JPH033566B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a tape-shaped prepreg in which a reinforcing fiber sheet is uniformly impregnated with a matrix resin. Tape-shaped prepregs made of reinforcing fiber sheets impregnated with resin are being used as materials for sports and leisure equipment such as golf club shafts and fishing rods, as well as structural materials for aerospace and vehicles. The performance required of a prepreg is that it has appropriate toughness, shape retention, drapability, and excellent workability and uniformity. Prepregs with excellent workability were developed by adjusting the blending ratio and viscosity of the matrix resin composition, and in the case of unidirectionally aligned prepregs, various measures were taken to eliminate non-bonding between adjacent fibers, such as openings. However, the reality is that a satisfactory prepreg with excellent uniformity, particularly uniformity of matrix resin distribution, has not yet been obtained. In prepreg, the uniformity of the matrix resin distribution, in other words, the uniformity of the fiber content, greatly affects the mechanical properties such as strength and modulus of elasticity as well as the dimensional accuracy of the molded product formed with the prepreg, so it is important to workability. These are the important quality characteristics of prepreg. Prepreg users do not place as much importance on this uniformity as they do on conventional workability.
This is thought to be partly due to the fact that inspection and evaluation are laborious and time-consuming, so they have to be avoided. In order to obtain a prepreg with excellent uniformity, first a reinforcing fiber sheet with a uniform basis weight is prepared, and then a matrix resin is impregnated with a uniform basis weight. There are two main methods for impregnating matrix resin: a method in which the resin is once dissolved in a solvent and impregnated into the reinforcing fiber sheet, and a method in which the resin is melted by heating and impregnated. The present invention relates to the latter prepreg manufacturing method, and aims to impregnate a matrix resin with a uniform basis weight. In the present invention, first, a matrix resin film with a uniform basis weight distribution is formed on a release paper, and then this is transferred and impregnated onto a unidirectionally aligned fiber bundle sheet or a woven sheet to have a uniform matrix resin basis weight. Manufacture prepreg. Therefore, the focus of the present invention is on how to form a resin film with a uniform basis weight distribution on a release paper. Traditionally, hot melt adhesives and resin films for prepregs have been manufactured by coating them on release paper using various roll coaters, doctor knife coaters, die coaters, fountain coaters, etc. No matter which coater is used, the resin used is quite viscous even under heating, and it is extremely difficult to apply it thinly and uniformly onto the release paper. For example, FIG. 1 is a schematic diagram showing a resin film coating process using a fountain coater. In the figure, 1 is a fountain coater, 2 is a back-up roll, 3 is a release paper, and 4 is a resin film coated on the release paper. Figure 2 shows the results of measuring the thickness in the width direction of the resin film coated on the release paper by the method shown in Figure 1, using the fountain coater shown in Figure 1. No matter how accurately the opening width of the lip portion is made uniform, it is impossible to prevent the occurrence of thickness unevenness in the width direction of the resulting resin film. Therefore, in order to prevent unevenness in the thickness of the film in the width direction, conventional methods have been used to improve the width accuracy of the die discharge section and improve the machining accuracy of the back-up roll surface. The occurrence of thickness unevenness in the width direction of the film has been significantly improved by improving the accuracy of the film, improving the temperature distribution of the resin discharge part of the die, and adjusting the die slit width using push-pull bolts installed in the die. Depending on the improved method, it is not possible to prevent the occurrence of film thickness unevenness as shown in a, b, c, and d of Figure 3, and it is practically impossible to suppress the film thickness unevenness to a range of 10μ or less. It has been said that it is impossible. Therefore, the present inventors conducted research to find a method for manufacturing a resin film that prevents the occurrence of film thickness unevenness, and found that even if the various improvement methods described above were applied to the molten resin coated area, the results shown in FIG. It has been found that unevenness in temperature distribution occurs, and unevenness in thickness occurs in the resulting resin film. Therefore, an attempt was made to prevent unevenness in the temperature distribution at the discharge area by installing several strip heaters in the die slit. However, as shown in Figure 2, this method did not reduce the unevenness in the thickness of the film in the width direction. The problem was not solved, and the result was that it took a lot of effort and had little effect. Therefore, the present inventors further investigated a method for eliminating thickness unevenness in the width direction of the resin film, and found that
Surprisingly, it was discovered that by preheating the release paper on which the molten resin is applied, the occurrence of thickness unevenness in the resin film obtained can be eliminated, and a resin film with thickness unevenness of less than 10 μm can be obtained. This makes it possible to manufacture prepregs with a uniform resin basis weight distribution. That is, the gist of the present invention is to prepare a prepreg by impregnating a reinforcing fiber sheet with a resin film coated with resin by heating the release paper when applying matrix resin to the release paper. FIG. 5 is a schematic diagram showing an example of the method for forming the resin film of the present invention using a fountain coater as the coater. In the figure, 5 is a heater for heating the release paper. Although the release paper can be heated uniformly, depending on the uneven thickness development pattern in the width direction of the resin film as shown in Fig. By heating the part of the release paper that is thicker than the other part of the release paper, it was possible to prevent uneven thickness of the resin film. As a method of heating the release paper, it is preferable to perform contact heating using plate heaters separated in the width direction, but a non-contact heating method using a dark infrared heater or the like may also be used. The heating section is preferably divided into three or more zones, although it depends on the characteristics of the coater used.
Further, although it is desirable that the temperature of each of the separated heating elements can be controlled independently, it is not necessary for adjacent heaters to be completely independent by using a heat insulating material or the like. According to the method of the present invention, in addition to the advantage of correcting the thickness unevenness of the resin film as described above, the effect of heating the release paper is to prevent the cooling of the resin during coating, resulting in a rapid increase in viscosity. Because there is almost no drop in the coating, it is possible to obtain a thinner coating film at the same resin temperature than without this method, and when applying a coating film of the same thickness, the resin temperature can be set lower. It is an ideal method for producing prepregs of thermosetting resins which are particularly susceptible to thermal hysteresis. Fortunately, the release paper commonly used for prepreg can withstand heating to temperatures close to 100°C for a short period of time without deteriorating, so the resin film coating method of the present invention was adopted. can. A resin film with little unevenness in thickness is formed on the release paper using the above-mentioned release paper heating method, and then a unidirectionally aligned or woven reinforcing fiber sheet is attached to this and heated nip roll or other impregnation method is used to heat the resin film. The prepreg is produced by transferring and impregnating the resin into fibers, but the resin film production process and the prepreg production process do not necessarily have to be continuous processes. EXAMPLES The present invention will be specifically explained below using examples. Example 1 Carbon fibers (12,000 fibers), 82 fibers with a width of 550 mm, were manufactured using a prepreg manufacturing equipment having a resin coating section of 510 mm in width and consisting of a fountain coater as shown in Fig. 6.
After producing a prepreg aligned in one direction on a release paper of 500 mm in width, the prepreg was divided into 8 parts in the width direction and the prepreg basis weight, resin content, fiber basis weight, and resin basis weight were measured and the results are shown in Table 1. It was shown to. The heating temperature of the heater is 60℃ at the center and 80℃ at both ends.
The average temperature was set at 70°C. The same table also shows the results when the same prepreg was manufactured without using a heater for the release paper. In Fig. 6, 1 is the aligned carbon fiber, 2 is the feed roll, 3 is the comb, 4 is the die, 5 is the back-up roll, 6 is the plate heater for heating the release paper, 7 is the release paper, and 8 is for impregnation. Preheating heater, 9
10 indicates a heating roll for impregnation, 10 indicates a release paper for protecting the roll, and 11 indicates a prepreg winding roll.

