JPH06342609A - Aramid nonwoven fabric and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a tissue paper form aramid nonwoven fabric having heat resistance, flexibility and cushion property so on and having less heat shrinkage under high temperature and good fluff loosing and superior surface flattability. CONSTITUTION:In a heat pressure treated aramid nonwoven fabric, weighting is 50g/m<2> or less, bulk density is 0.45g/m<2> or less, heat shrinkage percentage after heat treated at 300 deg.C for 10 minutes is 2.2% or less and fluff loosing numbers from one side or both sides are 10/10cm<2> or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cushion material and a spacer material used in a pressing process of an electric insulating material, a manufacturing process of a printed circuit board, etc., in which a fine damage on a surface portion and appearance quality are particularly important. It is a thing.

[0002]

2. Description of the Related Art With the recent refinement of electric and electronic equipment and the rapid development of technology, the required quality for electric insulation materials and printed circuit board materials used in these equipment is becoming more and more precise and strict. However, slight surface damage and adhesion of foreign substances are not allowed, and in addition, high surface smoothness is required. Conventionally, in the molding process of these electric insulating materials and the manufacturing process of printed circuit boards, a non-woven fabric made of aramid short fibers having relatively low heat shrinkage, heat resistance, flexibility, thinness and cushioning property, for example, DuPont Co., Ltd. Spunlaces (Nomex spunlaces) made of polymetaphenylene isophthalamide fiber are widely used.

However, although this Nomex spunlace (nonwoven fabric) is rich in heat resistance, flexibility, thinness, cushioning properties, etc., its heat shrinkage at high temperature is rather large.
In addition, fluffy fibers are easily removed from the surface (poor fluff removal property) and the surface is also poor in smoothness. However, various problems such as the transfer of particles, the occurrence of slight damage, and the attachment of fluff-like foreign matter occur, and there is a problem of a decrease in production yield in the manufacturing process. This improvement has been desired by the market.

Further, Japanese Patent Publication No. 61-30064 discloses an aramid felt and a method for producing the same. A nonwoven fabric produced by this method has excellent heat resistance and cushioning property, but heat shrinkage at high temperature. Is large and fluffy fibers are easily removed from the surface (poorness of fluff removal is poor), and since the surface is poor in smoothness, a minute uneven pattern may be transferred to the surface of the product on the other side. The quality is not satisfactory.

Further, a thin paper obtained by heating and pressurizing a wet paper formed by a wet papermaking method from an aqueous slurry composed of a mixture of aramid short fibers and aramid pulp has been disclosed (JP-A-4-6708). However, although this electrical insulating paper is rich in heat resistance, flexibility and thinness, the short fiber length of the short fibers makes it easy for the fluff to come off, and since it uses pulp, it has a high bulk density and poor cushioning properties. In addition, since the heat shrinkage rate is high, not only the characteristics required in the manufacturing process cannot be satisfied, but also the manufacturing cost becomes high.

As a result of intensive studies to solve the above problems, the present inventors have found that when a low basis weight non-woven fabric made of aramid fiber is heated and pressed under specific conditions, it has the surface smoothness required by the market. The inventors have found that it is possible to obtain a thin paper which has a good fluff removal property and a small heat shrinkage ratio, and has completed the present invention. The present invention will be described in detail below.

[0007]

OBJECT OF THE INVENTION The object of the present invention is a thin paper-like aramid fiber non-woven fabric which is excellent in heat resistance, flexibility, cushioning properties, etc., has little heat shrinkage at high temperatures, and has good fluff removal property and excellent surface smoothness. To provide.

[0008]

That is, according to the present invention, "(Claim 1) The aramid nonwoven fabric obtained by hot pressing has a basis weight of 50 g /
m ² or less, bulk density of 0.45 g / m ² or less, thermal shrinkage of 2.2% or less after heat treatment at 300 ° C. for 10 minutes, and number of fluffs removed from one side or both sides of 10/10 cm ²
An aramid non-woven fabric characterized by being:

(Claim 2) The aramid fiber is a polymetaphenylene isophthalamide fiber. The aramid non-woven fabric according to claim 1. (Claim 3) The aramid non-woven fabric has a temperature of 270 to 330.
A method for producing an aramid nonwoven fabric, which comprises hot-pressing at a temperature of 150 to 250 kg / cm.

