JPH05106191A - Heat-resistant sheet and its production - Google Patents

Abstract

PURPOSE:To obtain a sheet excellent in electrical properties, heat resistance etc., useful for printed wiring boards by specifically interlacing specific aromatic polyamide staple fibers, a microfibrillated product of aromatic polyamide and pulpy aromatic polyamide. CONSTITUTION:A slurry containing (A) staple fibers of an aromatic polyamide with the main chain bearing aromatic groups (pref. poly-p-phenylene terephthalamide 1-6 denier in single fiber fineness and >=5mm in fiber length), (B) a microfibrillated product of an aromatic polyamide (fibrillated to <=0.7mum in single fiber diameter) and (C) a pulpy aromatic polyamide >=0.7mum in fiber diameter, is prepared and put to wet paper making process into a web. One or more of these webs are laminated and interlaced using a water stream in a three-dimensional fashion, thus affording the objective sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant sheet having excellent electrical properties, heat resistance and dimensional stability, and particularly to a heat-resistant sheet suitable for printed wiring boards and a method for producing the same.

[0002]

2. Description of the Related Art Generally, a printed wiring board is constructed by laminating a metal foil such as a copper foil on an electric insulating sheet with or without a heat-resistant adhesive. It is obtained by forming. Since the insulating sheet used for this is required to have excellent properties such as heat resistance and dimensional stability, a heat resistant resin film such as a polyimide film, a dry or wet nonwoven fabric in which heat resistant synthetic fibers are bound with a binder, It is known that a mixture of heat-resistant synthetic pulp and heat-resistant synthetic fiber or glass cloth or glass paper impregnated with a heat-resistant resin and cured is selected and used according to the required performance or cost. ..

[0003]

However, although the polyimide film has good heat resistance,
It has the disadvantages of poor dimensional stability and high cost.

Further, in dry or wet papermaking, a binder is required to obtain a thin sheet having excellent strength to withstand the resin impregnation step. At this time, even if the main fiber has excellent heat resistance, there is a drawback that the binder is inferior in heat resistance, and in order to obtain strength that does not hinder the resin impregnation step, a large amount of binder is required,
There is a drawback that the resin content is reduced. Further, although glass cloth and glass paper are excellent in resin impregnation property, they have a drawback that the dimensional stability of the resin cured sheet is poor.

As the heat-resistant synthetic fibers, aromatic polyamide short fibers, especially para-type fibers, are excellent in heat resistance and dimensional stability, and sheets mainly composed of the fibers have been proposed.
As a binder for the fibers, low orientation polyester short fibers are used (Japanese Patent Laid-Open No. 62-274689 and Japanese Patent Laid-Open No. 62-2626), microfibrillated thermoplastic polymers and aramid-based pulp (aramid fibers (Milled and fibrillated or fibrid)
(Japanese Patent Laid-Open No. 63-35900), those using a fibrous binder of aramid fibrous binder (pulp-like aromatic polyamide) and thermoplastic heat-resistant polymer (Japanese Patent Laid-Open No. 61-170089). JP-A-60-26062
No. 6) is disclosed. Polyester is inferior in heat resistance and dimensional stability to aromatic polyamide, and thermoplastic polymer is also inferior in heat resistance and dimensional stability, which is not preferable.

In addition, short fibers of para-aromatic polyamide or fibrillated products thereof, or either one of them,
Further, there is disclosed one using a fibrid of a meta-aromatic polyamide (JP-A-60-207216), but a meta-aromatic polyamide having poor heat resistance and dimensional stability as compared with a para-aromatic polyamide. Is used, which is not preferable.

Further, the conventional nonwoven fabrics have a drawback that they are excellent in dimensional stability in the longitudinal and transverse directions but inferior to woven fabrics in dimensional stability in the thickness direction.
This is because the fibers can be arranged two-dimensionally, but it is difficult to arrange them in the thickness direction by the conventional method.

As an example of three-dimensionally entangled webs of aromatic polyamide fibers, 1985 Tappi Nonwoven Sym
The posium essential point describes a method of interlacing using a web formed by the air laying method. This sheet also has high strength and takes advantage of the heat resistance of the fiber, and has excellent performance as a flameproof sheet. However, the web obtained by the air-laid method is inferior in terms of formation as compared with the wet method. Further, it is difficult to mix fine fibers and the surface quality is poor.

