JPH0751210B2 - Glass fiber filter paper for heat resistant air filter and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass fiber filter paper for a heat resistant air filter which is used under high temperature conditions such as a clean oven and a drying line which are widely used in the semiconductor industry, biotechnology industry and the like, and a method for producing the same. Regarding

[0002]

2. Description of the Related Art Conventionally, as a filter element used at a high temperature in a clean oven or the like, (1) a glass fiber filter paper containing no organic binder is pleated, and (2) an organic filter element is used. After pleating the usual glass fiber filter paper containing the above binder into filaments, the whole element is heat-treated to decompose and volatilize organic substances, (3) A composite of a tetrafluoroethylene membrane and glass fiber filter paper Etc. are known.

However, in (1), since the glass fiber filter paper does not contain a binder, the strength of the filter paper is weak and the workability during processing is poor. In (2), the workability is good, but the strength is significantly reduced after the heat treatment. In order to solve these problems, measures such as reinforcement with a wire mesh are usually adopted.However, due to the weak adhesion between glass fibers, the filter paper itself emits due to a sudden change in shock, air volume, or temperature. The problem of dust has been pointed out. In particular, in a high-performance air filter commonly called a HEPA filter, since the purpose is to create a highly clean space, dust generated from the filter paper itself reduces the air cleanliness on the downstream side of the air filter and cannot be ignored. It's a problem. In addition, since the filter paper itself does not have water repellency, if water adheres, the strength is further reduced,
The filter paper itself may be damaged. In (3), since the tetrafluoroethylene film is an organic substance, there is a limit to the temperature that it can withstand, and it cannot be used at a high temperature such as 400 ° C.

On the other hand, many attempts have been proposed to increase the heat resistance of the material by using an inorganic binder.
As an inorganic binder, for example, colloidal silica,
Colloidal alumina, alkoxysilane and the like are known (Japanese Patent Laid-Open No. 64-77700 and Japanese Patent Laid-Open No. 3-124).
No. 86). However, when these inorganic binders are used, the filter paper becomes brittle, and it has not been put to practical use as a filter paper for an air filter accompanied by pleating.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems pointed out in conventional glass fiber filter papers for air filters. That is, the object of the present invention is (1) to improve suitability for pleating, to retain strength and rigidity at a level at which it is not particularly necessary to reinforce the filter paper when molded into a filter element, and to reduce strength deterioration due to water adhesion, (2) It has a high dust collection efficiency,
(3) 400-500 ° C, suppressing dust generation from the filter paper itself
Heat resistant glass fiber filter paper for air filter,
In particular, it is to provide a glass fiber filter paper for a high performance air filter with pleating.

[0006]

Means for Solving the Problems In order to provide a filter paper capable of withstanding a high temperature of 400 ° C., the present inventor diligently studied various inorganic binders and conditions for applying them, a method, a constitution and physical properties of the filter paper, It was found that the above problems can be solved by adjusting the specific physical properties of the filter paper using the above inorganic binder and by the specific application method.

That is, the first invention is that the condensate produced from the alkoxysilane is 1 to 7 weights based on the total weight of the filter paper.
% Content, machine direction Galley rigidity is 500-2000
It is a glass fiber filter paper for heat resistant air filters, characterized in that it is mgf.

A second invention is a method for producing the above glass fiber filter paper for heat-resistant air filters, which comprises applying an alkoxysilane solution after pleating, followed by drying and condensation.

The present invention will be described in more detail below.

The alkoxysilane used in the present invention is R ¹
Si (OR) _n [R; alkyl group, R ¹ ; carbon number 1 to 8
Of organic groups]. The partial hydrolyzate of the silicon alkoxide causes a condensation reaction with the alkoxide as follows,
Form a polymer: R ¹ Si (OR ² ) _n + H ₂ O-- → R ¹ Si (OR ² ) _n-1 OH + R ² OH R ¹ Si (OR ² ) _n-1 OH + R ¹ Si (OR _{^{2) n ── → R 1 Si}} (OR 2) n-1 -O-R 1 Si (OR 2) in _n-1 + R ² OH [wherein, R ¹ is an organic group having 1 to 8 carbon atoms Yes, R ²
Is an alkyl group having 1 to 5 carbon atoms and n is 3 or 4. This polymer is preferable because it has good adhesion to glass fibers or forms a strong coating having water repellency. That is, even if an inorganic binder such as alumina sol or colloidal silica is applied to the glass fiber filter paper, no water repellency is obtained, and since the film-forming property is poor, the strength is improved, but the fine glass fiber is used. It has been found that the force of fixing debris such as the above is inferior and the dust generation preventing effect is not present, and further that the binder itself falls off from the glass fiber filter paper due to vibration.
Another reason for choosing the silicon alkoxide is that it is a reactive inorganic binder, so that it has been found that the rigidity of the filter paper provided with this binder can be adjusted by adjusting the degree of reaction. The silicon alkoxide used in the present invention is a compound selected from trialkoxysilane and tetraalkoxysilane, and examples of the former include methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, ethyltrimethoxysilane, and vinyltrimethoxysilane. Methoxysilane and the like, and examples of the latter include tetramethoxysilane, tetraethoxysilane, and tetrabutylsilane. These can be used alone or as a mixture of two or more kinds, and may further contain a partially hydrolyzed product. Further, a small amount of inorganic colloid such as colloidal silica may be contained, but inorganic fine powder should not be contained because it causes dust generation from the filter paper.

