KR101228243B1 - A non-intumescent mat comprising crystalline type inorganic fiber and a method for manufacturing the same - Google Patents

Abstract

The present invention relates to a non-expandable mat comprising crystalline inorganic fibers and a method of manufacturing the same, and more particularly, to crystalline inorganic fibers, including crystalline inorganic fibers, having a length of 500 μm or less By including 10 to 80% by weight of the total amount, and relates to a non-expandable mat and a method for producing the same, characterized in that it has a level of mounting density and initial bulk density suitable as a fixing material for pollution prevention devices without further densification work.

Inorganic, Fiber, Non-Inflatable, Matte

Description

Non-expandable mat containing crystalline inorganic fibers and a method for manufacturing the same {A NON-INTUMESCENT MAT COMPRISING CRYSTALLINE TYPE INORGANIC FIBER AND A METHOD FOR MANUFACTURING THE SAME}

1 is a graph showing the change in pressure applied by the mat in accordance with the temperature change in the non-expandable mats prepared in Examples and Comparative Examples of the present invention.

The present invention relates to a non-expandable mat comprising crystalline inorganic fibers and a method of manufacturing the same, and more particularly, to crystalline inorganic fibers, including crystalline inorganic fibers, having a length of 500 μm or less By including 10 to 80% by weight of the total amount, and relates to a non-expandable mat and a method for producing the same, characterized in that it has a level of mounting density and initial bulk density suitable as a fixing material for pollution prevention devices without further densification work.

In general, an inorganic fiber mat can be used as a fixing material for supporting a brittle structure of an anti-pollution device such as, for example, an exhaust gas treatment device of an automobile. When an expandable inorganic fiber mat is used as such fixing material, the temperature around the mat is 500 ° C. If not too high, the expandable material (typically vermiculite particles) contained in the mat will not expand sufficiently to maintain the mounting pressure at the required level and, as a result, to protect the brittle structure in the device. Therefore, in the case of an exhaust gas treatment apparatus having an operating temperature of 500 ° C. or lower, such as in a diesel engine, an intumescent mat capable of maintaining bearing capacity without depending on the expandable material should be used.

In order for non-expandable mats to be used as fasteners to support the brittle structure of the pollution prevention device, there must be little heat shrinkage to maintain the original volume and elasticity even under various temperature changes. The heat shrinkability of non-expandable mats is highly dependent on the physical properties of the inorganic fibers that make up the mat.Amorphous ceramic fibers, when subjected to a high temperature environment, cause crystal growth in the amorphous structure, resulting in heat shrinkage. There is a problem that the volume is reduced or the heat cracking resistance is weak. Therefore, it is preferable to use crystallized inorganic fibers for non-expandable mats.

Examples of crystalline inorganic fibers mainly used in non-expandable mats include crystalline mullite fibers containing 72% alumina and 28% silica. In the case of such crystalline mullite fibers, both thermal and mechanical properties are satisfactory, but since the fibers have excellent elasticity, conventional wet lamination or dry lamination methods in which the fibers are entangled and entangled to form a mat are used. It is difficult to manufacture a mat from this. Thus, in order to produce non-expandable mats using crystalline inorganic fibers, it is necessary to use organic or inorganic binders or to introduce physical bonding processes such as stitching or needling.

In Korean Patent Laid-Open No. 2002-0015695, a fixing sheet is prepared by mixing polycrystalline fibers and amorphous ceramic fibers. As described above, since the ceramic fiber is subjected to a high temperature environment, crystal growth occurs in a structure that was amorphous, resulting in heat shrinkage, thereby reducing the volume of the mat or weakening the heat crack resistance. The annealing of the ceramic fibers at temperatures above or above the crystal formation point prior to mixing the inorganic fibers to produce the mat is intended to minimize the loss of mounting pressure due to crystal formation that occurs after the mat is mounted.

On the other hand, the Republic of Korea Patent Publication No. 2005-0055735 leaching glass fibers to increase the silica content in the fiber and then to prepare a mat using the same.

