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
1998-08-11
2001-01-16
Short, Patricia A. (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...
C525S460000
Reexamination Certificate
active
06174959
ABSTRACT:
The invention relates to thermoplastic molding compositions which contain thermoplastic polyurethane and a copolymer of at least one monomer containing olefinic unsaturation; more particularly, the thermoplastic polyurethane is characterized in that it is a reaction product of an aliphatic isocyanate.
BACKGROUND OF THE INVENTION
Thermoplastic polyurethane resins (TPU) are generally produced by reacting a polyol, a diisocyanate and a glycol chain extender. The properties of these resins depend to a large extent on the relative amounts of the reactants. These resins have been blended with other thermoplastic resins to produce compositions having a variety of properties making them suitable for a host of applications. Although non-polar polyethylene, or polypropylene, and polar TPU have been viewed as incompatible one with the other, such blends are desirable and some, containing small amounts of the olefins have been reported.
For instance, U.S. Pat. No. 3,929,928 indicates that mill blending of a thermoplastic polyurethane with polyethylene results in severe plate-out due to incompatibility of the two polymers. Researchers have reported in
Organic Coatings Plastics Chemistry
, Vol. 40, page 664 (1979) that it was impossible to prepare with a roll mill useful test specimens at any polyurethane/polyethylene blend ratios. Similarly, Walker's
Handbook of Thermoplastic Elastomers
, Section 5.4.17, reports that low density polyolefin modifications of polyurethane polymers must be maintained below 3 percent to avoid adverse effects due to incompatibility of the two polymers. Although U.S. Pat. No. 3,272,890 purports useful blends of polyolefin and soft polyurethane polymers, such blends are polyolefin based, containing less than 25 percent by weight polyurethane polymer where polyurethane polymer contents above 25 percent are incompatible and cannot be molded into useful plastic containers. Crystalline high density polyethylene or polypropylene polymeric blends are even more difficult to prepare due to incompatibility of the crystalline polyolefins with polyurethanes. Useful blends of thermoplastic polyurethane elastomers containing less than 15 percent by weight neutralized ethylene/carboxylic acid copolymers are disclosed in U.S. Pat. No. 4,238,574 to provide elastomeric blends useful in blow-molding operations.
U.S. Pat. No. 4,975,207 disclosed a blend of TPU and a carbonyl-modified polyolefin. U.S. Pat. No. 5,623,019 disclosed a compatibilized composition containing TPU and polyolefin. A particularly structured copolymer which contains blocks of monoalkylene arene and conjugated diene is said to compatibilize the components.
U.S. Pat. No. 4,990,557 disclosed the preparation of mechanically stabilized compatible blends of TPU and an at least mostly crystalline polyolefin by a high shear mixing of a melt of these polymers.
DETAILED DESCRIPTION OF THE INVENTION
The thermoplastic molding composition in accordance with the present invention comprise
(i) 99 to 50, preferably 95 to 60 percent of a thermoplastic polyurethane, the molecular structural of which contains ether units and units derived from an aliphatic isocyanate, and
(II) 1 to 50, preferably 5 to 40 percent of a copolymer, the molecular structure of which contains units derived from monomers containing olefinic unsaturation.
The thermoplastic polyurethanes suitable in the preparation of the inventive composition are known and are commercially available, for instance, under the Trademark Texin, from Bayer Corporation. Typically, the suitable TPU has a melt flow rate of about 4 to 100, more preferably 10 to 90 g/10 min., per ASTM D-1238.
These resins are prepared by reacting a suitable polyol, polyisocyanate and a chain extender by methods which have long been documented in the relevant literature.
