Arylene sulfide polymer cured with the aid of certain compounds
United States Patent 1 Blackwell ARYLENE SULFIDE POLYMER CURED WITH THE MD or CERTAIN COMPOUNDS [75] inventor: Jennings P. Blackwell, Bartlesville.  
 Okla.  
 [73] Assignee: Phillips Petroleum Company,  
 Bartlesville, Okla.  
 [22] Filed: Nov. 29, 1973 [21 Appl. No.: 420,256  
 [52] US. Cl 260/79; 260/791; 117/132 R; ll7/l6l R [51] Int. Cl. C08g 23/00 [58] Field of Search 260/79. 79.1  
 [451 Apr. 22, 1975 [56] References Cited UNITED STATES PATENTS 3.658.753 4/l972 Rccd ct ul 260/79 3.728.313 4/l973 Hill. Jr. ct al 260/79 Primary E.\&#39;umim&#39;rMelvyn l. Marquis [57] ABSTRACT Certain compounds are incorporated into arylene sulfide polymer. The resulting composition is precured to give a polymer of improved processability and/or applied to a substrate and cured to give a coating having improved characteristics.  
 10 Claims, No Drawings ARYLENE SULFIDE POLYMER CURED WITH THE AID OF CERTAIN COMPOUNDS BACKGROUND OF THE INVENTION This invention relates to improving the characteristics of arylene sulfide polymer compositions.  
  It is known that arylene sulfide polymers are useful in coatiing applications. Coating formed thereof are strong, heat stable and resistant to most industrial chemicals and fumes. Thus, for example, arylene sulfide polymers can be advantageously employed as coating for metals such as steel, aluminum, nickel, brass, copper, as well as ceramics, glass and other substrates stable at the curing temperature required for the coating which can run as high as 800F.  
  Arylene sulfide polymer is also ideally suited for other molding techniques such as extrusion and injection molding. However, in many instances the polymer as produced, while having a very high melting point, nonetheless has an extremely low melt viscosity with the melt flow number (MFN) as measured by ASTM D l238-65T (modified to use a 5 kilogram weight and a temperature of 343C.) being greater than 2500 g in minutes. To be usable in such applications, a melt flow in the range of only l-200 is generally required.  
 BRIEF SUMMARY OF THE INVENTION It is an object of this invention to provide an improved arylene sulfide polymer coated substrate; it is yet a further object of this invention to provide coating compositions comprising arylene sulfide polymers having enhanced processability, coating flexibility, and coating adherence; it is yet a further object of this invention to provide arylene sulfide coating compositions which can be cured at a relatively fast rate to form good, adherent, flexible coatings for metal and other materials without subjecting same to undesirably high temperatures; and it is still yet a further object of this invention to provide an arylene sulfide polymer composition having improved processability.  
  In accordance with this invention arylene sulfide polymer is compounded with at least one of (a) aluminum phosphate, (b) a polyfunctional benzene derivative in which at least two positions on the benzene nucleus are replaced by a functional group selected from (OH) and/or (NH with the substitution being in the meta or para positions if only two positions are substituted, such compounds being represented by the following formula wherein R is OH or NH and at least one R is R, R is H and the remaining R entities are H or R, (c) a metal salt selected from cobalt sulfate, cobalt acetate, ferrous sulfate, or cuprie naphthenate; and (d) ammonium persulfate.- The resulting mixture is subjected to heat to at least partially cure the polymer.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention is applicable for use with any normally solid, heat curable, high molecular weight arylene sulfide polymer. The preferred arylene sulfide polymer is poly(phenylene sulfide) (PPS) having a melting or softening point of at least 300F, preferably 400F to 850F. Such polymer can be made in accordance with Edmonds et al, US. Pat. No. 3,354,129, Example I for instance, the disclosure with patent is hereby incorporated by reference. The preferred polymers have an inherent viscosity in chloronaphthalenc at 206C of at least 0.1, preferably between 0.1 and 03, more preferably between 0.13 and 0.23. A particularly preferred polymer is poly(phenylene sulfide) having a melt flow of from 50 to about 2500 (limit of the instrument meas urement by ASTM D 123 8-65T. modified to use 5 kilogram weight and a temperature of 343C). The virgin PPS which normally may have a melt flow number of above 2500 can be precured by heatiing in air at 500 to 520F for l-6 hours to lower the initial melt flow for instance to the above 50 to 2500 range.  
