KR102503850B1 - Method for seperating and treating superabsorbent polymer from absorbent sanitary products - Google Patents

Abstract

The present invention relates to a method for recovering a reusable superabsorbent polymer from a sanitary absorbent product. According to the present invention, there is provided a method for effectively recovering a super absorbent polymer having an excellent absorbency suitable for use in various applications including agriculture and horticulture from sanitary absorbent products containing the super absorbent polymer.

Description

Method for recovering reusable superabsorbent polymer from sanitary absorbent products {METHOD FOR SEPERATING AND TREATING SUPERABSORBENT POLYMER FROM ABSORBENT SANITARY PRODUCTS}

The present invention relates to a method for recovering a reusable superabsorbent polymer from a sanitary absorbent product.

Super absorbent polymer (SAP) is a synthetic polymer material that can absorb about 500 to 1,000 times its own weight in moisture, and is also called SAM (super absorbency material), AGM (absorbent gel material), etc. there is.

Superabsorbent polymers began to be put into practical use as sanitary tools, and are now widely used in various fields such as sanitary products such as diapers for babies, soil retaining agents for gardening, waterstop materials for civil engineering, sheets for raising seedlings, and freshness retainers in the field of food distribution. .

For example, the amount of disposable diapers used increases every year, and about 200 billion or more are produced and used annually. Most of the used diapers end up in landfills, which is equivalent to about 30 million tons per year in terms of weight. It is known to account for about 2% of total municipal waste.

Accordingly, research into a regeneration method that can separate and recycle hygienic absorbent products such as disposable diapers by material such as nonwoven fabric, film, pulp, and superabsorbent polymer is continuously being conducted.

Conventionally, the main purpose was to separate and recycle nonwoven fabric and pulp from sanitary absorbent products, and in the process, a large amount of divalent or higher metal salt was used.

However, since the divalent or higher metal salt forms additional cross-links near the surface of the super absorbent polymer and significantly reduces the absorbency, the reusable use of the super absorbent polymer recovered through the regeneration method is limited.

An object of the present invention is to provide a method for recovering a super absorbent polymer having physical properties suitable for reuse for various purposes from a sanitary absorbent product containing the super absorbent polymer.

According to the present invention,

(1) cutting the sanitary absorbent product so that the absorbent layer containing the superabsorbent polymer is exposed;

(2) mixing a salt solution with the cut sanitary absorbent product obtained in step (1);

(3) separating the superabsorbent polymer from the mixture obtained in step (2);

(4) drying the superabsorbent polymer obtained in step (3), and

(5) Grinding the superabsorbent polymer obtained in step (4)

A method for recovering a reusable superabsorbent polymer from a sanitary absorbent product is provided.

Hereinafter, a method for recovering a reusable superabsorbent polymer from a sanitary absorbent product according to an embodiment of the present invention will be described in more detail.

The terminology used herein is only intended to refer to specific embodiments and is not intended to limit the present invention. And, as used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite.

As used herein, the meaning of 'comprising' or 'including' specifies a specific characteristic, region, integer, step, operation, element, or component, and of another specific characteristic, region, integer, step, operation, element, or component. Additions are not excluded.

The term 'superabsorbent polymer' used in the present invention refers to a base resin powder containing a first crosslinked polymer of water-soluble ethylenically unsaturated monomers having an acidic group at least partially neutralized; and a surface crosslinking layer formed on the base resin powder and including a second crosslinked polymer in which the first crosslinked polymer is additionally crosslinked with a surface crosslinking agent.

On the other hand, as a result of continuous research by the present inventors, it was confirmed that a super absorbent polymer having excellent absorbency at a level suitable for use for various purposes including agricultural and horticultural use can be recovered through a series of processes as follows.

