Flame retardant composition containing zinc borate

Flame retardant compositions comprise linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon and a minor quantity, relative to the polymer, of a zinc borate or barium borate.

FIELD OF THE INVENTION 
Compositions comprising carbon monoxide/ethylenically unsaturated 
hydrocarbon polymers and certain zinc borates demonstrate improved flame 
retardancy. 
BACKGROUND OF THE INVENTION 
The general class of polymers of carbon monoxide and one or more 
ethylenically unsaturated hydrocarbons has been known for some years. 
Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively 
low carbon monoxide content in the presence of free radical catalysts such 
as benzoyl peroxide. British Patent 1,081,304 produced such polymers of 
higher carbon monoxide content in the presence of alkylphosphine complexes 
of palladium as catalyst. Nozaki extended the process to arylphosphine 
complexes of palladium. See, for example, U.S. Pat. No. 3,694,412. 
More recently, the class of linear alternating polymers of carbon monoxide 
and unsaturated hydrocarbons, now known as polyketones, has become of 
greater interest, in part because of improved methods of production. Such 
methods are shown by European Patent Applications 181,014, 121,965, 
222,454 and 257,663. The disclosed processes employ, inter alia, a 
compound of a Group VIII metal such as palladium, an anion of a 
non-hydrohalogenic acid having a pKa below 2 and a bidentate ligand of 
phosphorus. The resulting polymers are generally high molecular weight 
thermoplastic polymers having utility in the production of articles such 
as containers for food and drink and parts for the automotive industry or 
structural members for use in the construction industry. 
With regard to any plastic material employed in a public application, some 
concern must be shown for the consequences of the material catching fire 
and burning. Many plastics, e.g., polyvinylchloride, produce highly toxic 
gases upon combustion. The use of polyketones has advantages in this 
regard since only atoms of carbon, hydrogen and oxygen are present in the 
polymer molecule. Nevertheless, it would be of advantage to provide for 
flame retardant compositions of polyketone polymers. 
Others in the past have attempted to improve the flame retardancy of 
polyketone compositions. For example, U.S. Pat. No. 4,761,449 discloses 
compositions containing a carbon monoxide/ethylenically unsaturated 
hydrocarbon copolymer with an alkaline earth metal carbonate, such as 
calcium carbonate. While these compositions show improved flame retardancy 
they still have certain deficiencies. In particular, the compositions 
containing up to 25% calcium carbonate still have Limiting Oxygen Index 
(LOI) values of only 27-27.5. LOI values of 30 or greater are required for 
man commercial applications. In addition, the mechanical properties of the 
flame retardant compositions must remain high if the compositions are to 
have commercial significance. Therefore, it is important that the amount 
of flame retardant necessary to obtain commercial compositions be as small 
as possible. 
SUMMARY OF THE INVENTION 
This invention relates to flame-retardant compositions of linear 
alternating polymers of carbon monoxide and at least one ethylenically 
unsaturated hydrocarbon. More particularly, the invention relates to 
compositions of such polymers incorporating a flame-retardant quantity of 
a zinc borate or barium borate. Compositions according to the present 
invention not only have high LOI values, but also have good mechanical 
values (i.e. high modulus and impact). Still further, these compositions 
are non-toxic, i.e. they do not release toxic fumes such as HCl or HF 
gases. 
COPENDING PATENT APPLICATIONS 
Copending U.S. ptent application Ser. No. 332,250, filed Mar. 31, 1989 now 
U.S. Pat. No. 4,885,328 (titled "Flame Retardant Compositions") discloses 
and claims a flame retardant composition comprising a polyketone polymer 
and certain alkaline earth metal hydroxides, such as magnesium hydroxides. 
Copending U.S. patent application Ser. No. 332,636, filed Mar. 31, 1989 now 
U.S. Pat. No. 4,885,318 (titled "Polyketone Flame Retardant Composition") 
discloses and claims a flame retardant composition with a polyketone 
polymer and various flame retardants, including antimony trioxide and 
decabromo diphenyloxide.

DESCRIPTION OF THE INVENTION 
The polymers from which the compositions of the invention are produced are 
linear alternating polymers of carbon monoxide and at least one 
ethylenically unsaturated hydrocarbon. Suitable ethylenically unsaturated 
hydrocarbons have up to 20 carbon atoms inclusive, preferably up to 10 
carbon atoms inclusive and are wholly aliphatic such as ethylene and other 
.alpha.-olefins including propylene, butene-1, octene-1 and dodecene-1 or 
are arylaliphatic containing an aryl substituent on an otherwise aliphatic 
molecule, particularly an aryl substituent on a carbon atom of the 
ethylenic unsaturation. Illustrative of this latter class of olefins are 
styrene, p-methylstyrene, m-methylstyrene and p-ethylstyrene. Preferred 
polyketone polymers are copolymers of carbon monoxide and ethylene or 
terpolymers of carbon monoxide, ethylene and a second aliphatic 
.alpha.-olefin of 3 or more carbon atoms, particularly propylene. 
