WO2016008922A1

WO2016008922A1 - Roller for a rice husker

Info

Publication number: WO2016008922A1
Application number: PCT/EP2015/066167
Authority: WO
Inventors: Yatin Shriniwas NANDEDKAR; Arun Anantrao KULKARNI
Original assignee: Dsm Ip Assets B.V.
Priority date: 2014-07-16
Filing date: 2015-07-15
Publication date: 2016-01-21

Abstract

A roller for a rice husker, the roller comprising a polymeric surface layer,which surface layer is of a polymer composition comprising a copolyester elastomer.

Description

ROLLER FOR A RICE HUSKER.

The invention relates to a roller for a rice husker and a rice husker comprising the roller. A rice husker is an agricultural machine, used to automate the process of removing the outer husks, also called the chaff, of grains of rice. Throughout history, there have been numerous techniques for the husking of rice. Traditionally, it would be pounded using some form of mortar and pestle. An early simple machine to do this is a rice pounder. The output of such a machine however was limited and it was not simple to operate. Later more efficient machinery was developed to husk and polish rice. These rice huskers are most widely developed and used throughout Asia, North America and South America. The earlier huskers used steel rollers to remove the husk from the rice to obtain the brown rice and often to further mill or polish the grain to remove the bran layer to obtain the white rice.

Rollers comprising an outer rubber surface layer may be used to increase husking efficiency by reducing the amount of broken grains and by reducing the amount of un-husked rice grains. However these so-called rubber rollers tend to require frequent replacement, due to abrasion of the rubber surface layer during the husking process, which is a significant drawback.

Object of the invention is to provide a roller for a rice husker, the roller comprising an outer polymeric surface layer, which roller does not show this

disadvantage. Surprisingly this object is obtained if the surface layer consists of a polymer composition comprising a copolyester elastomer.

A further advantage is that the weight of the roller is reduced, because of the reduction of the thickness of the surface layer.

Yet a further advantage is the increase in efficiency in the milling process by improving the husking efficiency in terms of reduction of the rice in the chaff + rice mix and reduction of the fraction of broken rice.

Copolyester elastomers are thermoplastic polymers with elastomeric properties comprising hard blocks consisting of polester segments, and soft blocks consisting of segments of another polymer. Such polymers are also known as block- copolymers. The polyester segments in the hard blocks of the copolyester elastomers are generally composed of repeating units derived from at least one alkylene diol and at least one aromatic or cycloaliphatic dicarboxylic acid.

The hard blocks typically consist of a polyester having a melting temperature or glass temperature, where applicable, well above room temperature, and may be as high as 300 °C or even higher. Preferably the melting temperature or glass temperature is at least 150 °C, more preferably at least 170 °C or even at least 190 °C. Still more preferably the melting temperature or glass temperature of the hard blocks is in the range of 200 - 280 °C, or even 220 - 250 °C. The soft blocks typically consist of segments of an amorphous polymer having a glass transition temperature well below room temperature and which temperature may be as low as -70 °C or even lower. Preferably the glass temperature of the amorphous polymer is at most 0 °C, more preferably at most -10 °C or even at most -20 °C. Still more preferably the glass temperature of the soft blocks is in the range of -20 - -60 °C, or even -30 - -50 °C.

Suitably, the copolyester elastomer is a copolyesterester elastomer, a copolycarbonateester elastomer, and /or a copolyetherester elastomer; i.e. a copolyester block copolymer with soft blocks consisting of segments of polyesters, polycarbonate or, respectively, polyether. Suitable copolyesterester elastomers are described, for example, in EP-01021 15-B1. Suitable copolycarbonateester elastomers are described, for example, in EP-0846712-B1. Copolyester elastomers are available, for example, under the trade name Arnitel, from DSM Engineering Plastics B.V. The Netherlands.

Preferably, the copolyester elastomer is a copolyetherester elastomer.

Copolyetherester elastomers have soft segments derived from at least one polyalkylene oxide glycol. Copolyetherester elastomers and the preparation and properties thereof are in the art and for example described in detail in

Thermoplastic Elastomers, 2nd Ed., Chapter 8, Carl Hanser Verlag (1996) ISBN 1 - 56990-205-4, Handbook of Thermoplastics, Ed. O. Otabisi, Chapter 17, Marcel Dekker Inc., New York 1997, ISBN 0-8247-9797-3, and the Encyclopedia of Polymer Science and Engineering, Vol. 12, pp. 75-1 17 (1988), John Wiley and Sons, and the references mentioned therein.

The aromatic dicarboxylic acid in the hard blocks of the

polyetherester elastomer suitably is selected from the group consisting of terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid and 4,4- diphenyldicarboxylic acid, and mixtures thereof. Preferably, the aromatic dicarboxylic acid comprises terephthalic acid, more preferably consists for at least 50 mole %, still more preferably at least 90 mole %, or even fully consists of terephthalic acid, relative to the total molar amount of dicarboxylic acid.

The alkylene diol in the hard blocks of the polyetherester elastomer suitably is selected from the group consisting of ethylene glycol, propylene glycol, butylene glycol, 1 ,2-hexane diol, 1 ,6-hexamethylene diol, 1 ,4-butane diol, benzene dimethanol, cyclohexane diol, cyclohexane dimethanol, and mixtures thereof. Preferably, the alkylene diol comprises ethylene glycol and/or 1 ,4 butane diol, more preferably consists for at least 50 mole %, still more preferably at least 90 mole %, or even fully consists of ethylene glycol and/or 1 ,4 butane diol, relative to the total molar amount of alkylene diol.

