JPH0558372B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for continuously manufacturing a laminate suitable for various electrical insulations, printed circuit boards, etc., in particular.

"Conventional technology" A long base material such as kraft paper is sufficiently impregnated with a thermosetting resin liquid without leaving any voids, and multiple sheets of this impregnated base material are stacked one on top of the other and pressurized or heated without pressurization. Conventionally, laminates are manufactured continuously by curing a resin liquid.

However, among these methods, curing without pressure forms a thermosetting resin tank between the base materials, and
The content of the base material in the resulting laminate is relatively low, and mechanical properties such as strength and rigidity tend to be insufficient.

In order to solve this problem of insufficient base material content, there is a method in which multiple sheets of impregnated base materials that are sufficiently impregnated without leaving any voids are stacked together and cured under pressure using a double belt press, etc., as described above. ,
It is possible to increase the base material content and reduce the resin content, but most of the impregnated resin is discharged from the base material when pressurized, which tends to cool the surrounding machinery, and the amount of discharged resin is huge, so the discharged resin Although it is necessary to recover the waste, the task is extremely difficult.

In view of these problems, the present inventors have proposed a method for continuous production of laminates using a specific double belt press that reduces the amount of resin discharged or does not require resin recovery, as disclosed in Japanese Patent Application Laid-Open No. 2-59343. JP-A-2-86441, JP-A-2-99327, JP-A-2-143857
It was proposed in the publication. For example, in JP-A-2-59343, a long base material is impregnated with a thermosetting resin liquid, and a plurality of the resin liquid-impregnated base materials are stacked and heated and pressurized to harden the resin liquid and integrate them. In the continuous manufacturing method for laminates, after partially impregnating the base material with a resin liquid, a double belt press consisting of an endless belt with substantially uniform pressure over the entire pressure zone is used to partially impregnate the base material. A method for continuously producing a laminate is proposed in which the impregnation resin liquid is heated and pressurized while measuring the penetration of the resin liquid into the entire base material. According to this method, there is almost no discharge of the impregnated resin liquid during pressurization by the double belt press, and it becomes possible to continuously produce a laminate with a high base material content and substantially no air bubbles.

``Problems to be Solved by the Invention'' However, the method for producing the laminate has the disadvantage that the laminate obtained by continuous heating and pressure tends to warp or wave.

The present invention was made in order to solve the above-mentioned disadvantages, and an object of the present invention is to provide a method for continuously manufacturing a laminated plate with good dimensional accuracy without warping or waving.

"Means for Solving the Problems" The inventors of the present invention have realized that when a resin liquid-impregnated base material is pressure-heated and cured using a double belt press, by controlling the degree of curing of the resin liquid, a laminate without the above-mentioned defects can be produced continuously. The present invention was completed based on the discovery that this can be obtained.

In other words, the gist of the present invention is to apply a thermosetting resin liquid to a long base material, which essentially does not require a drying process, and which does not substantially generate reaction by-products such as gas or liquid during the curing reaction process. A continuous manufacturing method for a laminate comprising an impregnating step of impregnating the substrate, and a heating step of superimposing and heating a plurality of impregnated base materials to cure the resin liquid and integrate the resin liquid. partially impregnating the substrate with the liquid, and in the heating step, using a double belt press constituted by an endless belt having a substantially uniform pressure over the entire pressure zone,
While measuring the penetration of the partially impregnated resin liquid into the entire base material, heat and pressure is applied to continuously semi-cure the resin to the extent that elastic recovery of the base material does not occur, and then heat and harden continuously under no pressure. In that case, a method of overlapping metal foils at the same time or in a separate process;
A method of press-fitting at 100 kg/cm ² , a method of using paper as a base material, and a method of partially impregnating the base material with resin liquid, and then using the double belt press described above, metal foil and multiple sheets of base material impregnated with resin liquid. The partially impregnated resin liquid is heated and pressurized while measuring the penetration of the partially impregnated resin liquid into the entire base material, so that the resin liquid is continuously semi-cured to the extent that elastic recovery of the base material does not occur. Then, the laminate is continuously heated and cured under no pressure and then cooled, and the warpage of the laminate is continuously corrected.

The present invention will be explained in detail below.

