U.S. patent application number 10/303784 was filed with the patent office on 2004-04-29 for method for preparing melamine salt of bis-(pentaerythritol phosphate) phosphoric acid.
This patent application is currently assigned to Chung-Shan Institute of Science & Technology. Invention is credited to Ma, Chong, Peng, Yuen-Hsin, Wu, Tseng-Rong.
Application Number | 20040082782 10/303784 |
Document ID | / |
Family ID | 32105833 |
Filed Date | 2004-04-29 |
United States Patent
Application |
20040082782 |
Kind Code |
A1 |
Ma, Chong ; et al. |
April 29, 2004 |
METHOD FOR PREPARING MELAMINE SALT OF BIS-(PENTAERYTHRITOL
PHOSPHATE) PHOSPHORIC ACID
Abstract
Bis-(pentaerythritol phosphate) phosphoric acid is prepared by
mechanochemical synthesis including ball milling a mixture
containing P.sub.2O.sub.5, pentaerythritol, an alkyl benzene having
one or two C1-C5 alkyl groups, and a metal halide catalyst, in a
ball mill as a reactor and at a temperature of room temperature to
150.degree. C. Melamine is then reacted with the resulting
bis-(pentaerythritol phosphate) phosphoric acid to form a product
of melamine salt thereof.
Inventors: |
Ma, Chong; (Tao-Yuan,
TW) ; Wu, Tseng-Rong; (Tao-Yuan, TW) ; Peng,
Yuen-Hsin; (Tao-Yuan, TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 SLATERS LANE
FOURTH FLOOR
ALEXANDRIA
VA
22314
|
Assignee: |
Chung-Shan Institute of Science
& Technology
P.O. Box 90008, Lung-Tan
Tao-Yuan
TW
|
Family ID: |
32105833 |
Appl. No.: |
10/303784 |
Filed: |
November 26, 2002 |
Current U.S.
Class: |
544/200 |
Current CPC
Class: |
C07D 251/54 20130101;
C07F 9/65748 20130101 |
Class at
Publication: |
544/200 |
International
Class: |
C07F 009/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2002 |
TW |
91124590 |
Claims
1. A method for preparing a melamine salt of bis-(pentaerythritol
phosphate) phosphoric acid by a mechanochemical synthesis, which
comprises the following steps: (a) ball milling a mixture
comprising P.sub.2O.sub.5, pentaerythritol, an alkyl benzene having
one or two C1-C5 alkyl groups, and a metal halide catalyst in a
ball mill reactor at a temperature of room temperature to
150.degree. C. to form bis-(pentaerythritol phosphate) phosphoric
acid; and (b) ball milling or mechanically mixing a mixture
comprising melamine, bis-(pentaerythritol phosphate) phosphoric
acid and a solvent at room temperature to 100.degree. C., wherein
said solvent is water, acetonitrile, or a mixture of the solvent in
step (a) with acetonitrile.
2. The method as claimed in claim 1, wherein said alkyl benzene is
toluene, and said metal halide catalyst has a chemical formula of
MX.sub.2, wherein M is Mg, Zn or Al, and X is Cl or Br.
3. The method as claimed in claim 2, wherein said metal halide
catalyst is MgCl.sub.2.
4. The method as claimed in claim 1, wherein a molar ratio of
pentaerythritol to P.sub.2O.sub.5 in said mixture of Step (a) is
4:3 to 1:2.
5. The method as claimed in claim 1, wherein a weight ratio of said
catalyst to pentaerythritol in said mixture of Step (a) is 1:99 to
5:95.
6. The method as claimed in claim 1, wherein said ball milling in
Step (a) is carried out for 4-20 hours.
7. The method as claimed in claim 1, wherein said temperature in
Step (a) is 90-105.degree. C.
8. The method as claimed in claim 2, wherein said toluene in Step
(a) is pre-heated to a temperature of 90-100.degree. C. prior to
being added to said ball mill reactor; and said ball milling in
Step (a) is carried out without heating.
