Application of John A. Casey, 405 F.2d 567 (C.C.P.A. 1969)

This appeal is from a decision of the Patent Office Board of Appeals¹  affirming the examiner's rejection of claims 1-20, all the claims of application serial No. 403,354, filed October 12, 1964, for "Stabilized Crystalline Propylene Polymers." The issue is whether appellant's claimed invention is obvious and hence unpatentable under 35 U.S.C. § 103.

The invention, claimed both as process and product, relates to the stabilization of polypropylene by the addition thereto of an additive comprising a stabilizing quantity of a tris-phenol having the formula:

NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE

wherein n is a whole number from 1 to 3, R is a tertiary alkyl group containing 4 to about 16 carbon atoms, and R' is a normal alkyl group containing 1 to about 16 carbon atoms. In the application, it is disclosed that:

By using a stabilizing quantity of the tris-phenol of this invention in combination with the polypropylene described herein, remarkable stability is imparted thereto against degradation by heat and oxidation, that caused by mechanical action, such as extrusion, and that made apparent by way of discoloration of the polymer. Thus, stability is imparted to the polymer during fabrication techniques wherein high temperatures are used, as well as during use of so-formed shaped articles in the presence of heat or oxygen.

Method claims 1-8 are directed to a process for forming a shaped article of polypropylene stabilized as described above, and claims 9-20 are directed to stabilized polymer compositions. Claims 1 and 9 are representative and read as follows:

1. A process comprising mixing a solid, substantially crystalline, polymer of propylene with a stabilizing quantity, effective to inhibit degradation of said polymer resulting from exposure thereof to at least one factor causing degradation, of a tris-phenol, melting the resulting mixture, and forming from said melted mixture shaped articles having improved resistance to environmental degradation by said factor, said tris-phenol having the general formula:

NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE wherein n is a whole number from 1 to 3, R is a tertiary alkyl group containing 4 to 16 carbon atoms, and R' is a normal alkyl group containing 1 to 16 carbon atoms.

9. A stable polymer composition comprising solid, isotactic, substantially crystalline polypropylene and a stabilizing quantity of a tris-phenol having the general formula:

NOTE: OPINION CONTAINING TABLE OR OTHER DATA THAT IS NOT VIEWABLE

wherein n is a whole number from 1 to 3, R is a tertiary alkyl group containing 4 to 16 carbon atoms, and R' is a normal alkyl group containing 1 to 16 carbon atoms:

The references relied on are:

Sullivan et al. 2,819,329 Jan. 7, 1958 Hawkins et al. 2,889,306 June 2, 1959 Salyer et al. 2,985,617 May 23, 1961 Maragliano et al. 3,013,003 Dec. 12, 1961 Bailey 3,067,259 Dec. 4, 1962 Burnett et al. (Australia) 208,596 Oct. 27, 1955

Although we shall discuss these references in more detail hereinafter, their relevant teachings may be briefly summarized as follows.

Sullivan discloses some of the same tris-phenols as those in appellant's claims, utilized as stabilizers for vulcanized rubber.

Hawkins discloses the stabilization of polypropylene and polyethylene by the addition of retarder materials comprising carbon black and thiuram disulfide. Hawkins also discusses the stabilization of polypropylene and polyethylene in his review of the general, known background to this subject, stating at column 2, lines 25-41:

The deleterious degradative effect of thermal oxidation on polymers, such as polyethylene and polypropylene, have [sic] also received considerable attention by researchers in the field. Effective "antioxidants" developed for this purpose are generally phenols or secondary amines of aromatic compounds which may, in addition to the amino or phenolic grouping, contain, as an additional ring substituent, a branched or normal aliphatic radical generally containing three or more carbon atoms. As is well known, a general requirement of such antioxidants is that they contain an antioxidant group such as the secondary amino or phenolic group attached to an aromatic ring, the compound having such a structure that its resulting radical is stabilized by resonance energy. Much consideration has been given such antioxidants in the texts, see, for example, G. W. Wheland's "Advanced Organic Chemistry," 2nd edition, chapters 9 and 10. [Emphasis added.]

Salyer is directed to the stabilization of Ziegler type polymers by the addition thereto of stabilizers for polyvinylchloride, either alone or in combination with rubber antioxidants. Although the Salyer examples are for polyethylene only, the specification (column 3, lines 30 and 31) states:

Other ethylenically unsaturated hydrocarbons whose Ziegler polymers are of potential interest include propylene, butylenes, especially butene-1, amylenes and the like. [Emphasis added.]

