IL95673A

IL95673A - Smoke suppressed thermoplastic resin composition and a method for suppressing the tendency of thermoplastic resin compositions to smoke under conditions of burning

Info

Publication number: IL95673A
Application number: IL9567390A
Authority: IL
Original assignee: Great Lakes Chemical Corp
Priority date: 1989-09-15
Filing date: 1990-09-13
Publication date: 1995-05-26
Also published as: WO1991004294A1; AU6625390A; AU7035594A; IL95673A0; CA2025172A1; EP0500608A1; KR927003711A; JPH05500983A

Description

A SMOKE SUPPRESSED THERMOPLASTIC RESIN COMPOSITION AND A METHOD FOR SUPPRESSING THE TENDENCY OF THERMOPLASTIC RESIN COMPOSITIONS TO SMOKE UNDER CONDITIONS OF BURNING BACKGROUND OF THE INVENTION Field of the Invention. This invention relates to flame retardant thermoplastic resin compositions that exhibit a reduced tendency to generate smoke under burning conditions. More particularly, this invention relates to thermoplastic compositions such as polyvinyl chloride ("PVC"), polystyrene and polyolefins, comprising bicyclic phosphate compound(s); and flame retardant agent(s). The compositions produced in accordance with this invention exhibit a reduced tendency to smoke under burning conditions .

Description of the Prior Art. It is known in the art that the flammability of thermoplastics, such as polystyrene, polyolefins, and polyvinyl halides, can be reduced by incorporation of a flame retardant agent. Typical flame retardant agents include reactive or additive halogenated organic compounds, inorganic fillers, and special formulations based on phosphorous and ammonium salts.

Although efficient in suppressing the rate of combustion in a resin system, most flame retardants tend to affect adversely one or more key properties of the resin. For example, many flame retardant additives are ineffective at producing low smoke ("smoke suppressed") formulations.

Recent public awareness about risk and hazard assessment during fire situations, and technical limitations of conventional flame retardant additives warrant a need for improved flame retardant thermoplastic compositions. In particular, a need exists for a thermoplastic composition that passes flammability standards with low smoke and combustion by-product formation, and does not detract from overall polymer performance.

Many prior art references describe the use of a variety of smoke additives in polystyrene and polyolefins. Modern Plastics Encyclopedia , Vol. 63, No. 10A, McGraw-Hill, Inc., pp. 179-180 (1986). However, the selection of a suitable smoke suppressant for thermoplastic resins is not predictable. Selection is particularly difficult when flame retardants are employed, exacerbated by the complex interaction between the polymer and the flame retardant agent.

Hechenbleikner , et al. describe in U.S. Patent No. 3,293,327 the production of bicyclic phosphites, phosphonates , thiophosphates , and selenophdsphates . These compositions are said to be stabilizers for vinyl halide resins. They are alleged to be useful as heat stabilizers for vinyl chloride resin, and as antioxidants for fats and oils. The Hechenbleikner patent does not specify the use of bicyclic phosphates to achieve low smoke thermoplastic resin compositions, nor does it disclose that cyclic phosphates of the present invention could be used with flame retardant agents to produce smoke suppressed flame retardant thermoplastic compositions.

British Patent No. 999,793 describes a process for producing organic phosphates by subjecting organic phosphites to reaction with peracetic acid. This patent shows a method for producing the most preferred bicyclic phosphate of the present invention, 2,6, 7-trioxa-l-phosphobicyclo[ 2.2.2] -octane-4- methanol-1-oxide and teaches the use of acetal ring-containing phosphates as plasticizers or functional fluids. The British patent, however, does not disclose the present invention. It does not mention bicyclic phosphates as being useful for flame retardant thermoplastic resins, nor that the most preferred bicyclic phosphate of the present invention can be used with flame retardant additives to yield improved smoke suppressed thermoplastic compositions.

Hills, et al. describe in U.S. Patent No. 3,873,496 a flame retardant polyester composition which contains 5 to 25 percent of a hydroxymethyl bicyclic phosphate compound as a flame retardant additive. Hills did not observe the ability for bicyclic phosphates to act as smoke suppressors for thermoplastic resin compositions which employ halogenated compounds as the primary flame retardant additive.