The glass fiber filter paper used in the present invention has a basis weight of 4
It is preferable that the collection efficiency of 0.3 μm DOP (dioctyl phthalate) is 99.97% or more when the surface wind velocity is 0.3 cm / sec at 0 to 100 g / m ² . Weight is 4
If it is 0 g / m ² or less, the strength and rigidity of the filter paper itself are insufficient, and 1
On the other hand, if it is more than 00 g / m ² , the rigidity is too high and it is not suitable for producing the filter paper of the present invention. The fibers constituting the glass fiber filter paper are mainly composed of ultrafine glass fibers with a diameter of 4 μm or less, and in order to improve tensile strength and crease strength, chopped sland glass fibers 2 to 30 with a diameter of 5 μm or more are used.
Wt% is mixed. 2% by weight of chopped glass fiber
If the amount is less than 30% by weight, the strength cannot be expected to increase, and if it exceeds 30% by weight, the Gurley rigidity becomes high, and as a result, the filter paper becomes brittle and the collection efficiency decreases. If necessary,
Other inorganic fibers such as alumina fibers, kaolin fibers, zirconia fibers, potassium titanate fibers, and tyranno fibers may be added.

The bending stiffness in the machine direction is particularly important as the physical properties of the glass fiber filter paper after application of the alkoxysilane and drying, and Japan Tappi No 40
According to the above, it is essential that the Gurley rigidity measured on a test piece having a length of 63.5 mm and a width of 25.4 mm is 500 to 2000 mgf. It has been found that the amount of alkoxysilane adhered and the Gurley rigidity have an almost linear relationship, and the Gurley rigidity and the crease strength have an extremely close relationship, and when the Gurley rigidity exceeds 2000 mgf, it extremely decreases. Generally, glass fiber filter paper for high-performance air filters is folded into multiple pleats in the direction perpendicular to the machine direction of the filter paper to reduce airflow resistance (pleated), and stored in a frame to be used as a filter element. Therefore, the strength of the folds is extremely important. When the strength of the folds is weak, the folds may break from the folds during pleating or may break during ventilation, making it impossible to function as a filter. Since the organic binder is flexible, even if the Gurley rigidity exceeds 2000 mgf, the strength of the fold is not significantly reduced. However, in the present invention, the Gurley rigidity is 2000 mgf in order to maintain the strength of the fold.
The following are essential requirements. More preferably 1
It should be 800 mgf or less, and in order to withstand the wind pressure during ventilation of the filter without reinforcement, it is necessary to have a rigidity of 500 mgf or more. The Gurley rigidity can be adjusted by the amount of alkoxysilane attached and the drying temperature. The adhesion amount is preferably in the range of 1 to 7% by weight based on the total weight of the filter paper. 1
If it is less than 10% by weight, the improvement in strength is low, and the effect of preventing dust from the filter paper is insufficient. On the other hand, if it exceeds 8% by weight, the collection efficiency is lowered and the strength of the folds is greatly reduced. The drying temperature after application of the alkoxysilane is related to the amount of deposition. However, in order to adjust the Gurley stiffness to 2000 mgf or less, it must be selected below 140 ° C.
A preferable temperature range is 60 to 130 ° C. Adhesion amount 5.
Table 1 shows the relationship between the drying temperature, Gurley rigidity, and crease strength at 5% by weight.

[0013] Note) Glasca T2101 (trade name, manufacturer: Nippon Synthetic Rubber Co., Ltd., including methyltrimethoxysilane) is used, and the drying time is 15 minutes.

