AU535493B2 - Improved rigid vinyl chloride polymer compositions - Google Patents

Description

IMPROVED RIGID VINYL CHLORIDE POLYMER COMPOSITIONS

BACKGROUND OF THE INVENTION Rigid vinyl chloride polymer compositions are well known. Such materials normally contain small amounts of copolymers of styrene and acrylonitrile, styrene and methacryiates and other alkyl alkacrylate processing aids. Typical compositions are described in U.S. Patents 2,646,417 and 2,791,600. These compositions find many applications as structural plastics, and while they have resistance to burning, under intense conditions such polymers do burn and form undesirable smoke. U.S. Patent 4,053,453 provides rigid vinyl halide polymer compositions containing copper oxalate and amine molybdates that suppress smoke formation when such polymers burn. In many applications these rigid compositions may be deficient in impact resistance, and it is desirable to add impact modifiers to the compositions. Unfortunately many of these materials contribute to smoke formation during burning of the compositions. Improved vinyl halide compositions which are impact resistant and have improved resistance to fire and have low smoke generation are desired.

SUMMARY OF THE INVENTION Rigid vinyl halide polymer compositions, substantially free of liquid ester type plasticizers, and containing styrene copolymer process modifiers, copper oxalate and an amine molybdate have improved impact resistance when there is also present small amounts of copolymers of ethylene and vinyl acetate and graft copolymers of methacryiates, butadiene, and styrenes (MBS) polymers, which compositions form less smoke than when either of these impact modifiers alone is included in the compositions. DETAILED DESCRIPTION The vinyl halide polymers used in this invention include homopolymers, copolymers and blends of homopolymers and/or copolymers. Useful vinyl halides include vinyl chloride and vinylidene chloride polymers that contain up to about 50% by weight of at least one other olefinically unsaturated monomer, more preferably at least one other vinylidene monomer (i.e., a monomer containing at least one terminal CH₂=C< group per molecule) copolymerized therewith, even more preferably up to about 20% by weight of such monomers. Suitable monomers include α-olefins containing from 2 to 12 carbon atoms , more preferably from 2 to 8 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene, 1-hexene, 4-methyl-1-pentene and the like; dienes containing from 4 to 10 carbon atoms including conjugated dienes as butadiene, isoprene, piperylene and the like; ethylidene norbornene and dicyclopentadiene; vinyl esters and allyl esters such as vinyl acetate, vinyl chloroacetate, vinyl propionate, vinyl butyrate, vinyl laurate, vinyl benzoate, allyl acetate and the like; vinyl aromatics such as styrene, α-rnethyl styrene, chlorostyrene, vinyl toluene, vinyl naphthalene and the like; vinyl and allyl ethers and ketones such as vinyl methyl ether, allyl methyl ether, vinyl isobutyl ether, vinyl n-butyl ether, vinyl chloroethyl ether, methyl vinyl ketone and the like; vinyl nitriles such as acrylonitrile, methacrylonitrile and the like; cyanoalkyl acrylates such as α-cyanomethyl acrylate, the α-, β- and γ-cyanopropyl acrylates and the like; olefinically unsaturated carboxylic acids and esters thereof, including α,β-olefinically unsaturated acids and esters thereof such as acrylic acid, methacrylic acid, ethacrylic acid, methyl acrylate, ethyl acrylate, chloropropyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, glycidyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, hexylthioethyl acrylate, methylmethacrylate, ethyl methacrylate, butyl methacrylate, glycidyl methacrylate and the like wherein the alkyl groups contain 1 to 12 carbon atoms, and including esters of maleic and fumaric acid and the like; amides of the α,β-olefinically unsaturated carboxylic acids such as acrylamide, methacrylamide, and the like; divinyls, diacrylates and other polyfunctional monomers such as divinyl benzene, divinyl ether, diethylene glycol diacrylate, ethylene glycol dimethacrylate, methylene-bis-acrylamide, allyl pentaerythritol, and the like; and bis(β-haloalkyl) alkenyl phosphonates such as bis(β-chloroethyl) vinyl phosphonate and the like . A group of particularly useful comonomers include 1-olefins containing from 2 to 8 carbon atoms; vinyl esters and allyl esters; olefinically unsaturated carboxylic acids and esters thereof, especially α,β-olefinically unsaturated acids and esters thereof; esters of maleic and fumaric acid and the like; amides of α,β-olefinically unsaturated carboxylic acids; and vinylidene or vinyl chloride.

