U.S. patent application number 09/874242 was filed with the patent office on 2002-01-17 for hydrotalcite compounds of low uranium (u) content and processes for their preparation.
This patent application is currently assigned to KYOWA CHEMICAL INDUSTRY CO., LTD.. Invention is credited to Okada, Akira, Shimizu, Koji, Yamashita, Satoko.
Application Number | 20020006375 09/874242 |
Document ID | / |
Family ID | 26555088 |
Filed Date | 2002-01-17 |
United States Patent
Application |
20020006375 |
Kind Code |
A1 |
Okada, Akira ; et
al. |
January 17, 2002 |
Hydrotalcite compounds of low uranium (U) content and processes for
their preparation
Abstract
Hydrotalcite compounds useful as additives to synthetic resins
such as epoxy resins which are used as, in particular, sealant for
semiconuctor devices such as transister, IC, LSI and the like,
which are characterized by having a composition represented by the
formula (1) below:
M.sub.1-X.sup.2+Al.sub.X.sup.3+(OH).sub.2A.sub.X/2.sup.2-.multidot.mH.sub.-
2O (1) in which M.sup.2+ is at least one of Mg.sup.2+ and
Zn.sup.2+, x is a positive number in the range of
0.2.ltoreq.x.ltoreq.0.5, A.sup.2- is at least one of
CO.sub.3.sup.2- and SO.sub.4.sup.2-, and m is a number in the range
of 0-2, and having a uranium (U) content of not more than 10 ppb,
an average secondary particle size of not more than about 3 .mu.m
and a BET specific surface area of not more than 30 m.sup.2/g.
Inventors: |
Okada, Akira;
(Takamatsu-shi, JP) ; Yamashita, Satoko;
(Nakatado-gun, JP) ; Shimizu, Koji; (Sakaide-shi,
JP) |
Correspondence
Address: |
Sherman & Shalloway
413 N. Washington Street
Alexandria
VA
22314
US
|
Assignee: |
KYOWA CHEMICAL INDUSTRY CO.,
LTD.
|
Family ID: |
26555088 |
Appl. No.: |
09/874242 |
Filed: |
June 6, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09874242 |
Jun 6, 2001 |
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09398428 |
Sep 17, 1999 |
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6287532 |
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Current U.S.
Class: |
423/420.2 ;
257/E23.119 |
Current CPC
Class: |
H01L 2924/0002 20130101;
C01P 2004/62 20130101; C01P 2006/80 20130101; C01P 2006/12
20130101; H01L 23/293 20130101; C01F 7/785 20220101; C01P 2002/72
20130101; C01G 9/006 20130101; C01P 2002/22 20130101; C01P 2006/44
20130101; C01P 2002/77 20130101; C01P 2004/61 20130101; C01P
2006/88 20130101; H01L 2924/0002 20130101; H01L 2924/00
20130101 |
Class at
Publication: |
423/420.2 |
International
Class: |
C01B 031/24 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 1998 |
JP |
283,557/98 |
Nov 10, 1998 |
JP |
333,357/98 |
Claims
1. Hydrotalcite compounds which are characterized in that they are
represented by formula (1) below:
M.sub.1-X.sup.2+Al.sub.X.sup.3+(OH).sub-
.2A.sub.X/2.sup.2-.multidot.mH.sub.2O (1) in which M.sup.2+ is at
least one of Mg.sup.2+ and Zn.sup.2+, x is a positive number in the
range of 0.2.ltoreq.x.ltoreq.0.5, A.sup.2- is at least one of
CO.sub.3.sup.2- and SO.sub.4.sup.2-, and m is a number in the range
of 0-2, and have a uranium (U) content of not more than 10 ppb, an
average secondary particle size of not more than about 3 .mu.m and
a BET specific surface area of not more than 30 m/g.
2. Hydrotalcite compounds according to claim 1, which are
surface-treated with at least one surface-treating agent selected
from the group consisting of higher fatty acids, anionic
surfactants, silane-containing coupling agents, titanate-containing
coupling agents, aluminium-containing coupling agents and
phosphoric acid esters of higher alcohols.
3. Hydrotalcite compounds according to claim 1, which are
surface-treated with not more than 3% by weight thereof of
silane-containing coupling agent.
4. Hydrotalcite compounds according to any one of claims 1-3, which
are additives and fillers for synthetic resins.
5. Hydrotalcite compounds according to any one of claims 1-4, in
which A.sup.2- in the above formula (1) is CO.sub.3.sup.2-.
6. A process for producing the hydrotalcite compounds as defined in
claim 1 which is characterized by (1) subjecting an aqueous
solution of water-soluble aluminium compound and an aqueous
solution of water-soluble magnesium compound and/or water-soluble
zinc compound to a coprecipitation reaction under alkaline
conditions, the composition of the starting materials satisfying
the molar ratio within the range defined by the formula (2) below:
3 0.15 at least one of CO 3 2 - and SO 4 2 - M 2 + + Al 3 + 1.25 ,
( 2 ) in which M.sup.2+ stands for at least one of Mg.sup.2+ and
Zn.sup.2+, at temperatures of 10-50.degree. C. under stirring, and
(2) subjecting the resulting coprecipitation product, without
isolating it from the suspension which served as the mother liquor
of the coprecipitation reaction, to a hydrothermal reaction at
temperatures of 90-200.degree. C. for at least 0.5 hour, (3) so
adjusting the reaction conditions in that occasion that the pH of
the reaction suspension which has undergone the hydrothermal
reaction should fall within the range of 7.0-13.5.
