JPH03207472A - Method for coating resin on mold release sheet - Google Patents

Abstract

PURPOSE:To make molten resin so as to be easily bonded to a mold release sheet and to smooth fluidization of molten resin by positively heating the mold release sheet until it reaches the position wherein coating of molten resin is performed by an applicator roll and holding the viscosity of molten resin at a time of transfer on the mold release sheet in a range within 10-10000 poise. CONSTITUTION:A mold release sheet 43 is moved on a coating roll 44 together with the surface thereof. An applicator roll 45 is opposed and arranged parallel to this coating roll 44 and rotated to the direction reverse to the coating roll 44. The molten resin 46 supplied on the applicator roll 45 is transferred on the mold release sheet 43 to coat it therewith. In this case, the mold release sheet 43 is positively heated by a heating roll 56 until it reaches the position wherein coating of molten resin is performed by the applicator roll 45. Thereby the viscosity of molten resin at a time of transfer on the mold release sheet 43 is held in a range within 10-10000 poise.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a method for coating a release sheet with a resin, and particularly to a method for producing a resin-supported release sheet used in the production of prepreg for fiber-reinforced composite materials. Relating to a coating method.

[Conventional technology] Sheet-like prepregs used for the preparation of fiber-reinforced composite materials have conventionally carried resin (for example, B-stage thermosetting resin) on at least one side, as shown in Fig. 2. Reinforcing fibers 2 arranged in a sheet form are sandwiched between two release sheets 1 and 3, and a press roll 4 is used, for example.
A method of applying pressure and heating to transfer and impregnate the reinforcing fibers 2 with resin to produce the prepreg 5, and then peeling off one release sheet 3 and winding the prepreg 5 together with the other release sheet 1 into a roll. Manufactured by. When the prepreg manufactured by such a method is used, a release sheet is peeled off from one side thereof, a plurality of prepregs are laminated in the same direction or in different directions as necessary, and the prepreg is used to form a fiber-reinforced composite material.

In contrast to the conventional general prepreg produced by the method described above, the present applicant has recently developed a method in which reinforcing fibers 11 made of long fibers are supported on a release sheet 12, as shown in FIGS. 3 and 4. A primary prepreg 14 is created by transferring and impregnating the resin 13, and fine particles 1 made of the resin 13 and another resin are coated on both or one side of the primary prepreg 14.
A new prepreg has been developed in which secondary prepreg 17 is obtained by transferring or moderately impregnating a mixture 16 with 5 (
(Japanese Unexamined Patent Publication No. 64-26651). According to this prepreg, when made into a fiber-reinforced composite material while ensuring the excellent adhesiveness and flexibility of the prepreg, it can exhibit high strength not only in the fiber axis direction of the reinforced fibers, but also in the interlayer strength and interlaminar toughness. It is possible to significantly improve the impact resistance, etc. of composite materials.

Release sheets 12 and 18 carrying resin are also used in the production of prepreg in which this resin is transferred and impregnated in two stages, but in particular, resin 16 for preparing the secondary prepreg is made of resin. Since it is preferable to maintain the fine particles 15 in a desired state of decomposition in order to obtain the above-mentioned excellent prepreg properties, the resin 13 is required to have a higher viscosity than the resins conventionally used. It became so.

[Problem to be solved by the invention@] As described above, a resin-supported release sheet is used in the production of Buri Preg, but the resin-supported release sheet is coated with a coater using a reverse-hole method as shown in Fig. 5, for example. It has been found that the following problems occur when attempting to manufacture using .

In FIG. 5, the release sheet 31 is fed over the surface of the coating roll 32 as the coating roll 32 rotates, and the molten resin 34 supplied from the melting roll 35 is running onto the opposing applicator roll 33. The coating is continuously applied onto the surface of the release sheet 31.

The applicator roll 33 is heated to the melting temperature of the resin. Further, since it is necessary to make the resin coating thickness uniform, the roll is constructed as a metal roll with a smooth surface. On the other hand, the coating roll 32 is pressed against the applicator roll 33 via the release sheet 31 so that the molten resin 34 on the applicator roll 33 is transferred onto the release sheet 31. In order to prevent uneven force, it is constructed as a roll coated with an elastic material, such as rubber, and active heating is not performed to protect the coating.

