The invention relates to a ball as set forth in the in- dependent claim directed thereto .

Plastic, essentially a mixture of a polymer and addi- tives, is presently used to produce a wide range of ob- j ects in large quantities thanks to their easy moldabil- ity, efficient manufacturing and technical properties .

Bioplastics are plastics that are partly or entirely made of renewable natural materials, or that decompose under certain conditions . Bioplastics can be further divided into bio-based and biodegradable plastics . Bio-based plastics are produced from renewable materials such as cellulose, lignin, chitin, wool or starch . However, bio- based plastics are not necessarily biodegradable, and non-biodegradable plastics can also be produced from these materials . Biodegradable plastics are those that, depending on the material , decompose in high temperature industrial composting system or lower temperature home composting system into water and carbon dioxide . Biode- gradable plastics can be produced from bio-based materi- als , but also from fossil raw materials .

Plastic balls made of both biodegradable and non-biode- gradable plastic are currently used as ammunition in air- soft guns . The proj ectiles are spherical plastic balls of varying weights , typically 5 . 9-6. 1 mm in diameter and 0 . 12-0. 48 g in weight . The most common type of plastic used in ammunition is non-biodegradable acrylonitrile bu- tadiene styrene (ABS ) . However, for outdoor games , balls made of ABS polymer are quite often forbidden, as it is impractical to collect the balls from the ground . ABS polymer does not biode- grade , causing plastic waste accumulation in the playing area and damage to the environment . For this reason, bi- odegradable plastic balls are used for outdoor airsoft games . Currently, biodegradable balls are made from ma- terials such as polylactide (PLA, (C 3H 4O 2 ) n) > which is typically made from renewable, bio-based materials such as starches . However, in practice PLA has turned out to be decomposing slowly in soil or home composting system and thus requires industrial composting where the tem- perature is raised above 60 °C to enhance degradation .

In some cases, biodegradable balls are made by arranging an organic core inside a polymer shell in order to promote faster biodegradation . However, the manufacturing process for such balls is more complex and expensive compared to inj ection molded plastic balls , and their shelf life is reduced due to the organic core .

Plastic balls can be manufactured by conventional methods suitable for the production of plastic parts , such as inj ection molding . In inj ection molding, the balls can be molded directly into a sphere or hemisphere shape in a mold, wherein the latter case the two hemispherical pieces are j oined together after molding . After molding, the balls must be grinded and polished to their final shape . The purpose of grinding and polishing is to remove flashes and other molding defects from the surface of the ball, to finish the surface to the required surface rough- ness and to ensure the sphericity of the ball . Balls made of plastic are also used as balls for slotted sealed ball bearings or valves where cleanliness and moisture resistance are required, e . g . , in the food in- dustry, cosmetics or pharmaceutical packaging or in un- derwater bearings or similar applications where conven- tional metal bearings corrode and/or pose a risk of con- tamination .

The obj ective of a ball according to the present inven- tion, made from a biodegradable PBS polymer and addi- tives, is to provide a decisive remedy for the foregoing problems and to thereby elevate substantially the exist- ing prior art . In order to attain this obj ective, the ball according to the invention is principally charac- terized by what is presented in the characterizing part of an independent claim directed thereto . The invention enables a ball made of biodegradable material , which is self-degradable under natural conditions , to be used for a number of purposes .

Polybutylene succinate ( PBS , (CgHiaCh J n) is a biodegradable polymer classified as a thermoplastic, which can be pro- duced from bio-based materials, but also from fossil raw materials . Traditionally, PBS polymer is produced from chemicals derived from petrochemical products of crude oil, such as amber acid and 1 , 4-butanediol as the main feedstocks . However, both of these feedstocks can also be produced from a bio-based materials . Bio-based PBS is made from renewable raw materials such as sugar cane , cassava or maize and its manufacturing is patented by Mitsubishi Chemical Corporation and marketed under the brand name BioPBS™ . PBS polymer degrades at a significantly lower temperature compared to PLA plastic, breaking down into biomass , water and carbon dioxide at temperatures as low as 30 °C, making it suitable for com- posting in home composting systems or open-air landfills . It can be disposed of with other biowaste .

PBS has similar properties to polypropylene (PP ) or pol- yethylene terephthalate ( PET ) . These properties allow PBS to be processed for applications in the plastics indus- tries and allow the usage of existing manufacturing pro- cesses, such as inj ection molding, and various grinding and polishing processes , to be used in the manufacturing of products made from it .

The polymeric material of the ball according to the in- vention is thus a polybutylene succinate, to which vari- ous additives are added during the production process to modify and improve the physical properties , thus obtain- ing a biodegradable plastic ball with properties suitable for the particular application, such as for example for outdoor airsoft games as a gun ammunition .