7. A process for producing the hydrotalcite compounds according to
claim 6, which comprises (1) subjecting an aqueous solution of
water-soluble aluminium compound and an aqueous solution of
water-soluble magnesium compound and/or water-soluble zinc compound
to a coprecipitation reaction under alkaline conditions, the
composition of the starting materials satisfying the molar ratio
within the range defined by the formula (2-a) below: 4 0.15 CO 3 2
- M 2 + + Al 3 + 1.25 , (2-a) in which M.sup.2+ stands for at least
one of Mg.sup.2+ and Zn.sup.2+, at temperatures of 10-50.degree. C.
under stirring.
8. A process for producing the hydrotalcite compounds according to
claim 6 or 7, which comprises, after carrying out the above (2)
hydrothermal reaction, (4) suspending the hydrothermal reaction
product, which has been washed with water, in an aqueous solution
of ammonium carbonate and/or alkali (hydrogen)carbonate, followed
by 1-24 hours' stirring at temperatures of 10-100.degree. C. (an
elution treatment).
9. Hydrotalcite compounds according to claim 1, which are free from
water of crystallization or have lowered content of water of
crystallization, as obtained by further heating the hydrotalcite
compounds as described in claim 1 at temperatures of
200-350.degree. C. for 0.5-24 hours.
10. Hydrotalcite compounds according to claim 1 which are free from
water of crystallization, whose "m" value referring to the formula
(1) of claim 1 is 0.05-0.
Description
[0001] This invention relates to hydrotalcite compounds of low
uranium (U) content and processes for their preparation. More
particularly, the invention concerns hydrotalcite compounds which
are useful as ion scavenger or various stabilizers for epoxy resins
used for sealing large-capacity, high-integration memory
semiconductor devices, without impairing reliability of the devices
against soft errors.
[0002] Hydrotalcites having concurrently the various properties
required for an inorganic powder additive for resins, such as good
dispersibility and processability and no deteriorating effect on
the products' appearance were disclosed in Japanese Patent KOKAI
No. 80447/80A. The hydrotalcites shown in this publication are
actually used in many synthetic resins as heat-stabilizers of PVC,
stabilizers for polyolefins and the like.
[0003] Whereas, semiconductor devices such as transistor, IC, LSI
and the like need to be sealed, for protection and insulation from
contact, contamination and moisture from outside. Presently, resin
sealing methods are advantageous from the standpoints of
productivity and economy, and are widely practiced. In particular,
epoxy resins are used for sealing semiconductor devices because of
their favorable electrical characteristics, moisture resistance and
adherability. Hydrotalcite compounds are used as ion scavenger or
the like in such epoxy resin sealing material for semiconductor
devices to perform the roles and functions of prevention of
corrosion and improvement in moisture resistance of wiring.
[0004] With the still larger capacities and higher integration
given to recent semiconductor memories, occurrence of soft errors
caused by alpha ray emitted upon decay in radioactive substances
such as uranium, thorium, etc. which are contained in the sealing
resin compositions begins to create problems. For example, the
content of uranium and thorium is required not to exceed 1 ppb
(ng/g) for 4M bit memories, and not to exceed 0.1 ppb (ng/g) for
4-16M bit memories, in order to secure reliability against soft
errors. In consequence, hydrotalcite compounds, which are blended
in the epoxy resin sealant in such a small (minor) amount as not
more than a few percent to said resin, are also required to contain
not more than micro-level of radioactive substances.
[0005] An object of the present invention is to provide
hydrotalcite compounds which are useful as ion scavengers for epoxy
resin compositions serving as sealant for memory semiconductor
devices in which capacity increase and raise in integration level
are highly advanced, and which possess high reliability against
soft errors. This object can be fulfilled by provision of high
purity hydrotalcite compounds whose radioactive substance content,
i.e., that of uranium and thorium, is exceeding low. Thus, the
theme of the present invention is to provide hydrotalcite compounds
which possess the properties required for additives to resin and
have extremely low uranium content, and processes for their
preparation.
[0006] The hydrotalcite compounds of the present invention are
characterized in that they have the composition expressed by the
formula (1) below:
M.sub.1-X.sup.2+Al.sub.X.sup.3+(OH).sub.2A.sub.X/2.sup.2-.multidot.mH.sub.-
2O (1)
[0007] [in which M.sup.2+ is at least one of Mg.sup.2+ and
Zn.sup.2+,
[0008] x is a positive number of 0.2.ltoreq.x.ltoreq.0.5,
[0009] A.sup.2- is at least one of CO.sub.3.sup.2- and
SO.sub.4.sup.2-, and
[0010] m is a number of 0 to 2],
[0011] have a uranium (U) content not more than 10 ppb, an average
secondary particle size not more than about 3 .mu.m and a BET
specific surface area of not more than 30 m.sup.2/g.
[0012] The hydrotalcite compounds of the present invention are
preferably those that are surface-treated with at least one
surface-treating agent selected from the group consisting of higher
fatty acid, anionic surfactant, silane-containing coupling agent,
titanate-containing coupling agent, aluminium-containing coupling
agent and phosphoric acid ester of higher alcohol.
[0013] Of those, particularly the hydrotalcite compounds which are
surface-treated with not more than 3% by weight thereof of a
silane-containing coupling agent are preferred.
[0014] The hydrotalcite compounds of the present invention are
conveniently used as additives and fillers for synthetic resin.
[0015] Of the hydrotalcite compounds of above formula (1) of the
present invention, particularly those whose A.sup.2- is
CO.sub.3.sup.2- are preferred. Whereas, those in which a part of
CO.sub.3.sup.2- is replaced with the other anion, eg., those
containing not more than 1/5 mol of Al (not more than 40 mol % of
--CO.sub.3.sup.2-), in particular, not more than {fraction (1/10)}
mol of Al (not more than 20 mol % of --CO.sub.3.sup.2-), of
SO.sub.4.sup.2- are also preferred.