The present invention solves the above-mentioned problems of the prior art, and is a sheet suitable not only for heat resistance but also for electrical characteristics and dimensional stability, especially for printed wiring boards.
The purpose is to provide

[0010]

[Means for Solving the Problems] The inventors of the present invention have made extensive studies to solve the above problems. As a result, by using an aromatic polyamide short fiber having an aromatic group in the main chain and an aromatic polyamide microfibrillated product, a uniform heat resistant sheet is obtained with less fluctuation in basis weight and unevenness of the formation. It was found. Further, it was found that the same effect can be obtained by blending an aromatic polyamide pulp-like material in combination with the above microfibrillated product. In addition, the heat-resistant resin is uniformly impregnated to ensure dimensional stability,
In particular, it has been found that a heat-resistant sheet having excellent dimensional stability in the thickness direction can be obtained. The present invention has been achieved based on the above findings.

That is, two components consisting of an aromatic polyamide short fiber having an aromatic group in the main chain and a microfibrillated product of an aromatic polyamide fibrillated to a fiber diameter of 0.7 μm or less, or a fiber diameter of the two components. Is 0.7μ
A heat-resistant sheet containing three components made of a pulp-like aromatic polyamide having a size larger than m, and these two components or three components being three-dimensionally entangled. Further, it is the above heat resistant sheet containing a heat resistant resin.

Further, two components comprising aromatic polyamide short fibers having an aromatic group in the main chain and microfibrillated aromatic polyamide fibrillated to a fiber diameter of 0.7 μm or less, or a fiber diameter of the two components. Having a particle size of more than 0.7 μm, a slurry containing three components made of a pulp-like aromatic polyamide is prepared, and a web formed by a wet papermaking method is laminated in a single layer or a plurality of layers and entangled with a water stream. Is a manufacturing method. Furthermore, it is a method for producing a heat-resistant sheet, characterized by impregnating with a heat-resistant resin before or after hydroentanglement, drying, and curing after hydroentanglement.

The present invention will be described in detail below. The aromatic polyamide having an aromatic group in the main chain used in the present invention is an aromatic dicarboxylic acid or its acid chloride or an aromatic dicarboxylic acid and its acid chloride, and a homopolymer or a copolymer containing an aromatic diamine as a main component. .. The aromatic dicarboxylic acid and the aromatic diamine can take a meta form and a para form, respectively. The para-form is preferable from the viewpoint of excellent dimensional stability of the obtained sheet, and specific examples thereof include poly-P-phenylene terephthalamide or poly-P-phenylene.3,4'diaminodiphenyl ether.terephthalamide.

The aromatic polyamide short fibers used in the present invention preferably have a fineness of 1 to 6 denier (hereinafter abbreviated as d) and a fiber length of 5 mm or more. If the fiber length is shorter than 5 mm, the entanglement is difficult.

The aromatic polyamide microfibrillated product used in the present invention, as disclosed in Japanese Patent Laid-Open No. 56-100801, is different from the treatment by a refiner used in a general papermaking process, and is a homogenizer. Is microfibrillated using. That is, when a slurry of aromatic polyamide fibers dispersed in water is passed through an orifice provided with a pressure difference of 200 kgf / cm ² or more at a high speed before and after the slurry is rapidly decelerated, a shearing force is applied to the slurry particles. , Aromatic polyamide fibers are vertically divided into microfibrils in the fiber axis direction. It is a product obtained by repeating this process. As a specific example, there is a Tiara 400 (manufactured by Daicel), which is a microfibrillated para-aromatic polyamide fiber (Kevlar fiber, manufactured by DuPont).

The pulp-like aromatic polyamide used in the present invention is a pulp-like substance composed of an aromatic polyamide polymer, preferably a fiber fibrillated product or fibrid.
The fibrillated material means fibrils generated by grinding fibers. Fibrids refer to fiber fibrils and particles obtained by the method disclosed in Japanese Examined Patent Publication No. 40-9044, which are dropped from a polymer solution into a polymer coagulant under high shear to coagulate and precipitate.

