WO2018124986A1

WO2018124986A1 - Fiber reinforced expanded polystyrene (eps) foam block

Info

Publication number: WO2018124986A1
Application number: PCT/TR2016/050553
Authority: WO
Inventors: Onur AKAY; Abdullah Tolga OZER
Original assignee: Akay Onur; Ozer Abdullah Tolga
Priority date: 2016-12-28
Filing date: 2016-12-28
Publication date: 2018-07-05

Abstract

The invention is related to a method for producing a fiber reinforced expanded polystyrene (EPS) foam block, comprising the steps of feeding fiber into a mixing process and stirring the fiber uniformly and randomly with matured pre-foamed polystyrene beads to an in-line molding process for making blocks of fiber reinforced EPS foam.

Description

FIBER REINFORCED EXPANDED POLYSTYRENE (EPS) FOAM

BLOCK

Technical Field

The invention is related to a method for producing a fiber reinforced expanded polystyrene (EPS) foam block that includes man-made or natural fiber.

The invention is particularly related to a method for producing a fiber reinforced expanded polystyrene (EPS) foam block, comprising the steps of feeding fiber into a mixing process and stirring the fiber uniformly and randomly with matured pre-foamed polystyrene beads to an in-line molding process for making blocks of fiber reinforced EPS foam.

Prior Art

Polystyrene is a petroleum-based, non-biodegradable polymer made from the monomer styrene. Polystyrene can be manufactured in solid form to create many different economical plastic objects by injection molding and vacuum molding techniques. Regardless of wide application areas, solid polystyrene has limited usage in engineering applications due to the tradeoff between toughness and stiffness. In general, fibers are used to improve the mechanical characteristics of polymeric structures such as elastic modulus, impact resistance and tensile strength. For example, US Patent 4,894,281 relates to a fiber-reinforced polymer molded body comprising a polymer matrix and a reinforcing layer fiber laminated with or embedded in the polymer matrix. In an another example, in order to increase the toughness of solid form of polystyrene polymer, the patent WO 2008/042090 A2 introduced a method for making fiber reinforced polystyrene composites in which an extrusion compounding process (feeding fiber into polymer resin melt) and a molding process (cooling said fiber reinforced polystyrene melt to form a solid) was coupled. The patent WO 2008/042090 A2 can be used to make molded articles including household appliances, automotive parts, and boat hulls. Polystyrene can also be expandable by the impregnation of expanding agents (usually pentane) during the polymerization of styrene. Additionally, athermanous materials such as carbon black, graphite, metal oxides, metal powders or pigment dyes can also be incorporated to improve the insulating properties as stated in patent US 2015/0175765 Al . In order to expand the polystyrene, steam is usually applied causing the pentane gas within the polystyrene granules (polystyrene beads), which are about the size of sugar granules, to boil. During this pre- expansion stage, the tiny solid expandable polystyrene beads become pre-foamed beads by undergoing a volume increase of 40 to 50 times their original size. Following a conditioning stage in which the pre-foamed beads reach an equilibrium temperature and pressure, the matured pre-foamed beads are transferred and filled into a molding machine. During this final molding stage, matured pre-foamed beads expand further under applied steam and pressure. As a result, the expanded polystyrene (EPS) beads (virgin EPS beads) completely fill the mold and fuse together. The product manufactured by this process is named as expanded polystyrene (EPS) foam. Depending on the type of the molding, EPS foam can be in block form (named as EPS foam block) or in custom-shaped form (named as EPS foam packaging). EPS foam blocks can be cut into sheets for use in building/construction applications such as thermal insulation in the building industry. On the other hand, EPS foam packaging is mainly used in food packaging industry (e.g. leak-free food containers, single-use foodservice products, etc.) and in electronics packaging industry (e.g. protective packaging for electronic items such as televisions, appliances, etc.).

Due to their lightweight aspect (approximately 50 - 100 times lighter than conventional compacted earth fill), EPS foam blocks have found many different applications in civil engineering such as constructing highway embankments and bridge approach ramps over soft soil sites, protecting buried pipelines against excess vertical pressures, creating terrain and terraces on the rooftop of existing structures without imposing significant pressures to the structural frame, reducing the both seismic and lateral forces acting on the retaining walls, increasing slope stability by reducing driving forces, etc. The compressive strength of EPS foam blocks are the main design parameter for these civil engineering applications. The compressive strength of the EPS foam block used in a civil engineering project should be high enough to carry the design loads. As an elasto-plastic material, the compressive strength of an EPS foam block is a function of strain (the ratio of the deformation under loading to the original length of the EPS foam block). For this reason, the compressive strength of an EPS foam block is reported at various strains from 1% to as high as 50%. However, there is usually a maximum limit of allowable strain of selected EPS foam block depending on project specifications. For example, 10% or higher strain may be allowable for EPS foam blocks used for compressible inclusions (e.g. protecting buried pipelines against excess vertical pressures, reducing the both seismic and lateral forces acting on the retaining walls, etc.), whereas only 1% strain is generally allowed for EPS foam blocks used for roadway fill applications. For the majority of the aforementioned civil engineering applications, compressive strength at 1% or 5% strain is a design parameter for EPS foam blocks.

