WO2016105217A1

WO2016105217A1 - Biodegradable seedling pots and method of their manufacture

Info

Publication number: WO2016105217A1
Application number: PCT/PL2014/000153
Authority: WO
Inventors: Małgorzata IZYDORCZYK; Konrad SULAK; Tomasz MIK; Danuta CIECHAŃSKA; Izabella KRUCIŃSKA; Michał PUCHALSKI; Piotr SIWEK
Original assignee: Instytut Biopolimerów i Włókien Chemicznych; Politechnika Łódzka
Priority date: 2014-12-22
Filing date: 2014-12-22
Publication date: 2016-06-30

Abstract

The invention relates biodegradable pots for plant seedlings formed from a nonwoven, which is made up of a blend of poly(butylene succinate) and potassium sulfate in the weight proportion of from 100:1 to 20: 1, with surface density of 30 - 200g/m² and tenacity measured as breaking force in the along/across directions of from 10N / 9N to 30N / 35N. The invention concerns the manufacture of biodegradable pots, too.

Description

Biodegradable seedling pots and method of their manufacture

The invention concerns biodegradable seedling pots and a manufacturing method of the seedling pots.

Commonly known are pots made of ceramics, metals, wood and crude oil derivatives like for example vinyl chloride or polypropylene. Resin pots are mainly prepared by injection moulding which allows the preparation of hard products with rather thick walls. Openings are provided in the bottom of the pots to allow water drainage and penetration of roots. Known are also thin pots prepared from film by pressing. Resistance to biodegradation is the main defect of that sort of pots implying the need of their post-use utilization.

Biodegradable pots are very useful in agriculture and wood nursery. They are applied in greenhouses for seedlings that after the initial growth are replanted to the soil. Transplantation to the soil without the need to remove the pots is a big advantage of the biodegradable products which are put to decomposition in the soil.

Known are also pots made of natural raw materials like cattle dung, rice husks, fibre of Miscanthus grass, coconut fibers, paper with addition of dried algae, and natural plant resins wit addition of turf.

Known from the Polish Patent application PL 392164 are pots made by extrusion moulding or by blow moulding from a polypropylene-based material with content of active substances dissolved in the basic material which initiate the degradation in the soil.

Known from the European Patent EP 0805181 are biodegradable resins designed for the manufacture of containers for cuttings and young plants made by extrusion moulding from pellets of biodegradable aliphatic polyesters and pulverized cellulose blended in the proportion of from 20 : 80 to 80 : 20. Degradation rate and progress of such resins is being controlled. Known from the European Patent EP 0881254 is a biodegradable material made up of pulverized paper and a biodegradable aliphatic polyester resin designed for, among others, plant seedling pots. Degradation time is adjusted to the kind of plants. The material was found to entirely degrade after 90 days.

Known from the Japanese Patent JP 11269753 are nursery pots characterized by a controlled degradation rate that are made from a blend of poly(butylene succinate) and poly(lactic acid) and carbon black

Biodegradable pots for plant seedlings according to the present invention are formed from a nonwoven made of a blend of poly( butylene succinate) and potassium sulfate in the weight proportion of from 100: 1 to 20: 1 with surface density of 30 - 200g m² and tenacity measured as along/across breaking force amounting to from 10N / 9N to 30N / 35N.

The method of manufacturing the seedling pots is featured by that the molten poly( butylene succinate) containing no more than 5 %wt. of potassium sulfate is at 190 - 250°C extruded through a multi-hole spinneret with a throughput of 0,1 - 3,0 g/min/hole. The spun fibers are drawn in air at 10- 25°C and at pressure difference of 900 to 2500 Pa in the forming shaft to form a fleece which is thence integrated into a nonwoven under the pressure of 0, 1 - 1,0 MPa and at temperature of 20 - 100°C. The biodegradable pots are formed from the obtained nonwoven by known methods like thermal or thermoforming method.

The pots according to the invention are distinguished by a short degradation time in soil of 5- 7 weeks in average. The time permits a free growth of the roots and the whole plant. Prior to the in-soil planting, the pots maintain their shape and structure for 3-4 weeks; that is the time necessary for the growth of seedling on trays in the greenhouse. Following examples illustrate the subject of the invention: Example 1.

