Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-08-16
2001-04-17
Buttner, David J. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S166000, C525S176000, C525S179000, C525S183000
Reexamination Certificate
active
06218467
ABSTRACT:
SPECIFICATION
State of the art
With few exceptions, such as polymethyl methacrylate and acrylonitrile/butadiene/styrene copolymer (ABS), polymethyl methacrylate and PVC or polystyrene (PS), and poly (2,6-dimethyl-1,4-phenylene oxide), different plastics are incompatible with one another and cannot be mixed with one another for energetic reasons [see T. K. Kwei, H. L. Frisch, Macromolecules, 11, 1267 (1978)]. Homogeneous mixtures of different plastics on the molecular level are instead the exception. It is technically difficult to prepare a mixture or an alloy or a composite or a blend of polymers incompatible with one another, and this usually leads to materials with poorer practical properties than the individual components (separation of the blend, delamination of the composite) because of phase separation. However, it often seems technically desirable to be able to combine with one another the good material characteristics of different plastics. Thus, for example, polyamides (PA) are distinguished by their excellent chemical resistance, their flow properties in processing, and their heat distortion resistance; on the other hand, they are deficient in dimensional stability.
U.S. Pat. No. 4,946,918 (Nippon Oil and Fats Co.) describes compatibilizers for mixtures of synthetic resins, for example different types of polyamide, polycarbonate/ABS varieties, and polycarbonate/poly(butylene terephthalate) varieties. These compatibilizers are copolymers of maleic anhydride, maleic acid, or maleic acid salts with polyoxyalkylenes.
EP-A 113 105 describes a method for preparing heat distortion-resistant molding compositions, with a mixture of a copolymer (I) consisting of methyl methacrylate, vinylaromatic, and maleic anhydride, and a copolymer (II) consisting of methyl methacrylate and optionally other comonomers being produced.
DE-A 44 40 219 describes a method for preparing copolymers of alkyl methacrylate, vinylaromatics, and maleic anhydride. The polymerization can take place at low temperatures in the range, for example, of 50 to 60° C. in a polymerization vessel. The block polymer can then be taken out, ground, and subjected to degassing extrusion followed by granulation.
Acrylonitrile/butadiene/styrene copolymers (ABS), for example, show very good impact strength and notched impact strength even at low temperatures, good strength and dimensional stability, but with only poor chemical resistance and inadequate flowability and heat distortion resistance.
It is known from studies described in the literature [M. Stolp, H.-J. Radusch; Kunststoffe 85, 4, (1995)] that the two materials ABS and PA are incompatible with one another and even the admixing of only small fractions of polyamide with acrylonitrile/butadiene/styrene copolymers leads to distinct embrittlement of the ABS. This embrittlement of plastic parts also hinders recycling, among other problems.
The purpose of this invention therefore consists of finding a way to be able to prepare certain polymer blends or composites from plastics incompatible with one another, at least retaining the positive material properties of the individual component.
Specifically in question are blends of polymethacrylate-compatible plastics (PC), for example polymethyl methacrylate (PMMA), acrylonitrile/butadiene/styrene copolymers (ABS), or polyvinylidene fluoride (PVDF), with polymers (PN) that contain at least one terminal nucleophilic group (such as an amino or hydroxy group, for example). Polyamides (PA) and polyesters may be mentioned here as examples of the polymers (PN).
Preferred are polyamides (PA) such as PA3, PA4, PA5, PA6, PA7, PA8, PA9, PA10, PA11, PA12, for example, that are prepared by polycondensation of &ohgr;-amino acids or by polymerization of the corresponding lactams. Polyesters that may be mentioned in particular are polyethylene terephthalate and polybutylene terephthalate.
Polyamides are preferred, especially PA6, PA6,6, PA6,10, PA10, PA11, PA12, with the “double-numbered” polyamides (PA6,6, PA6,10) being prepared by reaction of &agr;,&ohgr;-diamines with &agr;,&ohgr;-dicarboxylic acids (in this regard, for example, see Elias, H. G. (1981) Makromolekule: Structure, Properties, Syntheses, Substances, Technologies; 4th completely revised and substantially expanded edition, Huthig and Wepf Verlag; Chapter 28.2 “Polyamides”, pp. 796 ff).
It has been found that the problem is solved surprisingly by the use of a polymeric modifier (CP) consisting of the monomeric components methyl methacrylate (MMA), maleic anhydride (MA), and optionally other radical-polymerizable comonomers containing no other functional groups.
The other comonomers are not critical for the feasibility of the invention, if they have no functional groups, e.g. acid or hydroxy groups, other than the functional vinyl group entering into radical polymerization. Examples of suitable comonomers are esters of methacrylic acid (e.g. ethyl methacrylate, butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate), esters of acrylic acid (e.g. methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, cyclohexyl acrylate) or styrene and styrene derivatives, for example such as a-methylstyrene or p-methylstyrene. Reactive bonding leads to modification of the polymer (PN) that contains at least one terminal nucleophilic group, and thus to a distinct improvement of the property profile of the aforementioned polymer mixtures or polymer composites. The modification can take place, for example, by melting mixed granulates of the copolymer (CP) and of the polymer (PN).
The term “mixtures and polymer composites” used below therefore designates the physical and optionally chemical union of the copolymer pursuant to the invention with the polymers (PN) to be modified and/or the polymethacrylate-compatible plastics (PC).
Instead of maleic anhydride, in principle another copolymerizable acid or a copolymerizable anhydride can also be used, for example such as maleic acid, itaconic acid, itaconic anhydride, fumaric acid, or glutaric anhydride. However, maleic anhydride is especially preferred.
The invention relates to mixtures or polymer composites of the copolymer (CP) consisting of
70-99.9 wt. % methyl methacrylate,
0.1-5 wt. % maleic anhydride, and
0-25 wt. % of other vinyl-copolymerizable monomers that have no functional groups other than the vinyl function
with a polymethacrylate-compatible plastic (PC) and a polymer (PN) that contains at least one terminal nucleophilic group.
Copolymers of MMA and MA are known from the literature. Thus, a method is described in German Unexamined Patent Application DE 2,724,360 (BAYER AG) for preparing low-residual-monomer molding compositions; among the examples is also found a cyclohexyl methacrylate/MMA/MA terpolymer. Polymerization in this case occurs with an internal reactor temperature of 140° C. up to 40% conversion; the polymer syrup is then concentrated in a special degassing device and is degassed in another unit process to a residual monomer content of <0.1% in a screw machine.
Copolymers of 67-99 wt. % MMA with 1-33 wt. % MA are claimed in Jpn. Kokai Tokkyo Koho JP 60,141,708 (C.A. 104:6583e). Polymerization in this case occurs at 160° C. to 62% conversion. The syrup is then heated to 200° C. and then degassed at 230° C. in an extruder.
Both of the methods described are technically complicated and economically unattractive, and also have the drawback that large amounts of unreacted monomers have to be removed from the product by various degassing devices. The use of the products thus obtained as polymeric modifiers for incompatible polymer mixtures or composites is not mentioned.
The copolymers (CP) pursuant to the invention consist of:
70-99.9 wt. % methyl methacrylate,
0.1-5 wt. % maleic anhydride, and
0-25 wt. % of other methacrylate esters, acrylate esters, or styrene derivatives that contain no other functional groups.
They are prepared by bulk polymerization of the monomers with the addition of radical initiators and molecular weight regulators at temperatures <80° C. to conversions >95%
Jaksch Hermann
May Michael
Numrich Uwe
Rueppel Mona
Wicker Michael
Buttner David J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Roehm GmbH
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