EP1228500B1

EP1228500B1 - Drumsticks made from liquid crystalline polymer

Info

Publication number: EP1228500B1
Application number: EP00976821A
Authority: EP
Inventors: Joel David Citron; Michael Robert Samuels
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 1999-11-12
Filing date: 2000-11-02
Publication date: 2003-06-11
Anticipated expiration: 2020-11-02
Also published as: EP1228500A1; DE60003329T2; CA2384743A1; DE60003329D1; WO2001035386A1

Description

Liquid crystalline polymers (LCPs) are useful in drumsticks, the drumstick being completely made from a LCP (plus any fillers, antioxidants, reinforcing agents, pigments dyes or other materials normally found in thermoplastics.), or the drumstick may have one or more LCP inserts.

TECHNICAL BACKGROUND

Drumsticks for percussionists have traditionally been most often made from wood, usually a hardwood such as American hickory which is straight grained and readily shaped. Usually a rod of the wood is turned to produce the desired shape, the wood is smoothed if necessary, and then coated with a finish. Although wood sticks have been used for many years, and have been found satisfactory, they have some drawbacks, such as a tendency to break along the grain. Therefore improved drumsticks are needed.

Thermoplastics have been thought of for drumsticks, but the stiffness and other properties of most thermoplastics are too low to afford good drumsticks. Recently [see Modern Plastics, vol. 76, No. 10, p. 41 (Oct. 1999)] it has been reported that oriented polymers, such as oriented polypropylene, can be used for drumsticks, but these sticks are relatively expensive to form, requiring one or more orientation steps, then turning (much as in making wood drumsticks) to form the final shape. This manufacturing process does not allow for taking advantage of some of properties of thermoplastics, such as inexpensive and easy formability. Drumsticks which are made from LCPs, or which contain LCP inserts, may be simply melt formed, as by injection molding, and have the requisite properties for drumsticks without further processing.

SUMMARY OF THE INVENTION

This invention concerns a drumstick, comprising one or more thermotropic liquid crystalline polymer (s).

The invention also includes an embodiment wherein a thermotropic liquid crystalline polymer forms a core overmolded with a second polymer, which may be either a thermoplastic polymer or a thermoset polymer.

A further embodiment features a thermotropic liquid crystalline polymer overmolded over an isotropic polymer, preferably a thermoplastic core.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a cross section of a drumstick towards the handle end having an LCP core.

Figure 2 shows a longitudinal cross section of a drumstick having an LCP core and a partial thermoplastic overmolding.

DETAILS OF THE INVENTION

The drumstick described herein comprises a thermotropic liquid crystalline polymer. By comprises is meant that the drumstick contains at least some LCP, and may contain other materials, such as other thermoplastics. The LCP (or other polymer) may be blended with one or more fillers, antioxidants, reinforcing agents, pigments, dyes, or other materials normally found in thermoplastics. The other ingredients (if any) in the LCP or other polymer may be used to change the appearance (color for instance) of the drumstick, physical properties, and/or may also affect the acoustical properties of the drumstick.

Blends of LCPs with other thermoplastics may be also be used in the drumstick in place of "pure" LCP. If such a blend is used, it is preferred that the LCP be in a continuous phase.

By an LCP is meant a polymer that is anisotropic when tested in the "TOT Test" described in U.S. Patent 4,118,372. Any thermotropic LCP may be used in this process. Suitable thermotropic LCPs, for example, are described in U.S. Patents 3,991,013, 3,991,014 4,011,199, 4,048,148, 4,075,262, 4,083,829, 4,118,372, 4,122,070, 4,130,545, 4,153,779, 4,159,365, 4,161,470, 4,169,933, 4,184,996, 4,189,549, 4,219,461, 4,232,143, 4,232,144, 4,245,082, 4,256,624, 4,269,965, 4,272,625, 4,370,466, 4,383,105, 4,447,592, 4,522,974, 4,617,369, 4,664,972, 4,684,712, 4,727,129, 4,727,131, 4,728,714, 4,749,769, 4,762,907, 4,778,927, 4,816,555, 4,849,499, 4,851,496, 4,851,497, 4,857,626, 4,864,013, 4,868,278, 4,882,410, 4,923,947, 4,999,416, 5,015,721, 5,015,722, 5,025,082, 5,086,158, 5,102,935, 5,110,896, and 5,143,956, and European Patent Application 356,226. Useful thermotropic LCPs include polyesters, poly(ester-amides), poly(ester-imides), and polyazomethines. Preferred thermotropic LCPs are polyesters or poly(ester-amides), and it is especially preferred that the polyester or poly(ester-amide) is partly or fully aromatic.

If the drumstick is made completely from LCP or an LCP composition (meaning the LCP plus any fillers, antioxidants, reinforcing agents, pigments dyes or other materials normally found in thermoplastic.) the drumstick may simply be melt formed in any desired shape or size from the LCP (see for instance H. Mark, et al., Ed., Encyclopedia of Polymer Science and Engineering, Vol. 8, John Wiley & Sons, New York, 1987, p. 102-139). For example, the drumstick may be injection molded. In order to achieve a high degree of stiffness along the length of the drumstick (as it is in a wood drumstick), it is preferred to place the gate of the mold at one end of drumstick cavity, preferably the end which is the handle (not the end for hitting the drum or other instrument). In this instance it is preferred that the LCP contain a filler or reinforcing agent, such as talc, (hollow) glass spheres, or sawdust (the latter may allow the drumstick to look like wood). The filler or other added ingredients may be chosen to adjust the weight of the stick, by choosing a filler/reinforcing agent with an appropriately low or high density. It is preferred that the filler(s) and other ingredients present (but not including any polymer in an LCP/other polymer blend) be about 5 to about 40 percent by weight of that mixture.

