WO2019192958A1

WO2019192958A1 - Modular conveyor belt

Info

Publication number: WO2019192958A1
Application number: PCT/EP2019/058182
Authority: WO
Inventors: Ronald Michaël Alexander Maria SCHELLEKENS; Andreas Antonius Oosterlaken
Original assignee: Dsm Ip Assets B.V.
Priority date: 2018-04-03
Filing date: 2019-04-01
Publication date: 2019-10-10

Abstract

This invention relates to a modular conveyor belt comprising belt modules comprising polyethylene terephthalate (PET), wherein the PET exhibits a relative solution viscosity (RSV) of at least 1.30 as measured according to ISO 1628-5 5:1998 with dichloroacetic acid as a solvent. The invention also relates to a process for preparing such modular conveyor belt as well as a process to transport meat and/or poultry with such a modular conveyor belt.

Description

MODULAR CONVEYOR BELT

This invention relates to a modular conveyor belt. Modular conveyor belts are known and for example described in US7097030. These belts convey materials, usually in plants. Especially when conveying edible goods such as meat and poultry, these belts need to be cleaned regularly. When transporting edible goods, such as meat and poultry, it is essential that high hygiene standards are applied, and thus a conveyor belt transporting these goods must be able to withstand all kind of chemicals, which are usually used to clean these belts, such as for example a high resistance against cleaning solutions containing sodium hypochlorite and sodium hydroxide. Another important aspect is that these belts also need to exhibit a good cut-resistance, so that the belts are not damaged in case it conveys sharp goods, such as meat with sharp bones. Damaged belts are even more difficult to keep clean, as cuts may easily be contaminated and are more difficult to clean, which results in higher cleaning costs, and higher replacement rates, and thus leads to more waste.

Modular conveyor belts usually comprise many plastic belt modules arranged in an overlapping pattern. Many designs exist and are known to a person skilled in the art. For meat and poultry, the most commonly used plastic for belt modules is polyoxymethylene (POM), also known as acetal or polyacetal or polyformaldehyde, as this exhibits high strength, hardness and rigidity. A disadvantage, however, is that the cut resistance is insufficient. Another disadvantage of POM is that upon processing formaldehyde may be formed which is unhealthy for people.

It is thus an object of the present invention to provide a modular conveyor belt, which exhibits improved cut resistance. Surprisingly, this object is achieved with a modular conveyor belt comprising belt modules comprising

polyethylene terephthalate (PET), wherein the PET exhibits a relative solution viscosity (RSV) of at least 1 .30 as measured according to ISO 1628-5:1998 with dichloroacetic acid as a solvent. The modular conveyor belt according to the invention combines high cut resistance with sufficient mechanical properties, such as strain at break and E- modulus.

Many plastics have been mentioned as a suitable material for conveyor belts. EP3031752A1 for example lists many suitable plastics for belts in the tobacco industry, in which list also PET is mentioned. However, not any PET provides a modular conveyor belt with the required cut resistance and sufficient mechanical properties. Surprisingly, the inventors have found that a modular conveyor belt comprising belt modules comprising PET exhibiting a RSV of at least 1.30, the conveyor belt exhibits good cut resistance with the required mechanical properties.

This has been exemplified by examples.

The belt modules can be prepared by methods known to a person skilled in the art, including injection molding.

Another advantage of the modular conveyor belt according to the invention is that it can be operated over a wide temperature range, such as for example between 50 and 1 15 °C, but may also be employed at lower temperatures such as for example at least 1 °C. This also allows cleaning the modular conveyor belts, with chemicals at an elevated temperature, without damaging the belt. Surprisingly, the modular conveyor belt according to the invention can also be operated under humid conditions.

The relative solution viscosity of PET is a property known as such and can be influenced by the polymerization conditions. The relative solution viscosity may further be increased by for example solid state post condensation processes, which are also known per se.

