KR20160108688A

KR20160108688A - A method for producion of the layered double hydroxides by irradiation

Info

Publication number: KR20160108688A
Application number: KR1020150030813A
Authority: KR
Inventors: 박종석; 임윤묵; 노영창; 정성린; 권희정
Original assignee: 한국원자력연구원
Priority date: 2015-03-05
Filing date: 2015-03-05
Publication date: 2016-09-20

Abstract

The present invention relates to a method for producing a water-soluble polymer, which comprises adding a basic solution to an aqueous solution containing a divalent metal salt and a trivalent metal salt, followed by stirring (step 1); And irradiating the aqueous solution of step 1 with 20 to 100 kGy of radiation (step 2). The present invention also provides a method for producing a layered double hydroxides (LDH). The double layer hydroxide (LDH) and polymer / double layer hydroxide composites prepared according to the present invention can improve the flame retardancy and thermal / mechanical properties of the polymer material, as well as being capable of being ion-exchanged to provide a catalyst, a heat stabilizer, And can be used in various industrial fields such as a membrane.

Description

Technical Field [0001] The present invention relates to a method for producing double layer hydroxides using radiation,

The present invention relates to a process for preparing double layer hydroxides using radiation.

Recently, polymer nanocomposites prepared by adding nanoparticles to polymers have been proved to have improved mechanical properties, heat resistance, flame retardancy, mechanical properties and flame retardancy. The nanoparticles used in polymers include carbon nanotubes (CNT), layered double hydroxides or hydrotalcites (LDH), and HDS (hydroxy double salts). In order to increase the dispersibility of nanoparticles in polymer matrix, Or a method of using a dispersant additive is mainly used.

Layered double hydroxides (LDH) are known to be similar hydrotalcite-like materials with a layered structure and consist of metal divalent cations and trivalent cation layers, respectively. This metal ion forms an octagonal-shaped sheet of charged cation with an end-OH group attached to it. Due to its high charge density, water and anions are inserted to form a layer for balance. The inserted anions can be exchanged and used in various industrial fields such as catalysts, heat stabilizers, drugs, and inorganic membranes.

In addition, since the double layer hydroxide is composed of a layered structure having relatively weak bonds, metal or various organic modifications can be formed in the intermediate layer, and thus it can be used in various fields.

Recently, dual-layer hydroxides have been widely used as nanoparticles in polymeric materials. Complexes formed by the synthesis of polymers and LDHs can improve the thermal stability, flame retardancy, and mechanical properties of polymers, And also as a pharmaceutical transferring material. The composite can also be used as a flame retardant due to good thermal stability and interlayer hydration.

The chemical formula of LDH is a ^{_{[M 2 + (1-x}} ) M 3 + x (OH) 2] x + [A m -] x / m and a nH ₂ O, in the formula M ² ^+, M ^3+, respectively 2 Or trivalent cations such as Mg ² ⁺ , Al ³ ⁺ and the like, and A ^m ^- has an anion such as CO ₃ ^2- , SO ₄ ^2- , NO ₃ ^- and the like.

In addition, a strong electrical attraction between the LDH layers causes narrow interlayer distance, and it is difficult to insert the polymer because of low affinity with the nonpolar polymer. Therefore, the anion present in the LDH layer is converted into the long organic chain To facilitate the insertion of the polymer by increasing the interval between the layers.

It is not easy to prepare the exfoliated polymer / LDH nanocomposite. Mg-Al LDH treated with dodecyl sulfate (DS) can increase compatibility with hydrophobic polymer.

Particularly, compared with the phenomenon of decrease in mechanical properties of polymeric materials due to the addition of flame retardants, improvement of mechanical properties due to intercalation or exfoliation of layered polymeric compounds, separation of hydrates due to layer structure destruction, Flame retardancy can also be increased. However, since LDH has a strong hydrophilicity, it has a disadvantage that it has poor compatibility with hydrophobic polymer. Therefore, organizing process is required to increase compatibility with hydrophobic polymer.

