain the convergence of the carbon fiber bundle and to improve the weaving property, a water-soluble polyamide resin is preferred.
Here, the water-soluble polyamide resin refers to a polyamide resin such as nylon 6, nylon 6,6 or the like, which is insoluble in water, while imparting a hydrophilic chemical structure or using an emulsifier, A polyamide resin that is soluble in water.

When the glass transition temperature exceeds 25 ° C., the yarn bundle becomes hard, and the workability such as weaving property and spreading property deteriorates.
If the resin elongation is less than 170%, the sizing property is insufficient, and as a result, the amount of the sizing agent, that is, the water-soluble polyamide resin, increases, and the processability such as the weaving property and the spreading property decreases, In addition, the curing agent during RIM molding may be deactivated. The lower limit of the glass transition temperature is preferably selected from those having a glass transition temperature of preferably -80 ° C, more preferably -55 ° C, because they are not too soft and have excellent convergence.

Further, in the present invention, it has been found that there is a correlation between the tensile elongation at break and the convergence of the water-soluble polyamide resin. That is, it is necessary that the water-soluble polyamide resin has a tensile elongation at break of 170% or more. That is, if the tensile elongation at break is less than 170%, the convergence is insufficient, the filament is liable to be wound around a roller or the like at the time of processing, and a process trouble or poor quality is likely to occur. In order to improve such a problem, a large amount of carbon fiber must be adhered, and as a result, a hard carbon fiber bundle or a material having insufficient spreadability is provided, which is not preferable. The upper limit of the tensile elongation at break of such a water-soluble polyamide resin is preferably 1000%, more preferably 700%, from the viewpoint of convergence.

The sizing agent which is an aqueous solution of the water-soluble polyamide resin of the present invention is preferably used alone, and such a sizing agent is sized by a usual method such as a dip method, a spray method or a roller method. The sized carbon fiber bundle is dried in a hot air drying furnace at 100 to 250 ° C. At this time, the adhesion rate (% by weight) of the water-soluble polyamide resin is calculated from the relational expression that the product of the saturated water absorption (% by weight) and the amount of adhesion is 40 or less.
It is sufficient if the value is equal to or less than the value obtained by dividing 40 by the saturated water absorption, but it is generally controlled to a small range of about 0.1 to 1% by weight. Preferred from above.

The carbon fiber bundle for molding with a water-soluble polyamide resin is preferably a carbon fiber bundle having a large number of filaments in order to enhance the characteristics of a molded product obtained by RIM molding. It is preferable that the number of filaments is 15,000 or more, more preferably 45,000 or more. The upper limit of the number of filaments is preferably at most 100,000, and more preferably 70,000 or less, from the viewpoint of spreadability.

The carbon fiber bundle for molding of the present invention has the above-mentioned RI
Without being limited to the M molding, for example, the molding carbon fiber bundle may be cut into fibers, mixed with a molding resin, and then put into a mold for molding. In such a case, a cut fiber of 3 to 20 mm is preferably used.

[0025]

The present invention will be described in more detail with reference to the following examples. 1) Evaluation of characteristics of sizing agent resin a) Evaluation of tensile elongation at break A film having a thickness of 150 to 250 µm was prepared by hot pressing (press temperature: 250 ° C).

Measurement: Measured with a test length of 50 mm, using Tensilon manufactured by Toyo Baldwin.

B) Evaluation of saturated water absorption About 10 g of the resin shown in Table 1 was dried at 80 ° C. under reduced pressure for 12 hours, weighed accurately (weight A), and then dried at a temperature of 26.
The resin was allowed to stand under a condition of a temperature of 65 ° C. and a humidity of 65% until the weight became constant. The weight increase (weight B) of the resin at that time was precisely weighed and calculated by the following equation.