However, in the case of the non-expandable mat manufactured by the conventional method including the above-mentioned method, the mounting density and the initial bulk density of a certain level (approximately 0.4 to 0.75 g / cm 3), which are preferably required as fixing materials for pollution prevention devices, To have a green bulk density (about 0.2 g / cm 3) requires additional densification operations such as additional stitching or needling after mat manufacture.

The present invention has been made to solve the problems of the prior art as described above, an object of the present invention is to expand the non-expandable weapon having a suitable level of mounting density and initial bulk density as a fixing material for pollution prevention devices without additional densification work after mat manufacturing. It is to provide a fiber mat and a method of manufacturing the same.

According to the present invention, there is provided a non-expandable mat comprising crystalline inorganic fibers, wherein the crystalline inorganic fibers having a length of 500 μm or less comprise 10 to 80% by weight of the total amount of the crystalline inorganic fibers.

As the crystalline inorganic fibers, crystalline inorganic fibers commonly used in non-expandable inorganic fiber mats can be used without limitation, preferably, alumina fibers, mullite fibers, alumina-mullite fibers, alumina-silica fibers, alumina -Selected from the group consisting of mullite-silica fibers and mixtures thereof. Moreover, there is no restriction | limiting in particular in the diameter, It can select suitably within the range which can achieve the objective of this invention.

In the non-expandable mat of the present invention, the crystalline inorganic fibers having a length of 500 μm or less, preferably 200 to 500 μm, are 10 to 80% by weight of the total amount of the crystalline inorganic fibers, preferably 30 to 70% by weight. Crystalline inorganic fibers of greater than 500 μm, preferably longer than 500 μm and having a length of 50 mm or less, from 20 to 90% by weight of the total amount of crystalline inorganic fibers, preferably from 30 to 70% by weight. Included as. If the amount of crystalline inorganic fibers of 500 μm or less in length of the non-expandable mat of the present invention is less than 10% by weight of the total amount of the crystalline inorganic fibers, the space between the inorganic fibers in the mat is increased, thereby increasing the volume of the mat. Since the mat is not easy to mount, there is a disadvantage that an excess binder or an additional pressing process is required to reduce the volume and increase the density. On the other hand, when the amount of the crystalline inorganic fibers of less than 500 ㎛ length exceeds 80% by weight of the total amount of the crystalline inorganic fibers there is a problem that the less the entanglement and twist of the inorganic fibers to reduce the tensile strength of the mat.

Although the crystalline inorganic fiber is used for the non-expandable mat of the present invention, a small amount of amorphous ceramic fiber may be additionally used as necessary.

Amorphous ceramic fibers that may be further included in the non-expandable mat of the present invention include amorphous silica fibers, amorphous alumina-silica fibers, amorphous zirconia-silica-alumina fibers, and the like content is about 0.1 to 20% by weight of the total amount of inorganic fibers Is preferably, but is not limited thereto.

The non-expandable mat of the present invention preferably further includes an organic or inorganic binder material for improving mechanical properties such as tensile strength.

As the organic or inorganic binder material, any binder material conventionally used in manufacturing an inorganic fiber mat may be used without limitation. As the organic binder material, preferably hydrophobic polymers, more preferably those selected from the group consisting of acrylic polymers, urethane polymers, rubber polymers and mixtures thereof, are usually used in the form of an aqueous latex or emulsion. Most preferably an aqueous latex or emulsion of acrylic polymer is used. As an aqueous latex binder of such an acrylic polymer, commercially available products such as Primal EC-1791, Rhoplex 2438, Rhoplex HA-8 or Rhoplex TR-934, available from Rohm and Hass, for example. In the mat of the present invention, the organic binder material is generally included in about 1 to 15 parts by weight per 100 parts by weight of the inorganic fiber, but is not limited thereto, and may be appropriately selected as necessary.

In addition, as the inorganic binder material, it is preferable that clay, colloidal silica or alumina is used alone or in combination, but is not particularly limited thereto. Alumina sol such as, for example, Nayacol AD20 may be obtained commercially and used as an inorganic binder. In the mat of the present invention, the inorganic binder material is generally included in about 0.1 to 5 parts by weight per 100 parts by weight of the inorganic fiber, but is not limited thereto, and may be appropriately selected as necessary.