In this connection, Korean Patent Laid-Open No. 10-2011-0045282 discloses a nanocomposite polymer electrolyte in which a nanocomposite of a double hydroxide having a layered structure is added to a polyethylene glycol diacrylate (PEDGA) polymer matrix. The PEDGA By using the nanocomposites of polymers and LDHs as the electrolyte of the dye-sensitized solar cell, unlike conventional electrolytes, it is possible to secure the process efficiency while maintaining and improving the physical properties such as high ionic conductivity and higher elastic modulus, .

Korean Patent Laid-Open Publication No. 10-2011-0045282 also provides a layered metal double layer hydroxide (LDH) variant sephiocyte compound with improved thermal properties and a method of preparing the same. Specifically, the layered metal double layer hydroxide Preparing a partially dehydrated and oxidized layered metal double layer hydroxide by heat treatment at 265 to 275 占 폚; And a step of hydration-reacting the partially dehydrated layered metal double layer hydroxide to prepare a sepiolite compound having a channel structure.

However, although the hydrothermal synthesis method is mainly used for the production of the LDH, the organic lignin is required to undergo organizing after stirring for a long time at a high temperature.

Accordingly, in the present invention, while studying the production of LDH, a method of synthesizing and organizing LDH by irradiation alone was developed, and a composite material of LDH and polymer improved in flame retardancy, thermal and mechanical properties of the polymer material was developed Thus completing the present invention.

It is an object of the present invention to provide a process for preparing a double layer hydroxide using radiation.

In order to achieve the above object,

Adding a basic solution to an aqueous solution containing a divalent metal salt and a trivalent metal salt, followed by stirring (step 1); And

And irradiating the aqueous solution of step 1 with 20 to 100 kGy of radiation (step 2). The present invention also provides a method for producing double layer hydroxides (LDH).

Further, according to the present invention,

A double layer hydroxide prepared by the above process is provided.

Further,

A polymer / double layer hydroxide composite comprising the double layer hydroxide in a polymer matrix resin is provided.

The double layer hydroxide (LDH) and polymer / double layer hydroxide composites prepared according to the present invention can improve the flame retardance and thermal / mechanical properties of the polymer material, and can be ion-exchanged and used as catalysts, heat stabilizers, drugs, Film and the like can be used in various industrial fields.

1 is a graph showing the results of infrared spectroscopy (FT-IR) of the LDH prepared in Example 2 and Comparative Example 1;
2 is a graph showing the results of X-ray diffraction analysis using the LDHs prepared in Examples 1 to 3 and Comparative Example 1;
3 is a graph showing the measurement results of the oxygen limit index (LOI) of the HDPE / LDH composite material prepared in Examples 4 to 7 and the pure HDPE prepared in Comparative Example 2;
FIG. 4 is a graph showing tensile strengths measured by an univariate testing machine (UTM) using the HDPE / LDH composite prepared in Examples 4 to 6 and the pure HDPE prepared in Comparative Example 2 ;
5 is a graph showing the results of a dynamic mechanical analyzer (DMA) of the HDPE / LDH composite material prepared in Example 4 and the pure HDPE prepared in Comparative Example 2. FIG.

Hereinafter, the present invention will be described in detail.

According to the present invention,

LDH organizing is essential for the preparation of polymers as nanocomposites. The hydroxide layer of all LDHs is negatively charged and therefore generally contains a negative charge. The main purpose of modifying LDH into organic LDH is to widen the interlayer spacing of LDH to facilitate the insertion of large substances such as polymer chains. Organic anionic surfactants with anionic end groups in long chain hydrophobic groups are the most suitable materials for the LDH modification process. Due to the hydrophobic nature of the surfactant, it significantly reduces the surface energy compared to the pre-reforming LDH.

The organic modification method of the LDH uses a method of intercalating organic anions into the interlayer. Methods for intercalating organic anions into LDH include coprecipitation, ion-exchange, calcination method are generally used.

However, the conventional method of producing LDH has a disadvantage in that it requires additional organic treatment after a long stirring reaction at a high temperature. Accordingly, the present invention has developed a method for producing LDH by a 1-step process capable of synthesizing and organizing LDH only by irradiation with radiation at room temperature.

In the method for producing a double layer hydroxide according to the present invention, step 1 is a step of adding a basic solution to an aqueous solution containing a divalent metal salt and a trivalent metal salt, followed by stirring.

Generally, LDH is a layered crystal composed of hydroxides of two metals and is represented by the following formula (1).