(Claim 4) The method for producing an aramid non-woven fabric according to claim 3, wherein the aramid non-woven fabric is spun lace entangled with a water jet of high pressure and high speed flow. It is.

The aramid referred to here is an aromatic polyamide and an aromatic polyamide-imide. The aromatic polyamide is a conventionally known meta-type aromatic polyamide, para-type aromatic polyamide, or a copolymerized aromatic polyamide thereof.

The fiber used in the present invention comprises about 2 aramid fibers.
It is a short fiber or a continuous long fiber cut into about 5 to 80 mm, preferably about 45 to 65 mm. As the aramid fiber, a polymetaphenylene isophthalamide fiber is particularly preferable, but the aramid fiber is not limited thereto. If necessary, other fibers such as polyparaphenylene terephthalamide type may be mixed in an appropriate amount. The single yarn fineness of the fiber is 10.0 denier or less, more preferably 0.5 to 4.5 denier. The method for producing the nonwoven fabric in the present invention is not limited to a particular method. It can be obtained by entanglement of a web obtained by a conventionally known method, for example, the following method, with a high-pressure high-speed fluid jet such as needling or water jet, or by integrating it with an adhesive or a hot pressing process. . (A) A method in which crimped short fibers (staples) are opened into a sheet by a card machine such as a flat card or a roller card. (B) A method of stretching and opening a laminate of long fiber tows in the width direction. (C) A method of randomly laminating long fibers on a belt. (D) A method of randomly laminating short fibers on a belt while opening the fibers with a high-speed fluid.

The non-woven fabric used in the present invention has a basis weight of about 13 to 50 g / m ^{2 in} view of recent market demands for lightness, thinness and shortness.
Is preferably within the range of 15 to 35 g /
It is within the range of m ² . If the grammage exceeds about 50 g / m ² , it will be too thick and heavy, and it will not meet the market demand for developing the product of the present invention. If the basis weight is less than 13 g / m ² , the strength and cushioning properties required for practical use are insufficient.

Next, the market demand for the intended use of the non-woven fabric obtained by the above-mentioned manufacturing method, that is, within the values targeting various characteristics such as bulk density, heat shrinkage ratio, surface smoothness, and fluffiness It heats and presses so that it enters. This heating / pressurizing process may be performed by a calender roll or a flat plate press, but normally calendering with good production efficiency is good. In the case of calendering, the diameter is about 25-100 cm
Between two hard surface rolls, or about 15 in diameter
One hard surface roll of ~ 80 cm and diameter about 30-1
It is performed by heating and pressing with an elastic roll of 00 cm, but if anything, it is desirable that heating and pressing is performed between two hard surface rolls. The reason is that it becomes possible to process at a higher temperature and it is easy to put the properties such as the heat shrinkage rate and the fluff removal property of the processed nonwoven fabric within the target values. The heating temperature during processing is in the range of about 230 to 350 ° C, preferably 270 to 330 ° C. The applied pressure is about 70 ~
Within the range of 350 kg / cm, preferably 150-250
Within the range of kg / cm. When the heating temperature and the pressing force are out of the above ranges, the bulk density of the obtained nonwoven fabric is 0.45 g.
/ M ² or less, and not only the cushioning property is deteriorated, but also various other properties cannot be satisfied and the initial purpose cannot be achieved. That is, if the heating temperature is too low, the heat shrinkage rate of the nonwoven fabric becomes too large, and the surface smoothness and the fluffiness are reduced. On the other hand, if the heating temperature is too high, the flexibility and cushioning properties are lost, and the initial purpose cannot be achieved. On the other hand, if the pressure is too low, the surface smoothness and the fluff removal property are deteriorated. On the contrary, if the pressure is too high, the bulk density does not fall within the target value and the cushioning property is deteriorated.