[0016] The hydrotalcite compounds of low uranium content according
to the invention can be prepared through the steps of
[0017] (1) coprecipitation reaction of aqueous solution of a
water-soluble aluminium compound with aqueous solution of a
water-soluble magnesium compound and/or a water-soluble zinc
compound under alkaline condition, at a composition of the starting
materials satisfying the molar ratio in the range defined by the
formula (2) below: 1 0.15 at least one of CO 3 2 - and SO 4 2 - M 2
+ + Al 3 + 1.25 ( 2 )
[0018] [in which M.sup.2+ stands for at least one of Mg.sup.2+ and
Zn.sup.2+], at temperatures ranging 10-50.degree. C. and under
stirring [hereafter may be referred to as step (1)], and
[0019] (2) hydrothermal reaction of the resultant coprecipitation
reaction product in the form of the suspension as formed in the
step (1) reaction, at temperatures in the range of 90-200.degree.
C. for at least 0.5 hour [hereafter may be referred to as step
(2)], in which occasion
[0020] (3) adjusting the reaction conditions so that pH of the
reaction suspension after the hydrothermal reaction falls within
the range of 7.0 to 13.5.
[0021] In the production process according to the invention, it is
particularly preferred to carry out the coprecipitation reaction
(1) of aqueous solution of a water-soluble aluminium compound with
aqueous solution of a water-soluble magnesium compound and/or
water-soluble zinc compound under alkaline condition at the
composition of the starting materials satisfying the molar ratio in
the range defined by the formula (2-a) below: 2 0.15 CO 3 2 - M 2 +
+ Al 3 + 1.25 (2-a)
[0022] [in which M.sup.2+ stands for at least one of Mg.sup.2+ and
Zn.sup.2+], at temperatures ranging 10-50.degree. C. and under
agitation.
[0023] In the present invention, it is also preferred to carry out
the hydrothermal reaction of the coprecipitation reaction product
which is obtained in said step (1), leaving said product in the
state of suspension in the mother liquor of the reaction, at
temperatures of 90-200.degree. C. for at least 0.5 hour, preferably
for 0.5-24 hours, while so adjusting the reaction conditions that
pH of the reaction suspension after the hydrothermal reaction falls
within the range of 7.0-13.5 [the step (2)], and then
[0024] (4) to suspend the hydrothermal reaction product which has
been washed with water, in an aqueous solution of ammonium
carbonate and/or alkali (hydrogen)carbonate and to stir the
suspension at temperatures of 10-100.degree. C. for 1-24 hours (an
eluting treatment).
[0025] Preferred concentration of ammonium carbonate and/or an
alkali carbonate or alkali hydrogencarbonate in the aqueous
solution used in (4) above is from 0.1 to 3.0 mols/liter.
[0026] While the pH value of the suspension after the hydrothermal
reaction of step (2) in the production process of the present
invention is an important condition which controls the elimination
ratio of uranium, basically it may be the one sufficient for
UO.sub.2.sup.2+ ions to take a form of such complex ions as
UO.sub.2 (OH).sub.3.sup.-, UO.sub.2(CO.sub.3).sub.2.sup.2-,
UO.sub.2(CO.sub.3).sub.3.sup.4- and the like in the aqueous
solution, i.e., 7.0 or higher. At exceedingly high pH region,
surface charge of the hydrotalcite compounds reverses to negative
level and electrically repulses with the complex anions of uranium
to prevent latter's absorption or the like, which enables better
uranium elimination and the intended uranium content level can be
achieved without the elution step (4) using ammonium carbonate,
alkali (hydrogen)carbonate, etc. According to the production
process of the present invention inclusive of the elution treatment
step (4), the suitable pH range for the suspension after the
hydrothermal reaction is 7.0-13.5, preferably 9.0-13.0. The
mechanism for uranium elimination is not yet clear, but we presume:
during this hydrothermal reaction, the hydrotalcite compounds
undergo crystal growth to have reduced BET specific surface area,
whereby dispersibility of the particles is improved and not only
powder properties favorable for resin additives are imparted, but
also uranium ions which are a kind of impurities are expelled to
outside the crystals due to the purifying action of the substance
accompanying the procedure of crystal growth. Thus expelled uranium
ions either stay in the solution or, if re-adsorbed, remain in the
surface portion of the crystals, allowing easy elution thereof with
aqueous carbonate solution or the like. We infer that the mother
liquor of the reaction having a high pH and containing anions
serviceable as ligand contributes to increase the capacity of the
solution for retaining the expelled uranium ions as dissolved
therein, through formation of their complex ions or the like.
[0027] The hydrothermal reaction can be conveniently carried out at
temperatures in a range of 90-200.degree. C., for 0.524 hours,
preferably at 100-170.degree. C. for 1-10 hours. When the
temperature-time conditions are lower than the specified ranges,
crystal growth of the hydrotalcite compounds becomes insufficient,
which tends to lead to incomplete dispersibility of the compounds
and aggravates uranium removing efficiency. Thus, such conditions
are inconvenient for obtaining the product of the present
invention. Again, adoption of temperatures and time higher and
longer than the specified ranges does not lead to a notable
increase in the uranium removing efficiency, while production costs
futilely increase.
[0028] As the eluent to be used in the elution treatment, aqueous
ammonium carbonate solution, aqueous sodium hydrogencarbonate
solution, aqueous sodium carbonate solution, mixed aqueous solution
of ammonium carbonate/sodium hydrogencarbonate, mixed aqueous
solution of ammonium carbonate/sodium carbonate, etc. at
concentrations ranging from 0.1 to 3.0 mols/liter are conveniently
used, preferred concentration of those aqueous solutions being
0.5-2.5 mols/liter.