&Lt; Formula 1 >

^{_{[M 2 + (1-x}} ) M 3 + x (OH) 2] x + [A m -] x / m and nH ₂ O

M ² ⁺ is a divalent cation such as Mg ² ⁺ , Ni ² ⁺ , Cu ² ⁺ , Zn ² ⁺ , Ca ² ⁺ and Co ² ⁺ , and M ³ ⁺ is Al ³ ⁺ , Cr ³ A trivalent cation such as ⁺ , Fe ³ ⁺ , Ga ³ ⁺ , In ³ ⁺ , V ³ ⁺ and Ti ³ ⁺ can be used, and A ^m ^- can be CO ₃ ² ^- , SO ₄ ² ^- , NO ₃ ^- ClO ₄ ^- , Br ^- and the like can be used. X is a number from 0 to 1, and n is a positive number exceeding zero.

In the step 1, an aqueous solution can be prepared by dissolving the divalent metal salt and the trivalent metal salt in distilled water to prepare an LDH. The bivalent metal salt may include metals such as magnesium, nickel, copper, zinc, calcium and cobalt, and the trivalent metal salt may include metals such as aluminum, chromium, iron, gallium, indium, vanadium and titanium.

After dissolving the metal salt sufficiently, it can be added dropwise while maintaining a pH of 10 ± 2 using a basic solution. At this time, a nucleation reaction occurs.

In addition, in step 1, the surface of the LDH can be modified by adding a surfactant. LDH particles are intercalated between polymer chains in a polymer composite made of a mixture of polymer and LDH, so that the flame retardancy, thermal stability and mechanical properties of the polymer composite can be improved.

However, LDH particles are not hydrophilic and are incompatible with hydrophobic polymers such as polyethylene (PE), polypropylene (PP) and polystyrene (PS), and tend to have a tendency to decrease the mechanical and thermal properties of the polymer . Therefore, if the surface of the LDH surface is modified with a material such as SDBS, which is an organic surfactant, the compatibility with the hydrophobic polymer is increased, and the thermal and mechanical properties of the polymer composite material can be improved. The surfactant may be, but not limited to, sodium dodecyl benzene sulfonate (SDBS), dodecyl sulfate (DS), and dodecyl benznesulfonate (DBS).

Further, in the method for producing a double layer hydroxide according to the present invention, step 2 is a step of irradiating the aqueous solution of step 1 with 20 to 100 kGy of radiation.

The radiation can be irradiated at room temperature. If the dose of radiation is 20 kGy, the LDH is not synthesized. If the dose is more than 100 kGy, there is a problem that the irradiation of radiation does not improve the physical properties.

The radiation may be irradiated with an X-ray, a gamma ray, an alpha ray, a beta ray, an electron ray, a proton ray, an intermediate proton ray, a heavy ion ray or a neutron ray.

In addition, by irradiating the aqueous solution prepared in the step 1 with the radiation, the conventional hydrothermal synthesis method reacted for a long time at a temperature of 75 DEG C for 18 hours or more to synthesize LDH. However, when irradiated with radiation as in the present invention, The synthesis can be completed within 10 minutes by only stirring for 1 hour under the temperature condition of < RTI ID = 0.0 >

In addition,

A double layer hydroxide prepared by the above process is provided.

The double layer hydroxide prepared by the process of the present invention is represented by the following formula (1).

&Lt; Formula 1 >

^{_{[M 2 + (1-x}} ) M 3 + x (OH) 2] x + [A m -] x / m and nH ₂ O

In this case, in Formula 1, M ² ⁺ is ^{Mg 2 +, Ni 2 +,} Cu 2 +, Zn 2 +, Ca 2 + cations and one member selected from the group consisting of Co ² ⁺ a;

The M ³ ⁺ ³ ⁺ is Al, Cr ⁺ ^3, Fe ⁺ ^3, Ga ⁺ ^3, In ⁺ ^3, V ⁺ ^3, and one kind cation selected from the group consisting of Ti ³ ⁺ a;

A shopping ^m ^- is _{^{_{^{CO 3 2 -, SO 4 2}}}} - and NO ₃ ^- one kind of anions selected from the group consisting of a;

X is a number from 0 to 1, and n is a positive number exceeding zero.

