Organic phosphorus compounds and flame-retarded resin compositions containing the same

Organic phosphorus compounds of the formula (I): ##STR1## wherein R.sub.1 and R.sub.2 are, the same or different, a C.sub.1-8 straight chain or branched chain alkyl group, an optionally substituted C.sub.6-12 aryl group; and A represents a bond, a lower alkylene group or --(OCH.sub.2 CH.sub.2).sub.n -- group, (n is an integer of 1 to 5), which are useful as flame-retardants.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to novel organic phosphorus compounds of 
non-halogen type and flame-retarded resin compositions containing the same 
which are excellent in flame-retardant properties and heat resistance. 
2. Description of the Related Art 
Organic polymers such as thermoplastic resins (e.g., polypropylene, 
polystyrene and acrylonitrile-butadienestyrene (ABS) resins) and 
thermosetting resins (e.g., polyurethane and phenol resins) are available 
at relatively low cost and have excellent properties such as easy molding. 
Such organic polymers are widely used in all kinds of commodities 
including electronic components and automobile components. However, these 
organic polymers are flammable. Once they are involved in fire, they are 
readily burned and lost. A fire of cable causes great damage to our 
society. A law has recently been enacted which provides that these organic 
polymers shall be flame-retardant when used in products for daily use such 
as electric products, automobile interior decoration components and fiber 
products. For example, in the United States, there are the UL standards 
for electric apparatus and MVSS-302 Flame-Retardant Rule for automobiles. 
As a known method for giving flame-retardant properties to organic 
polymers, a flame-retardant is added to organic polymers when preparing a 
molded product. As the flame-retardants, there are inorganic compounds, 
organic phosphorus compounds, organic halogen compounds and organic 
phosphorus compounds containing halogen. Of the above compounds, organic 
halogen compounds and organic phosphorus compounds containing halogen 
exhibit excellent flame-retardant effect. However, these compounds 
containing halogen are pyrolyzed in the process of molding resins and 
produce hydrogen halide, which corrodes molds and causes resins to be 
deteriorated and colored. Furthermore, such compounds adversely affect our 
working environment. Still furthermore, the compounds generate toxic gas, 
such as hydrogen halide, which is toxic to human bodies. 
Typical flame-retardants which do not contain halogens are inorganic 
compounds such as magnesium hydroxide. However, since these inorganic 
compounds are inferior in flame-retardant effect, it is necessary to add a 
large amount to achieve sufficient flame-retardant effect. Thus such 
flame-retardants have a drawback of allowing resins to be deprived of 
their inherent properties. 
Halogen-free organic phosphorus compounds are generally used as 
flame-retardant having a relatively favorable flame-retardant effect. 
Aromatic phosphorus compounds such as triphenyl phosphate (TPP), tricresyl 
phosphate (TCP) and cresyl diphenylphosphate (CDP), which are typical 
organic phosphorus compounds, are used as flame retardants for each kind 
of engineering plastics, such as phenol resin, epoxy resin and 
polyurethane resin or the like. 
However, triphenyl phosphate can hardly give flame-retardant properties to 
resins because it contains phosphorus at a low ratio. Triphenyl phosphate 
is usually used together with a halogen type flame-retardant. Furthermore, 
when triphenyl phosphate is singly used, it must be used in large amounts. 
This will impair various physical properties of resins and readily cause 
resins to be colored and deteriorated. 
In addition, German Patent No. 3004184C2 discloses compounds of formula (A) 
as a flame-retardant which is added to an organic polymer such as 
polyolefin, polypropylene, polystyrene, ABS and polyurethane. 
##STR2## 
However, one of the main disadvantages of using these compounds lies in 
that a large amount thereof needs to be added to an organic polymer to 
give sufficient flame-retardant properties to resins because these 
compounds contain phosphorus at a low ratio, thereby resulting in inferior 
physical properties of resins. It is further noted that when R'.sub.1 to 
R'.sub.5 in the above formula (A) are methyl groups, the compounds have a 
low heat resistance, which leads to a disadvantage of causing resins to be 
colored and deteriorated in the process of molding. 
In recent years, the development of plastics having high functional 
properties, such as engineering plastics and super-engineering plastics 
are in progress. Since these plastics need a high molding temperature, a 
flame-retardant is also required to be sufficiently heat resistant. As a 
known method for improving the heat resistance of flame-retardants, an 
anti-oxidant such as hindered-phenol compounds, sulfur compounds and amine 
compounds together with flame-retardant is added to organic polymers. 
