JPS6311124B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for manufacturing prepreg. Laminated boards such as paper-based copper-clad laminates are required to have highly insulating substrates. Since this substrate is made of prepreg, which is a cellulose base material impregnated with a resin liquid, moisture that impairs electrical insulation is removed from the prepreg during production of the laminate. That is, moisture in the prepreg is removed by heating the prepreg with hot air, steam, electric heat, or the like. However, the moisture in this prepreg is due to the 7 to 10% moisture contained in the cellulose base material, and because the cellulose base material itself is highly hydrophilic, it is difficult to use the external heating method described above. It cannot be easily removed. Furthermore, when the temperature is high, such as 130° C. or higher, a keratinization phenomenon occurs and the base material becomes brittle. Moreover, according to the external heating method, the impregnated resin of the prepreg is cured first, so there is a limit to how much water can be removed. Therefore, the obtained laminate had a problem in electrical insulation (particularly electrical insulation after boiling). It has been considered to use a thin cellulose base material, but this also poses a problem, as this would result in poor productivity and increased costs. Therefore, as a result of repeated research to solve these problems, the inventor developed a resin-impregnated base material (prepreg) in which a cellulose base material is impregnated with a resin liquid.
The inventors have discovered that the desired objective can be achieved by applying microwave heating to a material under a moist heat atmosphere and then drying it, and have thus arrived at this invention. That is, the gist of the present invention is to subject a resin-impregnated base material, which is a cellulose base material impregnated with a resin liquid, to microwave heating in a moist heat atmosphere, and then to dry it. Traditionally used infrared heating is 10 ^-4 to ^{10 -6} m
In contrast, the microwave heating of the present invention is in the wavelength range of 1 to 10 ^-1 m. The reason why the present invention provides good results is considered to be due to the following reasons. In other words, by heating the resin-impregnated base material (prepreg) with microwaves, only the water in the cellulose base material is selectively heated (internal heating), vaporized, and discharged to the outside, thereby coarsening the internal structure. When this was cooled by stopping the microwave heating, the inside was in a reduced pressure state, and the resin on the surface side of the cellulose base material was transferred to the inside by subsequent drying, and the resin was evenly impregnated with almost no moisture. It is thought that it will become possible to obtain a prepreg of the same condition. By performing microwave heating in a moist heat atmosphere, it becomes possible to obtain a uniform distribution of microwaves and a cooling prevention effect due to convection, thereby further improving the effect of microwave heating. Next, this invention will be explained in detail. Examples of the cellulose base material used in this invention include various base materials containing cellulose, such as kraft paper, cotton linter paper, patterned paper, and plain-woven cotton cloth. Examples of the resin liquid include those obtained by dissolving a phenolic resin (water-soluble resol resin), an amino resin (urea, melamine), an unsaturated polyester resin, or an epoxy resin in a suitable solvent. Even if no particular solvent is added, the resin may contain a monomer and the monomer may serve as a solvent. Any resin that exhibits a liquid state can be used as is. Note that the above-mentioned solvents include those containing water, methanol, ethanol, acetone, or methyl ethyl ketone as a main component. In some cases, two of these
The above solvents may be mixed. The concentration of the resin liquid is such that the non-volatile content (resin content) is 60 to 100% by weight (hereinafter abbreviated as "%") for phenolic resins and amino resins, and for epoxy resins.
Although it is possible to achieve sufficient impregnation even at a concentration of 70 to 100%, it is preferably 70 to 90% in practice. However, the concentration of the resin liquid is not limited to this range, and it goes without saying that a resin liquid with a lower concentration than this, for example, about 40%, can be used. Various methods can be used to impregnate the base material with the resin liquid, such as a roll coater method, a dipping method, and a brush coating method. When applying resin liquid,
The resin liquid may be applied to only one side of the base material, or may be applied to both sides. The amount of resin liquid impregnated into the base material is preferably in a range such that the resin content of the prepreg after drying is 10 to 60%. Microwave heating of the prepreg in a moist heat atmosphere is performed using a known microwave heating device in a moist heat atmosphere, for example, in a heating atmosphere with a relative humidity of 100%. The heating time is appropriately selected depending on the type and concentration of the resin liquid, the thickness of the base material, and the like. Tests are conducted in advance to select the most suitable time. In this case, by microwave heating, only the moisture inside the base material is directly heated, so the heating time can be shortened to 1/10 to 1/100 compared to normal external heating.