Of particular interest are those polymers of molecular weight from about 
1,000 to about 200,000, particularly those of molecular weight from about 
10,000 to about 50,000, and containing substantially equimolar quantities 
of carbon monoxide and ethylenically unsaturated hydrocarbon. 
Such polymers are typically produced by contactiong the carbon monoxide and 
the ethylenically unsaturated hydrocarbon(s) under polymerization 
conditions in the presence of a catalytic amount of a catalyst formed from 
a compound of the Group VIII metals palladium, cobalt or nickel, the anion 
of a non-hyrohalogenic acid of a pKa less than about 6, preferably less 
than about 2, and a bidentate ligand of phosphorus, sulfur, arsenic or 
antimony. Although the scope of the polymerization is extensive, for 
purposes of illustration a preferred Group VIII metal compound is 
palladium acetate, the anion is the anion of an acid selected from 
trifluoroacetic acid and para-toluenesufonic acid and the bidentate ligand 
is selected from 1,3-bis(diphenylphosphino)propane and 
1,3-bis[di(2-methoxyphenyl)phosphino]propane. 
Polymerization is carried out at polymerization conditions, typically at 
elevated temperature and pressure, in the gaseous phase or in the liquid 
phase in the presence of an inert diluent, e.g., a lower alkanol such as 
methanol or ethanol. The reactants are contacted by conventional methods 
such as stirring or shaking and subequent to reaction the polymer product 
is recovered as by decantation or filtration. The polymer product may 
contain metallic residues from the catalyst which are removed by contact 
with a solvent which is selective for the residues. Production of these 
polymers is illustrated, for example, by published European Patent 
Applications 181,014, 121,965, 222,454 and 257,663. 
The physical properties of the polymer will be determined in part by the 
molecular weight and by whether the polymer is a copolymer or a 
terpolymer. Typical melting points are from about 175.degree. C. to about 
300.degree. C., more typically from about 210.degree. C. to about 
280.degree. C. The structure of the preferred polymers is that of a linear 
alternating polymer of carbon monoxide, ethylene and any second 
ethylenically unsaturated hydrocarbon. When terpolymers of carbon 
monoxide, ethylene and a second ethylenically unsaturated hydrocarbon, 
e.g., a hydrocarbon of at least 3 carbon atoms, are produced there will be 
at least two units incorporating moieties of ethylene per unit 
incorporating a moiety of the second unsaturated hydrocarbon, preferably 
from about 10 units to about 100 units incorporating moieties of ethylene 
per unit incorporating a moiety of the second unsaturated hydrocarbon. The 
polymer chain of the preferred class of polymers is illustrated by the 
formula 
EQU [CO(C.sub.2 H.sub.4 ].sub.x [CO--(B)].sub.y 
wherein B is the moiety obtained by polymerization of the second 
ethylenically unsaturated hydrocarbon through the ethylenic unsaturation. 
The --CO(C.sub.2 H.sub.4 -- units and the --CO(B-- units occur randomly 
throughout the polymer molecule and the ratio of y:x is no more than about 
0.5. In the modification of the invention which employs copolymers of 
carbon monoxide and ethylene without the presence of a second 
ethylenically unsaturated hydrocarbon, the term y is zero and the ratio of 
y:x is also zero. When terpolymers are employed, i.e., y is greater than 
zero, ratios of y:x from about 0.01 to about 0.1 are preferred. The end 
groups or "caps" of the polymer chain will depend on the particular 
materials present during its production and whether and how the polymer 
has been purified. The precise nature of the end groups is of little 
significance with regard to the overall properties of the polymer so that 
the polymer is fairly represented by the polymer chain as depicted above. 
The flame retardant compositions of the invention contain a flame retarding 
quantity of a zinc borate or barium borate, preferably a zinc borate. The 
typical composition of zinc borate is xZnO.yB.sub.2 O.sub.3, and is 
usually available in the hydrated form. A preferred zinc borate has the 
formula 2ZnO.3B.sub.2 O.sub.3.3.5H.sub.2 O. Due to slight amounts or 
impurities and analytical errors, the H.sub.2 O content can vary between 
about 3.3 and 3.7 but it will generally average about 3.5H.sub.2 O. It 
will be appreciated that this zinc borate has a much lower degree of water 
hydration than many other zinc borates. Due to the low amount of water of 
hydration there is less problem with this zinc borate when it is added to 
polymeric material with regard to formation of bubbles than with other 
zinc borates or other inorganic materials during processing, molding and 
curing. When the specific zinc borate is added to polymers, fire 
resistance of the polymers is greatly improved while the other physical 
properties of the polymers are not deteriorated. 
