JPS6223015B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a resin-impregnated sheet for producing a laminate, a so-called prepreg. To manufacture laminates using thermosetting resins,
The resin is dissolved in a solvent or monomer to form a varnish-like resin liquid (sometimes called resin varnish), which is impregnated into a base material, heated and dried, and the resin is B-staged to form a prepreg.
This is done by stacking the required number of sheets and press-molding them under heat to harden them. By the way, the process of impregnating the base material with resin liquid is an extremely important process, and if the impregnation state is insufficient, the performance of the product laminate (water absorption rate, insulation resistance, etc.) will deteriorate, so impregnation is necessary. Sufficient care was required in setting the conditions. Conventionally, the prepreg manufacturing method that has been widely adopted relies solely on the permeability of the resin liquid itself to impregnate the base material with the resin liquid. Therefore, in the conventional method, if the concentration of the resin liquid is high, impregnation does not proceed well, so a large amount of solvent is used to prepare the resin liquid (60% if the nonvolatile content in the resin liquid is phenolic resin).
(in the case of epoxy resins, less than 70% by weight) had to be used, making exhaust gas treatment difficult in the subsequent drying process. In addition, if the thickness of the base material is increased, not only will it take a long time for impregnation, but there is a risk that the resin will not be spread over the entire base material. ), and for this reason, accidents such as paper cuts often occurred during the manufacturing process of prepregs and laminates. The inventors conducted various studies in order to establish a method for efficient impregnation using a highly concentrated resin solution. The present invention was completed based on the discovery that impregnation of the resin liquid into the base material is significantly promoted by exposing the base material to water. Additionally, according to the present invention, the drying process, which has been a problem in the past, can also be improved. It is also one of the objectives of this invention to improve the drying process in this way. In this invention, a resin-retaining base material made of a cellulose base material retaining a resin liquid containing a phenol resin or an epoxy resin as a main component is subjected to a moist heat treatment, and then
This is a method for producing prepreg that dries, and is characterized in that the humidity during the heat-and-moisture treatment is higher than the relative humidity obtained when the outside air is raised to the temperature for the heat-and-moisture treatment. As the cellulose base material, various base materials containing cellulose can be used, such as kraft paper, cotton linter paper, patterned paper, and plain woven cotton cloth. Examples of resin liquids containing phenolic resins or epoxy resins as main components include those obtained by dissolving phenolic resins or modified products thereof in appropriate solvents, or those obtained by dissolving epoxy resins or modified products thereof in suitable solvents. be. 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. Furthermore, in the case of an epoxy resin, it may contain a so-called diluent, and the diluent may serve as a solvent. Examples of the solvent include those containing water, methanol, ethanol, acetone, or methyl ethyl ketone as a main component. In some cases, two or more of these solvents may be mixed. If water is selected as the solvent, the resin may not be sufficiently dissolved, resulting in an emulsion, but in some cases, even such an emulsion can be used. It is. The concentration of the resin liquid can be sufficiently impregnated even if the non-volatile content (resin content) is 60 to 100% by weight for phenolic resin and 70 to 100% by weight for epoxy resin. The upper content is preferably 70 to 90% by weight. 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% by weight, can be used. Various methods such as a roll coater method, a dipping method, and a brush coating method can be used to hold the resin liquid on the base material. Here, retention of the resin liquid refers not only to a state in which the resin liquid is merely attached to the surface portion of the base material, but also to a state in which the resin liquid is impregnated inside the base material. When applying the 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 held in the base material is preferably in a range such that the resin content of the prepreg after drying is 10 to 60% by weight. In this invention, a high concentration resin liquid can be used because the resin liquid is only attached to the surface of the base material or only a small amount is attached to the surface of the base material. However, when such a resin-retaining base material is brought into contact with heated humid air, the resin liquid impregnates the base material. This is because the impregnation of the resin liquid is substantially accelerated at this point. In addition, since the impregnation of the resin liquid is promoted in this way,
