Flame retardant ABS compositions incorporate an effective amount of halogenated unsymmetrical higher alkyl bisphenoxy alkane and an enhancing agent.

SUGGESTED CITATION
Flame Retardant ABS Resin Composition, E. J. Termine, N. A. Favstritsky, and D. M. Borden, United States Patent No. 4,829,118.
Available at: http://terminegroup.com/archives/233

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a non-blooming flame retardant ABS resin composition and more particularly to an ABS resin composition incorporating halogenated unsymmetrical higher alkyl bisphenoxy alkanes. 2. Description of the Art

Traditionally, most flame retardants, although efficient in their function of retarding the rate of combustion in a resin system, have a tendency to affect adversely one or more key properties of the resin. For example, many flame retardant additives tend to reduce impact strength of the resin; to migrate from the resin composition resulting in a phenomenon known as “bloom”; to plasticize the resin composition adversely, thus lowering the heat deflection temperature; or to degrade when exposed to indoor and outdoor light.

It is, therefore, essential that flame retardant agents be specifically tailored to the resin system so that in addition to their role as flame retardants, they will also enhance the desirable characteristics of the resin composition. Those skilled in the art well know that the selection of such an application specific flame retardant is unpredictable at best. Therefore, even if a given agent may exhibit utility in a particular resin system, there is no guarantee that this agent will have any use at all with other resins.

Acrylonitrile-butadiene-styrene (“ABS”) thermoplastics offer a good balance of physical and mechanical properties such as good abuse resistance, heat resistance, moldability, stain resistance, chemical resistance and surface hardness. Typically ABS thermoplastics are used in a wide variety of applications because of their properties and moderate costs. For example, ABS thermoplastics are used by telephone equipment, electronic, and automotive manufacturers who require materials of high impact strength.

ABS thermoplastics are derived from acrylonitrile, butadiene and styrene. Some of the properties of typical ABS resins are described on pages 1-68 of Harper’s Handbook of Plastics and Elastomers” published by McGraw-Hill Book Company in 1975.

A number of flame retardants have been described for ABS resins in the art. For example, the following materials have all been used in various ABS systems: bis(tribromophenoxy)-ethane, bis(pentabromophenoxy)-ethane, octabromodiphenyl oxide, decabromodiphenyl oxide, tetrabromobisphenol-A, bis(tribromophenoxyethyl)-tetra bromobisphenol A ether. Among the prior art specifically dealing with flame retarding ABS resins are U.S. Pat. No. 4,016,139; and U.S. Pat. No. 4,567,218, and the references cited therein.

The foregoing flame retardant agenst for ABS plastics have not been entirely satisfactory because of problems of bloom, thermal migration, heat instability, ultraviolet light instability, discoloration, or adverse effects on properties such as impact strength and flowability.

Many applications of ABS resins with flame retardant agents require that certain key properties be maintained. Examples of key properties include impact strength, light stability and retention of surface aesthetic properties. In particular, manufacturers of computer housings desire a thermoplastic ABS resin which is flame retardant, light stable, and resistant to bloom.

It is well known in the art to use various bromine containing compounds as flame retardant agents. The compositions obtained using these various bromine containing compounds have a tendency to change color on exposure to light, to develop a reduction in surface gloss, and to form deposits of flame retardant agents on the polymer surface.

Anderson, et al., U.S. Pat. No. 3,876,612 disclose ABS plastic compositions containing symmetrical bisphenoxy flame retardants. The compositions of the flame retardants are depicted by the following formula: ##STR1## where Z is bromine or chlorine; m and m’ are integers having a value of 1-5; and i and i’ are integers having a value of 0-2; A is a cyano, nitro, lower alkoxy, lower alkyl, fluorine, dialkylamino, phenyl, halo-phenyl, benzyl or halo-benzyl group; and R is chosen from the following group: ##STR2##

Anderson, et al., ‘612 does not disclose the use of an unsymmetrical higher alkyl bisphenoxy alkane as a flame retardant agent for the disclosed ABS resin.

U.S. Pat. No. 3,883,479 issued to Anderson, et al., discloses plastic compositions containing ABS and symmetrical bisphenoxy compounds. The bisphenoxy compounds have the formula: ##STR3## wherein A is bromine, m and m’ are integers having a value of 1-4, i and i’ are integers having a value of 1 or 2. The alkylene is a straight or branched chain alkylene group having from 1 to 6 carbon atoms. A is to be selected from the group consisting of cyano, nitro, lower alkoxy, lower alkyl (defined as CH.sub.3, C.sub.2 H.sub.5, C.sub.3 H.sub.7 or C.sub.4 H.sub.g), fluorine, dialkylamino, phenyl, halo-phenyl, benzyl or halo-benzyl group. Anderson, et al., ‘479, do not disclose the use of an unsymmetrical higher alkyl bisphenoxy alkane as a flame retardant agent.