In the present invention, the long base material is, for example, a long glass fiber cloth, a glass fiber type material such as a glass nonwoven fabric, a paper mainly composed of cellulose fibers such as kraft paper, aluminum hydroxide mixed paper, linter paper, etc. ,
Refers to a sheet or band-like material made of inorganic fibers such as asbestos cloth. When paper is used as the sheet material base material, from the viewpoint of impregnability and quality, it is preferable to use paper mainly composed of cellulose fibers, such as kraft paper, with an air-dried density (bulk specific gravity) of 0.3 to 0.7 g/cc. .

These base materials improve their water resistance by performing an impregnation drying treatment using a treatment agent such as methylol melamine, methylol phenol, methylol guanamine, or N-methylol compound before impregnating them with a thermosetting resin liquid. This is preferable because electrical characteristics can be improved by reducing hygroscopicity. The amount of the treatment agent deposited here is usually 5 to 35 parts by weight relative to the base material (100 parts by weight).

In addition, the thermosetting resin liquid referred to in the present invention that essentially does not require a drying process and does not substantially generate reaction by-products such as gas or liquid during the curing reaction process is a conventionally known unsaturated polyester resin. refers to thermosetting resins that are liquid at room temperature, such as allyl resins, allyl resins, vinyl ester resins, and epoxy acrylate resins.These resins have unsaturated groups in their molecules, and there are It is a resin that has the characteristic of being crosslinked via a vinyl monomer, and such resins also include epoxy resins.

These thermosetting resins are liquid with low viscosity when impregnated into the base material, and harden after being impregnated into the base material.
It bonds well with the substrate and is suitable for the method of the present invention.

In addition, if necessary, a halogen-containing flame retardant imparting component and a flame retardant aid such as phosphoric acid ester, antimony trioxide, or aluminum hydroxide may be added to the thermosetting resin liquid used for impregnating the base material. It may also be used as

In addition, when using any thermosetting resin liquid, the viscosity of the resin liquid can be adjusted as appropriate depending on the purpose of use of the laminate to be manufactured, the pressure during pressure molding, etc., but usually 25 A temperature of about 0.05 to 500 poise at °C is suitable. In other words, if it exceeds 500 poise, impregnating the base material becomes poor and bubbles tend to remain in the resulting laminate, while if it is less than 0.05 poise, impregnating property is good, but it is difficult to pressurize with the double belt press described below. This is because sometimes the amount of impregnating resin liquid discharged to obtain a bubble-free laminate becomes large, which is undesirable.

Then, the elongated base material is partially impregnated with such a thermosetting resin.

Here, the partial impregnation of a thermosetting resin liquid into a base material specifically refers to the following.

(a) Each of the plurality of long base materials is impregnated with the thermosetting resin liquid to the same extent, but instead of impregnating all the voids in each base material with the resin liquid, some of the voids are left unfilled. The state of impregnation. In other words, although the impregnation rate is approximately uniform at any position in the length direction or width direction of the base material, some of the voids are not impregnated with the resin.
Taking kraft paper as an example of a base material, the porosity of kraft paper is usually 60 to 70% by volume (when air-dried), but this porosity is, for example, about 30 to 40% by volume, regardless of the position of the base material. The resin liquid is impregnated into the base material so that the resin liquid is impregnated with the resin liquid.

(b) For each of the plurality of long base materials, the center portion in the width direction of the base material is impregnated with the resin liquid at a high impregnation rate, and both side portions are not impregnated or have a lower impregnation rate than the center portion. It impregnates the base material at a uniform rate, forming a concentration distribution of the resin liquid in the width direction of the base material. For example, if the base material is divided into three equal parts in the width direction, the impregnation rate will be approximately 100 in the central part.
%, and divide it into five equal parts so that the impregnation rate is about 0 to 30% on both sides, and make the impregnation rate around 100% in the center. around 50% on both sides, and 0 to 30% on the outermost side.
There are some types in which the impregnation is lower towards both side edges, as shown in the figure.