[0029] As the water-soluble compounds or salts of magnesium, zinc
and aluminium which are to be used in the step (1) coprecipitation
reaction in the above-described production process of hydrotalcite
compounds of low uranium content of the present invention,
magnesium compounds such as magnesium chloride, magnesium sulfate,
magnesium nitrate, magnesium acetate, magnesium hydroxide,
magnesium oxide, bittern, brine and the like; zinc compounds such
as zinc chloride, zinc nitrate, zinc sulfate, zinc acetate and the
like; and aluminium compounds such as aluminium chloride, aluminium
sulfate, aluminium nitrate, sodium aluminate and the like can be
named as examples. Also examples of the alkaline compounds to be
used for adjusting pH of the suspension formed through the
coprecipitation reaction and hydrothermal reaction to a value
within the range of 7.0 to 13.5 (at room temperature) include
sodium hydroxide, potassium hydroxide, sodium carbonate, potassium
carbonate, aqueous ammonia and ammonia gas.
[0030] Examples of carbonates to be used in the step (4) elution
treatment include ammonium carbonate, sodium carbonate, sodium
hydrogencarbonate, potassium carbonate and potassium
hydrogen-carbonate. It is also permissible to use them in
combinations such as ammonium carbonate/sodium carbonate, ammonium
carbonate/sodium hydrogencarbonate or the like, at optional mixing
ratios within the prescribed concentration range (0.1-3.0
mols/liter).
[0031] In the occasion of incorporating the hydrotalcite compounds
of low uranium content of the present invention in synthetic
resins, the compounds may be surface-treated with at least one
surface-treating agent selected from the group consisting of higher
fatty acids, anionic surfactants, silane-containing coupling
agents, titanate-containing coupling agents, aluminium-containing
coupling agents and phosphoric acid esters of higher alcohols, to
be imparted with improved compatibility and processability.
Examples of preferred surface-treating agents according to the
invention include: higher fatty acids such as lauric acid, palmitic
acid, stearic acid, arachidic acid, oleic acid, erucic acid, etc.
and alkali metal salts of these higher fatty acids; anionic
surfactants such as sulfate ester salts of higher alcohols like
stearyl alcohol, oleyl alcohol, etc., amide bond sulfate ester
salts, ether bond alkylallyl sulfonic acid salts, etc.; phosphoric
acid esters such as acid or alkali metal salts or amine salts,
which are mono- or di-esters between orthophosphoric acid and oleyl
alcohol, stearyl alcohol or the like, or mixtures of these esters;
silane-containing coupling agents such as vinylethoxysilane,
.gamma.-methacryloxypropyltrimethoxysilane,
.gamma.-glycidoxypropyltrimethoxy silane,
vinyl-tris(2-methoxyethoxy)sila- ne,
.gamma.-aminopropyltrimethoxysilane and
N-phenyl-.gamma.-amino-propylt- rimethoxysilene;
titanate-containing coupling agents such as isopropyl
triisostearoyl titanate, isopropyl tris(dioctylpyrophosphate)
titanate and isopropyl tridecyl-benzenesulfonyl titanate; and
aluminum-containing coupling agents such as acetalkoxyaluminum
diisopropylate, etc.
[0032] As methods of the surface treatment, there are wet method
and dry method. In the wet method, a surface-treating agent as
named above in liquid or emulsion state is added to slurry of the
hydrotalcite compound, and sufficiently mixed under stirring at a
temperature of about 10-100.degree. C. In the dry method, powder of
the hydrotalcite compound is put in a mixer such as a Henschel
mixer, to which the surface-treating agent in liquid, emulsion or
solid state is added and sufficiently mixed with or without
heating. Preferably, the surface-treating agent is used in an
amount of about 0.05- about 10% by weight of the hydrotalcite
compound.
[0033] Examples of the synthetic resins in which the hydrotalicte
compounds of low uranium content of the present invention are
conveniently used include:
[0034] polyolefine resins such as ethylene homepolymers,
ethylene/.alpha.-olefine copolymers; ethylene/vinyl acetate or
ethyl acrylate or methyl methacrylate copolymers, propylene
homopolymers, propylene/.alpha.-olefine copolymers, .alpha.-olefine
homopolymers or copolymers; and their halogenated resins;
[0035] polyamide resins such as ethylene/propylene thermoplastic
elastomers, nylon 6, 6.6, 1.1, 1.2, 4.6, 6.10, 6.12, etc.;
[0036] epoxy resins such as bisphenol A epoxy resins, novolac epoxy
resins, alicyclic epoxy resins, glycidyl epoxy resins, biphenyl
epoxy resins, naphthalene ring-containing epoxy resins,
cyclopentadiene-contain- ing epoxy reins; and polyester resins such
as PET, PBT, etc., and
[0037] polyurethane resins which are the reaction products of
polyisocyanates like organic diisocyanates, polyols like diols and
polyamines like diamines.
[0038] When hydrotalcite compounds are heated, release of water of
crystallization starts to take place in the vicinity of about
180-230.degree. C. When such problems as foaming, silver streaks or
other inconveniences attributable to release of the crystallization
water are expected in the application to synthetic resins whose
processing (or treating such as crosslinking) temperatures are
relatively high, eg., 200.degree. C. or higher, the hydrotalcite
compounds of the present invention can be heated in advance at
temperatures of 200-350.degree. C. for 0.5-24 hours to render them
dehydrated type [referring to the formula (1), those in which m is
approximately 0.05-0, i.e., close to 0]. Such dehydrated type
hydrotalcite compounds have a relatively higher uranium content in
comparison with the original compounds containing water of
crystallization, but have approximately the same levels of chemical
properties such as acid-neutralizing ability and ion-exchange
ability and physical properties such as secondary particle size,
specific surface area, etc., and exhibit unchanged performance when
used in the same application.