That is, the temperature of the resin of the prepreg does not rise, but only the temperature of the water rises, vaporizes, and evaporates from the surface of the prepreg. This evaporation causes the internal structure of the cellulose base material to become coarse due to the evaporation of water.
A moist heat atmosphere improves the efficiency of this microwave heating. Drying after microwave heating is usually performed using a known hot air dryer. During this hot air drying, the inside of the cellulose base material is at a lower temperature than during microwave heating, and is in a cooled state, so the inside of the base material is under reduced pressure, and the impregnated resin on the surface side is transferred to the rough areas inside. Penetrate. As a result, a prepreg with almost no moisture and uniformly impregnated with resin can be obtained. FIG. 1 shows an embodiment of an apparatus used for the manufacturing method according to the present invention. In the same figure, resin liquid tank 1
A base material 1 such as a roll paper passed through the wafer 1 becomes a resin-impregnated base material 2, and is fed into a moist heat microwave processing chamber 13 via a squeeze roll 12. This room 13
Warmed humid air is held inside, and the resin-impregnated base material 2 is subjected to microwave heating in a moist heat atmosphere. In this case, the humidity in the moist heat microwave processing chamber 13 is set to 100% RH. Microwave heating may be performed while directly spraying heated steam onto the resin-impregnated base material. By microwave heating in this moist heat atmosphere, only the moisture in the base material can be selectively heated and expelled from the base material while preventing the impregnated resin in the resin-impregnated base material from drying. Then, the resin-impregnated base material 2 that has left the wet heat microwave treatment chamber 13 is placed in a dryer 16.
It is sent to dryer 16, dried, and comes out from dryer 16. In the figure, 15 is a microwave oscillator, 17 is a dryer 1
18 is an exhaust duct. Next, examples will be described together with comparative examples and conventional examples. [Examples, Comparative Examples, and Conventional Examples] A resin having the following formulation was prepared. (Resin A) Brominated epoxy resin (Epicron 153 manufactured by Dainippon Ink Chemical Industries, Ltd.)
27 parts by weight (hereinafter referred to as "parts") Chain epoxy resin (Epiclon 1600 manufactured by Dainippon Ink and Chemicals) 10 parts Curing agent Paravinylphenol 10 parts Accelerator Benzyldimethylamine 0.005 parts (Resin B) Bisphenol type A Solid epoxy resin (epoxy equivalent: 475) 70 parts Liquid epoxy resin (epoxy equivalent: 180) 18 parts Curing agent Dicyandiamide 4 parts Accelerator Benzyldimethylamine 0.1 part (Resin C) Bisphenol A type epoxy resin (Epicoat)
828) 37 parts Hardening agent Paravinylphenol 10 parts Accelerator Benzyldimethylamine 0.005 parts (Resin D) In a flask equipped with a stirrer, thermometer, and condenser,
940g of phenol (equivalent to 10 moles), 470g of tung oil,
1.75 g of para-toluenesulfonic acid was added and mixed with stirring. The mixture was heated with stirring to 110° C. after about 40 minutes and then refluxed for 30 minutes. Immediately after refluxing, the mixture was cooled to room temperature in about 30 minutes. In addition, 1095 g of 37% formaldehyde (equivalent to 13.5 moles of formaldehyde) and 27.2 g of 25% aqueous ammonia are added.
(equivalent to 0.4 mol of ammonia) was added and thoroughly stirred and mixed. The mixture was heated with continued stirring to boiling for approximately 30 minutes and then refluxed for 60 minutes. Immediately after refluxing, pump the inside of the flask to 100 to 150 ml.
The internal pressure was reduced to mmHg, and dehydration was performed under reduced pressure while continuing heating to obtain a resin. The resin content of the obtained resin is 87
It was %. (Resin E) Xylene formaldehyde resin (molecular weight 450)
1700 g, 850 g of phenol, and 4.0 g of para-toluenesulfonic acid were placed in a four-necked flask equipped with a stirring bar and a condenser, heated to 100-105°C, reacted for 30 minutes, and then reacted for an additional 120 minutes while dehydrating. . This was cooled to 40°C, 330g of paraformaldehyde, 5.2g of triethylamine and 800g of toluene were added as a solvent, reacted at 90°C for 150 minutes, and then concentrated under reduced pressure to reduce the toluene content to 20%.