The above-mentioned microfibrillated product has a fine fiber diameter which cannot be obtained by grinding or fibrating the fibers. That is,
Since the microfibrillated product has a very fine fiber diameter of 0.7 μm or less, even in the slurry, the microfibrillated product is entangled with the main fibers to prevent the formation of flocs (aggregation of fibers) and to make the fiber uniform. Slurry can be prepared,
It is possible to obtain a sheet having a good texture and having less fluctuation in the basis weight and unevenness in the thickness of the sheet after papermaking. Further, since the entanglement between the fibers is large, the strength of the wet paper after papermaking is large, the effect as a binder of the sheet is remarkable even after drying, and the handling of the sheet after papermaking is easy.

When the sheet after papermaking is three-dimensionally entangled,
Not only it is possible to obtain a sheet having a high degree of entanglement between fibers and high strength, but the microfibrillated product improves the smoothness of the sheet surface after entanglement. further,
Filled between the short fibers, the sheet becomes dense.

On the other hand, the pulp-like material has a larger fiber diameter than the microfibrillated product, and cannot independently form a papermaking sheet having a higher strength than the microfibrillated product. Is difficult to transition. Rather, there is an advantage that the yield of the microfibrillated product can be improved by mixing it with the short fiber of the aromatic polyamide and the slurry of the microfibrillated product.

Further, aromatic polyamide has excellent heat resistance,
Inorganic fillers and inorganic fibers may be mixed as long as they are dimensionally stable but do not impair these functions.

The sheet is prepared by uniformly dispersing and mixing the aromatic polyamide short fibers and the microfibrillated product, forming a web by an ordinary paper machine, three-dimensionally interlacing the fibers with a high-pressure columnar water stream, and drying. can get. If necessary, it can be pressed with a calender or the like under heating or without heating to obtain a dense and smooth sheet.

The amount of the aromatic polyamide microfibrillated product is 5% to 40%, more preferably 10% to 40%, based on the weight of the sheet. If it is less than 5%, the strength of the paper sheet will be reduced, making it difficult to handle the paper sheet.
The strength at the time of entanglement is also weak, and the sheet is cut when impregnated with resin. When it is more than 40%, the drainage property at the time of papermaking is deteriorated, which is not preferable in the papermaking process.

The pulp-like aromatic polyamide is mixed in order to improve the yield of the microfibrillated product of the aromatic polyamide, and the amount of the pulp-like aromatic polyamide is
It is preferably 3% to 30% with respect to the weight of the sheet. Pulp-like aromatic polyamide has a low function as a binder as compared with a microfibrillated product, and is less effective when used alone, but when used in combination with a microfibrillated product, not only as a binder, but also during papermaking, and There was also an effect of improving the yield of the microfibrillated material in the sheet in the confounding step. At this time, the total amount of the pulp-like material and the microfibrillated material is 8% to 60% of the sheet weight.
And preferably 10% to 50%. If it is less than 8%, the strength of the papermaking sheet decreases, the handling of the papermaking sheet is difficult, the strength at the time of entanglement is weak, and the sheet is cut at the time of resin impregnation. If it is more than 60%, the drainage is poor, which is not preferable. If necessary, this pulp-like material may be beaten with a beater and used.

Next, the conditions for firmly and properly performing the three-dimensional entanglement will be described. A single layer or a plurality of the above-mentioned sheets are laminated and placed on a support of about 50 to 200 mesh, and a water stream is injected from above to perform three-dimensional entanglement of fibers.

The diameter of the nozzle for injecting the water stream to entangle the fibers is preferably in the range of 10 to 500 μm in order to perform the entanglement firmly and keep the texture well. The distance between the nozzles is preferably 10 to 1500 μm.

These nozzles are used for web, sheet type,
In consideration of the basis weight, processing speed, and water pressure, the number of nozzle heads can be changed and used within a range where sufficient entanglement can be obtained. Also, the number of confounding can be arbitrarily selected.

The water pressure can be used in the range of 10 to 250 kg / cm ² , but the aromatic polyamide has a large fiber rigidity, and it is preferable to perform the entanglement at a water pressure higher than usual.
In this case, 50 to 250 kg / cm ² is a preferable range. The processing speed can be used in the range of 15 to 200 m / min. If the confounding water pressure is low, sufficient confounding cannot be obtained. Also, if the water pressure is higher than necessary, the formation will be disturbed,
The sheet is damaged, which is not preferable.