[0015]

As described above, the aramid nonwoven fabric of the present invention is excellent in heat resistance, flexibility and thin leaf property, and is excellent in cushioning property, fluff removal property, etc., and also has a small heat shrinkage rate at high temperature and is electrically insulating. It is also useful as a heat-resistant insulating spacer for various electric and electronic devices, as well as being useful in the process of forming an electric insulating material and the process of manufacturing a printed circuit board material.

The present invention will be described in more detail with reference to the following examples. The various characteristic values shown in the examples are values measured by the following methods.

1) Basis weight: Measured according to JIS-P-8124.

2) Thickness: Measured according to JIS-C-2111.

3) Bulk density: Measured according to JIS-C-2111.

4) Heat shrinkage ratio: A sample of length × width = 30 cm × 30 cm was taken from the portion excluding both ends of the nonwoven fabric, and in this sample, length × width = 25 cm × 25 c
After drawing a square of m, the sample was placed in a dryer (manufactured by Tabai Espec Co., Ltd.) and heat-treated at 300 ° C. for 10 minutes, and the heat shrinkage rates in the vertical direction and the horizontal direction were calculated by the following formulas.

Thermal shrinkage (%) = {(S ₀ −S) / S ₀ } × 100 <Note 1> S ₀ : Dimension of square drawn in sample before heat treatment S: Draw in sample after heat treatment Square dimension <Note 2> Calculate the heat shrinkage ratios in the vertical and horizontal directions respectively, and then find the average value of the heat shrinkage ratios in the vertical and horizontal directions, and use this value as the heat shrinkage ratio of the sample.

5) Measurement of fluff deficiency (number of fluff deficiencies) An adhesive tape prepared according to JIS-Z-1522 was attached to the surface of an aramid non-woven fabric and pressed with a linear pressure of 1 kg / cm, and then adhesive. The tape was peeled off, and the number of fluffs adhered to the adhesive tape side was counted and converted to per 10 cm ² ┴ for comparison and judgment.

[0023]

Example 1 Polymetaphenylene isophthalamide short fibers having a single yarn fineness of 1.25 denier and a fiber length of 51 mm were used as aramid fibers. Approximately 30.2 g / m by opening with a card machine so that the fibers are arranged as much as possible in the traveling direction of the web.
^Two webs were formed. Subsequently, this web was subjected to a slight needling process and entangled to obtain a nonwoven fabric of about 30.5 g / m ² . Next, this nonwoven fabric was calendered between two hard surface rolls having a diameter of about 30 cm under the conditions shown in Table 1 to obtain the target heat-resistant thin leaf nonwoven fabric. Various properties of this nonwoven fabric were measured, and the results are shown in Table 1. The basis weight of the obtained nonwoven fabric was affected by the temperature during calendering and contracted to 34.1 g / m ²
It was.

[0024]

Example 2 The polymetaphenylene isophthalamide short fibers used in Example 1 were opened with a card machine in the same manner as in Example 1 so that the fibers were arranged in the direction of web travel as much as possible to obtain a low basis weight web. Formed. Then, press the web at high pressure,
Approximately 3 after being entangled with a high-speed water jet and then dried
A non-woven fabric of 0.0 g / m ² was obtained. Then, this non-woven fabric was calendered under the conditions shown in Table 1 between two hard surface rolls having a diameter of about 30 cm in the same manner as in Example 1 to obtain the target heat-resistant thin leaf-shaped non-woven fabric. Various properties of this nonwoven fabric were measured, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was affected by the temperature during calendering and contracted to 33.5 g / m ² .

[0025]

Example 3 A heat-resistant thin leaf-like nonwoven fabric of interest was obtained in the same manner as in Example 2 except that the calendering was carried out under the processing conditions shown in Example 3 of Table 1. The characteristics were measured, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was 31.5 g / m ² because the shrinkage was relatively small due to the low treatment temperature during calendering.