Even if the base material is made thicker, it is sufficiently impregnated. The resin holding base material is then exposed to heated humid air, that is, air containing water vapor (moisture heat treatment step). In this case, the temperature of the moist air (moist heat treatment temperature) is preferably 50°C or higher. In addition, the humidity in the heat-and-moisture treatment process is the relative humidity obtained when the outside air, that is, the air outside the heat-and-moisture treatment room (this does not necessarily mean that a separate room must be used), is raised to the temperature of the heat-and-moisture treatment. It is sufficient if the relative humidity is higher than that. For example, 35
If outside air with a relative humidity of 90% is heated to 50°C, the relative humidity will be 33%, but in that case, the humidity during moist heat treatment should be set to a relative humidity of over 33%. It is. The time for contacting the resin-retaining base material with moist air is
The time will vary depending on various factors such as the type and concentration of the resin liquid, the type and thickness of the base material, and the humidity of the humid air, so it is best to conduct a test in advance and choose the optimal time. For example, a few seconds may be sufficient for this time. The resin-retaining base material that has undergone the above moist heat treatment is dried using a method such as hot air drying, infrared radiation heat drying, high frequency heat drying, etc., to obtain a prepreg. FIG. 1 shows an embodiment of an apparatus used for the manufacturing method according to the present invention. In the figure, a base material 1 such as a rolled paper passes through a resin liquid tank 11, becomes a resin holding base material 2, passes through a squeeze roll 12, and is sent into a moist heat treatment chamber 13. Warm moist air is held in the heat-and-moisture treatment chamber 13, and the resin holding base material 2 is subjected to heat-and-moisture treatment here. In this case, the humidity in the heat-and-moisture treatment chamber 11 is higher than the relative humidity that would be obtained if the outside air was raised to the heat-and-moisture treatment temperature. At that time, the moist heat treatment may be performed by directly spraying water vapor onto the resin holding base material. As described above, by this moist heat treatment, impregnation of the resin liquid into the base material rapidly progresses. Also, when the solvent in the resin liquid evaporates,
The steam is accompanied by water vapor into the steam exhaust duct 14
The solvent is then guided to the solvent recovery device 15. However,
This solvent recovery device 15 is not essential. The resin holding base material 2 leaving the moist heat treatment chamber 13 is sent to a dryer 16. In the figure, 17 is a steam heating fin for heating the air sucked into the dryer 16, and 18 is an exhaust duct. In the moist heat treatment, the resin holding base material 2 becomes in a state of increased moisture content, and in some cases, the B stage of the resin has not progressed. In the dryer 16, heating and drying is performed to make the prepreg 3 into a perfect prepreg. In this case, since the wet heat treatment is performed first, drying can be carried out very simply and easily. An example of this situation is shown in FIG. That is, in the conventional manufacturing method, the temperature of the resin holding substrate rises slowly along the curve, but in the method of the present invention, the temperature rises more rapidly along the curve. Note that the curve represents the change in atmospheric temperature within the dryer (hot air drying). In FIG. 1, reference numeral 19 denotes a partition wall, which is provided with, for example, a slit-like passage so that the base material can pass therethrough, but the passage of water vapor and heated air can be suppressed as much as possible. As mentioned above, since drying is easy, the amount of heat or air required for this is smaller than in conventional methods. Conventionally, large amounts of solvent are discharged during the drying process, making explosion prevention and solvent recovery problematic. In this regard, in the present invention, what is discharged from the moist heat treatment chamber 13 is water vapor accompanied by a solvent.
There is little risk of explosion, and recovery of the solvent is also extremely easy. In the simplest case, it can be recovered by simply cooling it. That is, according to the present invention, it has become possible to improve the drying process. Since impregnation is greatly promoted by moist heat treatment,
If this manufacturing method is used, the thickness of the base material can be increased. For example, it is possible to use 13 to 40 mils (330 μm to 1016 μm) cardboard as the substrate. Therefore, it is possible to reduce so-called paper breakage accidents during the manufacturing process. In addition, for the same reason, a highly concentrated resin liquid with a high resin content can be used as the resin liquid, so the amount of solvent used can be reduced.