The polyols suitable in the preparation of the TPU of the present invention are characterized in that they contain at least one ether structural unit. These, often referred to as polyether polyols, have a number average molecular weight of at least 400, preferably at least 1250 and most preferably at least 2,000 but less than 20,000, preferably less than 10,000, and more preferably less than 8,000. The functionality of the polyol, the number of isocyanate-reactive hydrogen atoms per molecule, is preferably not greater than 6 and more preferably the functionality is in the range of 2 to 4. The suitable polyether polyols include polyoxyethylene glycols, polyoxypropylene glycols, copolymers of ethylene oxide and propylene oxide, polytetramethylene glycols, copolymers of tetrahydrofuran and ethylene oxide and/or propylene oxide. The preferred polyether polyols are copolymers of ethylene and propylene oxide.
It is not unusual, and in some cases it might be advantageous, to employ more than one polyol. Exemplary of such additional polyols are polyester polyols, hydroxy terminated polycarbonates, hydroxy terminated polybutadienes, hydroxy terminated polybutadiene-acrylonitrile-copolymers and hydroxy terminated copolymers of dialkyl siloxane and mixtures in which any of the above polyols are employed as a minor component (less than 50% relative to the weight of the mixture with polyether polyols). The preferred embodiment entails polyether polyol alone.
Any of the organic, aliphatic polyisocyanates, preferably diisocyanates which are known in polyurethane chemistry, may be used in preparing the TPU of the present invention. Illustrative of such isocyanates are hexamethylene diisocyanate, isophorone diisocyanate, methylene bis(cyclohexyl isocyanate) as well as the 4,4′-isomer, 2,4′-isomer and mixtures thereof, cyclohexylene diisocyanate, as well as its 1,2-isomer, 1,3-isomer, and 1,4-isomer, 1-methyl-2,5-cyclohexylene diisocyanate, 1-methyl-2,4-cyclohexylene diisocyanate, 1-methyl-2,6-cyclohexylene diisocyanate and 4,4′-isopropylidene bis(cyclohexyl isocyanate).
Glycols suitable as chain extenders in the present context are also known. Typically, the extenders can be aliphatic straight and branched chain diols having from 2 to 10 carbon atoms, inclusive, in the chain. Illustrative of such diols are ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, and the like; 1,4-cyclohexanedimethanol; hydroquinone bis-(hydroxyethyl)ether; cyclohexylene diols (1,4-, 1,3-, and 1,2-isomers), isopropylidene bis(cyclohexanols); diethylene glycol, dipropylene glycol, ethanolamine, N-methyidiethanolamine, and the like; and mixtures of any of the above. In some cases minor proportions (less than about 20 equivalent percent) of the difunctional extender may be replaced by trifunctional extenders without detracting from the thermoplasticity of the resulting TPU; illustrative of such extenders are glycerol, trimethylol-propane and the like. While any of the diol extenders referred to above can be employed alone, or in admixture, it is preferred to use any of 1,4-butane-diol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, ethylene glycol, and diethylene glycol, either alone or in admixture with each other or with one or more aliphatic diols previously named. Particularly preferred diols are 1,4-butanediol, 1,6-hexanediol and 1,4-cyclohexane dimethanol. Also included among the chain extenders which can be used in preparing TPU are adducts obtained by an aliphatic diol or triol such as 1 ,4-cyclohexane dimethanol, neopentyl glycol, hexane-1,2-diol, ethylene glycol, butane-1,4-diol, trimethylolpropane, and the like, with caprolactone in a mole ratio of from 0.01 to 2 moles of caprolactone per mole of diol or triol.
The equivalent proportions of polymeric diol to said extender can vary considerably depending on the desired hardness for the TPU product. Generally, the proportions fall within the respective range of from about 1:1 to about 1:20, preferably from about 1:2 to about 1:10. At the same time, the overall ratio of isocyanate equivalents to equivalents of active hydrogen containing materials is within the range of 0.90:1 to 1.10:1, and preferably, 0.95:1 to 1.05:1.
While any
Archey Rick L.
Ciebien Jane F.
Noble H. Lee
Bayer Corporation
Gil Joseph C.
Preis Aron
Short Patricia A.
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