[0026]

Example 4 The heat-resistant thin leaf-like nonwoven fabric of interest was obtained in the same manner as in Example 2 except that the calendering conditions were those shown in Example 4 of Table 1. The characteristics were measured, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was 34.8 g / m ² due to a large shrinkage because the temperature during calendering was high.

[0027]

Example 5 As a non-woven fabric before calendering, about 15.
The target heat-resistant thin leaf-like nonwoven fabric was obtained in the same manner as in Example 2 except that 0 g / m ² of web was used and calendering was performed under the processing conditions shown in Example 5 of Table 1. Was measured for various characteristics, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was 16.6 g / m ² as it contracted under the influence of the temperature during calendering.

[0028]

COMPARATIVE EXAMPLE 1 Same as used in Example 1, about 30.2 g
The target heat-resistant thin leaf-like nonwoven fabric was obtained in the same manner as in Example 1 except that the nonwoven fabric having a thickness of / m ² was calendered under the processing conditions shown in Comparative Example 1 in Table 1. Various properties of this nonwoven fabric were measured, and the results are shown in Table 1. The basis weight of the obtained nonwoven fabric was 31.1 g / m ² with little shrinkage because the treatment temperature during calendering was considerably low.

[0029]

Comparative Example 2 Same as used in Example 2, about 30.0 g
The target heat-resistant thin leaf-shaped nonwoven fabric was obtained in the same manner as in Example 2 except that the nonwoven fabric of / m ² was calendered under the processing conditions shown in Comparative Example 2 in Table 1. Various properties of this nonwoven fabric were measured, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was 30.7 g / m ² with little shrinkage because the treatment temperature during calendering was considerably low.

[0030]

COMPARATIVE EXAMPLE 3 Same as used in Example 2, about 30.0 g /
The target heat-resistant thin leaf nonwoven fabric was obtained in the same manner as in Example 2 except that the m ² nonwoven fabric was calendered under the processing conditions shown in Comparative Example 3 in Table 1. Various properties of this nonwoven fabric were measured, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was 36.1 g / m ² due to a large shrinkage because the treatment temperature during calendering was considerably high.

[0031]

[Comparative Example 4] The present invention was carried out in the same manner as in Example 2 except that a non-woven fabric having a low basis weight of about 10.5 g / m ² was used and calendered under the processing conditions shown in Comparative Example 4 of Table 1. A heat-resistant thin-leaf nonwoven fabric was obtained. Various properties of this nonwoven fabric were measured, and the results are shown in Table 1. The basis weight of the obtained non-woven fabric was affected by the temperature at the time of calendering and was 11.7.
It was g / m ² .

As is clear from Table 1, the heat-resistant thin paper-like nonwoven fabric of the present invention has a strength that can withstand practical use, has a low bulk density, is rich in cushioning properties, has a low fluffiness, and has a low heat shrinkage rate at high temperatures. . Therefore, it is not only useful as a non-woven fabric used in the step of forming an electric insulating material and the step of manufacturing a printed circuit board, but also very useful as a heat resistant insulating spacer for various electric and electronic devices.

[0033]

[Table 1]

Claims (4)

[Claims] 1. A hot-pressed aramid nonwoven fabric having a basis weight of 50 g / m ² or less and a bulk density of 0.45 g / m ^2.
An aramid non-woven fabric characterized by having a heat shrinkage of 2.2% or less after heat treatment at 300 ° C. for 10 minutes at m ² or less, and having 10 or 10 cm ² or less fluffs removed from one side or both sides. 2. The aramid non-woven fabric according to claim 1, wherein the aramid fiber is a polymetaphenylene isophthalamide fiber. 3. An aramid non-woven fabric at a temperature of 270-330.
A method for producing an aramid nonwoven fabric, which comprises hot-pressing at a temperature of 150 to 250 kg / cm. 4. The aramid non-woven fabric is a spunlace entangled with a high-pressure high-speed flow water jet.
A method for manufacturing an aramid nonwoven fabric.