(c) A laminate in which a plurality of resin-impregnated substrates are stacked one on top of the other, forming a resin liquid concentration distribution in the thickness direction of the laminate. For example, when laminating five base materials, the impregnation rate for the one base material located in the center is approximately 100%, and the impregnation rate for the two base materials located outside this is 50 to 60%.
The two outermost substrates are impregnated with the resin liquid at an impregnation rate of about 0 to 20%.

(d) A combination of (b) and (c) above. That is,
In a laminate in which a plurality of base materials are laminated together after being impregnated with resin, the central portion in two directions, the width direction and the thickness direction, is highly impregnated, and the peripheral portion is impregnated less.

The following methods can be mentioned. In this case, even if the concentration distribution is formed in the width direction of the base material or the thickness direction of the laminate, if the resin liquid impregnation rate is higher in the outer part than in the inner part, heating by the double belt press in the next step When pressurized, a portion of the resin liquid is discharged outward from the base material, making treatment of the discharged resin complicated, and it is not possible to penetrate the entire base material to the required impregnation rate, which is undesirable. .

Impregnation of these long base materials with curable resin liquid is
This is carried out by appropriately selecting a known method such as a coating method or a dipping method depending on the above-mentioned partial impregnation method.

In addition, the amount of impregnation of the curable resin liquid is related to the pressure applied during the next process with the double belt press, and it is important to ensure that the pressure does not cause excessive flow to be discharged outside the base material and that the resulting laminate is The amount of resin liquid is adjusted to be such that substantially no air bubbles are present, and the amount of resin liquid discharged from the base laminate when pressurized with a double belt press is 10% or less of the amount of cured resin in the product laminate, preferably 5% or less of the amount of cured resin in the product laminate. %
It is desirable to have the following.

After a plurality of long base materials impregnated with the curable resin liquid in this way are stacked to form a laminate, or are stacked together to form a laminate, substantially all of the entire pressure zone is covered. While being heated and pressurized by a double belt press having an even pressure, the impregnated resin fills the voids in the base material as widely as possible, and the impregnation is completed to form a laminate.

In the present invention, a double belt press that has substantially uniform pressure over the entire pressure zone is a double belt press in which, for example, stainless steel endless belts with a thickness of about 1 mm are installed above and below, and a resin is placed between the upper and lower belts. It is capable of heating and pressurizing a liquid-impregnated base material with scissors, and has a structure such that the pressure of the pressure band is substantially uniform. To give a specific example, (1) A plurality of rows of roll pairs are arranged to sandwich the upper and lower belts and apply pressure to the belts, and the roll diameter is 50 mm or less and the ratio of the roll pitch to the roll diameter is 1.2. This method reduces the pressure drop between adjacent rolls in the following way, and the position of the rolls may be fixed or placed between the endless belt and pressure plates installed above and below the endless belt. , may revolve around the pressure plate. If the diameter of the rolls becomes large and the distance between the rolls is too large, large waves will occur in the pressure applied to the substrate, which is undesirable. (2) A method in which the upper and lower endless belts are sandwiched, a pressure plate is placed to apply pressure to the belt, and a pressure medium is press-fitted and circulated between the pressure plate and the endless belt for the purpose of lubrication; or (3) )The upper and lower endless belts are sandwiched to create a container for storing pressure medium, and the opening of this container is in contact with the endless belt, and the pressure medium directly presses the endless belt. This is particularly suitable because the pressure difference across the entire pressure band is small.

Regardless of the type of double belt press, the presence of a large pressure distribution, especially the presence of large pulsating pressure in the direction of movement, makes it difficult to selectively discharge air bubbles in the resin liquid-impregnated base material. In addition, when the pressure drops, air tends to re-enter into the laminate, which should be avoided. For example, the pressure distribution is preferably ±50% or less and ±5 Kg/cm ² or less.

Further, the applied pressure varies depending on the viscosity and curing speed of the curable resin liquid used and the type of substrate, but is appropriately selected in order to control the content of the substrate in the resulting laminate. Usually from 1Kg/cm ² G
100Kg/cm ² G, preferably from 10Kg/cm ² G
It is 50Kg/cm ² G. When the pressure is lower than 1 Kg/cm ² G, not only is it difficult to increase the base material content, but also the air evacuation effect is small and the laminate is likely to have air bubbles mixed in. On the other hand, if the pressure is greater than 100Kg/cm ² G,
Not only is it unnecessary for removing air bubbles, but the base material content in the resulting laminate becomes too large, which tends to cause deterioration in strength such as delamination.