These vinyl chloride polymers normally are high molecular weight polymers having a specific viscosity greater than 0.4 measured as a 0.4% solution in nitrobenzene.

The vinyl chloride polymers may be prepared by any method known to the art such as by emulsion, suspension, bulk or solution polymerization. The additive compounds may be mixed with the polymer emulsion, suspension, solution or bulk mass before monomer recovery and/or drying. More preferably the compounds may be mixed with dry granular or powdered polymers. The polymers and compounds may be mixed thoroughly in granular or powder form in apparatus such as a Henschel mixer or the like. Alternatively, this step may be eliminated and the mixing done while the polymer mass is fluxed, fused and masticated to homogeneity under fairly intensive shear in or on a mixer apparatus having its metal surface in contact with the material. The fusion temperature and time will vary according to the polymer compositions and level of additive compounds but will generally be in the range of about 300 to 400°F. and 2 to 10 minutes.

The vinyl chloride polymers may also be mixed with standard compounding ingredients known to those skilled in the art, plasticizers, lubricants, stabilizers, fillers, colorants, processing aids, and the like. While these compounds are most effective in vinyl chloride polymers substantially free of plasticizers, they are also of value in reducing smoke formation of plasticized vinyl chloride polymers.

The copper oxalate and amine molybdates are normally used in powder form in amounts greater than about 0.1 part total per 100 weight parts of vinyl halide polymer, more preferably from about 1 to about 20 total weight parts per 100 weight parts of vinyl chloride polymers. From about 1 to about 10 total weight parts is a very practical range providing a good balance of desirable properties in the compounds. The useful ratio of copper oxalate to amine molybdate is from about 1:10 to 10:1 on a weight basis. The copper oxalate and amine molybdate are readily mixed with the vinyl chloride polymers in powder form as is any other powder ingredient mixed with vinyl chloride polymers, masterbatched and the like, as is well known to those skilled in the art; i.e., U.S. Patent No. 4,053,453.

Any amine molybdate may be used. Typical amine molybdates are described in U.S. Patent No. 4,053,455. Amine molybdates are typically produced by reacting an amine with MoO₃, molybdic acid or a molybdenum salt such as ammonium molybdate, ammonium di molybdate, ammonium heptamolybdate (also known as ammonium paramolybdate) , ammonium octamolybdate , sodium molybdate or the like. Excellent results have been obtained using ammonium dimolybdate, ammonium heptamolybdate, sodium molybdate, and the commercial "molybdic acid" which primarily consists of one or more ammonium molybdates.

Amines suitable for preparing the organoamine molybdates used in this invention may contain from 1 to 40 carbon atoms and from 1 to 10 primary, secondary or tertiary amine groups or a mixture thereof; more preferably from 1 to 20 carbon atoms and 1 to 4 primary amines or heterocyclic secondary amine groups. Examples of amines include aliphatic, alicyclic, aromatic and heterocyclic amines. Aliphatic amines include ethylamine, ethylenediamine, 1,2-proρanediamine, 1, 3-τ-propanediamine, 1,4-butanediamine, 2-methyl-1,2-propanediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, 1,10-decanediamine, 1,12-dodecanediamine and the like. Also, aliphatic polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, bis (hexamethylene) triamine, 3,3'-iminobispropylamine, quanidine carbonate, and the like. Other suitable amines include alicyclic diamines and polyamines such as 1,2-diaminocyclohexane, 2',4-diamino-1-propyl4-methylcyclohexane, and the like; aromatic amines as aniline, and naphthylamine; and heterocyclic amines such as melamine, N,N-dimethylaniline, pyridine, piperazine; hexamethylenetetraamine; 2,2,4-trimethyl decahydroquinoline; 2,4,6-tri(morpholino)-1,3,5-triazine; and N-(aminoalkyl)-piperazines wherein each alkyl group contains from 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms, such as N-(2-aminoethyl)piperazine, and the like. Examples of suitable polymeric amines include polyethyleneimine, polyvinylpyridine, polyvinyl pyrrolidine, and poly (2,2,4-trimethyl-1,2-dihydroquin olyl). Excellent results are obtained using melamine, piperazine, and alkyl amines wherein the alkyl contains 1 to 8 carbon atoms.

