BR102018072078A2 - polyethylene composite with wood powder compatible for rotational molding and rotational molding production process - Google Patents

Abstract

polyethylene composite with wood powder compatible for rotational molding and rotational molding production process the composite presents the following mixture by weight:? 80% to 94% micronized polyethylene; ? 5% to 20% wood dust and? 1% to 10% of micronized compatibilizing agent. the particle size of the wood powder is in the range of 65 to 150 mesh. the micronized compatibilizing agent employed is graphitized polyethylene / grafted with maleic anhydride which is obtained through a chemical reaction of polyethylene with maleic anhydride resulting in a polymer containing branches with polar groups. the particle size of the compatibilizing agent and the polyethylene is in the range of 25 to 300 mesh. the process of producing plastic objects by rotational molding that employs said composite consists of the following operations: obtaining the wood powder by grinding wood residues; drying of wood dust; micronization of polyethylene; micronization of the compatibilizing agent; mixing and homogenizing the micronized polyethylene with the micronized compatibilizing agent and wood powder; mold preheating; feeding the homogenized mixture into the rotational molding mold; rotomoulding; cooling of the mold and extraction of the molded part from the interior of the mold.

Description

“POLYETHYLENE COMPOSITE WITH COMPATIBILIZED WOOD POWDER FOR ROTOMOLDING AND ROTOMOLDING PRODUCTION PROCESS”

INTRODUCTION [001] The present invention relates to an innovative composite of polyethylene reinforced with wood powder that is made compatible during the rotational molding process. The invention also relates to the process of producing plastic objects by rotational molding that employs said composite.

STATE OF THE TECHNIQUE [002] The rotational molding process, also called rotational molding, is characterized by employing thermoplastic material, temperature and low pressure, consisting of the following steps:

- Loading - a hollow and split mold is loaded with plastic resin and closed;

- Molding - the mold is heated and rotated according to a predetermined program;

- Cooling - the resin solidifies inside the mold taking its shape;

- Demoulding - the mold is opened and the cooled part is extracted from the mold.

[003] Wood fiber reinforced thermoplastics have been widely used, especially by the automotive and civil construction industry, due to their high resistance to the weather, the growing cost of virgin plastics and limited availability of wood.

[004] The processing of thermoplastics reinforced with wood fiber requires care with the humidity and granulometry of the wood residues, as well as the temperature of its processing. The high humidity and granulometry generate bubbles in the material, discontinuities and

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2/6 stains caused by the thermal oxidative process. Temperature control is crucial, in view of the cellulose degradation from approximately 200 ° C, which generates the release of volatiles, discoloration, odors and fragility of the composite. The characteristics of the reinforcement material, such as: particle size distribution, particle size, surface area and chemical nature of the surface and maximum volumetric fraction of the cargo's packaging are fundamental in the manufacture of a reinforced thermoplastic. Other factors that must be observed during the production of a wood fiber reinforced thermoplastic are: complete coating of the reinforcement material by the thermoplastic matrix (encapsulation), filling of the voids present in the wood, good matrix finishing and reinforcement, minimizing friction between reinforcement particles and occurrence of unwanted preferential orientations of the particles.

[005] Patent document BR 10 2014 003762-4 refers to a wood composite with polyethylene and polypropylene that uses wood powder in the granulometric range of 50 to 120 mesh and in the proportion of 1 to 60% and low polyethylene micronized density in the proportion of 40 to 99%. The composite is suggested for use in the rotational molding process. However, this document does not use a compatibilizing agent, nor does it make use of the compatibilization step that makes the interfacial interaction between the wood powder and the polymeric matrix feasible, and therefore, does not guarantee satisfactory properties for application in rotational molded thermoplastic products.

DESCRIPTION OF THE INVENTION [006] The purpose of the present invention is an innovative composite of polyethylene reinforced with wood powder that is made compatible during the rotational molding process, as well as the process of producing plastic objects by rotational molding that it uses

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3/6 said composite.

[007] The composite of the invention comprises the following mixture, by weight:

- 80% to 94% micronized polyethylene;

- 5% to 20% wood dust and

- 1% to 10% of micronized compatibilizing agent.

[008] The granulometry of the wood powder is in the range of 65 to 150 mesh. The micronized compatibilizing agent employed is graphitized polyethylene / grafted with maleic anhydride which is obtained through a chemical reaction of polyethylene with maleic anhydride resulting in a polymer containing branches with polar groups. The polar groups present are responsible for forming bridges between the nonpolar polymer and the polar fibers, that is, they improve the interfacial interaction between the fibers and the polymeric matrix, and consequently, increase the physical properties as, elasticity module in the flexion of the composites , resistance to impact and tension and elongation in flow. The micronization of polyethylene and the compatibilizing agent consists of grinding the material using a disc mill in the granulometry range of 25 to 300 mesh.

[009] The process of production of plastic objects by rotational molding that employs said composite consists of the following operations:

a) Obtaining wood dust by grinding wood residues;

b) Drying of wood dust;

c) Micronization of polyethylene;

d) Micronization of the compatibilizing agent;

e) Mixing and homogenizing the micronized polyethylene with the micronized compatibilizing agent and wood powder;

f) Preheat the mold;

g) Feeding the homogenized mixture inside the mold

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h) Rotomoulding;

i) Cooling of the mold;

j) Extraction of the molded part from the interior of the mold.

[010] Micronization is the process used to reduce the particle size of materials using knife or disc mills. Materials micronized at room temperature have a particle size between 0.210 mm to 0.420 mm.

