JP3378121B2 - Heat resistant board - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an automobile engine, etc.
The present invention relates to a heat resistant board that can be suitably used as a heat shield plate for an exhaust gas part of a heat generating device.

[0002]

2. Description of the Related Art Conventionally, heat shielding of the exhaust gas portion of heat-generating equipment such as an internal combustion engine has not been carried out so much, but in recent years, for example, in the case of automobiles, precision equipment has been installed and the temperature in the engine room has been reduced. The demand for lowering has increased. For this reason, there has been a demand for a heat-resistant material that prevents the exhaust heat of the engine from being released into the engine room.

As such a heat-resistant material, for example, Japanese Patent Laid-Open No. 60-209100 discloses a meta-aramid short fiber, a pulp made of meta-aramid, and a non-woven fabric further mixed with glass short fibers as required. A press board that has been laminated and hot pressed has been proposed. However, these boards have a limit in heat resistance because they are composed of only organic substances when glass short fibers are not used in combination, and when glass short fibers are used in combination, the glass short fibers and aramid are used. There is a problem in practical use due to the difficulty in adhesion to short fibers.

Further, Japanese Patent Laid-Open No. 167908/1990 proposes a press board obtained by laminating and heating a nonwoven fabric obtained by mixing polyethylene terephthalate short fibers with pulp made of meta type aramid short fibers and meta type aramid. . However, this is also limited to heat resistance because it is composed only of organic substances as in the above case. Further, the mixed papermaking of these meta type aramid short fibers and the pulp made of the meta type aramid also has a drawback that the papermaking productivity is poor because the drainage is regulated by the pulp.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and can be suitably used as a heat shield plate for an exhaust gas part of a heat-generating device such as an automobile engine. It is an object of the present invention to provide a heat resistant board which is excellent in productivity and has good productivity.

[0006]

The above-mentioned object can be achieved by the following constitutions. That is, "(Claim 1) A heat-resistant board obtained by integrally molding a mixed paper comprising glass short fibers, meta-aramid short fibers, and polyvinyl alcohol short fibers under heat and pressure,
The board has a thickness of 0.5 to 5 mm and a bulk density of 0.7 to
A heat-resistant board characterized by having a flexural modulus of 1.6 g / cm ³ and a flexural modulus of 50 Kgf / mm ² or more. (Claim 2) The heat-resistant board according to claim 1, wherein the meta-aramid short fibers are undrawn yarns. It is.

The glass short fibers used in the present invention have a fiber diameter of 6 to 20 μm, preferably 8 to 15 μm, and a fiber length of 3 to 25 mm, preferably 5 to 12 mm.

The meta-type aramid short fibers are (a) a condensed polyamide of an aromatic dicarboxylic acid and an aromatic diamine that are substantially meta-typed, and (b) that is substantially meta-typed. A meta-aramid such as a condensed polyamide obtained by condensing an aromatic aminocarboxylic acid, (c) a polyamide obtained by copolymerizing the above (a) and (b), and the like are prepared by a conventional method, and particularly, a drawing / heat treatment step. An undrawn yarn that does not pass through is preferred. The fineness of this meta-type aramid short fiber is 0.5 to 5.
It is desirable to use one having a denier of 0, preferably 1.0 to 3.0 and a fiber length of 3 to 25 mm, preferably 5 to 12 mm.

[0009] Polyvinyl alcohol short fibers are used to increase the strength of mixed paper after papermaking drying and to improve processability. The fineness thereof is 0.5 to 2.0 denier and the fiber length is 2 to 15 mm. It is desirable to use one.