The water pressure does not hinder the surface quality by gradually increasing the pressure from the initial stage to the final stage of processing.
Strong confounding is possible. Further, it is possible to successively reduce the nozzle diameter and the nozzle interval, or either one, which is also preferable in that the surface quality of the nonwoven fabric is improved.
It is also possible to further improve the surface quality by rotating the header of the nozzle, vibrating it to the left or right, or vibrating the support wire of the web to the left or right. Further, after the entanglement, between the nozzle and the web, 40 ~
It is also possible to improve the surface quality by inserting a 100-mesh wire net and sprinkling the columnar water stream to spray it onto the web. Further, the surface quality can be easily improved by decreasing the water pressure immediately before the end of the confounding, or immediately before and two rows before.

As a method of entanglement, only one side or both sides can be entangled. It is also possible to further entangle by stacking sheets after the entanglement.

During or after the three-dimensional entanglement treatment as described above, excess water is removed by suction or a wet press, and then dried using an air dryer, an air through dryer, a suction drum dryer or the like. be able to.

Examples of the heat-resistant resin used in the present invention to be impregnated include thermosetting resins such as thermosetting polyesteramide resin, epoxy resin, phenol resin, and polyimide resin, which may be used alone or in combination of two or more. Are mixed and used. Moreover, the thing which mix | blended the inorganic filler as needed can be used.

Next, a method for forming a printed wiring board sheet will be described. A sheet obtained by drying after papermaking, or a sheet obtained by entanglement is impregnated with a thermosetting resin,
After drying the solvent, the resin may be cured. For impregnation of the resin solution, a commonly used horizontal or vertical impregnation machine can be used. Drying after impregnation does not require any special means. If the impregnated sheet during drying has tackiness, a release sheet may be optionally used in an appropriate step. If the impregnated sheet has already been entangled, a plurality of the above-mentioned impregnated sheets can be superposed, heated and pressed to be integrated, and further cured.

In the case of a paper-making dried sheet, after impregnating with a resin, drying and further laminating, the resin-impregnated sheets are entangled with each other, or with the paper-making dried sheet, the entangled sheet, etc., and further impregnated with a necessary amount of resin It is possible.

To further laminate the metal foil on the heat-resistant sheet of the present invention, it is possible to laminate with an adhesive resin interposed therebetween. However, without using an adhesive, before the sheet completely completes the curing reaction, The metal foil may be directly attached and then cured.

It is also possible to laminate and integrate with a woven or knitted fabric made of aromatic polyamide fiber.

[0036]

The heat-resistant sheet of the present invention is a sheet in which microfibers of aromatic polyamide are used for aromatic polyamide short fibers having an aromatic group in the main chain, and the fibers are three-dimensionally entangled. A sheet impregnated with a heat-resistant resin and cured by taking advantage of the characteristics of aromatic polyamide effectively acts as a printed wiring board excellent in electrical characteristics, heat resistance, dimensional stability, and particularly dimensional stability in the thickness direction.

[0037]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. All parts and percentages mentioned in the examples are by weight.

The physical property measuring methods used in the examples and comparative examples are as follows. Regarding the sheet after paper making, (1) basis weight, (2) a sheet having 150 mm and 20 mm as strength in the papermaking direction (longitudinal) and the direction perpendicular to the papermaking direction (horizontal) was prepared, span 10 cm, pulling speed At 20 cm / min, the maximum load until breakage of the sample piece was measured. After resin impregnation and hot-pressing (1) Dimensional change rate (coefficient of thermal expansion) The resin-impregnated and hot-pressed sample was subjected to IPC FC241 method to determine the dimensional change rate before and after the treatment at 150 ° C for 30 minutes. (2) Solder resistance Swelling according to JIS C6481 and color change were observed.