For example, Mg (NO ₃ ) ₂ 6H ₂ O, Al (NO ₃ ) ₃ 9H ₂ O and sodium dodecyl benzene sulfonate (SDBS) or MgCl ₂ 6H ₂ O, AlCl ₃ 9H ₂ O, And the organic LDH can be surface-modified by the surfactant to increase the compatibility with the hydrophobic polymer.

Further,

The LDH according to the present invention can be mixed with a polymer to prepare a polymer / LDH composite material, which can improve the flame retardancy, thermal stability and mechanical properties of the polymer composite by interposing LDH particles between the polymer chains.

However, LDH particles are not hydrophilic and are incompatible with hydrophobic polymers such as polyethylene (PE), polypropylene (PP) and polystyrene (PS), and tend to have a tendency to decrease the mechanical and thermal properties of the polymer . Therefore, if the surface of the LDH surface is modified with a material such as SDBS, which is an organic surfactant, the compatibility with the hydrophobic polymer is increased, and the thermal and mechanical properties of the polymer composite material can be improved.

In addition, the double layer hydroxide may be mixed in a weight ratio of 5 to 10 phr based on the polymer. If the content of the double-reactive hydroxides is less than 5 phr, the improvement of the flame retardancy and the thermal / mechanical properties of the composite can not be expected. If the content exceeds 10 phr, the compatibility between the polymer and the LDH is poor and the mechanical properties such as tensile strength are deteriorated have.

As an example, the polymer may be high density polyethylene (HDPE), which is a general hydrophobic polymer. The LDH modified with SDBS can be blended with HDPE and hot pressed to produce a polymer / LDG composite.

Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

Example 1 Preparation of Organically Modified LDH Using Radiation Technology.

Step 1: For the synthesis of Mg-Al-Cl LDH, magnesium chloride hexahydrate (MgCl ₂ .6H ₂ O) and aluminum chloride hexahydrate (AlCl ₃ .6H ₂ O) were used. Sodium dodecyl benzene sulfonate (SDBS) was used as a surfactant.

First, 250 ml of water was added to the tree-neck flask, and 0.2 mol of MgCl ₂ .6H ₂ O, 0.1 mol of AlCl ₃ .6H ₂ O and 0.015 mol of SDBS were added. At this time, stirring was carried out while maintaining the temperature at 75 캜. When the material was sufficiently dissolved, 1M of NaOH was added slowly while maintaining the pH of 10 to cause a nucleation reaction. Followed by heating and stirring for 1 hour.

Step 2: One hour later, 25 kGy was irradiated with an electron beam accelerator (ELV-8, EBtech) at a beam energy of 1 Mev, a beam current of 17.6 mA, and a dose rate of 25 kGy / 1 scan.

After the irradiation, it was washed with distilled water using a centrifuge, and the remaining residue was dried in a vacuum oven for over 24 hours.

&Lt; Example 2 >

Mg-Al-Cl LDH was produced in the same manner as in Example 1, except that the dose of electron beam irradiation in Example 2 was 50 kGy.

&Lt; Example 3 >

Mg-Al-Cl LDH was prepared in the same manner as in Example 1, except that the dose of electron beam irradiation in Example 2 was 75 kGy.

Example 4: Preparation of a polymer / double layer hydroxide composite.

High-density polyethylene (HDPE) was used as a polymer matrix resin to prepare a polymer / double-layer hydroxide composite material. In Example 2, Mg-Al-Cl LDH prepared by irradiating 50 kGy with electron beams was added to 5% by weight of high density polyethylene Respectively.

Brabender mixer of Brabender was used for the blending of the polymer resin and the powder. The mixing conditions were formulated at 170 ° C for 15 minutes at 60 rpm, and a polymer / double layer hydroxide composite was produced in the form of a sheet through a hot press at the same temperature.

Example 5 Preparation of Polymer / Double Layer Hydroxide Composite.

A polymer / double layer hydroxide composite material was prepared in the same manner as in Example 4, except that 10 phr of organically modified Mg-Al-Cl LDH was added in Example 4.

Example 6 Preparation of Polymer / Double Layer Hydroxide Composite.

