JPS6322849B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a material that can survive fluids containing acidic substances at high temperatures for long periods of time. Conventionally, materials such as glass fiber and asbestos have been used as materials for fluids that are at high temperatures (approximately 150°C or higher) and contain acidic substances (e.g. gases such as SO ₂ , SO ₃ , H ₂ SO ₄ , Hcl, etc.). Inorganic fibers or organic heat-resistant synthetic fibers such as aromatic polyamide fibers have been used. However, the former has excellent heat resistance but poor bending durability, and the fabric made of this has the disadvantage of being severely damaged when dust is removed and has a short service life. However, it had the disadvantage that it could be hydrolyzed by acid, resulting in a decrease in strength. In order to solve these problems, it has been proposed to coat the surface of heat-resistant synthetic fibers with a hydrolysis-resistant resin, such as a fluorocarbon resin or a silicone resin. The present applicant has previously proposed an acid-resistant fabric in which the acid resistance of organic heat-resistant synthetic fibers, particularly nitrogen-containing heat-resistant fibers, is improved. (Japanese Patent Publication No. 51-34586) This patent describes an acid-resistant material made by coating the fiber surface of a sheet-like structure made of nitrogen-containing heat-resistant fibers with an N-methylol resin in an amount of 2 to 20% by weight of the fibers. It has good acid resistance and can be used as a material for filtering dust with a relatively low acid gas concentration (SO ₂ concentration of several hundred ppm or less). However, its acid resistance is not satisfactory for use as a material for filtering dust with a high acid gas concentration, and there has been a demand for the development of a material with even higher performance, durability, and acid resistance. For example, a compound (A) having at least one methylol group in the molecule and the general formula It consists of the compound (B) shown by, and the ratio is (A)/(B)
= 1/9 to 9/1 (weight ratio) of 1 to 20 wt.
53-35100) has been proposed. but,
In this method, as shown in the example,
It is difficult to say that the acid resistance is at a satisfactory level. The inventors of the present invention have conducted extensive studies in order to meet such demands, and as a result, a fluorinated alkyl (meth)acrylate resin, which is known as a fluorine-based fiber treatment agent, or a resin having a fluorine bond in the main chain is added to the N-methylol resin. The inventors have discovered that acid resistance can be greatly improved by coating aromatic polyamide fibers with the resin composition obtained above, and have thus arrived at the present invention. That is, the present invention is an acid-resistant material formed by coating the fiber surface of a sheet-like structure made of aromatic polyamide fibers with a resin blend made of an N-methylol resin and a fluorine resin. In the present invention, the aromatic polyamide fiber is a polymer in which the repeating structural units are substantially -NH.Ar.
NH.COAr'CO― or -NH―Ar―CO― (However,
Ar and Ar' are aromatic polyamide fibers represented by the same or different aromatic rings), such as a condensation polymer of metaphenylene diamine and isophthalic acid chloride, a condensation polymer of paraphenylene diamine and terephthalic acid chloride, etc. Examples include polymers and copolymers obtained by copolycondensation of metaphenylenediamine, paraphenylenediamine, isophthalic acid chloride, terephthalic acid chloride, and the like. Also as Ar

