JP4077009B2 - Method for treating stimulus-responsive open nonwoven fabric - Google Patents

Description

  The present invention relates to a method for treating a nonwoven fabric that can be opened and dispersed in an aqueous medium depending on the pH value of the aqueous treatment medium.

  In the past, care products, sanitary products, diapers, cleaning cloths, etc. (hereinafter sometimes collectively referred to as “hygiene products”) have been used as cloth, but recently, they have been replaced by cloth. Paper and non-woven fabrics are increasingly used. The above sanitary goods made of paper and non-woven fabric can be used up once and are very convenient, so the demand is expected to increase more and more in the future.

  Such sanitary products need to absorb moisture such as urine well, and therefore, paper and nonwoven fabrics used as such sanitary products are in the form of paper and nonwoven fabrics even if they contain moisture. Need to be maintained. For this reason, such sanitary goods are actually formed using water-resistant paper and nonwoven fabrics. Therefore, since these sanitary products are insoluble in water, they cannot be processed by being flushed after using them, and are treated as general garbage.

  However, once used sanitary goods contain dirt, it is desirable to treat them as soon as possible after use. As a method for treating the sanitary article after use, it is very suitable if it can be treated by flowing it into a flush toilet.

  However, as described above, since the hygiene product requires water resistance at the stage of use, the sanitary product after use is naturally excellent in water resistance, and the sanitary product having such excellent water resistance is washed with water. It was not possible to dispose of it in the toilet. Thus, in sanitary goods, the water resistance required at the time of use and the opening property desired after use are contradictory characteristics, and it has been said that the manufacture of sanitary goods having both characteristics is very difficult.

On the other hand, JP-A-4-216889 discloses a water-disintegrating non-woven fabric and a binder that are difficult to dissolve in clean water and body fluid and easy to dissolve in sewage.
This publication specifically discloses a binder having the following composition. “A copolymer having an average molecular weight of 5,000 to 10,000 having an ethylenically unsaturated carboxylic acid or anhydride, a crosslinkable monomer, and a (meth) acrylic acid alkyl ester as essential components. Binder neutralized with a valent alkali. "Here, the crosslinkable unsaturated monomer is shown to be N-methylol (meth) acrylamide or its ether compound.

However, in this binder, since the carboxyl group is neutralized with a monovalent alkali, the monovalent alkali component is dissociated when containing water, and the dissociated monovalent alkali component has irritation to the skin. ing. In addition, in order to allow disintegration in sewage, when using the above-described polymer salt, the amount and structure of the crosslinked structure formed are extremely important factors, and the solubility of these resins is controlled. Therefore, it is extremely difficult to form a crosslinked structure.
JP-A-4-216889

  It is an object of the present invention to provide a method for opening a used stimulus-responsive opening nonwoven fabric.

The treatment method of the stimulus-responsive openable nonwoven fabric of the present invention is:
_{^{-N + R 1 3 · Cl -}} ,

A number of fibers having at least one kind of cationic group selected from the group consisting of (wherein R ¹ is each independently a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms), and —COO _{^{- · H +, -SO 3 -}} · H +, -SO 4 - containing a large number of fibers having a · H ⁺ become more selected from the group at least one anionic group ^- · H ⁺ and -PO ₄ The stimuli-responsive open nonwoven fabric is characterized by being opened by immersing it in an aqueous medium having a pH value of 8 or more.

  Further, the stimulus-responsive openable nonwoven fabric used in the method of the present invention contains a large number of fibers having a cationic group and a large number of fibers having an anionic group. The stimuli-responsive spreadable nonwoven fabric used here is paper-made using a fiber-dispersed aqueous medium in which a large number of fibers having a cationic group and a large number of fibers having an anionic group are dispersed, and then dried. Can be manufactured.

