JP2000007793A - Production of sheet molding material and sheet molding material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing, in good yield, sheet molding materials high in the content of a metal oxide and free from shrinkage upon heat-drying. SOLUTION: A process for producing a sheet molding material by forming an aqueous slurry obtained by dispersing (A) a metal oxide, (B) a synthetic resin, (C) fibrillated organic fibers, and (D) inorganic fibers into water into a sheet, dehydrating and heat-drying the sheet comprises adding a cationic flocculating agent (Ea) and an anionic flocculating agent (Eb) at the time of preparing said aqueous slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sheet-shaped molding material having a high metal oxide content, which is particularly useful for electric and electronic equipment requiring electromagnetic shielding properties and heat radiation properties. It is.

[0002]

2. Description of the Related Art In recent years, in electric and electronic equipment applications, a high proportion of a metal oxide having excellent electromagnetic wave shielding properties and heat radiation properties is contained from the viewpoint of electromagnetic interference and miniaturization of a semiconductor substrate, and this is bonded with a synthetic resin. The emphasis has been placed on sheet-shaped molding materials that have been attached. It is known that production by a wet papermaking method (a method of papermaking an aqueous slurry), which is a papermaking technique, is advantageous for this type of sheet-shaped molding material.

[0003] However, in this wet papermaking method, the yield of the sheet product is reduced due to the fact that the metal oxide and the synthetic resin are easily separated and settled from the aqueous slurry, and the wet sheet product after the papermaking and dewatering shrinks during heating and drying. There was a problem that it easily occurred.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a sheet-shaped molding material having a high metal oxide content and preventing shrinkage during heating and drying with a high yield. It is an object of the present invention to provide an improved method, especially a wet papermaking method.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, when preparing an aqueous slurry for wet papermaking, an organic fiber fibrillated with a cationic coagulant and an anion were prepared. It has been found that the combined use of a system flocculant can suppress the separation and sedimentation of metal oxides and synthetic resins from aqueous slurries. Furthermore, they have found that shrinkage during heating and drying can be prevented by using inorganic fibers as an additional component, and have completed the present invention.

That is, the present invention provides an aqueous slurry in which at least a metal oxide (A), a synthetic resin (B) and a fibrillated organic fiber (C) are dispersed, formed into a sheet, dehydrated, and dried by heating to obtain a sheet. A method for producing a shaped molding material, comprising the steps of: preparing a water-based slurry;
a) and a method for producing a sheet-like molding material characterized by adding an anionic coagulant (Eb), and a sheet-like molding material produced by the method.

[0007] In the present invention, it is preferable to disperse the inorganic fibers (D) to form an aqueous slurry.

Further, a metal oxide (A) and a synthetic resin (B)
Is 60 to 85% by weight / 40 to 15% by weight, and the compounding ratio of the fibrillated organic fiber (C) is between the metal oxide (A) and the synthetic resin (B). It is preferably 1 to 8 parts by weight per 100 parts by weight in total.

The mixing ratio of the inorganic fibers (D) is preferably 1 to 5 parts by weight per 100 parts by weight of the total amount of the metal oxide (A) and the synthetic resin (B).

The amounts of the cationic coagulant (Ea) and the anionic coagulant (Eb) are different depending on the dispersoid (A)
Preferably, the amount is 0.5 to 2 parts by weight per 100 parts by weight of the total amount of (C) or the dispersoids (A) to (D).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION According to the production method of the present invention, an aqueous slurry is prepared by dispersing at least a metal oxide (A), a synthetic resin (B) and a fibrillated organic fiber (C). At this time, by further dispersing the inorganic fibers (D), it is possible to prevent shrinkage of the sheet-shaped molding material (wet body) during heating and drying, which is preferable.

The metal oxide (A) used in the present invention is appropriately selected according to the intended use and cannot be unconditionally limited. Examples thereof include ferrite, alumina, barium titanate, and titanium oxide. Among these, ferrite having excellent electromagnetic wave shielding properties and alumina having excellent heat dissipation properties are preferable, and ferrite is particularly preferable. Further, the metal oxide is hardly soluble or insoluble in water and has an average particle size of 10 from the viewpoint of wet papermaking.
Desirably, the powder has a size of 0 μm or less.