[0039] Physically, these dehydrated type hydrotalcite compounds are
such that the water of crystallization present between crystal
layers is removed but anions remain between the layers as they are.
Their powder X-ray diffraction (XRD) chart changes from that of the
original compound containing water of crystallization. That is,
because it has lost its inter-layer water of crystallization, the
inter-layer distance is shrunken and narrowed. In consequence, in
the XRD chart, the diffraction lines of (001) plane shift to higher
angle side (direction of less interlayer distance).
[0040] Hereinafter the invention is explained in further details,
referring to working Examples and Comparative Examples. The
quantitative analysis of uranium in hydrotalcite compounds was
conducted through the steps of dissolving individual sample in
hydrochloric acid and perchloric acid, diluting the solution with
diluted nitric acid and measuring the uranium in the liquid by ICP
mass spectrometry. Secondary particle size was measured by laser
diffraction scattering method, as to each sample as added to water
or an organic solvent and dispersed with ultrasonic wave
treatment.
[0041] Specific surface areas were determined based on the amount
of nitrogen gas adsorption; using BET process.
REFERENTIAL EXAMPLE
[0042] The results of analyzing uranium and thorium in DHT-4A
(trade name), produced by Kyowa Chemical Industries, Co. Ltd.,
which is a commercially available synthetic hydrotalcite and is
currently most widely used as an additive to synthetic reins, are
shown below.
1 TABLE 1 U (ng/g) Th (ng/g) DHT-4A 210 <5 unit: ng/g (ppb)
[0043] From the above data, it can be understood that, for example,
blending of 5% by weight of the commercial synthetic hydrotalcite
results in a resin composition with a uranium content of about 10
ppb, and such 2-digits uranium content of currently sold products
must be reduced. Furthermore, when hydrotalcite is synthesized
using conventional starting materials, thorium is always less than
the level of detection limit, and it is also understood that
reduction in the uranium content is the hurdle to overcome to serve
the present object.
Example 1
[0044] Bittern of Mg concentration 1.5 mols/liter [which contained
50 ng/g (ppb) of uranium as converted per Mg(OH).sub.2] 361 ml and
an aqueous industrial grade aluminium sulfate solution of Al
concentration 1.03 mols/liter [which contained 576 ng/g (ppb) of
uranium as converted per Al(OH).sub.3] 117 ml were mixed. This
mixed aqueous solution was placed in a 2 liter-beaker, and into
which 3.4 N aqueous sodium hydroxide solution 585 ml and an aqueous
solution of 0.8 mol/liter sodium carbonate 226 ml were poured under
vigorous stirring at room temperature. The stirring was continued
for about 30 minutes to provide a coprecipitation product.
[0045] The suspension of the coprecipitation product which was
concentrated by sedimentation to a volume of 700 ml was transferred
into a 0.98-liter autoclave and subjected to a hydrothermal
reaction at 170.degree. C. for 6 hours. After subsequent cooling,
pH of the suspension was 13.17 (30.1.degree. C.). The product was
recovered by filtration, washed with water and dried at 95.degree.
C. for 18 hours, and the dry product was sieved with a 100-mesh
sieve.
[0046] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement. Its uranium (as U) content
was 8 ppb [ng/g (dry powder)], average secondary particle size was
1.0 .mu.m and BET specific surface area was 11.2 m.sup.2/g.
[0047] The product's chemical formua as determined from the result
of its chemical analysis was as follows:
Mg.sub.0.72Al.sub.0.27(OH).sub.2(CO.sub.3).sub.0.13.0.59H.sub.2O.
Example 2-1
[0048] Using the same starting materials as those of Example 1, the
operations of Example 1 were repeated, except that the amounts of
3.4 N aqueous sodium hydroxide solution and 0.8 mol/liter aqueous
sodium carbonate solution were changed to 478 ml and 226 ml,
respectively. The suspension after the hydrothermal reaction at
170.degree. C. for 6 hours had a pH of 12.08 (28.6.degree. C.).
[0049] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement. Its uranium (as U) content
was 17 ppb [ng/g (dry powder)], average secondary particle size was
0.59 .mu.m and BET specific surface area was 13.4 m.sup.2/g.
[0050] The product's chemical formula as determined from the
results of its chemical analysis was as follows:
Mg.sub.0.70Al.sub.0.30(OH).sub.2(CO.sub.3).sub.0.15.0.54H.sub.2O.
Example 2-2
[0051] Ammonium carbonate of first class grade 47 g was dissolved
in deionized water and the total volume of the solution was
adjusted to 700 ml, which was put in a 1-liter beaker. Under
stirring, 27 g of the hydrotalcite compound which was obtained in
Example 2-1 was added to the solution and stirred for 20 hours at
room temperature. The product was recovered by filtration, washed
with water and dried at 95.degree. C. for 18 hours. The dry product
was sieved with a 100-mesh sieve.
[0052] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement. Its uranium (as U) content
was not more than 5 ppb (ng/g), average secondary particle size was
0.59 .mu.m and BET specific surface area was 13.0 m.sup.2/g. The
product's chemical formula as determined from the result of its
chemical analysis was as follows:
Mg.sub.0.69 Al.sub.0.30(OH).sub.2
(CO.sub.3).sub.0.15.0.54H.sub.2O.
