JPH1133321A - Resin-impregnated filter-paper for filtering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide filter paper impregnated with resin for filtering having high rigidity of B-stage (drying) paper, omitting a C-state (curing) which has conventionally been necessary for impregnated paper, or having extremely less volatile phenols even if the C-stage is conducted. SOLUTION: Aldehydes and phenols are combined so that a molecular ratio of aldehydes/phenols is 1.0-1.5. Filter paper is impregnated with phenolic resin in which a free phenols to 100 parts of a resin solids content is 1% or less and an ash content per solid content of phenolic resin is 0.5% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a resin-impregnated filter paper for a filter.

[0002]

2. Description of the Related Art Conventionally, filters obtained by impregnating a thermosetting resin, particularly a phenolic resin, in a filter paper and thermosetting have been widely used for industrial machines such as machine tools and automobiles.
Specifically, it is used for air filters, engine oil filters, fuel filters, oil filters, and the like.

[0003] Air filters, oil filters, fuel filters, and the like for machine tools and automobiles are prepared by impregnating filter paper with a resol-type phenol resin and volatilizing the solvent to obtain a B (dry) state. Next, the impregnated paper with B is wound up by corrugating, and in the next step, the impregnated paper is pleated by folding the impregnated paper, and then C (hardened), and then the end plate is attached. Manufactured. The filter obtained from the thermoset resin-impregnated filter paper in the C-form in this way has good water resistance, heat resistance, oil resistance, high burst strength, toughness, and air permeability,
It has the feature of high filtration efficiency.

[0004]

However, the resol type phenol resin generally used for filters has a binding molar ratio of phenols to aldehydes of 0.8: 1.0 to 1.1: 1.0. It is obtained by reacting. The resol type phenol resin obtained by reacting at such a molar ratio contains about 12 to 20% of free phenols with respect to the solid content. Since the content of free phenol resin is high, phenol mononuclear bodies such as phenol monomer and methylolated phenol are scattered in the B-forming and C-forming processes, and the concentrations of phenols and formaldehyde in the exhaust gas are polluted. It is considered a problem from the above point of view.

[0005] Further, the step of curing the resin-impregnated filter paper (C)
), Usually at 140 to 180 ° C for 5 to 20
Need a minute. This C-conversion process consumes a large amount of heat and time, and should be omitted or improved from the viewpoint of energy saving and rationalization of production, and such demands are strong.

On the other hand, the filter itself has been devised to increase the surface area of the filter paper in order to reduce the size and improve the filtration efficiency. In order to perform such a complicated folding process, it is desired to improve the rigidity of the filter paper.

[0007]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have made intensive studies on the reaction molar ratio between phenols and aldehydes and found that the above-mentioned problems can be achieved with a specific molar ratio. Thus, the present invention has been completed.

That is, according to the present invention, the aldehyde / phenol is present in a molar ratio of aldehyde / phenol of 1.
0 to 1.5 and a resin solid content of 10
A filter resin-impregnated filter paper obtained by impregnating a filter paper with a phenol resin containing 1% or less free phenols per 0 parts, preferably a filter resin impregnation having an ash content of 0.5% or less per solid content of the phenol resin. Provide filter paper.

According to the present invention, there is provided a resin-impregnated filter paper in which the amount of volatile phenols during the conversion to B and C is reduced to 1% or less, and the amount of volatile phenols in the conversion to B and C is suppressed as much as possible. The purpose is to: Further, when used as an oil filter, it has sufficient rigidity as a filter only in the B-forming step, so that it can be used without performing the C-forming treatment. In this case, since the engine oil filter has a high temperature of 80 to 140 ° C., the resin is heated and cured in the oil, and can exhibit sufficient strength.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As the phenolic resin of the present invention, any of a resol type phenol resin and a novolak type phenol resin can be used, but a resol type phenol resin is preferable. The novolak-type phenol resin must use a curing agent that serves as a formaldehyde supply source such as hexamethylenetetramine, and these curing agents have to be added to the impregnated resin solution, which is problematic in workability. Liquids in which these curing agents are dissolved also have problems in stability of the compounding liquid, such as an increase in viscosity and a decrease in solvent diluting ability. Further, when hexamethylenetetramine is added, ammonia gas is generated at the time of curing of the resin, and there is a problem in sanitary environment.

