CA1101606A - Smoke and fire retardants for halogen-containing plastic compositions - Google Patents

Abstract

Abstract of the Disclosure A solid solution of zinc and magnesium oxide and/or calcium oxide when added to a halogen-con-taining plastic composition serves as a smoke and/or fire retardant agent. This solid solution agent may be added to the plastic composition, preferably with an antimony compound.

Description

This invention relates to smoke and fire re-tardants for halogen-containing plastic compositions.
Plastic materials including plastic sheeting, synthetic fibers and the like are generally considered to be hazardous materials from the standpoint of flam-mability; and in many cases it is the practice to add various flame reta~rdants to the plastic materials to reduce flammability during combustion. Recently, however, the propensity of plastics to create large volumes of smoke, when combusted, has come to be regarded as at least as hazardous, if not more so, than its flammability.
Increasing concern with consumer safety and several tragic accidents have contributed to the recognition of smoke evolution as a significant hazard. In many instances of fire, the resulting fatalities have been due to smoke which has prevented safe evacuation of a building due to lack of visibility.
As mentioned above, extensive studies have been made in the area of flame-retardant additives for halogen-containing plastic compositions, examples of which areantimony trioxide, antimony pentoxide, antimony-silica oxide and other organic and inorganic compositions of antimony. Zinc borate has been used also as a flame retardant, but generally not as a smoke suppressant and always at relatively high levels as for example, from 3 to 8 parts per hundred parts resin since lesser amounts are ineffective as a flame retardant. In U.S. Patent No. 3,723,139, Larkin et al, discloses the addition of antimony oxide in combination with sodium antimonate to polyvinyl chloride plastics to minimize flammability and to suppress smoking.

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V.S. Patent No. 3,945,974 discloses and claims halogen-containing plastic compositions which contain various zinc salts in amoun-ts from 0.2 to 1 part calculated as zinc oxide per hundred parts of polymer resin, which are also useful as smoke suppressants.
However, when these zinc salts are used at higher concentration than that specified above, for retarding fire in addition to smoke, the zinc salts tend to degrade the plastic compositions when they are ori-`; 10 ginally prepared by conventional high temperature processes.
~inc oxide is such a salt which quickly degrades the plastic composition.
~7~6~D~describes ~2 ~-3 the use of a magnesium-zinc complex salt of an acid which is useful to impart smoke and flame resistance to the `~ plastic composition. It has been found, however, that when this complex salt composition is employed during the ~`
formation of the plastic material, bubbles and gassing can appear in the plastic material due to the release of moisture which is present in the complex salt.
It is desirable, therefore, to produce an agent which provides flame and smoke resistance to plastic material and will not significantly affect the thermal stability of the plastic material.
-~ It has now been surprisingly found that a plastic composition having exceptional flame and smoke resistance can be prepared by incorporating a solid sol-ution of zinc oxide and either magnesium oxide or calcium oxide, or a mixture of magnesium and calcium oxides, as a flame and smoke retardant in a halogen-containing plastic composition. In general, the plastic composition ;
.

contains from about 0.25~, or 0.5%, to about 10% by welght of the agent comprising a solid solution of zinc oxide and magnesium oxide and/or calcium oxide. The solid solution agent itself contains zinc oxide and an amount of mag- ;
nesium oxide and/or calcium oxide effective to provide the zinc o~ide with sufficient heat stability, i.e~, the polymer does not discolor at temperatures up to about 200~C. to 210C., to permit the processing, e.g. sheet and article formation, milling, extruding, etc., of plastic formulations using polyvinyl chloride and other halogen containing polymer systems. Generally, from about 0.1 to 10 parts of magnesium oxide and/or calcium oxide are used for each part of zinc oxide, the parts being expressed on a weight basis.
Most any type of plastic composition can be satisfactorily trea~ed with the flame and smoke retardant ` agents of this invention. Among those most commonly used are 1exible and riyid polyvinyl chloride, polyolefins such as polyethylene and polyproplene, polystyrene, poly-esters and acryIonitrile-butadiene-styrene, copolymers and the like. These plastic compositions typically contain a halogen and the expression "halogen-containing plastic composition" as used herein is intended to include both plastic compositions formed using a halogen-containing polymer such as polyvinyl chloride, and plastic compositions formed using a polymer which does not contain a halogen, such as a polyester, but to which a haloyen containing compound is added. Suitable halogen containing compounds which can be added in this manner are decarbromodiphenyl oxide and DECHLORANE~ 15, a chlorined polyethylene of Hooker Chemicals Co. containiny about 65% Cl and having 6~
.

