GB1589821A - Smoke and fire retardants for halogen-containing plastic compositions - Google Patents

Description

(54) SMOKE AND FIRE RETARDANTS FOR HALOGEN-CONTAINING PLASTIC COMPOSITIONS (71) We, NL INDUSTRIES INC., a company organised under the laws of the States of New Jersey, United States of America, of 1230 Avenue of the Americas, New York, New York 10020, U.S.A. do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following -statement:- Plastic materials including plastic sheeting, synthetic fibers and the like are generally considered to be hazardous materials from the standpoint of flammability; and in many cases it is the practice to add various flame retardants 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 are antimony 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.

U.S. Patent No. 3,945,974 discloses and claims halogen-containing plastic compositions which contain various zinc salts in amounts 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 originally prepared by conventional high temperature processes. Zinc oxide is such a salt which quickly degrades the plastic composition.

Our earlier Specification No. 1523531 and the corresponding U.S. Patent No. 3996142 disclose and claim 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.

We have now surprisingly found that halogen containing plastic compositions having exceptional flame and smoke resistance can be prepared by incorporating therein a solid solution of zinc oxide, magnesium oxide and/or calcium oxide. The present invention accordingly provides a flame and smoke retardant halogen containing plastic composition (as hereinafter defined) containing, as a flame and smoke retardant a solid solution of zinc oxide, magnesium oxide and/or calcium oxide. The invention includes a method of making a flame and smoke retardant halogen-containing plastic composition (as hereinafter defined) which comprises incorporating into a halogen-containing plastic composition a solid solution of zinc oxide and magnesium oxide and/or calcium oxide.

In general, the plastic composition contains from about 0.25%, or 0.5%, to about 10% by weight of the flame and smoke retardant. The solid solution itself contains zinc oxide and an amount of magnesium oxide and/or calcium oxide effective to provide the zinc oxide with sufficient heat stability, i.e., the polymer does not discolor at temperatures up to about 200"C. to 210 C., to permit the processing, e.g. sheet and article formation, milling and extruding 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.

Certain of the solid solutions used as flame and smoke retardants in the halogen containing plastic compositions of the invention are believed to be novel per se. The invention accordingly includes: a) a solid solution of zinc oxide, calcium oxide and magnesium oxide containing 0.1 to 10 parts by weight of calcium and magnesium oxide per part by weight zinc oxide and preferably comprising 10 to 60% by weight of zinc oxide, 5 to 50% by weight of calcium oxide and 10 to 60% by weight of magnesium oxide, the solid solution having a specific surface area of at least 10 M3/g; and b) a solid solution of zinc oxide and calcium oxide containing 0.1 to 10 parts by weight of calcium oxide per part by weight zinc oxide and preferably comprising from 50 to 85% by weight of zinc oxide and from 50 to 15% by weight of calcium oxide, the solid solution having a specific surface area of at least 10 M /g.

Most types of plastic composition can be satisfactorily treated to make them flame and smoke retardant according to this invention. Among those most commonly used are flexible and rigid polyvinyl chloride, polyolefins, such as polyethylene and polyproplene, polystyrene, polyesters and acrylonitrile-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 halogen containing compound is added.Suitable halogen containing compounds which can be added in this manner are decarbromodiphenyl oxide and DECHLORANE 515, a chlorined polyethylene of Hooker Chemicals Co. containing about 65% Cl and having a melting point more than about 350do. and a particle size of 5 to 15 microns. When such compounds are used, they are generally added in amounts of from 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 liquids 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 (NaCI 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", complied 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 ZnO/CaO/MgO systems can also form solid solutions. Further, it has been found that such solid solutions are effective flame and smoke retardants, as are ZnO/MgO solid solutions.

The solid solutions for zinc oxide and magnesium oxide and/or calcium oxide of or for use in this invention can be prepared by thoroughly mixing ground zinc oxide with ground magnesium oxide and/or calcium oxide in the desired proportions and calcining the mixture typically at a temperature of at least about 500"C., preferably from 800"C. to 10000C, and up to about 1500"C. 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. For 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 presence 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) KV/Ma: 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:KCI powder crystals The data in Table 1 represents the lattice parameters (aO,cO) for five mixtures containing 60 wt.% magnesium oxide and 40 wt.% zinc oxide calcined under different conditions. The lattice 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: TABLE 1 Sample Calcination MgO ZnO Description Temp ( C) Time (hrs) Lattice Parameter* Lattice Parameter (wt. %) ao( ) ao( ) co( ) 40ZnO/60MgO 900 4.5 4.22791 Not Computed 40ZnO/60MgO 950 0.50 4.21854 Not Computed 40ZnO/60MgO 1000 0.25 4.22048 Not Computed 40ZnO/60MgO 950 0.50 4.21703 3.25102 5.20902 40ZnO/60MgO 900 8 4.21228 Not Computed pure MgO --- --- 4.213 pure ZnO --- --- ------ 3.249 5.205 * Based on the precision of two-theta angle measurements, the equivalent precision of a0 is + 0.00006 .

