WO1999060055A1

WO1999060055A1 - Method for reducing extractable heavy metals (lead) from halogenated polymer compositions

Info

Publication number: WO1999060055A1
Application number: PCT/US1999/010660
Authority: WO
Inventors: Richard F. Grossman
Original assignee: Hammond Group, Inc.
Priority date: 1998-05-15
Filing date: 1999-05-14
Publication date: 1999-11-25
Also published as: AU3990999A

Abstract

A metal phosphate is used in halogenated polymer compositions containing heavy metal stabilizers, such as lead, to reduce extractable heavy metals from molded polymer products when tested by the toxicity characteristic leaching procedure (TCLP) of 40 CFR 261.

Description

METHOD FOR REDUCING EXTRACTABLE HEAVY METALS (LEAD) FROM HALOGENATED POLYMER COMPOSITIONS

BACKGROUND OF THE INVENTION

Haiogenated polymers, such as chlorinated polyethylene

(CPE), polychloroprene (CR), polyvinyl chloride (PVC) and

chlorosulfonated polyethylene (CSPE), are commonly used for many

5 useful articles such as wire of cable insulation, electrical component

housings and electrical conductors. Insulated products include residential

and commercial building wire; portable power cord and fixture wires;

automotive primary (harness) wire; telephone and other communications

wires; instrument and appliance wires; motor lead wires, etc.

1 0 Compositions based on haiogenated polymers typically provide required

flame resistance, oil resistance, and resistance to environmental factors

such as ozone and ultraviolet light to a greater extent than would similar

nonhalogenated polymers (e.g., olefin polymers and copolymers) .

Therefore, the use of compositions based on haiogenated polymers in

1 5 useful products is widespread. The wire and cable industry has relied on insulating

haiogenated polymers containing heat stabilizers based on lead

compounds. Thus, electrically insulating CPE and CSPE compositions

usually include dibasic lead phthalate, dibasic lead phosphite, tribasic lead

sulfate, or lead stearate, among others, as heat stabilizers. With

chlorinated polyethylene or chlorosulfonated polyethylene, litharge and

red lead oxide are also used.

On June, 22, 1 990, Part 261 of CFR 40, Protection of

Environment, was amended to include (as Appendix II) Method 1 31 1 ,

Toxicity Characteristic Leaching Procedure (TCLP), as a prerequisite for

any solid waste to be landfilled as nonhazardous waste. When tested per

Method 1 31 1 , the solid waste must yield an extract containing less than

5.0 mg/l of lead. Thus, reduction in the level of lead extractables from

haiogenated polymers by the TCLP has been an objective in the above

mentioned industries.

SUMMARY OF THE INVENTION

The present invention is directed to haiogenated polymer

compositions containing heavy metal stabilizers, such as lead compounds,

having reduced extractable heavy metal. It has been found that the

extractable lead levels of a molded haiogenated polymer composition

having a lead stabilizer can be reduced by adding a metal phosphate in an

effective amount to the polymer composition. In a preferred embodiment the extractable lead of lead-

stabilized CPE, CR, PVC or CSPE polymer is substantially improved by

including a minor amount of about 0.2 to 5 parts, or up to about

20 parts, of a metal phosphate per 1 00 parts of polymer. In particular,

calcium phosphate is preferred. However, other alkali or Group II metal

phosphates can be used.

The invention provides for greatly reduced extractable lead

on exposure of molded compositions to environmental landfill conditions.

In particular, it has been found that a significant reduction of extractable

lead from haiogenated polymer compositions can be achieved by adding

a metal phosphate to the polymer in an effective amount to reduce

extraction of the heavy metals when exposed to the toxicity

characteristic leaching procedure of 40 CFR 261 . The function of the

metal phosphate, such as calcium phosphate, as an additive to reduce

extractable lead from haiogenated polymer compositions is considered

unexpected and surprising. Furthermore, it has been found that the metal

phosphates reduce the toxicity of lead when blended therewith. These

blends also appear to be less soluble in digestive fluids.