Alternatively, the cationic fiber and the anionic fiber can be entangled with a high-pressure water jet, or the fiber can be mechanically entangled and then immersed in water.
The treatment method of the stimulus-responsive spreadable nonwoven fabric of the present invention is a stimulus-responsive spreadable nonwoven fabric containing a large number of fibers having a cationic group and a large number of fibers having an anionic group, having a pH value of 8 or more. It is characterized in that it is opened in an aqueous medium.

Stimulus response openability nonwoven fabric used in the method of the present _{^{invention, -N + R 1 3 · Cl}} -,

A number of fibers having at least one kind of cationic group selected from the group consisting of (wherein R ¹ is each independently a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms), and —COO _{^{- · H +, -SO 3 -}} · H +, -SO 4 - containing a large number of fibers having a · H ⁺ become more selected from the group at least one anionic group ^- · H ⁺ and -PO ₄ In the acidic region and neutral region, the cationic group and the anionic group introduced into the fiber are ionically and stably bonded to each other. Will not collapse. However, in the alkaline region, since the ionic bond between the cationic group and the anionic group forming the second stimulus-responsive spreadable nonwoven fabric is broken, the bonding force of the nonwoven fabric is lost, and the nonwoven fabric is collapsed. And opened.

  Thus, since the stimulus-responsive spreadable nonwoven fabric of the present invention is opened with an alkaline aqueous solution of a certain value or more, the sanitary article formed from this nonwoven fabric is treated with an alkaline aqueous medium, and is then poured into a flush toilet. It becomes possible to process.

  In the present invention, the acidic region represents a region having a pH value of less than 6, the neutral region represents a range having a pH value of 6 or more and less than 8, and the alkaline region represents a region having a pH value of 8 or more. To do.

The treatment method of the following stimulus-responsive spreadable nonwoven fabric of the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.
The stimulus-responsive openable nonwoven fabric according to the embodiment of the present invention has a fiber itself having a cationic group or an anionic group, and the fiber having a cationic group and the fiber having an anionic group are ionically bonded. It is the nonwoven fabric formed by doing.

  The stimulus-responsive openable nonwoven fabric according to this example is formed from a large number of fibers into which a cationic group or an anionic group is introduced, and examples of fibers before these ionic groups are introduced are as follows: Vegetable fiber such as wood pulp, plant fiber such as cotton fiber, hemp fiber, jute, hemp fiber and cotton linter, animal fiber such as wool and silk, regenerated cellulose fiber such as viscose rayon and copper ammonium rayon, polyolefin Examples thereof include synthetic fibers such as fibers, polyester fibers, polyamide fibers, and acrylic fibers, and composite fibers obtained by combining these fibers. Moreover, the natural fiber and synthetic fiber which have an ionic group in a molecule | numerator beforehand may be sufficient.

The average length of these fibers is usually in the range of 0.1 to 60 mm, preferably 20 to 50 mm, and is usually 0.1 to 20 denier, preferably 0.5 to 1.5 in the present invention. Fibers within the denier range are used.

Examples of cationic group introduced into a fiber constituting the stimulus response openability nonwoven fabric according to the present _{^{embodiment, -N + R 1 3 · Cl}} -,

These cationic groups may be introduced into the fiber alone or in combination. In the above formula, each R ¹ is independently a hydrogen atom or 1 to 3 carbon atoms.
Or —CH ₂ CH ₂ OH. Moreover, these cationic groups may be introduced into the fiber via a spacer such as a — (CH ₂ CH ₂ O) _n — group, a sugar chain, or an alkyl group. Examples of the anionic group to be introduced into the fiber constituting the second stimulus response openability ^{nonwoven, -COO - · H +, -SO} 3 - · H +, -SO 4 - · H +, - PO ₄ ⁻ · H ⁺ can be mentioned, and these cationic groups may be introduced into the fiber alone or in combination. _{Also, - (CH 2 CH 2 O} ) n - group, a sugar chain, may be introduced into the fiber via a alkyl group.