TABLE 2 Sample CaO MgO ZnO Description Lattice Parameter* Lattice Parameter* Lattice Parameter* (wt. %) aO (A) aO (A) aO (A) cO (A) 60CaO/40ZnO 4.80894 ----- 3.25113 5.20674 18ZnO/41MgO/41CaO 4.80901 4.22157 Not Computed pure CaO 4.8105 ---pure MgO ---- 4.213 pure ZnO ---- ---- 3.249 5.205 * Based on the precision of two-theta angle measurements, the equivalent precision of a0 is + 0.00006 .

The shift in lattice parameters (aO,cO) for both the CaO/ZnO and ZnO/MgO/CaO systems, see Table 2, indicates that solid solution occurs during calcining of these systems.

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. % MgO and 41 wt. % CaO and was calcined at 900 C for 4 hours.

Increasing the calcination temperature of the oxide mixture used to form the solid solution of this invention, e.g. from 500 to 1000 C., 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 composition are related to the specific surface area. Oxygen index measurements in semi-rigid polyvinyl chloride formulations, for example, show 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 retardant/smoke suppressant efficacy of the solid solutions of this invention is related to both solid solution formation and specific surface area of the particles. Table 3 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.

TABLE 3 Specific Surface Sample Calcination Calcination % Smoke Area Description Temp ("C) Time (hrs) OI Reduction M2/g 40ZnO/60MgO 500 8 39.8 40 50.3002 40ZnO/60MgO 750 8 38.1 41 30.7351 40ZnO/60MgO 900 8 36.2 33 16.1514 40ZnO/6()MgO 1,000 8 34.4 34 3.6814 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 10M2/g, and more preferably a solid solution having a specific surface area above 16 M2/g, particularly above 30 M2/g.Temperatures above about 500"C, preferably from about 800"C to about 1000"C, and up to about 1500"C, 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 chamber 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 ny 6.5 by 3 millimeter specimens.

The heat stability at 1900C. in PVC was obtained by milling the samples with the resin and other plastic additives. The specimen was cut from the formulated milled sheet and heated at 3750F 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 considered 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 arc obtained when the composition comprises from about 10% to 60% ZnO, 10% to 60% MgO and 5% to 50% CaO.

In order to describe more fully the present invention, the following examples were presented: Example I 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 950"C. and calcined at the temperature for 41/2 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 effectiveness. 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 calcination 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 systems.

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 100 viscosity 1.13 ASTM D1755 classification GP 6- 15443 LAvg. mole wt./wt Avg. - 150,000 DOP (di (2-ethylhexyl) phthalate) 23.5 Epoxidized Soybean Oil, Paraplex G-62, Rohm-Haas 1.5 Ba-Cd Stabilizer, Mark M, Argus Chemicals 2.0 Stearic Acid 0.5 Antimony Trioxide 1.5 ZnO-MgO and/or CaO As indicated (The words "Geon" and "Paraplex" are Registered Trade Marks".) Example 2 In this example 989 grams of magnesium oxide and 598 grams of zinc oxide were added to 6 liters of deionized water. The slurry contained 21% solids. After stirring at room temperature for one half hour, the solids were filtered under vacuum. The filter cake was dried in an oven at 1200C for 18 hours.The dried filter cake was broken up and calcined in a revolving ceramic tube. After reaching 900"C., the charge was calcined at that temperature for 41/2 hours. Again, after cooling, the solid solution product was hammer milled through a 0.02 inch screen to break up the agglomerates.

The operational details and the results of the testing procedures are recorded in Table 4.

Controls A-C In order to show the superiority of using a solid solution of magnesium oxide and zinc oxide in comparison to employing uncalcined mixture of 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 900 C.) and the two calcined oxides were then mixed. When this mixture was 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 along with those of Controls A and B.