a melting paint more than about 350C. and a particle size of 5 to 15 microns. When such compounds are used, they are generally added in amounts of ~rom about 10 to 35 wt., preferably about 12 to 25% wt of the polymer composition.
A true solution is a homogenous mixture of two or more substances which has several characteristics such as sub-division down to molecular formation, absence of settling, and no fixed proportions of the component substances. While the best known examples of solutions are cases where solids are dissolved in liquids, solutions of li~ulds in liquids and solids in solids are known.
For example, published literature includes a tentative phase diagram for a ZnO/MgO system which shows that this system possesses two solid terminal phases, the periclase solid solution based on the MgO lattice (NaCl type cubic) and the zincite solid solution based on the ZnO Wurtzite type hexagonal lattice. ( E. M. Levin, et al "Phase Diagram for Ceramists, 1969 Supplement", compiled at the NBS, 1969, published by the American Chemical Society, p. 87, Figure 2312, System MgO-ZnO, tentative and J.D.H. Donnay and H.M. Ondish, "Crystal Data", 3rd Ed., Vol. 2, Inorganic Compounds, published by the JCPOS, ZnO, H-1.5965, Data for MgO-ZnO Solid Solution.) - In accordance with this invention it has been found that ZnO/CaO and ZnOtCaO/MgO systems can also form solid solutions. Further, it has been found that such solid solutions are ef~ec-tive flame and smoke retardants, as are ZnO/MgO solid solutions.
; 30 The solid solutions of zinc oxide and magnesium oxide and/or calcium oxide of this invention are prepared !L6~;
.

. , b~ thoroughly mixing ground zinc oxide with yround magnesium oxide and/or calcium oxide inthe desired pro-portions and calsining the mixture at a temperature of at least about 500C., preferably from 800C. to 1000C, and up to about 1500C. to form the solid solution. The magnesium and/or calcium oxide and the zinc oxide may be admixed in the dry state or as a wet slurry mixture.
; Technical grade reagents may be used as purity is not a critical factor. The magnesium oxide, calcium oxide and the zinc oxide may be added as carbonates, hydroxides and other compounds which decompose to oxide compounds upon calcination. E'or example, limestone or slaked lime may be used as a source of calcium oxide.
Compositions containing different amounts of zinc oxide, magnesium oxide and calcium oxide have been calcined at different temperatures as described in Example 1 and the formation of solid solutions verified.
Precise lattice parameter measurements using x-ray diffraction have been made to verify the presen~e of solid solutions in these compositions. A Standard Norelco Diffractometer by Philips Electronics was used for obtaining the x-ray diffraction two-theta spectra~
The operating conditions were:
1) Two-theta spectrum range: 6-145

2) KVtMa: 45/35

3) Slit: 1

4) Chart Speed: 30"/hour

5) Goniometer Speed: 1/4/minute

6~ Estimated precision of line measurements :
~ 0.005.

7) Internal standard for correcting two-theta '' peak position: KCl powder crystals The data in Table l represents the lattice parameters (aO,cO~for five mixtures containing 60 wt.
% magnesium oxide and 40 wt. % zinc oxide calcined under different conaitions. The lat-tice parameters clearly indicate solid solution formation in all five samples~
The lattice expansion of both magnesium oxide and zinc oxide is in agreement with published data:
The shift in lattice parameters (aO, cO )for bqth the CaO/ZnO and ZnO/MgO/CaO systems, see Table 2, indicates that solid solution occurs during calcining of these sytems. The CaO/ZnO system contained 60 wt %
CaO and 40 wt. % ZnO and was calcined at 950 for 2.5 hours. The ZnO/MgO/CaO system contained 18 wt % ZnO, 41 wt. % ~lgO and 41 wt. % CaO and was calcined at 900C
for 4 hours.
Increasing the calcination temperature of the oxide mixture used to form the solid solution of this invention, e.g. from ~00 to 1000C., causes the specific surface area of the solid solution product to undergo a significant decrease. This is a well-known phenomenon.
However, it has now been found that the performance properties of the flame retardant smoke suppressant com-position are related to the specific surface area. Oxygen index measurements in semi-rigid polyvinyl chloride formulations, for example, r,how a corresponding decrease with decreasing surface area. To a lesser extent, the smoke reduction properties of the solid solution product are also diminished. Thus, flame xetardant~smoke 30 suppressant efficacy of the solid solutions of this in- !
vention is rela1ed to both solid solution formation and specific surface area of the particles. Table 3 ~ 7 --6~)6 :
~ .
N
O
a) ~ ~ ~ ~ o ~ I o .IJ o ~ O a) a) N a) I N
a) --~ I
~ U
O ~ O O O O
1:: ~ O C) ~ ~) a) ~ ~, ~ ~ N ~ I ~
3-o ~ ~o ~ z o z , o ~C

Q, ~-I C)~ U~ ~ O N I a,~
0~ rd ~ co O N
u ~ ~0 ~ ' ~
n~
~ , . . .
u~ .
~1 _ o In O
O ~r o o o ~
.. . ~
U ~ ~
~ t~ O
_- o o o O o o L~ o U~ o ~ ~ ~ ~0 ~ ~ I I rl E~ ., U o~
. . ~ ~o o o ~ o ~ O
o -tl aO ~, ~ ~ ~ C~ ~
a.) ~-- o o o o o ~q ~d ~ ~ ~ ~ ~ 0~ 0~ *
~U3 æ o~ ~ O 0~ ~ ~
U~ ~ ~ ~ ~ ~ ~ ~
æ O O O O O ~ ~

