CONVEYOR BELT

Abstract

This invention relates to a conveyor belt comprising a composition comprising a) a (co)polyester A comprising hard segments comprising a polyester and having a melting temperature T.sub.mA of between 200° C. and 240° C. as measured according to ISO 11357-1/-3 (10° C./min), wherein the (co)polyester A is present in an amount of between 1 and 60 wt % with respect to the total weight of the composition; and b) a copolyester B comprising hard segments comprising a polyester wherein the (co)polyester B has a melting temperature T.sub.mB of between 100° C. and 180° C., as measured according to ISO 11357-1/-3 (10° C./min), wherein the copolyester B is present in an amount of between 40 and 99 wt % with respect to the total weight of the composition. The invention also relates to a process for preparing the conveyor belt.

Claims

1. Conveyor belt comprising a composition comprising a) a (co)polyester A comprising hard segments comprising a polyester and having a melting temperature T.sub.mA of between 200° C. and 240° C. as measured according to ISO 11357-1/-3 (10° C./min), wherein the (co)polyester A is present in an amount of between 1 and 60 wt % with respect to the total weight of the composition; and b) a copolyester B comprising hard segments comprising a polyester wherein the (co)polyester B has a melting temperature T.sub.mB of between 100° C. and 180° C., as measured according to ISO 11357-1/-3 (10° C./min), wherein the copolyester B is present in an amount of between 40 and 99 wt % with respect to the total weight of the composition.

2. The conveyor belt according to claim 1, wherein the composition has a bimodal melting behavior exhibiting at least two peaks, one peak P1 between 200° C. and 240° C. and another peak P2 between 100° C. and 180° C.

3. The conveyor belt according to claim 1, wherein T.sub.mA-T.sub.mB is at least 40° C., preferably at least 50° C. and most preferred at least 60° C. and/or P1-P2 is at least 40° C., preferably at least 50° C. and most preferred at least 60° C.

4. The conveyor belt according to claim 1, wherein (co)polyester A and/or copolyester B comprise hard segments comprising polybutylene terephthalate (PBT).

5. The conveyor belt according to claim 1, wherein the copolyester B comprises soft segments chosen from aliphatic polyesters, aliphatic polyethers, dimer fatty acids and dimer fatty diols and combinations thereof, preferably an aliphatic polyether being polytetramethylene oxide (PTMO).

6. The conveyor belt according to claim 1, wherein copolyester B further comprises PBI segments in an amount of between 5 and 50 wt % with respect to the total amount of copolyester B.

7. The conveyor belt according to claim 1, wherein the composition further comprises nucleating agent, glass fibers, stabilizers, colorants, and combinations thereof.

8. The conveyor belt according to claim 1, wherein the (co)polyester A is PBT.

9. The conveyor belt according to claim 1, wherein the conveyor belt is an extruded conveyor belt.

10. Process for preparing a conveyor belt according to claim 1, comprising at least the following steps: a) Providing a composition comprising a (co)polyester A comprising hard segments comprising a polyester and having a melting temperature T.sub.mA of between 200° C. and 240° C. as measured according to ISO 11357-1/-3 (10° C./min); and a copolyester B hard segments comprising a polyester wherein the (co)polyester B has a melting temperature T.sub.mB of between 100° C. and 180° C., as measured according to ISO 11357-1/-3 (10° C./min); and wherein the (co)polyester A is present in an amount of between 1 and 60 wt % with respect to the total weight of the composition and the copolyester B is present in an amount of between 40 and 99 wt % with respect to the total weight of the composition; b) Bringing the composition to a temperature of between 230° C. and 290° C. to form a melt; c) Extruding the melt through a die; d) Cooling the extruded melt to form a conveyor belt; e) Optionally welding parts onto the conveyor belt.

11. Process according to claim 10, wherein T.sub.mA-T.sub.mB is at least 40° C., preferably at least 50° C. and most preferred at least 60° C.

12. Process according to claim 10, wherein copolyester B further comprises soft segments chosen from aliphatic polyesters, aliphatic polyethers, aliphatic polycarbonates, dimer fatty acids and dimer fatty diols and combinations thereof.

