Background technology:
General inorganic powder in use, especially in the time of in add organic systems such as macromolecular material to as the functional agent material, need carry out organic modification of surface to it usually, to increase the consistency of itself and organic matrix, make it reach good dispersion effect, bring into play good action effect.
At present, both at home and abroad the surface modification to inorganic powder generally all adopts the dry method surface treatment, normally inorganic powder is added high-speed mixer, adds organic modifiers under high-speed stirring, heats and fully stirs and finish.There is complex manufacturing in this method, surface treatment is inhomogeneous and problem such as easy generation reunion.Document [silane coupling agent is used for the mechanism of non-metal powder surface modification and uses the problem that should note, Chinese powder industry, 2006 (4): 12-14] has carried out more detailed description to this.
Layered composite metal hydroxides (Layered Double Hydroxides is called for short LDHs) is hydrotalcite again, is a kind of typical anionic type laminated material, and its chemical constitution formula is [M
2+ 1-xM
3+ x(OH)
2] A
N- X/nMH
2O, wherein M
2+, M
3+Represent divalence and trivalent metal cation respectively, A
N-Be interlayer anion, x is M
3+The ionic molar fraction, m is the quantity of crystal water.The kind of the element kind of LDHs main body laminate and proportion of composing, interlayer object and quantity is modulation in relative broad range as required, thereby obtains a series of materials with special construction and performance.The adjustable sex change of LDHs The Nomenclature Composition and Structure of Complexes and the multifunctionality that is caused thus, make it become the type material that a class has research potential and application prospect, be widely used in fields such as fire-retardant, resin treatment, plastic sheeting for farm use as functional agents such as the high smoke-inhibiting flame retardant agent of Halogen, non-toxic heat stabilizer, selective infrared absorbing material and ultraviolet blocking materials.
Provide a kind of among the patent of invention ZL99119386.5 LDHs has been carried out wet-process modified technology, this technology is to add organic modifiers in the LDHs preparation process in the slurries that it washs, under certain temperature, reacted 15~60 minutes, and then filter, drying, reach the purpose of organic modification of surface.Because this method is modification before dry, has overcome the problem that particle is easily reunited in the first dry post-modification process, has realized the integrated of powder preparing and modification, for good product basis has been laid in the application of LDHs.But, because modification is to finish, still need to expend a large amount of bath wateies after washing, especially for the product of difficult washing, the water of productive use amount is huge, and production cost is increased greatly.
Summary of the invention
The purpose of this invention is to provide a kind of technology of utilizing iso-electric point layered composite metal hydroxides to be carried out the surface in situ modification.
Utilize iso-electric point as follows to the concrete operations step that layered composite metal hydroxides carries out the surface in situ modification:
A. be M in molar ratio with solvable divalent metal salt and solvable trivalent metal salt
2+/ M
3+=2~4 are dissolved in and are made into mixing salt solution, wherein [M in the deionized water
2+]=0.1~2.0mol/L; Press n (NaOH)/[n (M
2+)+n (M
3+)]=1.8~2.5 molar ratio, NaOH is dissolved in the alkaline solution that is made into equal volume in the deionized water; Two kinds of solution are added in the full back-mixing liquid film reactor nucleation fast simultaneously,, obtain layered composite metal hydroxides LDHs slurries the slurry reflux crystallization that obtains 5-6 hour; Wherein the quality percentage composition of LDHs is 0.5~20%, and the pH value is greater than 10; Full back-mixing liquid film reactor is seen patent of invention ZL00132145.5
The chemical general formula of described layered composite metal hydroxides LDHs is:
[M
2+ 1-xM
3+ x(OH)
2]
x+(A
n-)
x/2·yH
2O,
Wherein, M
2+Represent divalent metal Mg
2+, Zn
2+, Ca
2+, Cu
2+, Ni
2+, Co
2+, Fe
2+, Mn
2+Or Cd
2+In one or both, preferably Mg
2+, Zn
2+, Ca
2+In one or both;
M
3+Represent trivalent metal cation Al
3+, Ni
3+, Co
3+, Fe
3+, Mn
3+, Cr
3+, V
3+Or Ti
3+In a kind of, preferably Al
3+Or Ni
3+
A
N-Be Cl
-, CO
3 2-, NO
3 -, B
N2-, F
-, Br
-, I
-, SO
4 2-, ClO
3 -, OH
-, PO
4 3-, H
2PO
4 -, WO
4 2-, in Whitfield's ointment, tartrate, L-glutamic acid, oxysuccinic acid, phenylformic acid, hexanodioic acid or the organic sulfonic acid negatively charged ion one or both, preferably CO
3 2-, NO
3 -, Cl
-, SO
4 2-, PO
4 3-, in the phenylformic acid, Whitfield's ointment one or both; X is M
3+The ionic molar fraction; Y is the quantity of crystal water, and its span is 0≤y≤2.