9. The method as claimed in claim 1, wherein said solvent in Step
(b) is pre-heated to 50-100.degree. C., and said mixture in step
(b) is ball milled in said ball mill reactor without heating.
10. The method as claimed in claim 9, wherein said solvent is a
mixture of toluene with acetonitrile pre-heated to 50-80.degree.
C., acetonitrile pre-heated to 80.degree. C., or boiling water.
11. The method as claimed in claim 10, wherein said solvent is
boiling water.
Description
BACKGROUND OF THE INVENTION
[0001] U.S. Pat. No. 4,454,064 discloses a method for preparing
pentaerythritol phosphate, which comprises reacting pentaerythritol
with POCl.sub.3 in dioxane solvent at 75-125.degree. C. The
pentaerythritol phosphate thus prepared can be used as an
intermediate for synthesizing a polyurethane flame retardant and a
plasticizer. This preparation method will also generate HCl gas and
a residual solution of excessive POCl.sub.3.
[0002] U.S. Pat. No. 4,478,998 discloses a synthesis of an
amino-s-triazine salt of a phosphoric acid having the following
formula: 1
[0003] when X and X' in the formula are amino, said salt is
melamine salt of bis-(pentaerythritol phosphate) phosphoric acid.
The synthesized amino salt can be used as a flame retardant
additive for certain polymer compositions. In Example 1 of said
patent, melamine reacts with acid chloride of bis-(pentaerythritol
phosphate) phosphoric acid in water to obtain said melamine salt.
Said acid chloride of bis-(pentaerythritol phosphate) phosphoric
acid is synthesized through the following reaction formula: 2
[0004] HCl gas and a residual solution of excessive POCl.sub.3 will
also be generated in the abovementioned reaction.
SUMMARY OF THE INVENTION
[0005] The present invention provides a method for preparing a
melamine salt of bis-(pentaerythritol phosphate) phosphoric acid,
which comprises preparing bis-(pentaerythritol phosphate)
phosphoric acid, and reacting melamine with the obtained
bis-(pentaerythritol phosphate) phosphoric acid to form a melamine
salt thereof. The preparation of bis-(pentaerythritol phosphate)
phosphoric acid according to the present invention has the
following characteristics:
[0006] 1. The method uses P.sub.2O.sub.5 as a reactant.
[0007] 2. The method uses a mechanochemical synthesis and uses a
ball mill as a reactor.
[0008] 3. The method uses an alkyl benzene, such as toluene or
xylene, as a solvent. The alkyl benzene may have one or two
identical or different alkyls having 1 to 5 carbons.
[0009] 4. The solvent used in the method is at room temperature or
pre-heated to 50-150.degree. C.
[0010] 5. The method uses metal halide MX.sub.2, such as MgCl.sub.2
etc., as a catalyst, wherein M=Mg, Zn, or Al; and X=Cl, or Br. The
weight ratio of the catalyst to pentaerythritol is 1:99 to
5:95.
[0011] Compared to the conventional process, the present invention
has the following three advantages: (a) no generation of waste gas
of HCl; (b) free of a waste aqueous solution generated from
neutralization of HCl waste gas; and (c) avoiding handling of a
residue solution containing unreacted POCl.sub.3.
[0012] The reaction between melamine and bis-(pentaerythritol
phosphate) phosphoric acid according to the present invention can
be carried out in a ball mill or a conventional mechanical
agitation reactor, which comprises ball-milling or mechanically
mixing a mixture of melamine, bis-(pentaerythritol phosphate)
phosphoric acid, and a solvent at room temperature to 100.degree.