' *
s~
a~ I~
a) o ~ o ~ II o 1~; -- N ~) I I N
td O . ~
Ir) ~ In o ~ O ~ , O O '~' a) .,~
O ~ ~ U~
rl O ,¢ ~ O ~-1 _ ~1 I I~ a O In 1~ N I IN R.
I I. : .
a ,,, . ~ , * ~ ''' .,~
"
. ~,, . : ,~ ,, ~ ~ ~:
O P~ ~ U~
o ,¢ 1 ~1 _ I N I ~11 U~ i I N I N I
N ~rl O I ' I ' I

~} ~ a) ~ ~ .

'15', ~ ,'~
a ~ :~
(~
h ~r ~1 .C
(~I ~ O U~
: O ~4 CO ~ O
rd ~ O o r-l l l O :
o ~ ~ I 1 3 ~ -- . . . I I
.,1 ~ ~ ~r O ~
. ~ ~ O
.,1 .
0~ o ,1 S~ U~
o o o a) o ~ o : ~ ~ o : ~
~0 ~r ~ + I
O O O
. `~ r~ 0 O
.
P~ o ~ ~ ~ o ~n 3 I ~ ,1 h m 0 ~ aJ-- o U~ ~ ~ *

. . .
... .. . . . .

below presents data for a system containing 40 wt.%
zinc oxide and 60 wt. ~ magnesium oxide calcined at different temperatures, when used in a semi-rigid polyvinyl chloride formulation~
In general, in accordance with this invention, it is desired to calcine the oxide mixture at a temperature and for a time, sufficient to produce a solid solution and preferably a solid solution which is effective as a smoke and flame retardant. Accordingly, it is generally desired to calcine the mixture at a temperature and for a time effective to produce a solid solution having a specific surface area above 10~ /g, and more preferably a solid solution having a specific surface area above 16 M2/g, particularly above 30 M2/g. Temperatures above about 500C., preferably from about 800C. to about 1000C, and up to about 1500C., are suitable. Calcination times of several hours, e.g. from about 15 minutes up to about 10 hours are typical, depending upon the temperature.
Smoke measurements were carried out in the National Bureau of Standards smoke density chamber. Sheets of milled stock, 3 inch square and 40 mils thick, were used as test samples. The time required in minutes to reach 90 percent maximum density (T90) and the maximum smoke corrected for deposition on charnber walls (Dmc) were measured in order to calculate the percent smoke reduction.
Oxygen index values were determined in accordance with ASTM-D2863 method using 150 by 6.5 by 3 millimeter specimens.
The heat stability at 190C. in PVC was obtained by milling the samples with the resin and other plastic additives. The specimen was cut from the formulated . . , . -:J
milled sheet and heated at 375F, for specific time periods.
Specimens were withdrawn at given time intervals and the color of the plastic composite was compared with that of the non-additive sample. The brown discoloration was con-sidered a failure and the time (minutes) at failure was recorded and compared to a standard specimen containing no additives which failed at 45 minutes.
A wide range of ZnO/MgO, ZnO/CaO and ZnO/MgO/
CaO solid solution compositions are effective flame and smoke retardants in accordance with this invention.
Optimum properties are obtained for the ZnO/MgO system when - the composition is preferably from about 30~ ZnO and 70~
MgO to about 50 % ZnO and 50~ MgO. In the ZnO/CaO system the optimum properties are obtained when the composition is from about 50~ ZnO and 50~ CaO to about 85% ZnO and 15% CaO. Optimum properties for the ZnO/MgO/CaO system are obtained when the composition comprises from about 10%
to 60% ZnO, 10% to 60% MgO and 5% to 50% CaO.
In order to described more fully the instant invention, the following examples were presented:

40 grams of zinc oxide and 60 grams of magnesium oxide were mixed thoroughly in a blender. Both the zinc oxide and the magnesium oxide were added as powdered material.
The mixture was placed in a ceramic tube and slowly tumbled throughout the calcination step. The mixture was heated to 950C. and calcined at that temperature for 4~1/2 hours. After the calcination was completed, the calcined mixture was allowed to cool and the calcine was hammer milled through a 0.02 inch screen to break up the agglomerates which formed during the formation of the ; solid solution of the mixed oxides.
The solid solution of zinc oxide and magnesium oxide obtained was added to a standard plasticized PVC
sheet containing 1.5% antimony oxide. The amount of solid solution added was 2% (equal to 0.7% zinc oxide) and various tests were conducted using this product to show its effect-ness. The percentages are expressed on a weight basis.
The oxygen index was 37.7, the smoke reduction was 36% and the heat stability was 5 minutes less than the nonadditive control sample ( Table 4 ).
To demonstrate the effect of varying the cal-cination temperature, and thereby, the specific surface area of the solid solution, several mixtures were calcined at different temperatures. Table 3 presents the oxygen index and smoke reduction achieved using these sytems.
In these test runs the plasticized PVC sheet was prepared using the following formula:
Ingredients Parts GEON 102 EP F5~ B.F. Goodrich PVC resin inherent viscosity 1.13 ASTM D1755 class-ification GP-6-15443 Avg. mole wt./wt Avg. ~ 150,000 100 DOP (di (2-ethylhexyl)phthalate)23.5 Epoxidized Soybean Oil, Paraplex G-6 ~ 1 5 Rohm-Haas Ba-Cd Stabilizer, Mar~ ~, Argus Chemicals 2.0 Stearic Acid 0.5 Antimony Trioxide 1.5 ~ZnO-MgO and/or CaO As indicated In this example 989 grams of magnesium oxide and 598 grams of zinc oxide were added to 6 liters of deionized - :, , . :;, ~ : : , .

- ~0~16~6 a) ~ 0 .. ~ ,~
u~ ~ ~ ~r :
O u~
., o ~ U~ ~ .,.
~rl O O ~D
~, 0 a s~
U~ ~

~ ., X
~ ~ o ~ ~ ~ :~
u~ ~ ~ ~r ~ ~ .
d? ~
~ .

CO ,, ~ ~ ::, H
O ~ o~
. ,~

~.
~ r~
p:
m ~ ~ 0~ 00CO CO
E~ t) ~ '~
~ ~;:

~ .
g : :.
. ~.
:-:
: ~:~ o O O O
o ~ o In o o .,~ I~ ~ O
0 a~
E~

o ~ o~ o~
~ 5 o o o O o . ~ o~ ~ ~0 W C~ ~ W
U~
0 ~3 o o o o , - - . . .: -. . : : ..

water. The slurry contained 21% solids. A~ter stirring at room temperature for one half hour, the solids were filtered under vacuum. The filter cake was dried in an oven at 120C. for 18 hours. The dried filter cake was broken up and calcined in a revolving ceramic tube. After reaching 900C., the charge was calcined at that temp-erature for 4-1/2 hours. Again, after cooling, the solid solution product was hammer milled through a 0.02 inch screen to break up agglomerates.
The operational details and the results of the testing procedures are recorded in Table 4.
CONTROLS ~-C
In order to show the superiority of using a solid solution of magnesium oxide and zinc oxide in com-parison to employing uncalcined mixture o~ magnesium oxide and zinc oxide, a control run ( Control A ) was made in which an uncalcined mixture of the two oxides was employed in the same ratio as that used in Example 1.
In this particular run, when the mixture was added to the standard PVC product, the heat stability was very poor, i.e. 20 minutes less than the PVC standard containing no additive. This poor heat stability is equal to that obtained when zinc oxide alone ( Control B ) is used as the additive without the presence of magnesium oxide.
Another control run ( Control C ) was prepared in which the magnesium oxide and the zinc oxide were calcined separately ( i.e. 8 hrs. at 900C.) and the two calcined oxides were then mixed. ~hen this mixture ~as used in the plastic sheet, the heat stability was good but the ~ smoke reduction was very poor. The operational details and results obtained are also recorded in the Table - ~ 14 -:

, ~a~

: along with those of Controls A and B.

The solid solution flame and smoke retardant agent of the instant invention was also compared ~qith the magnesium-zinc sulfate complex salt prepared according C~p/~ ~/c~o~ ~0,~
to U ~. applicat-ion ~e~i~t~ ~3~ . It was found that although the heat stability, the oxygen index and the smoke reduction properties were all satisfactory, the complex salt when incorporated into the plastic gassed and formed bubbles which is undesirableO The solid solution agent of the instant invention, however, does not gas nor form bubbles when employed in the plastic material.
In these runs various zinc oxide-magnesium oxide and/or calcium oxide solid solutions were prepared by dry blending the indicated compositions and calcining at the time and temperature shown in Table 4 and used to treat the standard PVC product as follows:
Example No. % MgO ~ CaO ;
3 . 83.8 4 73.5 4.8 - :

7 35 35 ~:
Again, the results are recorded in the Table.
.
It should be noted that the test results were satisfactory ~:
in all of the examples except Example 5 where the smoke reduction was unsatisfactory ( MgO content low ).