In particular, in this embodiment, the -N ⁺ R ¹ ₃ · Cl as the cationic group ^- and cellulosic fiber group is introduced, as an anionic group, -COO ^- · H ⁺ groups and cellulosic fibers are introduced Are preferably used in combination.

The polar group as described above can be introduced by using a group capable of reacting with the reactive group of the fiber and the polar group-introducing compound having the anionic group or the cationic group. For example, in order to introduce —N ⁺ R ¹ ₃ · Cl ⁻ group into cellulosic fiber,

Can be used to react this polar group-introducing compound with OH groups present in the main chain of the fiber. In the above formulae, R ¹ has the same meaning as described above. Further, for example, in order to introduce —COO ⁻ .H ⁺ group into a cellulosic fiber, ClCH ₂ COONa is used as a polar group introducing compound, and this polar group is introduced into the OH group present in the main chain of the fiber. A method of reacting the introduced compound can be employed. These fibers having a cationic group and fibers having an anionic property are produced separately.

  In the stimulus-responsive openable nonwoven fabric according to this example, the pH value of the aqueous dispersion in which the fibers having the cationic groups and the fibers having the anionic groups are dispersed is usually 2 to 8, preferably 2 to 2. 4 is adjusted. By adjusting the pH value of the aqueous dispersion so as to be weakly acidic in this way, the fibers are bonded to each other and become stable in the acidic region and the neutral region.

  The stimuli-responsive openable nonwoven fabric according to this example is formed of a fiber having a cationic group and a fiber having an anionic group as described above, and a fiber having no cationic group or anionic group However, the properties of the stimuli-responsive openable nonwoven fabric according to this example, that is, the property of opening in response to an alkaline aqueous solution is not impaired, and the ionicity is not impaired. It is also possible to blend fibers that do not contain singly or in combination. Examples of such nonionic fibers include vegetable cellulose fibers such as wood pulp, cotton fibers, hemp fibers, jute, cannabis fibers and cotton linters, plant fibers such as wool and silk, Examples thereof include regenerated cellulose fibers such as viscose rayon and copper ammonium rayon, and synthetic fibers such as polyolefin fibers, polyester fibers, polyamide fibers, and acrylic fibers.

The compounding quantity of the fiber which does not have such a cationic group and an anionic group is 0-50 weight part normally with respect to 100 weight part of nonwoven fabrics obtained, Preferably it is 0-20 weight part.
The stimulus-responsive openable nonwoven fabric according to this example is prepared by separately producing the above-described fibers having a cationic group and fibers having an anionic group, and the fibers having these cationic groups and an anionic property. The base-containing fibers are weighed and introduced into an aqueous medium to be dispersed. Further, if necessary, a fiber having no ionic group is dispersed in an aqueous medium. The total content of the fibers in the aqueous medium at this time is usually set in the range of 0.01 to 1% by weight, preferably 0.01 to 0.1% by weight.

  The stimulus-responsive openable nonwoven fabric according to this example does not require the use of a binder because the fiber itself has self-bonding properties. However, a normal aqueous binder is used in an aqueous medium in which the fiber is dispersed. Can also be added. When using such a binder, the content of these binders in the second stimulus-responsive openable nonwoven fabric is usually in the range of 0 to 20% by weight, preferably 0 to 10% by weight. Blended.

  Water is generally used as an aqueous medium in which a fiber having a cationic group, a resin fiber having an anionic group, and, if necessary, an aqueous binder is dispersed when producing the stimulus-responsive openable nonwoven fabric according to this example. However, lower alcohols such as methanol, ethanol, and isopropanol, and cell solve solvents such as ethyl cell solve can be used in combination with water.

The concentration of the fibers blended in such an aqueous medium in the aqueous medium is usually 0.01.
It is adjusted in the range of ˜1% by weight, preferably 0.01 to 0.1% by weight. Further, the concentration of the alkali-responsive binder and / or aqueous binder to be blended in the aqueous medium as necessary is usually adjusted within the range of 0 to 0.05% by weight, preferably 0 to 0.01% by weight. . And the compounding weight ratio of the fiber which has a cationic group and the fiber which has an anionic group disperse | distributed in this aqueous medium is usually in the range of 1: 9-9: 1, Preferably it is 1: 9-6. : The blending amount of each fiber is set so as to be within the range of 4.