[Formula] (Y: -O-, -SO ₂ -, -CH ₂ ), etc. can also be included as a copolymer component. In the present invention, the N-methylol resins include melamine resins (resins produced by addition condensation of melamine and formalin), urea resins (resins produced by addition condensation of urea and/or modification, and urea melamine formalin resins). ), an initial condensation polymerization composition in which N-methylol groups mainly contribute to the condensation crosslinking reaction, such as acrylamide resin (acrylamide alone or a copolymer of a vinyl monomer mixture containing acrylamide as a main component), or the like. Refers to products whose main component is polycondensation products. In use, these resins can be used alone, or mixtures or reactants thereof can be used. The fluorine-based resin referred to in the present invention is a polyfluoroalkyl group-containing water and oil repellent agent known as a water and oil repellent having the general formula _CH2 =C( ^R1 )COO(R)mRf (where Rf in the formula has 3 to 3 carbon atoms). 20 linear or branched perfluoroalkyl groups, R ¹ is a hydrogen atom or a methyl group, R
does not contain an acrylate or methacrylate polymer represented by a linear or branched divalent alkylene group having 1 to 10 carbon atoms (m indicates 0 or 1, respectively), or a polyfluoroalkyl group with these Polymerizable compounds such as (meth)acrylic acid and its alkyl ester, (meth)acrylamide and its N-methylol compound, copolymers of one or more of vinyl acetate, etc., known as fluororesins or fluororubbers. Polymers or copolymers containing fluorine bonds in their main chains, such as tetrafluoroethylene, tetrafluoroethylene-propylene copolymers, vinyl fluoride-hexafluoropropylene copolymers, etc. In use, these resins can be used alone or in combination. The material of the present invention is a sheet-like structure such as a woven or knitted fabric or a nonwoven fabric made of the aromatic polyamide fiber described above, and the fiber surface thereof is coated with a resin blend of an N-methylol resin and a fluorine resin. When the fiber surface is coated with N-methylol resin, the resin coats the fiber surface very well, and the resin itself has relatively good acid resistance against acidic substances, making it a material with good acid resistance. can be obtained. On the other hand, fluorine-based resins, i.e., fluorinated alkyl (meth)acrylate resins known as fluorine-based fiber treatment agents, or resins with fluorine bonds in their main chains are resins with good acid resistance. Impregnate the material with the aqueous dispersion obtained by emulsification,
When dried and coated on the fiber surface, the resin does not cover the fiber surface well and does not form a uniform coating, so even if the resin itself has good acid resistance, the resin-coated material may not have good acid resistance. It won't happen. The present inventors have found that a resin compound in which a fluorine-based resin is blended with an N-methylol resin has extremely good coating properties on the fiber surface, and the acid resistance of the blended resin itself is also good. It was discovered that the treated material has extremely good acid resistance, and the present invention was developed based on this finding. Therefore, the acid resistance of the material depends on the blending ratio of the N-methylol resin and the fluorine resin, and the preferred resin blending ratio is 98:2 to 70:30 by weight. When the blending ratio of the fluorine-based resin is 2% or less, the coating properties of the resin blend on the fiber surface are good, but
The resin itself has little effect on improving acid resistance, and on the contrary,
% or more, the acid resistance of the resin itself improves, but the coverage of the fiber surface gradually decreases, and the effect of improving acid resistance also decreases. As a method for coating the fiber surface of a sheet-like structure made of aromatic polyamide fibers with such a resin compound, the fiber surface may be coated with resin in advance and used for knitting or non-woven fabric, but N
- When a methylol-based resin is attached, the fibers generally harden, which impairs processing efficiency and reduces productivity, so it is more advantageous to attach it after forming a sheet-like product. The aqueous resin solution preferably contains a crosslinking agent, a catalyst, and the like. Such crosslinking agents and catalysts include catalysts that promote the condensation reaction of N-methylol resins, such as free acids, alkalis,
Ammonium salts such as diammonium phosphate, rhodanammonium, ammonium chloride, 2-methyl-2-aminopropanol hydrochloride, morpholine hydrochloride,