Specific examples of the resole type phenol resin include a phenol resin obtained by reacting a phenol and an aldehyde in the presence of an alkali catalyst, and a phenol resin obtained by further reacting a novolak phenol resin with formaldehyde. No. In addition, a novolak phenol resin can be used in combination with a resol phenol resin. In this case, it is preferable not to add a curing agent for a novolak type phenol resin such as hexatetramethylenetetramine for the above-mentioned reason. When a novolak type phenol resin is used in combination, the content is preferably 50% by weight or less based on the total phenol resin from the viewpoint of the physical properties of the filter.

Phenols that can be used at this time are preferably phenol in terms of heat resistance and cost.
Some phenol derivatives may be used. Examples of the phenol derivative include m-cresol, p-cresol, o-cresol, 3,5-xylenol, resorcinol, alkylresorcinol, bisphenol A, bisphenol F, α-naphthol, β-naphthol, 1,6
And dihydroxynaphthalene and the like, and these may be used in combination of two or more.

The aldehydes include, for example, formaldehyde (formalin), paraformaldehyde, acetaldehyde, trioxane, etc. Among them, formaldehyde or paraformaldehyde is preferred in view of price and performance.

The method for reducing the free phenols to 1% or less is not particularly limited. For example, aldehydes / phenols = 0.7 to 1.5 and a resol type resin synthesized using an alkaline catalyst. A method of removing phenols by thin film distillation or the like, or a novolak reaction using an aldehyde / phenols of 0.6 to 0.8 with an acid catalyst, and then removing the phenol by steam distillation, high temperature distillation, thin film distillation, or the like. Alternatively, the novolak resin from which phenol has been removed by washing with water is further resolulated with an aldehyde and an alkali catalyst.

Any known alkaline catalyst for the resolving reaction can be used. As the alkaline catalyst,
Alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide; carbonates such as alkali metal such as sodium carbonate; carbonates such as alkaline earth metal such as calcium carbonate Examples thereof include amine compounds such as salts, alkanolamines, alkylamines, and ammonia.

It is also possible to use hexamethylenetetramine as an aldehyde supply source and a catalyst source.
Any known acidic catalyst can be used for the novolak reaction. Examples of the acidic catalyst include inorganic acids such as hydrochloric acid, sulfuric acid, and phosphoric acid, and organic acids such as phenolsulfonic acid, paratoluenesulfonic acid, oxalic acid, and formic acid. However, when resolving novolak resin,
Because of the use of an alkali catalyst, when novolacing,
An acid having high temperature decomposability such as oxalic acid is preferred.

The amounts of these resolation catalysts and novolak reaction catalysts are reflected in the ash content in the resin. When a large amount of catalyst is used, that is, when there is a large amount of ash in the resin, the filter processed using the resin tends to have reduced heat resistance, and is used for applications requiring long-term heat resistance such as an oil filter. Not preferred. The ash content of the impregnated filter paper of the present invention is 0.5% per phenol resin solid content.
The following is preferred.

The final bonding molar ratio of the aldehydes and phenols of the present invention is aldehydes / phenols =
It is in the range of 1.0 / 1.0 to 1.5 / 1.0. If the binding molar ratio is lower than that, the rigidity at the time of conversion to C is low, and settling occurs on the filter paper, thereby impairing the filtration efficiency. On the other hand, if the bonding molar ratio is high, the filter paper becomes too hard after C-formation, becomes brittle, and cannot exhibit sufficient burst strength.

The present invention is characterized in that it has the above binding molar ratio and that the free phenol content is 1% or less in the resin solid content. Volatile phenols increase during the chemical conversion, and the phenols that have volatilized adhere to the inside of a curing furnace or a stack for exhaust gas, and further turn into resin by heat. Also,
If discharged into the atmosphere from the chimney without adhering, it may cause air pollution and the like, and a waste gas treatment facility may be required.

Further, when the amount of free phenol is large, the rigidity of the B-modified paper tends to decrease. In recent years, in order to increase the surface area of the filter body and increase the filtration efficiency, there is a tendency that a pleating process (folding process) of filter paper is woven into a complicated shape. In such a complicated pleat process, the folding process conventionally used may be difficult.

