Thermoplastic compositions of epichlorohydrin rubber and poly(alkyl methacrylate) resin

#This invention relates to thermoplastic compositions and, more particularly, to thermoplastic compositions comprising blends of epichlorohydrin rubber and poly(alkyl methacrylate) resin.

#High molecular weight polymers are generally incompatible with each other. When two different polymers are mixed, the blend usually exhibits poor mechanical properties, e.g., tensile strength or ultimate elongation. A pair of polymers is seldom sufficiently compatible to give a blend exhibiting mechanical properties as good as those of the weakest polymer. However, when two polymers are sufficiently compatible, the resulting blend can exhibit a valuable combination of properties, i.e., in addition to good mechanical properties, the blends may also exhibit favorable characteristics such as temperature and solvent resistance of the individual polymers.

#It has been discovered that compositions comprising blends of thermoplastic poly(alkyl methacrylate) resin and epichlorohydrin rubber exhibit a valuable combination of properties. Generally, compositions comprising 1-99 parts by weight of poly(alkyl methacrylate) resin and, correspondingly, 99-1 parts by weight of epichlorohydrin rubber are moldable thermoplastic compositions exhibiting high strength and toughness. Compositions comprising 50 or more parts by weight of poly(alkyl methacrylate) resin, per 100 parts by weight of said resin and epichlorohydrin rubber combined, are thermoplastic compositions exhibiting improved impact resistance. Compositions comprising 50 or more parts by weight of epichlorohydrin per 100 total parts by weight of said rubber and resin are elastoplastic, i.e., they exhibit elastomeric properties, yet are processable as thermoplastics.

#Compositions illustrating the invention are prepared by charging poly(methyl methacrylate) resin, PMMA, and epichlorohydrin rubber, in the indicated amounts (all parts by weight) to a Brabender mixer at 180.degree. C. and a mixing speed of 80 rpm. The epichlorohydrin rubber is purchased Hydrin.RTM. 400 Elastomer, a sulfur vulcanizable grade comprising a copolymer of epichlorohydrin, ethylene oxide and sufficient olefinic monomer to give about 2% residual olefinic unsaturation. The PMMA is purchased Lucite.RTM. 147 acrylic resin which meets ASTM specification D-788 for grade 8 acrylic resin. The compositions are mixed for two minutes after the PMMA is melted; they are then removed from the mixer, cooled, returned to the mixer and mixed for 2-21/2 additional minutes. Test specimens are prepared by compression molding at 225.degree. C. and then evaluated. Compositions containing cured epichlorohydrin rubber are prepared in a similar manner except after the PMMA melts and a blend is formed, 10 parts by weight of dimethylol t-octylphenol curing resin, SP-1045, per 100 parts by weight of epichlorohydrin rubber are added and mixing is continued until maximum consistency is reached. The composition is removed from the mixer, cooled, then returned to the mixer and mixed for 2-21/2 additional minutes. Test specimens are prepared by compression molding as above. The effect of the proportions of epichlorohydrin rubber and poly(methyl methacrylate) resin in the blend is shown in Table 1. All compositions are processable as thermoplastics. The properties of blends in which the rubber is cured is shown in parentheses. The properties indicate that the two polymers are sufficiently compatible over the entire range of proportions. The data also show that compositions comprising up to 50 weight percent of PMMA are elastomeric. Curing the rubber in the blend increases solvent resistance of the composition and increases the tensile strength of compositions comprising greater proportions of epichlorohydrin rubber.

#Compositions comprising blends of different types of epichlorohydrin rubber are illustrated in Table 2. Stock 1 contains epichlorohydrin homopolymer rubber purchased as Hydrin.RTM. 100 Elastomer. Stock 2 contains epichlorohydrin rubber comprising a copolymer of epichlorohydrin and ethylene oxide purchased as Hydrin.RTM. 200 Elastomer. The blends are prepared by the same procedure as in Table 1. The data show that the polymers are sufficiently compatible and that compositions exhibiting a useful combination of properties are obtained.

#TABLE 1 __________________________________________________________________________ 1 2 3 4 5 6 7* 8* 9* __________________________________________________________________________ Epichlorohydrin Rubber 90 80 70 60 50 40 30 20 10 PMMA 10 20 30 40 50 60 70 80 90 Properties TS, MPa 0.2 0.8 5.1 10.9 20.0 20.0 25.2 31.4 62.6 (1.6) (4.4) (7.1) (11.8) (18.6) (21.2) (27.1) (31.5) (69.4) M100, MPa 0.3 0.5 0.6 1.3 4.8 12.9 21.7 -- -- (0.3) (0.5) (0.6) (1.3) (5.4) (13.0) (21.3) -- -- E, MPa 0.3 0.6 0.4 1.6 5.1 191 1027 1750 1997 (0.3) (0.5) (0.8) (1.6) (6.8) (181) (1033) (1649) (1735) Elong., % 2030 2600+ 1500 710 490 310 140 47 6 (2380) (1930) (1310) (800) (460) (300) (170) (52) (7) Tension Set, % 40 30 20 15 15 65 Bk Bk Bk (19) (18) (15) (14) (20) (68) Bk Bk Bk TSB, MPa 3.6 >22 82 88 118 82 62 46 66 (38) (89) (100) (106) (105) (84) (72) (48) (74) Shore D Hardness 5 8 9 16 31 55 65 72 76 (5) (8) (10) (16) (33) (60) (70) (75) (85) __________________________________________________________________________ *Stocks 7-9 were tested according to ASTM D170866 by pulling the specimen at one inch per minute to failure.