TABLE 4 Calcination Heat Stab.

Time Temp. (Min. Less Oxygen % Smoke Example No. % ZnO % MgO % CaO (Hrs.) ( C) Than Std.) Index Reduction 1 ZnO/MgO (dry blend) 40 60 - 4 950 5 37.7 36 2 ZnO/MgO (wet blend) 37.7 62.3 - 4 900 10 38.3 36 Control A ZnO/MgO uncalcined 40 60 - 0 0 20 38.9 44 B ZnO alone 100 - - 0 0 20 35.5 42 C ZnO/MgO calcined separately 40 60 - 8 900 10 34.6 19 Example No.

3 ZnO/MgO 16.2 83.8 - 8 900 10 35.0 28 4 ZnO/MgO 26.5 73.5 - 8 900 5 34.8 30 5 AnO/MgO 95.2 4.8 - 8 900 10 34.4 10 6 ZnO/CaO 40 - 60 2 950 10 37.0 37 7 ZnO/MgO/CaO 30 35 35 4 900 10 36.3 34 8 ZnCl2/MgCl2 hydrolyzed 40 60 - 2 950 5 37.9 31 9 ZnNO3/MgNO3 hydrolyzed 40 60 - 2 950 5 38.0 40 10 ZnSO4/MgSO4 hydrolyzed 40 60 - 2 950 5 38.3 29 11 Zn/Mg intermetallic alloy 45.8 54.2 - 2 950 5 38.3 29 All agents added at level equivalent to 0.7% zinc oxide 1.5% antimony oxide present in plastic composition Example 3-7 The solid solution flame and smoke retardant agent of the present invention was also compared with the magnesium-zinc sulfate complex salt prepared, disclosed and claimed in U.K. Specification No. 1523531 (U.S. Patent No. 3996142).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 undesirable. 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 5 4.8 6 - 60 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).

Example 8-11 In these runs various zinc and magnesium compounds were used as starting materials. In Examples 8-10, zinc 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 calcium oxides and antimony trioxide 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 smoke 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 include among others zinc borate, aluminum trihydrate, molybdenum trioxide and other commonly used flame and smoke retardant additives.

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 of zinc oxide and magnesium oxide and/or calcium oxide produces a highly desirable flame and smoke 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 invention, a number of additional tests were made using other plastic compositions.

Example 12 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. Goodrich 100.0 100.0 100.0 PVC resin inherent viscosity 0.92 ASTM D-1755 classifica tion 6P-4-16043 avg. mole wt/wt avg. 91,000 (2) Thiotin Stabilizer, M & 0.5 0.5 0.5 Chemicals (3) 165"F Paraffin Wax 1.0 1.0 1.0 (4) Calcium Stearate 0.7 0.7 0.7 (5) Plastiflow POP, N.L. 0.15 0.15 0.15 Industries flexible/rigid lubricant, modified polyethyl ene wax specific gravity @ 25"C. 0.96 melting point, 116"C.

(6) Calcium Carbonate, Omyalite 2.5 2.5 2.5 90-T (7) TiO2, Titanox 2071 1.0 1.0 1.0 (8) Sb2O3 0 0 2.0 (9) ZnO/MgO 0 0 2.0 Oxygen index - ASTM D-2863A 48.7 58.4 66.9 NBS smoke density, 40 mil stocks, flaming conditions Dm (Per gram, 50.0 38.6 32.7 corrected) % Reduction 0 23 35% Example 13 The flame and smoke retardant composition of the instant invention is very effective when used in conjunction 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.F. 100 ---- same same Goodrich PVC resin inherent viscosity 1.02 ASTM D-1755 classification GP-5 15443 avg. mole wt/ wt avg 100,000 (2) Tribase Exl, N.L. 5 ---- same same Industries lead sili cate 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- - - - - 26 26 phate (9) Sub203 - 5 - - - - (10) ZnO/MgO - 4 - 4 - 4 Oxygen index, ASTM D-2863A 24.9 30.6 28.3 28.5 27.1 27.5 NBS smoke density, 40 mil stocks, flaming conditions DM (per gram, corrected) 50.1 35.9 66.1 39.6 54.6 32.4 % Reduction 0 28 0 40 0 41 Example 14 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 same (2) Decabromo Diphenyl Oxide, 10 same same DOW-300BA (3) Plastiflow POP 0.5 same same (4) Sb203 5 4.75 4.75 (5) ZnO/MgO 0 0.25 0.75 (The word "DOW" is a Registered Trade Mark) 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 Example 15 Low levels of the flame and smoke retardant composition of the instant invention are effective for suppressing smoke in polypropylene Pup). 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) (1) PP Pro-Fax 6423 Hercules polypro- 60 60 60 pylene resin, nominal melt flow 12 @ 230"C. 6.5 (2) Dechlorane 515 Hooker Chemicals, 27 27 27 % Cl-65, particle size 5-15 microns, melting point > 350 C.