Example 1 50 mol% of terephthalic acid dichloride and 50 mol% of paraphenylenediamine were mixed with hexamethylsulforamide (H
Low temperature solution polymerization was carried out in a mixed solvent of MPA) and N-methylpyrrolidone (NMP), and the generated acid was neutralized with lithium hydroxide. After washing, the isolated polymer of poly-P-phenylene terephthalamide was dissolved in 20% by weight sulfuric acid,
After heating to ℃, spinning. At this time, the solution was discharged from a nozzle through an air layer of 1 cm into a low temperature coagulation bath to form fibers. The tow with a fineness of 2d thus obtained was cut into a fiber length of 20 mm to obtain aromatic polyamide short fibers. 80 parts of this short fiber is pre-dispersed at a concentration of 0.5%,
20 parts of a poly-P-phenylene terephthalamide microfibrillated product (Tiara 400, manufactured by Daicel Chemical Co., Ltd.) was added to a pre-dispersed aqueous solution, high-molecular polyacrylamide (sticky agent) was added, and the mixture was further stirred and diluted with water, The slurry was adjusted. Using this slurry, a sheet having a basis weight of 50 g / m ² was made into paper by a cylinder paper machine and dried.

The sheet after papermaking is made of reinforced polyester 1
A 00 mesh support is placed on top and under the following water flow, 3
Dimensional confounding was performed. Five nozzle heads were used. The nozzle of the first head has a nozzle diameter of 120 μm, the nozzle interval is 1.2 mm, the water pressure is 100 kgf / cm ^{2 in} two rows, and the second head has a nozzle diameter of 120 μm, the nozzle interval is 1.2 mm, and the water pressure is 1 in two rows.
30 kgf / cm ² , No. 3 head, nozzle diameter 120 μm, nozzle spacing 0.6 mm, water pressure 150 kgf / cm ^{2 in} 2 rows, No. 4 head, nozzle diameter 100 μm, nozzle spacing 0.6 mm, water pressure 140 kgf / cm ^{2 in} 1 row , No. 5 head has a nozzle diameter of 100μ
m, nozzle spacing 0.6 mm, water pressure 100 kgf / cm ² in one row. The entanglement was done with the pulp layer facing up first. Next, the same treatment was performed on the back surface. The entanglement speed was 10 m / min. This entangled sheet was dried at 130 ° C using a suction through dryer to obtain a sheet. Table 1
The measurement results are shown in.

Example 2 70 parts of the short fibers of Example 1 and 20 parts of the microfibrillated product were further added with 10 parts of a pulp-like aromatic polyamide (Kevlar pulp, manufactured by DuPont) to prepare a sheet. The entanglement was performed under the same conditions as in Example 1 below. The results are shown in Table 1.

Example 3 50 mol% of terephthaloyl chloride, 25 mol% of paraphenylenediamine, and 25 mol% of 3,4'-diaminodiphenyl ether were subjected to low temperature solution polymerization in NMP to obtain polyparaphenylene-3,4'-diaminopenic acid. A polymer of luther terephthalamide was obtained. The acid generated was neutralized with calcium hydroxide. Dilute the polymerization stock solution to 10% by weight,
Using a solution in which 1.5% by weight of calcium chloride was added and stabilized, the solution was discharged into an aqueous coagulation bath containing 50% by weight of calcium chloride as a solubilizing agent to be fiberized. Further, the solvent was removed, washed, dried, and stretched and heat-fixed at 500 ° C. 10 times. The tow with a fineness of 1.5d thus obtained was cut into a short fiber having a fiber length of 15 mm. The sheet was made into paper and entangled in the same manner as in Example 1. The results are shown in Table 1.

Example 4 The tow of Example 3 was cut into 3 mm and beaten with a Niagara type beater to produce a pulp-like aromatic polyamide. This pulp was further mixed with the ingredients of Example 3 to give Example 2
The sheet was made into paper and entangled in the same manner as in (1). Table 1
The results are shown in.

Comparative Example 1 A papermaking sheet was produced in the same manner as in Example 2. However, no confounding process was performed. The results are shown in Table 1.

[0045]

[Table 1]

From the above results, it can be seen that the sheet of the present invention is extremely excellent in strength. Further, even with the same composition, the sheet which is not entangled is inferior in strength.

Examples 5 to 8 The sheets obtained in Examples 1 to 4 were bismuth rayimide-containing.
Impregnate a triazine resin (BT resin, manufactured by Mitsubishi Gas Chemical Co., Inc.) in a methyl ethyl ketone solution (solid content concentration 60%),
Excess resin was squeezed with a glass bar to even out the resin adhesion. After drying at 145 ° C. for 8 minutes, four sheets were laminated and thermocompression molded at 175 ° C. and 20 kgf / cm ² for 1 hour to obtain a heat resistant sheet. The results are shown in Table 2.