A method for producing the zinc borate of low hydration is set forth in 
U.S. Pat. No. 3,549,316, and its use with certain halogenated polymeric 
compositions is disclosed in U.S. Pat. No.3,718,615. 
The preferred zinc borate is available commercially under the tradename 
Firebrake.RTM. ZB flame retardant. 
The zinc borate is employed in an amount sufficient to render the resulting 
composition flame retardant. Compositions from about 2 to about 50 percent 
by weight, based on the total composition, of the zinc borate are 
preferred. More preferred are compositions having about 15 to about 40 
percent by weight zinc borate. 
In an alternative embodiment an alkaline earch metal carbonate is also 
incorporated in the composition to replace a portion of the zinc borate. 
One of the considerations in adding the carbonate is cost. 
By alkaline earth metal carbonate is meant a carbonate salt of a metal of 
Group IIA of the Periodic Table of Elements. While carbonate salts of 
berylium, magnesium, calcium, strontium and barium are suitable, the 
preferred flame retarding carbonate salts are carbonates of magnesium and 
calcium, particularly calcium. If desired the CaCO.sub.3 may be surface 
treated to improve dispersion. Such surface treatments include treatment 
with stearic acid or salts of stearic acid. 
The alkaline earth metal carbonate is typically provided in the form of a 
fine powder, for example, above about 0.04 .mu.m but below about 100 
.mu.m. The alkaline earth metal carbonate is preferably employed as such, 
but in alternate modifications alkaline earth metal compounds may be 
utilized which serve to generate alkaline earth metal carbonates during 
processing or upon exposure of the resulting composition to heat at 
temperatures lower than those at which flame would result. An example of a 
material useful as an alkaline earth metal carbonate precursor is the 
corresponding alkaline earth metal bicarbonate. 
The following relative amounts of polymer, zinc borate and alkaline earth 
metal carbonate are suitable (expressed in weight percent of the total 
composition): 
______________________________________ 
More 
Preferred Preferred 
______________________________________ 
Polyketone about 60 to about 85% 
about 60 to about 85% 
Polymer 
zinc borate 
about 5 to about 30% 
about 20 to about 30% 
alkaline earth 
about 5 to about 20% 
about 5 to about 10% 
metal carbonate 
______________________________________ 
Note the percentages should add up to 100 percent in actual compositions. 
The relative amount of zinc borate to alkaline earth metal carbonate should 
be 1:1 or greater, preferably the weight ratio should be at least 2:1, for 
example between 2:1 and 3:1. 
The zinc borates may be employed with other materials such as ammonium 
thiosulfate, asbestos, alkali metal carbonates or bicarbonates, e.g., 
potassium bicarbonate or stannous or stanic oxide. The preferred 
compositions of the invention, however, are those wherein zinc borate is 
employed as substantially the sole material used to impart flame 
retardancy to the polyketone composition. 
The flame retardant compositions are produced by mixing the zinc borate 
throughout the polyketone polymer. The method of forming the composition 
is not critical so long as the method results in a uniform mixture of zinc 
borate throughout at least the outer layer of the polyketone polymer. In a 
preparation of a composition useful in the form in which it is produced, 
only the outermost portion of the composition need be provided with zinc 
borate. However, in most applications, a flame retardant composition is 
produced which is then processed further and in such applications the 
production of a substantially uniform mixture of polyketone polymer and 
zinc borate is preferred. In one modification, the compositions are 
produced by dry blending the components in particulate form and converting 
to a substantially uniform composition by application of heat and 
pressure. Alternatively, the compositions are produced by heating the 
polyketone polymer until molten and the zinc borate thereof is mixed 
throughout the polymer by use of a high-shear mixer or extruder. 
The polymer composition, in addition to polymer and zinc borate, may 
incorporate other conventional additives which do not detract from the 
flame retardant character of the composition. Examples of such additives 
are plasticizers, mold release agents and antioxidants which are added by 
blending or other conventional methods together with or separately from 
the zinc borate. 
