JPS6140791B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to polyamide fibers in which the inner and outer layers of the fibers have different modification states, and a method for producing the same. More specifically, the present invention provides a modified polyamide fiber with excellent hygroscopicity, no yellowing, and less damage to the skin, and a method for producing the same. Various attempts have been made in the industry to modify polyamide fibers by graft polymerizing them with acidic vinyl monomers such as acrylic acid, including the one described in Japanese Patent Publication No. 7248/1973. ing. In addition, attempts have been made widely in the industry to make the properties of polyamide fibers more hydrophilic by graft polymerizing the aforementioned acidic vinyl monomers, then treating them with an aqueous alkali solution and substituting them with alkali metals. However, since such modified polyamide fibers are finally treated with an alkaline aqueous solution, alkali remains in the fibers, and when applied to things that come into direct contact with the human body, such as underwear, it may cause allergic reactions to people with allergies.
Not only is there a risk of skin damage, but the modified polyamide fiber itself has a major problem in that it is susceptible to yellowing due to residual alkali. The present invention solves these problems and provides polyamide fibers that are highly compatible, safer in terms of human health, and less likely to yellow. In order to solve such problems, the present invention has the following features:
After graft polymerizing acidic vinyl monomers onto polyamide fibers, alkali metal substitution is carried out by treatment with an aqueous alkali solution, and then neutralization of the fiber surface layer with a weak base salt of a strong acid makes the fibers relatively stable. To provide a modified polyamide fiber whose inner layer (core) is rich in acidic groups substituted with an alkali metal, and whose surface layer (sheath) is relatively rich in acidic groups which are not substituted with an alkali metal. It is. Here, the content of the present invention will be explained in more detail. The polyamide fibers referred to in the present invention include nylon 4, nylon 6, nylon 6/6, nylon 8,
It may be a polymer or copolymer of nylon 10, nylon 6/10, nylon 12, or a modified nylon, and these polyamide fibers may be blended or copolymerized with other polymers. It can be anything. Examples of graft polymerized forms include staples, tows, filaments, tops, knitted fabrics, woven fabrics,
It may be made of nonwoven fabric, sheet, etc., and is not particularly limited. The acidic vinyl monomer used in the present invention is
Vinyl monomers having ionic groups such as carboxylic acid and sulfonic acid, such as acrylic acid, methacrylic acid, allylsulfonic acid, and styrenesulfonic acid. In order to obtain the modified polyamide fiber of the present invention, acrylic acid and methacrylic acid are particularly advantageous because they are easy to graft polymerize. To explain a typical example of the graft polymerization method employed in the present invention, first, fibers are subjected to activation treatment in order to initiate polymerization. Examples of this method include pre-treatment or simultaneous treatment with an oxidizing agent such as ammonium persulfate or potassium persulfate, or a method in which radicals are generated in the fiber in advance by electron beam radiation. A typical example is a method in which polyamide fibers are modified by generating radicals using such a method and then performing immersion heat treatment or pad steam treatment in an aqueous solution of an acidic vinyl monomer such as acrylic acid or methacrylic acid. However, the graft polymerization method in the present invention is not limited to these. Next, typical examples of the alkali metal used in the alkali metal substitution of the present invention include metal elements such as sodium and potassium. The alkaline aqueous solution used in the present invention includes Na ₂ CO ₃ , K ₂ CO ₃ ,
Examples include compounds that exhibit alkalinity when dissolved in water, such as NaOH, KOH, sodium acetate, and potassium acetate. Furthermore, the term "weak base salt of a strong acid" as used in the present invention means a compound that can be converted to an acidic side by being subjected to heat treatment such as ammonium chloride, ammonium sulfate, hydrochloride or sulfate of various organic amines. At that time, the amount of these compounds used depends on the amount of acidic group introduced,
Although it varies depending on the degree of modification of the target fiber, the amount of fiber adhesion is usually 3.5 x 10 ^-3 mol/kg fiber to 2.0 x 10 ^-1 mol/kg fiber.
A range of fibers is preferred. If the amount is less than this range, the degree of neutralization of the surface layer of the fibers will be low, and it will not be possible to sufficiently improve safety in terms of skin damage and quality stability in terms of yellowing of the product, which is the objective of the present invention. There is a risk. Further, if the above range is exceeded, the neutralization phenomenon may proceed too much and the neutralization reaction may proceed to the inside of the fiber, resulting in a disadvantage that the hydrophilicity, which is a basic characteristic of the modified polyamide, may be reduced. Note that when a general inorganic acid or an organic acid is used for neutralization instead of the weak base salt of a strong acid of the present invention, it is difficult to neutralize only the surface layer of the fiber, and the inner layer of the fiber is also neutralized. Therefore, the hydrophilicity, which is a basic property of modified polyamide, is lost, so it cannot be said to be a useful means. In addition, when graft polymerizing acidic vinyl monomers such as acrylic acid, the amount of graft polymerization varies depending on the purpose in order to impart good hydrophilicity to polyamide fibers, but it is usually 1% to the weight of the fibers.