Example 2-3
[0053] A 0.5 mol/liter aqueous industrial grade sodium carbonate
solution 700 ml was placed in a 1-liter beaker, into which 27 g of
the hydrotalcite compound obtained in Example 2-1 was added under
stirring, followed by 20 hours' stirring at room temperature. The
product was recovered by filtration, washed with water and dried at
95.degree. C. for 18 hours. The dry product was sieved with a
100-mesh sieve. Said product was identified to be a hydrotalcite
compound by powder X-ray diffraction measurement. Its uranium (as
U) content was 5 ppb (ng/g), average secondary particle size was
0.59 .mu.m and BET specific surface area was 13.3 m.sup.2/g The
product's chemical formula as determined from the result of its
chemical analysis was as follows:
Mg.sub.0.70Al.sub.0.30(OH).sub.2(CO.sub.3).sub.0.15.0.54H.sub.2O.
Example 3
[0054] Using the same starting materials as those of Example 1, the
operations of Example 1 were repeated, except that the amounts of
3.4 N aqueous sodium hydroxide solution and 0.8 mol/liter aqueous
sodium carbonate solution were changed to 461 ml and 226 ml,
respectively. The suspension formed of the hydrothermal reaction
had a pH of 11.05 (28.2.degree. C.).
[0055] The cake obtained through filtration and washing with water
was placed in 700 ml of 1.0 mol/liter aqueous solution of first
class grade ammonium carbonate and suspended under stirring,
followed by 20 hours' stirring at room temperature. The cake
obtained by filtration and washing with water was placed in a
2-liter beaker, into which 800 ml of deionized water was added to
form a suspension under stirring and heated to 80.degree. C. In a
200-ml beaker 1.2 g of sodium stearate (purity: 86%) and 150 ml of
deionized water were placed and heated to about 80.degree. C. to
form a solution. The solution was poured into the suspension under
stirring, and the system was maintained at 80.degree. C. for 30
minutes. The reaction product was recovered by filtration, washed
with water and dried at 95.degree. C. for 18 hours, and then sieved
with a 100-mesh sieve. The product was identified to be a
hydrotalcite compound by powder X-ray diffraction measurement. The
product's uranium (as U) content was not more than 5 ppb (ng/g),
average secondary particle size was 0.59 .mu.m and BET specific
surface area was 13.0 m.sup.2/g. Its chemical formula determined
from the result of chemical analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2(CO.sub.3).sub.0.15.0.53H.sub.2O.
Example 4
[0056] A 1.2 mols/liter aqueous zinc chloride solution 300 ml was
mixed with 225 ml of 0.4 mol/liter aqueous solution of industrial
grade aluminum sulfate. The mixture was placed in a 2-liter beaker,
into which 318 ml of industrial grade 3.4 N NaOH solution and 135
ml of industrial grade 0.8 mol/liter Na.sub.2CO.sub.3 solution were
poured at room temperature under vigorous stirring, followed by
about 30 minutes' agitation.
[0057] The total volume of the resultant suspension of
coprecipitation product was reduced to 700 ml by sedimentation
concentration. The suspension was transferred into a 0.98-liter
autoclave, and subjected to a hydrothermal reaction at 110.degree.
C. for 15 hours.
[0058] The resultant suspension after cooling had a pH of 10.51
(29.2.degree. C.). The cake recovered by filtration was washed with
water and put in 700 ml of a 0.5 mol/liter aqueous solution of
ammonium carbonate of first class grade, and uniformly suspended
with a stirrer, followed by 20 hours' stirring at room temperature.
Filtering the suspension, the cake recovered was washed with water
and dried at 95.degree. C. for 18 hours. The dry product was sieved
with a 100-mesh sieve, which was identified to be a hydrotalcite
compound by powder X-ray diffraction measurement and chemical
analysis. Its uranium (U) content was not more than 5 ppb [ng/g
(dry powder)], average secondary particle size was 1.2 .mu.m and
BET specific surface area was 9.9 m.sup.2/g.
[0059] The chemical formula of the product as determined by the
chemical analysis was as follows:
Zn.sub.0.67Al.sub.0.33(OH).sub.2(CO.sub.3).sub.0.17.0.5H.sub.2O.
Example 5
[0060] In the same manner to Example 1, 363 ml of bittern having a
Mg concentration of 1.5 mols/liter was mixed with 117 ml of the
aqueous solution of industrial grade aluminium sulfate having an Al
concentration of 1.03 mols/liter, and the mixture was put in a
2-liter beaker, to which 463 ml of 3.4 N sodium hydroxide solution
and 303 ml of 0.8 mol/liter industrial Na.sub.2CO.sub.3 solution
were poured at room temperature under vigorous stirring, followed
by about 30 minutes' stirring.
[0061] From the resultant suspension of the coprecipitate, 600 ml
was transferred into a 0.98-liter autoclave and subjected to a
hydrothermal reaction at 170.degree. C. for 6 hours. After
subsequent cooling, pH of the suspension was 10.56 (25.0.degree.
C.). The product was recovered by filtration, washed with water and
dried at 95.degree. C. for 18 hours, and the dry product was sieved
with a 100-mesh sieve.
[0062] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement.
[0063] Its uranium content was 13 ppb, average secondary particle
size was 0.60 .mu.m and BET specific surface area was 14
m.sup.2/g.
[0064] The product's chemical formula as determined by chemical
analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2(CO.sub.3).sub.0.15.0.54H.sub.2O.