Examples include organic and inorganic acid salts of aliphatic amino alcohols such as 2-aminobutanol phosphate and triethanolamine hydrochloride, and metal salts such as magnesium chloride, zinc nitrate, and zinc chloride. Although the amount of coating cannot be uniformly determined depending on the type of resin used, the type and thickness of fibers, it is 4 to 20% by weight, preferably 5 to 15% by weight, based on the weight of the fibers. If it is less than 4%, the effect of improving acid resistance is poor, and if it exceeds 20%, the effect of improving acid resistance is saturated, and conversely, the material becomes hard and clogs occur.
Resin treatment is N-methylol resin, fluorine resin,
This is carried out by mixing a predetermined amount of a crosslinking agent and water and attaching the mixture to the fiber surface of a sheet-like structure made of aromatic polyamide fibers. N when mixing resin
- Methylol resins are usually obtained in the form of aqueous solutions, and fluorine resins are obtained in the form of emulsions, but depending on the type of emulsifier, the emulsions may be destroyed during mixing, and such emulsifiers should be avoided. . Examples of resin treatment methods include butt method, dipping method,
Examples include coating method and spray method. After applying a liquid resin to the fiber surface with a uniform thickness by these methods, the fiber (fabric) is dried at a temperature of about 80 to 130°C. At that time, if a coarse fabric is treated with resin, you may use any dryer such as a shoot loop dryer, non-touch dryer, or tenter, but if a particularly dense fabric is treated with resin, For the purpose of preventing clogging caused by the fabric, it is preferable to dry the fabric using suction power such as a suction drum dryer, or to remove clogging from the fabric using a vacuum dehydrator before drying and then drying with an arbitrary dryer. .
After drying, it is desirable to perform curing at approximately 130 to 170°C for several minutes. As mentioned above, the material of the present invention has acid resistance and heat resistance by selecting aromatic polyamide fiber as a highly heat resistant fiber and coating the surface with a resin mixture containing N-methylol resin and fluorine resin. It is made of a material with excellent bending abrasion resistance and dust collection properties, and is suitable for high temperature and acidic fluids (especially gases).
can be used directly and efficiently without prior dilution or temperature cooling treatment, and even if clogging occurs, it can be regenerated by "blowing off", so it can be used for a long period of time. Factories containing acid gases or acids from boilers (for burning heavy oil or coal), blast furnaces, converters (combustion furnaces), open hearths, roasting furnaces, sintering furnaces, drying furnaces, cupolas, or waste incinerators. Drainage, etc. can be efficiently disposed of. Next, the present invention and its effects will be explained with reference to Examples. In addition, "strength retention rate" indicating heat resistance and acid resistance in the example is expressed as the ratio of tensile strength of the fabric before and after attaching concentrated sulfuric acid to a 5 cm wide cloth and heating it, and "% strength retention rate" other than "strength retention rate" ” are all “% by weight”. Examples 1 to 5, Comparative Examples 1 to 6 A resin solution having the five types of compositions shown in Table 1 below was applied to a fabric (surge) made of polymetaphenylene isophthalamide fiber with a basis weight of 250 g/m ² using the pad method. After adhering 8% (as resin) to the fabric, each was dried at 120°C for 5 minutes, and then cured at 150°C for 3 minutes.
In addition, to adjust the resin liquid, add the specified amount of the components shown in each example.
After weighing, the mixture was mixed and stirred until uniform. The five resin-treated fabrics were immersed in a 10% aqueous sulfuric acid solution and heated at 150°C for 1 hour, after which the strength retention of the fabrics was measured. Let the result be F-1. Then, the same process was repeated three times to measure the strength retention rate of the fabric, and the result was designated as F-4. The results obtained are shown in Table 1. For comparison, the same fabric used in the above example was used as it was, or a fabric treated with only N-methylol resin without adding fluorine resin (8% resin attached to the fabric) was used. The fabric was treated with sulfuric acid in the same manner as above, and the strength retention rate of the fabric was determined. The results obtained are shown in Table 1.