  The compounds which can be used in accordance with this invention to modify the curing of poly(arylene sulfide) are (a) aluminum phosphate, (b) polyfunctional benzene derivatives in which at least two positions on the benzene nucleus are replaced by a functional group selected from (OH) and/or (NH with the substitution being in the meta or para positions if only two positions are substituted, (c) a metal salt selected from cobalt sulfate, cobalt acetate, ferrous sulfate, or cupric naphthenate; and (d) ammonium persulfate.  
  The additives of this invention can be incorporated into the polymer prior to curing in any convenient manner. Thus, for example, the additives can be added as such to the polymer and the resulting mixture can be agitated in any convenient manner to achieve good mixing. A particularly convenient manner of introducing the additives into the polymer is the addition of the additive dissolved in a volatile solvent such hexane, benzene, acetone and the like to the polymer in powder form with subsequent volatilization of the solvent. Alternatively the additive dissolved in said solvent can be ball milled with powdered polymer. The additives can be melt blended but this is less preferred.  
 There are two broad aspects to this invention.  
  First, the additives of the invention are useful in accelerating the cure of virgin arylene sulfide polymer which has a melt flow too high to be useful in such applications as injection molding (precuring). Such polymer can be heated in air at a temperature of about 490 to 520F, preferably 500 to 5 10F for l to 10 preferably 2 to&#39; 6 hours to lower the original melt flow. Incorporation of additives to this invention allows for reduction in the time required to effect this lowering of melt flow or in the alternative, allows further reduction in melt flow for a given time, Thus, for instance, a polymer with a melt flow of 2500 or greater which is not suitable for fabrication operations such as injection molding can be heated after incorporation of the additive in accordance with the invention for 6 hours at 510F to bring the melt flow into the range of 0 to I5, preferably 1 to&#39; 15, This melt flow is measured in terms of MFN (melt flow number) which is the grams of polymer flowing from an orifice in 10 minutes utilizing ASTM D 123 8-65T, modified as noted to utilize a 5 kilpolymer during this pre-curing operation is generally in the solid state.  
  The use of the compounds of this invention speeds up the cure rate of either slow curing or fast curing resins. For example, a slow curing arylene sulfide polymer will ordinarily require 6 hours at F in air curing time to have a melt flow of less than about 400 withoutaccelerators. A fast curing resin will cure to a melt flow of less than about 400 in 2-4 hours at 5 10F. Very fast curing resins will cure to a melt flow of less than 100 in l2 hours at 510F in air without additives.  
  Thus, in accordance with the first aspect of this invention, a virgin polymer with a melt flow of 50 to above 2500 which is unsuitable for many applications can be made suitable for such applications after a relatively short curing time by utilizing the additives of this invention.  
  In accordance with the second aspect of the invention, the additives are incorporated into arylene sulfide polymer which is utilized in a coating composition (curing). This allows reduction of the curing temperature from the normal level which can run as high as 800F down to within the range of 575 to 725F, preferably about 600 to 700F. The temperature obviously is related to the particular polymer utilized and to the 7 time, of course, but in any event for a given polymer in a given curing time, the temperature for achieving a cure sufficient to give a good coating can be reduced preferably at least 100F below the temperature required to give a coating of similar quality without the additive. Similarly at a given cure temperature, the cure time can be reduced at least 10 minutes below the time required to give a coating of similar quality without the additive. The curing time will generally be from l0 to 40 minutes, preferably to 30 minutes. Times of 15 to minutes are particuarly suitable. ln addition to decreasing the cure time and/or temperature required, the coatings made in accordance with the invention have increased flexibility.  