According to one embodiment of the invention,

(1) cutting the sanitary absorbent product so that the absorbent layer containing the superabsorbent polymer is exposed;

(2) mixing a salt solution with the cut sanitary absorbent product obtained in step (1);

(3) separating the superabsorbent polymer from the mixture obtained in step (2);

(4) drying the superabsorbent polymer obtained in step (3), and

(5) Grinding the superabsorbent polymer obtained in step (4)

A method for recovering a reusable superabsorbent polymer from a sanitary absorbent product is provided.

According to one embodiment of the present invention, in particular, through the step (5) of grinding the superabsorbent polymer obtained in the step (4), the degree of permeation of the salt solution in the step (3) is weak, and thus crosslinking is relatively small. This part can be exposed to the outside. Through such pulverization, it is possible to recover the inherent absorbency of the superabsorbent polymer recovered from the sanitary absorbent product. Accordingly, the recovery method of the present invention can provide a superabsorbent polymer having excellent absorbency at a level suitable for use in various applications including agriculture and horticulture.

Hereinafter, each step that may be included in the method of recovering the reusable superabsorbent polymer from the sanitary absorbent product will be described.

(1) Cutting

*The absorbent hygiene products include, but are not limited to, disposable diapers for infants or adults, feminine hygiene products, bed pads, and other related absorbent and adsorbent products.

Generally, the sanitary absorbent product includes a liquid impermeable back sheet including a polyethylene film, a polypropylene film, and the like; an absorbent layer including a superabsorbent polymer and pulp surrounding the superabsorbent polymer; and a main body in which liquid-permeable non-woven sheets formed of polyethylene, polypropylene, rayon, or cotton are sequentially laminated. In addition, the sanitary absorbent product may further include an elastic body or an adhesive tape for adhering the main body to the wearer.

The above step (1) is a step of cutting a used or unused sanitary absorbent product (for example, a defect has occurred in the manufacturing process).

By the cutting, the absorbent layer containing the super absorbent polymer is exposed to the outside of the sanitary absorbent product.

A conventional shredder may be used to cut the sanitary absorbent product.

As a non-limiting example, the sanitary absorbent product may be cut into pieces having a longest diameter of about 10 cm in a mincer.

If necessary, prior to the cutting, a step of washing the sanitary absorbent product with water or an appropriate aqueous solution may be performed.

For example, the washing may be performed by adding the sanitary absorbent product to water, stirring it, and removing the water using a centrifugal drum or the like.

(2) mixing of salt solution

The step (2) is a step of mixing a salt solution with the sanitary absorbent product obtained in the step (1) where the absorbent layer is exposed.

According to an embodiment of the present invention, step (2) is performed for the purpose of pretreatment to effectively separate the superabsorbent polymer included in the sanitary absorbent product.

In step (2), the salt solution dehydrates the superabsorbent polymer at least partially gelled by use or washing to form a particulate superabsorbent polymer.

Dehydration using the salt solution is faster than air drying and uses less energy than thermal drying.

Step (2) is performed by adding a salt solution to the cut sanitary absorbent product obtained in step (1) and mixing by stirring.

As the salt solution, a solution containing a metal salt capable of dehydrating the gelled superabsorbent polymer may be used.

According to one embodiment, the salt solution may be a solution containing one or more compounds selected from the group consisting of alkali metal salts, alkaline earth metal salts and aluminum salts.

Specifically, the salt solution is sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, calcium chloride, calcium nitrate, calcium sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, disodium phosphate, barium chloride, trisodium phosphate, It may be a solution containing at least one compound selected from the group consisting of sodium silicate, potassium sulfide, aluminum sulfate, sodium bisulfate, zinc sulfate, aluminum chloride, and sodium sulfate.

According to an embodiment of the invention, it may be advantageous to perform the step (2) that the salt solution is an aqueous solution containing a salt at a concentration of 1 to 50%. Preferably, the salt solution may contain salt at a concentration of 1 to 50%, or 2 to 35%, or 5 to 25%.

In order to secure the dehydration efficiency of the superabsorbent polymer with the salt solution, the salt solution preferably contains salt at a concentration of 1% or more, 2% or more, or 5% or more.