The invention is particularly applicable to haiogenated

polymer compositions having lead stabilizers in electric wire or cable

applications. In a broader aspect, the invention is applicable to other

heavy metals, such as barium and cadmium, in stabilized haiogenated

polymer products. The invention in these broader aspects, as well as specific embodiments and other parameters, may be further understood

with reference to the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

A. Haiogenated Polymer

Halogen-containing polymers or resins which are employed

and which illustrate the principles of this invention include chlorinated

polyethylene, chlorosulfonated polyethylene, polychloroprene, polyvinyl

chloride, and other vinyl halide resin types. Haiogenated polymer or vinyl

halide resin, as understood herein, and as appreciated in the art, are

common terms and are adopted to define those resins or polymers usually

derived by polymerization or copolymerization of vinyl monomers

including vinyl chloride with or without other comonomers such as

ethylene, propylene, vinyl acetate, vinyl ethers, vinylidene chloride,

methacrylate, acrylates, styrene, etc. A simple case is the conversion of

vinyl chloride H₂C=CHCI to polyvinyl chloride (CH₂C=CHCI)_n wherein the

halogen is bonded to the carbon atoms of the carbon chain of the

polymer. Other examples of such vinyl halide resins would include

vinylidene chloride polymers, vinyl chloride-vinyl ester copolymers, vinyl

chloride-vinyl ester copolymers, vinyl chloride-vinyl ether copolymers,

vinyl chloride-vinylidene copolymers, vinyl chloride-propylene copolymers,

chlorinated polyethylene, and the like. Of course, the vinyl halide

commonly used in the industry is the chloride, although others such as bromide and fluoride may be used. Examples of the latter polymers

include polyvinyl bromide, polyvinyl fluoride, and copolymers thereof.

B. Heavy Metal Stabilizers

Heavy metal stabilizers in haiogenated polymer compositions

are well known. These metal compounds serve to capture HCI liberated

during heat processing of the vinyl halide resin composition into its final

shape. The heavy metal can be lead, cadmium or barium, for example.

The lead stabilizers comprise litharge, red lead, dibasic lead phthalate,

dibasic lead phosphite, tribasic lead sulfate, tetrabasic lead sulfate,

tribasic lead maleate, tetrabasic lead fumarate, basic lead carbonate and

dibasic lead stearate. The stabilizers may include heavy metal salts of a

carboxylic acid, advantageously a C₈-C₂₄ carbon link monocarboxylic acid

such lauric, oleic, stearic, octoic, or similar fatty acid salts. Mixed metal

salts of such acids, and their preparation, are familiar to those skilled in

the art to which this present invention pertains.

C. Metal Phosphates

The metal phosphates suitable for use in accordance with

the principles of this invention may be derived from a broad ciass of

compounds. In short, the term "metal phosphate" is used hereinafter to

define a member of this class. The metal salts are alkali or alkaline earth

metal, and Group II or lla cations, which are exemplified by calcium,

magnesium, zinc, strontium and barium. Preferably, the metal cation is

calcium and especially preferred calcium phosphates include CaHP0₄, mixtures of CaHP0₄, and Ca₃(P0₄)₂ which are essentially ground

phosphate rock. Alkali metal phosphates, such as Na₂HP0₄, can be used.

Other alkali and alkaline metal earth metal phosphates may be included.

D. Amounts of Components

Broad ranges of components of the haiogenated polymer

compositions may be employed in the invention. In general, the metal

phosphate is used in an effective amount in the haiogenated polymer

composition to reduce extractable lead. Particularly useful compositions

of the invention are achieved containing about 0.5 to about 5 parts, up

to about 40 parts, of the heavy metal compound heat stabilizer, about

0.2 to about 5 parts, up to about 20 parts, of the metal phosphate, said

parts on the basis of 1 00 parts of the haiogenated polymer. The

compositions of the present invention can also include various additional

compounds including lubricants for providing the polymer or resin with

lubricity and plasticizers of the phthaiic ester or fatty acid ester type,

hydrocarbon resins or chlorinated olefins or paraffins. Other additives may

include auxiliary stabilizers, antioxidants, light stabilizers, pigments, dyes

or extenders. The compositions may optionally contain an inorganic acid

acceptor, such as various hydrotalcites and Type A hydrous zeolites, or

coordinating multidentate metal blend ligands, such as 1 ,3-diketone, or

an antioxidant such as bisphenol A, or a phosphite costabilizer such as

diphenyl decyl phosphite. Fillers may be added including coarse ground

limestone, fine ground limestone, clay, talc or other particulate fillers. The advantages of this invention and its operating

parameters will be further understood with reference to the following

detailed examples.