The synthetic resin (B) used in the present invention
Is a resin having a so-called binder function of mutually binding the metal oxide (A), the fibrillated organic fiber (C), the inorganic fiber (D), and other dispersoids. Thermosetting resin such as epoxy resin, unsaturated polyester resin, diallyl phthalate resin, polyimide resin, melamine resin, urea resin, urethane resin, thermoplastic resin such as polyethylene resin, polypropylene resin, polystyrene resin, vinylidene chloride resin, nylon resin Examples include resins and mixtures thereof. Of these, thermosetting resins are preferred in terms of heat resistance. From the viewpoint of wet papermaking, the synthetic resin (B) is preferably in the form of a powder or a fibrous material having an average particle diameter of 100 μm or less, which is hardly soluble or insoluble in water.

The component ratio (A / B) of the metal oxide (A) and the synthetic resin (B) is 60 to 85% by weight / 40 to 15% by weight.
And preferably 70 to 80% by weight / 30 to 20% by weight. If the compounding ratio of the metal oxide (A) is less than 60% by weight, it is not possible to meet the needs, and if it exceeds 85% by weight, strength and moldability deteriorate, which is not preferable.
If the compounding ratio of the synthetic resin (B) is less than 15% by weight, the moldability is deteriorated. On the other hand, if it exceeds 40% by weight, the content of the metal oxide (A) is relatively reduced to meet the needs. Can not do.

The fibrillated organic fiber (C) used in the present invention plays a role in inhibiting the sedimentation of the metal oxide (A) and the synthetic resin (B) in the aqueous slurry. Typical examples of the fibrillated organic fiber (C) having various functions include microfibrous cellulose and Cellish K in the case of a cellulose fiber system.
Y-100G (trade name, manufactured by Daicel Chemical Industries), CFF114-3, R-56 for polyacrylonitrile fiber
D (trade name, manufactured by Toyobo Co., Ltd.). In addition, the fibrillated organic fiber (C) means a so-called fibrillated organic fiber aggregate obtained by beating fibers such as polyacrylonitrile fiber and cellulose fiber into a desired degree of branch. .

The compounding ratio of the fibrillated organic fiber (C) is 10% of the total amount of the metal oxide (A) and the synthetic resin (B).
It is 1 to 8 parts by weight, preferably 1 to 5 parts by weight per 0 parts by weight. If the amount of the fibrillated organic fiber (C) is less than 1 part by weight, the metal oxide (A) and the synthetic resin (B)
The effect of preventing sedimentation and sedimentation is not sufficient. Conversely, if it exceeds 8 parts by weight, the drainage during papermaking decreases and productivity is deteriorated, which is not preferable.

The inorganic fiber (D) used in the present invention
Plays a role in preventing shrinkage of the sheet-shaped molding material (wet body) during heating and drying. Examples of such inorganic fibers include glass fiber, alumina fiber, rock wool fiber, carbon fiber, and titanium. Potassium whisker and the like, but are not limited thereto.

The mixing ratio of the inorganic fiber (D) is based on 100 parts by weight of the total amount of the metal oxide (A) and the synthetic resin (B).
It is 1 to 5 parts by weight, preferably 3 to 5 parts by weight. If the amount of the inorganic fiber (D) is less than 1 part by weight, the effect of preventing shrinkage is not sufficient, and if it exceeds 5 parts by weight, not only does the effect of preventing shrinkage remain unchanged, but also the content of metal oxide (A) decreases. It is not preferable because it causes a relative decrease.

In the present invention, a cationic coagulant (Ea) and an anionic coagulant (Eb) are used during the preparation of the aqueous slurry.
Is added.

As the cationic coagulant (Ea), for example, Filex RC104, Filex RC10
7 (trade name, manufactured by Meisei Chemical Co., Ltd.), Arafix 50
2, ALAFIX 530, ALAFIX 580 (trade name, manufactured by Arakawa Chemical Industry Co., Ltd.), 115CH, 102 (trade name, manufactured by Mitsui Toatsu Chemical Co., Ltd.) and the like. On the other hand, examples of the anionic coagulant (Eb) include, for example, Filex M (trade name, manufactured by Meisei Chemical Industry Co., Ltd.), Araflock A-1
85 (Minami product name, Arakawa Chemical Industry Co., Ltd.), 3100C, 31
50B (trade name, manufactured by Mitsui Toatsu Chemicals, Inc.) and the like.