Useful melamine and substituted melamines have the formula

wherein X is hydrogen or an alkyl, alicyclic, aralkyl, alkaryl, aryl or heterocyclic group containing from 1 to 10 atoms of C, O, S and/or N. Two X's on each of one or more nitrogen atoms may also be joined together to form a heterocyclic ring such as a morpholino group in 2,4,6-tri(morpholino)-1,3,5-triazine. Other examples of suitable substituted melamines include N,N',N''-hexaethylmelamine; 2-anilino-4-(2',4'-dimethylanilino)-6-piperidino-1,3,5-triazine; and 2,4,6-tri(N-methylanilino)-1,3,5-triazine. The amine molybdate normally contains from about 1 to 2 moles of molybdenum per mole of amine.

The amine molybdates used in this invention may be in the form of polycrystalline or amorphous fine powders, for example with an average particle size from about 0.01 to about 800 microns, more preferably from about 0.1 to about 200 microns, and even more preferably from about 0.5 to about 50 microns. Supports such as SiO₂, Al₂O₃ and the like may be used for the smoke retardant additives.

The styrene copolymer processing aid for use in the compositions of the invention may be made from monomers containing as two essential monomers, 50 to 90% by weight of styrene or a nuclear or alpha-substituted styrene such as chloro, alkyl, and alkoxy styrenes such as chlorostyrene, vinyl toluene, α-methyl styrene, methoxystyrene and the like, with from 10 to 50% by weight of an acrylicnitrile such as acrylonitrile, methacrylonitrile, ethacrylonitrile, and the like. Other vinylidene monomers containing at least one terminal CH₂ < group may be included in amounts up to about 20% by weight of the total monomers. These polymers are described in U.S. 2,646,417. The styrenealkacrylate copolymers normally contain as two essential monomers, from 75 to 25 weight percent of styrene, a nuclear or α-substituted derivative such as chlorostyrene, vinyl toluene, α-methyl styrene, methσxystyrene and the like, and from 25 to 75 weight percent of an aliphatic alicyclic or aromatic methacrylate. Useful are alkyl methacryiates and ethacrylates wherein the alkyl group contains 1 to 8 carbon atoms, alicyclic methacryiates such as cyclohexyl methacrylate and the like, other vinylidene monomers containing at least 1 terminal CH₂< group in amounts up to 20 weight percent may be included. Normally the copolymer contains 60 to 40 weight percent styrene and 40 to 60 weight percent methyl methacrylate. Acrylate materials also may be used such as copolymers of methyl methacrylate and ethyl methacrylate substituted for the styrene copolymers. These polymers generally have molecular weights above about 40,000. The amounts used are 1 to 10 weight parts per 100 weight parts of vinyl chloride polymer.