(3) Sb2O3 12 10 10 (4) ZnO/MgO 0 1 3 (The words "Pro-Fax" and "Dechlorane" are Registered Trade Marks.) NBS smoke density, 25 mil stocks, flaming conditions Dm (per gram, corrected) 43.7 37.7 34.9 % Reduction 0 14 20 Example 16 The flame and smoke retardant composition of the instant invention is very effective when used in acrylonitrile-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) (A) (B) (C) (D) (1) Sb203 12.3 12.3 4 4 (2) ZnO/MgO 0 3 0 3 (3) ABS Cycolac TD 1001, Borg Warner 61.3 61.3 82 82 (4) Lectro 60XL, N.L.Industries, 2 2 2 2 lead chlorosilicate complex, % PbO-64 (5) Dechlorane 515 24.4 24.4 0 0 (6) Citex BC-26 Cities Service 0 0 2 12 tricylic bromine complex, % Br-29, % C1-40 (The word "Cycolac" is a Registered Trade Mark.) Oxygen index, ASTM D-2863A 26.0 29.6 25.0 24.2 NBS smoke density, 15 mil stocks, flaming conditions Dm (per gram, corrected) 84.8 78.8 117 91.8 % Reduction 0 7 0 22 Example 17 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 incorporated into a PVC formulation with Sb203 or ATH the following results were obtained: Formulation: (parts by weight) (A) (B) (C) (D) (E) (F) (1) PVC Geon 102 EP F5 100 ---- same same (2) Deundecyl phthlcate 30 ---- same same (3) Dythal, N.L. Industries, 7 ---- same same dibasic lead stabilizer % PbO-79.8. specific gravity 4.5 (4) Acrawax C, Glycol Chem- 0.3 ---- same same icals, fatty diamide synthetic wax (5) DS-207, N.L. Industries 0.3 ---- same same dibasic lead stearate, % PbO-553, specific gravity (6) Sb2O3 ---- 2 ---- 2 (7) ZnO/MgO ---- ---- 2 2 ---- 2 (8) ATH ---- ---- ---- ---- 20 18 (The word "Acrawax" is a Registered Trade Mark.) Oxygen index, ASTM D-2863A 27.9 32.1 28.1 34.1 30.1 30.8 NBS smoke density, 40 mil stocks, flaming conditions DM (per gram, corrected) 73 75.7 39.3 40.1 53.6 39.9 % Reduction 0 (+3) 46 45 27 46 Example 18 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 92AT, Ashland 100 100 Chemicals halogenated poly ester, properties @ 25"C.

acid number 18, color (gardner) 5 maxium, viscos ity (Brookfield) #2 spindle 50 Rpm 400 #2 spindle 5 Rpm 1100 (2) MEK Peroxide 1 1 (3) Sb203 5 5 (4) ZnO/MgO 0 1 (The word "Hetron" is a Registered Trade Mark.) 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 Example 19 It has been found that the flame and smoke retardant composition of the present 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 Sb203 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 Sb203 and ZnO/MgO was additive.This is shown in the Table below: The formulation used was that of Example I, in parts by weight (1) PVC 100 (2) DOP 23.5 (epoxidized soybean oil) (3) EPOX Oil 1.5 (4) Ba-Cd Stabilizer 2 (5) Stearic Acid 0.5 (6) Additive - Sb2O3 (x), ZnO/MgO (y) x + y = 2 Parts by Weight Additive Dm*(per grams Sb2O3 40/60 ZnO/MgO Ol corrected) % Reduction 2 0 32.9 39.0 0 1.5 0.5 34.6 1 1 34.5 21.8 44 0 2 33.7 19.0 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 of zinc oxide and magnesium oxide and/or calcium oxide produces a highly desirable flame and smoke resistant plastic 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 present invention are easily prepared and economical to employ.