The hard blocks of the polyetherester elastomer most preferably comprise or even consist of polybutylene terephthalate segments.

Suitably, the polyalkylene oxide glycol is a homopolymer or copolymer on the basis of oxiranes, oxetanes and/or oxolanes. Examples of suitable oxiranes, where upon the polyalkylene oxide glycol may be based, are ethylene oxide and propylene oxide. The corresponding polyalkylene oxide glycol homopolymers are known by the names polyethylene glycol, polyethylene oxide, or polyethylene oxide glycol (also abbreviated as PEG or PEO), and polypropylene glycol, polypropylene oxide or polypropylene oxide glycol (also abbreviated as PPG or PPO), respectively. An example of a suitable oxetane, where upon the polyalkylene oxide glycol may be based, is 1 ,3-propanediol. The corresponding polyalkylene oxide glycol homopolymer is known by the name of poly(trimethylene)glycol. An example of a suitable oxolane, where upon the polyalkylene oxide glycol may be based, is tetrahydrofuran. The corresponding polyalkylene oxide glycol homopolymer is known by the name of poly(tretramethylene)glycol (PTMG) or polytetrahydrofuran (PTHF). The polyalkylene oxide glycol copolymer can be random copolymers, block copolymers or mixed structures thereof. Suitable copolymers are, for example, ethylene oxide /

polypropylene oxide block-copolymers, (or EO/PO block copolymer), in particular ethylene-oxide-terminated polypropylene oxide glycol.

The polyalkylene oxide can also be based on the etherification product of alkylene diols or mixtures of alkylene diols or low molecular weight poly alkylene oxide glycol or mixtures of the aforementioned glycols.

Preferably, the polyalkylene oxide glycol used in the flame retardant elastomeric composition in the insulated wire according to the invention is selected from the group consisting of polypropylene oxide glycol homopolymers (PPG), ethylene oxide / polypropylene oxide block-copolymers (EO/PO block copolymer) and poly(tretramethylene)glycol (PTMG), and mixtures thereof.

The polymer composition of the surface layer preferably comprises at least 50 wt.% of the copolyester elastomer, more preferably at least 70 wt.%, even more preferably at least 90 wt.%. The rolls comprising a rubber surface layer according to the state of the art comprise a metal core, suitably an aluminum core. Good results are obtained if the roll according to the invention comprises a core consisting of a polymer

composition comprising one or more polyamides. Preferably the polymer composition of the core comprises at least 50 wt % of one or more polyamide, more preferably 75 wt.% even more preferably 90 wt.%.

Suitable polyamides include aliphatic polyamides such as PA6, PA66, PA46, PA410, PA610, PA612, PA1 1 , PA12, PA412 as well as blends thereof, but also semi-aromatic polyamides. Suitable semi-aromatic polyamides include terephthalic acid based polyamides like PA6T, PA9T, PA4T and PA6T6I, as well as PAMXD6 and PAMXDT, and copolyamides thereof, as well as blends thereof, as well as blends of aliphatic and semi-aromatic polyamides.

Preferably the polyamide is chosen from the group of PA6, PA66 or blends thereof, as this has the advantage that these polyamides are readily available. Ref: Nylon Plastics Handbook, Melvin I. Kohan, 1995, page 5

The rolls according to the invention may be produced by

overmoulding of the surface layer in the mold of an injection molding machine, either horizontally or vertically. The surface layer of the roller may also be produced by a casting process.

The thickness of the surface roller may vary between 6 and 35 mm, preferably between 8 to 25 mm, more preferably between 10 and 20 mm. The thickness of the surface layer may depend on the size of the husking machine.

The invention also relates to a rice husker comprising one or more rolls according to the invention.

The adhesion between the surface layer and the core may be achieved by mechanical anchoring, surface treatment of the core and through application of a bonding agent to the core, before application of the surface layer.

The invention also relates to a rice husker comprising at least one roller according to the invention. Good results are obtained if the rice husker according to the invention comprises a pair of rollers, one roller according to the invention having an outer surface layer consisting of a polymer composition comprising a thermoplastic copolyester elastomer as described above the other roller being produced of, or having an outer surface layer of a polymer composition comprising a polyamide, preferably PA46. With this rice husker a very efficient rice husking process is obtained.

Claims

1 . A roller for a rice husker, the roller comprising an outer polymeric surface layer, characterized in that the surface layer consists of a polymer composition comprising a copolyester elastomer.

2. A roller according to claim 1 , wherein the polymer composition of the surface layer comprises at least 90 wt. % of the copolyester elastomer.

3. A roller according to claim 1 or 2, wherein the copolyester elastomer is a

copolyetherester elastomer.

4. A roller according any one of the preceding claims, wherein the core is of a polymer composition comprising one or more polyamides.

5. A roller according to claim 4, wherein the polymer composition of the core comprises at least 90 wt.% of one or more polyamides.

6. A roller according to any one of the preceding claims, wherein the polyamide is chosen from the group of PA6, PA66.

7. A roller according to any one of the preceding claims, wherein the outer

surface layer has a thickness between 8 to 25 mm.

8. Rice husker comprising a roller according to any one of the preceding claims.

9. Rice husker according to claim 8, wherein the rice husker comprises a pair of rollers, one roller according to any one of claims 1 - 8, the other roller consisting of, or having an outer surface layer of a polymer composition comprising a polyamide.

10. Rice husker according to claim 9, wherein the polyamide is PA46.