Viscosity number (VN) as calculated by ISO 1628-5:1998 can be expressed in relative solution viscosity by the following formula: VN = (h_G -1 ) x 1/c (Formula 1 )

In which h_G is the relative solution viscosity (RSV) and c is the polymer concentration prescribed by the ISO norm (0.005 g/ml).

Preferably, the modular conveyor belt comprising belt modules comprises polyethylene terephthalate (PET), wherein the PET exhibits an RSV of at least 1.35 as measured according to ISO 1628-5:1998 with dichloroacetic acid as a solvent, more preferably at least 1.45 and even more preferred at least 1.55.

Surprisingly, the cut resistance improves upon having a higher RSV.

Surprisingly, the inventors have found that preparing a modular conveyor belt according to the invention requires the use of a PET with an RSV being higher than the RSV of the PET in the modular conveyor belt. Without wishing to be bound by theory, the inventors believe that upon preparing of the conveyor belt modules, the PET undergoes a decrease in RSV. The present invention thus also relates to a process for preparing a modular conveyor belt comprising belt modules comprising PET, comprising at least the following steps:

• Providing PET having an initial RSV of at least 1.50.

• Bringing the PET to a temperature of between 260 °C and 290 °C to form a melt;

• Injecting the melt into a mold of at least 120 °C;

• Cooling the mold so that the melt solidifies into a belt module;

• Ejecting the belt module;

• Assembling the belt module into a modular conveyor belt.

Surprisingly, this results in a modular conveyor belt exhibiting improved cut resistance.

With“initial RSV” is herein meant the RSV of the polymer before being subjected to processing into a part, in this case into a belt module. Preferably, the initial RSV of the PET is at least 1.50, more preferably 1.55, even more preferred at least 1.60 and most preferred at least 1.70.

Preferably, the process is carried out with PET with a low moisture content, such as for example with a PET with a moisture content of at most 0.02 wt%, preferably at most 0.01 wt%, with respect to the total weight of the PET. This has the advantage that the decrease in viscosity is limited. Preferably, the PET is subjected to a drying step before bringing the PET to a temperature of between 260 °C and 290 °C to form a melt, to decrease the moisture content of the PET. Drying may be done by known means.

The belt modules comprising PET may further comprise other ingredients, which are as such commonly known in the industry and include for example glass fibers, nucleating agents, mold release agents, colorants, flame- retardants, Polytetrafluoroethylene (PTFE) etc. Nucleating agent for example includes sodium benzoate. Preferably, the belt module comprises PET in an amount of at least 80 wt%, wherein the weight percentage is with respect to total weight of the belt module. More preferably, the belt module comprises PET in an amount of at least 90 wt%, and most preferred in an amount of at least 95 wt%.

The invention also relates to a process for transporting meat and/or poultry, comprising at least the following steps:

a. Providing meat and/or poultry on a modular conveyor belt; b. Moving the modular conveyor belt with the meat and/or poultry in a desired direction;

wherein the modular conveyor belt is a belt according to the present invention as disclosed above. Surprisingly, this process of transportation is quick and requires less cleaning steps as compared to a process in which a modular conveyor belt of for example POM is used.

Materials used

POM: Natural Acetal H2320, delivered by BASF.

PET-A, polyethylene terephthalate having an initial RSV of 1.55. The material contains 0.15% sodium benzoate nucleating agent, delivered by Univar Benelux, and 0.25% Loxiol G32 mould release agent, delivered by Emery Oleochemicals Group.

PET-B, polyethylene terephthalate having an initial RSV of 1 .66.

PET-C, polyethylene terephthalate having an initial RSV of 1.80.

Preparation of test bars by Injection moulding

PET test bars 150x18x4 mm³ for cut-resistance tests and tensile test bars according to ISO 527 were injection molded from pre-dried (10 hours at 120 °C under vacuum with nitrogen flow) granules on an Engel e-VC1 10 injection molding machine, with temperature settings 260-275 °C, and mold temperature of 140 °C. The POM acetal H2320 parts have been injection molded at temperature setting 190-200°C, and mold temperature of 90 °C.