During heating and pressure curing with this double belt press, when the laminate is released from the double belt press and the pressure is released, the laminate does not recover in the thickness direction due to the elastic restoring force of the compressed base material. In addition, it is necessary that the resin liquid be semi-cured to the extent that it can withstand continuous transportation in the next pressureless heating step. When the degree of curing of the resin liquid is low, the bonding force of the semi-cured resin to the base material is weak, allowing the base material to recover elastically and allowing air to re-enter from the outside, resulting in a laminate with bubbles. On the other hand, if the degree of curing of the resin is too high, warping or waving will occur in the resulting laminate. The temperature applied to this semi-curing varies depending on the type of thermosetting resin liquid used, the type of curing catalyst, etc., but the temperature is usually in the range of 50°C to 200°C, preferably 100°C. to 200℃. At temperatures below 50°C, the curing time is too long and uneconomical;
If the temperature exceeds .degree. C., internal strain is likely to occur due to the rapid progress of curing, and when a crosslinkable vinyl monomer is used, interlayer peeling is likely to occur due to evaporation of the monomer.

When pressurized by such a double belt press, the resin liquid in the laminate of multiple base materials partially impregnated with thermosetting resin liquid is applied to the non-impregnated base materials by the pressure applied. It penetrates the entire laminate until it is evenly impregnated. This is because a large pressure gradient occurs in the laminate at the inlet of the double belt press in the opposite direction to the direction in which the laminate travels, and this pressure gradient promotes the penetration and impregnation of the resin liquid into the unimpregnated parts of the base material. This is presumed to be due to the fact that the replacement between the remaining air bubbles in the base material and the resin liquid is promoted. A portion of the displaced air bubbles are then continuously driven through the base material laminate in a direction opposite to the traveling direction, and continue to be removed from the laminate under pressure. In addition, some of the air bubbles are driven to both side edges of the laminate due to the pressure gradient that also occurs in the width direction of the laminate, and the air bubbles are eliminated as a small amount of resin liquid is discharged, thereby effectively reducing the A laminate with no air bubbles is obtained. Since the base material is partially impregnated with the thermosetting resin liquid, it is possible to almost eliminate discharge of the resin liquid from the base material laminate even when pressurized by a double belt press. . In other words, the base material can be partially impregnated with only an amount of resin liquid corresponding to the resin in the resulting laminate, so that no excess resin liquid is present in the laminate before pressurization. This is because it becomes possible. If the resin liquid is not discharged, there is no need to collect it in the double belt press, and the double belt press will not be contaminated, and the structure of the double belt press can be simplified.

Thereafter, the laminate, which has been semi-cured by pressure heating using a double belt press, is then continuously heated in a pressureless heating furnace or the like to substantially complete the curing of the curable resin. This continuous curing under no pressure makes it possible to obtain a laminate without warping or waviness. During pressure heating using the double belt press, stress is generated in the laminate due to forced penetration and impregnation of the resin liquid into the base material, and if the resin hardens too much under pressure, residual stress will be generated. However, it is presumed that the stress is removed by releasing the pressure in a semi-cured state and further proceeding with curing. When cutting immediately after semi-curing with a double belt press to substantially complete curing in batches, stress remains near the cut surface and causes warping of the surrounding area, so it is difficult to complete curing under continuous conveyance. This is essential in order to obtain a laminate with good precision.

Further, the heating temperature under continuous pressureless operation is usually higher than the heating temperature under pressure using a double belt press and 200° C. or lower. If the heating temperature is lower than the heating temperature under pressure, it will take a long time to substantially complete curing, which is not only uneconomical, but may also prevent curing from proceeding. , there is a risk that the laminate or metal foil may become discolored or become warped.