C. Suitable solvents include (but not limited to) water,
acetonitrile (CH.sub.3CN), and a mixture of the solvent used in the
preparation of bis-(pentaerythritol phosphate) phosphoric acid with
acetonitrile. Preferably, said solvent is pre-heated to
50-100.degree. C. and thus there is no heating while ball milling
said mixture. More preferably, said solvent is a mixture of toluene
with acenonitrile preheated to 50-80.degree. C., acetonitrile that
has been pre-heated to 80.degree. C. or boiling water, most
preferably is boiling water.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0013] The present invention discloses a method for preparing
melamine salt of bis-(pentaerythritol phosphate) phosphoric acid,
which comprises preparing bis-(pentaerythritol phosphate)
phosphoric acid, and reacting melamine with the obtained
bis-(pentaerythritol phosphate) phosphoric acid to form a melamine
salt thereof. Several factors affecting the synthesis of said
bis-(pentaerythritol phosphate) phosphoric acid are discussed in
the following:
[0014] 1. Study on the Reaction Solvent
[0015] The molecular structure unit of phosphorus pentoxide is
P.sub.4O.sub.10, usually represented by P.sub.2O.sub.5. Phosphorus
pentoxide is a very strong dehydration agent, and is liable to
react with water to form phosphoric acid.
P.sub.2O.sub.5+3H.sub.2O.fwdarw.2H.sub.3PO.sub.4
[0016] Furthermore, it can grab H.sub.2O from reactant molecules to
form metaphosphoric acid and related inorganic or organic material,
e.g.
P.sub.2O.sub.5+H.sub.2SO.sub.4.fwdarw.SO.sub.3+4HPO.sub.3
P.sub.4O.sub.10+H.sub.2N--C(O)--C(O)--NH.sub.2.fwdarw.NC--CN+4HPO.sub.3
P.sub.2O.sub.5+CH2.dbd.C(CH.sub.3)--C(O)--OH+CH.sub.3OH.fwdarw.CH.sub.2.db-
d.C(CH3)--C(O)OCH.sub.3+2HPO.sub.3
[0017] P.sub.2O.sub.5 reacts with ethyl ether to form triethyl
phosphate:
P.sub.2O.sub.5+3(C.sub.2H.sub.5).sub.2O.fwdarw.2(C.sub.2H.sub.5O).sub.3P.d-
bd.O
[0018] The strong reactivity of phosphorus pentoxide makes the
selection of the reaction solvent greatly restricted. The inventors
of the present invention have tried using a solvent such as
n-hexane, diethyl phosphate, and toluene, etc. for performing the
reaction, in which the reaction of using n-hexane as a solvent is
not ideal and has an extremely low yield. When diethyl phosphate is
used as a solvent, the reaction has a very good yield. However,
since the properties of diethyl phosphate are too close to the
properties of the product bis-(pentaerythritol phosphate)
phosphoric acid, they are difficult to be separated. Therefore,
toluene is selected as a reaction solvent.
[0019] Pentaerythritol can be dissolved in diethyl phosphate
solvent, therefore, after addition of P.sub.2O.sub.5, the reaction
can take place at a reaction temperature of 90.degree. C. While not
dissolving in toluene, pentaerythritol will turn into a molten
state when the temperature rises to 90.degree. C. and can react
with P.sub.2O.sub.5. Since pentaerythritol in its molten state has
an extremely high viscosity and is difficult to agitate, the
reaction yield is not high. Therefore, how to achieve an ideal
agitation for pentaerythritol to have a sufficient contact with
P.sub.2O.sub.5 is a key factor in increasing the yield.
Pentaerythritol does not dissolve at the boiling point of n-hexane
at 68.degree. C. and has no change in state at this temperature,
this could be a reason why it does not react with P.sub.2O.sub.5 in
n-hexane.
[0020] 2. Study on Reaction Temperature
[0021] Pentaerythritol does not react with P.sub.2O.sub.5 in
toluene solvent at a temperature lower than 70.degree. C. under
traditional stirring process. When the temperature increases to
90.degree. C., pentaerythritol can undergo a phosphate
esterification reaction. The reaction time is about 10 hours. When
the temperature rises to 105.degree. C., the reaction time can be
reduced to 6 hours.
[0022] 3. Effects of the Particle Size of Pentaerythritol
[0023] The reaction yield and purity can be increased when, prior
to the reaction, pentaerythritol is ground in toluene in a ball
mill.