13. Process according to claim 10, wherein the composition in step a) is provided as a blend by mixing the (co)polyester A and the copolyester B as a dry-blend.

14. Process according to claim 10, wherein a drying step is applied to the (co)polyester A and/or the copolyester B before bringing the (co)polyester A and the copolyester B to a temperature of between 230° C. and 290° C. to form a melt.

15. Process for transporting food, comprising at least the following steps: Providing food on a conveyor belt; Moving the conveyor belt with the food in a desired direction; wherein the conveyor belt is a belt according to claim 1.

Description

EXAMPLES

Materials Used

Polyester A-I; PBT

[0058] Melt volume-flow rate (T=250° C., weight=2.16 kg): 22 cm.sup.3/10 min according to ISO1133
Melting temperature (10° C./min): 225° C. according to ISO11357-1/-3
Water absorption: 0.45 wt % (ISO 62)
Humidity absorption: 0.18 wt % (ISO 62)
Density: 1300 kg/m.sup.3 according to ISO1183
RSV (m-cresol, 1 g/100 mL): 2.1 (ISO 1628-5:1998 and ISO307)

(Co)polyester A-II

[0059] Copolyetherester based on PBT as hard segment and PTMO as soft segment, containing, 65 m/m % hard segment and 35 m/m % soft segment.
Melt volume-flow rate (T=230° C., weight=2.16 kg): 9 cm.sup.3/10 min according to ISO1133
Melting temperature (10° C./min): 207° C. according to ISO11357-1/-3
Water absorption: 0.65 wt % (ISO 62)
Humidity absorption: 0.20 wt % (ISO 62)
Density: 1200 kg/m.sup.3 (ISO1183)
Shore D hardness (3s): 52 (ISO 868)
RSV (m-cresol, 1 g/100 mL): 3.2 (ISO 1628-5:1998 and ISO307)

(Co)polyester A-III

[0060] Copolyetherester based on PBT as hard segment and PTMO as soft segment, containing, 75 m/m % hard segment and 25 m/m % soft segment.
Melt volume-flow rate (T=230° C., weight=2.16 kg): 4 cm.sup.3/10 min according to ISO1133
Melting temperature (10° C./min): 212° C. according to ISO11357-1/-3
Water absorption: 0.6 wt % (ISO 62)
Humidity absorption: 0.20 wt % (ISO 62)
Density: 1240 kg/m.sup.3 according to ISO1183
Shore D hardness (3 s): 60 (ISO 868)
RSV (m-cresol, 1 g/100 mL): 3.4 (ISO 1628-5:1998 and ISO307)

(Co)polyester A-IV

[0061] Copolyetherester based on PBT as hard segment and PTMO as soft segment, containing, 90 m/m % hard segment and 10 m/m % soft segment.
Melt volume-flow rate (T=230° C., weight=2.16 kg): 18 cm.sup.3/10 min according to ISO1133
Melting temperature (10° C./min): 221° C. according to ISO11357-1/-3
Water absorption: 0.6% (ISO 62)
Humidity absorption: 0.15% (ISO 62)
Density: 1290 kg/m.sup.3 according to ISO1183
Shore D hardness (3 s): 70 (ISO 868)
RSV (m-cresol, 1 g/100 mL): 2.3 (ISO 1628-5:1998 and ISO307)

Copolyester B-I

[0062] Copolyester based on both PBT and PBI as hard segment and PTMO as soft segment, containing, 65 m/m % hard segments and 35 m/m % soft segment.
Melt volume-flow rate (T=230° C., weight=2.16 kg): 25 cm.sup.3/10 min according to ISO1133
Melting temperature (10° C./min): 165° C. according to ISO11357-1/-3
Water absorption: 0.65 wt % (ISO 62)
Humidity absorption: 0.20 wt % (ISO 62)
Density: 1190 kg/m.sup.3 according to ISO1183
RSV (m-cresol, 1 g/100 mL): 2.8 (ISO 1628-5:1998 and ISO307)

Preparation of Compositions

[0063] Compositions were made with recipes as listed in Table 3 by hand mixing the granules in the given ratio prior to injection molding.