Even if the pleating process is performed, the rigidity before the resin is cured in the hot oil is low, so that the filter paper is set before the resin is cured, and the filtration efficiency is greatly reduced.

As the filter paper for a filter used in the present invention, any conventionally known filter paper is preferably used. For example, there is a filter paper for a general filter, which is mainly made of fiber of linter pulp and, if necessary, added with chemical fibers such as rayon and polyester, and made into paper to adjust the air permeability, basis weight, thickness and the like.

The impregnating solution obtained is impregnated into a filter paper for a filter using an impregnating solution having a resin concentration of 5 to 20% by weight. The impregnating solution is impregnated by immersion and squeezing operations, a so-called dip-squeezing method or a specific method. It is carried out by a conventionally known method such as a kiss-coat method of impregnating with a kiss roll using an impregnating liquid having a concentration of 15 to 30 parts by weight of resin solids per 100 parts by weight of filter paper. It is common to use

B-drying of the resin-impregnated paper is performed under normal drying conditions, for example, at 80 to 180 ° C. for 1 to 15 minutes.
Thereafter, the resin-impregnated paper is wound up after corrugating. The B-formed paper thus obtained is subjected to processing such as cutting and creases, and then cured by heating. The drying and heating conditions in the C-forming step are not particularly limited, but are usually 1
The reaction is performed at 00 to 200 ° C. for 1 to 40 minutes.

The resin-impregnated filter paper for a filter thus obtained is cut into a suitable length and assembled as a filter element.

[0026]

EXAMPLES The present invention will be specifically described below with reference to examples. Example 1 A cooling tube, a thermometer, and a stirrer were set in a 2-liter four-necked flask, and 990 g of phenol and 42% formalin 1 were added.
06 g and 6.0 g of oxalic acid were charged and the temperature was raised to 100 ° C. Next, 525 g of 42% formalin is allowed to react while being dropped in 45 minutes. After further reacting at reflux temperature for 6 hours, normal pressure distillation is performed and the temperature is raised to 150 ° C. Then 7
Vacuum distillation is performed at 20 hPa and the temperature is raised to 180 ° C. Furthermore, steam distillation was carried out for 4 hours, and phenol monomer was removed to obtain novolak type phenol resin A.

This novolak type phenolic resin A400
g was dissolved in 100 g of methanol, and 16.2 g of 92% paraformaldehyde and 1.3 g of a 48% sodium hydroxide solution were added. The mixture was reacted at reflux temperature for 6 hours, and methanol was added to adjust the resin concentration to 50%. Cool down,
A uniform resol-type phenol resin solution B was obtained.

The resol type phenol resin solution B has a viscosity of 190 mPa.s, a gel time of 70 seconds, and a phenol monomer content of 0.2% or less (0.4% or less per resin solid content).
Was a resin solution. Further, the binding molar ratio of the resin aldehydes / phenols = 1.0, ash content per resin solid content =
0.18%.

The obtained resin solution was diluted with methanol to obtain a solution having a resin concentration of 20%.
0 g / m ² ), air-dried, and then dried at 100 ° C. for 5 minutes to obtain B-coated paper having a resin amount of 35 g / m ² .

The normal rupture strength of the B-type paper, the oil rupture resistance after immersion in engine oil heated to 140 ° C. for 200 hours, and the bending strength under normal conditions were measured. The B-treated paper was heat-treated at 160 ° C. for 15 minutes to obtain C-treated paper, and the normal burst strength, the oil rupture resistance, and the bending strength were measured in the same manner as the B-formed paper.

Further, phenols and formaldehyde in the gas generated in the C-forming step are collected by passing through water,
The amounts of volatile phenols and formaldehyde were measured. Phenols were quantified by 4-aminoantipyrine absorbance method, and formaldehyde was quantified by acetylacetone absorbance method.

Example 2 To 400 g of the novolak type phenol resin A obtained in the same manner as in Example 1, 100 g of methanol was added and dissolved.
After adding 27.0 g of paraformaldehyde and 1.3 g of 48% sodium hydroxide solution and reacting at reflux temperature for 6 hours, methanol was added to adjust the resin concentration to 50%.
After cooling, a uniform resol-type phenol resin solution C was obtained.