However, if the concentration of the salt is too high, the surface of the super absorbent polymer is excessively cross-linked, and thus the absorbent properties of the super absorbent polymer may deteriorate. Therefore, it is preferred that the salt solution contains salt at a concentration of 50% or less, or 35% or less, or 25% or less.

According to an embodiment of the present invention, the salt solution preferably contains enough water not to saturate the superabsorbent polymer.

Specifically, the salt solution may be mixed in a weight ratio of 1 to 500 times with respect to the cut sanitary absorbent product obtained in step (1). Preferably, the salt solution may be mixed in a weight ratio of 1 to 200 times, 2 to 100 times, or 5 to 50 times the weight of the cut sanitary absorbent product obtained in step (1).

In order to secure the separation efficiency of the super absorbent polymer by the added salt solution, the salt solution has a weight of at least 1, 2, or 5 times the weight of the cut sanitary absorbent product obtained in step (1). It is preferable to mix in ratio. If the added amount of the salt solution is too small, most of the added salt solution is absorbed into pulp or nonwoven fabric included in the sanitary absorbent product, making it difficult to separate the superabsorbent polymer.

However, if the salt solution is mixed too much, the process efficiency of the step (2) may decrease, such as saturation of the superabsorbent polymer by the water contained in the salt solution. Therefore, the salt solution is preferably mixed in a weight ratio of 500 times or less, or 200 times or less, or 100 times or less, or 50 times or less with respect to the cut sanitary absorbent product obtained in step (1).

From the point of contact of the salt solution with the cut sanitary absorbent product, the expanded superabsorbent polymer is contracted, and the solution inside the superabsorbent polymer escapes to the outside. Therefore, step (2) may be performed until the superabsorbent polymer is sufficiently dehydrated by the salt solution.

Preferably, the salt solution may be mixed with the cut sanitary absorbent product obtained in step (1) with a contact time of 1 to 600 minutes or 10 to 600 minutes.

However, if the contact time is too long, the time of the entire process is prolonged, and the absorption capacity of the recycled absorbent polymer may be reduced due to excessive reaction. Therefore, in the step (2), it is preferable to appropriately adjust the contact time in consideration of the concentration of the salt solution and the throughput of the cut sanitary absorbent product.

Through the step (2), the superabsorbent polymer may be obtained in the form of particles having a particle size of 0.1 to 5 mm.

(3) Separation of superabsorbent polymer

The step (3) is a step of separating the superabsorbent polymer from the mixture obtained in the step (2).

The mixture obtained in step (2) includes a plastic component (eg, a polyethylene film or a polypropylene film), a fiber component, and a particulate superabsorbent polymer.

The step (3) may be performed by a conventional method for selectively separating the particulate superabsorbent polymer from the mixture.

For example, in the step (3), a sieve or wire mesh having an opening that allows the particulate superabsorbent polymer to pass through may be used. In order to increase the separation efficiency, a device for pressing the upper part of the sieve on which the mixture is accumulated may be used together. In the step (3), a plurality of sieves having the same or different openings or open areas may be used.

(4) Drying of superabsorbent polymer

Step (4) is a step of drying the superabsorbent polymer obtained in step (3).

Step (4) is a step of drying the particulate superabsorbent polymer obtained in step (3) by heat. In order to increase the efficiency of the drying, the drying may proceed after a dehydration process using a centrifuge or the like.

Specifically, the drying may be performed at a temperature of 100 to 250 °C, or 120 to 250 °C, or 120 to 200 °C, or 120 to 150 °C. The temperature may be defined as the temperature of the drying medium supplied for drying or the temperature inside the dryer used in step (4).

If the drying temperature is too low, the drying time may be increased and thus the treatment time of the entire process may be increased. Therefore, the drying is preferably performed at a temperature of 100 °C or higher.

However, if the drying temperature is too high, the surface of the super absorbent polymer may be excessively dried, resulting in an increased amount of fine powder generated in a subsequent pulverization process and deterioration in the absorption properties of the super absorbent polymer. Therefore, the drying is preferably performed at a temperature of 250 °C or less.

