Document MoJ8VdVzbv3D1RO5DQedd0LLk

FILE NAME: Asbestos in Plastics (AIP) DATE: 1975 Nov 25 DOC#: AIP008 DOCUMENT DESCRIPTION: US Patent - Asbestos-Free Heat-Resistant Thermosettable Phenol-Aldehyde Molding Composition United States Patent im Barker et al. [in 3,922,241 [45] Nov. 25, 1975 [54] 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 [511 Int. Cl.2.............................................. C08L 1/02 [58] Field o! Search............................... 260/17.2, 38 [56] 3,567,667 References Cited UNITED STATES PATENTS 3/1971 Rumbold......................... 260/17.2 3,658,750 3,813,356 4/1972 5/1974 Tsukui et al............................ 260/38 Lievremont et al................... 260/2.5 OTHER PUBLICATIONS Chem. Abst. 68:11540f, "Structural M aterial-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 s 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 minum silicate, talc and cellulose fibers. a novolac. The novolac resin is generally the type that can be finely ground and requires blending thereof with BACKGROUND OF THE INVENTION an external crosslinking agent such as hexamethylene tetramine in order to provide a thermosettable resin which can be advanced to an infusible state upon expo 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 sure to elevated temperatures. While any external crosslinking agent can be employed herein, the pre 15 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 bestos filled phenolics provides a hazard to those ex moles thereof. While any aldehyde can be employed posed to this type of material. 20 herein such as folmaldehyde, paraformaldehyde, acet The standard for direct exposure to asbestos fibers is aldehyde, butyraldehyde, furfuraldehyde, etc., the pre clearly detailed by the Department of Labor's Occupa ferred aldehyde to be employed herein is formalde tional Safety and Health Administration (OSHA). Ef fects of exposure to personnel involved in the manufac hyde. When employing more than one mole of aldehyde ture of phenolic molding compound in which raw as- 25 per mole of phenol, a one-stage resin is produced which bestos is handled or processed is well delineated. What can be advanced to an infusible state by the mere appli is less obvious is the health hazard to personnel in shops cation of elevated temperatures. The one-stage resin that mold asbestos material and finish or machine the which can be employed herein is one prepared by re molded parts. acting more than one mole of an aldehyde per mole of In order to comply with OSHA standards dealing 30 phenol and preferably 1.1-3.0 moles thereof. Again, with asbestos, the development of asbestos-free pheno the preferred aldehyde is formaldehyde. lic molding compositions which comply with the OSHA In addition, it has also been observed that when using law is needed. However, there are properties problems a phenoiformaldehyde novolac, favorable molding associated with eliminating asbestos from phenolic characteristics are obtained when the novolac has or molding compositions. Two of the key properties ef- 35 tho-ortho content of less than 70 weight percent of the fected are dimensional stability and heat resistance. total novolac composition. Optimum results are ob The heat resistance, mechanical and electrical prop tained when the ortho-ortho content is around 50 erties of the non-asbestos phenolic molding composi weight percent, by the balance of the novolac consists tions must be at least equivalent to the asbestos-con of ortho-para and para-para linkages. taining compositions. Additionally, the moldability of 40 By these various types of linkage, it is meant the the non-asbestos compositions must be equivalent to methylene bridging between the phenol nuclei and can the asbestos-filled compositions. Since the same mold be represented by the following formulas: is used for asbestos and non-asbestos compositions, the 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. OH OH DESCRIPTION OF THE INVENTION 50 _ch2 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. 55 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 ortho-ortho linkage asbestos filled phenolic resin composition. Also, heat deflection temperature and dielectric strength are 60 B. 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 CHo sive strength, Izod impact and drop ball impact proper 65 ties of a phenolic resin with the filler combination of the instant invention are comparable to an asbestos filled phenolic resin composition. 