Preferably, a proportion of ~10% is grafted. For example, when converted to the number of moles of carboxyl group,
Approximately 1.4×10 ^-1 mol/kilogram fiber ~ 1.4
If the value is lower than this value, it is difficult to provide good hydrophilicity, and if it exceeds this value, it is not only industrially unprofitable but also has poor shrinkage properties and dimensional stability. This may result in a product with poor quality. When the alkali metal substituted material of the modified polyamide graft-polymerized to such a degree is subjected to surface neutralization treatment with a weak base salt of a strong acid, the surface layer of the fiber becomes relatively rich in acidic groups, and the fiber becomes relatively rich in acid groups. The inner layer is rich in acidic groups substituted with alkali metals, which can be clearly determined by staining with a cationic dye. In other words, cationic dyes dye by reacting with acidic groups, but at this time, the dyeing reaction occurs at a much faster rate when the acidic groups are substituted with an alkali metal than when they are not. Therefore, the modified polyamide fiber of the present invention can be distinguished from this difference in dyeing reaction speed. That is, when the modified polyamide fiber of the present invention is cut in the cross-sectional direction and the cut section is dyed with a cationic dye (especially blue dye is better), the inner layer (core) of the fiber is dyed deeply, and the surface layer ( The sheath) is lightly dyed. This becomes even more apparent when observed under a microscope.
can be clearly identified. Of course, when modified polyamide fibers that have not been subjected to the conventional surface neutralization treatment using a weak base salt of a strong acid are dyed with a cationic dye, the hue density of the fiber cross section becomes uniform.
In addition, in the case of polyamide fibers that have not undergone normal modification, the dyeing is only slightly uniform.
The amount of dyeing with cationic dyes is extremely small. As a result of conducting a 48-hour human test using the modified polyamide fiber of the present invention as a patch test medical material manufactured by Torii Pharmaceutical Co., Ltd., it was found that the modified polyamide fiber was not treated with the conventional weak base salt of a strong acid. Some people with allergies to fibers developed red rashes, but the products of the present invention had no such phenomenon, proving that they are extremely safe in terms of human health. Next, the product of the present invention, conventional modified polyamide fibers that are not treated with weak base salts of strong acids, and regular polyamide fibers were placed in separate packaging bags and left in a room exposed to sunlight for a long time without being sealed. Did. Separately, a test was conducted in which each of the above-mentioned samples was put through a bag with a rubber string and left in a room where a kerosene heater was used for a long time. It was found that the modified polyamide fibers showed almost no yellowing phenomenon, but the conventional modified polyamide fibers suffered from the yellowing phenomenon, and the quality of the products tended to be extremely low. As described above, it can be seen that the modified polyamide fiber of the present invention has high hydrophilicity, has no effect on the human body, and is an extremely stable and good quality fiber without yellowing. The present invention will be further explained below with reference to Examples. Example 1 A processed yarn jersey made of nylon 6 fibers was prepared using an aqueous solution containing 0.2 parts of ammonium persulfate as a polymerization initiator.
After processing at 70℃ for 30 minutes, add 3 parts of acrylic acid,
It was treated with an aqueous solution consisting of 97 parts of water at 95°C for 30 minutes. By titration with caustic soda and hydrochloric acid, it was found that the carboxyl group in this product was 7.2 x 10 ^-1 mol/kilogram fiber. Next, this treated fabric was treated in an aqueous solution consisting of 5 parts of soda ash and 95 parts of water at 95°C for 30 minutes to impart extremely excellent hydrophilicity. Then ammonium chloride 0.2
After immersing the fiber in an aqueous solution consisting of 99.8 parts of water and 99.8 parts of water, the fiber was squeezed with a mangle so that the amount of ammonium chloride deposited was 3.8 x 10 ^-2 mol/kg of fiber, and a dry heat treatment was performed at 170°C for 2 minutes. The fabric thus obtained was highly hydrophilic and of high quality, causing no skin damage and not causing yellowing during storage. As a reference, a cloth that was not treated with ammonium chloride (Reference Example A) and an untreated cloth (Reference Example B) of this Example were compared and evaluated, and the results were as shown in the following table.