However, even when such anti-oxidants are added to organic polymers, for 
example, together with the organic phosphorus compounds as mentioned 
above, coloring of resins cannot be avoided at 200.degree. C. or more. 
SUMMARY OF THE INVENTION 
The present invention has been made to solve the above drawbacks of the 
prior art and aims to provide a novel compound which can be used as a 
flame-retardant for various kinds of resins, having excellent 
flame-retardant properties and heat resistance and good properties which 
do not deteriorate or corrode the resins when molded owing to the absence 
of halogens, and further to provide a flame-retarded resin composition 
containing the above compound and a resin which is excellent in heat 
resistance and flame-retardant properties, and can form molded articles 
without causing dripping of molten resins. 
Accordingly, the present invention provides an organic phosphorus compound 
of the formula (I) (hereinafter referred to as Compound (I)): 
##STR3## 
wherein R.sub.1 and R.sub.2 are, the same or different, a C.sub.1-8 
straight chain or branched chain alkyl group, or an optionally substituted 
C.sub.6-12 aryl group; A represents a bond, a lower alkylene group or 
--(OCH.sub.2 CH.sub.2).sub.n -- group (n is an integer of 1 to 5) and a 
flame-retarded resin composition comprising Compound (I) and a resin.

DESCRIPTION OF PREFERRED EMBODIMENTS 
In the above formula (I), examples of the C.sub.1-8 alkyl groups 
represented by R.sub.1 and R.sub.2 include methyl, ethyl, propyl, 
isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl, 2-ethylhexyl, 
n-octyl, and isooctyl groups. In particular, methyl or ethyl groups are 
preferable. 
Examples of the optionally substituted C.sub.6-12 aryl groups represented 
by R.sub.1 and R.sub.2 include phenyl, cresyl, xylyl and naphthyl groups. 
In particular, phenyl group is preferable. 
Such aryl groups may be substituted with one to three C.sub.1-3 alkyl 
groups such as methyl, ethyl and propyl. 
Examples of the lower alkylene groups represented by A include C.sub.1-4 
alkylene groups such as --CH.sub.2 --, --CH.sub.2 CH.sub.2 --, and 
--CH.sub.2 CH.sub.2 CH.sub.2 -- groups, among which --CH.sub.2 CH.sub.2 -- 
group is preferable. 
Examples of --(OCH.sub.2 CH.sub.2).sub.n -- groups represented by A are 
--OCH.sub.2 CH.sub.2 -- group (n is 1) and --OCH.sub.2 CH.sub.2 OCH.sub.2 
CH.sub.2 -- group (n is 2), among which the former is preferable. 
Compound (I) of the present invention can be obtained by reacting a 
compound of the formula (III) (hereinafter referred to as Compound (III)): 
##STR4## 
wherein R.sub.1 and R.sub.2 are as described above and X is a halogen 
atom, with a compound of the formula (IV) (hereinafter referred to as 
Compound (IV)): 
EQU HO(CH.sub.2 CH.sub.2 O).sub.n H (IV) 
wherein n is as described above for formula (I) or a compound of the 
formula (V) (hereinafter referred to as Compound (V)): 
EQU HO(CH.sub.2).sub.m OH (V) 
wherein m is an integer of 2 to 8 in an organic solvent in the presence of 
an organic base. 
In the above reaction, the organic base functions as an acid acceptor. 
Examples of organic bases include triethylamine, tributylamine, pyridine 
and dimethylaminopyridine. These bases can be used singly or as a mixture 
of two or more kinds. The amount of base to be used is 2 to 2.5 moles, 
preferably 2.05 to 2.2 moles, for one mole of Compound (IV). 
The reaction can be conducted in an inert organic solvent such as benzene, 
toluene, dichloroethane, dioxane or acetonitrile, or the like. 
Compound (III) is used in 2 to 2.5 moles, preferably 2 to 2.1 moles, for 
one mole of Compound (IV). 
The reaction can be conducted at 25.degree. to 80.degree. C., preferably 
30.degree. to 70.degree. C. for about two to ten hours, preferably about 
five to seven hours. 
The reaction product can be isolated and purified by means of known methods 
such as solvent extraction, change of acidity or alkalinity, salting out, 
crystallization and recrystallization. 
Of the material compounds used in the process for preparing Compound (I), 
Compound (III) can be obtained by reacting phosphorus oxyhalide with a 
diol compound such as neopentyl glycol or the like. 