A polymer / double layer hydroxide composite material was prepared in the same manner as in Example 4, except that 15 phr of organically modified Mg-Al-Cl LDH was added in Example 4.

Example 7 Preparation of Polymer / Double Layer Hydroxide Composite.

A polymer / double layer hydroxide composite material was prepared in the same manner as in Example 4, except that 20 phr of organically modified Mg-Al-Cl LDH was added in Example 4.

&Lt; Comparative Example 1 > Preparation of LDH by hydrothermal synthesis.

To prepare Mg-Al-Cl LDH by the conventional hydrothermal synthesis method, 250 ml of water was added to the tree-neck flask, and 0.2 mol MgCl ₂ .6H ₂ O and 0.1 mol AlCl ₃ .6H ₂ O were added. At this time, stirring was carried out while maintaining the temperature at 75 캜.

When the material was sufficiently dissolved, 1 M NaOH was slowly added while maintaining the pH of 10 to cause a fission reaction. Followed by heating and stirring for 18 hours.

After 18 hours, it was washed with distilled water using a centrifuge, and the remaining residue was dried in a vacuum oven for 24 hours or more to prepare LDH.

&Lt; Comparative Example 2 > Production of high density polyethylene.

High density polyethylene (HDPE) was used as a polymer matrix resin, and the HDPE was formed into a sheet form at 170 占 폚 using a hot press.

Experimental Example 1 Infrared spectroscopic analysis and X-ray diffraction analysis of LDH.

In order to examine the crystal structure of the LDH prepared in Example 2 and Comparative Example 1, infrared spectroscopy (FT-IR) was performed. The results are shown in FIG.

FT-IR measurements, even in the vicinity of wavelength 3400 ~ 3500 cm ^-1, as shown in Figure 1 showed an absorption band due to the stretching vibration of OH, 1630 cm ^- ¹ peak due to the OH-H bending vibrations were at.

In addition, 1380 cm ^- ¹ in the carbonate (carbonate) ions to the stretching vibration appeared due to, 800 cm ^-1 Under showed a peak due to lattice vibration between metal and oxygen, as in the modified SDBS Mg-Al-Cl LDH In Example 2, a peak due to CH stretching vibration due to SDBS was observed at 2,850 to 2,960 cm ^< ^{-1 >} , indicating that the LDH was organicized.

X-ray diffraction was performed using the LDH prepared in Comparative Example 1 and Examples 1 to 3 to confirm the crystal structure of the organically modified Mg-Al-Cl LDH according to the irradiation dose The results are shown in FIG. 2 and Table 1.

2 theta and d-space of Mg-Al-Cl LDH according to irradiation dose. Mg-Al-Cl LDH Dose
(kGy) 2 theta
(003) d-space
(A) 2 theta
(006) d-space
(A) Comparative Example 1 0 11.21 7.866 22.61 3.929 Example 1 25 11.16 7.887 22.66 3.941 Example 2 50 11.14 7.916 22.78 3.957 Example 3 75 11.11 7.958 22.30 3.983

As shown in FIG. 2 and Table 2, it can be seen that as the electron beam irradiation dose increases, the d-space increases in the (003) and (006) planes.

<Experimental Example 2> Physical property analysis of HDPE / LDH composite material

1. Oxygen Limit Index ( Limit Oxygen Index , LOI ) Measure

Oxygen Index refers to the lowest concentration of oxygen required to sustain combustion of the ignited material in the ascending flow of oxygen and nitrogen. Oxygen Index (%) = O ₂ / (O ₂ + N ₂ ) × 100 .

In addition, the limit oxygen index (LOI) is a minimum oxygen concentration at which the flammable substance is vertically ignited at the uppermost position to continuously maintain the combustion, and the oxygen limit index is used as an evaluation index of the flammability and flammability of the polymer material do.

In order to measure the flame retardancy of HDPE according to the amount of Mg-Al-Cl LDH produced by irradiation, the HDPE / LDH composite prepared in Examples 4 to 7 and the pure HDPE prepared in Comparative Example 2 The oxygen limit index (LOI) was measured.

The specimens of the samples were prepared as 6.5 mm x 120 mm x 3 mm according to ASTM D2863, and LOI values were measured using a LOI tester of FESTEC Co. The results are shown in Fig.