%, a resin with a resin content of 70% was obtained. (Resin F) In a four-necked flask equipped with a stirrer and a condenser,
940 g of phenol (equivalent to 10 mol), 488 g of 80% formaldehyde (equivalent to 13 mol of formaldehyde), 15 g of aniline (equivalent to 0.16 mol) and 10.1 g of triethylamine (equivalent to 0.1 mol) as a catalyst were reacted at 100°C for 90 minutes. , an aniline-modified resol resin was obtained. The resin content of this resin is 73
It was %. (Resin G) In a four-necked flask equipped with a stirrer and a condenser,
940 g of phenol (equivalent to 10 moles), 655 g of 55% formaldehyde (equivalent to 12 moles of formaldehyde)
and 10.1 g (0.1
(corresponding to moles) were reacted under reflux at 100°C for 45 minutes to obtain a resol resin. The resin content was 63%. [Example 1] Resin A was diluted with methyl ethyl ketone to obtain a resin liquid with a resin content of 75%. As a base material, density 0.52
g/cm ³ , 10 mils (254 μm) thick cotton linter paper, the resin-impregnated base material was dip-coated with the resin solution and heated with 2450 MHz microwave (5 KW) in water vapor at 100°C (100% RH). ) for 5 seconds. Thereafter, hot air drying was performed to obtain a prepreg with a resin content of 50 to 51%. [Example 2] Resin B was diluted with acetone to obtain a resin liquid with a resin content of 85%. A prepreg with a resin content of 50 to 51% was obtained by processing under the same conditions as in Example 1, except that this resin liquid was used as the resin liquid. [Example 3] Resin C was used as a resin liquid without adding any other solvent. This was applied by dip coating onto cotton linter paper having a density of 0.48 g/cm ³ and a thickness of 20 mils (508 μm), and then irradiated with 2450 MHz microwave (5 KW) for 10 seconds in water vapor at 100°C. After that, it was dried to obtain a prepreg with a resin content of 51%. [Example 4] Resin D was diluted with methanol to give a resin content of 50%.
It was made into a resin liquid. As a base material, density 0.51g/cm ³ ,
Using kraft paper with a thickness of 20 mils (508 μm),
The resin liquid was applied by dip coating, and then 2450MHz microwave (5KW) was irradiated for 5 seconds while spraying water vapor at 100°C. Thereafter, hot air drying was performed to obtain a prepreg with a resin content of 49 to 50%. [Example 5] Resin D was diluted with methanol to give a resin content of 65%.
It was made into a resin liquid. As a base material, density 0.45g/cm ³ ,
Using kraft paper with a thickness of 30 mils (762 μm),
The resin liquid was applied by dip coating, and then 2450MHz microwave (5KW) was irradiated for 5 seconds while spraying water vapor at 100°C. Afterwards, it is dried using a high-frequency heating device to reduce the resin content to 50-51%.
prepreg was obtained. [Example 6] The resin liquid used in Example 5 had a density of 0.65 g/cm ³ ,
It was coated on only one side of 13 mils (330 μm) thick kraft paper, and then irradiated with 2450 MHz microwave (5 KW) for 10 seconds while spraying water vapor at 100°C. Afterwards, hot air drying is performed to reduce the resin content to 48.
~50% prepreg was obtained. [Example 7] Resin D was diluted with methanol to give a resin content of 75%.
It was made into a resin liquid. As a base material, density 0.68g/cm ³ ,
Using kraft paper with a thickness of 20 mils (508 μm),
Other conditions were the same as in Example 4 to obtain a prepreg with a resin content of 49 to 50%. [Example 8] Resin D was diluted with methanol to achieve a resin content of 80%.