EXAMPLE 1

A cable jacket for use in power supply to electric

locomotives consisted of 1 00 parts chlorosulfonated polyethylene

elastomer (ASTM designation CSM, trade name Hypalon), 80 parts kaolin

clay, 20 parts carbon black, 30 parts trioctyl trimellitate plasticizer,

44 parts litharge stabilizer, and minor amounts of curatives. After

extrusion as a cable jacket, and vulcanization, this compound yielded

TCLP lead extraction of 90-100 mg/l. The TCLP analysis of 40 CFR 261

is incorporated herein in its entirety by reference.

EXAMPLE 2

The cable jacket of Example 1 was made employing the

same composition except that 22 parts of calcium phosphate were added

to the composition and, after extrusion as a cable jacket and

vulcanization, the product yielded TCLP lead extraction of 22 mg/l. Thus,

employing the metal phosphate of this invention in the haiogenated

polymer composition enabled the reduction of extractable lead from

90-1 00 mg/l to 22 mg/I.

EXAMPLE 3

The cable jacket of Example 1 was made and the identical

procedures were followed except that 44 parts of litharge were replaced with 25 parts of red lead. TCLP lead extraction of this cable jacket was

1 0 mg/l.

EXAMPLE 4

The procedure of Example 3 was repeated except that

1 2.5 parts of calcium phosphate was added to the formulation and, after

extrusion as a cable jacket and vulcanization, the product yielded TCLP

lead extraction of 3.6 mg/l. Thus, employing a metal phosphate of this

invention enabled the reduction of extractable lead from 1 0 mg/l to

3.6 mg/l.

EXAMPLE 5

Chloropolyethylene wire insulation product consisting of

1 00 parts chloropolyethylene, 60 parts clay, 40 parts calcium carbonate,

20 parts ester plasticizer, 1 2 parts litharge stabilizer, plus antioxidant and

cross linking agents was made. After extrusion and vulcanization, the

product yielded TCLP lead extraction values of 20-30 mg/l which is above

the limiting value of 5 mg/l needed for qualification as nonhazardous

waste.

EXAMPLE 6

The procedures of Example 5 were repeated except that

litharge was replaced with a preblended stabilizer containing 60% by

weight litharge and 40% by weight calcium phosphate (CaHP0₄) . The

product yielded TCLP lead extraction values of 2-3 mg/l, thereby

qualifying as nonhazardous waste. Thus, this invention enables the reduction of hazardous waste materials and greatly reduces the cost of

transportation to a suitable recycling site.

EXAMPLE 7

Dibasic lead phthalate was found to have an oral LD50 value

in rats of between 2000-5000 mg/kg body weight, placing it in

Category III (formerly known as Slightly Toxic). A blend of 67% dibasic

lead phthalate, 33% zinc phosphate, was found to have an oral LD50

value in rats of greater than 5000 mg/kg body weight, corresponding to

Category IV (formerly known as Nontoxic). It is not believed that any

lead stabilizer has previously been found to have an oral LD value above

5000 mg/kg. Accordingly, this invention offers the advantage of

producing nontoxic lead stabilizer systems. It has also been found that

the blends appear to be less soluble in digestive fluids which would

reduce the toxicity in animals where compositions containing lead

stabilizer components were ingested.

EXAMPLE 8

A composition was prepared comprising polyvinyl chloride

(PVC) 100 parts by wt., calcium carbonate 40, di-iso-decyl phthalate 65,

stearic acid 0.3, and tribasic lead sulfate 4. This composition is routinely

used as a nonmetallic (Underwriters Laboratories Type NM) jacket to

cover residential building wire. This composition was mixed to a

homogeneous state and extruded, simulating wire manufacture. The

composition yielded TCLP extraction of 7 mg/l. EXAMPLE 9

The composition of EXAMPLE 8 was mixed using a blend of

4 parts of tribasic lead sulfate with 2 parts of Na₂HP0₄ in place of the

above 4 parts of pure tribasic lead sulfate. This composition yielded

TCLP extraction of 1 .5 mg/l.