In these runs various zinc and magnesium compounds were used as starting materials. In Examples 8 - 10, zinc - 15 ~

,, , L6q~

o .' ,( ~ ~ ~D ~ ~ ~ a~ ~ o o ~ o ~ a~

a) x ~ a) 1~ ~ o a~ ~r o ~ ~ o O H r~(~ ~) ~ ~ ~7 ~rl ~) ~ ~ ~1 .
_~
rn ~
~ U~ ~) u~ ~ ~n ~1 L~ o o o o o In O O O
(~ ~ ~d . , tq '~ -,~
_ ~C) O O O OOOOOOOOO
k Lo o o o o o o o Irl o o_ ~ ~ a~
.~
_ .
,~ a~ u, ~ ~i ~1 ~ ~ N
~1 r~ 5 E~-- -1 ~1 o o o~
~r U I I I I I ~ ~.
X
~ 0~ ~ O
~ o U~
o\o 1 1 1 1 1 1 1 1 D ~) I I I I N .
: r`
O ~ 0~ ~ O O
~ O ~ O O r~ ~ I Ln O O O ~ O
o~

t` ~ U~ ~ ~ ~ ~
O
~: O 1-- 0 0 0 ~D ~ Il O O O O O L~ ~
o\o tJ' O
N N N
_ _ ~ ~ ~ U .-1 Q, ~d ~ ~ ,~ ., a)a~ h h ~ rd ~
,Q Q U ~ ~ X
O
U El ~1 h o U ~1 :~ O ~ ~ ~ S
O O ~ ~ ~
. ---- ~ z u~ ~ n Z 0 0~ 0 ~0~ Z g,,O~O~O~
t~
a~
~1 ~ ~ O ~ 1~i~l O O
Q~ O O h ~(D O O O ~ O O O O O U Z u~
x c;~ ~1 ~ x~ 1~ ~ ~ ~ ,~ dO

r~
r~

~ .,.,.. . ~ .

and magnesium compounds were precipitated as hydroxides from aqueous solutions by the addition of sodium hydroxide.
These hydroxides were in turn calcined to form the solid solutions of magnesium oxide and zinc oxide. In Example

8 the chloride salts were used as the starting materials while the nitrates were used in Example 9 and zinc and magnesium sulfate were employed in Example 10.
In Example 11, zinc and magnesium intermetallic alloy (Mg2Zn) was used as the starting material; and during calcination, zinc oxide and magnesium oxide solid solution was formed. In all of these runs satisfactory results were obtained as shown in Table 4. ~ -~
Although the flame and smoke resistance of a plastic composition is improved when the zinc oxide and magnesium oxide and/or calcium oxide solid solution particles are present in the composition, it has been found that further improvements are obtained when antimony trioxide is also present in the plastic composition.
Mixtures, therefore, of the solid solution of the zinc, magnesium and/or càlcium oxides and antimony trioxicle have been prepared. The amount of antimony trioxide added to the particles of the solid solution of zinc, magnesium and/or calcium oxide is generally from about 0.05 to 15 parts, preferably from about 0.1 to 10 parts, of antimony trioxide for each part of the solid solution present in the mixture ( parts expressed on a weight basis), It has also been discovered that in some cases the flame and/or smo~e resistance may be somewhat increased when various amounts of other agents are also added in addition to the zinc oxide and magnesium oxide and/or calcium oxide solid solutions. These agents includeamong others zinc borate, aluminum trihydrate, molybdenum trioxide and other commonly used flame and smoke retardant additives.
From the above description and by the e~amples presented, it has clearly been shown that a halogen containing plastic composition containing a small percentage of the solid solution of zinc oxide and magnesium oxide and/
or calcium oxide produces a highly desirable flame and smoke 10 resistant plastic material. By using the solid solution -~
agents of the instant invention as flame and smoke resistant agents, superior results are obtained over those which employ zinc oxide alone, mixtures of zinc oxide and magnesium oxide and complex compositions of magnesium oxide and zinc salts of the acid.
To further illustrate the flame and smoke retardant properties of the solid solutions of this in-vention, a number of additional tests were made using other plastic compositions.

A 40/60 ZnO/MgO solid solution prepared by the method of Example 1 was incorporated into a rigid polyvinyl chloride (PVC) pipe formulation and the following results were observed:
-~ The Formulation was, in parts by weight:
(A) ~B) (C) (1) Geon 103 EP-F76~ B.F. Good 100.0 100.0 100.0 rich PVC resin inherent vis-cosity 0.92 ASTM D-1755 classi-fication 6P-4-16043 avg. mole wt/wt avg 91,000 30 (2) Thiotin Stabilizer~ M&T
Chemicals 0.5 0.5 0.5 (3) 165F Paraffin Wax 1.0 1.0 1.0 (A) (B) (C) (4~ C~lcium Stearate 0.7 0.70.7 (5) Plastiflow PO ~, N.L. 0.150.15 0.15 Industries fle~ible/
rigid lubricant, modified polyethylene wax specific gravity @ 25C. 0.96 melting point,ll6C.
(6) Calcium Carbo~ate, 2.5 2.5 2.5 Omyalite 90-IQ~ !
(7) TiO2, Titanox 2071~ 1.0 1.0 1.0 (8) Sb2O3 2.0