The resol type phenol resin solution C has a viscosity of 205 mPa.s, a gel time of 63 seconds, and a phenol monomer content of 0.2% or less (0.4% or less per resin solid content).
Was a resin solution. Further, the binding molar ratio of aldehydes / phenols of the resin = 1.2, ash content per resin solid content =
0.17%.

Using the obtained resin liquid, the normal burst strength, the oil rupture resistance and the bending strength of the B-formed paper and the C-formed paper were measured in the same manner as in Example 1, and the gas generated during the C-forming was analyzed. Example 3 100 g of methanol was added to and dissolved in 400 g of a novolak-type phenol resin A obtained in the same manner as in Example 1, and 92%
After adding 43.2 g of paraformaldehyde and 1.3 g of a 48% sodium hydroxide solution and reacting at a reflux temperature for 6 hours, methanol was added to adjust the resin concentration to 50%, cooled, and a uniform resol-type phenol resin solution D was added. I got

The resol-type phenolic resin solution D has a resin solid content of 50%, a viscosity of 220 mPa.s, a gel time of 55 seconds,
The resin solution had a phenol monomer content of 0.2% or less (0.4% or less per resin solid content). Further, the binding molar ratio of aldehydes / phenols of the resin was 1.5, and the ash content per resin solid content was 0.17%.

Using the obtained resin liquid, the normal burst strength, the oil rupture resistance, the bending strength of the B-modified paper and the C-modified paper were measured in the same manner as in Example 1, and the gas generated during the C conversion was analyzed. Example 4 100 g of methanol was added to the novolak type phenolic resin A obtained in Example 1 and dissolved, and 27.0 g of 92% paraformaldehyde and 5.9% of 48% sodium hydroxide solution were used.
g was added and reacted at reflux temperature for 6 hours, then adjusted to a resin concentration of 50% with methanol and cooled to obtain a uniform resol-type phenol resin solution I.

The resol type phenol resin solution I has a viscosity of 200 mPa.s, a gel time of 55 seconds, and a phenol monomer content of 0.2% or less (0.4% or less per resin solid content).
Was a resin solution. Further, the binding molar ratio of the resin was aldehydes / phenols = 1.2 and ash content = 0.7%.

Using the obtained resin liquid, the normal burst strength, the oil rupture resistance and the bending strength of the B-modified paper and the C-modified paper were measured in the same manner as in Example 1, and the gas generated during the C conversion was analyzed. Comparative Example 1 100 g of methanol was added to and dissolved in the novolak-type phenolic resin A obtained in Example 1, and 16.2 g of 92% paraformaldehyde and 1.3% of a 48% sodium hydroxide solution 1.3 were used.
g, and reacted at reflux temperature for 6 hours. Then, methanol was added to adjust the resin concentration to 50%, and the mixture was cooled to obtain a uniform resol-type phenol resin solution E.

The resol type phenol resin solution E has a viscosity of 180 mPa.s, a gel time of 75 seconds, and a phenol monomer content of 0.2% or less (0.4% or less per resin solid content).
Was a resin solution. Also, the binding molar ratio of aldehydes / phenols of the resin = 0.9, ash content per resin solid content =
0.19%.

Using the obtained resin liquid, the normal burst strength, the oil rupture resistance, and the bending strength of the B-modified paper and the C-modified paper were measured in the same manner as in Example 1, and the gas generated during the C conversion was analyzed. Comparative Example 2 100 g of methanol was added to and dissolved in the novolak-type phenolic resin A obtained in Example 1, and 48.6 g of 92% paraformaldehyde and 1.3% of a 48% sodium hydroxide solution 1.3 were used.
g, and the mixture was reacted at a reflux temperature for 6 hours. Then, methanol was added to adjust the resin concentration to 50%, and the mixture was cooled to obtain a uniform resol-type phenol resin solution F.

The resol type phenol resin solution F has a viscosity of 215 mPa.s, a gel time of 55 seconds, and a phenol monomer content of 0.2% or less (0.4% or less per resin solid content).
Was a resin solution. Further, the binding molar ratio of the resin aldehydes / phenols = 1.6, ash content per resin solid content =
0.17%.