【table】

[Table] Examples 6 to 9, Comparative Examples 7 to 9 Resin liquids having the four types of compositions shown in Table 2 below were applied to a fabric made of polymetaphenylene isophthalamide fibers by a patting method at a rate of 12% per fabric. % (as resin) 100℃ after adhesion
Dry for 3 minutes. Then, curing was performed at 150°C for 3 minutes. The strength retention rates of the two types of resin-treated fabrics after acid treatment were measured in the same manner as in Example 1, and the results are shown in Table 2. For comparison, the strength retention rate of a fabric treated with only N-methylol resin without adding fluorine resin is shown.

[Table] Examples 10 to 12, Comparative Examples 7 and 8 Five 20-count twin yarns obtained by spinning 2-denier, 51-mm-long polymetaphenylene isophthalamide fibers
Sheet satin structure Number of implants: 79 pieces/inch x 52 pieces/inch/(vertical) x
A resin solution having the composition shown in Table 3 below was applied to a fabric (weave weight: 323 g/m ² ) which was woven into a (horizontal) fabric and heat-set at 190°C by a batting method at a rate of 7% (as resin) per fabric. 100℃ after
Drying was carried out for 3 minutes at 170°C, followed by curing for 3 minutes at 170°C. The strength retention rate of this resin-treated fabric after treatment with sulfuric acid was measured in the same manner as in Example 1, and the results are shown in Table 3. For comparison, the strength retention rate after sulfuric acid treatment of a fabric treated with a resin solution having a composition ratio of N-methylol resin and fluorine resin other than the scope of the claims of the present invention is shown. From this table, it is clear that the blending ratio of N-methylol resin and fluorine resin greatly affects the acid resistance of the material.

[Table] Examples 13 to 16, Comparative Examples 12 to 14 Number of 20 count twin yarns obtained by spinning 2 denier, 51 mm long polymetaphenylene isophthalamide fibers: 32 yarns/inch x 32 yarns/inch/ (vertical) x (horizontal) plain weave fabric, use this fabric as the base fabric, 2 denier,
A web made of 71 mm long polymetaphenylene isophthalamide fibers through a conventional carding machine was needle punched to obtain a nonwoven fabric with a basis weight of 450 g. Resin liquids having the composition shown in Table 4 below were applied to this nonwoven fabric at varying concentrations, and then dried at 120°C for 10 minutes, and then cured at 165°C for 5 minutes. The strength retention rate of this resin-treated nonwoven fabric after treatment with sulfuric acid was measured in the same manner as in Example 1, and the results are shown in Table 4. For comparison, the strength retention rate after treatment with sulfuric acid of a nonwoven fabric whose resin adhesion amount is outside the scope of the claims of the present invention is shown. As a result, if the amount of resin adhesion is small, the acid resistance will not be satisfactory, and if the amount of resin adhesion is too large, the acid resistance will reach saturation.
On the other hand, it is undesirable as a material because it becomes too hard and causes clogging.

【table】

[Table] Example 17 As a method for evaluating the acid resistance of the filter fabric, Examples 3, 5, 7, 13,
14, Comparative Examples 1, 4, 6, 12, and 13. Table 5 shows the results of the study on the fabrics shown in Comparative Examples 1, 4, 6, 12, and 13. The method for evaluating the sulfuric acid concentration of 5% by weight is the method described in the prior documents, JP-A-52-91999 and JP-A-53-35100.

[Table] Return.

Claims (1)

[Scope of Claims] 1. A resin compound in which the blending ratio (weight ratio) of N-methylol resin and fluorine resin is 98/2 to 70/30 on the fiber surface of a sheet-like structure made of aromatic polyamide fibers. Acid-resistant material that coats objects. 2. The acid-resistant material according to claim 1, wherein the fluorine-based resin is a fluorinated alkyl (meth)acrylate-based resin. 3. A resin blend of N-methyl roll resin and fluorine resin is added to the aromatic polyamide fiber amount from 4 to 4.
The acid-resistant material according to claim 1, which is coated with 20% by weight. 4. The acid-resistant material according to claim 1, wherein the N-methylol resin is a mixture of a urea resin, a melamine resin, and/or an acrylamide resin. 5. Claim 1, wherein the aromatic polyamide fiber is polymetaphenylene isophthalamide fiber.
Acid-resistant material as described in section.