The mixing ratio (Ea / Eb) of the cationic coagulant (Ea) and the anionic coagulant (Eb) is 95/5 to 5/95, preferably 80/50, based on weight.
20-20 / 80, more preferably 70 / 30-30 /
70. If the mixing ratio is out of the range of 95/5 to 5/95, the effect of improving the yield is not sufficient.

The amount of the aggregating agent is 0.5 to 2 parts by weight, preferably 0.5 to 2 parts by weight, per 100 parts by weight of the total amount of the dispersoids (A) to (C) or the dispersoids (A) to (D). It is about 1 part by weight. If the amount is less than 0.5 part by weight, the effect of improving the yield is not sufficient, and if it exceeds 2 parts by weight, drainage is deteriorated due to an increase in viscosity, which is not preferable.

The method for producing the sheet-like molding material according to the present invention is not particularly limited, but the wet papermaking method is preferable because it can contain a metal oxide in a high ratio and the thickness can be easily adjusted. Hereinafter, a specific method of the present invention will be described.

First, a metal oxide (A), a synthetic resin (B), a fibrillated organic fiber (C) and an inorganic fiber (A) are placed in a pulverizer / beater (for example, pulper, beater, Henschel mixer) containing a large amount of water. D) If necessary, after adding a dispersant, high-speed stirring and mixing are performed to form a slurry. Next, after transferring the obtained aqueous slurry into a mixing tank with a stirring blade, various additives such as a curing agent, a curing accelerator, a flame retardant, a plasticizer, a release agent, and a coloring agent are added as necessary. . Then
Coagulants (Ea and Eb) are added and mixed at low speed with stirring to obtain an aqueous slurry for papermaking having a concentration of about 0.01 to 10%. Next, the aqueous slurry for papermaking is formed into a sheet-shaped wet molding material having a desired size by, for example, a continuous net or cylindrical continuous or batch-type papermaking machine, and is dehydrated by filtration, decompression, squeezing, or the like, and is then dried. For example, the sheet-shaped molding material can be obtained by drying with a drum-type dryer, a hot-air ventilation dryer, a dielectric heating dryer, a far-infrared ray dryer, or a reduced-pressure dryer.

[0025]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples.

The yield (%) of the sheet-shaped molding material is 10% of the total amount of the components (A) to (C) or (A) to (D).
It is the ratio of the product yield (weight) after drying to 0 parts by weight. The shrinkage rate (%) of the sheet-shaped molding material is the ratio of the area after drying to the area before drying when dried in a hot air circulating drier (set temperature: 80 ° C.).

Example 1 Water 3 in a Henschel mixer
Liter, ferrite powder 21g (average particle size 2.7μ)
m), 4.6 g of o-cresol novolak type epoxy resin powder, 2.0 g of novolak type phenol resin powder,
Fibrillated polyacrylonitrile fiber (trade name C
FF114-3, manufactured by Toyobo Co., Ltd.) and 0.09 g of an appropriate amount of an anionic dispersant were charged and stirred at high speed to form a slurry. Next, the obtained slurry was transferred into a mixing tank with stirring blades, and then 0.14 g of a cationic coagulant (trade name: Filex RC104, manufactured by Meisei Chemical Industry Co., Ltd.) and 0.1 g of a flocculant were added.
90 g of an anionic coagulant (trade name: Filex M,
(Meisei Chemical Industry Co., Ltd.) and stirred and mixed at a sufficiently low speed to obtain a 1% by weight aqueous slurry for papermaking.

Next, this aqueous slurry for papermaking was applied to a standard square sheet machine (a laboratory paper machine manufactured by Toyo Seiki, papermaking net 100).
The whole amount was poured into a mesh (250 mm in length × 200 mm in width), filtered, and subjected to suction compression dehydration to obtain a wet sheet-shaped molding material. Next, this was dried in a hot air circulating drier at 80 ° C. to prepare a 0.5 mm thick sheet-shaped molding material (230 mm long × 180 mm wide).

The obtained sheet-shaped molding material was uniform without dispersion unevenness, and had a yield of 96% and a shrinkage of 20%. Table 1 shows the results.