Using the obtained resin solution, the normal burst strength, the oil rupture resistance, the bending strength of the B-formed paper and the C-formed paper were measured in the same manner as in Example 1, and the gas generated during the C-forming was analyzed. Comparative Example 3 A condenser, a thermometer, and a stirrer were set in a two-liter four-necked flask, and 990 g of phenol and 42% formalin 1 were added.
06 g and 6.0 g of oxalic acid were charged and the temperature was raised to 100 ° C. Next, 525 g of 42% formalin is allowed to react while being dropped in 45 minutes. After further reacting at reflux temperature for 6 hours, normal pressure distillation is performed and the temperature is raised to 150 ° C. Then 7
Vacuum distillation was performed at 20 hPa for 1 hour to obtain a novolak phenol resin G.

This novolak type phenolic resin G400
100 g of methanol was added to the resulting solution, and 27.0 g of 92% paraformaldehyde and 1.3 g of a 48% sodium hydroxide solution were added. The mixture was allowed to react at reflux temperature for 6 hours. Solution H was obtained.

The resol-type phenolic resin solution H was prepared from a resin solid content of 50%, a viscosity of 160 mPa.s, a gel time of 62 seconds,
Phenol monomer content 3% (6 per resin solid content)
%) Of the resin solution. Further, the binding molar ratio of the resin was aldehydes / phenols = 1.2, and the ash content per resin solid content was 1.5%.

Using the obtained resin solution, the normal burst strength, the oil rupture resistance, the bending strength of the B-modified paper and the C-modified paper were measured in the same manner as in Example 1, and the gas generated during the C conversion was analyzed. Comparative Example 4 A condenser, a thermometer, and a stirrer were set in a two-liter four-necked flask, and 750 g of phenol and 42% formalin 5 were added.
70 g and 4.1 g of a 48% sodium hydroxide solution were charged and reacted at 80 ° C. for 3 hours.
Dehydration under reduced pressure was performed at 2 millipascals. After dehydration, the temperature was raised to 90 ° C. while reducing the pressure at 72 mPascal, 200 g of methanol was added, and the mixture was reacted at a reflux temperature for 5 hours. Methanol was added to the mixture to dilute it to a concentration of 50%, followed by cooling to obtain a uniform resol-type phenol resin solution J.

The resol type phenol resin solution J was a resin solution having a viscosity of 95 mPa.s, a gel time of 85 seconds, and a phenol monomer content of 8% (16% per resin solid content). Further, the binding molar ratio of the resin was aldehydes / phenols = 1.0 and ash content = 0.2%.

Using the obtained resin liquid, the normal burst strength, the oil rupture resistance and the bending strength of the B-formed paper and the C-formed paper were measured in the same manner as in Example 1, and the gas generated during the C-forming was analyzed. The results are shown in Tables 1 and 2.

[0048]

[Table 1]

(* 1)% by weight per solid resin. (* 2) ppm by weight based on filter paper.

[0050]

[Table 2]

(* 1)% by weight per solid resin. (* 2) ppm by weight based on filter paper. Examples 1 to 3 have higher flexural strength than Comparative Example 1, and have higher oil rupture resistance than Comparative Example 2. Also, the flexural strength is higher as compared with Comparative Example 3 having a large amount of free phenol. It can be seen that Examples 1 to 3 have higher oil rupture strength and are superior in heat resistance as compared with Example 4 having a large amount of ash.

Further, as compared with the resin of Comparative Example 4 used in the conventional filter, the amount of phenols and formaldehydes volatilized during the formation of C is extremely small.

[0053]

The filter resin-impregnated paper obtained according to the present invention has high rigidity of B-modified paper, and phenols and formaldehyde which volatilize even if C-conversion, which is conventionally required for impregnated paper, is performed, or C-conversion is carried out. There is an advantage that the rationalization in the environment and the production process can be extremely reduced.

Claims (2)

[Claims] An aldehyde and a phenol are combined in a molar ratio of aldehyde / phenol of 1.0 to 1.5, and free phenol is added to 100 parts of resin solid content. % Or less of a phenolic resin impregnated into a filter paper. 2. The impregnated filter paper according to claim 1, wherein the ash content per solid content of the phenolic resin is 0.5% or less.