A blend was prepared of fibre-grade poly(butylene succinate) - trade name Bionolle 1020MD with a 20% content of potassium sulfate. Prior to the blending, Bionolle was dried up to moisture content below 0,005 %; potassium sulfate was milled in a planetary mill and then screened through a 20 μηι mesh. The blend was fed to a twin-screw extruder with temperature from 177 to 200°C in the consecutive zones. A polymer string was extruded, quenched in water and cut into pellets. 2kg of the pellets were mixed with 6 kg of dried up Bionolle 1020MD (moisture content below 50 ppm). A nonwoven was formed from the molten mixture which was extruded through a single- screw extruder at temperature of 120 - 200°C in the consecutive zones. The molten, potassium sulfate-containing polymer was pressed by means of a metering pump through a 464-capillary spinneret with a throughput of 0,28 g/min/capillary. Diameter and length of the capillary were 0,4 and 2 mm respectively. The formed fibres were directed to a lead channel where they were stretched by air at 18°C streaming from a pneumatic device. Pressure drop of the air in the channel was 1200 Pa. The drawn fibres then entered a forming channel where they were spread on a travelling band under which the pressure was maintained by ca. 24 Pa lower than the atmospheric one. The fleece was first combined by a squeezing roller at 45°C, and then thermally combined on a calender with rollers heated to 80°C at applied pressure of 0,5 MPa. The take-up speed of the nonwoven was 4.2 m/min.

A nonwoven was obtained with content of 4,91%wt. of potassium sulfate. The nonwoven was characterized by a thickness of 0,49mm, surface density of 67,2g/m² and breaking force in the along/across directions amounting to 18,0N / 16, IN. Pots were formed from the nonwoven with the use of a stationary thermal heat sealing machine with an 8 - step temperature control. The pots were used for the planting of cucumber seedlings Barvina Fl according to a testing procedure in a greenhouse. The seedlings planted in pots made of a potassium sulfate-containing nonwoven revealed shoots longer by 20cm in average longer than those planted in pots of nonwoven without potassium sulfate. Kept for 6 weeks in soil, the pots showed a mass loss of 33,7%. Example 2

0,5kg of the pellets prepared as in Example 1 were mixed with 9,5 kg of dried Bionolle 1020 MD. Next a nonwoven was formed from the melt of the mixture. The potassium sulfate-containing polymer was passing through a single-screw extruder with temperature in the consecutive zones in the range of 160 - 250°C, and was extruded through a spinneret as in Example 1. The fibres were directed from the spinneret to a lead channel where they were stretched by air at 14,4°C streaming from a pneumatic device. Pressure drop of the air in the lead channel was lOOOPa. The drawn fibres were directed to the forming channel where they were spread on a travelling band under which the pressure was maintained by ca. 240 Pa lower than the atmospheric one. The fleece was first combined by a squeezing roller at 60°C, and then thermally combined on a calender with rollers heated to 65°C at applied pressure of 0,5 MPa. The take-up speed of the nonwoven was 5,8 m/min.

A nonwoven was obtained with content of 0,95 %wt. of potassium sulfate. The nonwoven was characterized by a thickness of 0,3 mm, surface density of 52,6 g/m² and breaking force in the along/across directions amounting to 16, ON /28,1N.

Pots were formed from the nonwoven by thermoforming method. The pots were used for the planting of cucumber seedlings Barvina Fl according to a testing procedure in a greenhouse. The seedlings planted in pots made of a potassium sulfate-containing nonwoven revealed shoots longer by 9.6 cm in average than those planted in pots of nonwoven without potassium sulfate. Kept for 6 weeks in soil, the pots showed a mass loss of 40.7%

Claims

1. Biodegradable pots for plant seedlings characterized by that they are formed from a nonwoven which constitutes a blend of poly(butylene succinate) and potassium sulfate in the weight proportion of from 100 .1 to 20: 1 with surface density of 30 - 200g/m² and tenacity measured as braking force in the along/across directions amounting to from 10N / 9N to 30N / 35N.

2. Method of manufacturing the biodegradable pots for plant seedlings characterized by that the molten poly(butylene succinate) with a content of no more than 5% wt. of potassium sulfate is extruded at temperature of 190 - 250°C through a multi-hole spinneret with a throughput of 0,1 - 3,0 g/min/hole, next from the formed fibers drawn by air at temperature of 10 -25°C, and at pressure difference in the forming channel of from 900 to 2500 Pa, a nonwoven is formed, which is then combined under pressure of 0, 1 - 1,0 MPa and temperature of 20 - 100°C to obtain a nonwoven from which the biodegradable pots are formed by known methods.