Relative solution viscosity

The relative solution viscosity was determined in a solution of 0.5 gram of material in 100 ml of dichloroacetic acid at 25 °C according to ISO 1628-5:1998. Table 1 provides the relative solution viscosities of the material before preparation of the part (“initial RSV”), as well as after a part was being prepared (“RSV part”). Cut-resistance test

Evaluation of the cut resistant on PET 150x18x4 mm test bars provide a friction force and cutting depth. A knife cuts in a plate with a defined load, angle, and speed. The friction force was measured during the test, after the test the cutting depth and the exact cutting angle were measured with an optical microscope. The cut-resistance was evaluated on Zwick 1445 testing machine including a 2kN loadcell. Cutting knife Martor Argentax Nr. 44, length 39mm, width 19.3mm, thickness: 0.3mm. Blade: two-sided cut. The speed of the knife was 5mm/s, test length 40 mm, and load 34.84 N.

Cut resistance can generally be measured on a materials testing machine with a 2 kN loadcell, e.g. a Zwick 1445, with the knife as specified above, at a speed of 5mm/s, test length 40 mm, and a load 34.84 N.

For the depth measurement, a cross section perpendicular on the cut direction was made. Sawmachine Varga 1 was used for cutting the samples. Struers Polishing machine, LaboPol-25 was used to polish the cross section. The cutting depth was measured using an Olympus SZX10 stereo microscope.

Mechanical properties

The tensile test was carried out at 23 °C with injection moulded ISO 527 type 1 A bars. Testing of the tensile test bars occurred in accordance with the ISO 527 standard. Tensile testing speed 50 mm/min was used.

Table 1

Table 2

Comparative experiment A

POM test bars were injection molded and cut-resistance on the plaques was evaluated. As shown in Table 1 , cut-resistance depth is 972 pm and cut force 86.3 N.

Examples I - III

PET materials with different initial RSV were injection molded and cut-resistance evaluated. The cut resistance and cut force of the relatively lower molecular weight PET-A are significantly below the POM material. The material based on the higher molecular weight PET-C show even lower cut resistance depth.

Claims

1 . Modular conveyor belt comprising belt modules comprising polyethylene

terephthalate (PET), wherein the PET exhibits a relative solution viscosity (RSV) of at least 1.30 as measured according to ISO 1628-5: 1998 with dichloroacetic acid as a solvent.

2. Modular conveyor belt according to claim 1 , wherein the PET exhibits an RSV of at least 1.40, more preferably at least 1.45 and even more preferred at least 1.55.

3. Modular conveyor belt according to claim 1 or 2, wherein the belt module further comprises mold release agent, nucleating agent, glass fibers, and combinations thereof.

4. Modular conveyor belt according to any one of the preceding claims, wherein the belt module comprises PET in an amount of at least 90 wt%, with respect to the total weight of the belt module.

5. Modular conveyor belt according to any one of the preceding claims, wherein the belt module exhibits a cut resistance depth of at most 800 micrometer as measured according to the method in the description.

6. Process for preparing a modular conveyor belt according to any one of the preceding claims, comprising at least the following steps:

• Providing PET having an initial relative solution viscosity of at least 1.50;

• Injecting the melt into a mold;

• Cooling the mold so that the melt solidifies into a belt module;

• Ejecting the belt module;

• Assembling the belt module into a modular conveyor belt.

7. Process according to claim 6, wherein the initial relative solution viscosity is at least 1.65.

8. Process according to claim 6 or 7, wherein PET is provided having a moisture content of at most 0.02 wt% with respect to the total weight of the PET.

9. Process according to any one of claims 6 to 8, wherein a drying step is applied to the PET before bringing the PET to a temperature of between 260 °C and 290 °C to form a melt.

10. Process for transporting meat and/or poultry, comprising at least the following steps:

a. Providing meat and/or poultry on a modular conveyor belt;

b. Moving the modular conveyor belt with the meat and/or poultry in a desired direction;

wherein the modular conveyor belt is a belt according to any one of the claims 1 to 5.