Examples of the aqueous binder that may be used in the present invention include CMC-Na, starch, polyvinyl alcohol, and polyvinyl acetate.
This aqueous dispersion is usually adjusted to have a pH value of 2 to 8, preferably 2 to 4. That is, by making the aqueous dispersion slightly acidic, the fiber having a cationic group and the fiber having an anionic group are ionically combined, and the nonwoven fabric is stable in the acidic region and the neutral region. . Therefore, by setting the pH value of the aqueous dispersion to the acidic region in this way, it is possible to obtain a nonwoven fabric that is stable as a whole by ionically combining polar groups of the fibers. For adjusting the pH value of the aqueous dispersion, a method of adjusting the blending amount of a fiber having a cationic group and a fiber having an anionic group, and a method using hydrochloric acid, nitric acid, sulfuric acid or the like can be employed. .

Using the aqueous dispersion as described above, the stimulus-responsive openable nonwoven fabric of the present invention can be produced by making paper according to a normal method and drying. Further, the cationic fiber and the anionic fiber are shaped by a dry method by a usual method. This is entangled using a high-pressure water jet. Alternatively, the stimulus-responsive openable nonwoven fabric can be prepared by spraying water on fibers that have been mechanically shaped and entangled, or by immersing the fibers in water and then drying. The basis weight of the second stimulus-responsive openable nonwoven fabric obtained by paper making in this way is usually 10 to 60 g / m ^2.
, Preferably 15 to 30 g / m ² . Moreover, when making paper, it paper-works so that the average thickness after drying of this 2nd stimulus response openable nonwoven fabric may be in the range of 100-800 micrometers normally, Preferably it is 200-500 micrometers.

  The stimulus-responsive openable nonwoven fabric having such a basis weight and thickness exhibits good water absorption. In the stimulus-responsive openable nonwoven fabric according to this example obtained in this way, a large number of fibers are bonded to each other by the bonding force of the fibers themselves to form a stable nonwoven fabric in the acidic region and the neutral region. However, the stimulus-responsive openable nonwoven fabric loses ionic bonds that have acted between the fibers in an alkaline atmosphere, and is opened to become fibers and dispersed by contact with an alkaline solution.

  In the stimulus-responsive openable nonwoven fabric according to this example, polar groups in the fiber having a cationic group and the fiber having an anionic group are ionically bonded (that is, the bipolar group is neutralized). In the acidic region and the neutral region, the fibers are bonded to each other, so that the fibers are difficult to open. However, in an alkaline atmosphere, particularly in an alkaline atmosphere having a pH value of 8 or more, ions formed between the fibers As a result, the fiber cannot be maintained and the fiber is opened and dispersed in water.

Next, the processing method of the stimulus-responsive spreadable nonwoven fabric of the present invention will be described.
In the above-described stimulus-responsive openable nonwoven fabric, the fibers themselves constituting the nonwoven fabric have a cationic group and an anionic group. As described above, the fiber having a cationic group and the resin having an anionic group are ionically bonded to each other in the acidic region and the neutral region to constitute a stable nonwoven fabric.

  The treatment method of the stimulus-responsive spreadable nonwoven fabric of the present invention is such that the stimulus-responsive spreadable nonwoven fabric as described above is stable and not opened in the acidic region and neutral region, and in an alkaline atmosphere, the fiber binding force is This is a method in which the nonwoven fabric after use is dipped in an alkaline solution and opened using the loss. That is, the stimulus-responsive openable nonwoven fabric according to the present invention does not dissociate ionically bonded composite fibers in an acidic atmosphere and a neutral atmosphere as described above, and the stimulus-response opening is not performed in an acidic atmosphere or a neutral atmosphere. A fine nonwoven fabric does not open or collapse.

