MXPA97004534A - Dob durometric handles - Google Patents

Abstract

A thermoplastic polyurethane or a handle containing double durometer thermoplastic polyurethane suitable for being grasped by a human being is described, and provides mechanical strength and chemical resistance, and which can be prepared without the use of additives.

Description

DOUBLE DUROMETRIC HANDLES DESCRIPTION OF THE INVENTION This invention relates to a double durometer thermoplastic polyurethane handle, made of rigid and soft thermoplastic polyurethanes. Manual grips for tools or sports equipment, which provide comfort to the user, are well known in the art. For example, U ke et al., In the patent of E. U.A. 4, 953, 862 discloses a sleeve of a semi-solid or rigid elastomeric material. Smith in the patent of E. U.A. 4,452, 862 discloses a handle made of rubber encapsulating a relatively hard plastic core. Coyle in the patent of E. U.A. No. 2,871,899 discloses a tool handle made of a soft plastic sleeve surrounding a rigid material. Kusznir in the patent of E. U .A. No. 4,721,021 discloses a handle made of a strong, durable plastic material and of a synthetic rubber pad of soft coupling foam extending longitudinally from the handle. The pad is compressed in engagement with the durable elastic material. In the art it has been an advance to provide a double durometer handle with both mechanical strength and chemical resistance, which can be prepared without the use of adhesives. The present invention is a dual durometer thermoplastic polyurethane handle suitable for being held by the hand of a human being, comprising: (a) a rigid thermoplastic polyurethane core having a glass transition temperature above 50 ° C , or a core containing a thermoplastic polyurethane having a flexural modulus of at least 7030 kg / cm2; and (b) a mild thermoplastic polyurethane material having a glass transition temperature below 25 ° C, or a thermoplastic polyurethane blend having a Shore A hardness not greater than 95, the mild polyurethane material or the mixture of thermoplastic polyurethane overlaying at least a portion of the rigid thermoplastic polyurethane or the thermoplastic polyurethane-containing material of (a), so that a hand, upon grasping the handle, is brought into contact with the soft thermoplastic polyurethane material. The handle of the present invention can be made without the use of an adhesive. The handle provides comfort, resistance, and chemical resistance. Figure 1 is a side view of a double durometer screwdriver having a handle made of thermoplastic polyurethanes of the present invention. Figure 2 is a cross-sectional view of the double durometer handle, taken on line 2-2 of Figure 1. Figure 3 is a side view of a double durometer screwdriver handle showing a sheath of a soft polyurethane material covering a core of a rigid thermoplastic polyurethane. The tool chosen to illustrate a preferred embodiment of the present invention is a screwdriver. It should be understood that a screwdriver handle is merely illustrative and is not intended to restrict the scope of the application. Figure 1 shows a screwdriver 10 having an elongated rigid thermoplastic polyurethane core 12 having a near end 16 and a distal end 18. The core 12 has a plurality of longitudinally extended slots, filled with grip strips 14 of soft thermoplastic polyurethane. The grip strips 14 exit above the surface of the core 12, so that the hand of a human can grasp the grip strips 14. The distal end 18 of the core 12 has a depression that receives a body extending toward in from the far end to receive a blade 20. The core may be a rigid thermoplastic polyurethane material (RTPU) or any material containing thermoplastic polyurethane, having a flexural modulus of at least 7030 kg / cm2. The RTPU refers to a thermoplastic polyurethane (TPU) having a Tg of at least 50 ° C. The RTPU has a hard segment that preferably constitutes 75, most preferably 90 to 100% by weight based on the total weight of the RTPU; and a soft segment that preferably constitutes from 0 to 25, most preferably 10% by weight, based on the total weight of the RTPU.