In the present invention, the blending ratio of each of the above short fibers is 20 to 6 when the short glass fibers are based on the weight of the mixed paper.
5% by weight, preferably 35 to 50% by weight, meta-aramid short fibers 25 to 79% by weight, preferably 43 to 63% by weight, polyvinyl alcohol short fibers 1 to 10% by weight,
It is desirable to set it to 2 to 7% by weight. If the proportion of short glass fibers is less than 20% by weight, the rigidity of the resulting heat-pressed board will be insufficient, while 65
If the weight% is exceeded, the porosity of the resulting board will be too high and the adhesiveness between the meta type aramid short fibers and the glass short fibers will be insufficient, so when laminating and hot pressing multiple non-woven fabrics to form a board. Delamination is likely to occur. When the content of the meta-type aramid short fibers is less than 25% by weight, delamination of the obtained heat resistant board is likely to occur,
On the other hand, if it exceeds 79% by weight, the rigidity of the obtained heat resistant board becomes insufficient. Further, when the content of the polyvinyl alcohol short fibers is less than 1% by weight, the strength of the mixed paper is insufficient in the paper making process, and process troubles are likely to occur.
If it exceeds 0% by weight, the amount of decomposition gas of polyvinyl alcohol generated during hot pressing of the mixed paper after paper making increases, which is not preferable in the working environment, and the heat resistance and rigidity of the heat resistant board obtained at the same time also decrease. There is a tendency.

As a method of mixing and papermaking these glass short fibers, meta-aramid short fibers, and polyvinyl alcohol short fibers, any of the conventionally known methods can be adopted. The mixed paper made into paper has a water content of 50 to 95% by weight.
After laminating one or several of the above, dehydration under heating and pressure
A board is formed by a wet pressing method of drying and integrating, or a dry pressing method of rapidly heating and pressing a material having a water content of less than 45% by weight to integrate it.

The heating and pressing are usually performed by a flat plate press or a roll press. The heating temperature is 230-35.
The pressure is 0 ° C, preferably 250 to 330 ° C. The pressurizing pressure varies depending on the mixing ratio of the short fibers, but is 30 to 100 kg / cm ² for a flat plate press and 20 to 20 for a roll press.
About 80 kg / cm (linear pressure) is preferable.

The heat-resistant board of the present invention thus obtained has a thickness of 0.5 to 5.0 mm, preferably 0.7.
It should be ~ 3.5 mm. If the thickness is less than 0.5 mm, the heat shield effect will be insufficient, while 5.0 mm
If it exceeds, it is not preferable because unevenness in heat transfer is likely to occur during hot pressing and it is difficult to obtain a board of uniform quality.

The bulk density of the board is 0.7 to 1.6 g /
It is necessary to set it to be cm ³ , preferably 0.9 to 1.3 g / cm ³ . If it is less than this range, the rigidity of the board becomes insufficient, and the void ratio of the board becomes too large, so that delamination easily occurs, which is not preferable. On the other hand, when the amount exceeds the above range, the pressure during pressing is inevitably increased, and the glass short fibers in the board are broken, which lowers the rigidity of the board, which is not preferable.

Furthermore flexural modulus 50 kg / mm ² or more, it is preferably required to be 80~500kg / mm ^2. If it is less than this value, the shapeability of the board becomes insufficient, which is not preferable.

[0016]

Since the heat-resistant board of the present invention is composed of glass, meta-aramid and polyvinyl alcohol short fibers, it has the following effects. 1) Since the pulp-like material is not used, the drainage rate is high, so that the papermaking process speed is significantly increased and the productivity is dramatically improved as compared with the nonwoven fabric containing the pulp-like material. 2) Since polyvinyl alcohol fibers are blended in a specific ratio, the adhesion between fibers is improved while maintaining good heat resistance, and the dimensional stability and strength at high temperatures become good. 3) The board has low thermal conductivity and air permeability, and a good heat shield effect can be obtained. 4) Since the board has high rigidity, when used as a heat shield material for an automobile exhaust pipe, for example, the metal plate thickness of the exhaust pipe can be reduced, and the weight can be reduced.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples. Each measured value in the examples is evaluated by the following method. (1) Basis weight Measured according to JIS P8124. (2) Thickness was measured using a micrometer according to JIS C2111 5.2 method. (3) Bulk density The bulk density was measured according to the JIS C2111 6.1 method. (4) The delaminated board was cut in the thickness direction with a cutter knife, and it was visually determined whether cracks were formed in the inner layer of the board parallel to the surface. (Evaluation: ◯ = No delamination occurred × = Delamination occurred) (5) Bending elastic modulus It was measured according to JIS K6911 method 5-17.