It was made into a resin liquid. As a base material, density 0.51g/cm ³ ,
Using kraft paper with a thickness of 10 mils (254 μm),
The resin liquid was applied by dip coating, and then 2450MHz microwave (5KW) was irradiated for 5 seconds while spraying water vapor at 100°C. Thereafter, it was dried with hot air to obtain a prepreg with a resin content of 49%. [Example 9] Resin E was used as it was as a resin liquid. The other conditions were the same as in Example 8 to obtain a prepreg. [Example 10] Resin G was used as it was as a resin liquid. As a base material, density 0.47g/ ^cm3 , thickness 10mils (254μm)
The resin solution was dip-coated using Kotsuton linter paper, and then 2450 MHz microwave (5 KW) was irradiated for 10 seconds while spraying water vapor at 100°C. After that, it is dried with hot air and the resin content is 46.
% prepreg was obtained. [Example 11] Resin F was diluted with methanol to give a resin content of 70%.
It was made into a resin liquid. Then, using a plain-woven cotton cloth as a base material, the resin liquid was dip-coated onto it, and then
2450MHz microwave (5KW) was irradiated for 15 seconds in a steam atmosphere at 100℃. Thereafter, it was dried with hot air to obtain a prepreg with a resin content of 50%. [Example 12] Resin D was diluted with methanol to give a resin content of 65%.
It was made into a resin liquid. And as a base material, density 0.51
g/cm ³ and 10 mils (254 μm) thick kraft paper, the above resin solution was applied by dip coating, and then water vapor was blown out at a temperature of 80°C and a relative humidity of 50%.
The coated substrate was introduced into a chamber where the coating was heated and irradiated with 2450MHz microwaves (5KW) for 10 seconds. Thereafter, hot air drying was performed to obtain a prepreg with a resin content of 49%. [Example 13] The conditions for steam treatment were a temperature of 60°C and a relative humidity of 30%.
A prepreg was obtained by processing under the same conditions as in Example 12, except that the processing was carried out in a room for 5 seconds. [Comparative Examples 1 to 11] In Examples 1 to 11, the same manufacturing conditions as those of the correspondingly numbered examples were used, but the wet heat microwave treatment was not performed and the resin liquid was applied and then dried immediately. I did it. [Conventional Example 1] Resin A was diluted with methyl ethyl ketone to obtain a resin liquid with a resin content of 65%. This has a density of 0.52
g/cm ³ and 10 mils (254 μm) thick cotton linter paper by dip coating, followed by drying to obtain a prepreg with a resin content of 50 to 51%. [Conventional example 2] Resin D was diluted with methanol to a resin content of 50
% resin liquid. This was applied by dip coating onto kraft base paper with a density of 0.50 g/cm ³ and a thickness of 10 mils (254 μm), and then dried with hot air to obtain a resin content of 49 to 50.
% prepreg was obtained. (Manufacture of laminates) A predetermined number of prepregs obtained in each of the above Examples, Comparative Examples, and Conventional Examples are stacked one on top of the other, and one piece of adhesive-coated copper foil (thickness
35 μm), sandwiched between metal plates, and heated and formed using a conventional method to produce a product, a single-sided copper clad plate. The manufacturing conditions were as shown in Table 1. (Performance) Table 2 shows the performance of the obtained single-sided copper clad board.

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[Table] From Table 2, it can be seen that the Example product has superior performance compared to the Comparative Example product and the Conventional Example product. As described above, the present invention is characterized in that a resin-impregnated base material, which is a cellulose base material impregnated with a resin liquid, is subjected to microwave heating in a moist heat atmosphere and then dried, which increases costs. It is possible to obtain a prepreg in which water is almost completely removed and the resin is uniformly impregnated without any problem.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an apparatus used for carrying out the present invention. 1...Base material, 2...Resin-impregnated base material, 12...Squeeze roll, 13...Moist heat microwave treatment chamber,
15...Microwave oscillation device, 16...Dryer,
17... Steam heating erofine, 18... Exhaust duct.

Claims (1)

[Scope of Claims] 1. A prepreg manufacturing method, which comprises subjecting a resin-impregnated base material, which is a cellulose base material impregnated with a resin liquid, to microwave heating in a moist heat atmosphere and then drying the base material. 2. The prepreg manufacturing method according to claim 1, wherein the moist heat atmosphere is a heated steam atmosphere with a relative humidity of 100%.