Therefore, raw material cost is low and exhaust gas treatment is easy. Next, examples of the prepreg manufacturing method according to the present invention will be described together with comparative examples and conventional examples. [Examples, Comparative Examples, and Conventional Examples] Resins with the following formulations were prepared. (Resin A) Brominated epoxy resin (Epiclon 153 manufactured by Dainippon Ink and Chemicals) 27 parts by weight (hereinafter referred to as parts) Chain epoxy resin (Epiclon 153 manufactured by Dainippon Ink and Chemicals)
1600) 10 parts hardening agent paravinylphenol 10 parts accelerator benzyldimethylamine 0.005 parts (Resin B) Bisphenol A type solid epoxy resin (epoxy equivalent 475) 70 parts liquid epoxy resin (epoxy equivalent 180) 18 parts hardening agent dicyandiamide 4 parts Accelerator Benzyldimethylamine 0.1 part (Resin C) Bisphenol A type epoxy resin (Epicote 828) 37 parts Curing agent Paravinylphenol 10 parts Accelerator Benzyldimethylamine 0.005 part (Resin D) Stirrer, thermometer, cooling In a flask with a container,
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
(equivalent to 0.4 mol of ammonia) was added and thoroughly stirred and mixed. The mixture was heated with continued stirring to boil for approximately 30 minutes and then refluxed for 60 minutes. Immediately after refluxing, the inside of the flask is heated to 100~
The internal pressure was reduced to 150 mmHg, and while heating was continued, dehydration was performed under reduced pressure to obtain a resin. The resin content of the obtained resin is
It was 87% by weight. (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 to 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, and reacted at 90°C for 150 minutes, then concentrated under reduced pressure, with a toluene content of 20% by weight and a resin content of 70%. % resin by weight was obtained. (Resin F) In a four-neck 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 alinine-modified resol resin was obtained. The resin content of this resin is 73
It was in weight%. (Resin G) In a four-necked flask equipped with a stirrer and a condenser,
940 g of phenol (equivalent to 10 mol), 655 g of 55% formaldehyde (equivalent to 12 mol of formaldehyde) and 10.1 g of triethylamine as catalyst
(equivalent to 0.1 mol) were reacted under reflux at 100° C. for 45 minutes to obtain a resol resin. The resin content was 63% by weight. <Example 1> Resin A was diluted with methyl ethyl ketone to obtain a resin liquid with a resin content of 75% by weight. As a base material, density
Using cotton linter paper with a weight of 0.52 g/cm ³ and a thickness of 10 mils (254 μm), the resin solution was applied by dip coating, and then water vapor at 100°C was sprayed on it, and the temperature was increased according to the temperature rise curve shown in Figure 3. Processing was performed for seconds. Afterwards, hot air drying is performed to reduce the resin content to 50.
~51% by weight prepreg was obtained. <Example 2> Resin B was diluted with acetone to obtain a resin liquid with a resin content of 85% by weight. A prepreg having a resin content of 50 to 51% by weight 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 with a density of 0.48 g/cm ³ and a thickness of 20 mils (508 μm), and then treated in steam at 100°C for 10 seconds according to the temperature rise curve shown in Figure 3. . Thereafter, drying was performed to obtain a prepreg with a resin content of 51% by weight. <Example 4> Resin D was diluted with methanol to obtain a resin liquid with a resin content of 50% by weight. As a base material, density 0.51g/
cm ³ , 20 mils (508 μm) thick kraft base paper was coated with the resin solution by dip coating, and then
Steam at 100° C. was blown onto the surface and the treatment was carried out for 5 seconds according to the temperature rise curve shown in FIG. Thereafter, hot air drying was performed to obtain a prepreg having a resin content of 49 to 50% by weight. <Example 5> Resin D was diluted with methanol to obtain a resin liquid with a resin content of 65% by weight. Density 0.45g/ as base material
Using kraft base paper of cm ³ and thickness of 30 mils (762 μm), the resin solution was applied by dip coating, and then
Steam at 100° C. was blown onto the surface and the treatment was carried out for 5 seconds according to the temperature rise curve shown in FIG. Thereafter, drying was performed using a high frequency heating device to obtain a prepreg having a resin content of 50 to 51% by weight. <Example 6> The resin liquid used in Example 5 above had a density of 0.65 g/
It was coated on only one side of Kraft paper having an area of cm ³ and a thickness of 13 mils (330 μm), and was then sprayed with steam at 100° C. and treated for 10 seconds according to the temperature rise curve shown in FIG. Thereafter, hot air drying was performed to obtain a prepreg having a resin content of 48 to 50% by weight. <Example 7> Resin D was diluted with methanol to obtain a resin liquid with a resin content of 75% by weight. Density 0.68g/ as base material