As the glass fiber filter paper to which the alkoxysilane is applied, one which does not substantially contain an organic substance or one which contains an organic binder in an amount of 4% by weight (based on the total weight of the filter paper) is used. To be In the latter case, by heat-treating at 300 to 400 ° C. after pleating, a glass fiber filter paper for heat-resistant air filters containing substantially no organic substance can be obtained. In this case, it is important that the content of the organic binder does not exceed 4% by weight, and if the content of the organic binder is more than 40% by weight, sufficient strength-improving effect after heat treatment is not observed even if alkoxysilane is added. Therefore, it is necessary to add the organic binder in the minimum necessary amount (4% by weight or less) that provides the strength to withstand the load during processing.

Alkoxysilane can be applied before pleating, that is, in the glass fiber filter paper manufacturing process, or can be applied to the dried fiber filter paper by using a coating machine, an impregnating machine, and a spray device. As another application method, there is a method of applying a solution of an alkoxysilane with a spray device or the like after pleating, followed by drying and condensation.

The advantage of this method is that the creases are already formed during the pleating process, so that the crease strength is higher than the case where the creases are formed after the alkoxysilane is applied.

[0017]

The selected reactive binder has the ability to form a film and has a good affinity with the surface of the glass fiber having silanol groups, and the hydrophobic portion is oriented on the opposite side of the surface of the glass fiber. It is presumed that at the same time as increasing the binding force, it has an action of preventing fine fibers from falling off from the filter paper and an action of improving water repellency. Since the specific reactive binder is selected and the degree of reaction can be adjusted by the temperature, the rigidity of the filter paper before processing can be adjusted, and as a result, the occurrence of brittleness common to the inorganic binders can be suppressed and at the time of processing. The decrease in strength can be reduced.

[0018]

Example 1 A glass fiber filter paper for a high-performance air filter, which is composed of 90% by weight of ultrafine glass fibers having an average diameter of 1 μm or less and 10% by weight of chopped strand glass fibers having an average diameter of 6 μm and which is substantially free of organic substances. A methanol solution of alkoxysilane (Glaska T2101: trade name, manufacturer: Nippon Synthetic Rubber Co., Ltd., containing methyltrimethoxysilane) is applied to (the same as in Comparative Example 1) by spraying, and the solution is sprayed at 120 ° C. for 15 minutes.
Dry for minutes, 2.1% by weight, Gurley stiffness 700
A mgf filter paper was obtained. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Example 2 In Example 1, an aqueous solution of ceramate C-100 (trade name, manufacturer: Catalysis Kasei Co., Ltd., containing methyltriethoxysilane) was used as the alkoxysilane, and the amount adhering thereto was 1.8% by weight. Except that the adjustment was made to
A filter paper having a Gurley stiffness of 1010 mgf was obtained. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Example 3 A filter paper having a Gurley stiffness of 1260 mgf was obtained in the same manner as in Example 1 except that the amount of alkoxysilane attached was adjusted to 4.3% by weight. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Example 4 A filter paper having a Gurley stiffness of 1480 mgf was obtained in the same manner as in Example 1 except that the amount of alkoxysilane deposited was adjusted to 6.5% by weight. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Example 5 The same as Example 1 except that the methanol solution of the alkoxysilane was applied by spraying in Example 1 and the drying was carried out at 100 ° C. for 15 minutes to adjust the adhesion amount to 7.0% by weight. A filter paper having a Gurley stiffness of 1720 mgf was obtained.
The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Example 6 90% by weight of ultrafine glass fibers containing 3% by weight of an acrylic latex and the balance having an average diameter of 1 μm or less and an average diameter of 6 μm
Glass fiber filter paper for high performance air filters composed of 10% by weight of chopped strand glass
101 (Product name, Alkoxysilane of Japan Synthetic Rubber Co., Ltd.)
Of methanol solution is applied by spraying at 120 ° C for 1
Dry for 5 minutes, 4.8% by weight, Gurley stiffness 16
50 mgf of filter paper was obtained. The physical properties and filter characteristics of this filter paper were measured. 400 more pieces of filter paper
It was treated at 0 ° C. for 2 hours and its physical properties were measured. Table 2 shows the measurement results.

Example 7 A glass fiber filter paper for a high-performance air filter containing substantially no organic substance (same as in Comparative Example 1) was applied to a square plate having a thickness of 1 mm in a direction perpendicular to the machine direction, and along the square plate. 180 °
Bend 5 times and make a crease. Then, a solution of alkoxysilane was applied by spraying and dried at 120 ° C. for 15 minutes to obtain a filter paper having an adhesion amount of 6.5% by weight. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Comparative Example 1 90% by weight of ultrafine glass fibers having an average diameter of 1 μm or less and an average diameter of 6
A glass fiber filter paper for high-performance air filters, which is substantially free of organic substances and is composed of 10% by weight of chopped glass fiber of μm. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. All measurement results are shown in Table 2.
Shown in.