Meanwhile, the non-expandable mat of the present invention may further include additives such as an antifoaming agent and a dispersing agent, if necessary, and the amount thereof may be appropriately selected within the range in which the object of the present invention can be achieved.

In the non-expansible mat of the present invention, since a relatively short crystalline inorganic fiber having a length of 500 µm or less and a longer crystalline inorganic fiber are mixed to form a mat, a web is basically formed by a long fiber and therebetween. It has a structure to fill the short fibers. Therefore, while maintaining the tensile strength of the mat properly, it is possible to reduce the empty space between the inorganic fibers can be high density, as a result, it can have a high initial bulk density, mounting density and mounting support. The non-expandable mat of the present invention preferably has an initial bulk density of 0.15 to 0.25 g / cm 3, a mounting density of 0.25 to 0.75 g / cm 3 and / or a mounting bearing capacity of 15 psi or more.

The non-expandable mat of the present invention uses a relatively short crystalline inorganic fiber having a length of 500 µm or less and a relatively long crystalline inorganic fiber having a length greater than that, and thus, a conventional inorganic fiber mat manufacturing method (wet method or Dry method).

In one preferred embodiment of the wet method of the method for producing the non-expandable mat of the present invention, (1) preparing an aqueous slurry comprising water, mixed inorganic fibers and a binder material, (2) in step (1) Adding and stirring a binder flocculant to the prepared slurry, and (3) dehydrating and drying the resultant mixture of step (2) to prepare a mat, wherein the mixed inorganic fibers have a length of 500 μm or less. Non-expandable mat manufacturing method characterized by including 10 to 80% by weight of crystalline inorganic fibers having and 20 to 90% by weight of crystalline inorganic fibers having a length exceeding 500 μm.

In the wet method, the crystalline inorganic fibers and the binder material included in the aqueous slurry are as described above.

In the wet method, the slurry prepared in step (1) includes water, mixed inorganic fibers and a binder material, the total inorganic fiber content of the slurry is preferably 0.1 to 20 parts by weight based on 100 parts by weight of water, 0.1 The content of the binder material is preferably 1 to 15 parts by weight, more preferably 1 to 8 parts by weight based on 100 parts by weight of the total amount of the inorganic fibers. If the total amount of inorganic fibers in the slurry is less than 0.1 parts by weight based on 100 parts by weight of water, the slurry concentration is too low, so that the organic binder is less likely to adhere to the inorganic fibers and the tensile strength of the manufactured mat is also weakened. If it exceeds 20 parts by weight, there is a fear that the dispersion of the slurry becomes uneven. In addition, when the content of the binder material in the slurry is less than 1 part by weight based on 100 parts by weight of the total amount of inorganic fibers, the elasticity of the mat may be deteriorated. When the content of the binder material exceeds 15 parts by weight, the organic binder material may be deteriorated at a high temperature, resulting in a loss in the mounting pressure of the mat. There is a risk of adding.

As the binder material, an organic binder material as described above is preferably used, and an inorganic binder may be additionally used as necessary. Inorganic binders that can be used are as described above. Meanwhile, the slurry may further include additives such as an antifoaming agent and a dispersing agent as necessary.

There are no particular limitations on the production conditions, such as temperature and stirring speed during the slurry production, it is possible to adopt conventional inorganic fiber slurry production conditions as it is or appropriately changed. In order to prepare the slurry, the order of addition of each component is also not particularly limited. Generally, the inorganic fiber is first added to an excess of water, followed by vigorous stirring to disperse the inorganic fiber to some extent. Additives are added and further stirred to ensure that the binder material is evenly dispersed in the slurry.

In the wet method, in step (2), a binder flocculant is added to the inorganic fiber slurry prepared in step (1) and stirred to cause the inorganic fiber and the binder material to aggregate together.