The laminate, which has been substantially completely cured by heating under no pressure in this way, is cut into a rectangular shape with predetermined dimensions using a cutter such as a guillotine cutter.
If necessary, warp correction and end face treatment are performed to produce the product. In this case, the warp correction and the end face treatment in the longitudinal direction can also be performed continuously following the heat treatment before cutting with a cutter. In particular, in the case of single-sided metal foil-clad laminates, the laminate warps at room temperature becomes large due to curing shrinkage of the curable resin liquid and the difference in linear expansion coefficient between the metal foil and the cured resin containing the base material. Therefore, it is often necessary to straighten the warp, and after cooling the single-sided metal foil-clad laminate, which has been substantially completely cured by heating under no pressure, to a predetermined temperature, the warp straightening machine such as a roll is used to continuously straighten the warp. It is desirable to straighten the warp and then cut it. Here, the temperature of the laminate during warp correction is preferably close to room temperature, and is usually about 50° C. or lower, although it varies depending on the substrate used and the type of thermosetting resin liquid.

The laminate obtained in this way varies depending on the type of base material and thermosetting resin used, the conditions of pressurization or heating, etc., but usually the base material content (the amount of base material in the laminate) weight%) is 30
-80% by weight, and for example, when kraft paper is used as the base material, about 35-65% by weight is suitable. In other words, if the kraft paper content is less than 35% by weight, the resulting laminate will have low mechanical strength and bending rigidity, while if it exceeds 65% by weight, it will not only tend to cause delamination, but also have poor punchability and moisture resistance. This is because it causes a decrease in sexual performance, which is undesirable.

In addition, in order to manufacture metal foil-clad laminates, metal foil is overlaid on one or both sides of a laminate made of a resin liquid-impregnated base material at the same time as the base materials are overlaid or a little later, and this is double belted. This is done by feeding the press. As the metal foil used here, an electrolytic copper foil intended for use in printed circuit boards is suitable from the viewpoint of touch resistance, etching property, and adhesion, but aluminum foil or the like may also be used. Further, as such metal foil, one having a thickness of 10 to 100 μm is usually used, and it is more preferable that the adhesive surface is roughened to improve adhesiveness.

An adhesive is preferably used to bond the metal foil and the resin-impregnated base material. The adhesive is preferably a liquid or semi-fluid adhesive that does not generate unnecessary reaction by-products during the curing process, ie, has a viscosity of preferably 5000 poise or less. From this point of view, for example, epoxy-acrylate adhesives, epoxy resin adhesives, polyisocyanate adhesives, or various modified adhesives thereof are suitable. As the epoxy adhesive, a mixture of a bisphenol A type epoxy resin and a curing agent such as a polyamide resin or amines is suitable.
By introducing such an adhesive, it is possible to produce a metal foil-clad laminate that has excellent adhesive strength of metal foil, and also has excellent solder heat resistance and electrical insulation properties.

When using the adhesive applied to metal foil, heat-treat it at 60-150℃ for 2-7 minutes after application.
It may be precured to a semi-cured state. Furthermore, the adhesive can be applied simultaneously during lamination. The thickness of the adhesive coating may be about 10 to 100 μm, and preferably 20 to 50 μm.

The thickness of the laminate obtained by the present invention depends on the type of base material,
Although it varies depending on the composition of the thermosetting resin liquid, the use of the laminate, etc., 0.5 to 3.0 mm is usually suitable.

"Examples" The present invention will now be described in more detail with reference to Examples.

FIG. 1 is a diagram showing an example of an apparatus suitably used to carry out the method of the present invention. This device includes a roll 1 for feeding out a base material A, and an impregnating tank 2 for impregnating the base material A with a thermosetting resin liquid B.
..., a double belt press 3 for performing pressure heat treatment, a heating furnace 4 for performing heat treatment under normal pressure, a roll 5 for feeding out metal foil C, and applying adhesive to metal foil C. The device is equipped with a coating machine 6 for heating the adhesive and a heating furnace 7 for preheating the adhesive. The double belt press 3 is of a pressure medium storage type, and has drums 8a, 8a, 8b, 8.
b, endless belts 9, 9 wound between them, a pressurizing chamber 10, and a pressure medium 11 made of high temperature fluid filled in the pressurizing chamber 10. be.