Saturated water absorption (%) = 100 × weight B / weight A 2) Evaluation of RIM polymerization Under a nitrogen atmosphere, ε-caprolactam (15 g) and dicyclohexylcarbodiimide (0.55 g) were put into a test tube, and 1) described above. 3 g of the carbon fiber bundle obtained in the above was added. (Test tube A) Under a nitrogen atmosphere, ε-caprolactam (15 g) and sodium hydride (0.07 g) were added to another test tube. (Test tube B) Heat test tubes A and B in an oil bath at 200 ° C for 20 minutes to melt ε-caprolactam, mix the contents of test tubes A and B, and polymerize at 150 ° C. Was done. The inhibition of the polymerization reaction was evaluated by evaluating how long the curing time was longer than the curing time in a system to which a carbon fiber bundle having no coating was added. That is, with respect to the curing time when using a carbon fiber bundle to which nothing is applied, the curing time is less than 1.1 times, ○, the curing time is 1.1 to 1.5 times, Δ,
When the curing time was 1.5 times or more, it was judged as x. 3) Evaluation of Spreadability One meter of the carbon fiber bundle is taken, and a 100 g weight is hung on one end. A portion of 50 cm from the end of the carbon fiber bundle is placed on a curved surface of a 4.5 cm diameter cylindrical iron bar placed horizontally with the ground so that the fiber direction is perpendicular to the cylindrical iron bar.

Both ends of the carbon fiber bundle hang down perpendicularly to the ground via a cylindrical iron bar. From this state, the end opposite to the one where the weight is hung is 20 cm vertically downward.
Pull down, then pull up vertically 40 cm.

After repeating this operation 10 times, the width of a portion 50 cm from the end of the carbon fiber bundle is measured.

The evaluation was made in terms of the ratio to the spread width when using a carbon fiber bundle having no coating. That is, when the spread width is less than 1.1 times the spread width when using the carbon fiber bundle to which nothing is applied, 、, 1.1 to 1.5
It was determined as Δ when the width was doubled, and × when the width was 1.5 times or more. Example 1 A water-soluble polyamide resin [water-soluble polyamide P-70 manufactured by Toray Industries, Inc.] was applied to carbon fibers having 70,000 filaments.
Of 0.5% by weight as a sizing agent,
After drying at 70 ° C., a molding carbon fiber bundle having an adhesion amount of the water-soluble polyamide resin of 0.2% by weight was obtained. Saturated water absorption (% by weight) of the carbon fiber bundle for molding and the attached amount (% by weight)
Was 3.2.

The evaluation results are shown in Table 1. Comparative Example 1 In Example 1, the amount of the sizing agent was 3% by weight.
A molding carbon fiber bundle was obtained in the same manner as in Example 1 except that the above procedure was adopted. The product of the saturated water absorption (% by weight) of the carbon fiber bundle for molding and the attached amount (% by weight) was 48.

Table 1 shows the evaluation results. Example 2 A molding carbon fiber bundle was obtained in the same manner as in Example 1, except that the water-soluble polyamide resin was changed to [Water-soluble polyamide A-90 manufactured by Toray Industries, Inc.]. The product of the saturated water absorption (% by weight) and the attached amount (% by weight) of the carbon fiber bundle for molding was 5.2.

Table 1 shows the evaluation results. Comparative Example 2 A water-soluble polyamide resin was used as an alcohol-soluble polyamide resin [Alcohol-soluble polyamide CM4 manufactured by Toray Industries, Inc.
000] to obtain a molding carbon fiber bundle in the same manner as in Example 1. The saturated water absorption of this alcohol-soluble polyamide resin was 2% by weight.

Table 1 shows the evaluation results.

[0036]

[Table 1]

As is evident from Table 1, in Examples 1 and 2, carbon fiber bundles having no polymerization inhibition, good spreadability and good weaving properties were obtained.

On the other hand, in Comparative Example 1 in which the amount of adhesion was increased,
Spreadability deteriorated, and even in Comparative Example 2 using a resin having a high glass transition temperature, spreadability deteriorated.

[0039]

According to the present invention, it is possible to stably provide a carbon fiber bundle for molding excellent in weaving property and suitable for RIM molding.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F206 AA29C AD16 JA01 JB11 JL02 4L033 AA09 AB01 AC12 CA55

Claims (3)

[Claims] 1. A water-soluble polyamide resin having a saturated water absorption of not less than 10% by weight and not more than 30% by weight and a tensile elongation at break of not less than 170%, has a saturated water absorption (% by weight) and an attached amount (% by weight). The carbon fiber bundle for molding, characterized in that the carbon fiber bundle is adhered so as to satisfy a product of 40 or less. 2. A polyamide resin having a glass transition temperature of 25.
The carbon fiber bundle for molding according to claim 1, wherein the temperature is lower than or equal to ° C. 3. The molding carbon fiber bundle according to claim 1, wherein the carbon fiber bundle is constituted by a number of filaments of 150,000 or more.