A TPU that is not by definition an RTPU may be used as the core of the handle of the present invention providing sufficient amounts of suitable fillers, reinforcing fibers, or other thermoplastic materials added to obtain the desired core flex modulus. Suitable fillers include talc, silica, mica, or glass beads, or mixtures thereof; the reinforcing fibers include glass, carbon, or graphite fibers, or mixtures thereof; and suitable thermoplastics include acrylonitrile-butadiene-styrene, polyacetal, nylon, polybutylene terephthalate, polyethylene terephthalate and ionomers. The core is superimposed by a soft thermoplastic polyurethane (STPU) or any TPU mixture having a Shore A hardness not greater than 95. The CTPU has a Tg not greater than 25 ° C. Preferably, the STPU has a hard segment of 15, preferably 20, preferably 25 to 50, most preferably 40, and preferably 30% by weight based on the total weight of STPU. Preferably, the STPU has a smooth segment of 50, most preferably 60, preferably 70 to 85, preferably 80, and most preferably 75% by weight based on the total weight of soft TPU. Examples of materials used to create a TPU blend having a not greater than 95 Shore A, include natural rubber, butyl triblock copolymers of styrene-isoprene-styrene and styrene-butadiene-styrene, and polyolefinic materials containing grafts of maleic anhydride. The quantities of such materials used, of course, will vary depending on the material and the desired hardness. The hard segment of the TPUs is a block derived from the reaction between a polyisocyanate and a difunctional chain extender. Preferred polyisocyanates include aromatic, aliphatic and cycloaliphatic diisocyanates and combinations thereof. Representative examples of these preferred diisocyanates can be found in, for example, the E patents. U .A. Nos. 4, 385, 133; 4, 522, 975; and 5, 167, 899. Highly preferred diisocyanates include 4,4'-diisocyanatodiphenylmethane, p-phenylene, 1, 3-bis (isocyanatomethyl) cyclohexane, 1, 2-cyclohexane diisocyanate, hexamethylene diisocyanate, dii diisocyanate 1, 5-naphthalene diisocyanate, 3, 3'-dimethyl-4,4'-biphenyl, 4,4'-diisocyanate-dicyclohexyl-methane, and 2,4-toluene diisocyanate or mixtures thereof. Most preferred are 4,4'-diisocyanatodicyclohexylmethane and 4,4'-diisocyanatodiphenylmethane. The most preferred is 4,4'-diisocyanato-diphenylethane. The difunctional chain extender is a polyol having a molecular weight no greater than 200. Preferred chain extenders are ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5- pentanediol, 1, 6-hexanediol , diethylene glycol, tetraethylenic glycol, neo-specialty glycol, 1,4-cyclohexanedimethanol, 1,4-bis-hydroxyethyl-hydroquinone, and mixtures thereof. The most preferred chain extenders are 1,4-butanediol, 1,6-hexanediol and 1,4-cyclohexanedimethanol, and mixtures thereof.

The soft segment of the TPUs is derived from a polyol, which has a molecular weight on the scale of 500, preferably 1000, most preferably 1500, to 6000, most preferably to 4000, and preferably to 3000. Preferably, the polyol is a polyester polyol or a polyether polyol or combinations thereof. Examples of preferred polyester polyols and polyether polyols include polycaprolactone glycol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene / polyoxypropylene glycol copolymer, polyoxytetramethylene glycol, polyethylene adipate, polybutidene adipate, polyethylene-butylene adipate, and polycarbonate glycol ( hexamethylene), or combinations thereof. In a preferred embodiment, the handle comprises a core of RTPU placed on it by an STPU. The core of RTPU is preferably a thermoplastic resin designed by engineering, ISOPLAST ™, (trademark of The Dow Chemical Company) and STPU is preferably a polyurethane elastomer, PELLETHANE ™, (trademark of The Dow Chemical Company), having a Shore A hardness of 90 or less. Preferably, the polyurethane elastomer, PELLETHA N E ™, has a Shore A hardness of 80 or less, most preferably 75 or less. The handle of the present invention may be transparent or opaque, but preferably is transparent. The shape of the handle is not critical, although it is preferred that it be elongated. The handle can be produced through a variety of techniques, including coextrusion, coinjection, and overmolding of two shots. In the coextrusion technique, for example, a primary extruder extrudes the core of rigid thermoplastic polyurethane, which is in grooves, while a second extruder extrudes the soft thermoplastic polyurethane through a crosshead die into the grooves of the rigid core. The distribution and the amount of STPU superimposed on the core are not critical since the user perceives the STPU when it grasps the handle. The core is preferably grooved, and the overlying material is preferably contained in and exits the grooves of the core. The configuration of the dual durometer handle can be that of an internal core surrounded by an STPU sheath or a material containing soft TP U. This method can be produced, for example, by means of a two-shot overmolding process. Any procedure that is used, the core and the superposed material are adhered to each other with glue, solvent, or any other adhesive. Although not bound by theory, it is believed that covalent bonds are formed across the abutting surface of STPU-RTPU, through depolymerization and repolymerization during processing of the handle, where the hydroxyl groups released from one of the TPUs react with the isocyanate groups released from the other TPUs. It is also possible that the adhesion is present through the diffusion of polymer chains through the abutting surface of RTPU-STPU. The handle can be any type of handle that is suitable to be grasped by a human being. Examples include, but are not limited to, handles for sports equipment, such as baseball bats, racquets, golf clubs, and towing cables for water skiing; handles for household items, such as refrigerator doors, oven doors, manual mixers, and door knobs; and hand tools, such as hammers, saws, mechanical drills, torque wrenches and, of course, screwdrivers.