In order to manufacture a laminate by carrying out the method of the present invention using such an apparatus, a plurality of base materials A made of, for example, paper etc. are simultaneously fed out from roll 1 and each is coated with impregnated layer 2. After being impregnated with the thermosetting resin liquid B, these base materials A are transferred between the endless belts 9 of the double belt press 3 in a stacked state. At the same time, a metal foil C made of, for example, copper foil is fed out from the roll 5, coated with adhesive by a coating machine 6, and then preheated in a heating furnace 7 to form the outermost layer. The base material A is transferred between the endless belts 9, 9 while being superimposed on the base material A. Then, thermosetting resin liquid B was added using double belt press 3.
A plurality of substrates A impregnated with... and metal foil C are heated under pressure to primarily cure the resin liquid, and then heated under normal pressure in a heating furnace 4 to substantially cure the resin liquid. After completion, it is further cooled in the cooling chamber 12 to form a laminate. Thereafter, the laminate is successively passed through a long-axis straightening roll 13 and a short-axis straightening roll 14 to correct warpage in both the long-axis and short-axis directions of the laminate, and then a guillotine cutter 15 The product is continuously cut to obtain a single-sided metal foil-clad product D having a predetermined size.

In addition, although the above example shows an example in which one side is coated with metal foil, it is also possible to produce a laminate without metal foil affixed using the above apparatus, and in that case, a laminate plate impregnated with thermosetting resin B can be used. Only the base materials A are overlapped and the phase is shifted between the endless belts 9, 9 of the double belt press 3.

"Effects of the Invention" As explained above, the present invention eliminates the need for post-curing treatment after cutting, and can economically produce a laminate with good dimensional accuracy without warping or waving.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the method of the present invention, and is a diagram showing a schematic configuration of an apparatus suitably used to carry out the method of the present invention. A...Base material, B...Thermosetting resin liquid, C...Metal foil, D...Product, 3...Double belt press,
4... Heating furnace, 9... Endless belt, 10...
...pressure chamber, 11...pressure medium, 12...cooling chamber.

Claims (1)

[Scope of Claims] 1. A thermosetting resin liquid that essentially does not require a drying process and that does not substantially generate reaction by-products such as gas or liquid during the curing reaction process is applied to a long base material. A continuous manufacturing method for a laminate comprising an impregnating step of impregnating the substrate, and a heating step of superimposing and heating a plurality of impregnated base materials to cure the resin liquid and integrate the resin liquid. partially impregnating the substrate with the liquid, and in the heating step, using a double belt press constituted by an endless belt having a substantially uniform pressure over the entire pressure zone,
While measuring the penetration of the partially impregnated resin liquid into the entire base material, heat and pressure is applied to continuously semi-cure the resin liquid to the extent that elastic recovery of the base material does not occur, and then heat harden continuously under no pressure. A method for continuously manufacturing a laminate, characterized in that: 2. The continuous production method of a laminate according to claim 1, wherein the laminate is a metal foil-clad laminate formed by laminating a plurality of substrates impregnated with metal foil at the same time or in a separate process. 3. A double belt press consisting of an endless belt that has a substantially uniform pressure over the entire pressure zone, has a pressurizing chamber with the endless belt as one constituent surface, and uses a fluid as a pressure medium. The continuous manufacturing method of a laminate according to claim 1, which is a press. 4. The continuous production method of a laminate according to claim 1, wherein the pressure in the heating and pressing step is in the range of 1 to 100 kg/ ^cm2 . 5. The method for continuously manufacturing a laminate according to claim 1, wherein the base material is paper. 6 A long base material is impregnated with a thermosetting resin liquid that essentially does not require a drying process and does not substantially generate reaction by-products such as gas or liquid during the curing reaction process, and is then bonded to metal foil. In a continuous manufacturing method for single-sided metal foil clad laminates in which multiple sheets of the resin liquid-impregnated base material are overlapped and heated to cure the resin liquid and integrate, after partially impregnating the base material with the resin liquid, , having a substantially uniform pressure throughout the cuff;
Using a double belt press consisting of an endless belt, heat and pressurize the partially impregnated resin liquid while measuring its penetration into the entire base material, and continuously apply the resin liquid to the extent that elastic recovery of the base material does not occur. 1. A method for continuously manufacturing a laminate, which comprises semi-curing, then continuously heating and curing under no pressure, followed by cooling, and then continuously correcting warpage of the laminate.