In addition to the large amounts of EPS foam waste added to the landfills across the globe each year, factories that manufacture EPS foam packaging or EPS foam block create their own EPS waste. For example, during hot wire cutting of EPS foam blocks into sheets for use in building/construction applications, EPS foam block molders create scrap EPS foam. The recycling of these EPS waste is extremely crucial since EPS is non-degradable and stockpiling them requires significant volumes of areas in landfills. In addition, the recycling of the EPS waste allows reduction in new expandable polystyrene production from petroleum, thus less greenhouse gas emissions are produced. In order to deliver environmental benefits through recycling, EPS foam block molders grind EPS foam wastes into regrind EPS beads and reuse them during block manufacturing. This is accomplished by mixing the regrind EPS beads with the matured pre- foamed beads before block molding. The ratio of the weight of the regrind EPS beads to the total weight of the EPS foam block indicates the recycle content of the final product in percentage by weight (wt%). However, the mechanical properties of the EPS foam block are adversely affected as the recycle content increased. For example, the compressive strength of EPS foam blocks reduces as the recycle content increases. Therefore, the recycling is generally limited to the manufacturing of EPS foam packaging since the reduced compressive strength of the products mostly meets the design criteria for the aforementioned food and electronics packaging industries. Nevertheless, in order to increase the recycle content of EPS foam packaging without impairing its mechanical properties, patent US 2016/0023379 Al presents a method for bonding regrind EPS beads together using powder adhesive and steam. Their example showed that the compressive strength of EPS foam packaging with 20% recycle content was improved as compared to that of non-recycled (virgin) EPS foam packaging at 50% strain.

The compressive strength of EPS foam block is proportional to its density. As a matter of fact, EPS foam blocks are classified based on their density by the standard ASTM D6817 published by ASTM International. For example, an EPS foam block with a density of 28.8 kg/m3 is classified as EPS29 by ASTM D6817. ASTM D6817 also provides the compressive strength of EPS foam blocks at 1%, 5%), and 10% strain. The need for increasing the compressive strength of EPS foam block without increasing its density could reduce the cost of the product since less expandable polystyrene beads will be used in the expansion and molding process. In addition, polystyrene is a petroleum product and non degradable. Increasing the compressive strength of EPS foam block without increasing the amount of expandable polystyrene beads is not only a need to save raw polystyrene material cost but also a need to reduce the green house emissions for raw polystyrene beads production. Although man-made and natural fibers are used as admixtures in civil engineering applications to increase the compressive strength of concrete and shear strength of soil due to the high tensile strength of fibers, no method is available that uses fibers as an admixture to increase the compressive strength of EPS foam blocks. There is a need for enhancing the compressive strength of EPS foam block without increasing its EPS density and maintaining the compressive strength of EPS foam block as recycle content increases. The present invention is designed to satisfy both of these needs by the inclusion of fiber into EPS foam block. The ratio of the weight of the fiber to the total weight of the EPS foam block indicates the fiber content of the final product in percentage by weight (wt%).

Summary of the Invention

The present invention is related to a method for producing a fiber reinforced EPS foam block that includes man-made or natural fiber. According to the present disclosure, an advantageous method for making a fiber reinforced EPS foam block article may comprise the steps of:

Step 100: mixing about 1 wt% to about 20 wt% of fiber, about 1 wt% to about 50 wt% of regrind EPS beads, about 30 wt% to about 98 wt% of matured pre-foamed polystyrene beads in a dry blend rotating mixer to obtain uniformly and randomly stirred mixture.

Step 102: transferring the mixture to a block molding machine.

Step 104: bonding the mixture together under pressure by introducing steam into the mold to raise the temperature of the matured pre-foamed polystyrene beads so that matured pre-foamed polystyrene beads expand further and completely fill the mold.

Step 106: cooling the bonded mixture in the mold, thereby producing a fiber reinforced EPS foam block with fiber content up to 20 wt% and recycle content up to 50 wt%.