[0024] 4. Ball Mill Process
[0025] Based on the above studies 1.about.3, the key factors
affecting the method of the present invention include: heating of
the solvent, material with a fine particle size, and complete
mixing in the reaction. Therefore, a ball mill is considered as a
reactor to achieve a complete grinding, mixing and thermal
insulation in the reaction. A suitable reaction time is 4-20
hours.
[0026] 5. Formation of Phosphoric Acid in the Reaction
[0027] When 2 moles of pentaerythritol reacts with 1.5 mole of
P.sub.2O.sub.5, 1 mole of bis-(pentaerythritol phosphate)
phosphoric acid and 3.5 moles of water will be generated. Since 3
moles of water will react with 1 mole of P.sub.2O.sub.5 to from 2
moles of phosphoric acid, and a consumption of P.sub.2O.sub.5
occurs. Therefore, an excessive amount of P.sub.2O.sub.5 should be
used for all the pentaerythritol phosphate alcohol to be converted
to bis-(pentaerythritol phosphate) phosphoric acid. A suitable mole
ratio of pentaerythritol to P.sub.2O.sub.5 is 4:3 to 1:2.
[0028] The reaction between melamine and bis-(pentaerythritol
phosphate) phosphoric acid according to the present invention can
be carried out in said ball mill or a conventional mechanical
agitation reactor, preferably in a ball mill. The reaction can be
carried out using acetonitrile or water as the solvent. According
to the present invention, when the conventional mechanical mixing
is used and acetonitrile is used as a solvent, the reaction can be
completed in 6 hours by reflux. In the ball mill process where
acetonitrile which is pre-heated to 80.degree. C. is used, the
reaction time is 7.5 hours. In the ball mill process, if toluene is
still used as a solvent in the reaction for forming melamine salt
after the preparation of bis-(pentaerythritol phosphate) phosphoric
acid, the result is poor. After the completion of the preparation
of bis-(pentaerythritol phosphate) phosphoric acid in the ball mill
process, if the original solvent (400 ml) is retained and another
100 ml of acetonitrile, which is pre-heated to 80.degree. C., is
added as a solvent in the reaction for forming melamine salt, the
reaction can be carried out smoothly and the reaction time is also
7.5 hours. Furthermore, if the remaining solvent is poured out and
boiling water is added as a solvent in the reaction for forming
melamine salt, the reaction time can be greatly reduced to 15-60
minutes. The obtained melamine salt of bis-(pentaerythritol
phosphate) phosphoric acid has a good heat resistance, only about
10.about.20% of which will be decomposed at 200.about.300.degree.
C., and about 40% of which will remain at a temperature exceeding
600.degree. C.
[0029] The present invention uses P.sub.2O.sub.5 to replace
POCl.sub.3, and a mechanochemical synthesis process to overcome
lack of a suitable solvent. Thus, the present invention has the
following advantages: no formation of hydrochloric acid, no waste
solution, environmentally friendly, without the need of heating in
the reaction, high yield, increased purity, and capability of
recycling solvent.
[0030] The reaction formulas involved in the following Examples are
shown in the following: 3
[0031] Since P.sub.2O.sub.5 will be consumed by the 7/2 moles of
water simultaneously formed during the reaction, an excessive
amount of P.sub.2O.sub.5 is needed in the reaction. Therefore, a
small amount of H.sub.3PO.sub.4 will be also formed together with
the product as shown in the following reaction:
P.sub.2O.sub.5+3H.sub.2O.fwdarw.2H.sub.3PO.sub.4
[0032] Since P.sub.2O.sub.5 is very hygroscopic, the feeding must
be carried out by using an enclosed feeding device for solid
feed.
EXAMPLE 1
Ball Mill Process for Synthesis of bis-(pentaerythritol phosphate)
Phosphoric Acid (abbreviated as b-PEPAP)
[0033] A ball mill reactor with one liter capacity was used and
ceramic balls with a diameter of 2 cm were used.