  In addition, although the stimulus-responsive spreadable nonwoven fabric does not basically contain the special binder as described above, the fiber itself has alkali-responsive spreadability. Although it is stable in the neutral region, when it is placed in the alkaline region, the ionic bonding force acting between the fibers is lost, and the fibers are opened to form a fiber and dispersed in an alkaline aqueous medium.

  That is, this stimulus-responsive openable nonwoven fabric does not respond to the stimuli of the acidic atmosphere and neutral atmosphere in the environment in which it is placed, but selectively senses the alkaline atmosphere and responds to this alkaline stimulus. In response, the fibers are opened, and the fibers can be dispersed in the aqueous medium.

Body fluids, human secretions or human excreta are usually weakly acidic, and generally their pH value is 4.
It is in the range of 7 to 7.8. Therefore, even if the first and second stimulus-responsive spreadable nonwoven fabrics of the present invention are used for sanitary products such as wiping cloths, paper, sanitary products, disposable diapers and urine pads, The non-stimulated open nonwoven fabric does not open and collapse.

  On the other hand, when the stimuli-responsive spreadable nonwoven fabric is placed in an alkaline atmosphere, it senses this alkaline atmosphere and opens the fiber to a state dispersible in water. That is, the stimulus-responsive spreadable nonwoven fabric in the present invention does not open at acidic regions and neutral regions, specifically when the pH value is less than 8, whereas the pH value is 8 or more, preferably 9 or more. Then, since the fibers are opened to individual fibers, if the water tank of the flush toilet is made alkaline in advance, the tube of the flush toilet will not be clogged even if it is poured into the flush toilet.

  Therefore, sanitary goods that have been conventionally treated as general waste can be easily opened at home and run into sewage for treatment. In addition, although the stimulus response opening nonwoven fabric shown in the Example mentioned above is very stable in the acidic region as described above, the neutral region is less stable than the acidic region and is not normally opened. In the neutral region where certain ions are dissolved, the stimulus-responsive openable nonwoven fabric may open. For example, in an aqueous medium in which monosodium hydrogen phosphate, disodium hydrogen phosphate, sodium hydroxide, sodium borate, etc. are dissolved and the pH value is in a neutral range (eg, pH 6.96), the cation used Depending on the type of the conductive fiber and the anionic fiber, the fiber may be opened. However, even such a stimulus-responsive spread nonwoven fabric does not open in the acidic region, but opens quickly in the alkaline region.

The stimulus-responsive spreadable nonwoven fabric as shown in the above-described embodiments senses alkalinity and opens in response thereto, but is stable in the acidic region and neutral region and does not open.
That is, secretions, excretions, etc. from the human body are weakly acidic, and in the state where the stimulus-responsive opening nonwoven fabric of the present invention is used, the fibers are firmly bonded, and the opening / disintegration is not However, when the product is once used and discarded, it is quickly opened by contacting with an alkaline aqueous solution and dispersed in a fiber state in the alkaline aqueous solution. Since the fiber dispersion solution can be processed by flowing it into a flush toilet, the sanitary ware that has not been dissolved in water and cannot be treated with the flush toilet and was disposed of as general waste has been opened at home. And can be processed.

Claims (1)

_{^{-N + R 1 3 · Cl -}} ,

A number of fibers having at least one kind of cationic group selected from the group consisting of (wherein R ¹ is each independently a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms), and —COO _{^{- · H +, -SO 3 -}} · H +, -SO 4 - containing a large number of fibers having a · H ⁺ become more selected from the group at least one anionic group ^- · H ⁺ and -PO ₄ A method for treating a stimulus-responsive spreadable nonwoven fabric, comprising: opening a stimulus-responsive spreadable nonwoven fabric by immersing it in an aqueous medium having a pH value of 8 or more.