The dependent claims directed to a ball of the invention present other preferred embodiments therefor .

In the subsequent specification, the invention will be described in detail .

The invention relates to a ball comprising a biodegrada- ble polymer and one or more additives , such as an anti- -tatic agent, a density increasing agent , a strength/hardness modifier and/or the like added to the polymer mass during the compounding step . The ball is manufactured by a process suitable for production of pol- ymers , such as inj ection molding, into a substantially spherical shape and then grinded and/or polished to its final shape by double-sided lapping, barrel tumbling and/or the like . The biodegradable polymer used in the ball is polybutylene succinate ( PBS ) .

In particular, fillers can be used to modify the density of a plastic composition, wherein the fillers are typi- cally powdered metal oxides ; such as alumina, magnesia or the like ; pure metal powders such as sodium; alloy metal powders ; salts of metals , semimetals and alkali metals ; such as silicon dioxide and/or the like ; minerals, min- eral and ionic compounds ; such as barium sulphate, cal- cium hydroxide or lime, cerium oxide, magnesium hydrox- -de, calcium carbonate, dolomite, kaolin, aluminum hy- droxide , wollastonite and/or kieselguhr; glass , carbon, aramid or natural fibers or filaments and/or the like .

In a preferred embodiment of the invention, the density of the abovementioned fillers is at least 1 .27 g/cm ³ to increase the overall density of the plastic composition . In a preferred advantageous embodiment of the invention, the amount of biodegradable polybutylene succinate, act- ing as a binder polymer in the composition, is between 22 and 60 wt% , more preferably between 34 and 60 wt% , to achieve the required hardness/strength properties .

The balls can be manufactured by any method suitable for the production of plastics , such as inj ection molding, wherein a granulate made from plastic mass is fed into the inj ection screw of a molding machine, melted and in- j ected into a mold . After cooling, the mold is opened and the molded plastic part is removed from the mold .

When casting small-sized balls , the mold contains several identical pieces at a time . The individual balls are separated either by using a molding method in which the balls are removed from the molding runners when the mold opens , or alternatively by cutting the balls out of the supporting structure formed by the molding runners after molding . After molding, the balls are ground, which can be achieved by any method suitable for grinding spherical parts , such as for example double-sided lapping, barrel tumbling and/or similar, whereby the molding defects and possible flashes are removed and the sphericity of the ball is improved . After grinding, the balls are polished to the final surface finish, e . g . , with the abovemen- tioned processes and with a suitable polishing agent, and then further screened for non-standard balls .

In a preferred embodiment of the invention, the ball to be manufactured comprises at least one antistatic agent, i . e . , a static charge eliminator . In a still further pre- ferred embodiment, the additive used herein is first of all a permanent static charge eliminator, such as an electrically conductive polymer electrolyte formed by a polymer and salts and/or an electrically conductive car- bon, graphene and/or the like, and/or a hygroscopic hu- mectant absorbing moisture from the ambient air, such as a moisture absorbing salt, to provide surface conductiv- ity .

In a still further preferred embodiment of the invention, the balls are coated with a static charge elimination agent , such as a hygroscopic humectant that absorbs mois- ture from the ambient air, to provide surface conductiv- ity .

In a still further preferred embodiment of the invention, the balls are intended to be used in particular as ammunition for an airsoft gun, or alternatively, for ex- ample , in a bearing application as a ball for a slotted sealed ball bearing or the like, wherein the diameter of the ball is , for example, between 0.25 and 51 mm in di- ameter in accordance with the standard dimensions of a steel bearing ball . The balls according to the invention can also be used, for example, in valves with signifi- cantly larger diameters .

It is obvious that the invention is not limited to the embodiments presented or described above, but can be mod- ified within the basic context of the invention, depend- ing on the circumstances , by using the most suitable mix- ture of PBS polymer, other polymers and/or additives for the manufacture of the ball . The properties of the PBS polymer can be modified, for example, by nanocomposites such as fibers and metal or metal oxide nanoparticles , resulting in increased strength and/or biodegradability of the polymer . Furthermore, it is possible to add mate- rials to the ball, e . g . , a material that causes the ball to glow in th-e dark after an exposure in a gun ' s lighter tracer unit, allowing the ball ' s traj ectory to be as- sessed in low light conditions when used as an airsoft ammunition . It is also possible to dye the balls for better detectability, or coat them with a dye to detect a hit . The size, density and weight of the ball may vary depending on the intended use, making it possible to use biodegradable balls as shotgun pellets , different air weapons or in games , for example, where the size of the ball used may vary significantly . Depending on the ap- plication, the ball can be further coated with metal to modify the surface properties or to improve durability, e . g . , in valve applications .