[011] The term graftized is used to describe polymers submitted to the process of functionalization of polymer chains with capable compounds. The graphitized polyethylene used as a compatibilizer has in its structure groups of maleic anhydride grafted laterally in its main chain. The best interfacial interaction between the polymer occurs due to the reactions that occur between the acidic groups of the maleic anhydride and the hydroxyl groups on the surface of the wood particles promoting adhesion and improvement in the mechanical properties.

[012] The process preferably presents the following parameters:

- the wood powder has a particle size range between 65 to 150 mesh;

- the drying of the wood powder occurs at 23 to 110 ° C for 2 to 8 hours;

- the compatibilizing agent is graphitized polyethylene / grafted with maleic anhydride;

- the micronization of polyethylene and the compatibilizing agent consists of grinding the material using a disc mill in the granulometry range of 25 to 300 mesh;

- the preheating of the mold occurs in the temperature range of 120 to 160 ° C;

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- the rotational molding operation is carried out in the temperature range of 250 to 270 ° C for a period of 10 to 20 minutes;

- the cooling of the mold is forced with the aid of fans and spraying of water in a period of 10 to 15 minutes.

ADVANTAGES OF THE INVENTION [013] The composite of polyethylene reinforced with compatible wood powder, proposed by the present invention, results in the following advantages over the state of the art:

- the use of the graphitized polyethylene compatibilizing agent significantly increases the modulus of elasticity in flexion in relation to the sample without compatibilizer; this behavior can be attributed to the greater interfacial interaction between the polymeric matrix and the wood fibers, caused by the insertion of the compatibilizing agent.

EXAMPLES [014] Specimens were prepared to assess physical properties from rotomolded parts with a thickness of 3 ± 1 mm. For the dimensions to be guaranteed, the specimens were stamped using calibrated and specific cutting knives for the analysis. The formulations used in the rotational molding of the specimens were as follows:

FORMULATION RESIN DUST WOOD AGENT COMPAT. BENDING ELASTICITY MODULE (Mpa) CMP1 100 0 0 296 CMP2 95 5 0 312 CMP3 90 10 0 270 CMP4 85 15 0 52 CMP5 80 20 0 4 CMP11 85 10 5 356

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6/6 [015] In the formulation with 85% polyethylene, 10% wood powder and 5% graphitized polyethylene, an increase of 32% in the flexural modulus of elasticity in relation to the sample without compatibilizer with 10% powder was identified wooden. The use of the compatibilizer promotes a better interfacial interaction between the fibers and the polymeric matrix, improving the physical properties of the composites. The best interfacial interaction occurs due to the reactions that occur between the acidic groups of maleic anhydride and the hydroxyl groups on the surface of the wood particles.

[016] This behavior can be attributed to the greater interfacial interaction between the polymeric matrix and the wood fibers, caused by the insertion of the compatibilizing agent.

Claims (12)

1 - “POLYETHYL ENO COMPOSITE WITH POWDER COMPATIBILIZED WOOD FOR ROTOMOLDING ”characterized by presenting the following composition, by weight: - 80% to 94% micronized polyethylene; - 5% to 20% wood dust and - 1% to 10% of micronized compatibilizing agent. 2 - “POLYETHYLENE COMPOSITE WITH COMPATIBILIZED WOOD POWDER FOR ROTOMOLDING”, according to claim 1, characterized by the particle size of the wood powder in the range of 65 to 150 mesh. 3 - "POLYETHYLENE COMPOSITE WITH COMPATIBILIZED WOOD POWDER FOR ROTOMOLDING", according to claim 1, characterized by the micronized compatibilizing agent being graphitized / grafted polyethylene with maleic anhydride. 4 - “POLYETHYLENE COMPOSITE WITH COMPATIBILIZED WOOD POWDER FOR ROTOMOLDING”, according to claim 1, characterized by the granulometry of the compatibilizing agent and polyethylene in the range of 25 to 300 mesh. 5 - “ROTOMOLDA PRODUCTION PROCESS- GEM ”characterized by being made up of the following operations: - Obtaining wood dust by grinding wood residues; - Drying of wood dust; - Micronization of polyethylene; - Micronization of the compatibilizing agent; - Mixing and homogenizing the micronized polyethylene with the micronized compatibilizing agent and wood powder; - Preheat the mold; - Feeding the homogenized mixture inside the mold Petition 870180144868, of 10/26/2018, p. 78/82 2/2 rotational molding; - Rotomoulding; - Mold cooling; - Extraction of the molded part from the interior of the mold. 6 - “ROTOMOLDING PRODUCTION PROCESS”, according to claim 5, characterized by presenting the wood powder with a granulometric range of 65 to 150 mesh. 7 - "ROTOMOLDING PRODUCTION PROCESS", according to claim 5, characterized in that the drying of the wood powder occurs at 23 to 110 ° C for 2 to 8 hours. 8 - “ROTOMOLDING PRODUCTION PROCESS”, according to claim 5, characterized by being the compatibilizing agent graphitized / grafted with maleic anhydride. 9 - “ROTOMOLDING PRODUCTION PROCESS”, according to claim 5, characterized by the micronization of polyethylene and the compatibilizing agent in a disc mill. 10 - “ROTOMOLDING PRODUCTION PROCESS”, according to claim 5, characterized by the preheating of the mold in the temperature range of 120 to 160 ° C. 11 - “ROTOMOLDING PRODUCTION PROCESS”, according to claim 5, characterized by the rotational molding operation carried out in the temperature range of 250 to 270 ° C for a period of 10 to 20 minutes. 12 - "ROTOMOLDING PRODUCTION PROCESS", according to claim 5, characterized by the cooling of the forced mold with the aid of fans and water sprinkling in a period of 10 to 15 minutes.