  Thus, in accordance with this second aspect of the invention, the time and/or temperature required to cure a coating on a substrate can be reduced so as to allow coating of many substrates which would be adversely affected by the higher temperature and/or curing time. In fabricating pipe, for instance, the exposure of a substrate to long periods of high temperatures is undesirable because metalhas a tendency toward e&#39;mbrittlement under such severe conditions. As with the first aspect of the invention, either a slow or fast curing arylene sulfide polymer can be used, although in all as pects of the invention the advantage is greater with the slow curing polymers.  
  in addition to the additives of this invention, the compositions of this invention can contain other ingredients conventionally employed in arylene sulfide polymer compositions. For instance, fillers such as titanium dioxide, calcium carbonate, aluminum oxide, aluminum silicate, pigments, resins and/or plasticizers, ferric oxide, silicon dioxide, asbestos fibers, glass fibers, poly(tetrafluoroethylene), and the like can be present. Preferably the coating compositions will contain, based on 100 parts by weight polymer, 10 to 50 parts by weight of a filler pigment such as titanium dioxide and- /or poly(tetrafluoroethylene).  
  When arylene sulfide polymer compositions in accordance with this invention are used as coating materials,  
 the coatings can have a thickness of 0.25 to 25 mils. It is also within the scope of the invention to utilize a plurality of layers of the polymeric composition with the material being cured or at least partially cured between each coat. Preferably the total thickness will be in the range of 0.5 to 50 mils. The invention has been found to be of particular utility in the production of relatively thin coatings, that is coatings in which each layer has a thickness of about 0.5 to 5 mils.  
  The additives of this invention are employed in an amount within the range of 0.5 to 10, preferably 1 to 5. more preferably 1 to 3 weight percent based on the weight of the arylene sulfide polymer.  
 EXAMPLE I Formulations wereprepared in a Waring blender using the proportions of 100 parts poly(phenylene sulfide) or PPS, 33 parts TiO plus the additive, in 200 parts of propylene glycol. The solid additives were first powdered and predispersed in some of the glycol; inorganic salts were first dissolved in a little water to obtain better dispersion of the&#39;additive. The coating test procedure was as follows:  
  1 Cold rolled steel coupons, 3 X 6 X 0.035 in. were cleaned, grit-blasted and heated with a gas-oxygen flame to a blue-gray color.  
  2. Three coats of the formulation were applied to the coupon with a No. 60 coating rod; each coat was cured at the same conditions, usually 30 min. at 600F.  
 3. After the third coat was cured and cooled, the coupon was annealed for 2 hours at 450F, then cooled to room temperature.  
  4. The coated coupons were bent over a threesixteenths-inch mandrel and the elongated portion was examined at 20X magnification. The coating was rated l-5 as follows: I  
 Rating Observation 1 No cracking on elongated portion of the coating (very good) Occasional microcracks along elongated coating (good) Numerous microcracks and some cracking barely visible to the unaided eye. (not acceptable) Continuous and easily visible cracks.  
 (poor) Complete rupture of the coating.  
 (very poor) Y The poly(phenylene sulfide) was Ryton PPS Grade V-l, virgin polymer, melt flow 2000 as measured by ASTM D 123 8-65T, modified to operate at 343C. with a 5 kilogram weight. This was a fast curing resin as evidenced by the fact that it could be cured to a melt flow of 5.1, 5 l0F, air cure, with no additive.  
 Test results are given in the table below:  
 TABLE I Curing Curing Time. Rating Additive Conc.&#34;&#39; T.. F. Minutes l is best) Control. no Additive 700 10 2 Control. no Additive 700 30 1 Control. no Additive 600 60 3 Control, no Additive 600 30 3 MP 3 600 30 1 coat rough 1.2.3 trihydroxy-benzene I0 600 30 1 coat rough 1.2.3 trihydroxy-benzene 10 600 15 2-3 coat rough l,2,3 trihydroxy-benzene 5 600 30 1 coat rough p-Aminophenol I0 600 30 coat rough, dark 1,3 dihydroxy benzene 600 2 coat rough 1.3 dihydroxy benzene 10 600 30 coat rough &#34;parts by weight per I00 parts FPS (Php) &#34;&#39;a rough coating is still acceptable and. as can be seen. is obtained at a lower temperature which in some applications is essential.  
  The results show that all the additives tested will either produce a good coating, rating of l or 2. or at least a borderline acceptable coating with a rating of 2-3 at 600F cure even at the shorter 15 minute curing time when used at the concentrations tested. The l,2,3,trihydroxybenzene and AlPO. give excellent results at low levels. The last run apparently reflects experimental error or overcure.  
  While not tested, it is believed based on the chemicals that were tested that para-phenylenediamine would also be a preferred additive.  
  These results show that all of the additives tested will produce an acceptable coating with a rating varying from 2 to 2-3.  