TABLE-US-00003 TABLE 3 Compositions Polyester Copolyester Copolyester Copolyester Copolyester A-I, PBT, A-II, A-III, A-IV, B-I, T.sub.mA − T.sub.mA = 225° C., T.sub.mA = 207° C., T.sub.mA = 212° C., T.sub.mA = 221° C., T.sub.mB = 165° C., T.sub.mB [wt %] [wt %] [wt %] [wt %] [wt %] [° C.] Example 1 30 0 0 0 70 60 Example 2 20 0 0 0 80 60 Example 3 10 0 0 0 90 60 Example 4 0 0 80 0 20 47 Example 5 0 0 0 50 50 56 Comparative 0 50 50 0 0 experiment A Comparative 100 0 0 0 0 N.A. experiment B Comparative 0 0 0 0 100 N.A. experiment C wt % with respect to the total weight of the composition.

Preparation of Test Plaques and 1BA Tensile Bars by Injection Moulding

[0064] Where applicable, ISO 294-1 Standard was used.
Plaques with dimensions 120×120×4.0 mm were molded with pre-dried material.
Material was dried 6 hr/120° C. with vacuum and N2 purge. Moisture content after drying below max. moisture spec. (<500 ppm). Material was processed on an Injection molding machine brand Arburg with clamp force 150 tons and 40 mm screw diameter. Measured melt temperature 247 and 248° C. Measured mold temperature was between 40 and 43° C. Thickness of the produced plaques was measured between 3.97 and 4.0 mm.
Parts are packed dry as molded in seal bags.
Plaques with dimensions 80×80×1 mm were molded with pre-dried material. Material was dried 6 hr/120° C. with vacuum and N2 purge. Moisture content after drying below max. moisture spec. (<500 ppm). Material was processed on an Injection molding machine brand Arburg with clamp force 110 tons and 25 mm screw diameter. Measured melt temperature 246 and 247° C. Measured mold temperature was between 17 and 27° C. Thickness of the produced plaques was measured at 1.02 mm. Parts are packed dry as molded in seal bags.
Tensile bars ISO 527-1BA were molded with pre-dried material. Material was dried 6 hr/120° C. with vacuum and N2 purge. Moisture content after drying below max. moisture spec. (<500 ppm). Material was processed on an Injection molding machine brand Arburg with clamp force 70 tons and 20 mm screw diameter. Measured melt temperature between 229 and 236° C. Measured mold temperature was between 46 and 51° C. Thickness of the produced bars was measured between 2.04 and 2.05 mm. Parts are packed dry as molded in seal bags.

Relative Solution Viscosity

[0065] The relative solution viscosity was determined in a solution of 1.0 gram of material in 100 ml of m-cresol at 25° C. according to ISO 1628-5:1998.

Mechanical Properties

[0066] Tensile bars type 1BA, according to ISO527, were tested on a Zwick//Roell Z010 tensile tester equipped with a 2.5 kN force cell, Zwick contact extensometers type Multisens with a gauge length of 25 mm and Zwick pneumatic clamps type 8297 with a gripping distance of 58 mm. After a preload of 0.5N was applied, the test starts with a test speed of 1 mm/min to determine E-modulus (0.05%-0.25%) followed by a test speed of 500 mm/min until rupture. Strain was measured up to 60% strain with extensometers, followed by traverse displacement until rupture. Tensile Strength (M Pa) was determined as the highest found stress during testing. The tests were carried out in fivefold. The specimens were “Dry As Moulded” during testing, and the tests were conducted at a test temperature of 23° C. “Dry As Moulded” is herein understood that immediately after moulding the specimens were placed in a moisture-proof container and stored at (23±2)° C. for at least 24 h and having a moisture content <0.2% (mass fraction).

Dynamical Mechanical Analysis (DMA)

[0067] From the 150 mm×150 mm×4.0 mm injection molded plaques, DMA in torsion were performed which are generally described in ASTM D5279. The samples for the measurements were sawed to a suitable length (10 mm×55 mm), parallel and perpendicular to the melt flow in injection molding. The dimensions were measured with the calibrated Heidenhain thickness meter. Prior to the measurements, the samples were dried for 4 h at 110° C. at 150 mbar nitrogen pressure. The dynamic mechanical analyses were carried out using a TA ARES test system at a frequency of 1 Hz and over a temperature ranging from −130° C. to 250° C. with a heating rate of 3° C./min. During the measurements, the storage modulus (G′), loss modulus (G″) and tangent delta (tan δ) were determined as a function of temperature.