In addition, Compound (IV) is ethylene glycol when n is 1 and diethylene 
glycol when n is 2. Other examples of Compound (IV) are triethylene glycol 
and tetraethylene glycol. 
Compound (V) is ethylene glycol in case of m being 2, propylene glycol for 
m being 3 and buthylene glycol for m being 4. 
Compound (I) having desired phosphorus content and molecular weight can be 
prepared by suitably selecting the kinds and amounts of the starting 
Compounds (III) and (IV) in the above method. The resulting organic 
phosphorus Compound (I) thus obtained can be used as a flame-retardant 
singly or as a mixture of two or more kinds. 
The flame-retarded resin composition of the present invention comprises a 
resin and the above organic phosphorus Compound (I) optionally together 
with an anti-oxidant and other additives. Examples of such additives 
include halogen type flame-retardants, inorganic flame-retardants, 
antioxidants, fillers and lubricants. 
The kind and amount of Compound (I) to be used is appropriately determined 
by the degree of flame-retardant properties required therein. The amount 
of Compound (I) to be used is 0.1 to 100 parts by weight, preferably 5 to 
50 parts by weight, for 100 parts by weight of the resin. The resin, the 
organic phosphorus compound and the above additive, when needed, are 
headed and molded in accordance with the known method to give a 
flame-retardant molded article. Compound (I) can be added to monomers to 
be used in the preparation of a resin with block polymerization, a 
reaction mixture at the end of the block polymerization, or the resin to 
be subjected to molding, thereby providing flame-retardant properties 
thereof. 
Examples of the above resins include thermoplastic resins such as 
chlorinated polyethylene, polyethylene, polypropylene, polybutadiene, 
polystyrene, impact-resistant polystyrene, polyvinyl chloride, ACS resin, 
AS resin, ABS resin, polyphenylene oxide, polymethylmetacrylate, 
polyamide, polyester and polycarbonate; and thermosetting resins such as 
polyurethane, phenolic resin, melamine resin and urea resin and 
unsaturated polyester. The above resins may be used singly or as a 
mixture. 
The flame-retarded resin composition of the present invention may contain 
an anti-oxidant when required. Examples thereof are a hydroquinone 
compound of the formula (II): 
##STR5## 
wherein R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are, the same or different, 
a hydrogen atom or a C.sub.1-14 straight chain or branched chain alkyl 
group, and known trivalent organic phosphorus compounds. 
Examples of the hydroquinone compounds (II) include hydroquinone, 
2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone and 
octylhydroquinone. Preferred hydroquinone compounds having excellent heat 
resistance are 2,5-di-tert-amylhydroquinone and 
2,5-di-tert-butylhydroquinone. 
Examples of the above trivalent organic compounds include 
triphenylphosphite, tris(nonylphenyl)phosphite, diphenylisodecylphosphite, 
bis(2,4-di-tert-butylphenyl)pentaerythritoldiphosphite, 
tetrakis(2,4-tert-butylphenyl)4,4-diphenylenephosphonite. 
For such resins as denatured polyphenylene oxide (PPO), polystyrene or ABS 
resin, Compound (I) can be used together with an inorganic 
flame-retardant, for example, magnesium hydroxide or antimony trioxide. 
For polyurethane foam, Compound (I) can be also used together with a 
non-halogen type compound, such as melamine or urea. 
The present invention will be detailed with respect to the following 
examples which are not intended to be limiting. In the following examples, 
parts are designated in weights and temperatures in centigrades unless 
otherwise indicated. 
EXAMPLE 1 
Into a four necked flask equipped with a stirrer, a thermometer and a 
condenser with water scrubber was put 104 parts (1 mole) of neopentyl 
glycol and 100 parts of toluene, followed by addition of 153.5 parts (1 
mole) of phosphorus oxychloride at 50.degree. C. in an hour. The reaction 
was continued for 4 hours to complete dehydrochlorination. To the reaction 
solution was added 150 g of toluene, to which 31 parts of ethylene glycol 
(0.5 mole) and 200 parts of dioxane were added at 20.degree. C. and 
further a mixture of 111 parts of triethylamine and 0.5 part of 
dimethylaminopyridine was dropwise added at 50.degree. C. for about 2 
hours. Then the mixture was raised to 80.degree. C. and maintained for 5 
hours to complete the reaction. The precipitated object compound and the 
amine hydrochloride were collected by filtration and washed with methanol 
to remove the amine hydrochloride. The residue was dried in vacuo at 
100.degree. C. to obtain 155g (yield: 87%) of white powder crystals. The 
chemical structure of the crystals is as follows (referred to as Compound 
1), mp 164.degree. to 166.degree. C. 