The binder flocculant (also referred to as pH regulator) is used to agglomerate the binder so that the binder adheres to the inorganic fiber better, and is used to adjust the pH of the slurry to preferably 5.5 to 6.5. As such a coagulant, a binder coagulant conventionally used in the wet production of the inorganic fiber mat can be used without limitation, and an aqueous solution of aluminum sulfate is preferably used. More preferably, an aqueous solution of aluminum sulfate at a concentration of about 0.1 to 10% by weight is used. The binder flocculant is preferably used in an amount such that the slurry has a pH of 5.5 to 6.5, and by controlling the pH, weakens the electrical double layer of the binder particles stabilized in an emulsion state, thereby making them unstable and causing the binder particles to agglomerate. It works. The binder flocculant is typically 0.025 to 0.1 parts by weight per 100 parts by weight of slurry, but is not limited thereto.

In addition, in the step (1-1b), additives such as an antifoaming agent and a dispersing agent may be further added to the slurry as necessary.

The binder flocculant is added after dispersing the inorganic fiber and the primary organic binder material evenly in water, and the strength and cohesion of the cohesion in the slurry can be controlled by the initial amount or concentration of the binder flocculant. Additional agitation at moderate speeds can also control the strength of cohesion and the mode of cohesion.

In the wet method, in step (3), the resultant mixture of step (2) is dehydrated and dried to prepare an inorganic fiber mat.

As the dehydration apparatus, a known press-type sheet manufacturing apparatus or a mat manufacturing apparatus can be used without limitation, and a known drying method such as air drying or heat drying may be used as the drying method.

According to one embodiment of the wet method of the present invention, in step (3), the slurry agglomerated by the binder flocculant is introduced into a conventional paper machine and then dewatered or vacuum dewatered to form a mat. Subsequently, an additional pressing process is optionally performed, and the remaining moisture is finally dried. As a drying method, general air drying or heat drying below 150 ° C. is suitable. Inorganic fiber mats are prepared by cutting the final dried mat into desired shapes by means such as stamping or die cutting.

On the other hand, as a preferred embodiment of the dry method of the method of manufacturing the non-expandable mat of the present invention, (i) laminating the mixed inorganic fibers to prepare a mat, (ii) to the mat prepared in step (i) Adding a binder material, and (iii) dehydrating and drying the resultant mat of step (ii), wherein the mixed inorganic fiber comprises 10-80 wt% of crystalline inorganic fiber having a length of 500 μm or less And 20 to 90% by weight of a crystalline inorganic fiber having a length exceeding 500 μm.

In the dry method, the inorganic fibers and the binder material are as described above.

In the step (i) of the dry method, a mixed inorganic fiber comprising 10 to 80% by weight of crystalline inorganic fibers having a length of 500 μm or less and 20 to 90% by weight of crystalline inorganic fibers having a length of more than 500 μm. To produce a nonwoven mat.

In step (i), the nonwoven mat may be manufactured according to a conventional method. For example, the inorganic fibers may be individualized with a hammer mill or blower and then transferred to a conventional web carding machine, where the inorganic fibers may be moved onto a wire screen or mesh belt (metal or nylon belt). Form the web. When the web is formed, the inorganic fibers are additionally bonded using an emulsion adhesive or needle punched or stitched to prepare a nonwoven mat. For convenience of processing, the nonwoven mat is formed on an auxiliary film. Depending on the length of the inorganic fiber, it is possible to produce a nonwoven mat with sufficient handleability only by needle drilling or stitch bonding without an auxiliary material. Further workability may be improved by adding suitable organic binders by spraying or dipping during web formation or after mat manufacture.

In the step (ii) of the dry method, a binder material is added to the dry mat prepared as described above.

In the step (ii) of the dry method, the binder material, in particular the organic binder material, is added in the form of a solution (or dispersion, hereinafter referred to as 'solution') and added to the dry mat by dipping or spray coating or the like. In the binder solution, a solvent (or dispersion medium, hereinafter referred to as 'solvent') is basically the same kind of medium in which the binder material is dispersed or dissolved. When the emulsion of the aqueous acrylic polymer is used as the organic binder, the solvent of the binder solution is also used. It is preferred to include 0.1 to 50 parts by weight of the binder material per 100 parts by weight). In addition, the binder solution may further include additives such as a dispersant and a surfactant, as necessary. In addition, the amount of the binder material added to the dry mat by dipping or spray coating is preferably 1 to 15 parts by weight, more preferably 1 to 8 parts by weight per 100 parts by weight of the dry mat. If the amount of the binder material added is less than 1 part by weight per 100 parts by weight of the dry mat, the elasticity of the mat may be deteriorated. If the amount of the binder material exceeds 15 parts by weight, the organic binder material may deteriorate at a high temperature, which may cause a loss in the mounting pressure of the mat.