WHAT WE CLAIM IS: 1. A solid solution of zinc oxide and calcium oxide and magnesium oxide containing from 0.1 to 10 parts by weight of calcium and magnesium oxide per part by weight of zinc oxide, and having a specific surface area of at least 10M2/g.

2. A solid solution as claimed in claim 1 containing from 10 to 60% by weight of zinc oxide, from 5 to 50% by weight of calcium oxide and from 10 to 60% by weight magnesium oxide.

3. A solid solution of zinc oxide and calcium oxide containing from 0.1 to 10 parts by weight of calcium oxide per part by weight zinc oxide, and having a specific surface area of at least 10M2/g.

4. A solid solution as claimed in claim 3 containing from 50 to 15% by weight of calcium oxide.

5. A flame and smoke retardant agent for halogen containing plastic compositions (as hereinbefore defined) comprising a mixture of antimony trioxide and a solid solution of zinc oxide and calcium oxide and/or magnesium oxide.

6. A flame and smoke retardant agent for halogen-containing plastic compositions 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 by weight of antimony trioxide for each part by weight of the solid solution.

7. An agent as claimed in either claim 5 or claim 6 wherein the solid solution contains from 0.1 to 1() parts by weight of magnesium and/or calcium oxide per part by weight of zinc oxide.

8. An agent as claimed in claim 7 wherein the solid solution is as claimed in any one of claims 1 to 4.

9. An agent as claimed in claim 7 wherein the solid solution contains from 30 to 50% by weight of zinc oxide and from 70 to 50% by weight magnesium oxide.

10. An agent as claimed in any one of claims 5 to 9 wherein the solid solution has a specific surface area of at least 1() M2/g.

11. A composition being a solid solution as claimed in any one of claims 1 to 4 or an agent as claimed in claim 10 wherein the solid solution has a specific surface area of at least 16 M2/g.

12. A solid solution, agent or composition as claimed in any one of claims 1 to 11 and substantially as hereinbefore described.

13. A method of making a solid solution of zinc oxide and calcium oxide, or zinc oxide, calcium oxide and magnesium oxide which method comprises calcining a mixture of zinc oxide and calcium oxide, or zinc oxide, calcium oxide and magnesium oxide wherein the amount of magnesium and/or calcium oxide is from 0.1 to 10 parts by weight per part by weight of zinc oxide.

14. A method as claimed in claim 13 wherein the oxide mixture is calcined to produce a solid solution having a specific surface area of at least 10 M2/g.

15. A method as claimed in claim 14 wherein the solid solution produced has a specific

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (33)

**WARNING** start of CLMS field may overlap end of DESC **. Parts by Weight Additive Dm*(per grams Sb2O3 40/60 ZnO/MgO Ol corrected) % Reduction 2 0 32.9 39.0 0 1.5 0.5 34.6

1 1 34.5 21.8 44 0 2 33.7 19.0 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 of zinc oxide and magnesium oxide and/or calcium oxide produces a highly desirable flame and smoke resistant plastic 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 present invention are easily prepared and economical to employ.

WHAT WE CLAIM IS: 1. A solid solution of zinc oxide and calcium oxide and magnesium oxide containing from 0.1 to 10 parts by weight of calcium and magnesium oxide per part by weight of zinc oxide, and having a specific surface area of at least 10M2/g.

2. A solid solution as claimed in claim 1 containing from 10 to 60% by weight of zinc oxide, from 5 to 50% by weight of calcium oxide and from 10 to 60% by weight magnesium oxide.

3. A solid solution of zinc oxide and calcium oxide containing from 0.1 to 10 parts by weight of calcium oxide per part by weight zinc oxide, and having a specific surface area of at least 10M2/g.

4. A solid solution as claimed in claim 3 containing from 50 to 15% by weight of calcium oxide.

5. A flame and smoke retardant agent for halogen containing plastic compositions (as hereinbefore defined) comprising a mixture of antimony trioxide and a solid solution of zinc oxide and calcium oxide and/or magnesium oxide.

6. A flame and smoke retardant agent for halogen-containing plastic compositions 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 by weight of antimony trioxide for each part by weight of the solid solution.

7. An agent as claimed in either claim 5 or claim 6 wherein the solid solution contains from 0.1 to 1() parts by weight of magnesium and/or calcium oxide per part by weight of zinc oxide.

8. An agent as claimed in claim 7 wherein the solid solution is as claimed in any one of claims 1 to 4.

9. An agent as claimed in claim 7 wherein the solid solution contains from 30 to 50% by weight of zinc oxide and from 70 to 50% by weight magnesium oxide.