Example 2 A sheet-like molding material was produced in the same manner as in Example 1, except that 1.4 g of glass fiber (diameter 9 μm × length 3 mm) was further used.

The obtained sheet-like molding material was uniform without dispersion unevenness, and had a yield of 95% and a shrinkage of 0%. Table 1 shows the results.

(Examples 3 to 8) Six kinds of sheet-like materials were prepared in the same manner as in Example 2 except that the mixing ratio of the cationic flocculant and the anionic flocculant was changed as shown in Table 1. A molding material was prepared. With respect to the obtained sheet-like molding material, the yield, the measurement of shrinkage, and the presence or absence of dispersion unevenness were examined. Table 1 shows the results.

Example 9 A sheet-like molding material was produced in the same manner as in Example 2, except that the ferrite powder was changed to alumina powder (average particle size: 3 μm). In addition, the obtained sheet-shaped molding material was uniform without dispersion unevenness, and had a yield of 96% and a shrinkage of 0%. Table 1 shows the results.

Example 10 A sheet was formed in the same manner as in Example 2 except that o-cresol novolak type epoxy resin powder and novolak type phenol resin powder were changed to benzylic ether type phenol resin powder. Materials were made. In addition, the obtained sheet-shaped molding material is uniform without dispersion unevenness, and the yield is 96%.
The shrinkage was 0%. Table 2 shows the results.

Comparative Example 1 A sheet-like molding material was produced in the same manner as in Example 2 except that no coagulant was used. In addition, dispersion unevenness was confirmed in the obtained sheet-shaped molding material, and the yield was 50% and the shrinkage was 0%. Table 2 shows the results.

Comparative Example 2 A sheet-like molding material was prepared in the same manner as in Example 2 except that the cationic coagulant and the anionic coagulant were not used in combination and only the cationic coagulant was used. did. Dispersion unevenness was confirmed in the obtained sheet-like molding material, and the yield was 67% and the shrinkage was 0%.
Met. Table 2 shows the results.

Comparative Example 3 A sheet-like molding material was produced in the same manner as in Example 2, except that the fibrillated polyacrylonitrile fiber was not used.
In addition, dispersion unevenness was confirmed in the obtained sheet-like molding material, and the yield was 62% and the shrinkage was 0%. Table 2 shows the results.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

As described above, according to the present invention,
By using fibrillated organic fibers and two types of flocculants (anionic flocculant and cationic flocculant),
A sheet-shaped molding material having a high content of a metal oxide and having no dispersion unevenness can be obtained with a high yield. Further, by further forming inorganic fibers, it is possible to obtain a sheet-shaped molding material having a high content of the metal oxide and having no dispersion unevenness and no shrinkage.

Claims (6)

[Claims] An aqueous slurry comprising at least a metal oxide (A), a synthetic resin (B) and a fibrillated organic fiber (C) dispersed therein is formed, dewatered, and dried by heating to obtain a sheet-shaped molding material. A method for producing a sheet-like molding material, wherein a cationic coagulant (Ea) and an anionic coagulant (Eb) are added during the preparation of the aqueous slurry. 2. The method for producing a sheet-like molding material according to claim 1, wherein the aqueous slurry is formed by dispersing the inorganic fibers (D). 3. The composition ratio (A / B) of the metal oxide (A) and the synthetic resin (B) is 60 to 85% by weight / 40 to 15% by weight.
And the compounding ratio of the fibrillated organic fibers (C) is 10 in total of the metal oxide (A) and the synthetic resin (B).
The method for producing a sheet-like molding material according to claim 1 or 2, wherein the amount is 1 to 8 parts by weight per 0 parts by weight. 4. The compounding ratio of the inorganic fiber (D) is 1 to 5 parts by weight per 100 parts by weight of the total amount of the metal oxide (A) and the synthetic resin (B). 4. The method for producing a sheet-shaped molding material according to item 1. 5. The addition amount of the cationic flocculant (Ea) and the anionic flocculant (Eb) is 100 total weight of the dispersoids (A) to (C) or the dispersoids (A) to (D). The amount is 0.5 to 2 parts by weight per part.
4. The method for producing a sheet-shaped molding material according to item 1. 6. A sheet-shaped molding material produced by the production method according to claim 1.