##STR6## 
The elemental analysis of Compound 1 (C.sub.12 H.sub.24 O.sub.8 P.sub.2) is 
shown in Table 1. The NMR spectrum is also shown in FIG. 1. 
EXAMPLE 2 
White crystalline powders having the following chemical structure (referred 
to Compound 2) were prepared in the same manner as Example 1 except that 
51 parts of diethylene glycol were used in place of 31 parts of ethylene 
glycol. The yield was 161 g (80%). mp 116.degree. C. 
The elemental analysis of Compound 2 (C.sub.14 H.sub.28 O.sub.9 P.sub.2) is 
shown in Table 1. FIG. 2 shows the NMR spectrum of Compound 2. 
##STR7## 
EXAMPLE 3 
White crystalline powders having the following structure (referred to 
Compound 3) were prepared in the same manner as Example 1 except that 45 
parts of 1,4-butanediol was used in place of 31 parts of ethylene glycol. 
mp 127.degree. C. 
The elemental analysis of Compound 3 (C.sub.14 H.sub.28 O.sub.8 P.sub.2) is 
shown in Table 1. 
##STR8## 
TABLE 1 
__________________________________________________________________________ 
Yield Melting 
Elemental analysis 
Exp. 
ratio 
point 
Theoretical value (%) 
Measured value (%) 
No. (%) (.degree.C.) 
C H O P C H O P 
__________________________________________________________________________ 
1 87 165 40.22 
6.70 
35.75 
17.32 
39.86 
6.61 
37.12 
17.76 
2 80 116 41.79 
6.97 
35.82 
15.42 
40.86 
6.52 
36.24 
16.08 
3 85 127 43.52 
7.25 
33.16 
16.06 
42.29 
7.08 
25.82 
16.62 
__________________________________________________________________________ 
Besides, even if the organic phosphorus compounds in accordance with the 
invention may contain a by-product, such by-product would not affect heat 
resistance and flame-retardant properties when they are used as a 
flame-retardant. 
The following examples 4 to 6, show the results for performance evaluation 
on the above Compounds 1 and 2 and the conventional flame-retardant 
compounds. 
##STR9## 
EXAMPLE 4 
Flame-Retarded Resin Composition 
______________________________________ 
Polyol (manufactured by Mitsui Toatsu 
100 parts 
Chemicals, Inc., Trade name of MN-3050 ONE) 
Isocyanate (manufactured by Mitsui Toatsu 
55.1 parts 
Chemicals, Inc., Trade name of TDI 80/20) 
Polyol silicone oil (manufactured by Nihon 
1.2 parts 
Yunika Co., Ltd., Trade name of L-520) 
Tin catalyst 0.25 part 
Amine catalyst 0.15 part 
Water 4.5 parts 
Methylene chloride 3.0 parts 
Flame-retardant compound (predetermined 
amount shown 
in Table 1) 
______________________________________ 
The above ingredients were used to prepare a soft urethane foam in 
accordance with the one-shot method as follows. 
Firstly, the polyol, silicone oil, catalysts, methylene chloride, water and 
flame-retardant compound were blended and homogenously mixed for a minute 
with a stirrer of 3000 rpm. Then the isocyanate was added thereto, stirred 
for 5 to 7 seconds at 3000 rpm and quickly poured into a box with a 
square-shaped cross section. Immediate foaming occurred to give the 
maximum volume several minutes later. The product was cured for 30 minutes 
in a furnace at 120.degree. C. The resulting foam has white and soft open 
cells. 
Each of the resulting foams was cut to obtain a specimen, which was 
subjected to a burning test using MVSS-302. Furthermore a fresh specimen 
was treated for 3 minutes in a microwave oven (500 W) followed by heating 
for 2 hours at 140.degree. C. The specimen was observed for change of 
color (presence or absence of scorch). 
Results are shown in Table 2 and Table 3. In the item "scorch" in Table 3, 
mark "o" designates almost no change of color while mark "x" is colored in 
brown. 
TABLE 2 
______________________________________ 
Average Average 
burning burning 
Flame- distance distance 
retardant 
(pts.) (mm) (pts.) 
(mm) (pts.) 
scorch 
______________________________________ 
Compd. 1 
8 NB 32.0 10 NB 22.8 
20 .smallcircle. 