The MBS impact modifiers are alkyl alkacrylate equivalents of ABS graft polymers and are well known. These materials are readily prepared for example by grafting methyl methacrylate and styrene onto a butadiene polymer substrate, which may be a copolymer of butadiene and a minor proportion of styrene. Other styrene derivatives such as α-methyl styrene, chlorostyrene, methoxy styrene and the like may be employed and other alkyl alkacrylates such as methyl met: late, methyl ethacrylate, butylethacrylate, and as described hereinabove may be employed. Norma these butadiene polymers contain greater than 5C parts of butadiene with the remainder being from weight parts to about 50 weight parts of a vinyl monomer containing at least one terminal CH₂< g for example, 10 to 50 parts of sytrene. At leas of the styrene and the alkyl alkacrylate are gra onto the butadiene polymer substrate. Proportio; monomer can be from about 20 to 90% of methyl me acrylate and styrene with 80 to 10 parts of the substrate. The styrene normally is the predomina monomer. More usually, the proportions are 30 to methyl methacrylate and styrene and 70 to 40 part butadiene polymer. A typical formulation would b polymerizing 20 parts of methyl methacrylate and parts of styrene onto 60 parts of a copolymer of parts of butadiene polymerized with 25 parts of s Cross-linking agents may be used in either the sur or in the graft polymerization stage, and such mat include for example diallyl acrylate, divinyl benz and other well known difunctional cross-linking ag normally in amounts up to 2 weight parts per 100 c other monomers. The MBS polymers are generally a ture of the rubber particles dispersed in a styren methyl methacrylate matrix, the styrene and methyl acrylate being grafted onto the elastomeric butadi polymer substrate.

The ethylene-vinyl acetate (EVA) copolyme impact improvers are also well known and such copo] mers prepared by methods known to those skilled in art contain from 5 to 50% of vinyl acetate copolyme with ethylene. Use of copolymers containing the lo amounts of vinyl acetate result in less smoke forma These copolymers normally contain more than 5% of v acetate monomer, and more preferably contain 15 to 40% vinyl acetate in the copolymers.

As to the proportion of EVA/MBS, excellent results have been obtained at 8:4, 7:3 and 6:2. Preferably of the two components there is used 60 to 80 weight percent EVA and 40 to 20 weight percent of MBS. Although improvement is observed when the mixture contains greater than 50 percent EVA, amounts larger than 90 weight percent are not desired. The total amount of the two modifiers used is an amount of at least 3 up to 15 weight parts per 100 weight parts of vinyl halide polymer, more preferably 6 to 12 weight parts. The process modifiers and impact improvers are readily mixed with the vinyl halide polymers, copper oxalate and amine molybdate by any of those techniques well known to those skilled in the art.

In testing for flame retardants the following procedure is used.

Smoke retardation may be measured using an NBS Smoke Chamber according to procedures described by Gross et al, "Method For Measuring Smoke from Burning Materials", Symposium on Fire Test Methods - Restraint & Smoke 1966, ASTM STP 422, pp. 166-204. Maximum smoke density (D_m) is a dimensionless number and has the advantage of representing a smoke density independent of chamber volume, specimen size or photometer path length, provided a consistent dimensional system is used. Maximum rate of smoke generation (R_m) is defined in units of min ^-1. Percent smoke reduction is calculated using this equation:

The term "D_m/g" means maximum smoke density per gram of sample. D_m and other aspects of the physical optics of light transmission through smoke are discussed fully in the above ASTM publication. In the following Examples, there is reported the D_m/g, maximum optical density/gram sample observed with a vertical light path in the National Bureau of Smoke Chamber (NBS). D_m is maximum optical density according to Gross. The NBS smoke chamber and its use are described by Gross et al in fire test methods ASTM STP 422, 1967, Pages 166-206. The NBS D_m/g smoke numbers reported are in the flaming or nonflaming mode. The D_s values are instantaneous smoke density at a given time such as 90 seconds and 4 minutes. Refer to ASTM E662-79.

To demonstrate the practice of the invention and various embodiments, a series of compounds were prepared using the following general formulation: 100 weight parts of poly (vinylchloride) having an inherent viscosity (IV) of 0.9 measured by ASTM D1243-66; 2 weight parts of a copolymer of 78 weight percent styrene and 22 weight percent acrylonitrile, 1.25 weight parts of a wax ester lubricant having an ASTM D566/49 drop point of 100-105°C, a density at 20°C of 1.01 to 1.03 and an ASTM D1387/55T saponification value of 100115 (American Hoechst), 1.25 weight parts of saturated fatty acid ester lubricant having a drop point of 122-125°F, viscosity of 185 cp at 140°F, specific gravity of 0.921 at 104°F and refractive index of 1.450 to 1.453 (Henkel, Inc.); 4 weight parts of dibutyl tin-bis-octyl thio glycollate, 6 weight parts titanium dioxide pigment, 2 weight parts copper oxalate, 2 weight parts of amine molybdate, and EVA and/or MBS modifiers in weight parts as indicated in the tables below. The EVA contains 25 weight parts vinyl acetate. The MBS contains 20 weight parts each of styrene and methyl methacrylate grafted onto a copolymer of 75 weight parts butadiene-1,3 and 25 weight parts of styrene. TABLE I