Claims (2)

1 - . 1 - A double durometer thermoplastic polyurethane handle suitable for being grasped by the hand of a human being, comprising: (a) a core of rigid thermoplastic polyurethane having a glass transition temperature above 50 ° C, or a core containing a thermoplastic polyurethane having a flexural modulus of at least 7030 kg / cm2; and (b) a mild thermoplastic polyurethane material having a glass transition temperature below 25 ° C, or a thermoplastic polyurethane blend having a Shore A hardness not greater than 95, the mild polyurethane material or the mixture of thermoplastic polyurethane overlaying at least a portion of the rigid thermoplastic polyurethane or the thermoplastic polyurethane-containing material of (a), so that a hand, upon grasping the handle, is brought into contact with the soft thermoplastic polyurethane material. 2. The handle according to claim 1, comprising a soft thermoplastic polyurethane material having a glass transition temperature below 25 ° C, overlaying a core of rigid thermoplastic polyurethane having a glass transition temperature above 50 ° C. 3. The handle according to claim 1, wherein the rigid thermoplastic core is elongated and has a plurality of longitudinally extended grooves, wherein the soft thermoplastic material is contained, so that the soft thermoplastic material exits above the core. core surface of rigid thermoplastic polyurethane. 5. The handle according to claim 3, wherein 75 to 100% by weight of the rigid thermoplastic polyurethane core contains hard segments derived from a diisocyanate selected from 4,4'-diisocyanatodiphenylmethane, p-phenylene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,

2-cyclohexanediisocyanate , hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-biphenyl, 4,4'-diisocyanate-dicyclohexyl-methane, or 2,4-toluene diisocyanate. 6. The handle according to claim 5, wherein at least 90 to 100% by weight of the rigid thermoplastic polyurethane core, and 10 to 25% by weight of the soft thermoplastic polyurethane material comprises portions derived from a diisocyanate selected from 4,4'-diisocyanatodiphenylmethane and 4,4'-diisocyanatodicyclohexylmethane. 7 - The handle according to claim 6, wherein the rigid thermoplastic polyurethane core is prepared through the reaction of 4,4'-diisocyanatodiphenylmethane and a diol selected from 1,6-hexanediol, 1,4-butanediol, or 1, 4-cyclohexanedimethanol. 8. The handle according to claim 7, wherein the mild thermoplastic polyurethane is prepared by the reaction of 4,4'-diisocyanatodiphenylmethane no; a diol selected from 1,4-butanediol, 1,6-hexanediol or 1,4-cyclohexanedimethanol; and a polyol having a molecular weight in the range of 1000 to 2000 and which is selected from the group consisting of polycaprolactone diol glycol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polybutylene adipate, polyethylene-butylene adipate , or poly (hexamethylene) carbonate glycol. SUMMARY A thermoplastic polyurethane or a handle containing double durometer thermoplastic polyurethane suitable for being grasped by a human being is described, and provides mechanical strength and chemical resistance, and which can be prepared without the use of additives.