Document ypxderOE052O0ngo5bZm7REeE

FILE NAME: Asbestos in Plastics (AIP) DATE: 1975 Nov 25 DOC#: AIP007 DOCUMENT DESCRIPTION: US Patent - Asbestos-Free Heat-Resistant Thermosettable Phenol-Aldehyde Molding Composition United States Patent Barker et al. [in 3,922,241 [45] Nov. 25, 1975 t54] ASBESTOS-FREE HEAT-RESISTANT THERMOSETTABLE PHENOL-ALDEHYDE MOLDING COMPOSITION [75] Inventors: Richard H. Barker, Dalton; Frank P. Florentine, Pittsfield, both of Mass. [73] Assignee: General Electric Company, Pittsfield, Mass. [22] Filed: June 12, 1974 [21] Appl. No.: 478,785 [52] U.S. Cl........................................ 260/17.2; 260/38 [51] Int. Cl.2.............................................C08L 1/02 [58] Field of Search.............................. 26Q/17.2, 38 [56] 3,567,667 References Cited UNITED STATES PATENTS 3/1971 Rumbold........................... 260/17.2 3,658,750 4/1972 Tsukui et al........................... 260/38 3,813,356 5/1974 Lievremont et al.................. 260/2.5 OTHER PUBLICATIONS Chem. Abst. 68:11540f, "Structural Material-Resins --Filler," Yatsenko et al. Primary Examiner--Donald E. Czaja Assistant Examiner--Edward Woodberry Attorney, Agent, or Firm--William F. Mufatti; Donald M. Papuga [57] ABSTRACT An asbestos free, heat resistant phenolic molding com position comprising in admixture, a phenolic resin and a filler combination of aluminum silicate, talc and cel lulose fibers. 6 Claims, No Drawings 3,922,241 1 2 ASBESTOS-FREE HEAT-RESISTANT THERMOSETTABLE PHENOL-ALDEHYDE MOLDING COMPOSITION The phenolic resin employed in the practice of this invention is preferably a phenol-aldehyde resin and can be any phenol-aldehyde resin which is prepared by re acting from less than one mole to more than one mole 5 of an aldehyde per mole of phenol under certain condi This invention relates to an asbestos free, heat resis tions to provide a resin. If less than one mole of an alde tant phenolic molding composition comprising in ad hyde is used, the resin so produced is commonly called mixture a phenolic resin and a filler combination of alu a novolac. The novolac resin is generally the type that minum silicate,,talc and cellulose fibers. can be finely ground and requires blending thereof with BACKGROUND OF THE INVENTION 0 an external crosslinking agent such as hexamethylene tetramine in order to provide a thermosettable resin Phenolic molding compositions have been available for many years and are generally made with an asbestos filler. The asbestos is used as a reinforcing fiber or as a reinforcing filler. The asbestos provides the phenolic molding composition with increased mechanical, ther mal and electrical properties. However, the use of as bestos filled phenolics provides a hazard to those ex posed to this type of material. The standard for direct exposure to asbestos fibers is clearly detailed by the Department of Labor's Occupa tional Safety and Health Administration (OSHA). Ef fects of exposure to personnel involved in the manufac ture of phenolic molding compound in which raw as bestos is handled or processed is well delineated. What is less obvious is the health hazard to personnel in shops that mold asbestos material and finish or machine the molded parts. In order to comply with OSHA standards dealing with asbestos, the development of asbestos-free pheno lic molding compositions which comply with the OSHA law is needed. However, there are properties problems associated with eliminating asbestos from phenolic molding compositions. Two of the key properties ef fected are dimensional stability and heat resistance. The heat resistance, mechanical and electrical prop erties of the non-asbestos phenolic molding composi tions must be at least equivalent to the asbestos-con taining compositions. Additionally, the moldability, of the non-asbestos compositions must be equivalent to the asbestos-filled compositions. Since the same mold is used for asbestos and non-asbestos compositions, the which can be advanced to an infusible state upon expo sure to elevated temperatures. While any external crosslinking agent can be employed herein, the pre5 ferred external crosslinking agent is hexamethylenetet ramine. Generally, the preferred range of aldehyde em ployed herein to prepare the novolac is 0.5-0.9 moles thereof per mole of phenol and preferably 0.6 -0.8 moles thereof. While any aldehyde can be employed 2 herein such as folmaldehyde, paraformaldehyde, acet aldehyde, butyraldehyde, furfuraldehyde, etc., the pre ferred aldehyde to be employed herein is formalde