A prepreg having a resin content of 49 to 50% by weight was obtained by using kraft base paper having a size of cm 3 and a thickness of 20 mils (508 μm), and otherwise treating the same conditions as in Example ⁴ above. <Example 8> Resin D was diluted with methanol to obtain a resin liquid with a resin content of 80% by weight. Density 0.51g/ as base material
cm ³ , 10 mils (254 μm) thick kraft base paper was coated with the resin solution by dip coating, and then
Steam at 100° C. was blown onto the surface and the treatment was carried out for 5 seconds according to the temperature rise curve shown in FIG. 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. A prepreg was obtained by processing under the same conditions as in Example 8 except for the above. <Example 10> Resin G was used as it was as a resin liquid. As a base material, the density is 0.47 g/cm ³ and the thickness is 10 mils (254μ
The above-mentioned resin solution was applied by dip coating onto the cotton linter paper (m), and then water vapor at 100° C. was sprayed onto the paper, followed by treatment for 10 seconds according to the temperature rise curve shown in FIG. Thereafter, it was dried with hot air to obtain a prepreg with a resin content of 46% by weight. <Example 11> Resin F was diluted with methanol to obtain a resin liquid with a resin content of 70% by weight. A plain woven cotton cloth was used as the base material, and the resin solution was applied by dip coating, and then 100%
It was treated with water vapor at 15°C for 15 seconds according to the temperature increase curve shown in Figure 3. Afterwards, it is dried with hot air.
A prepreg with a resin content of 50% by weight was obtained. <Example 12> Resin D was diluted with methanol to obtain a resin liquid with a resin content of 65% by weight. Density 0.51g/ as base material
Using kraft base paper of cm ³ and thickness of 10 mils (254 μm), the resin solution was applied by dip coating, and then,
The coated substrate was introduced into a chamber with a temperature of 80°C and a relative humidity of 50% by blowing out water vapor, and treated for 10 seconds. Thereafter, hot air drying was performed to obtain a prepreg with a resin content of 49% by weight. <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 no steam treatment was performed, and the resin liquid was applied and then immediately dried. Ta. <Conventional Example 1> Resin A was diluted with methyl ethyl ketone to obtain a resin liquid with a resin content of 65% by weight. This is the density
A prepreg having a resin content of 50 to 51% by weight was obtained by dip coating onto cotton linter paper with a weight of 0.52 g/cm ³ and a thickness of 10 mils (254 μm), and then drying. <Conventional Example 2> Resin D was diluted with methanol to obtain a resin liquid with a resin content of 50% by weight. This has a density of 0.50g/cm ³ ,
The resin content
A prepreg of 49-50% by weight 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 35μ
m) was stacked, sandwiched between metal plates, and heated and formed by 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.

【table】

[Table] Additional relationships This invention is disclosed in Patent No. 981000 (Special Publication No. 54-
15465), namely, that it is a method for producing prepreg by impregnating a base material with a thermosetting resin, and that it includes a step of bringing it into contact with water vapor prior to the step of bringing it into contact with heated air. As the main part of the essential matters for its composition,
One of its objectives is to improve the drying process, which is the same objective as the invention disclosed in Japanese Patent Application No. 137513/1983. Therefore, this invention satisfies the requirements of Article 31, Item 1 of the Patent Act.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of an apparatus used for the manufacturing method according to the present invention. FIGS. 2 and 3 are graphs showing the state of temperature increase in the prepreg manufacturing method according to the present invention. 1...Base material, 2...Resin holding base material, 3...Prepreg, 11...Resin liquid tank, 12...Squeeze roll, 13...Moist heat treatment chamber, 16...Dryer, 1
9... Bulkhead.

Claims (1)

[Scope of Claims] 1. A prepreg manufacturing method in which a cellulose base material retains a resin liquid containing a phenolic resin or an epoxy resin as a main component, which is subjected to a moist heat treatment and then dried. A method for producing prepreg, characterized in that the humidity during heat treatment is higher than the relative humidity obtained when outside air is raised to the wet heat treatment temperature. 2. The method for producing prepreg according to claim 1, wherein the temperature in the moist heat treatment is 50°C or higher. 3 The amount of non-volatile content in the resin liquid is 60% by weight or more in the case of phenolic resin, and 70% by weight in the case of epoxy resin.
The method for manufacturing a prepreg according to claim 1 or 2, which is the above.