The flame retarfdant compositions are processed by injection molding, 
pressure forming or other conventional fabrication methods. They are 
characterized by the same combination of good impact, stiffness and heat 
resistant properties found in the neat polymer, and in addition have 
excellent flame retardancy. The compositions of this invention are useful 
in a variety of applications, particularly where exposure to elevated 
temperature is likely to be encountered. The compositions are useful in 
the production of parts for the automotive industry, electronics industry 
and electrical industry. The compositions are particularly useful for 
those automotive parts located within the engine compartment where high 
temperatures are encountered or those parts which encounter heat as during 
the baking of painted surfaces, e.g. wire coatings, connectors, etc. 
The compositions of the invention are further illustrated by the following 
Comparative Examples and Illustrative Embodiments which should not be 
construed as limiting the invention. 
Illustrative Embodiment I 
A first terpolymer (Polymer 1) of carbon monoxide, ethylene and propylene 
was prepared in the presence of a catalyst formed from palladium acetate, 
trifluoroacetic acid and 1,3-bis(diphenylphosphino)propane. The polymer 
had a melting point of 219.degree. C. and a limiting viscosity number 
(LVN) of 1.60 measured at 60.degree. C. in m-cresol. A second terpolymer 
(Polymer 2) of carbon monoxide, ethylene and propylene was prepared in the 
presence of a catalyst formed from palladium acetate, trifluoroacetic acid 
and 1,3-bis[di(2-methoxyphenyl)phosphino]propane. The second terpolymer 
had a melting poit of 221.degree. C. and a LVN of 1.83 measured at 
60.degree. C. in m-cresol. 
Comparative Example I 
Polymer 1 of Illusrative Embodiment I was blended with different weight 
percents of calcium carbonate by use of a twin-screw extruder to extruder 
to produce nibs. Polymer 2 was also extruded to produce nibs for 
comparison purposes as a control without the addition of calcium 
carbonate. The nibs were injection molded into test bars of approximately 
4.75 in. by 0.5 in. by 0.125 in. dimensions. The test bars were then 
sliced lengthwise into 3 equal strips and the edges were smoothed off. 
These strips were tested for flame retardancy. 
Standard test method ASTM D2863-77 was used to evaluate the burning 
behavior of the different blend compositions. This test measures the 
minimum concentration of oxygen in an oxygen-nitrogen atmosphere that is 
necessary to initiate and support a flame for 180 seconds on a test strip. 
The result of the test is expressed as the percentae of oxygen in the 
oxygen-nitrogen atmosphere and is called the Limiting Oxygen Index (LOI) 
of the composition. 
The LOI values determined for three different blends of the terpolymer of 
Ilustrative Embodiment I and calcium carbonate are given in Table I 
together with the LOI of the terpolymer without added calcium carbonate 
used as a control sample. One can see from the LOI values in Table A that 
a greater percentage of oxygen was required in an oxygen-nitrogen 
atmosphere to initiate and support a flame on the samples containing 
calcium carbonate in comparison to the control sample without calcium 
carbonate. The flame retardancy of the blend compositions is improved for 
the samples containing calcium carbonate, however the LOI values are still 
too low for most commercial applications. 
TABLE I 
______________________________________ 
Sample % Weight Calcium Carbonate 
LOI* 
______________________________________ 
Control none 18.5-19 
l 5 23-23.5 
2 10 25.5-26 
3 25 27-27.5 
______________________________________ 
*LOI values are expressed as a range obtained for three duplicate test 
samples. 
Illustrative Embodiment II 
A linear alternating terpolymer of carbon monoxide, ethylene and propylene 
was prepared, hereinafter referred to as Polymer 87-011. Polymer 87-011 
was prepared in the presence of a catalyst formed from palladium acetate, 
the anion of trifluoroacetic acid, and 1,3-bis(diphenylphosphino)propane. 
Polymer 87-011 had a melting point of 218.degree.) C. and an LVN of 1.14. 
In Illustrative Embodiment II, four fillers (talc, mica, surface treated 
mica and calcium carbonate) and a zinc borate flame retardant (Firebrake 
ZB, having the formula 2ZnO.3B.sub.2 O.sub.3.3.5H.sub.2 O) were dry 
blended with Polymer 87-011 at amounts of 20 and 40% by weight of the 
filler/flame retardant on a 15 mm Baker Perkins twin-screw extruder. This 
equipment had no devolatilization capabilities. Extrusion conditions were: 
______________________________________ 
Atmosphere: air 
RMP: 300 
Feed Rate and Torque: 
adjusted maximize mixing 
Temperatures: 425.degree. F., 454.degree. F., 486.degree., 456.degree. 
F. 