Compd. 2 
8 NB 37.0 10 NB 26.6 
20 .smallcircle. 
Compd. A 
8 SE 39.6 10 NB 27.8 
20 x 
Compd. B 
8 -- 10 SE 75.9 
20 .smallcircle. 
Compd. C 
8 SE 76.0 10 SE 52.0 
20 .smallcircle. 
Compd. D 
8 NB 31.0 10 NB 21.6 
20 x 
none -- burned .smallcircle. 
______________________________________ 
NB: Non Burn 
SE: Self Extinguish 
TABLE 3 
______________________________________ 
Flame- 
retardant (pts.) scorch 
______________________________________ 
Compound 1 20 .smallcircle. 
Compound 2 20 .smallcircle. 
Compound A 20 x 
Compound B 20 .smallcircle. 
Compound C 20 .smallcircle. 
Compound D 20 x 
none .smallcircle. 
______________________________________ 
As apparent from Table 2 and Table 3, the organic phosphorus compounds of 
the present invention give better flame-retardant properties and do not 
occur any scorch, in comparison with the conventional halogen 
flame-retardant compounds. Even keeping the organic phosphorus compounds 
of the present invention at 80.degree. C. for 14 days, they did not change 
the flame-retardant effect. 
EXAMPLE 5 
To 100 parts of a mixture of impact-resistant polystyrene/PPO resin (45/55) 
was added 10 parts of the organic phosphorus compound described in Table 
4. The mixture was uniformly blended for about 15 minutes using an V type 
blender with 10 L, and converted into pellets using an extruding machine 
having internal diameter of 40 mm. A predetermined specimen was prepared 
from the pellets using a molding machine with a capacity of 4 ounces. 
The flame-retardant properties of the specimen were evaluated in accordance 
with the test method stipulated in UL-94. Five test pieces for each 
specimen were twice measured for a time from firing to extinguishment. 
Total times for two measurements are used as burning time and the times 
are averaged for five test pieces. Then the heat deformation temperature 
was measured in accordance with D648 in ASTM standard. Juicing phenomena 
of the surface of the molded article were also determined. Table 4 shows 
the result thereof. 
TABLE 4 
______________________________________ 
Flame- Average burning 
Heat deformation 
retardant 
time (sec) temperature (.degree.C.) 
Juicing 
______________________________________ 
Compd. 1 
35 95.2 none 
Compd. 2 
39 94.3 none 
Compd. E 
unextinguished 
81.5 present 
Compd. F 
45 86.0 somewhat 
present 
______________________________________ 
EXAMPLE 6 
To 100 parts of ABS resin (Sebian-V manufactured by Daicel Chemical 
Industry, Ltd., Japan) was added 10 parts of the organic phosphorus 
compound described in Table 5, 5 parts of tetrabromobisphenol A, and 2.5 
parts of Sb.sub.2 O.sub.3. The mixture was uniformly stirred for about 15 
minutes using a V type blender with 10 L, and converted into pellets using 
an extruding machine having internal diameter of 40 mm. The pellets were 
molded into predetermined specimen with a 4 ounce molding machine. 
The flame-retardant properties of the specimen were evaluated in accordance 
with the test method stipulated in UL-94. Five test pieces for each 
specimen were twice measured for a time from firing to extinguishment. 
Total times for two measurements are used as burning time and the times 
are averaged for five test pieces. Then the heat deformation temperature 
was measured in accordance with D648 in ASTM standard. Juicing phenomena 
of the surface of the molded article were also determined. Table 5 shows 
the results thereof. 
TABLE 5 
______________________________________ 
Average Heat 
Flame- burning time 
deformation 
retardant 
(sec) temperature (.degree.C.) 
Juicing 
______________________________________ 
Compd. 1 
7 92.0 none 
Compd. 2 
11 86.9 none 
Compd. E 
20 75.3 present 
Compd. F 
14 80.2 somewhat present 
______________________________________ 
The novel organic phosphorus Compound (I) of the present invention, when 
mixed with various kinds of resins, can impart excellent flame-retardant 
properties to the resin. The organic phosphorus compounds (I) have 
low-volatility and excellent heat resistant properties, and are free of 
causing resin to be colored and deteriorated by pyrolysis in the molding 
process. Additionally, they hardly impair the physical properties of the 
resin. In addition, the flame-retarded resin composition can provide a 
molded product that fails to generate dripping of molded resin when 
burned.