Halpern, et al. describe in U.S. Patent No. 4,341,694 a composition comprising 2 , 6 , 7-trioxa-l-phosphobicyclo[ 2.2.2 ] -octane-4-methanol-l-oxide and a nitrogen-containing co-additive, which are intumescent and are adaptable to flame retard polyolefins, polyvinylaromatic resins, polycarbonates, PVC and blends thereof. Halpern did not observe any smoke suppression of the present invention.

Parr, et al. describe in U.S. Patent No. 4,801,625 a flame resistant composition having (1) an organic polymeric substance in intimate contact with (2) a bicyclic phosphorous compound, and (3) a gas producing compound. Parr is silent on the use of bicyclic compounds to attain smoke suppressed flame retardation thermoplastic compositions.

Accordingly, a primary object of this invention is to provide smoke suppressed flame retardant thermoplastic compositions.

A related object is to provide flame retardant thermoplastic polyvinyl chloride compositions with a reduced tendency to smoke under burning conditions.

A further object is to provide polyvinyl chloride resin compositions incorporating bicyclic phosphate compound and flame retardants. - 6 - 95673/2 The foregoing and other objects, advantages and features of the present invention may be achievable with smoke suppressed thermoplastic polyvinyl halide, polyolefin or polystyrene resin compositions incorporating an effective amount of an additive mixture comprising a" flame retardant agent and a bicyclic phosphate compound.

More particularly, the invention provides a smoke suppressed thermoplastic resin composition comprising a polyvinyl halide, polyolefin or polystyrene resin; and an effective amount of a mixture comprising a smoke suppressant comprising at least one bicyclic phosphate compound of the formula: where X is OH, OR' , or OC(0)R' ; R is H or a saturated or unsaturated straight-chain or branched-chain C3.-C3.-7 alkyl; and R' is a saturated or unsaturated straight-chain or branched-chain C3.-C3.-7 alkyl; and a flame retardant agent as herein defined, differing in composition from said smoke suppressant, and being nitrogen-free.

Compoositions in accordance with the present invention exhibit a reduced tendency to smoke under burning conditions.

The invention also provides a method for suppressing the tendency of polyvinyl halide, polyolefin or polystyrene resins to smoke under conditions of burning, comprising the step of incorporating therein an effective amount of a - 6A - 95673/ 1 mixture comprising a smoke suppressant comprising at least one bicyclic phosphate compound of the formula: where X is OH, OR' , or OC(0)R' ; R is H or a saturated or unsaturated straight-chain or branched-chain -C^-, alkyl; R' is a saturated or unsaturated straight-chain or branched-chain C -C 7 alkyl; and a flame retardant agent as herein defined, differing in composition from said smoke suppressant, and being nitrogen-free.

Preferred bicyclic phosphates in accordance with this invention are compounds of Formula (I) where X is OH or OC(0)R' . The most preferred bicyclic compounds are 2 , 6 , 7-trioxa-phosphobicyclo[ 2.2.2 ] -octane-4-methanol-l-oxide (Compound BCP, that is, Formula [I] when R is H and X is OH), and 2,6, 7-trioxa-l-phosphobicyclo[ 2.2.2] -octane- -methanol , acetate, 1-oxide (Compound BCP-A, that is, when R is H and X is OC(0)CH3) The flame retardant agent employed in accordance with the present invention may be any common flame retardant agent which can be used to reduce the flammability of thermoplastic resins, such as halogenated compounds containing bromine and/or chlorine or inorganic materials, such as metal hydrates, metal borates, antimony-containing compounds, or phosphorous-containing compounds .

Preferred halogen-containing compounds are di- ( 2-ethylhexyl )tetrabromophthalate , hexabromocyclododecane , tetrabromobisphenol A, tetrabromobisphenol A bis- (dibromopropylether ) , dibromo(dibromoethyl)cyclohexane, tetrabromocyclooctane , bis- (dibromonorbornane dicarboximido ) ethane , bi s- ( tetrabromophthalimido ) ethane , Diels-Alder adduct of chlorinated cyclopentadiene and an unsaturated cycloaliphatic compound, bis- ( tribromophenoxyethyl ) -tetrabromobisphenol A ether, pentabromodiphenyl ether, octabromodiphenyl ether, decabromodiphenyl ether, bis- (tribromophenoxy) ethane, bis- (pent bromophenoxy) ethane , chloropentabromocyclohexane , ( tribromophenoxy) - (dibromononylphenoxy) ethane , pentabromoethylbenzene , pentabromododecylbenzene , carbonate oligomers of tetrabromob sphenol A, poly (bromostyrene ) , and brominated polystyrene, poly (bromophenylene ) ether, and mixtures thereof. Particularly preferred is di-(2-ethylhexyl)tetrabromophthalate.