EVA (Wt.Pts.) 0 4 6 8 12 MBS (Wt.Pts.) 12 8 6 4 0 DM/gm. 22 20 19 13 16 Ds-90 sec. 47 50 46 32 44 Ds-4 min. 230 230 185 140 185

The improved results obtained are readily apparent with the presence of EVA and quite unexpectedly the mixture of EVA and MBS at 8 parts EVA and 4 parts MBS shows an unexpected synergistic result better than EVA or MBS alone. Table 1 results are averages of either two or three tests.°

Another series of compounds were prepared to the same recipe above, but with varying amounts of EVA and MBS. The test results obtained were as follows:

In Table II the results are the average of the two lists.

° Two tests are run - if the results don ' t reproduce within about 10% , a third is run.

TABLE II

EVA Wt. Pts. 6 6 10 10

MBS Wt. Pts. 2 6 2 0

Izod Impact 2.3/13.2 - - - /17.9 2.8/1.2 2.2/1.1

Dm 198 278 275.5 343

Dm/gm 13.85 16.75 17.1 21.25

Ds-90 sec. 35.5 33.5 31 40.5

Ds-4 min. 143 177.5 169 212

When the above examples are repeated with copolymers of 75% styrene with 25% methyl methacrylate, or 95% methyl methacrylate and 5% ethyl methacrylate used in place of the styrene/acrylonitrile copolymer, and with other MBS polymers as described hereinabove and EVA polymers as described hereinabove, similar improvement in smoke formation is observed.

Claims (7)

1. An improved flame resistant low smoke generating vinyl chloride polymer composition having improved impact resistance comprising a major proportion of a vinyl chloride polymer, a processing aid selected from the group consisting of styrene copolymers and alkyl acrylate copolymers, flame retardant amounts of copper oxalate and an amine molybdate, an ethylene-vinyl acetate copolymer and a graft polymer of a styrene and alkyl alkacrylate onto a butadiene polymer.

2. A composition of Claim 1 wherein the vinyl chloride polymer is polyvinyl chloride, the styrene copolymer is a copolymer of a major proportion of styrene with acrylonitrile and the graft polymer is a graft of styrene and methyl methacrylate onto a butadiene polymer.

3. A composition of Claim 1 wherein the styrene copolymer is a copolymer of a major proportion of styrene with methyl methacrylate.

4. A' composition of Claim 2 wherein the styrene/acrylonitrile copolymer is present in amounts of about 1 to 10 weight parts per 100 weight parts of PVC, there is about 1 to 10 total weight parts of copper oxalate and amine molybdate, and 3 to 15 weight parts of the ethylene-vinyl acetate copolymer and graft polymer.

5. A composition of Claim 4 wherein the amine molybdate is melamine molybdate present in a ratio of 1:10 to 10:1 to copper oxalate and the ratio of ethylene vinyl acetate copolymer to the graft polymer is 2:10 to 10:2.

6. A composition of Claim 5 wherein the ethylene-vinyl acetate copolymer contains about 15 to 40 weight percent copolymerized vinyl acetate and the ratio of the copolymer to graft polymer is from 4:8 to 10:2.

7. A composition of Claim 6 wherein the ratio of copolymer to graft polymer is from about 4:8 to about

8:4 and the graft polymer contains about 15 to 25 weight parts each of styrene and methyl methacrylate polymerized in the presence of about 70 to 50 weight parts of butadiene copolymer containing up to about 35 weight parts styrene .