Conventional devices such as a hot air dryer, a rotary dryer, an infrared dryer, and a dryer using microwaves may be used for the drying.

In the step (4), the drying time may be adjusted according to the temperature.

Preferably, the drying may be performed for 10 minutes to 600 minutes, or 30 minutes to 400 minutes, or 60 minutes to 300 minutes under the above temperature range.

(5) pulverization of superabsorbent polymer

The step (5) is a step of grinding the superabsorbent polymer obtained in the step (4).

As described above, the salt solution mixed in step (2) makes the superabsorbent polymer included in the sanitary absorbent product in a state in which it can be effectively separated from other components. However, the absorbency of the superabsorbent polymer contained in the sanitary absorbent product is significantly reduced by the salt solution. That is, the salt solution causes shrinkage or surface cross-linking of the super absorbent polymer, and as a result, the absorbency of the recovered super absorbent polymer decreases.

According to an embodiment of the present invention, by crushing the super absorbent polymer obtained in step (4), the inner portion of the super absorbent polymer (that is, the portion having a relatively low degree of crosslinking) not in contact with the salt solution in step (2) is removed. can be exposed to the outside.

Through such pulverization, it is possible to recover the inherent absorbency of the superabsorbent polymer recovered from the sanitary absorbent product.

In the step (5), a conventional crushing means may be used.

For example, the grinding means includes a pin mill, a hammer mill, a screw mill, a roll mill, a fitz mill, and a disc mill. , a jog mill, or the like may be used.

The pulverization of step (5) may be performed to the extent that the inner portion of the superabsorbent polymer not in contact with the salt solution in step (2) can be exposed to the outside.

Therefore, the particle diameter of the superabsorbent polymer obtained through the pulverization is not particularly limited.

However, in order for the super absorbent polymer obtained through step (5) to exhibit excellent absorbent properties, the grinding may be performed so that the average particle diameter of the super absorbent polymer is 100 to 1000 μm.

And, if necessary, a step of selectively classifying the particles having a particle diameter within the above range may be further performed after the pulverization of step (5).

According to the present invention, there is provided a method for effectively recovering a super absorbent polymer having an excellent absorbency suitable for use in various applications including agriculture and horticulture from sanitary absorbent products containing the super absorbent polymer.

Hereinafter, preferred embodiments are presented to aid understanding of the invention. However, the following examples are only for exemplifying the present invention, and do not limit the present invention only to these.

Example 1

(1) A used disposable diaper containing a superabsorbent polymer was put into a small cutting machine (GRANDBELL Co.) in the width direction and cut into pieces having a width of 2 cm.

(2) 250 g of the cut disposable diaper obtained in step (1) and 5000 ml of 5% aluminum sulfate aqueous solution were added to a 10 L plastic container and mixed.

(3) The mixture obtained in step (2) was poured into a standard sieve with a diameter of 203 mm and an opening of 19 mm, and a mixture including a back sheet, nonwoven fabric, and superabsorbent polymer was first separated. The mixture obtained in the first separation was poured into a standard opening 4 mm sieve, and a mixture including pulp, nonwoven fabric cut into small sizes, and the superabsorbent polymer was secondarily separated. The mixture obtained by the secondary separation was placed in a 400 mesh nylon bag and dehydrated in a dehydrator for 3 minutes to obtain 65 g of superabsorbent polymer.

(4) The super absorbent polymer obtained in step (3) is evenly spread in a rectangular SUS container equipped with a 0.1 mm opening wire mesh on the bottom, and dried at 120 ° C. for 6 hours to obtain a 0.1 to 3 mm thickness. A superabsorbent polymer having a particle size of

(5) The super absorbent polymer obtained in step (4) was placed in a two-stage roll mill grinder (Modern Process Equipment Co.) and pulverized to obtain a super absorbent polymer having an average particle diameter of 300 μm.