(9) ZnO/MgO 0 0 2.0 48.7 58.466.9 NBS SMOKE DENSITY, 40 MIL STOCKS ! FLAMING CONDITIONS
Dm ( Per gram, corrected ) 50.0 38.6 32.7 % Reduction 0 23 35%

The flame and smoke retardant composition of the instant invention is very effective when used in con-junction with phosphate plasticizers. When a 40/60 ZnO/MgO solid solution prepared by the method of Example 1 was incorporated into a PVC wire and cable formulation using phosphate plasticizers, the following results were obtained.
~ Formulation: ( parts by weight ) (A) (B) (C) (D) (E) (F) (1) Geon 103 EP B.~.~ 100 ~ same same --------Goodrich PVC resin inherent viscosity 1.02 ASTM D-1755 classification GP-5-15443 avg. mole wt/
wt avg 100,000 6~i (A) (B) (C) (D) (E) (F) (2) Tribase Exl~, N.L. 5 ~ - same same-----------Industries lead silicate sulfate %PbO 64.0 specific gravity 3.9 (3) SP #33 Clay~ Kaolin 15 ----- same same ------------Clay, from Freeport, Georgia electrical grade (4) Calcium Carbonate Antomite~ 15 ------same same-------------(5) Plastiflow POP~0.2 --~--same same------------(6) Mixed Dialkyl 52 52 26 26 26 26 Phthalate ~7) Tricresyl Phosphate - 26 26 (8) Alkyl Diaryl Phos-phate - - - - 26 26 (9) Sb2O3 - 5

(10) ZnO/MgO - 4 - 4 - 4 OXYGEN IN~EX, ASTM D-2863A
24.9 30.6 28.3 28.527.1 27.5 NBS SMOKE DENSIT~, 40 MIL STOCKS, FLAMING CONDITIONS

DM ( per gram,50.1 35.9 66.1 39.654~6 32.4 corrected ) % Reduction 0 28 0 40 0 41 Very low levels of the flame and smoke retardant composition of the instant invention are effective for suppressing smoke in high impact polystyrene (HIPS).
When a 40/60 ZnO/MgO solid solution prepared by the method of Example 1 was incorporated into a HIPS formulation the following results were obtained:

Formulation : (parts by weight) (A) (B) (C) (1) HIPS U.C. 6500 85 -- same --6~6 .
(A) (~)(C) (2) Decabromo~ Diphenyl Oxide, DOW-300BA 10 ~same ----(3)Plastiflow POP~ 0.5 ---- same ----(5) ZnO/MgO 0 0.25 0.75 NBS SMOKE DENSITY, 25 MIL STOCKS, FLAMING CONDITIONS
..... . .
Dm (per gram, corrected) 118 108 95 % Reduction 0 9 20 UL 94, Vertical Burning Test V-0 V-0 V-0 Low levels of the flame and smoke retardant composition of the instant invention are effective for ;~
suppressing smoke in polypropylene (PP). When a 40/60 ZnO/MgO solid solution prepared by the method of Example 1 was incorporated into a PP formulation the following results were obtained:
Formulation: ( parts by weight ) (A) (B)(C) 20 (1) PP Pro-Fax 642 ~ Hercules polypropylene resin, nominal melt flow 12 @ 230C. 6.5 60 60 60 (2) Dechlorane 515~ Hooker Chemi- 27 27 27 cals, % Cl-65, particle size 5-15 microns, melting point >350C. :
(3) Sb2O3 13 12 10 (4) ZnO/MgO 0 1 3 NBS SMOKE DENSITY, 25 MIL STOCKS, FLAMING CONDITIONS

Dm ( per gram, corrected ) 43.7 37.7 34.9 % Reduction 0 14 20 The flame and smoke retardant composition of the instant invention is very effective when used in acrylonitrile-6~