3 ortho-para linkage 3,922,241 4 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-149), Arc Resistance (ASTM D- 495), Tensile Strength (ASTM D-651), Flexural para-para linkage Strength (ASTM D-790), Flexural Modulus (ASTM 20 D-790), Compressive Strength (ASTM D-695), Izod The individual components of the combination of fill Impact (ASTM D-256A) and the Drop Ball Impact. All ers of the instant invention, i.e., alumina silicate, talc test specimens are molded from conventional molding and cellulose fibers are commercially available in vari methods. The results are tabulated as follows: ous forms and grades. The combination of fillers can be employed in an amount of from about 15 to about 50 weight percent. Preferably the filler combination con 25 tains from about 5 to about 20 weight percent alumina silicate, from about 5 to about 20 weight percent of talc and from about 5 to about 10 weight percent of cellu TABLE I Test W ater A bsorption(7<, 24 hr.) H eat D eflection (F. at 264 psi) Exam ple 11 0.2 380 Exam ple 1 02 350 lose fibers. Said weight percents being based on the 30 D ielectric S tren g th (6 0 cps 25Cst. weight of the molding composition. Arc Resistant (sec) V PM ) The composition of this invention is prepared by Tensile S trength (psi) 360 180 7000 350 180 8000 methods well known to those skilled in the art. For ex ample, the individual ingredients are mixed together in Flexural S trength (psi) Flexural M odulus (psi) Com pressive Strength (psi) 12000 1X10" 23000 1200C 1X10" 27000 a suitable vessel and then fed directly to the feed 35 lzod lm p act(ft-lb /in . n o tch ) hopper of a screw extruder or roll mill. D ro p B all Im p a c t (in V* lb w e ig h t) .30 33 1 1 13 It should be noted that the phenolic resin composi tions of this invention can, and generally do, have pres Dimensional stability refers to the ability of the ent additive compounds which are normally used in molded part to maintain its dimensions within reason such compositions in addition to the composition of 40 able limits under a wide variety of ambient conditions; this invention. Included among these other additives it is particularly important when the molded phenolic are fillers such as wood flour, calcium carbonate, glass part is a component in a device or assembly which must fibers, etc. and any combination of these or other rely on close part tolerances for successful operation. known fillers employed in the phenolic molding com This property was evaluated for the compositions of position as well as such additives as coal, lime, stearic 45 Examples I and II. The test moldings, in this case, were acid, etc. In a preferred embodiment of the instant in compression molded 1Vfein. x 3 in. rectangular boxes, vention, the composition of the instant invention may % in. deep, with crosssections of 0.100 in. (walls) and contain lime in amounts of from 4 to 10 weight percent. Ve in. and % in. (bottom). In yet another preferred embodiment the composition Dimensions in both the length and width direction of the instant invention may contain coal in amounts of 5 0 were tracked over a period of 15 days at room tempera from 5 to 15 weight percent. ture, 150F, 200"F 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 1 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 Tem perature Exam ple 11* Exam ple I* Room T em perature(75F) 0.1 0.2 60 1 5 0 F 1 4 1 3 200T 2 3 2.6 25QT 2.9 3.4 These numbers indicate dimensional change o f 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, lzod 3,922,241 5 6 impact and drop ball impact data of Example 1 were sentially of in admixture, a phenol-aldehyde resin and a comparable with Example 11. 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 jq of the molding composition. the aluminum silicate, talc and cellulose fibers. The re 3. The composition as defined in claim 1 wherein the sults obtained were similar to those set forth in Tables talc is present in an amount of from about 5 to about 20 l and II. Obviously, other modifications and variations of the present invention are possible in the light of the above teachings. It is, therefore, to be understood that changes may be made in the particular embodiments described which are within the full intended scope of the invention as defined by the appended claims. weight percent based on the weight of the molding composition. j 5 4. The composition as defined in claim 1 wherein the cellulose fibers are present in an amount of from about 5 to about 10 weight percent based on the weight of the molding composition. 5. The composition as defined in claim I which contains lime. What is claimed is: 6. The composition as defined in claim 1 which con 1. An asbestos-free, heat-resistant thermosettable tains coal. phenol-aldehyde molding composition consisting es- Sfc >jC ifc tfc 25 30 35 40 45 50 55 60 65