Now, the applicator roll 33 is the coating roll 3.
2, the molten resin 34 on the applicator roll 33 is rotated in the opposite direction to the release sheet 31 at a position where the release sheet 31 leaves the coating roll 32 or a position near the position.
It is transferred and coated on the surface of
As mentioned above, the coating roll 32 is not actively heated, so the release sheet 31 fed over its surface is at almost the same temperature as the coating roll 32, and the molten resin 34 is transferred to the release sheet 31. It will be cooled at the transition point. Therefore, when the molten resin 34 has a high viscosity, it is difficult for the molten resin 34 to be smoothly transferred to the release sheet 31 compared to a molten resin with a relatively low viscosity, and random coating unevenness may occur or the transfer may be difficult. The resulting shearing force becomes large and stick-slip occurs at the coating point, which causes a problem in that it causes coating unevenness that extends in the width direction of the sheet.

An object of the present invention is to suppress the occurrence of coating unevenness, particularly when the coating resin has a high viscosity, in coating a release sheet with a molten resin using a reverse roll type coater.

[Means for Solving the Problems] The resin coating method for a release sheet of the present invention in accordance with this objective includes a method for coating a release sheet with a resin that moves on a coating roll along with the surface of the coating roll, and is arranged opposite to the coating roll in parallel with the release sheet. When transferring and coating the molten resin supplied onto the applicator roll rotating in the opposite direction to the coating roll, the release sheet is actively moved until it reaches the molten resin coating position by the applicator roll. The viscosity of the molten resin at the time of transfer to the release sheet is 10 to 10.
It consists of a method of keeping it within the range of iooo poise.

The coater used in the method of the present invention is the so-called reverse roll type coater described above, in which the release sheet is wound around the coating roll, and as the coating roll rotates, the release sheet is continuously rolled along with the coating roll surface. The molten resin is supplied onto an applicator roll which is placed parallel to the coating roll and rotates in the opposite direction to the coating roll, and the molten resin is transferred onto the surface of the release sheet for coating. be. The type of coater is not particularly limited as long as it is of a reverse roll type.

The release sheet used in the present invention is release paper, for example, with a thickness of 0. 05~0.2m kraft paper, roll paper,
A coating layer of a filler such as clay, starch, polyethylene, or polyvinyl alcohol is provided on both sides of paper such as glassine paper, and a silicone or non-silicone mold release agent, preferably polyester, is applied on each coating layer. It is as if a mold release agent made of condensation reaction type silicone or addition reaction type silicone of dimethylsiloxane and polydimethylhydrodiene siloxane was applied. A synthetic resin film imparted with mold releasability by corona discharge treatment or the like or a synthetic resin film coated with a mold release agent can also be used (for example, polyethylene film, polypropylene film, etc.).

The present invention is effective when the resin to be coated is a relatively high viscosity resin, but it is of course possible to apply the present invention even to a low viscosity resin, and it is possible to further suppress coating unevenness and coat the resin. Effects such as improved thickness control accuracy can be obtained.

When the resin-supported release sheet obtained in the present invention is used for preparing prepregs, the high-viscosity coating resin is particularly transferred to and impregnated into reinforcing fibers in two or more stages. If required. In other words,
As mentioned above, the reinforcing fibers are transferred and impregnated with resin to produce a primary prepreg, and this primary prepreg is coated with a resin consisting of a mixture of resin and fine particles made of another resin different from the resin. By creating a secondary prepreg through transfer and impregnation, it has excellent adhesive properties as a prepreg.
A prepreg that can exhibit excellent interlaminar strength and interlaminar toughness when made into a composite material while ensuring flexibility can be obtained, but it is difficult to maintain the fine particles in a desired dispersed state in a resin-supported state on a release sheet. Therefore, the resin mixed with the fine particles is required to have a viscosity above a certain level. The resin mixed with these fine particles is also the resin for making the primary prepreg in the preparation of the above-mentioned prepreg, so in the production of the above-mentioned prepreg, the resin-supported release sheet for making the primary prepreg is also a high-viscosity resin. Must be coated with molten resin.

The resin coated on the release sheet used for preparing the prepreg mentioned above includes thermosetting resin,
Examples include resins that are a mixture of thermosetting resins and thermoplastic resins. Preferred thermosetting resins include epoxy resins, maleimide resins, polyimide resins, resins with acetylene ends, resins with gonyl ends, resins with allyl ends, resins with nadic acid ends, and resins with cyanate ester ends. Resin can be given. These can generally be used in combination with a curing agent or a curing catalyst. Moreover, it is also possible to use a mixture of these thermosetting resins as appropriate.