Comparative Example 2 A filter paper having a Gurley rigidity of 500 mgf was obtained in the same manner as in Example 1 except that the amount of alkoxysilane attached was adjusted to 0.5% by weight. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Comparative Example 3 A filter paper having a Gurley stiffness of 2100 mgf was obtained in the same manner as in Example 1 except that the amount of alkoxysilane deposited was adjusted to 8.0% by weight. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Comparative Example 4 Gurley stiffness was 2050 mgf in the same manner as in Example 1 except that the amount of the alkoxysilane deposited was adjusted to 6.5% by weight and the drying was performed at 160 ° C. for 15 minutes.
A filter paper of The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. All measurement results are shown in Table 2.
Shown in.

Comparative Example 5 A glass fiber filter paper for a high performance air filter, containing 5.8% by weight of a commercially available organic binder. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper was further treated at 400 ° C. for 2 hours, and its physical properties were measured. Table 2 shows the measurement results.

Comparative Example 6 The same as Example 1 except that an aqueous solution of alumina sol-200 (trade name, manufactured by Nissan Kagaku Co., Ltd.) was used in place of the alkoxysilane in Example 1, and the adhesion amount was adjusted to 7.0% by weight. Similarly, a filter paper having a Gurley rigidity of 1930 mgf was obtained. The physical properties and filter characteristics of this filter paper were measured. A part of the filter paper is further treated at 400 ° C for 2 hours,
Its physical properties were measured. Table 2 shows the measurement results.

[0031] Note) 1) As for the crease strength of 400 ° C treatment V, the one with creases was used in advance.

2) The above quality evaluation methods are as follows.

Quality Evaluation Method: (1) Adhesion of Inorganic Binder The weight of the base paper and the weight of the inorganic binder solution applied and dried were measured, and the weight increase relative to the weight of the base paper was divided by the weight after drying. Display as a percentage. (2) Gurley stiffness According to Japan Tappi No 40, length 63.
A piece of paper having a width of 5 mm and a width of 25.4 mm is sampled so that the machine direction is the long side and measured. (3) Tensile Strength A filter paper of 25.4 mm sampled from the machine direction is also deformed and measured at a span length of 100 mm and a tensile speed of 15 mm / min. (4) Tensile strength with folds A 25.4 mm test piece, which was also taken from the machine direction, was applied to a square plate with a thickness of 1 mm, bent at 180 ° and bent five times, and then the tensile strength was measured under the conditions shown in (3). To do. (5) Pressure loss For filter paper with an effective area of 100 cm ² , the surface velocity is 5.3 c.
Ventilate at m / sec and measure. (6) Collection efficiency Dioctyl phthalate (DOP) particles with a size of 0.3 μm are generated, and a self-made device is used to ventilate the upstream side of a filter paper with an effective area of 100 cm ^{2 at} a surface wind velocity of 5.3 cm / sec, and to obtain the upstream and downstream sides. The particle concentration was measured using a laser particle counter and was determined by the following formula: Collection efficiency (%) = (1-downstream particle concentration / upstream particle concentration) × 100 (7) Dust generation Periodically on filter paper The generated dust is introduced into a laser particle counter, and the number of dust generated per minute is measured. (8) Water repellency US Army Standard MIL-STD-282, Method6
It is measured according to 03.1.

[0034]

【effect】

(1) Since the filter paper of the present invention has an appropriate Gurley rigidity, workability of pleating is improved and at the same time,
When the filter element is formed, it is not necessary to reinforce the filter paper, and the structure of the filter element is simplified.

(2) Compared with a filter paper containing no binder, the water resistance and heat resistance are improved, and it can withstand continuous use at a high temperature of 400 ° C., and troubles such as strength reduction due to water adhesion can be avoided.

(3) Since it has a high dust collecting ability and suppresses dust generation from the filter paper, which has been a big problem in the past, even when the external conditions such as temperature, air volume and shock are changed, A space with a high degree of air cleanliness can be created on the stable downstream side.

Claims (2)

[Claims] 1. A glass for heat-resistant air filters, which contains 1 to 7% by weight of a condensate formed from an alkoxysilane based on the total weight of filter paper, and has a Galley rigidity in the machine direction of 500 to 2000 mgf. Fiber filter paper. 2. The method for producing the glass fiber filter paper for a heat resistant air filter according to claim 1, wherein after the pleating process, an alkoxysilane solution is applied and then dried and condensed.