Title of Invention: Transparent molding materials resistant to stress cracking and having improved toughness/rigidity ratio
Abstract: Thermoplastic molding materials contain a mixture of. (A) a methacrylate polymer, PA1 (B) a copolymer of vinylaromatic monomers and vinyl cyanide, PA1 (C) a graft copolymer comprising a core and a graft shell and PA1 (D) a further graft copolymer comprising a core and a graft shell,. the average particle size (d.sub.50)-C of the graft copolymer (C) being from 25 to 60 nm and that of the graft copolymer (D) being from 90 to 300 nm and the ratio of the average particle size (d.sub.50)-C to (d.sub.50)-D being kept in the range from 2:1 to 5:1.
Detailed Description: Part PAC: EXAMPLES
Part PAR: In the examples and comparative experiments which follow, ratios and percentages are by weight.
Part PAR_2: The refractive index n.sub.D.sup.25 was determined using an Abbe refractometer by the method for measuring the refractive indices of solids (cf. Ullmanns Encyklopadie der technischen Chemie, Volume 2/1, page 486, editor E. Foerst; Urban & Schwarzenberg, Munich-Berlin 1961).
Part PAR_3: The multiaxial toughness Wg was determined according to DIN 53 443 and the rigidity (modulus of elasticity) according to DIN 53 475.
Part PAR_4: The average particle size (d.sub.50)-C or (d.sub.50)-D and the particle size distribution were determined from the integral mass distribution. The average particle sizes in all cases are the weight average of the particle sizes as determined by means of an analytical ultracentrifuge according to the method of W. Scholtan and H. Lange, Kolloid-Z, and Z.-Polymere 250 (1972), 782-796. The ultracentrifuge measurement gives the integral mass distribution of the particle diameter of a sample. From this it is possible to determine the percentage by weight of the particles which have a diameter equal to or smaller than a certain size. The average particle diameter, which is also referred to as the d.sub.50 value of the integral mass distribution, is defined as the particle diameter at which 50% by weight of the particles have a diameter smaller than the diameter which corresponds to the d.sub.50 value. Likewise, 50% by weight of the particles then have a larger diameter than the d.sub.50 value.
Part PAR_5: The yellowness index YI is based on chromaticity coordinates calculated from the transmission spectrum according to DIN 5036. The illuminant D65 and the standard wide-field observer form the base.
Part PAR_6: The determination of the scattered light fraction was likewise carried out according to DIN 5036.
Part PAR_7: The Example and Comparative Examples A to D, the polymers defined in more detail below were used:
Part PA1: A Copolymer prepared from methyl methacrylate (MMA) and methyl acrylate (MA) in the ratio of 94:6 (n.sub.D.sup.25 =1.492, M.sub.w =110,000 g/mol); PA1 B Copolymer prepared from styrene (S) and acrylonitrile (AN) in the ratio of 81:19 (M.sub.w =250,000 g/mol, n.sub.D.sup.25 =1.575); PA1 C Graft copolymer prepared from 45 parts by weight of a mixture consisting of 51 parts by weight of MMA, 44 parts by weight of styrene and 5 parts by weight of n-butyl acrylate, polymerized in the presence of 55 parts by weight of a core obtainable by polymerization of 72 parts by weight of butadiene and 28 parts by weight of styrene (n.sub.D.sup.25 =1.5402, d.sub.50-C =110 nm); PA1 C.sup.1 Graft copolymer prepared from 45 parts by weight of a mixture consisting of 51 parts by weight of MMA, 44 parts by weight of styrene and 5 parts by weight of n-butyl acrylate, polymerized in the presence of 55 parts by weight of a core obtainable by polymerization of 72 parts by weight of butadiene and 28 parts by weight of styrene (n.sub.D.sup.25 =1.5402, d.sub.50-C =53 nm); PA1 D.sup.1 Graft copolymer prepared from 45 parts by weight of a mixture consisting of 51 parts by weight of MMA, 44 parts by weight of styrene and 5 parts by weight of n-butyl acrylate, polymerized in the presence of 55 parts by weight of a core obtainable by polymerization of 72 parts by weight of butadiene and 28 parts by weight of styrene (n.sub.D.sup.25 =1.5402, d.sub.50-C =195 nm); PA1 D.sup.2 Graft copolymer prepared from 45 parts by weight of a mixture consisting of 51 parts by weight of MMA, 44 parts by weight of styrene and 5 parts by weight of n-butyl acrylate, polymerized in the presence of 55 parts by weight of a core obtainable by polymerization of 72 parts by weight of butadiene and 28 parts by weight of styrene (n.sub.D.sup.25 =1.5402, d.sub.50-C =100 nm); PA1 D.sup.3 Graft copolymer prepared from 45 parts by weight of a mixture consisting of 51 parts by weight of MMA, 44 parts by weight of styrene and 5 parts by weight of n-butyl acrylate, polymerized in the presence of 55 parts by weight of a core obtainable by polymerization of 72 parts by weight of butadiene and 28 parts by weight of styrene (n.sub.D.sup.25 =1.5402, d.sub.50-C =310 nm).
Part TBL: TABLE __________________________________________________________________________ Ratio of Scattered Components particle Impact Rigidity Yellowness light [in % by weight] sizes strength [modulus index fraction A B C D d.sub.50 -C/d.sub.50-D [Wg] of elasticity] [YI] [%] __________________________________________________________________________ Comparative A[28.5] B[35.5] C[36.0] -- -- 12.4 1970 4.9 3.8 Example A Example A[28.5] B[35.5] C.sup.1 [28.8] D.sup.1 [7.2] 3.7 19.8 2000 2.5 2.9 Comparative Af28.5] B[35.5] C.sup.1 [28.8] D.sup.2 [7.2] 1.9 6.2 2010 3.7 3.5 Example B Comparative A[28.5] B[35.5] C.sup.1 [28.8] D.sup.3 [7.2] 5.8 21.1 1950 4.0 5.3 Example C __________________________________________________________________________
Part PAR_8: A comparison of the example according to the invention with Comparative Examples A to C shows, inter alia, that the novel use of graft copolymers C and D having exactly defined average particle sizes d.sub.50-C and d.sub.50-D and a specific ratio of the particle sizes d.sub.50-C /d.sub.50-D leads to molding materials exhibiting less yellowing and high transparency [smaller scattered light fraction]. Moreover, the novel thermoplastic molding materials are distinguished by an improved toughness/rigidity ratio.


{'bibliographic_information': "{'Patent Number': '059690429', 'Series Code': '8', 'Application Number': '9832335', 'Application Type': '1', 'Art unit': '171', 'Application Filing Date': '19980113', 'Title of Invention': 'Transparent molding materials resistant to stress cracking and having improved toughness/rigidity ratio', 'Issue Date': '19991019', 'Number of Claims': '7', 'Exemplary Claim Number(s)': '1', 'Primary Examiner': 'Mullis; Jeffrey C.'}", 'source_file': './grant/1999/pftaps19991019_wk42.txt', 'source_data': 'USPTO-Grant'}