hyde. When employing more than one mole of aldehyde 25 per mole of phenol, a one-stage resin is produced which can be advanced to an infusible state by the mere appli cation of elevated temperatures. The one-stage resin which can be employed herein is one prepared by re acting more than one mole of an aldehyde per mole of 30 phenol and preferably 1.1-3.0 moles thereof. Again, the preferred aldehyde is formaldehyde. In addition, it has also been observed that when using a phenolformaldehyde novolac, favorable molding characteristics are obtained when the novolac has or- 35 tho-ortho content of less than 70 weight percent of the total novolac composition. Optimum results are ob tained when the ortho-ortho content is around 50 weight percent, by the balance of the novolac consists of ortho-para and para-para linkages. By these various types of linkage, it is meant the methylene bridging between the phenol nuclei and can be represented by the following formulas: shrinkage of both types should be similar. In short, the non-asbestos compositions should not change normal 45 . operation procedures, at least in a deleterious sense. The non-asbestos filler combination of the instant in vention satisfies this criteria. DESCRIPTION OF THE INVENTION The invention is directed to an asbestos-free heat re sistant phenolic molding composition comprising in ad mixture, a phenolic resin and a filler combination of aluminum silicate, talc and cellulose fibers. The filler combination of the instant invention when used with the phenolic resin provides a molding com position having heat resistant properties better than an asbestos filled phenolic resin composition. Also, heat deflection temperature and dielectric strength are greater using the filler combination of the instant in vention in place of asbestos in phenolic resins. Addi tionally, water absorption, arc resistance, tensile strength, flexural strength, flexural modulus, compres sive strength, Izod impact and drop ball impact proper ties of a phenolic resin with the filler combination of the instant invention are comparable to an asbestos filled phenolic resin composition. - 3,922,241 ortho-para linkage cent of asbestos fibers and 15 weight percent of wood flour to form a 50/50 mixture. The blend is then com pounded in a screw extruder at about 220F which is 5 sufficient to melt the resin. The molten mixture is ad vanced through the screw and extruded into granular or pellet form; EXAMPLE II 10 Example I is repeated except that a filler combination of 14 weight percent aluminum silicate, 15 weight per cent of talc and 8 weight percent of cellulose fiber is used in place of the asbestos. Each of the materials so prepared in Examples I and 15 II are subjected to the following tests: Water Absorp tion, Heat Deflection (ASTM D-648), Dielectric Strength (ASTM D-I49), Arc Resistance (ASTM D- para-para linkage 495), Tensile Strength (ASTM D-65I), Flexural Strength (ASTM D-790), Flexural Modulus (ASTM The individual components of the combination of fill 20 D-790), Compressive Strength (ASTM D-695), Izod ers of the instant invention, i.e., alumina silicate, talc Impact (ASTM D-256A) and the Drop Ball Impact. All and cellulose fibers are commercially available in vari ous forms and grades. The combination of fillers can be test specimens are molded from conventional molding methods. The results are tabulated as follows: employed in an amount of from about 15 to about 50 weight percent. Preferably the filler combination con 25 TABLE I tains from about 5 to about 20 weight percent alumina silicate, from about 5 to about 20 weight percent of talc Test Example Example Il I and from about 5 to about 10 weight percent of cellu lose fibers. Said weight percents being based on the weight of the molding composition. 30 The composition of this invention is prepared by methods well known to those skilled in the art. For ex ample, the individual ingredients are mixed together in a suitable vessel and then fed directly to the feed 35 hopper of a screw extruder or roll mill. Waler Absorptionen, 24 hr.) Heat Deflection (F. at 264 psi) Dielectric Strength! 