Furthermore, epoxy resin is used as a thermosetting resin suitable for preparing prepreg. Particularly preferred are epoxy resins whose precursors are amines, phenols, and compounds having carbon-carbon double bonds. Specifically, as an epoxy resin using amines as a precursor, tetraglycidyldiaminodiphenylmethane, triglycidyl-p-aminophenol, triglycidyl-p-aminophenol, various isomers of triglycidylaminofresol, and phenols are used as precursors. As the epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, epoxy using a compound having a carbon-carbon double bond as a precursor Examples of the resin include alicyclic epoxy resin, etc.
It is not limited to this. Brominated epoxy resins obtained by brominating these epoxy resins may also be used. Epoxy resins whose precursors are aromatic amines such as tetraglycidyldiaminodiphenylmethane have good heat resistance and good adhesion to reinforced 18M, and are therefore most suitable for the prepreg production as described above. These epoxy resins are preferably used in combination with an epoxy curing agent. Any compound having an active group capable of reacting with an epoxy group can be used as the epoxy curing agent.

In general, it is also suitable to mix and use a thermoplastic resin with the above-mentioned thermosetting resin. The thermoplastic resin to be mixed is
Thermoplastic with a bond selected from carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, monoponate bonds, urethane bonds, urea bonds, thioether bonds, sulfone bonds, imidazole bonds, and carbonyl bonds in the main chain. Resin, more preferably polyacrylate, polyamide, polyaramid, polyester,
Polycarbonate, polyphenylene sulfide, polybenzimidazole, polyimide, polytechtelimide,
A group of thermoplastic resins that belong to engineering plastics, such as polysulfone, polyethersulfone, and polyetheretherketone. In particular, polyimide,
Polyether imide, boris sulfone, polyether sulfone, and polyether ether ketone have excellent heat resistance and are therefore ideal as a part of the resin.

As the fine particles to be mixed with the resin, a thermosetting resin, a thermoplastic resin, and a mixed resin of both can be used.

Preferred thermosetting resins used as fine particles include epoxy resins, phenolic resins, unsaturated polyester resins, amino resins, allyl resins, silicone resins, urethane resins, maleimide resins, polyimide resins, resins with acetylene ends, and resins with vinyl ends. Examples include resins, resins having allyl ends, resins having nadic acid ends, and resins having cyanate ester ends. Examples of thermosetting resin fine particles that are commercially available include epoxy resin ``Trepearl'' EP-B manufactured by Toray Industries, Ltd., and phenol resin ``'Belpearl'' R-800 manufactured by Kanebo Corporation. Even if it is not available as a product, it is possible to make it into fine particles by crushing the above resin, and by further classifying it, it is possible to use only those within the desired particle size range.

Thermoplastic resin can also be used as the fine particles. Suitable thermoplastic resins include carbon-carbon bonds, amide bonds, imide bonds, ester bonds, ether bonds, carbonate bonds, urethane bonds, urea bonds, thioether bonds, sulfone bonds, imidazole bonds, and carbonyl bonds in the main chain. It is a thermoplastic resin with a bond that
Those having a partially crosslinked structure within the molecule may also be used. Specifically, polyacrylate, polyvinyl acetate,
Vinyl resins represented by polystyrene, polyamide, polyaramid, polyester, polyacetal, polycarbonate, polyphenylene oxide, polyphenylene sulfide, polyarylate, polybenzimidazole, polyimide, polyamideimide, polyetherimide, polysulfone, polyether Examples include thermoplastic resins belonging to engineering plastics such as sulfone and polyetheretherketone, hydrocarbon resins represented by polyethylene and polypropylene, and cellulose derivatives represented by cellulose acetate and cellulose butyrate. In particular, polyamide, polycarbonate, polyacetal, polyphenylene oxide, polyphenylene sulfide, polyarylate, polyester, polyamideimide, polyimide, polyetherimide, polysulfone, polyethersulfone, polyetheretherketone, polyaramid, polybenzimidazole It has excellent impact resistance, making it suitable as a material for fine particles. Among these, polyamide has particularly excellent toughness, and by using a polyamide that belongs to the amorphous transparent nylon category, it can also have heat resistance.