As shown in FIG. 3, as the addition amount of LDH increases, the oxygen limit index increases and the flame retardancy also increases as compared with the pure HDPE resin.

2. The tensile strength Measure

In order to investigate the mechanical properties of HDPE / LDH composites according to LDH content, the HDPE / LDH composite prepared in Examples 4 to 6 and the pure HDPE prepared in Comparative Example 2 were extruded using UTM (univerydals testing machine) (Tensile strength).

Tensile strength was measured using a dumbbell-shaped sample as described in ASTM D638, and the measurement was performed using an Instron 5569 model. The results are shown in FIG.

As shown in FIG. 4, the tensile strength was increased until the addition amount of Mg-Al-Cl LDH was 10 phr, but the tensile strength decreased when the addition amount was 15 phr.

3. Dynamic Mechanical Analysis Dynamic mechanical analyzer , DMA )

In order to test the durability against the external stress of the HDPE / LDH composite material according to the LDH content, the HDPE / LDH composite material prepared in Example 4 and the pure HDPE prepared in Comparative Example 2 were subjected to dynamic mechanical analysis (DMA) Q800, TA instrument) were analyzed.

The HDPE / LDH composite material was prepared in a size of 12.2 × 60 × 3 mm and analyzed using a dual cantilever method. The results are shown in FIG.

FIG. 5 shows the storage modulus of HDPE / LDH composite according to the addition of LDH, showing the storage modulus of HDPE / LDH composite according to Example 4 in which 5 phr of LDH was added compared with Comparative Example 2, which is pure HDPE without LDH It can be seen that the composite has higher storage elastic modulus with temperature.

Claims

Adding a basic solution to an aqueous solution containing a divalent metal salt and a trivalent metal salt, followed by stirring (step 1); And
And irradiating the aqueous solution of step 1 with 20 to 100 kGy of radiation (step 2).

The method for producing a double layer hydroxide according to claim 1, wherein the divalent metal salt of step (1) comprises one kind of metal selected from the group consisting of magnesium, nickel, copper, zinc, calcium and cobalt.

The process according to claim 1, wherein the trivalent metal salt of step 1 comprises one metal selected from the group consisting of aluminum, chromium, iron, gallium, indium, vanadium, and titanium. Way.

The method of claim 1, further comprising the step of modifying the surface of the double layer hydroxide by adding a surfactant in step 1 above.

5. The method of claim 4, wherein the surfactant is sodium dodecyl benzene sulfonate (SDBS), dodecyl sulfate (DS), and dodecyl benznesulfonate (DBS).

The method according to claim 1, wherein the radiation of step 2 is one selected from the group consisting of X-ray, gamma ray, alpha ray, beta ray, electron ray, proton ray, heavy ion ray, mid ion ray and neutron ray.

A double layer hydroxide prepared by the process of claim 1.

The double layer hydroxide of claim 7, wherein the double layer hydroxide is represented by the following formula (1).

&Lt; Formula 1 >
^{_{[M 2 + (1-x}} ) M 3 + x (OH) 2] x + [A m -] x / m and nH ₂ O

Wherein M ² ⁺ is a cation selected from the group consisting of Mg ² ⁺ , Ni ² ⁺ , Cu ² ⁺ , Zn ² ⁺ , Ca ² ⁺ and Co ² ⁺ ;
The M ³ ⁺ ³ ⁺ is Al, Cr ⁺ ^3, Fe ⁺ ^3, Ga ⁺ ^3, In ⁺ ^3, V ⁺ ^3, and one kind cation selected from the group consisting of Ti ³ ⁺ a;
A shopping ^m ^- is _{^{_{^{CO 3 2 -, SO 4 2}}}} - and NO ₃ ^- one kind of anions selected from the group consisting of a;
X is a number from 0 to 1, and n is a positive number exceeding 0).

A polymer / double layer hydroxide composite comprising the double layer hydroxide of claim 7 in a polymer matrix resin.

The polymer / double layer hydroxide composite material according to claim 9, wherein the polymer is high density polyethylene (HDPE).

11. The polymer / double layer hydroxide composite of claim 9, wherein the double layer hydroxide is mixed in a weight ratio of 5 to 10 phr based on the polymer.