B. be 0.1~30% acid solution with concentration, slowly be added drop-wise under the agitation condition in the above-mentioned LDHs slurries that the pH value of regulation system makes it be lower than the iso-electric point for the treatment of the modification slurries;
Described acid solution is sulfuric acid, hydrochloric acid or salpeter solution;
Described iso-electric point numerical evaluation method is: the dilute sulphuric acid with 1% is regulated the pH value of modification slurries, and the employing electrophoresis apparatus is measured the zeta-potential under the different pH values, draws ζ-pH curve, and the pH value when zeta-potential is zero is the iso-electric point of this material; Above-mentioned LDHs iso-electric point numerical range is 8.6~10.5.
The principle schematic of isoelectric point determination is seen Fig. 1.As can be seen from the figure, descend with the pH value, the zeta-potential of sample constantly increases, from negative value become on the occasion of, wherein, the pH value of correspondence is called iso-electric point when zeta-potential is zero, i.e. A point among the figure.
C. in system, add properties-correcting agent, the add-on of properties-correcting agent be in the system powder total amount 0.1~15%, be warmed up to more than the properties-correcting agent melting temperature, stirring reaction 5~120min isolates the upper strata solid after the cooling, washing, drying obtain the LDHs powder of modification.
Described properties-correcting agent comprises a kind of in stearic acid, sodium stearate, lauric acid, sodium laurate, oleic acid, sodium oleate, palmitinic acid, Sodium pentadecanecarboxylate, silane coupling agent, titanate coupling agent, aluminate coupling agent or the zirconium aluminate coupling agent, preferably stearic acid, sodium stearate, lauric acid, sodium laurate or titanate coupling agent;
Owing to have excessive raw material alkali in the LDHs slurries that steps A obtains, promptly have a large amount of OH
-, this moment pH value generally all more than 11, and LDHs is with permanent positive charge, surface potential shows electropositivity, the OH in these product slurries
-Ion can become the gegenion preferentially adsorbed in the LDHs surface, makes the LDHs particle be in OH
-Encirclement in.
Common modification all is earlier LDHs to be washed, and to remove these gegenions, again it is carried out modification, need expend a large amount of bath wateies, inefficiency like this.And the present invention is before washing, pH value by regulation system makes it to drop to below the iso-electric point of particle, make particle surface show electropositivity, and the quantity of the anti-electric charge of reduction particle surface, add organic modifiers then, make modifier molecules under electrostatic attraction and intermolecular forces effect, clamp-on Stern (stern) layer, with particle surface group generation physical and chemical adsorption, and along with the increase of modifier molecules adsorptive capacity, the OH of surface adsorption
-Quantity can be fewer and feweri, finally reaches the particle surface degree that agent molecule covers fully that is modified, and plays good modified effect.Particle and water fast hierarchical and float on the upper strata of water after the modification are highly susceptible to separating with the aqueous solution.And because organically-modified agent molecule is coated on the inorganic particulate surface, isolated by product and excessive alkaline solution, only needed the little water washing, washing process is simplified greatly.
The mechanism of iso-electric point in-situ techniques modification is: the inorganic particulate surface generally all has the electric charge of different densities, has surface potential, the electric charge of its surface meeting absorption contrary sign constitutes electrostatic double layer in solution, and wherein the gegenion adsorbed close layer that mortise forms at surperficial volume owing to strong attraction is called Stern (stern) layer.The electric charge of these contrary signs concentration from the near to the remote reduces gradually, and the voltage that produces at electrostatic double layer slipping plane place is called Zeta (ζ) current potential, and its numerical value can calculate by the mensuration of electrophoresis or electric osmose speed.Become under the condition in certain temperature, pressure and media pack, the pH value of medium was called iso-electric point (Isoelectric point) when the zeta current potential was zero.