Maragliano teaches a process involving controlled thermal depolymerization of polypropylene to reduce the viscosity of the material sufficiently to enable it to be worked into filaments and films. Once the necessary amount of depolymerization has been achieved, a heat stabilizer or retardant is added in an amount sufficient to prevent further breakdown of the polymer. The specification (column 3, lines 33-45) states:

Generally speaking, heat-stabilizing agents or depolymerization inhibitors or retardants of the kind useful for stabilizing polyvinyl chloride and rubbers may be used, including particularly organo-tin compounds, alkyl-aryl phosphites, aromatic amines and phenol derivatives. Such compounds, in addition to exerting a controlling effect on the rate of the thermal conversion of the polymers, persist in the depolymerized polymers and articles formed from them, and continue to exert a stabilizing action thereon. Stabilizing agents, such as phenyl-beta-naphtylamine [sic], which protect the polymers and shaped articles against light, can be added to the starting polymer with the heat-stabilizer or after the addition of the latter. [Emphasis added.]

Bailey teaches stabilization of polyethylene and polypropylene²  by the use of tris-phenols differing from those of appellant only in that a single alkoxy³  group is utilized in one position where appellant's tris-phenols have an alkyl group.

Burnett discloses stabilization of polyethylene by the addition of various antioxidants, including some of the same tris-(alkylphenols) disclosed by appellant.

The examiner rejected all the claims under 35 U.S.C. § 103 as unpatentable over Salyer in view of Sullivan, it being his position that Salyer teaches the use of rubber antioxidants to stabilize polypropylene and it would therefore be obvious to use the rubber antioxidants of Sullivan in polypropylene.

As an alternative rejection, all the claims were rejected under 35 U.S.C. § 103 as unpatentable over Maragliano or Hawkins in view of Burnett. In this rejection the examiner submitted that since the primary references show the conventionality of using the same stabilizers in polyethylene and polypropylene, it would be obvious to use the compounds of Burnett in the polypropylene of the primary reference and expect the results obtained.

The board, after reviewing the references, stated:

This case too differs from those cases wherein a selection has been made from a very large list of materials without any guidance as to which might be especially suited for a particular material or stabilizing function. In this case there are several clear signposts leading to the choice of appellant's tris-phenols. The first is that it is clearly taught they are effective stabilizers (Burnett et al.) for the closely related polyethylene which, for purposes of stabilization with a closely related tris-phenol, has been equated with polypropylene and rubber (Bailey) as well as by Salyer et al. for stabilization with rubber antioxidants in general. [Emphasis added.]

The board then discussed Hawkins' teaching that polyethylene and polypropylene may be stabilized by the same antioxidants and commented that appellant had not attempted to challenge the effectiveness of Burnett's antioxidant (the same as some of appellant's) for stabilizing polyethylene. The board said:

Our conclusion on this state of facts is that the art contains adequate guideposts to the choice of the claimed tris-phenols to stabilize polypropylene.

Much of appellant's brief before us is devoted to an attack on the relevance of the Salyer reference which appellant characterizes as "the reference on which the Patent Office relied most heavily." We do not consider this characterization to be correct in view of the fact that the board in the last decisive paragraph of its opinion mentioned Salyer only once and then only as a cumulative reference supporting Bailey.

Appellant's arguments against Salyer are centered about (1) the allegedly vast and all encompassing disclosure of Sayler which might embrace thousands and even millions of combinations of materials while actually showing examples restricted only to polyethylene stabilization, and (2) the alleged ineffectiveness of the Salyer teachings for the intended purpose of stabilizing polyethylene. We do not, however, find it necessary to pass upon the merits of appellant's arguments concerning the weight to be given to Salyer because the Salyer reference is not involved in the reasoning of our decision.

Instead, we believe Bailey provides adequate teaching that tris-phenols suitable for stabilizing polyethylene may also be suitable for stabilizing polypropylene. This teaching is explicit and unambiguous as may be confirmed by reference to the previously-quoted excerpt from Bailey in footnote 2. Furthermore, we reject appellant's contention that Bailey does not so teach merely because no actual examples of polypropylene stabilization are given.

Informed by the teaching of Bailey that his particular tris-phenol is suitable for stabilizing both polyethylene and polypropylene, we believe it would have been obvious to one of ordinary skill in the art, as of appellant's filing date, to employ the closely related tris-phenol of Burnett, known to be effective for stabilizing polyethylene, to stabilize polypropylene. This, we believe, was the correct understanding of the board as expressed in the emphasized portion of the previously quoted extract from their opinion, supra.

Furthermore, we are not persuaded by appellant's arguments as to the alleged, unexpectedly excellent results provided by his stabilizer as opposed to the results obtained utilizing the other stabilizers given as examples for comparison in the specification. No showing has been made that, for purposes of comparison, appellant selected other stabilizers of known effectiveness for polypropylene stabilization and we think it particularly significant in this connection that appellant failed to provide any comparison with the results that would be obtained utilizing the known tris-phenol disclosed in Bailey as a stabilizer for polypropylene.

As we see no convincing reason for different treatment of the process and composition claims, the board's rejection of all the claims is, for the reasons expressed above, affirmed.

Affirmed.

SMITH, J., participated in the hearing of this case but died before a decision was reached.