Substantially any suitable metal hydrates and oxides may be employed as flame retardant agents, including hydrates and oxides of aluminum, iron, zinc, magnesium, tin, molybdenum and antimony. Alumina trihydrate, magnesium hydroxide, and antimony trioxide are the preferred compounds in this class.

Suitable metal boron-containing flame retardant compounds include zinc, barium, calcium, magnesium, cadmium and mercury. Zinc borate is the preferred compound in this class.

Substantially any suitable phosphorus-containing compound may be used as a flame retardant agent, including ammonium polyphosphate, arylphosphates , alkarylphosphates and alkylphosphates . Particularly preferred are phenyl isopropylphenyl phosphate and isodecyldiphenyl phosphate commercially available from FMC Corporation under the trademarks Kronitex 100 and Santicizer 148.

The foregoing flame retardant compounds are added to thermoplastic resins at effective levels such that the resultant resin composition may be rendered flame retardant.

Thermoplastic resins which may be treated in accordance with the invention include thermoplastics such as polyvinyl halides, polystyrene, and homopolymers and copolymers of polypropylene, polyethylene, and polybutylene . Polyvinyl chloride is most preferred in accordance with this invention.

The scope of the present invention also includes the incorporation of other additives in the composition so far as to produce a particular end result. Such additives include, without blowing agents, heat stabilizers, light stabilizers, plasticizers , pigments, preservatives, ultraviolet light stabilizers, fillers, antioxidants, antistatic agents and other materials well known to those skilled in the art, for example, as described in Modern Plastics Encyclopedia, Vol. 63_, No. 10A, McGraw-Hill, Inc. (1986).

The bicyclic phosphates of the present invention may be used alone or as mixtures of any such compounds. When mixtures of bicyclic phosphates are employed, substantially any combinations of amounts and proportions of the individual compounds may be used. The use of Compound BCP and Compound BCP-A is especially preferred in accordance with this invention.

The bicyclic phosphate may be employed at substantially any level because even very low levels are believed to assist in smoke suppression. Preferably it is present at a level of at least 2 percent and preferably about 3 percent up to about 20 percent by weight of the composition.

The flame retardant agents of the present invention may be used alone or as mixtures of any such compounds. When mixtures of flame agents are employed, substantially any combinations of amounts and proportions of the individual compounds may be used. The use of di- ( 2-ethylhexyl ) - tetrabromophthalate, alumina trihydrate, magnesium hydroxide, zinc borate, antimony trioxide, and alkylaryl phosphates are especially preferred in accordance with this invention.

Desirably, flame retardants are employed at a level of about 2 to 50 percent by weight of the composition, preferably about 3 to 20 percent, depending on the specific flame retardant and thermoplastic resin employed. Operative and preferred ranges for various flame retardants in accordance with this invention are given in the Table I .

TABLE I OPERATING RANGES MATERIAL OPERATIVE RANGE PREFERRED RANGE BrFr 2-50 3-20 AAP 2-50 3-20 ATH 2-50 5-20 MgOH 2-50 5-10 ZnBor 2-50 5-10 SbOx 1-15 5-10 BrFr - di- ( 2-ethylhexyl ) tetrabromophthalides brominated flame retardant AAP - alkylarylphosphate (Kronitex 100 - FMC Corp. ) ATH - alumina trihydrate MgOH - magnesium hydroxide ZnBor - zinc borate SbOx - antimony oxide Desirably, the bicyclic phosphate compound and flame retardant are provided as a mixture useful as an additive which may be added to polystyrene or polyolefin resin compositions. The additive mixture utilizes bicyclic phosphate and flame retardant in a weight ratio lying in the range of about 1:25 to 20:1, most preferably, about 3:20 to 20:3.