Purified LDHs surface is positively charged, owing to there are a large amount of excessive raw material alkali in the LDHs slurries system that obtains of steps A, the pH value is greater than iso-electric point, surface adsorption a large amount of OH
-, make the LDHs particle electronegative, with the modifier molecules of being with anionic group the electrostatic repulsion effect has taken place, simultaneously owing to OH in the solution
-Concentration is excessive, a large amount of OH
-Clamp-on the stern layer LDHs particle has been formed fine and close parcel, spatially also play and stop modifier molecules to enter the effect that stem layer and particle surface react, do not reach the purpose of organic modification of surface; Regulate pH value by dilute sulphuric acid, when system pH during, LDHs ion band positive electricity less than iso-electric point, the effect that can inhale mutually with the modifier molecules generation static of being with anionic group, and the OH of surface adsorption
-Ion is less, and is more loose to the parcel of LDHs particle, and this moment, modifier molecules can more easily be clamp-oned the stern layer under electrostatic attraction and intermolecular forces effect, and with particle surface generation physical and chemical adsorption, thereby reach the purpose of organic modification of surface.Along with the increase of modifier molecules adsorptive capacity, the OH of surface adsorption
-Quantity can be fewer and feweri, finally reaches the LDHs surface degree that agent molecule covers fully that is modified.
The LDHs surface presents hydrophobic nature through modify and graft organic molecule rear surface, can float on the upper strata with water stratification very soon, has simplified the separating and filtering process.In addition, because organically-modified agent molecule is direct and the LDHs surface bonding, can when modification, the gritty particle in the LDHs and the aqueous solution be kept apart, simplified washing process greatly, reduce the bath water amount, reduced production costs, can also prevent particle agglomeration well simultaneously.The result shows that the bath water amount has reduced more than 80%, and Na in the product
+Be lower than 0.05% Deng hetero-ion content.
Characteristics of the present invention are before preparation feedback finishes back and washing, regulation system pH value makes the iso-electric point less than particle, directly adding properties-correcting agent then carries out in-situ modified, make modifier molecules can with the surface group generation physical and chemical adsorption effect of inorganic particulate, and be coated on the surface, reach good modified effect.This method has not only effectively been avoided the ion reunion, has also simplified washing process greatly, has reduced the bath water amount.
Embodiment:
Embodiment 1
With 102.5g Mg (NO
3) 6H
2O and 75.0gAl (NO
3)
39H
2O is dissolved in and is made into the 500ml mixing salt solution in the deionized water, with 38.4g NaOH and 42.3g Na
2CO
3Be made into the 500ml alkaline solution with water, two kinds of solution are added full back-mixing liquid film reactor simultaneously, the slurries that obtain place under the 2L flask agitation condition and are heated to backflow, and reaction 6h obtains Mg
4Al
2(OH)
12CO
34H
2The O slurries.Slurries are cooled to room temperature, and the pH value of slurries is 10.6 after measured, and slurries are divided into 4 parts, and every part contains the about 5g of product, measures Mg with DXD2II type television microscopy electrophoresis apparatus
4Al
2(OH)
12CO
34H
2The iso-electric point of O is 9.9.Be to be added drop-wise to respectively in above-mentioned 4 parts of slurries under 0.2% the dilute hydrochloric acid solution agitation condition with concentration, make the pH value of 4 parts of slurries be respectively 10.5,10.0,9.5 and 9.Be warming up to 80 ℃, add stearic acid 0.5g respectively, stirring reaction 30min postcooling is to room temperature.Found that the pH value is layering not occur in 10.5 and 10.0 the slurries, the pH value is very fast generation layering in 9.5 and 9.0 slurries, and the white solid product floats on the water surface.Isolate the upper strata solid to stratified system takes place,, obtain the LDHs powder of modification again through washing, drying.
Slurries carry out the modification result as shown in Figure 2 under different pH condition.Can find out very clearly that from figure when system pH was carried out modification greater than iso-electric point, organically-modified agent molecule failed to graft on the LDHs surface, reaction finishes back LDHs and still is dispersed in the water, does not reach modified effect; When system pH during less than iso-electric point, LDHs all floats on the upper strata of water soon, shows that organically-modified agent molecule has grafted on the LDHs surface, has reached good modified effect.
(Cu target K alpha-ray, 5 ° of sweep velocitys/min), the result as shown in Figure 3 to adopt the Japanese Shimadzu XRD-6000 of company type X-ray powder diffraction instrument to measure the crystalline structure of above-mentioned sample.As can be seen from the figure, the characteristic diffraction peak peak shape of sample point is alarmmed, and baseline is low flat, and interpret sample has complete layered crystal structure, and the adding of acid does not produce sample and destroys when regulating the pH value.
Adopt German Bruker Vector22 type FT-IR infrared spectrometer that above-mentioned sample is carried out infrared analysis, the result as shown in Figure 4.Spectrogram is consistent with the standard spectrogram of LDHs, wherein 1384cm
-1The absorption peak at place is CO
3 2-Unsymmetrically υ
3Vibration modes, intensity and go out the peak position and do not change illustrates that preparation process does not exert an influence to product.