[0065] Thus obtained hydrotalcite compound was added to 700 ml of a
1.0 mol/liter aqueous first class grade ammonium carbonate solution
under stirring and suspended, followed by 20 hours' stirring at
room temperature. The product was recovered by filtration, washed
with water and dried at 95.degree. C. for 18 hours. The dry product
was sieved with a 100-mesh sieve. The product was identified to be
a hydrotalcite compound by powder X-ray diffraction measurement.
Its uranium (as U) content was not more than 5 ppb (ng/g), average
secondary particle size was 0.60 .mu.m and BET specific surface
area was 14 m.sup.2/g. The product's chemical formula as determined
from the result of its chemical analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2(CO.sub.3).sub.0.15.0.54H.sub.2O.
Comparative Example 1
[0066] From the suspension of the coprecipitate as obtained in
Example 5, 600 ml was taken and filtered. The filter cake was
washed with water and placed in a 1-liter beaker. The cake was
suspended in deionized water and the total amount of the suspension
was adjusted to 600 ml. The suspension was transferred into a
0.98-liter autoclave and subjected to a hydrothermal reaction at
170.degree. C. for 15 hours. After the subsequent cooling, the
suspension had a pH of 9.94 (24.1.degree. C.). The product was
recovered by filtration, washed with water and dried at 95.degree.
C. for 18 hours. The dry product was sieved with a 100-mesh
sieve.
[0067] Said product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement and chemical analysis.
[0068] Its uranium content was 190 ppb (ng/g), average secondary
particle size was 0.6 .mu.m, and BET specific surface area was 19
m.sup.2/g.
[0069] The product's chemical formula as determined by chemical
analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2(CO.sub.3).sub.0.15.0.54H.sub.2O.
Example 6
[0070] Using the same starting liquid materials as those in Example
1, the copreicipitation reaction was conducted by continuous
reaction method. That is, a bittern having a Mg concentration of
1.5 mols/liter, aqueous aluminium sulfate solution of 1.03
mols/liter in concentration and 0.8 mol/liter aqueous sodium
carbonate solution were poured at the flow rates of 12.1 ml/min.,
3.92 ml/min. and 5.5 ml/min., respectively under stirring into an
approximately 1-liter reaction vessel from which the reaction
suspension could be continuously discharged. Simultaneously, 3.4 N
aqueous sodium hydroxide solution was added into the system with a
feeding pump which can control flow rate, at a flow rate so
adjusted as to maintain the pH of the reaction suspension at
10.+-.0.2. The coprecipitation reaction was continued for 3
hours.
[0071] The resultant reaction suspension was condensed by
sedimentation to a concentration of about 1.5 times, from which 700
ml was transferred into a 0.98-liter autoclave and subjected to a
hydrothermal reaction at 170.degree. C. for 6 hours, followed by
cooling, filtration and washing with water. In a 1-liter beaker,
101 g of ammonium carbonate was dissolved in deionized water and
the volume of the solution was adjusted to 700 ml, into which the
above-obtained cake after the water washing was added under
stirring and suspended, followed by 20 hours' stirring at room
temperature. Then the suspension was filtered and the recovered
cake was washed with water, transferred into a 2-liter beaker and
suspended in 1 liter of deionized water under stirring. To the
suspension 3 g of .gamma.-glycidoxypropyltrimethoxysilane (A-187,
Nippon Unicar) was poured under stirring, followed by 30 minutes'
stirring. The resultant suspension was led to a spray dryer and
dried, to provide a white dry powder. Thus obtained hydrotalcite
compound had a uranium (U) content of not more than 5 ppb (ng/g),
an average secondary particle size of 0.62 .mu.m and a BET specific
surface area of 13 m.sup.2/g.
[0072] The product's chemical formula determined through chemical
analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2
(CO.sub.3).sub.0.15.0.53H.sub.2O.
Comparative Example 2
[0073] From the reaction suspension as obtained in the continuous
coprecipitation reaction of Example 6, 700 ml was taken, filtered
and washed with water. Thus recovered cake of the coprecipitation
product was suspended in deionized water, and the volume of the
suspension was adjusted to 700 ml. The suspension was transferred
into a 0.98-liter autoclave and subjected to a hydrothermal
reaction at 170.degree. C. for 20 hours, followed by cooling,
filtration, washing with water and drying at 95.degree. C. for 18
hours. After the drying, the product was sieved with a 100-mesh
sieve. The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement and chemical analysis. Its
uranium (U) content was 200 ppb (ng/g), average secondary particle
size was 0.5 .mu.m and BET specific surface area was 13.5
m.sup.2/g.
[0074] The chemical formula of the product as determined by the
chemical analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2(CO.sub.3).sub.0.15.0.54H.sub.2O.
[0075] Ammonium carbonate of the first class grade 101 g was
dissolved in deionized water, the volume of the solution was
adjusted to 700 ml, and it was put in a 1-liter beaker. Under
stirring with an agitator, 38 g of the hydrotalcite compound as
obtained in Comparative Example 1 was added to the solution,
followed by 20 hours' stirring at room temperature. The resulting
suspension was filtered, and the recovered cake was washed with
water and dried at 95.degree. C. for 18 hours. The dry product was
sieved with a 100-mesh sieve.
[0076] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement and chemical analysis. Its
uranium (U) content was 110 ppb (ng/g), average secondary particle
size was 0.54 .mu.m and BET specific surface area was 13
m.sup.2/g.
[0077] The product's chemical formula as determined by chemical
analysis was as follows:
Mg.sub.0.69Al.sub.0.31(OH).sub.2(CO.sub.3).sub.0.15.
0.54H.sub.2O.