【table】

[Table] Example 2 Half tricots made of nylon 66 fibers were pretreated with an aqueous solution consisting of 0.5 parts of potassium persulfate and 99.5 parts of water at 80°C for 30 minutes, and then treated with 5 parts of methacrylic acid.
and 95 parts of water at 95°C for 60 minutes. A neutralization titration reaction of this material with caustic soda and hydrochloric acid revealed that the carboxyl group was 3.0 x 10 ^-1 mol/kg fiber. Next, the treated fabric was heat-treated at 95°C for 60 minutes with an aqueous solution consisting of 10 parts of soda ash and 90 parts of water, washed with water, dried, and then padded with an aqueous solution of 0.3 parts of ammonium sulfate and 99.7 parts of water using a mangle. rear,
Dry heat treatment was performed at 170°C for 1 minute using a pin tenter. This product was found to be extremely hydrophilic and of high quality, causing no skin damage or yellowing during storage. Tests were conducted using acetic acid (Reference Example C) and phosphoric acid (Reference Examples D and E) in place of ammonium sulfate, but none of them satisfied the objectives of the present invention detailed in the text. The following table summarizes these results.

[Table] Example 3 A 2.5 denier, 51 mm staple made of nylon 6 fibers was packed into a package dyeing machine and heated at 98°C in an aqueous solution consisting of 0.2 parts of ammonium persulfate and 99.8 parts of water.
× After pretreatment for 30 minutes, add 2 parts of acrylic acid and 98% of water.
The temperature was raised from room temperature to 70°C with an aqueous solution consisting of 30% of the sample, and heat treatment was performed at that temperature for 30 minutes. Subsequently, after washing with water, treatment is performed at 98℃ for 30 minutes with a solution of 2 parts of soda ash and 98 parts of water. A jersey fabric was knitted at. After that, the knitted fabric with the jersey structure is treated with ammonium chloride.
Patiding with a solution consisting of 0.3 parts and 99.7 parts of water,
Drying treatment was performed at 170°C for 1 minute, as detailed in the text. A high-quality knitted fabric with high hydrophilic skin damage and no yellowing phenomenon during storage was obtained.

Claims (1)

[Scope of Claims] 1. A modified polyamide fiber in which the inner layer portion has an acidic group substituted with an alkali metal, and the surface layer portion has an acidic group not substituted with an alkali metal. 2. Graft polymerizing an acidic vinyl monomer onto polyamide fibers, then subjecting the acidic groups introduced by the graft polymerization to an alkali aqueous solution with an alkali metal substitution treatment, and further neutralizing the fiber surface with a weak base salt of a strong acid. A method for producing characteristically modified polyamide fibers.