Example 2

Average particle diameter of 250 μm in the same manner as in Example 1, except that 5000 ml of 2% calcium chloride aqueous solution was used instead of 5000 ml of 5% aluminum sulfate aqueous solution as the salt solution, and a fitz mill grinder was used instead of a roll mill grinder as the grinder. A superabsorbent polymer was obtained.

Example 3

A superabsorbent polymer having an average particle diameter of 300 μm was obtained in the same manner as in Example 1, except that 5000 ml of a 5% aqueous solution of calcium chloride was used as the salt solution instead of 5000 ml of an aqueous solution of 5% aluminum sulfate.

Comparative Example 1

A superabsorbent polymer having an average particle diameter of 950 μm was obtained in the same manner as in Example 1, except that the grinding step (5) was not performed.

Comparative Example 2

A superabsorbent polymer having an average particle diameter of 1050 μm was obtained in the same manner as in Example 3, except that the grinding step (5) was not performed.

*

test example

After putting 1.00 g (W ₀ ) of the superabsorbent polymer obtained in Examples and Comparative Examples in a nonwoven bag and sealing it, it was submerged in a container containing distilled water at room temperature. After 60 minutes, the bag was taken out, hung for 10 minutes to remove moisture, and then the mass W ₂ (g) of the bag was measured. Separately, the bag without the superabsorbent polymer was immersed in the same manner as above, and after draining water, the mass W ₁ (g) was measured. For each obtained mass, the distilled water absorption amount (g/g) of the superabsorbent polymer was calculated according to the following formula.

* Distilled water absorption (g/g) = (W ₂ - W ₁ ) / W ₀

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Distilled water absorption (g/g) 75 112 96 35 43

Referring to Table 1, it was confirmed that the super absorbent polymers according to the above examples had significantly higher absorption than the super absorbent polymers according to the comparative examples.

Claims (8)

(1) cutting the sanitary absorbent product so that the absorbent layer containing the superabsorbent polymer is exposed;
(2) mixing a salt solution with the cut sanitary absorbent product obtained in step (1);
(3) separating the superabsorbent polymer from the mixture obtained in step (2);
(4) drying the superabsorbent polymer obtained in step (3), and
(5) Grinding the superabsorbent polymer obtained in step (4)
A method for recovering a reusable superabsorbent polymer from a sanitary absorbent product comprising:
According to claim 1,
Wherein the salt solution is a solution containing at least one compound selected from the group consisting of alkali metal salts, alkaline earth metal salts, and aluminum salts, a method for recovering a reusable superabsorbent polymer from a sanitary absorbent product.
According to claim 1,
The salt solution is sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, calcium chloride, calcium nitrate, calcium sulfate, magnesium chloride, magnesium nitrate, magnesium sulfate, disodium phosphate, barium chloride, trisodium phosphate, sodium silicate, A method for recovering a reusable superabsorbent polymer from a sanitary absorbent product, the solution containing at least one compound selected from the group consisting of potassium sulfide, aluminum sulfate, sodium bisulfate, zinc sulfate, aluminum chloride, and sodium sulfate.
According to claim 1,
The method of claim 1 , wherein the salt solution is an aqueous solution containing salt at a concentration of 1 to 50%.
According to claim 1,
The method of claim 1, wherein the salt solution is mixed in a weight ratio of 1 to 500 times the weight of the cut sanitary absorbent product obtained in step (1).
According to claim 1,
The salt solution is mixed with the cut sanitary absorbent product obtained in step (1) with a contact time of 1 to 600 minutes.
According to claim 1,
The method of recovering a reusable superabsorbent polymer from a sanitary absorbent product, wherein the drying in step (4) is performed at a temperature of 100 to 250 ° C. for 10 to 600 minutes.
According to claim 1,
The method of recovering the reusable super absorbent polymer from the sanitary absorbent product, wherein the grinding in step (5) is performed so that the super absorbent polymer has an average particle diameter of 100 to 1000 μm.