Embodiment 2
With 129.4g ZnSO
47H
2O and 50.0gAl
2(SO
4)
318H
2O is dissolved in and is made into the 300ml mixing salt solution in the deionized water, 38.4g NaOH is dissolved in proportionaling alkali-forming solution in the 300ml water, two kinds of solution are added full back-mixing liquid film reactor simultaneously, and the slurries that obtain place under the 2L flask agitation condition and are heated to backflow, and reaction 6h obtains Zn
6Al
2(OH)
12SO
44H
2The O slurries are cooled to room temperature, are divided into 4 parts, and every part contains the about 5g of product, and the pH value of slurries is 10.5 after measured.Measure Zn with DXD2II type television microscopy electrophoresis apparatus
6Al
2(OH)
12SO
44H
2The iso-electric point of O is 9.7.Configuration concentration is 0.2% dilution heat of sulfuric acid, is added drop-wise under the agitation condition in the above-mentioned slurries, and regulation system pH value is 10.5,10.0,9.5 and 9 respectively.Be warming up to 80 ℃, add titanic acid ester 0.25g respectively, stirring reaction 60min postcooling is to room temperature.Found that not layering of system when the pH value is 10.5 and 10.0, the very fast generation layering of system when the pH value is 9.5 and 9.0, the white solid product floats on the water surface.Isolate the upper strata solid to stratified system takes place, washing, drying obtain the LDHs powder of modification.
Adopt the Japanese Shimadzu ICPS-7500 of company type plasma emission spectrum that embodiment 2 samples are carried out elementary composition analysis, the result is as shown in table 1.As can be seen from the table, sample is elementary composition suitable with theoretical value, and hetero-ion content such as Na is very low, illustrates that washing effect is remarkable, and modifying process produces sample and destroys.
The ultimate analysis of table 1 sample
Embodiment 3
With 76.9g Mg (NO
3)
26H
2O and 56.3g Al (NO
3)
39H
2O is dissolved in and is made into the 500ml mixing salt solution in the deionized water, 36.0g NaOH is dissolved in proportionaling alkali-forming solution in the 300ml water, two kinds of solution are added full back-mixing liquid film reactor simultaneously, and the slurries that obtain place under the 2L flask agitation condition and are heated to backflow, and reaction 6h obtains Mg
4Al
2(OH)
12NO
34H
2The O slurries are cooled to room temperature, are divided into 4 parts, and every part contains the about 5g of product, and the pH value of slurries is 10.2 after measured.Measure Mg with DXD2II type television microscopy electrophoresis apparatus
4Al
2(OH)
12NO
34H
2The iso-electric point of O is 9.4.Configuration concentration is 0.1% dilution heat of sulfuric acid, is added drop-wise under the agitation condition in the above-mentioned slurries, and regulation system pH value is 10.5,10.0,9.5 and 9 respectively.Be warming up to 80 ℃, add lauric acid 0.2g respectively, stirring reaction 30min postcooling is to room temperature.Found that not layering of system when the pH value is 10.5,10.0 and 9.5, the very fast generation layering of system when the pH value is 9.0, the white solid product floats on the water surface.Isolate the upper strata solid to stratified system takes place, washing, drying obtain the LDHs powder of modification.
Embodiment 4
With 15.4g Mg (NO
3)
26H
2O and 11.3g Al (NO
3)
39H
2O is dissolved in and is made into the 200ml mixing salt solution in the deionized water, 8.3g Whitfield's ointment and 9.6g NaOH are made into proportionaling alkali-forming solution in the 200ml water, two kinds of solution are added full back-mixing liquid film reactor simultaneously, and the slurries that obtain place under the 1L flask agitation condition and are heated to backflow, and reaction 6h obtains Mg
4Al
2(OH)
12(HOC
6H
4COO) 4H
2The O slurries are cooled to room temperature, are divided into 4 parts, and every part contains the about 2g of product, and the pH value of slurries is 10.1 after measured.Measure Mg with DXD2II type television microscopy electrophoresis apparatus
4Al
2(OH)
12(HOC
6H
4COO) 4H
2The iso-electric point of O is 8.9.Configuration concentration is 0.1% dilution heat of sulfuric acid, is added drop-wise under the agitation condition in the above-mentioned slurries, and regulation system pH value is 10.0,9.5,9.0 and 8.5 respectively.Be warming up to 80 ℃, add silane coupling agent 0.1g respectively, stirring reaction 30min postcooling is to room temperature.Found that not layering of system when the pH value is 10.0,9.5 and 9.0, the very fast generation layering of system when the pH value is 8.5, the white solid product floats on the water surface.Isolate the upper strata solid to stratified system takes place, washing, drying obtain the LDHs powder of modification.