Comparative Example 2 The papermaking sheet of Example 1 was impregnated with resin. The method was the same as in Examples 5-8. The results are shown in Table 2.

Example 9 90 parts of the same short fibers as in Example 1, microfibrillated material 1
The sheet was made into paper using 0 part. An epoxy resin solution consisting of 100 parts of an epoxy resin (Epicoat 1001, manufactured by Yuka Shell Co., Ltd.), 6 parts of dicyanamide, 0.4 part of benzyldimethylamine and 67 parts of methyl ethyl ketone was prepared,
Further, it was impregnated with a solution diluted 20 times with methyl ethyl ketone and dried at 120 ° C. for 10 minutes. The resin adhesion amount was 2% by weight with respect to the sheet weight. Two layers of this sheet were laminated and entangled in the same manner as in Example 1. However, the water pressure is 130, 150 in order from the first head to the fifth head,
It was conducted at 180, 160 and 100 kgf / m ² . Further, it was impregnated with the resin before dilution, dried at 120 ° C. for 10 minutes, then laminated four sheets, and thermocompression molded at 170 ° C. and 20 kgf / cm ² for 1 hour to obtain a heat resistant sheet. The results are shown in Table 2.

Comparative Example 3 Using 50 parts of the short fibers of Example 1 and 50 parts of the pulp-like aromatic polyamide of Example 2, an attempt was made to obtain a paper sheet.
This sheet strength is very weak and difficult to handle, and an attempt was made to further impregnate a resin and thermocompression molding, but the resin-impregnated sheet was damaged by the press and a heat resistant sheet could not be obtained. It was

Comparative Example 4 Using a card machine, a sheet containing only aromatic polyamide short fibers was prepared, laminated with a cross wrapper, and continuously hydroentangled. The water pressure is the same as in Example 1. When this sheet was held with transmitted light and observed, a mottled pattern was observed and it was found that the texture was poor. Also, if you push the sheet vertically with your hands, you can feel the unevenness and unevenness. This sheet was impregnated with resin in the same manner as in Examples 5 to 8 to obtain a heat resistant sheet. The results are shown in Table 2.

[0052]

[Table 2]

From Table 2, it can be seen that the heat-resistant sheet of the present invention exhibits excellent dimensional stability not only in the vertical and horizontal directions but also in the thickness direction. On the other hand, the sheet which is not entangled has poor dimensional stability in the thickness direction, and the one obtained by the dry method is
The dimensional stability of the entire sheet is poor.

[0054]

The present invention comprises a microfibrillated product of the same aromatic polyamide as the aromatic polyamide short fibers.
It is a dimensionally entangled sheet. Further, it is a sheet further containing a pulp-like aromatic polyamide. This sheet shows great strength and is easy to handle. further,
A sheet impregnated with a heat resistant resin and cured is a heat resistant sheet useful as an electrical insulating layer of a printed wiring circuit board. That is,
It has excellent heat resistance and dimensional stability, especially in the thickness direction. Therefore, it is very preferable in terms of fine circuit design.

Claims (4)

[Claims] 1. A two-component comprising an aromatic polyamide short fiber having an aromatic group in the main chain and a microfibrillated aromatic polyamide fibrillated to a fiber diameter of 0.7 μm or less, or a fiber diameter of the two components. Is a heat-resistant sheet containing three components made of a pulp-like aromatic polyamide having a size of more than 0.7 μm, and these two components or three components being three-dimensionally entangled. 2. The heat-resistant sheet according to claim 1, which contains a heat-resistant resin. 3. A two-component comprising an aromatic polyamide short fiber having an aromatic group in the main chain and a microfibrillated aromatic polyamide fibrillated to a fiber diameter of 0.7 μm or less, or a fiber diameter of the two components. Having a particle size of more than 0.7 μm, a slurry containing three components made of a pulp-like aromatic polyamide is prepared, and a web formed by a wet papermaking method is laminated in a single layer or a plurality of layers and entangled with a water stream. Manufacturing method. 4. The method for producing a heat-resistant sheet according to claim 3, wherein the heat-resistant resin is impregnated before or after hydroentanglement, dried, and cured after hydroentanglement.