Weldability

[0068] Welding was performed on the 80 mm×80 mm×1.0 mm injection molded plaques. Two plaques were placed on top of each other. Welding was performed on a 16 KW RF welding machine with a vertical press set-up. An electrode brass 75×10 mm.sup.2 was used. Temperature of the main block was controlled at 200° F. (93.3° C.). Temperature of the contact plate was not controlled but measured typically at 110° F. (43.3° C.). Each RF welding cycle consisted of: 1.0 second pre-heat when pressure is applied; 2.5 seconds during which Amperage is applied; 2.0 seconds cooling cycle. The amperage is controlled by a percentage of the maximum power. 180° peel tests were performed to quantify the maximum peel force of the weld using the procedure as described below. The welded plaques were put into room environment with a temperature range of 23+/−2° C., 50+/−10% RH for 3 days; Plaques with a width of 10 mm were marked with a mark pen and manually cut with scissors; test parameter such as preload*, grip distance (50 mm), test speed (50 mm/min) were put in the software; The thickness and width of specimens were measured and put into the test software; The outsides of non-welded parts of the bar were clamped in the grips, after which the peel test can be started; After peel test, the specimen was removed from grip; The testing environment: 23+/−2° C., 50+/−10% RH. The maximum peel force (in Newton) is reported in Table 4. * Preload (the value is not zeroed after starting test): The exact value was set based on initial load of each sample when the test bar was just clamped in grips, before start test.

Warpage

[0069] Warpage is tested by cutting test samples of for example 100 mm×40 mm from an extruded plate of 4 mm in flow direction and contra flow direction and in various positions over the width of the extruded plate and expose these test samples at 100° C. for 24 hrs. The dimensional change can visually be recorded and qualitatively assessed. The scale ranges from no warpage at all, thus completely flat as “+++” via curled up at the edges “+/−”, to ultimately completely distorted, denoted by “−−−”. Results are given in Table 4.

Chemical Resistance

[0070] In order to assess the resistance of the compositions as described under examples 2 and 3, chemical resistance was evaluated. 1BA tensile bars were subjected to 672 h of ageing in 75% Ethanol (23° C.), 30% Phosphoric acid aqueous solution (60° C.), 3% Phosphoric acid aqueous solution (60° C.), 14% NaClO aqueous solution (23° C.), 200 ppm NaClO aqueous solution (23° C.) and 2000 ppm peracetic acid aqueous solution (23° C.). In none of the above-mentioned chemicals, a drop in mechanical properties (by means of elongation at break) was observed. Mechanical testing was performed according to ISO527.

TABLE-US-00004 TABLE 4 Results Maximum Maximum Tensile Peel force at Peel force at G′.sub.τ=−40° C. G′.sub.τ=23° C. G′.sub.τ=100° C. strength 55% power 70% power (MPa) (MPa) (MPa) (MPa) Warpage (N) (N) Example 1 455 135 36 30 ++ 1 87 Example 2 397 90 27 32 ++ 27 151 Example 3 358 65 23 31 +++ 74 187 Example 4 569 177 50 n.d. +/− n.d. n.d. Example 5 537 155 44 n.d. + n.d. n.d. Comparative 484 103 47 23 − <0.5* <0.5* experiment A Comparative 1100 892 123 n.d. −−− <0.5* <0.5* experiment B Comparative 288 32 14 27 +++ n.d. n.d. experiment C *Peel forces were tried to be measured, but weld strength was very bad, therefore the value was set to less than 0.5; n.d. = not determined.

[0071] Surprisingly, a conveyor belt according to the invention with a similar G′ at room temperature, which is a measure for the stiffness of the belt, exhibited a much higher tensile strength. Surprisingly, even a much softer extruded conveyor belt (example 3), still exhibited a high tensile strength in combination with a high peel strength, which is indicated by a high peel force. The conveyor belt according to the invention exhibited low warpage, thus were substantially flat in combination with a high peel strength.