The features and attributes of the disclosed method for making fiber reinforced EPS foam block will be apparent from the detailed description which follows, particularly when read in conjunction with the figures appended hereto. Brief Description of the Drawings

Figure 1 depicts a flow chart showing the method of molding fiber reinforced EPS foam block article using matured pre-foamed polystyrene beads, fiber, and regrind EPS beads according to the disclosure; Figure 2 depicts an exemplary schematic of a mixer machine for making dry blend mixture.

Detailed Description of the Invention

While this invention may be embodied in many forms, there is shown in the drawings and will herein be described in detail an embodiment with the understanding that this disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to the illustrated embodiment.

The invention is related to a method for producing a fiber reinforced expanded polystyrene (EPS) foam block that includes man-made or natural fiber. The method may allow for molding EPS foam block with over 1 wt% and up to 50 wt% of regrind foam beads. The regrind recycled foam beads may be made of expanded polystyrene (EPS), expanded polyethylene or any suitable expanded foam bead material.

Fibers may be man-made or natural. The natural fibers may be bamboo, coir, jute, kenaf, palm, sisal or any suitable natural fibers. Man-made fibers may be polyester, polyethylene, polypropylene, polyvinyl alcohol, glass, nylon, glass, rubber, waste plastic, carpet or any suitable man-made fibers. More specifically, the length of natural or manmade fibers is at least 6 mm.

Referring to Figure 1; the method comprises the following steps: Step 100: mixing about 1 wt% to about 20 wt% of fiber (10), about 1 wt% to about 50 wt% of regrind EPS beads (12), about 30 wt% to about 98 wt% of matured pre-foamed polystyrene beads (14) in a dry blend rotating mixer (16) to obtain uniformly and randomly stirred mixture (18).

Step 102: transferring the mixture (18) to a block molding machine.

Step 104: bonding the mixture (18) together under pressure by introducing steam into the mold to raise the temperature of the matured pre-foamed polystyrene beads (14) so that matured pre-foamed polystyrene beads expand further and completely fill the mold.

Step 106: cooling the bonded mixture in the mold, thereby producing a fiber reinforced EPS foam block with fiber (10) content up to 20 wt% and regrind EPS beads (12) up to 50 wt%.

In one exemplary embodiment, fiber (10), regrind EPS beads (12), and matured pre-foamed polystyrene beads (14) are fed into a dry blend rotating mixer (16) as depicted in Figure 2. Following a mixing process that can take up to 5 minutes, uniformly and randomly stirred mixture (18) exits the dry blend rotating mixer (16).

Referring again to Figure 2, dry blend rotating mixer (16) includes a drive motor (20) and mixing blades (22).

Referring to Figure 1, the process steps from 102 to 106 are widely used in EPS foam industry. Therefore, any widely used EPS foam block molding machine can be used as in-line molding process for making fiber reinforced EPS foam block from the mixture (18).

However, the temperature of the steam applied during the molding stage should be lower than that of melting point of fiber.

It should also be noted that since the regrind EPS beads have no residual pentane trapped in their cell structure, they cannot be fused together in a block form during the molding stage if one wants to manufacture a block with recycle content of 100%.

Claims

1. A method for producing a fiber reinforced EPS foam block article characterized in that, the method comprises the steps of:

- mixing fiber (10) and matured pre-foamed polystyrene beads (14) in a dry blend rotating mixer (16),

- transferring the mixture (18) to a block molding machine,

- bonding the mixture (18) together under pressure by introducing steam into the mold to raise the temperature of the matured pre-foamed polystyrene beads (14) so that matured pre-foamed polystyrene beads expand further and completely fill the mold,

- cooling the bonded mixture (18) in the mold, thereby producing a fiber reinforced EPS foam block.

2. A method according to claim 1 characterized in that regrind EPS beads (12) are also added to the dry blend rotating mixer (16).

3. A method according to claim 2 characterized in that, 1 wt% to 20 wt% of fiber (10), 1 wt% to about 50 wt% of regrind EPS beads (12) and 30 wt% to 98 wt% of matured pre-foamed polystyrene beads (14) are added to the dry blend rotating mixer (16).

4. A method according to claim 3 characterized in that mixing is realized in a dry blend rotating mixer (16) to obtain uniformly and randomly stirred mixture (18).

5. A method according to claim 3 characterized in that the regrind bead foam are made of expanded polystyrene (EPS) or expanded polyethylene.

6. A method according to claim 3 characterized in that said fiber is man-made.

7. A method according to claim 3 characterized in that said fiber is natural.

8. A method according to claim 6 characterized in that said man-made fiber is produced from polyester, polyethylene, polypropylene, polyvinyl alcohol, glass, nylon, glass, rubber, waste plastic, carpet, and combinations thereof.

9. A method according to claim 7 characterized in that said natural fiber is bamboo, coir, jute, kenaf, palm, sisal, and combinations thereof.