60 cps. 25"C,st. VPM) Arc Resistant (sec) Tensile Strength (psi) Flexural Strength (psi) Flexural Modulus (psi) Compressive Strength (psi) Izod Impact)ft-lb/in. notch) Drop Ball Impact (in. M lb. weight) 0.2 380 360 180 7000 12000 1x10" 23000 .30 11 0.2 350 350 180 8000 12000 1x10 27000 .33 13 It should be noted that the phenolic resin composi tions of this invention can, and generally do, have pres ent additive compounds which are normally used in Dimensional stability refers to the ability of the such compositions in addition to the composition of 40 molded part to maintain its dimensions within reason this invention. Included among these other additives able limits under a wide variety of ambient conditions; are fillers such as wood flour, calcium carbonate, glass it is particularly important when the molded phenolic fibers, etc. and any combination of these or other part is a component in a device or assembly which must known fillers employed in the phenolic molding com rely on close part tolerances for successful operation. position as well as such additives as coal, lime, stearic 45 This property was evaluated for the compositions of acid, etc. In a preferred embodiment of the instant in Examples I and II. The test moldings, in this case, were vention, the composition of the instant invention may compression molded \'h in. X 3 in. rectangular boxes, contain lime in amounts of from 4 to 10 weight percent. k in. deep, with crosssections of 0.100 in. (walls) and Vs in. and V* in. (bottom). In yet another preferred embodiment the composition Dimensions in both the length and width direction forfotmhe5intosta1n5t wineviegnhttiopnermceanyt.contain coal in amounts of 50 were tracked over a period of 15 days at room tempera ture, 150F, 200F and 250F. PREFERRED EMBODIMENT OF THE INVENTION The results are tabulated as follows: The following examples are set forth to illustrate more clearly the principle and practice of this invention to those skilled in the art and unless otherwise speci fied, where parts or percentages are mentioned, they are parts or precentages by weight. EXAMPLE I A phenol-formaldehyde resin is prepared by reacting about 0.7 moles of formaldehyde per mole of phenol in the presence of an acid catalyst, which is subsequently neutralized, to form a novolac. The novolac is ground to a fine particle size with about 16 weight percent of hexamethylenetetramine based on the weight of novolac. The resin mixture is then blended with 38 weight per- 55 TABLE II Temperature 60 Room Temperature* 75*F) 150F 200F 250F E xam ple 11* 0.1 1.4 2.3 2.9 Example ! 0.2 1.3 2.6 3.4 The&e numbers indicate dimensional change of length in mils per inch. 65 The results in Table I demonstrate that heat deflec tion and dielectric strength were significantly improved with the composition of Example II whereas water ab sorption, arc resistance, tensile strength, flexural strength, flexural modulus, compressive strength, Izod 3,922,241 5 6 impact and drop ball impact data of Example I were sentially of in admixture, a phenol-aldehyde resin and a comparable with Example II. Table II demonstrates filler combination of aluminum silicate, talc and cellu that at higher temperatures the composition of Exam lose fibers; said filler combination present in an amount ple II exhibits less overall change in dimension than the of from about 15 to about 50 weight percent based on composition of Example I. Therefore, the filler combi- ^ the weight of the molding composition. nation of the instant invention provides a phenolic 2. The composition as defined in claim 2 wherein the molding composition of comparable and better proper aluminum silicate is present in an amount of from ties than a composition containing asbestos. about 5 to about 20 weight percent based on the weight Example II was repeated using varying amounts of of the molding composition. the aluminum silicate, talc and cellulose fibers. The re- 10 3. The composition as defined in claim 1 wherein the suits obtained were similar to those set forth in Tables talc is present in an amount of from about 5 to about 20 I and II. weight percent based on the weight of the molding Obviously, other modifications and variations of the composition. present invention are possible in the light of the above 15 4. The composition as defined in claim 1 wherein the teachings. It is, therefore, to be understood that cellulose fibers are present in an amount of from about changes may be made in the particular embodiments described which are within the full intended scope of 5 to about 10 weight percent based on the weight of the molding composition. the invention as defined by the appended claims. 5. The composition as defined in claim 1 which con What is claimed is: 20 tains lime. 1. An asbestos-free, heat-resistant thermosettable 6. The composition as defined in claim 1 which con tains coal. phenol-aldehyde molding composition consisting es- * * *** 25 30 35 40 45 50 55 60 65