In the step (iii) of the dry method, the mat to which the primary organic binder material is added is dehydrated and dried. As the dehydration apparatus, a known press-type sheet manufacturing apparatus or a mat manufacturing apparatus can be used without limitation, and as a drying method, a known drying method such as air drying or heat drying may be used.

The non-expandable mat manufacturing method by the wet method or the dry method may further include spraying or coating an additional organic binder material on the surface of the prepared inorganic fiber mat and drying it. This coating of the additional binder material on the mat surface can improve the mechanical properties of the mat with a smaller binder content.

The additional organic binder material is prepared in the form of a solution and is then added to the mat surface by dipping or spray coating, preferably with a hydrophobic polymer, more preferably with an acrylic polymer, urethane polymer, rubber polymer and mixtures thereof. It is selected from the group consisting of and used in the form of an aqueous latex or emulsion. Most preferably an aqueous latex or emulsion of acrylic polymer is used. As a subsequent drying method, a known drying method such as general air drying or heating drying at 150 ° C. or lower may be used, and it is particularly preferable to heat-dry to cure the additional organic binder material immersed or spray-coated.

As described above, the non-expandable mat manufactured by the wet method or the dry method may have a high level of initial bulk density and a mounting density without an additional densification process such as a compression process, but to further improve the additional density after the completion of dehydration and drying It may be further processed.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

Example 1

30 g of alumina-mullite fiber mixture (inorganic fiber weight having a length of 500 μm or less: weight of inorganic fiber having a length exceeding 500 μm = 1: 1) was added to 2 L of water, stirred, and dispersed therein, followed by an organic binder material. As a binder, 4.8 g of acrylic organic binder (Primal EC-1791, Rohm and Hass, 50% solid content concentration) (8 parts by weight of binder solids per 100 parts by weight of inorganic fibers) was added to a slurry in which inorganic fibers were dispersed and stirred, 3 ml of an aqueous solution of aluminum sulfate at a concentration of 3 wt% was added as a flocculant and stirred for a further 5 minutes to form a slurry of aggregates of the inorganic fiber-binder. The slurry was poured into a sheet machine to dehydrate and manufactured in a mat form. The dehydrated mat was placed in a 120 ° C. oven for 2 hours to dry the moisture completely to make a non-expansible mat.

Initial bulk density of the prepared inorganic fiber mat was calculated from the basis weight (weight) and thickness of the mat, which is shown in Table 1 below. In addition, the mat is placed between the gap of 4mm, and the change in pressure applied by the mat according to the temperature change while changing the temperature from room temperature to 800 ℃, the results are shown in FIG.

[Example 2]

Same as Example 1 except that a different alumina-mullite fiber mixture (inorganic fiber weight having a length of 500 μm or less: inorganic fiber weight having a length exceeding 500 μm = 2: 1) was used. A non-expandable mat was produced by the method.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

[Example 3]

Inorganic fiber mixture different from Example 1 [Alumina-Mullite fiber weight having a length of 500 μm or less: Alumina-Mullite fiber weight having a length exceeding 500 μm: Amorphous ceramic fiber (type: Alumina-silica fiber) Weight = 2: 3: 1], but a non-expandable mat was prepared in the same manner as in Example 1.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

Example 4

Dry-laminated the alumina-mullite fiber mixture (inorganic fiber weight having a length of 500 μm or less: weight of inorganic fiber having a length exceeding 500 μm = 1: 1) to the same basis weight as Examples 1, 2 and 3 After needle punching to prepare a dry mat. Thereafter, the prepared dry mat was impregnated with a 1 wt% diluent of an acrylic organic binder (Primal EC-1791, Rohm and Hass) as an organic binder material, and then passed through a pressing roll to remove excess binder dilution. The mat passed through the pressing roll was placed in a 120 ° C. oven for 2 hours to completely dry the moisture to prepare a non-expandable mat.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