[Example 1] A glass short fiber having a fiber diameter of 11 µm and a fiber length of 10 mm, a meta-aramid short fiber having a fineness of 3.0 denier and a fiber length of 6 mm, an undrawn fiber, and a polyvinyl alcohol short fiber. A fiber having a fineness of 1.0 denier and a fiber length of 6 mm is weighed so that the compounding weight ratio is glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 40/57/3, and 1% A fiber dispersion slurry was obtained by disaggregating and dispersing with a pulper at a concentration. The obtained slurry was paper-made using a tappy type square paper machine, dehydrated with a flat plate compressor and then dried with a drum dryer to obtain 1500 g / m ² of dried paper. The obtained dry paper was heated to a surface pressure of 50 kg / cm ² and a heating temperature of 30.
A board having a thickness of 1.4 mm was formed by press molding at 0 ° C. No delamination occurred on the obtained board. Various properties of the obtained board are shown in Table 1.

[Example 2] Fibers having a fiber diameter of 7 µm and a fiber length of 8 mm as short glass fibers, an unstretched fiber having a fineness of 2.0 denier and a fiber length of 4 mm as short meta-aramid fibers, and further polyvinyl alcohol short fibers. Fibers having a fineness of 1.5 denier and a fiber length of 10 mm were weighed so that the blending weight ratio was glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 30/65/5. In the same manner as in Example 1, 200 g / m ² of dry paper was obtained. 7 sheets of this dry paper are laminated and 50kg / cm
A board having a thickness of 1.0 mm was prepared by press molding at a surface pressure of ² and a heating temperature of 250 ° C. No delamination occurred on the obtained board.

[Comparative Example 1] Dry paper press molding conditions were set to 3
A board having a thickness of 2.3 mm was prepared in the same manner as in Example 1 except that the surface pressure was changed to 0 kg / cm ² . The bulk density of this board was as small as 0.65 g / cm ^3, and delamination occurred on the board.

[Comparative Example 2] The press molding condition for dry paper was 1
A board having a thickness of 0.8 mm was prepared in the same manner as in Example 1 except that the surface pressure was changed to 20 kg / cm ² . The bulk density of this board was as large as 1.88 g / cm ^3, and no delamination occurred on the board, but the rigidity of the board was insufficient.

[Example 3] Glass short fibers having a fiber diameter of 7 µm and a fiber length of 15 mm, meta-aramid short fibers having a fineness of 4.0 denier, unstretched fibers having a fiber length of 20 mm, and polyvinyl alcohol short fibers. Fibers having a fineness of 1.5 denier and a fiber length of 10 mm were weighed so that the blending weight ratio was glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 55/38/7. 100 g / m ^{2 in} the same manner as in Example 1
Of dry paper was obtained. 15 sheets of this dry paper are laminated and 40 kg
A board having a thickness of 2.0 mm was prepared by press molding at a surface pressure of / cm ² and a heating temperature of 280 ° C. No delamination occurred on the obtained board.

[Example 4] Glass short fibers having a fiber diameter of 15 µm and a fiber length of 5 mm, meta-aramid short fibers having a fineness of 0.8 denier, an unstretched fiber having a fiber length of 5 mm, and polyvinyl alcohol short fibers. Fibers having a fineness of 0.5 denier and a fiber length of 3 mm were weighed so that the blending weight ratio was glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 25/74/1. 100 g / m ² of dry paper was obtained in the same manner as in Example 1. 10 sheets of this dry paper are stacked and 50 kg / c
A board having a thickness of 0.7 mm was prepared by press molding at a surface pressure of m ² and a heating temperature of 280 ° C. No delamination occurred on the obtained board.

[Comparative Example 3] The same fiber as in Example 4 was used, but the compounding weight ratio was measured such that glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 70/25/5. 100 g / m in the same manner as in Example 1
² dry papers were obtained. 10 sheets of this dry paper are laminated and 50k
A board having a thickness of 1.6 mm was prepared by press molding at a surface pressure of g / cm ² and a heating temperature of 280 ° C. Delamination occurred on the obtained board, and the rigidity of the board was insufficient.