[Table] Example 2 Using a fountain coater as shown in Fig. 1, a resin film with a width of 510 mm was applied to a release paper of 550 mm in width in advance, and using this release paper, the resin film was applied to an impregnating device as shown in Fig. 7. Then, a 500 mm wide woven fabric (5 sheets and 8 pieces of satin) using carbon fiber (3000 pieces) was impregnated with resin, and after manufacturing the woven fabric prepreg, it was divided into 5 parts in the width direction, and the prepreg fabric weight, resin content, The fiber basis weight and resin basis weight were measured and the results are shown in Table 2. The heating temperature of the heater was set at 60°C at the center, 80°C at both ends, and 70°C on average. The same table also shows the case where a release paper coated with a resin film was used without using a heating plate heater. In Fig. 7, 1 is a woven fabric unwinding roll, 2 is a release paper coated with a resin film, 3 is a preheating plate heater for impregnation, 4 is a heating nip roll for impregnation, 5 is a release paper for protecting the roll, and 6 is a prepreg. A take-up roll is shown.

【table】 [Brief explanation of the drawing]

Figure 1 shows the coating process using a fountain coater, Figures 2 to 4 show the measurement results of the thickness in the width direction of the coated resin film, and Figure 5 shows the coating process when the present invention is implemented using a heating heater. Construction process, 6th to 7th
The figures represent prepreg manufacturing processes suitable for carrying out the invention.

Claims (1)

[Claims] 1 When applying matrix resin to release paper,
A prepreg manufacturing method characterized by impregnating a reinforcing fiber sheet with a resin film obtained by heating release paper and applying resin.