Hyperbranched amphiphilic polymeric additives and polymer compositions with increased surface energy

#The present invention relates to novel asymmetric hyperbranched copolymers, a process for their preparation, and to their use as polymer additives that migrate to the surface of a polymer and have beneficial effects on the surface properties of the polymer.

#Random hyperbranched polymers are known. Hyperbranched polymers are obtained from the random polymerization of monomers in the presence of at least one polyfunctional monomer capable of introducing branching. Such a synthetic scheme is shown by Hawker and Devonport in “Step-Growth Polymers for High-Performance Materials: New Synthetic Methods,” Hedrick, J. L. and Labadie, J. W., Eds., Am. Chem. Soc., Washington, D.C., 1996, pp. 191-193. Hult, et al., in “Advances in Polymer Science,” Vol. 143 (1999), Roovers, J., Ed., Springer, New York, pp. 1-34, present a review of hyperbranched polymers.

#U.S. Pat. No. 3,441,953 teaches that discrete esters of certain hindered dihydroxycarboxylic acids possess desirable properties and which may be used as textile softeners, lubricants, wetting and rewetting agents and textile assistants and which impart properties such as improved softness, scorch resistance, wettability and rewettability, static control, lubricity, tensile and tear strengths and sewability to textile materials. An example is given where polyethylene glycol (PEG) is reacted with dimethylolpropionic acid (2,2-bis(hydroxymethyl)propionic acid or BMPA) to form a PEG monoester of BMPA. This diol-ester is subsequently reacted with a tallow fatty acid to form the tallow fatty acid diester. In fact, it is believed that in the first step that a discrete PEG-BMPA monoester is not formed but that some hyperbranching must have occurred, resulting in a hyperbranched polyester.

#A series of various amphiphilic block copolymers of the present invention are prepared according to the following general procedure. Comparative examples of linear amphiphilic polymers are prepared by the same procedure with the exclusion of the multi-functional monomer. The comparative amphiphilic polymers are represented by numbers 1 and 2 of Table 1 and are representative of state of the art nonionic surfactants employed for increasing the surface energy of polyolefins. The copolymers of the instant invention are represented by numbers 3-25. The linear hydrophilic polymer component (A) is derived from either poly(ethylene glycol) monomethyl ether (MPEG) or poly(ethylene glycol) (PEG), and is represented in Table 1 by the symbol “A”. The molecular weight ({overscore (M)}n, daltons) of the hydrophilic polymer component is given in Table 1. The random hyperbranched component(B) is derived from dimethylolpropionic acid [2,2-bis(hydroxymethyl)propionic acid (BMPA)]. The lipophilic terminal groups are derived from the corresponding long-chain alkylcarboxylic acid (“LCA” in Table 1). The use of stearic acid results in a C17H35 lipophilic group. The last column of Table 1 represents the ratio of components employed in the preparation of the corresponding copolymer. The copolymers of the instant invention comprise a mixture of structures as discussed supra and similar to compounds of formulae (1)-(4).

#A reactor is charged with 89.9 g (316 mmol) of stearic acid, 31.8 g (237 mmol) of BMPA, and 27.8 g (79 mmol) of MPEG350 ({overscore (M)}n 350 daltons, eq. wt. 349). Under a constant flow of nitrogen the temperature of the solid mixture is increased to 110° C., at which point the solid mixture becomes a homogeneous colorless liquid. Stirring is initiated and the reaction is allowed to purge for 30 min., and then 750 mg (3.9 mmol) of p-toluenesulfonic acid are added. The reaction temperature is increased to 160° C. Water of condensation immediately collects in a trap attached to the reactor. After 4 h, the reaction temperature is increased between 180-190° C. Stirring at this temperature is continued until the acid number shows little appreciable decrease. Stirring is stopped and the hot liquid is poured into a glass container and allowed to equilibrate to room temperature under ambient conditions. The structure of the (A)(B) block copolymer of the instant invention is confirmed by 1H, 13C FT-NMR spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). {overscore (Mn)}=1400, {overscore (M)}w/{overscore (M)}n=1.2, Tm=44° C., acid number=29.0 mg KOH/g, hydroxyl number=31.5 mg KOH/g, yield is quantitative.

#Likewise, the structures of the other (A)(B) or (B)(A)(B) block copolymers of the instant invention, as well as the comparative linear copolymers, are confirmed by the same analytical techniques.