butadiene-styrene (ABS) resins. When a 40/60 ZnO/MgO
solid solution prepared by the method of Example 1 was incorporated into an ABS formulation the following results were obtained:
Formulation : (parts by weight) (~) (B) (C) (D) (1) Sb2O3 12 3 12.3 4 4 ~' (2) ZnO/MgO 0 3 3 (3) ABS Cycolac TD 1001~, Borg Warner 61.3 61.3 82 82 (4) Lectro 60XL~, NL Industries, lead chlorosilicate complex, ~ PbO-64 2 2 2 2 (5) Dechlorane 51 ~ 24.4 24.4 0 0 (6) Citex BC-26~ Cities Service tricyclic bromine complex, ~ Br-29, % Cl-40 0 0 12 12 OXYGEN INDEX, ASTM D-2863A
26.0 29.625.0 24.2 NBS SMOKE DENSITY~ 15 MIL STOCKS, FLAMING CONDITIONS
Dm (per gram, corrected~ 84.8 78.8 11791.8 ~ Reduction 0 7 0 22 The flame and smoke retardant composition of the instant invention is very effective when used in conjunction with antimony trioxide or alumina trihydrate (ATH) in semi-rigid polyvinyl chloride (PVC). When a 40/60 ZnO/MgO solid solution prepared by the method of Example 1 was incorporatedinto a PVC formulation with Sb2O3 or ATH the following results were obtained:
Formulation : ( parts by weight ) (A) (B) (C) (D) (E) (F) (1) PVC Geon 102 EP F ~ 100 ------same same ----~----L61~6 (A) tE3) (C) (D) (E) (F) (2) Deundecyl phth~cate 30 ~ - same same ------(3) Dythal~, N.L Indus- 7 -- ------ same same ------tries, dibasic lead stabilizer % PbO-79.8.
specific gravity 4.5 (4) Acrawax C~), Glycol 0.3 -------- same same -~
Chemicals, fatty diamide synthetic wax (5) DS-207~), N.L Indus- 0.3 -------- same same ------tries, dibasic ~ead sterate, % PbO-553, specific gravity 10 (6) Sb2O3 2 __ 2 -- --(7) ZnO/MgO -- -- 2 2 -- 2 (8) ATH -- -- -- -- 2018 OXYGEN INDEX, ASTM D-2863A
27.9 32.128.134.1 30.1 30.8 NBS SMOKE DENSITY, 40 MIL 5TOCKS, FLAMING CONDITIONS

DM ( per gram, corrected ) 73 75.7 39.3 40.1 53.6 39.9 % Reduction 0 (+3) 46 45 27 46 Low levels of the flame and smoke retardant composition of the instant invention are effective for suppressing smoke in halogenated polyesters (HPE). When a 40/60 Zno /MgO solid solution prepared by the method of Example 1 was incorporated into HPE formulation the following results were obtained:
Formulation: ( parts by weight ) (A) (B) (1) HPE Hetron 92 A~), Ashland 100 100 Chemicals halogenated poly-ester, properties @ 25C.
acid nunber 18, color (gardner) 5 maximum, viscosity (Brookfield) #2 spindle 50 Rpm 400 #2 spindle 5 Rpm 1100 (A) (B) (2) MEK Peroxide (3) Sb2O3 5 5 (4) ZnO/MgO 0 OXYGEN INDEX, ASTM D-2863A

43.3 43.4 NBS SMOKE DENSITY, 65 MIL STOCKS, FLAMING CONDITIONS
_ Dm ( per gram, corrected ) 57.6 44.5 % Reduction 0 23 It has been found that the flame and smoke ; retardant composition of the instant invention can function alone or synergistically with antimony trioxide. When a 40/60 ZnO/MgO solid solution prepared by the method of Example 1 was used in conjunction with Sb2O3 in a semi-rigid polyvinyl chloride (PVC) formulation the improvement in flame retardancy as measured by the Oxygen Index Test was greater than expected, assuming the effect of Sb2O3 and ZnO/MgO was additive. This is shown in the Table below:
The formulation used was that of example 1, in parts by weight.
(1) PVC 100 (2) DOP 23.5 (3) EPOX Oil l.S
(4) Ba-Cd Stabilizer 2 (5) Stearic Acid 0.5 (6) Additive - Sb2O3 (x), ZnO/MgO ty) x + y=2 ;~ 30 :;
- 24 - ;
.'' , PARTS BY WEIGHT ADDITIVE
~ Dm*(per grams 2 3 40/60 ZnO/MgO OI corrected ) % Reduction ... .. ___ .- -- -2 0 32.939~0 0 1.5 0.5 34.6 ~
l 1 34.521.8 44 0 2 33.719.0 51 *NBS Smoke Density, 40 mil stock, non-flaming conditions From the above description and by the examples presented, it has clearly been shown that a halogen containing plastic composition containing a small percentage of the solid solution ofzinc oxide and magnesium oxide and/or calcium oxide produces a highly desirable flame and smoke resistant plas-tic material~ By using the solid -solution agents of the instant invention as a flame and smoke resistant agents, superior results are obtained over those which employ zinc oxide alone, mixtures of zinc oxide and magnesium oxide and complex compositions of magnesium oxide and zinc salts of an acid~
The solid solutions of zinc oxide and magnesium oxide and/or calcium oxide of the instant invention are easily prepared and economical to employ.
While this invention has been described and illustrated b~ the examples shown, it is not intended to be strictly limited thereto, and other variations and :~ modifications may be employed within the scope of the following claims.

Claims (28)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A flame and smoke resistant halogen-containing plastic composition, said composition containing therein from 0.5% to 10% of a solid solution of zinc oxide and an oxide selected from the group consisting of magnesium oxide, calcium oxide and mixtures thereof, the amount of magnesium oxide and calcium oxide present in said solid solution being from .1 to 10 parts for each part of zinc oxide, all of the percentages and parts expressed on a weight basis.

2. Composition according to Claim 1 in which the composition contains a solid solution of zinc oxide and magnesium oxide.