10. An agent as claimed in any one of claims 5 to 9 wherein the solid solution has a specific surface area of at least 1() M2/g.

11. A composition being a solid solution as claimed in any one of claims 1 to 4 or an agent as claimed in claim 10 wherein the solid solution has a specific surface area of at least 16 M2/g.

12. A solid solution, agent or composition as claimed in any one of claims 1 to 11 and substantially as hereinbefore described.

13. A method of making a solid solution of zinc oxide and calcium oxide, or zinc oxide, calcium oxide and magnesium oxide which method comprises calcining a mixture of zinc oxide and calcium oxide, or zinc oxide, calcium oxide and magnesium oxide wherein the amount of magnesium and/or calcium oxide is from 0.1 to 10 parts by weight per part by weight of zinc oxide.

14. A method as claimed in claim 13 wherein the oxide mixture is calcined to produce a solid solution having a specific surface area of at least 10 M2/g.

15. A method as claimed in claim 14 wherein the solid solution produced has a specific

surface area of at least 16 M2/g.

16. A method as claimed in any one of claims 13 to 15 wherein the calcination temperature is at least 500"C.

17. A method as claimed in claim 16 wherein the calcination temperature is from 500"C to 1000"C.

18. A method as claimed in any one of claims 13 to 17 wherein the mixture before calcination includes at least one compound which is not an oxide of zinc or calcium and/or magnesium but which decomposes to such an oxide during calcination.

19. A method as claimed in any one of claims 13 to 18 and substantially as hereinbefore described.

20. Solid solutions of zinc oxide and calcium oxide, or zinc oxide, calcium oxide and magnesium oxide whenever made by the method claimed in any one of claims 13 to 19.

21. A flame and smoke resistant halogen containing plastic composition containing, as a flame and smoke retardant, a solid solution of zinc oxide and calcium oxide and/or magnesium oxide.

22. A flame and smoke resistant halogen-containing plastic composition containing, as a flame and smoke retardant, from 0.5% to 10% of a solid solution of zinc oxide and calcium oxide or magnesium oxide or a mixture thereof, the amount of calcium oxide and/or magnesium oxide present in the solid solution being from .1 to 10 parts by weight for each part by weight of zinc oxide.

23. A composition as claimed in either claim 21 or claim 22 wherein the flame and smoke retardant is a solid solution, agent or composition as claimed in any one of claims 1 to 12 and 20.

24. A flame and smoke resistant halogen-containing plastic composition (as hereinbefore defined) containing therein from 0.25% to 10% by weight of a solid solution of zinc oxide and magnesium oxide, calcium oxide or a mixture thereof, the amount of magnesium oxide and/or 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.

25. A composition as claimed in any one of claims 21 to 24 and substantially as hereinbefore described.

26. A flame and smoke resistant halogen containing plastic composition substantially as described in any one of Examples 1 to 4 and 6 to 11.

27. A method of making a flame and smoke resistant halogen containing polymer composition (as hereinbefore defined) which method comprises incorporating into a halogen containing polymer composition a solid solution of zinc oxide and calcium oxide and/or magnesium oxide.

28. A method of making a flame and smoke resistant halogen containing polymer composition which method comprises incorporating into a halogen containing polymer composition a solid solution, agent or composition as claimed in any one of claims 1 to 12 and 20.

29. A method of making a flame and smoke resistant halogen containing plastic composition which comprises incorporating in the said plastic composition from 0.5% to 10% of a solid solution of zinc oxide and magnesium oxide and/or calcium oxide, the magnesium and/or calcium oxide being present in the said solid solution in an amount of from 0.1 to 10 parts by weight for each part by weight of zinc oxide.

30. A method of making a flame and smoke resistant halogen containing plastic composition which comprises incorporating in the said plastic composition from 0.25% to 10% by weight of a solid solution of zinc oxide and magnesium oxide, calcium oxide or a mixture thereof, the amount of magnesium oxide and/or calcium oxide present in the 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 2000C.

31. A method as claimed in any one of claims 27 to 30 and substantially as hereinbefore described.

32. A method of making a flame and smoke resistant halogen containing plastic composition substantially as hereinbefore described in any one of Examples 1 to 4 and to 11.

33. Flame and smoke resistant halogen containing polymer compositions whenever made by the method claimed in any one of claims 27 to 32.