Example 7
[0078] A mixture was formed by blending 133 ml of the same bittern
having a Mg concentration of 1.5 mols/liter as used in Example 1,
143 ml of 0.2 mol/liter aqueous zinc sulfate solution and 143 ml of
0.4 mol/liter aqueous industrial grade aluminium sulfate solution,
which was put in a 1-liter beaker. Under vigorous stirring, 202 ml
of industrial 3.4N NaOH solution and 143 ml of industrial 0.8
mol/liter Na.sub.2CO.sub.3 solution were poured into said beaker,
followed by about 30 minutes' stirring. The suspension of the
formed coprecipitate, whose total volume was reduced to 700 ml by
sedimentation concentration, was transferred into a 0.98-liter
autoclave and subjected to a hydrothermal reaction at 150.degree.
C. for 10 hours. The resulting suspension after cooling had a pH of
9.71 (32.4.degree. C.). Filtering the suspension, the filter cake
was washed with water and put into 700 ml of 0.6 mol/liter aqueous
solution of first class grade sodium hydrogencarbonate and
uniformly suspended with a stirrer, followed by heating to
50.degree. C. and standing for 2 hours. The suspension was
subsequently filtered, and the filter cake was washed with water
and dried at 95.degree. C. for 18 hours. The dry product was sieved
with a 100-mesh sieve.
[0079] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction measurement and chemical analysis.
[0080] The uranium (U) content of the product was 5 ppb [ng/g (dry
powder)], the average secondary particle size was 0.6 .mu.m, and
BET specific surface area was 8.0 m.sup.2/g.
[0081] The chemical formula of the product as determined by the
chemical analysis was as follows:
Mg.sub.0.58Zn.sub.0.08Al.sub.0.33(OH).sub.2(CO.sub.3).sub.0.16.0.5H.sub.2O-
.
Example 8
[0082] A mixture was formed by blending 213 ml of the same bittern
having a Mg concentration of 1.5 mols/liter as used in Example 1,
266 ml of 0.2 mol/liter aqueous industrial grade aluminium sulfate
solution and 15 g of first class grade Na.sub.2SO.sub.4, which was
put in a 1-liter beaker. Under vigorous stirring 251 ml of
industrial 3.4N NaOH solution was poured into the mixture at room
temperature, followed by about 30 minutes' stirring. The resultant
suspension of the coprecipitate was transferred into a 0.98-liter
autoclave and subjected to a hydrothermal reaction at 170.degree.
C. for 12 hours. The resultant suspension after cooling had a pH of
11.08 (29.degree. C.).
[0083] The suspension was filtered, and the filter cake was washed
with water, put in 700 ml of industrial 0.5 mol/liter aqueous
Na.sub.2CO.sub.3 solution and uniformly suspended with a stirrer,
followed by 10 hours' stirring at room temperature. Thereafter the
suspension was filtered, and the filter cake was washed with water
and dried at 95.degree. C. for 18 hours.
[0084] The dry product was sieved with a 100-mesh sieve.
[0085] The product was identified to be a hydrotalcite compound by
powder X-ray diffraction analysis and chemical analysis.
[0086] The product had a uranium (U) content of 8 ppb [ng/g (dry
powder)], an average secondary particle size of 1.5 .mu.m and a BET
specific surafce area of 10.9 m.sup.2/g.
[0087] The product's chemical formula determined by the chemical
analysis was as follows:
Example 9
[0088] The dry powder of the hydrotalcite compound after the
aqueous ammonium carbonate treatment as obtained in Example 5 was
given a drying treatment in a laboratory gear oven at 270.degree.
C. for 8 hours, and whereby converted to dehydrated type
hydrotalcite compound, which had a uranium (U) content of 6 ppb
[ng/g], an average secondary particle size of 0.6 .mu.m and a BET
specific surface area of 15 m.sup.2/g. The weight decrease caused
by heating at 250.degree. C. for an hour was by 0.5%.
Example 10
[0089] The cake obtained through the steps of coprecipitation
reaction, hydrothermal reaction, the treatment with aqueous
ammonium carbonate solution, filtration and washing with water as
in Example 6 was suspended in deionized water. The suspension was
heated to 80.degree. C., and into which 5% by weight sodium
stearate solution of a prescribed amount was poured under stirring,
followed by 30 minutes' stirring. Subsequently the suspension was
filtered, and the filter cake was washed with water and dried at
95.degree. C. for 18 hours. The dry product was pulverized to
provide a surface-treated dry powder, which was further dried in a
hot-air dryer at 230.degree. C. for 20 hours. The resultant
dehydrated type hydrotalcite compound had a uranium (U) content of
8 ppb [ng/g], an average secondary particle size of 0.65 .mu.m and
a BET specific surface area of 14 m.sup.2/g. The weight decrease
caused by an hour's heating at 250.degree. C. was by 0.8%.
[0090] The diffraction sites on (003) plane [20 value] and spacing
[d(003) value] as determined by XRD measurement of the dehydrated
type hydrotalcite compounds obtained in Examples 9 and 10 are shown
below.
2 TABLE 2 Original crystallization of Dehydrated type
water-containing type Example 9 (dry product of Example 5) 2.theta.
[deg.] 13.30 11.60 d(003) [.ANG.] 6.65 7.62 Example 10 (dry product
of Example 6) 2.theta. [deg.] 13.10 11.60 d(003) [.ANG.] 6.75 7.62
(XRD measurement by CuK.alpha. rays)
[0091] As explained in the foregoing, according to the present
invention high purity (uranium content not more than 10 ppb)
hydrotalcite compounds can be produced easily and industrially.
Thus, hydrotalcite compounds suitable as additives to high
integration level semiconductor memory element-sealing resin
compositions can be provided.
* * * * *