The additive mixture is incorporated into the polymer composition at an effective level such that the resulting resin composition is rendered flame retardant. In general, the additive mixture is provided in the flame retardant at a level of about 2 - 50 percent by weight of the resin composition, preferably about 3 - 30 percent by weight.

Practice of the present invention is illustrated by the following examples, which are given to illustrate the invention and should not be construed as limiting its scope.

EXAMPLES Preparation of Polyvinylchloride Resin Systems. A general purpose polyvinylchloride ("PVC") resin was used in the study. PVC resin, powdered additives and flame retardant were blended in a mixing bowl and warmed to 90°C. Liquid plasticizer was added, and the admixture was compounded on a two-roll mill at 160°C. The compounded PVC material was compression molded at 180°C.

Table II shows examples of the use of Compound BCP in flexible PVC formulations. The general formulation used is as follows: Material ¾ by weight PVC Resin varied Compound BCP varied (see Table) Flame Retardant varied (see Table) Dioctylphthalate Plasticizer varied (see below) Epoxidized Soya Plasticizer 5 Stabilizer 3 The amount of dioctyl phthalate ("DOP") plasticizer was adjusted to give compositions with comparable physical properties (i.e., approximately 90 Shore A hardness) and flammability (approximately 30 01) performance.

Flammability Test Procedures. The following flammabi lity tests were used throughout the study: Test Method Description ASTM D-2863 Limiting Measurement of the minimum oxygen Oxygen Index necessary to sustain burning of a vertically supported sample for three minutes. High values indicate improved resistance to burning.

NBS Smoke Chamber Smoke density determinations ASTM -662 under smoldering conditions. Low values indicate low smoke evolution.

A series of experimental and comparative studies were performed using the foregoing techniques. The data are given in Table II.

TABLE II FLAMMABILITY AND PHYSICAL PROPERTY PERFORMANCE FLEXIBLE POLY INYLCHLORIDE COMPOSITIONS EXAMPLE AMOUNT OF FLAME RETARDANT NBS SMOKE OXYGEN HARDNESS NUMBER BCP TYPE AMOUNT SMOLDERING INDEX SHORE A Wt % wt % ASTM -662 ASTM ASTM D-2863 CONTROL 5 .0 0.0 170 30 90 1 5 .0 BrFr 10.0 165 30 90 COMP 2 0 .0 BrFr 10.0 210 30 90 2 5 .0 AAP 15.0 160 30 90 COMP 3 0 .0 AAP 15.0 200 30 90 3 5 .0 ATH 15.0 145 30 90 COMP 4 0 .0 ATH 15.0 160 30 90 4 5 .0 MgOH 15.0 140 30 90 COMP 5 0 .0 MgOH 15.0 165 30 90 5 5 .0 ZnBor 15.0 130 30 90 COMP 6 0 .0 ZnBor 15.0 155 30 90 BCP - Preferred bicyclic phosphate BrFr - di- (2-ethylhexyl ) tetrabromophthalates AAP - alkylarylphosphate (Kronitex 100 - FMC Corp.) ATH - alumina trihydrate MgOH - magnesium hydroxide ZnBor - zinc borate These data demonstrate the patentability of the subject invention as follows. The Control Example shows the effect of 5.0% BCP alone on the smoke performance of a 30 01 flexible PVC composition. Comparative Examples 2-6 show the effect of various flame retardants on smoke performance when Compound BCP is not present.

Example 1 illustrates the invention when the flame retardant is a bromine-containing flame retardant. Example 2 illustrates the invention when the flame retardant is phosphate-containing flame retardant (an alkarylphosphate ) . Example 3-5 illustrate the invention when the flame retardant is an inorganic flame retardant.

In the case of each invention composition, compositions comprising a bicyclic phosphate (Compound BCP) and a flame retardant had lower smoke than the Control (i.e., a system without any additional flame retardant agent) or the corresponding Comparative Examples 2-6 (i.e., a system without bicyclic phosphate).