Comparative Example 1

An intumescent mat was prepared in the same dry manner as in Example 4 except that only alumina-mullite fibers having a length exceeding 500 μm were used.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

Comparative Example 2

A non-expansible mat was prepared by the same wet method as in Example 1 except that only alumina-mullite fibers having a length exceeding 500 μm were used.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

[Comparative Example 3]

Example 1, except that inorganic fiber mixtures different from Example 1 [alumina-mullite fiber weight: amorphous ceramic fiber (type: alumina-silica fiber) weight = 1: 1] were used. Non-expandable mats were prepared in the same wet method.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

[Comparative Example 4]

An intumescent mat was prepared by the same wet method as in Example 1, except that only amorphous ceramic fibers (type: amorphous alumina-silica fibers) were used.

Initial bulk density of the prepared inorganic fiber mat was measured in the same manner as in Example 1, which is shown in Table 1 below. In addition, for this mat, the change in pressure applied by the mat according to the temperature change was measured in the same manner as in Example 1, and the results are shown in FIG.

[Table 1]

As can be seen from Table 1, the non-expandable mat of the present invention has a higher initial bulk density of the mat than Comparative Examples 1 and 2 using only crystalline inorganic fibers having a length exceeding 500 µm. Therefore, according to the present invention, a thinner mat with the same weight can be made without a separate pressing process.

In addition, in the case of Comparative Example 4 using only amorphous ceramic fibers, the initial bulk density was considerably high, but as shown in FIG. 1, thermal shrinkage of the amorphous ceramic fibers occurred at a high temperature, thereby causing the mat to lose elastic force, and as a result, the mounting pressure was increased. Sharply decreased.

As described above, according to the present invention, a non-expandable inorganic fiber mat having a suitable level of mounting density and initial bulk density can be obtained as a fixing material for antipollution devices without further densification work after mat production.

Claims (10)

Total crystalline inorganic fibers, including crystalline inorganic fibers, wherein the crystalline inorganic fibers having a length of 500 μm or less are 10-80 wt% of the total amount of the crystalline inorganic fibers, and the crystalline inorganic fibers having a length exceeding 500 μm. Including 20 to 90% by weight of, A non-expandable mat characterized by having a structure in which a web is formed of crystalline inorganic fibers having a length exceeding 500 μm, and a crystalline inorganic fiber having a length of 500 μm or less is filled therebetween. The method of claim 1, wherein the crystalline inorganic fibers are selected from the group consisting of alumina fibers, mullite fibers, silica fibers, alumina-mullite fibers, alumina-silica fibers, mullite-silica fibers, alumina-mullite-silica fibers and mixtures thereof. Non-expandable mat, characterized in that. The non-expandable mat according to claim 1, further comprising amorphous ceramic fibers. The non-expandable mat of claim 1 further comprising an organic or inorganic binder material. The non-expandable mat according to claim 1, having an initial bulk density of 0.15 to 0.25 g / cm 3. The non-expandable mat according to claim 1, having a mounting density of 0.25 to 0.75 g / cm 3. delete (1) preparing an aqueous slurry comprising water, mixed inorganic fibers and a binder material, (2) adding and stirring a binder flocculant to the slurry prepared in step (1), and (3) dehydrating and drying the resultant mixture of step (2) to produce a mat, Said mixed inorganic fiber comprises 10 to 80% by weight of crystalline inorganic fiber having a length of 500 μm or less and 20 to 90% by weight of crystalline inorganic fiber having a length of more than 500 μm. Non-expandable mat production method according to. (i) laminating mixed inorganic fibers to produce a mat, (ii) adding a binder material to the mat prepared in step (i), and (iii) dehydrating and drying the resultant mat of step (ii), Said mixed inorganic fiber comprises 10 to 80% by weight of crystalline inorganic fiber having a length of 500 μm or less and 20 to 90% by weight of crystalline inorganic fiber having a length of more than 500 μm. Non-expandable mat production method according to. 10. The method of claim 8 or 9, further comprising spraying or coating an additional organic binder material on the surface of the prepared inorganic fiber mat and drying it.

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