Feed-Die 
______________________________________ 
All of the extrudates were foamy except for those from the calcium 
carbonate blends. Some foaming was expected due to the inability to 
devolatilize. The extrudates were then pelletied, dried at 50.degree. C. 
for 16 hours, and compression molded into 5".times.0.5".times.0.125" test 
schemes for the LOI test. 
The LOI results are listed in Table II. As seen in Table II, the 
compositions containing zinc borate are preferred. 
TABLE II 
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PRELIMINARY SCREENING OF FLAME 
RETARDANTS FOR POLYKETONE 
Polymer 87-011 
LVN = 1.14 
BASE POLYMER: LEVEL 
FILLER (wt. % based on total blend) 
LOI 
______________________________________ 
Talc 20% 22.5 
Talc 40% 26.5 
Zinc Borate 20% 27.5 
Zinc Borate 40% 30.5 
Mica 20% 24.5 
Mica 40% 23.5 
Surfaced treated Mica 
20% 21.5 
Surfaced treated Mica 
40% 29.5 
Calcium Carbonate 
20% 22.5 
Calcium Carbonate 
40% 29.5 
______________________________________ 
Illustrative Embodiment III 
In Illustrative Embodiment III, the polyketone employed was a blend of two 
specific linear alternating polymers This blend comprised 33% of the novel 
polyketone polymer 088-005 and 67% of the novel polyketone polymer 
088-006. Polymer 088-005 was a linear alternating terpolymer of carbon 
monoxide, ethylene and 7 wt% propylene prepared by employing a catalyst 
composition formed from palladium acetate, the anion of trifluroacetic 
acid and 1,3-bis[di(methoxy-phenyl)phosphino]propane. Polymer 088-005 had 
a melting point of 220.degree. C. and a limiting viscosity number (LVN) 
measured in 60.degree. C. meta-cresol of 1.79. Polymer 088-006 was a 
linear alternating polymer prepared in a manner identical to to the 
088-005 polymer. The 088-006 polymer had a melting point of 223.degree. C. 
and an LVN of 1.62. The neat polymer blend was formed by drying mixing 
pellets of the two polymers 088-005 with 088-006 in a conventional manner. 
The blended mixture was then melt blended in a 30 mm co-rotating twin 
screw extruder having seven zones and total L/D of 27/1. The melt 
temperature at the die exit was 260.degree. C. and the temperatures along 
the barrel were maintained at about 466.degree. F. 
Based on the results from Illustrative Embodiment II, zinc borate was 
chosen, in conjunction with calcium carbonate, to scale up to larger batch 
size. About 15 pounds of each of the blends listed in Table III were 
compounded on a 30 mm ZSK twin-screw extruder. 
The goal of this compounding was to incorporate the chosen flame retardants 
into the polyketone polymer utilizing two stage feed with vacuum 
devolatilization. The initial screw design was similar to successful 
screws used when compounding the polyketone with other polymers. This 
screw was intended to provide good melting and mixing prior to the second 
stage. This screw ran the neat polymer well; however, severe temperature 
rises occurred with the downstream addition of a separate flame retardant 
(Kisuma 5BG magnesium hydroxide). Possible causes for this were thought to 
be: 
1. First stage too intense. Melt temperature at the point of flame 
retardant addition triggered foaming of retardant. 
2. Insufficient mixing of flame retardant and polymer in second stage. 
A single feed, gentle mixing screw was assembled to eliminate the severe 
temperature rise, and the Firebrake ZB blends compounded satisfactorily. 
The blends were pelletized, dried at 160.degree. F. for 16 hours, and 
injection molded into the test specimens. Room temperature Notched Izod, 
Flex Modulus and LOI tests were run. 
All test results are listed in Table III. 
TABLE III 
______________________________________ 
PHYSICAL PROPERTIES OF FLAME 
RETARDED POLYKETONE POLYMER 
NOTCHED 
IZOD FLEX MOD. 
COMPOSITION ft.-lb/in. psi LOI 
______________________________________ 
Polymer Blend 3.00 260,000 17.5 
88-005,006 
Polymer Blend 
88-005,006/Zinc Borate/ 
CaCO3 
80/10/10 0.94 325,000 24.5 
70/20/10 0.75 410,000 27.5 
60/30/10 0.52 480,000 30.5 
75/20/5 0.75 370,000 29.5 
______________________________________ 
Note: 
All samples had 0.3% Ethanox 330 added based on Polyketone content. 
All samples were compounded in a 30 mm ZSK Twin Screw Extruder and 
injection molded. 
*The amounts listed are weight percent based on total composition. 
As can be seen above, acceptable LOI values are obtained with a combination 
of zinc borate and CaCO.sub.3 flame retardants.