[Comparative Example 4] Except that the blending weight ratio of the same fibers as in Example 4 was measured such that glass short fibers / meta type aramid short fibers / polyvinyl alcohol short fibers = 45/40/15. 100 g / in the same manner as in Example 1
m ² of dry paper was obtained. Stack 10 sheets of this dry paper,
A board having a thickness of 1.2 mm was prepared by press molding at a surface pressure of kg / cm ² and a heating temperature of 280 ° C. A large amount of pyrolysis gas was generated during press working, and the obtained board also had insufficient rigidity.

Example 5 Fibers having a fiber diameter of 7 μm and a fiber length of 10 mm as short glass fibers, undensed fibers having a fineness of 3.0 denier and a fiber length of 10 mm as meta-aramid short fibers, and polyvinyl alcohol. A short fiber having a fineness of 1.0 denier and a fiber length of 10 mm was weighed so that the blending weight ratio was glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 55/38/7. , 200 g / m in the same manner as in Example 1
² dry papers were obtained. Stack 15 sheets of this dry paper and
A board having a thickness of 4.2 mm was prepared by press molding at a surface pressure of g / cm ² and a heating temperature of 320 ° C. No delamination occurred on the obtained board.

[Comparative Example 5] Fifteen dry paper sheets obtained by the same method as in Example 5 were laminated and press-formed at a surface pressure of 30 kg / cm ² and a heating temperature of 320 ° C. to a thickness of 5.3 mm. I made a board. The obtained board had low bulk density and delamination occurred.

[Example 6] Glass short fibers having a fiber diameter of 15 µm and a fiber length of 5 mm, meta-aramid short fibers having a fineness of 3.0 denier and an unstretched fiber having a fiber length of 5 mm, and polyvinyl alcohol short fibers. Fibers having a fineness of 1.5 denier and a fiber length of 3 mm were weighed so that the blending weight ratio was glass short fibers / meta-aramid short fibers / polyvinyl alcohol short fibers = 35/62/3, In the same manner as in Example 1, 200 g / m ² of dry paper was obtained. 10 sheets of this dry paper are stacked and 50 kg / c
A board having a thickness of 2.0 mm was prepared by press molding at a surface pressure of m ² and a heating temperature of 300 ° C. No delamination occurred on the obtained board.

[Example 7] Glass short fibers having a fiber diameter of 11 µm and a fiber length of 8 mm, meta-aramid short fibers having a fineness of 3.0 denier and a fiber length of 6 mm, unstretched fibers, and polyvinyl alcohol short fibers. Fibers having a fineness of 1.5 denier and a fiber length of 4 mm were weighed so that the blending weight ratio was glass short fiber / meta type aramid short fiber / polyvinyl alcohol short fiber = 45/42/3. In the same manner as in Example 1, 200 g / m ² of dry paper was obtained. Fifteen sheets of this dry paper are laminated and 50 kg / c
A board having a thickness of 3.7 mm was prepared by press molding at a surface pressure of m ² and a heating temperature of 300 ° C. No delamination occurred on the obtained board. The experimental results are summarized in Table 1.

[0030]

[Table 1]

Continuation of the front page (56) Reference JP 62-6999 (JP, A) JP 61-121934 (JP, A) JP 6-212593 (JP, A) JP 4-126894 (JP , A) JP-A-60-209100 (JP, A) JP-A-1-167908 (JP, A) JP-A-8-325947 (JP, A) JP-A-7-243189 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B32B 1/00-35/00 D21H 11/00-27/42

Claims (2)

(57) [Claims] 1. A glass short fiber, a meta-aramid short fiber,
And a heat-resistant board obtained by integrally molding a mixed paper made of polyvinyl alcohol short fibers under heat and pressure, the board having a thickness of 0.5 to 5 mm and a bulk density of 0.7 to 1.6.
A heat-resistant board characterized by having a flexural modulus of 50 kgf / mm ² or more in g / cm ³ . 2. The heat-resistant board according to claim 1, wherein the meta-aramid short fibers are undrawn yarns.