Claims

- 16 - 95673/3 WHAT IS CLAIMED IS:

1. A smoke suppressed thermoplastic resin composition, comprising: a polyvinyl halide, polyolefin or polystyrene resin; and an effective amount of a mixture comprising: a smoke suppressant comprising at least one bicyclic hos ha e compound of the formula: where X is OH, OR', or OC(0)R'; R is H or a saturated or unsaturated straight-chain or branched-chain C -C1V alkyl; and R 1 is a saturated or unsaturated straight-chain or branched-chain C;,.-C17 alkyl; and a flame retardant agent as hereinbefore defined, differing in composition from said smoke suppressant, and being nitrogen-free.

2. A composition as claimed in claim 1, wherein the flame retardant agent is a member selected from the group consisting of alogenated compounds, metal hydrates, metal borates, antimony compounds, phosphorous compounds, and mixtures thereof.

3. A composition as claimed in claim 1, wherein the flame retardant agent is a member selected from the group consisting of di- ( 2-ethylhexyl) tetrabromophthalate, alumina trihydrate, magnesium hydroxide, antimony trioxide, zinc borate and alkarylphosphates . - 17 - 95673/2

4. A composition as claimed in claim 1, wherein the bicyclic phosphate compound is 2,6,7-trioxa-phosphobicyclo[2.2.2]-octane-4 -methanol-1 -oxide; or 2,6,7-trioxa-l-phosphobicyclo[2.2.2]-octane-4-methanol, acetate, 1-oxide.

5. A composition as claimed in claim 1, wherein the resin is a member selected from the group consisting of polyvinyl chloride, polystyrene and polyethylene, polypropylene and polybutylene homo- and copolymers.

6. A composition, as claimed in claim 5, wherein the resin is polyvinyl chloride.

7. A composition as claimed in claim 1, wherein the weight ratio of bicyclic phosphate compound to flame retardant agent lies in the range of about 1:25 to 20:1.

8. A composition as claimed in claim 1, wherein the mixture of bicyclic phosphate compound and flame retardant agent is provided in the resin composition at a level lying in the range of about 2 to 50 percent by weight of the overall composition.

9. A method for suppressing the tendency of polyvinyl halide, polyolefin or polystyrene resins to smoke under conditions of burning, comprising the step of incorporating therein an effective amount of a mixture comprising: a smoke suppressant comprising at least one bicyclic phosphate compound of the formula: - 18 - 95673/3 where X is OH, OR' or OC(0)R' ; R is H or a saturated or unsaturated straight-chain or branched-chain CxrC17 alkyl, R' is a saturated or unsaturated straight-chain or branched-chain d-Ci, alkyl; and a flame retardant agent as hereinbefore defined, differing in composition from said smoke suppressant, and being nitrogen- free .

10. A method as claimed in claim 9, wherein the flame retardant agent is a member selected from the group consisting of halogenated compounds, metal hydrates, metal borates, antimony compounds, phosphorous compounds, and mixtures thereof.

11. A method as claimed in claim 9, wherein the flame retardant agent is a member selected from the group consisting of di-{2-ethylhexyl) tetrabromophthalate, alumina trihydrate, magnesium hydroxide, antimony trioxide, zinc borate and alkarylphosphates .

12. A method as claimed in claim 9, wherein the bicyclic phosphate compound is 2,6,7-trioxa-phosphobicyclo[2.2.2]-octane-4-methanol-1-oxide; or 2,6,7-trioxa-l-phosphobicyclo[2.2.2]-octane-4-methanol, acetate, 1-oxide.

13. A method as claimed in claim 9, wherein the weight ratio of bicyclic phosphate compound to flame retardant agent lies in the range of about 1:25 to 20:1. - 19 - 95673/2

14. The composition of claim 1, and which is substantially free of ammonium compounds, amines, ureas, guanidines, guanamines, s-triazines, amino acids, peptides and salts thereof.

15. The composition of claim 1, and which consists essentially of said resin, said flame retardant agent, and said at least one bicyclic phosphate compound.

16. The composition of claim 1, in which X is OH and in which R is H.

17. The composition of claim 9, and which is substantially free of ammonium compounds, amines, ureas, guanidines, guanamines, s-triazines, amino acids, peptides and salts thereof.

18. The method of claim 9, in which said mixture consists essentially of said flame retardant agent and said at least one bicyclic phosphate. for the Applicant: WOLFF, BREGMAN AND GOLLER