3. Composition according to Claim 1 in which the composition contains a solid solution of zinc oxide and calcium oxide.

4. Composition according to Claim 1 in which the composition contains a solid solution of zinc oxide, magnesium oxide and calcium oxide.

5. Method of preparing a flame and smoke resistant halogen-containing plastic composition which comprises incorporating in said plastic compositions from 0.5% to 10%
of a solid solution of zinc oxide and an oxide selected from the group consisting of magnesium oxide, calcium oxide and mixtures thereof, the amount of magnesium oxide and oxide and calcium oxide present in said solution being from about .1 to about 10 parts for each part of zinc oxide, all of the percentages and parts expressed on a weight basis.

6. Method according to Claim 5 in which said solid solution employed contains zinc oxide and magnesium oxide.

7. Method according to Claim 5 in which said solid solution employed contains zinc oxide and calcium oxide.

8. Method according to Claim 5 in which said solid solution employed contains zinc oxide, magnesium oxide and calcium oxide.

9. A flame and smoke resistant agent for halogen-containing plastic compositions, said agent comprising a mixture of antimony trioxide and a solid solution of zinc oxide and magnesium oxide and/or calcium oxide in which there are from 0.1 to 10 parts of antimony trioxide for each part of the solid solution present in said mixture, the parts expressed on a weight basis.

10. A solid solution of zinc oxide and calcium oxide.

11. A solid solution of zinc oxide, calcium oxide and magnesium oxide.

12. A flame and smoke retardant composition comprising a solid solution of zinc oxide, and at least one other oxide selected from the group consisting of calcium oxide and a mixture of calcium oxide and magnesium oxide, wherein the weight percents of said zinc oxide and said other oxide are selected such that said composition has flame and smoke retardant properties.

13. The composition of Claim 12 containing about 0.1 to 10 parts by weight of said other oxide for each part by weight of zinc oxide.

14. The composition of Claim 13 wherein the solid solution consists of zinc oxide and calcium oxide.

15. The composition of Claim 14 containing from about 50 weight percent zinc oxide and 50 weight percent calcium oxide to about 85 weight percent zinc oxide and 15 weight percent calcium oxide.

16. The composition of Claim 13 wherein the solid solution consists of zinc oxide and magnesium oxide.

17. The composition of Claim 16 containing from about 30 weight percent zinc oxide and 70 weight percent magnesium oxide to about 50 weight percent zinc oxide and 50 weight percent magnesium oxide.

18. The composition of Claim 13 wherein the solid solution consists of zinc oxide, magnesium oxide and calcium oxide.

19. The composition of Claim 18 containing from about 10 weight percent to 60 weight percent zinc oxide and 5 weight percent to 50 weight percent calcium oxide.

20. The composition of Claim 12 wherein the solid solution has a specific surface area of above about 10 M2/g.

21. The composition of Claim 13 wherein the solid solution has a specific surface area above 16 M2/g.

22. A flame and smoke resistant halogen-con-taining plastic composition, said composition containing therein from 0.25% to 10% of a solid solution of zinc oxide and an oxide selected from the group consisting of magnesium oxide, calcium oxide and mixtures thereof, the amount of magnesium oxide and calcium oxide present in said solid solution being effective to provide the zinc oxide with sufficient heat stability to permit processing of the plastic composition at temperatures up to about 200°C., all of the percentages and parts expressed on a weight basis.

23. A method of preparing a flame and smoke resistant halogen-containing plastic composition which comprises incorporating in said plastic composition from 0.25% to 10% of a solid solution of zinc oxide and an oxide selected from the group consisting of magnesium oxide, calcium oxide and mixtures thereof, the amount of magnesium oxide and calcium oxide present in said solid solution being effective to provide the zinc oxide with sufficient heat stability to permit processing of the plastic composition at temperatures up to about 200°C., all of the percentages and parts expressed on a weight basis.

24. A method of producing a flame and smoke retardant for use in halogen containing plastic compositions com-prising calcining zinc oxide and another oxide selected from the group consisting of magnesium oxide, calcium oxide, and mixtures thereof at a temperature and for a time effective to produce a solid solution having flame and smoke retardant properties, said another oxide being present in an amount of about 0.1 to 10 parts by weight for each part of zinc oxide.

25. The method of Claim 24 wherein the temperature and time are sufficient to produce a solid solution having specific surface area above about 10 m52/g.

26. The method of Claim 24 wherein the temperature is above about 500°C.

27. The method of Claim 24 wherein the temperature is from about 500°C. to about 1000°C.

28. A flame and smoke retardant composition comprising a solid solution of zinc oxide and at least one other oxide selected from the group consisting of calcium oxide, magnesium oxide and mixtures thereof, wherein said com-position contains from about 0.1 to 10 parts by weight of said other oxide for each part by weight of zinc oxide, and wherein the specific surface area of said solid solution is equal to or greater than 10 m2/g.