Anderson, et al., U.S. Pat. No. 3,892,710 disclose ABS plastic compositions containing symmetrical halogenated aryl flame retardants. The flame retardants have the formula: ##STR4## where Z is bromine or chlorine; m and m’ are integers having a value of 1-5, i and i’ are integers having a value of 0 to 2, M and M’ are each independent and are from the group consisting of oxygen, nitrogen or sulfur as long as both m and m’ are not oxygen. A is chosen from the group consisting of cyano, nitro, lower alkoxy, lower alkyl, fluorine, diakylamino, phenyl, halo-phenyl, benzyl or halo-benzyl group. Anderson, et al., ‘b 710’s disclosure on halogenated aryl flame retardants fails to suggest usage of an unsymmetrical higher alkyl bisphenoxy alkane.

In U.S. Pat. No. 3,971,758, Anderson, et al., disclose an ABS plastic composition containing symmetrical bisphenoxy flame retardant compounds. The compositions of the flame retardants have the formula: ##STR5## where Z is bromine or chlorine; m and m’ are integers having a value of 1 to 5; i and i’ are integers having a value of 0 to 2; HBCA is a halo-branched alkylene group having from 1 to 6 carbon atoms; and A is cyano, nitro, lower alkoxy, lower alkyl (C.sub.1 -C.sub.4), fluorine, dialkylamino, phenyl, halo-phenyl, benzyl or halo-benzyl group. Again, Anderson, et al., ‘758 fail to disclose usage of an unsymmetrical higher alkyl bisphenoxy alkane as a flame retardant agent.

Anderson, et al., U.S. Pat. No. 4,016,137, describe plastic compositions containing ABS and symmetrical bisphenoxy flame retardant compounds, which have the following formula: ##STR6## where Z is bromine, m and m’ are integers having a value between 1 and 5 and the alkylene is a straight or branched alkylene group containing 1 to 6 carbon atoms. This reference again fails to suggest usage of an unsymmetrical higher alkyl bisphenoxy alkane as a flame retardant.

Anderson, et al., U.S. Pat. No. 4,016,139 disclose a composition containing an ABS polymer, a symmetrical bisphenoxy flame retardant and a flame retardant enhancing agent. The bisphenoxy flame retardant has the following formula: ##STR7## wherein Z is bromine, m and m’ are integers having a value of 1 to 5 so that the total bromine atom content ranges from 6 to 10 atoms, and T is a straight chain or branched chain carbon group having 1 to 4 carbon atoms. There is a lack of disclosure of a unsymmetrical higher alkyl bisphenoxy alkane compound in Anderson, et al., ‘139.

Anderson, et al., U.S. Pat. No. 4,051,105, disclose a plastic composition. The plastic composition contains an ABS polymer and a symmetrical b isphenoxy compound having the formula: ##STR8## where Z is bromine, m is an integer having a value of 1 to 5, and m’ is an integer having a value of 0 to 4, i is an integer having a value of 0 to 2, and i’ is an integer having a value of 1 to 5. The alkylene is a straight or branched chain alkylene group having from 1 to 6 carbon atoms and A is chlorine. Clearly there is no disclosure of unsymmetrical higher alkyl bisphenoxy compound in Anderson, et al, ‘105.

In overview, the bromine containing compounds for ABS resin described by the Anderson, e al., patents disclose the usage of symmetrical bisphenoxy alkane compounds containing nuclear aromatic bromination, alkylation and various other substitutions. The use of these symmetrical bisphenoxy alkane compounds has not been entirely satisfactory in ABS systems. In particular, the symmetrical bisphenoxy compounds such as bis(tribromophenoxy)-ethane tend to bloom or migrate to the polymer surface is ABS systems.

Accordingly, a primary object of the present invention is to provide an agent capable of flame retarding ABS resin compositions without exhibiting problems of bloom, heat or light instability, or any of the other disadvantages of the prior art ABS flame retardant agents.

A further object is to provide flame retardant ABS resin compositions that exhibit the desired level of flame retardancy without suffering any deterioration of physical properties.

Yet a further object is to utilize an halogenated unsymmetrical higher alkyl bisphenoxy alkane, as flame retardant agents for ABS resins.

SUMMARY OF THE INVENTION

The foregoing and other objects, advantages and features of this invention may be achieved with flame retardant ABS resin compositions comprising a normally combustible ABS resin; an effective amount of halogenated unsymmetrical higher alkyl bisphenoxy alkane and an enhancing agent. The compositions of this invention preferably comprise about 50 to 90 percent ABS thermoplastic resin, about 5 to 30 percent halogenated unsymmetrical higher alkyl bisphenoxy alkane and about 0.1 to 15 percent enhancing agent, all by weight of the composition.

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