Commercially available thermoplastic resin particles include:
For example, nylon 12 fine particles SP-500 manufactured by Toray ■,
Examples include acrylic fine particles MP7-1000 manufactured by Nippon Synthetic Rubber. In addition, even if fine particles cannot be obtained as a commercial product, it is possible to make them into fine particles by crushing the above resin, and by rough classification, only particles within the desired particle size range can be used. be able to.

It is also suitable to use a mixture of a thermosetting resin and a thermoplastic resin as the fine particles. Suitable thermosetting resins and thermoplastic resins in this case are the same as those mentioned above. For example, if a mixture of a phenol resin and a nylon resin is used, the water absorption rate of the nylon resin is lowered and the glass point transition temperature is increased while maintaining the toughness of the nylon resin, resulting in a particle component with excellent heat and water resistance.

The resin or the mixed resin of the resin and fine particles as described above is supplied onto the applicator roll as a relatively high viscosity molten resin, and the surface of the release sheet is conveyed from the applicator roll onto the coating roll. It is transferred onto the mold release sheet and coated on it. During this coating, the release sheet is actively heated before reaching the molten resin coating position by the applicator roll, and the molten resin is prevented from cooling at the point of transition to the release sheet, causing the transfer. The viscosity of the molten resin at
It is kept in the range of 0 to 10,000 voices.

Here, if the viscosity is less than 10 poise, the fluidity of the resin is too high, resulting in uneven coating weight, and on the other hand, if it exceeds 10,000 poise, the transferability rapidly decreases, resulting in uneven coating. The preferred viscosity range is 100-
It is 10,000 poise.

The release sheet can be heated by heating the coating roll and heating the release sheet via the coating roll, or by heating the release sheet from above the coating roll or in front of the coating roll using a non-contact heating means. Alternatively, a method in which another heating roll is placed before the coating roll and the release sheet is heated by the heating roll, or a combination of these methods can be applied. Note that the applicator roll can be heated and controlled in order to move the supplied molten resin to the coating position while maintaining the molten state.

If the release sheet is preheated to the coating position in this way and the viscosity of the molten resin coated on the release sheet is maintained at 10 to 10,000 poise at the time of transfer, the resin will become very sticky. The flow for transfer onto the release sheet surface during coating is extremely stable. In addition, since the sudden increase in viscosity due to the temperature drop of the molten resin at or near the contact surface of the molten resin at the moment when the molten resin contacts the release sheet is suppressed, the shearing force acting on the coating point is relatively reduced. kept small,
The occurrence of stick-slip phenomenon is suppressed. As a result, even if the molten resin has a high viscosity, it is smoothly transferred from the applicator roll surface to the release sheet surface without fluctuation, and coating unevenness is prevented from occurring.

In addition, in order to further ensure the smooth transfer of the molten resin onto the release sheet as described above, it is also effective to use the following methods in combination.

In the process of supplying molten resin onto the applicator roll, the thickness (supply amount) of the molten resin on the applicator roll is usually suppressed, and the molten resin is evenly coated onto the release sheet at the target thickness. The mold is transferred onto the release sheet.

At the coating position, the release sheet is nipped between an applicator roll and a coating roll that rotate in opposite directions, and the molten resin on the surface of the applicator roll is peeled off and coated onto the surface of the release sheet. .

Therefore, in order to accurately and uniformly coat the release sheet with the target resin thickness, substantially all of the molten resin on the applicator roll must be smoothly peeled off and transferred onto the release sheet. It is preferable. To accomplish this, it is preferred to increase the nip pressure (linear pressure) of the coating roll against the applicator roll and to ensure that the linear pressure is applied substantially uniformly. By using such a nip pressure increase in combination, the occurrence of coating unevenness in high viscosity resin coating can be more reliably prevented.

[Embodiments] Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a diagram for carrying out a method according to an embodiment of the present invention.
4 shows a reverse roll type coater 40.

The release sheet 4 is released from the roll 42 set on the unwinding machine 41.
3 is unwound, and one surface of the release sheet 43 is coated with a coating molten resin 46 that is continuously supplied via an applicator roll 45 onto a coating roll 44 . Whether or not a predetermined coating thickness has been achieved can be determined by checking the release sheet 43 using, for example, a β-line grating meter 47.
The thickness of the single piece and the resin-coated release sheet 60 is checked by measuring the thickness, and the resin-supported release sheet 60 is wound onto a roll 48. This roll 48 is subjected to the prepreg production process described above.

