ANTISTATIC PLASTICISERS

Abstract: This invention relates to antistatic plastic plasticisers for flexible polar polymers e.g. PVC comprising an alkoxyalkanol ester and a surfactant. The feature of the invention is that the specific combination now claimed shows a synergistic effect in its antistatic plasticising activity. The combination also reduces significantly the surface resistivity of such polymers.

Description: The present invention relates to an antistatic plasticiser for flexible, polar polymers such as plasticised polyvinyl chloride (PVC). In the context of the present invention polar polymers are those derived from monomers having dipole moments in the range required for compatibility with ester plasticisers. Flexible polar polymers such as synthetic nitrile rubbers, polychloroprene, chlorosulphonated polyethylene and plasticised PVC are well known to accumulate static electricity charges under certain conditions. Static electricity charges can represent a potential hazard especially if such PVC products are to be used in e.g. coal mine conveyor belts, hospital flooring and safety footwear. In view of this producers of formulations of such polymers have used antistatic agents to reduce build-up of static charges and to promote charge dissipation in their products. The antistatic agents commonly used are cationic, non-ionic or anionic in nature and generally fall under the following groups of materials: amides and amines; quaternary ammonium compounds; polyalkylene glycol derivatives; sulphates and sulphonates; and miscellaneous ethers and esters. It is also well known that some antistatic agents adversely affect the thermal stability of plasticised PVC. Such adverse effects are most notable when amines, amides and quaternary ammonium compounds are used as antistatic agents. It has now been found that by using a combination of a specific ester, a surfactant and an antistatic agent for flexible polar polymers having improved performance can be formulated. Accordingly the present invention is a flexible polar polymer formulation comprising a polar polymer and an antistatic plasticiser which comprises (i) a dicarboxylate ester derivable from a dicarboxylic acid and one or more hydroxy compounds of the general formula: R(OCH₂CH₂) n -OH wherein R is a C₁-C₄ alkyl group and n is an integer from 1-4, and (ii) a surfactant selected from an ethoxy alcohol and a monocarboxylic acid ester of a polyoxyethylene glycol. The dicarboxylic acid component of the diester in the antistatic plasticiser is suitably an acid selected from succinic, adipic, glutaric, azelaic and sebacic acids, and is preferably adipic acid. The hydroxy compound component of the diester in the antistatic plasticiser is suitably butoxyethoxy ethanol. Thus, the preferred diester component of the antistatic plasticiser is dibutoxyethoxy ethyl adipate (DBEEA). The diester component may be the sole plasticiser in the formulation or may be used in conjunction with other well known plasticiser esters such as e.g. dioctyl phthalate (DOP) which is a typical primary plasticiser component. The diester component is suitably present in the antistatic plasticiser in an amount of 40 to 95% w/w, preferably from 60 to 90% w/w with respect to the surfactant. Where the surfactant is a monocarboxylic acid ester, it is preferably a polyoxyethylene glycol mono-carboxylate, especially polyoxyethylene glycol mono-oleate. The polyethylene glycol moeity in the mono ester surfactant suitably has a molecular weight in the range of 350 to 460 which corresponds to between 8 and 10 oxyethylene units each molecule of the surfactant. By the term "ethoxy alcohol" is meant here and throughout the specification that the surfactant is an ether in which the ethoxy function represents a monoethoxy or polyoxyethylene group. In the case of a polyoxyethylene group, it suitably has up to 10 oxyethylene groups, preferably from 2-5 oxyethylene groups. Where the surfactant is a simple ethoxy alcohol, the alcohol moiety suitably has 1 to 20 carbon atoms and is a saturated, aliphatic monohydric alcohol. The monohydric alcohol preferably has 4 to 15 carbon atoms. Ethoxy-1-dodecanol (ethoxy lauryl alcohol), polyoxyethylene-1-dodecanol and mixtures thereof are preferred. The antistatic plasticiser is suitably present in the formulation in amounts from 10 to 80 parts, preferably from 10 to 50 parts per hundred parts of polar polymer resin (phr) in the formulation. The antistatic plasticiser can be added to the formulation at any stage during the compounding of the formulation. It is, however, essential to ensure that the antistatic plasticiser is uniformly distributed throughout the mass of the formulation. Typical flexible polar polymers which may be compounded with the antistatic plasticisers of the present invention include PVC, synthetic nitrile rubbers, polychloroprene and chlorosulphonated polyethylene. The antistatic plasticisers of the present invention may contain in addition minor amounts of conventional additives such as antioxidants. The present invention is further illustrated with reference to the following Examples. Examples A set of PVC formulations were prepared as follows and then tested for their surface resistivity using a method described in BS 3289, 1982 Appendix H (20°C ± 2°C, relative humidity 65% ± 5%). The results are tabulated in Table 1 below. PVC - Breon S125/14 (Registered Trade Mark) - 100 phr DOP - dioctyl phthalate (Primary plasticiser) Stabilizer - tribasic lead sulphate (5 phr) Lubricant - AC 629* Polyethylene (*ex Allied Chemical Corp) - (0.5 phr) Surfactant - Polyoxyethylene glycol monooleate [Nonex 30 (Registered Trade Mark)] Plasticiser - Dibutoxy ethoxyethyl adipate (DBEEA) The above results show that the combination of ester and surfactant now proposed significantly reduces the surface resistivity of PVC formulations. The thermal stability of these formulations was determined using a modified version of ISO thermal stability test (ISOR 305). The results are tabulated in Table 2 below.

Claims: A flexible polar polymer formulation comprising a polar polymer and an antistatic plasticiser which comprises (i) a dicarboxylate ester derivable from a dicarboxylic acid and one or more hydroxy compounds of the general formula: R(OCH₂CH₂) n -OH wherein R is a C₁-C₄ alkyl group and n is an integer from 1-4, and (ii) a surfactant selected from an ethoxy alcohol and a monocarboxylic acid ester of a polyoxyethylene glycol. A formulation according to claim 1 wherein the dicarboxylic acid component of the diester (i) is an acid selected from succinic, adipic, glutaric, azelaic and sebacic acids. A formulation according to claim 1 or 2 wherein the hydroxy compound component of the diester (i) is dibutoxyethoxy ethanol. A formulation according to any one of the preceding claims wherein the diester (i) is dibutoxyethyl adipate. A formulation according to any one of the preceding claims wherein the diester (i) is present in the antistatic plasticiser in an amount from 40 to 95% w/w with respect to the surfactant (ii). A formulation according to any one of the preceding claims wherein the polyoxyethylene glycol moiety in the monoester surfactant (ii) has a molecular weight in the range of 350 to 460. A formulation according to any one of the preceding claims wherein the surfactant (ii) is a polyoxyethylene glycol monooleate. A formulation according to any one of the preceding claims 1-5 wherein the surfactant (ii) is an ethoxy alcohol in which the alcohol moiety has 1-20 carbon atoms. A formulation according to claim 8 wherein the surfactant (ii) is selected from ethoxy-1-decanol, polyoxyethylene-1-decanol and mixtures thereof. A formulation according to any one of the preceding claims wherein the antistatic plasticiser is present in said formulation in an amount from 10 to 80 parts per hundred parts of the polar resin

Inventors: CLUTTERBUCK, PAUL GEOFFREY, WILSON, ALAN STUART
Applicants: BP CHEMICALS LIMITED
Application year: 1987
Main classification: C08K5
IPC codes: C08K5, C09K3, C08L101