 EXAMPLE III EXAMPLE II TABLE Ill The same polymer was used to form coatings in the C I C uring uring same manner as iii Example I utilizing the following ad- Cone Tn Time Rating ditives with the results given in the table hereinbelow. Additive .php F. Minutes (1 is best) Ammonium persulfate I0 600 30 2 TABLE II Curing Curing These results show that a good coating rating of 2 is Cunc. Time Rating produced using persulfate. Additive php F. Minutes (1 is best) Cobalt sulfate 10&#39; 600 30 3&#34; i0 600 I5 24 EXAMPLE IV c b It t r 10 600 30 2 i ffii 2 600 30 The same fast curing polyphenylene sulfide of Exam- Cupric nflphlhenme 10 600 30 ple I was mixed with certain additives and precured at I 5O 475F. with the melt flow number thereafter being de- May be poor due to experimental error or overcure. w Produced mixed results at 2 phr in thicker 12 mil) coatings. termined. The results were as follows.  
 TABLE IV MFN MNF MNF Heating Virgin Polymer 5 phr Cobalt l0 phr Time, hrsv Control, No Additive Acetate l,2,3-trihydroxy benzene &#34;flow g/li) minutes as previously defined. Low value apparently the result of experimental error.  
  These data reveal that compositions of this invention in addition to producing better coatings also can be precured so as to produce a polymer having a melt flow which is suitable for extrusion or injection molding whereas the original melt flow (approximately 2000) would be so high that the polymer would be useless for such applications.  
  While this invention has been described in detail for the purpose of illustration, it is not to be construed as limited thereby but is intended to cover all changes and modifications within the spirit and scope thereof.  
 What is claimed is:  
  l. A composition of matter comprising an arylcne sulfide polymer and 0.5 to 10 weight percent based on the weight of said arylcne sulfide polymer of a compound selected from the group consisting of a. aluminum phosphate b. a polyfunctional benzene derivative in which at least two positions on the benzene nucleus are replaced by a functional group selected from OH and NH with the substitution being in the meta or para position if only two positions are substituted;  
 c. a metal salt selected from cobalt sulfate, cobalt acetate, ferrous sulfate, or cupric naphthenate; and  
 d. ammonium persulfate.  
  2. A composition according to claim 1 wherein said compound is present in an amount within the range of l to 5 weight percent based on the weight of said polymer.  
  3. A composition according to claim 1 wherein said compound is aluminum phosphate.  
  4. A composition according to claim 1 wherein said compound is selected from the group consisting of para-amino phenol, 1,3-dihydroxybenzene, and 1,2,3- trihydroxybenzene.  
  5. A composition according to claim 1 wherein said compound is selected from the group consisting of cobalt sulfate, cobalt acetate, ferrous sulfate, and cupric naphthenate.  
  6. A composition according to claim 1 wherein said compound is ammonium persulfate.  
  7. A composition according to claim 1 wherein said polymer is polyphenylene sulfide.  
  8. A method for preeuring an arylcne sulfide polymer comprising incorporating into said polymer 0.5 to 10 weight percent based on the weight of said arylcne sulfide polymer of a&#39;compound selected from the group consisting of a. aluminum phosphate;  
 b. a polyfunctional benzene derivative in which at least two positions on the benzene nucleus are replaced by a functional group selected from OH and NH with the substitution being in the meta or para posititon if only two positions are substituted;  
 c. a metal salt selected from cobalt sulfate, cobalt acetate, ferrous sulfate, or cuprie naphthenate; and  
 d. ammonium persulate,  
 and thereafter heatiing said composition to a temperature within the range of 490 to 520F for a time within the range of 1 to 10 hours.  
 9. A method according to claim 8 wherein said polymer is a slow curing poly(phenylene sulfide).  
  10. A composition of matter comprising an arylcne sulfide polymer and an effective cure accelerating amount of a compound selected from the group consisting of a. aluminum phosphate b. a polyfunctional benzene derivative in which at least two positions on the benzene nucleus are replaced by a functional group selected from OH and NH; with the substitution being in the meta or para position if only two positions are substituted;  
 c. a metal salt selected from cobalt sulfate, cobalt acetate, ferrous sulfate, or cupric naphthenate; and  
 d. ammonium persulfate.