[0034] 13.6 g (0.1 mol) of pentaerythritol and 18.88 g (0.133mol)
of P.sub.2O.sub.5were used. 400 ml of toluene was used and was
pre-heated to 90.about.100.degree. C. After drying, the ball mill
reactor was added with the pre-heated solvent, and sequentially
added with pentaerythritol, P.sub.2O.sub.5, and 0.4 g of
MgCl.sub.2, followed by ceramic balls. The ball mill reactor was
then closed and rotated. The reaction was carried out for 6 hours.
After the reaction, the liquid portion in the ball mill reactor was
poured out, and the remaining product mixture was subjected to a
reduced pressure to evaporate the solvent contained therein.
.sup.31P-NMR spectrum of the product mixture was taken and the
integration areas of bis-(pentaerythritol phosphate) phosphoric
acid (b-PEPAP) and phosphoric acid therein were calculated, thereby
obtaining the phosphor content ratios thereof, wherein the relative
phosphor content ratio of b-PEPAP to phosphoric value is 56 to 44.
The phosphor content ratio was used to calculate the purity of
b-PEPAP in the product mixture, which is 65 wt %.
[0035] .sup.31P-NMR was used to identify the main components in the
product mixture obtained by the mechanochemical synthesis ball mill
process in Example 1, wherein DMSO d.sub.6 was used as a solvent.
The results indicate that the resonance at 0.4 ppm was phosphoric
acid, -0.3 ppm was P--OH, -6.4 ppm was P on the bicyclo ring
(pentaerythritol phosphate alcohol, as shown in Example 1 of EP 0
578 318 A1).
Preparation of Melamine Salt of bis-(pentaerythritol phosphate)
Phosphoric Acid (abbreviated as b-PEPAP.MEL)
EXAMPLE 2
[0036] The product mixture of Example 1 was retained in the ball
mill reactor, after the liquid portion was poured out. 21 g (0.166
mol) of melamine was poured into the ball mill, and 300 ml of
acetonitrile which was pre-heated to 80.degree. C. was added. The
ball mill reactor was closed and rotated for 6 hours. .sup.31P-NMR
spectrum of a sample of the reaction solution taken from the ball
mill reactor showed no existence of .sup.31p peak, which indicated
that b-PEPAP and phosphoric acid were all consumed. The product
b-PEPAP.MEL and the by-product melamine salt of phosphoric acid
were all insoluble in acetonitrile solvent. The reaction was
completed with a conversion rate of 100%.
EXAMPLE 3
[0037] The procedures in Example 2 were repeated except that the
liquid portion of the reaction mixture in the ball mill reactor was
not poured out, 100 ml of acetonitrile which was pre-heated to
80.degree. C. was added instead of 300 ml, and the ball mill
reactor was for 7.5 hours. The conversion rate was 100%.
EXAMPLE 4
[0038] The procedures in Example 2 were repeated except that 350 ml
of pre-heated boiling water was added instead of acetonitrile, and
the ball mill reactor was rotated for 15 minutes only. .sup.31P-NMR
spectrum of a sample of the reaction solution taken from the ball
mill reactor showed no existence of .sup.31P peak. The reaction was
completed with a conversion rate of 100%.
[0039] The melamine salt of bis-(pentaerythritol phosphate)
phosphoric acid obtained in Example 2 to Example 4 had an average
particle size of 6-8 .mu.m, and the particle size distributions
thereof showed that 91% of the particles were smaller than 14.4
.mu.m. Their IR spectrums were were substantially the same and
contained the following major characteristic absorption
wavelength:
[0040] 900.about.1060 (broad): P--O--CH.sub.2R (Vibration)
[0041] 1164.about.1185 (strong): P.dbd.O (Vibration)
[0042] 1430.about.1548 (medium): primary amine salt, bending
[0043] 1650 (wide, strong): O.dbd.P--OH
[0044] 3100 (strong): amine salt, primary
[0045] 3300 (medium): primary amine
* * * * *