The coating resin 46 is produced by melting a resin block 49 with a heating roll 50 as a melt and guiding (dropping) the molten resin onto the applicator roll 45 to reduce the clearance between the applicator roll 45 and the metal ring roll 51. By adjusting the circumferential speed, temperature, etc. of both rolls, the amount of molten resin supplied and the thickness of the molten resin on the applicator roll 45 are controlled, and the release sheet 4 is applied from above the applicator roll 45.
3. Supply and coating by transferring on top. The heating roll 50, the applicator roll 45, the metering roll 51, and the coating roll 44 are heated and controlled by internal heaters 52, 53, 54, and 55 or a heating medium, respectively.

By heating the coating roll 45 by the heater 55, the release sheet 43 is heated while being conveyed on the coating roll 45 before reaching the coating position. In this embodiment, furthermore, the coating roll 45
The guide roll 56 located upstream of the release sheet 43 is also heated by a heater 57, and the release sheet 43 is effectively heated to a predetermined temperature from both sides by the coating roll 45 and the heating roll 56. Furthermore, if necessary, a non-contact heater 58 may be disposed at an appropriate position to promote heating of the release sheet 43, as shown by the two-dot chain line.

By such heating means 45, 56 and 58, the release sheet 43 is heated until it reaches the coating point 59.
It is actively heated to a predetermined temperature. The heated mold release sheet 43 is coated with the molten resin 46 at the coating point, but since the temperature of the mold release sheet 43 is high, the temperature of the molten resin 46 does not decrease even when it comes into contact with the mold release sheet 43. The viscosity at the time of transition is 10~
The pressure is maintained at 10,000 poise, so that it adheres well to the surface of the release sheet 43 and transfers, and the shearing force generated during coating is kept small, preventing irregular flow and preventing coating unevenness.

The release sheet 43 coated with the molten resin 46 uniformly and precisely to a predetermined thickness is wound up as a resin-supported release sheet as a roll 48 and used for manufacturing prepreg. Since there is no coating unevenness on the resin-supported release sheet, the resin supported on the release sheet is uniformly and evenly impregnated into the reinforcing fibers during the prepreg production process, resulting in a prepreg with uniform physical properties.

[Effects of the Invention] As explained above, when using the resin coating method for a release sheet of the present invention, the release sheet is actively heated up to the molten resin coating position, and the molten resin coats the release sheet. Since the temperature drop during coating is kept extremely small and the viscosity at the time of transition is maintained at 10 to 1000 poise, the molten resin easily adheres to the release sheet and the flow of the molten resin during coating is reduced. The coating becomes extremely smooth, and even when using a high viscosity resin, a resin-supported release sheet with a predetermined coating thickness and no uneven coating can be easily obtained. By using this resin-supported release sheet for prepreg production, a prepreg with uniform physical properties without resin transfer or uneven impregnation can be obtained.

[Brief explanation of drawings]

FIG. 1 is a side view of a coater for carrying out a method according to an embodiment of the present invention; FIG. 2 is a schematic side view of a prepreg manufacturing apparatus showing an example of a prepreg manufacturing process using a resin-supported release sheet; Figures 3 and 4 are cross-sectional views showing the state of resin inclusion, showing an example of another prepreg manufacturing process using a resin-supported release sheet. Figure 5 is a partial side view of a conventional reverse roll type coater. , is. 40... Coater 41... Unwinder 43... Release sheet 44... Coating roll 45... Applicator roll 46... ... Molten resin for coating 47 ...
... Meter 49 ... Resin block 50 ... Heating roll 51 as a melter ...
... Metering rolls 52, 53, 54, 55, 57, 58 ... Heater 56 ... Heating roll

Claims (1)

[Claims] 1. Transfer the molten resin supplied onto the applicator roll, which is placed parallel to and facing the coating roll and rotates in the opposite direction to the coating roll, to a release sheet that moves on the coating roll along with the surface of the coating roll. During coating, the release sheet is actively heated until it reaches the molten resin coating position by the applicator roll, so that the viscosity of the molten resin at the time of transfer to the release sheet is 10 to 100.
A resin coating method for a release sheet, characterized by maintaining the resin coating within a range of 0.00 poise.