The LCP may also be present as one or more cores (also called inserts or insert molding) or the outer material of the drumstick. In either case the LCP lends stiffness and other desirable properties to the drumstick, while reducing the amount of (often) relatively expensive LCP in favor of a cheaper thermoplastic. If the LCP is used as a core, it may have a cross section (through at least most of the length) as shown in Figure 1. The core, 1, in spline form, may be formed by melt forming, for example by extrusion or injection molding, much as a drumstick formed completely from LCP would be formed. The core may then be overmolded with another thermoplastic, 2. Useful thermoplastics include polyolefins such as polyethylene, polypropylene and polystyrene, polyesters such as poly(ethylene terephthalate) and poly(butylene terephthalate), polyamides such as nylon-6 and nylon-6,6, and other thermoplastics such as polysulfones, polyethers, polyurethanes. Thermosets may also be used. Useful thermosets include epoxy, urethane and phenolic resins. The LCP core may be overmolded by any usual technique used to overmold thermoplastics or thermosets.

Conversely, a (nonLCP) thermoplastic or thermoset or other material may be used for a core, and an LCP overmolded over that core to form the drumstick. Again any normal method of overmolding may be used. In this process it is often preferred that the LCP have a relatively low melting point so as not to melt or otherwise damage the already existing core. Whichever material is used for the core, the core may be mechanically "locked" to the overmolding by molding into the core shape appropriate angles, overlaps or other discontinuities that cause such mechanical locking.

The drumstick may also be constructed where part of the exposed surface is an LCP or LCP polymer blend "core", and part of the length of the drumstick is overmolded with another polymer, as is shown in Figure 2. In Figure 2, which is a longitudinal cross section of a drum stick, the LCP core, 3, extends beyond the overmolded thermoplastic jacket 4, and this core also is the tip of the drumstick. The LCP core in Figure 2 may have a cross section similar to that shown in Figure 1, until the point where it emerges from under the thermoplastic jacket 4. The LCP and non-LCP polymers in Figure 2 may also be reversed.

As some wooden drumsticks are now made, the striking end of the LCP containing drumstick may be covered by another material such as another thermoplastic, for example a polyamide such as nylon-6 or nylon-6,6. The striking end of the molded drumstick may be configured so that the added tip may slip over that end and be locked onto the end by mechanical means (so-called snap fit). The drumstick may have fastened to it at its end felt or other material which is the surface that actually strikes the drum, as is typical with tympani mallets (sticks).

The LCP drumstick may also be hollow to some extent (through part of all or the length, especially the hand held section) to adjust the weight of the drumstick, adjust the acoustical response, and/or reduce the amount of relatively expensive LCP used. Alternatively for the same reasons the LCP drumstick may be partially or fully foamed to form a rigid foam. Since LCPs maintain their rigidity in foams, the stick's stiffness is not greatly compromised.

Unlike turned drumsticks, such as most wooden drumsticks and oriented polymer drumsticks, the cross section of molded LCP drumsticks need not be circular, and contoured and/or curved drumsticks, which may be easier or less tiring to grip, may be readily formed. Such drumsticks may be ergonomically superior to the classical straight drumstick, and/or the cross section may be varied to change the balance of the drumstick. For a drumstick, such as shown in Figure 2, the outer layer may also be a thermoplastic or thermoset elastomer, preferably a thermoplastic elastomer. The use of an elastomeric outer layer may allow the drumstick to be used with less fatigue by the percussionist, and/or change the acoustical properties of the drumstick. A useful thermoplastic elastomer is a block copolymer containing polyester segments and polyether segments, such as is available under the tradename Hytrel® from the DuPont Co., Wilmington, DE, U.S.A. LCP containing drumsticks are durable, and their acoustical properties may sometimes be adjusted.

Claims

A drumstick, comprising one or more thermotropic liquid crystalline polymer(s).
The drumstick, as recited in Claim 1, where, in said drumstick, the only polymer is said thermotropic liquid crystalline polymer or a polymer blend containing said thermotropic liquid crystalline polymer.
The drumstick, as recited in Claim 2, where, in said drumstick, the only polymer is said thermotropic liquid crystalline polymer.
The drumstick, as recited in Claim 1, wherein said thermotropic liquid crystalline polymer forms a core overmolded with a second polymer.
The drumstick, as recited in Claim 4, wherein said second polymer is a thermoplastic polymer..
The drumstick, as recited in Claim 4 wherein said second polymer is a thermoset polymer.
The drumstick as recited in Claim 1 wherein said thermotropic liquid crystalline polymer is overmolded over an isotropic polymer core.
The drumstick, as recited in Claim 7, wherein said core is a thermoplastic.
The drumstick, as recited in Claim 1, wherein said drumstick is contoured and/or curved, or has a varying cross section.
The drumstick as recited in Claim 1 comprising a blend of one or more liquid crystalline polymers with one or more other thermoplastic polymers.
The drumstick as recited in Claim 10 wherein said liquid crystalline polymer is in a continuous phase.
The drumstick, as recited in claim 1, wherein said drumstick is at least partially hollow, and/or at least part of said liquid crystalline polymer is foamed.