The above data establishes that minor amounts of an alkali

or alkaline earth metal, Group II and Group lla metal phosphate, when

employed as an additive in haiogenated polymer compositions reduces

extractable lead, as a heavy metal, of the lead stabilizer employed in the

compositions. The above examples are not intended to limit the

invention. In accordance with the principles, other haiogenated polymers

that are stabilized with heavy metals may be landfillable as

non-hazardous waste by adding an effective quantity of the metal

phosphate to pass the TCLP as provided in 40 CFR 261 .

Having described this invention, its advantages and

operating parameters, it will be obvious to persons of ordinary skill in the

art, in view of the above description, that variations hereof may be made

without departing from the spirit and scope thereof.

WHAT IS CLAIMED IS:

Claims

1 . A haiogenated polymer composition comprising a

haiogenated polymer, a heavy metal compound stabilizer for said polymer

and a metal phosphate as an additive in an effective amount to reduce

extraction of heavy metal when said composition is exposed to the

toxicity characteristic leaching procedure of 40 CFR 261 .

2. The composition of claim 1 wherein said haiogenated

polymer is selected from the group of polyvinyl chloride, polychloroprene,

chlorinated polyethylene and chlorosulfonated polyethylene.

3. The composition of claim 1 wherein said metal phosphate is

calcium phosphate.

4. The composition of claim 1 wherein said heavy metal

compound is selected from the group consisting of litharge, red lead,

dibasic lead phthalate, dibasic lead phosphite, tribasic lead sulfate,

tetrabasic lead sulfate, tribasic lead maleate, tetrabasic lead fumarate,

basic lead carbonate and dibasic lead stearate.

5. The composition of claim 1 wherein said heavy metal

compound stabilizer is present in an amount from about 0.5 to about

40 parts and said metal phosphate is present in an amount from 0.2 to

about 20 parts and said haiogenated polymer is present in amount of

about 1 00 parts.

6. The composition of claim 1 wherein the metal phosphate is

selected from the group consisting of an alkali metal phosphate and an

alkaline earth metal phosphate.

7. A haiogenated polymer composition comprising a polymer or

copolymer of vinyl chloride, a lead stabilizer selected from the group

consisting of litharge, red lead, dibasic lead phthalate, dibasic lead

phosphite, tribasic lead sulfate, tetrabasic lead sulfate, tribasic lead

i maleate, tetrabasic lead fumarate, basic lead carbonate and dibasic lead

stearate, and a metal phosphate as an additive in an effective amount to

reduce extraction of the lead when said composition is exposed to the

toxicity characteristic leaching procedure of 40 CFR 261 .

8. The composition of claim 7 wherein the metal phosphate has

a metal cation selected from the group consisting of calcium, magnesium,

strontium, barium and zinc.

9. The composition of claim 7 wherein said metal phosphate is

in an amount of about 0.2 to about 20 parts and the lead compound is

in an amount of about 0.5 to about 40 parts per 1 00 parts resin.

10. The composition of claim 7 wherein said metal phosphate is

calcium phosphate.

1 1 . A method for reducing extractable heavy metal from a

molded product of a haiogenated polymer composition comprising

providing a haiogenated polymer composition containing a

heavy metal compound stabilizer for said polymer to produce a molded

product,

adding a metal phosphate as an additive in an effective

amount to reduce extraction of the lead when said molded product is

exposed to the toxicity characteristic leaching procedure 40 CFR 261 .

1 2. The method of claim 1 1 wherein said heavy metal compound

is selected from the group consisting of litharge, red lead, dibasic lead

phthalate, dibasic lead phosphite, tribasic lead sulfate, tetrabasic lead

sulfate, tribasic lead maleate, tetrabasic lead fumarate, basic lead

carbonate and dibasic lead stearate, and a metal phosphate as an additive

in an effective amount to reduce extraction of the lead when said

composition is exposed to the toxicity characteristic leaching procedure

of 40 CFR 261 .

1 3. The method of claim 1 1 wherein said heavy metal stabilizer

is present in an amount from about 0.5 to about 40 parts and said metal

phosphate is present in an amount from 0.2 to about 20 parts and said

haiogenated polymer is present in an amount of about 1 00 parts.

14. The method of claim 1 3 wherein said metal phosphate is

calcium phosphate.

1 5. The method of claim 1 2 wherein the metal phosphate is

selected from the group consisting of calcium, magnesium, strontium,

barium and zinc.