KR101308153B1 - Method of recylcing waste plastics containing natural fiber filler - Google Patents

Abstract

The present invention relates to a method for recycling waste plastics containing natural fiber-based fillers such as hemp or wood flour, and more particularly, washing, drying and pulverizing waste plastics containing natural fiber-based fillers. Regeneration comprising preparing a starch nanocomposite by mixing and drying ceramic nanoparticles having an average size of 2 to 20 nm with an aqueous solution of starch, and melting and extruding the mixture including the materials of the respective steps. A method for producing a polymer composition. According to the production method according to the present invention it is possible to stabilize the physical properties of the polymer composition produced by recycling the waste plastic by the incorporation of the starch nanocomposite, thereby to recycle the natural fiber-based filler-containing waste plastic that has been mostly disposed of It has the advantage of being able to.

Description

Recycling method of waste plastic containing natural fiber filler {METHOD OF RECYLCING WASTE PLASTICS CONTAINING NATURAL FIBER FILLER}

The present invention relates to a method for recycling waste plastics containing natural fiber fillers, such as hemp and wood flour. In particular, the waste plastics containing natural fiber fillers are pulverized, washed, dried and mixed together with the previously prepared fibrous material. The present invention relates to a method for producing a recycled polymer composition having a relatively homogeneous physical property by melt extrusion.

Recently, the use of plastic materials in automobile parts is increasing. In particular, polypropylene (PP) resin is a trend of replacing the ABS or nylon resin that has been used as a conventional material for automobile parts because of the low cost, low specific gravity and easy processing. Examples thereof include PP composite materials used as automotive interior parts. In general, as automotive interior parts, various fillers are added to PP resin to reinforce impact resistance and strength. Recently, the use of parts molded of composite materials using natural fiber fillers such as hemp, cotton, wood powder, and paper powder, which are easily decomposed in nature, has been increasing for the development of eco-friendly vehicles.

Accordingly, researches on technologies for recycling polymer composite materials containing natural fiber fillers have been actively conducted. However, when applying the recycling technology of the conventional plastic material, the polymer composite material containing the natural fiber filler is difficult to recycle. The reason for this is that it is difficult to penetrate and absorb the washing water into the natural plastic filler of waste plastic in the washing process for recycling, so that the physical properties of the composite material manufactured through the extrusion and cooling process, which is the next process, This is because the phenomenon of deterioration appears. In addition, the content of spine-based fillers is not constant according to the collection source of waste plastics, and the physical properties due to the physicochemical interaction between the fibers and the matrix polymers during the extrusion process are expressed at an unpredictable level depending on the fiber type. There is a problem that it is difficult to stabilize the physical properties of the polymer composition to a certain level. Accordingly, the current plastic recycling industry separates and recycles only polymer composite materials that can be applied to existing recycling technologies, and polymer composite materials containing natural fiber fillers above a certain level are classified as waste and disposed of in full by disposal of landfill or incineration. It's happening.

Therefore, for the regeneration of waste plastics containing natural fiber fillers, it is necessary to compensate for the deterioration of physical properties caused by water absorption and physicochemical denaturation during the regeneration process, and to minimize the change of physical properties according to waste plastic lots. There is a need for a method of recycling waste plastics.

Thus, the inventors of the present invention, as a result of research efforts to solve the above problems, set the conditions that can be recycled waste plastic containing natural fiber-based fillers. According to this, it is possible to secure the homogeneity of physical properties by compensating for the deterioration of the physical properties by using recycled polymers containing the filamentary fiber fillers and by re-adjusting the difference in the content of the natural fiber fillers according to the lot of waste plastics during the recycling process. It is an object of the present invention to provide a method for producing a waste plastic based recycled polymer composition.

The present invention relates to a method for recycling waste plastics containing natural fiber-based fillers, and in particular, in order to compensate for the deterioration of physical properties that appear after melt-extrusion by washing and drying the pulverized waste plastics. Nano-ceramic particles of 2 to 20 nm size are mixed and recycled by adding additional fibrous materials in arbitrary proportion to the mixture to compensate and adjust the difference of natural fiber content according to the source of waste plastics. It is characterized by providing a method for producing a recycled polymer-based recycled polymer composition, which can ensure homogeneity of physical properties by maintaining a constant fibrous filler content in the polymer composition.

As described above, according to the present invention, a regenerated polymer composition may be provided by mixing and melt-extruding a fibrous filler and ceramic nanoparticles in a regeneration process of waste plastic containing a natural fiber filler. As a result, it is possible to compensate for the deterioration of physical properties caused by water absorption and physicochemical denaturation during waste plastic recycling, and to minimize the change of physical properties according to waste plastic lots.

The present invention is described in more detail as follows.

The present invention comprises the steps of preparing a recycled plastic by pulverizing and then washing and drying the waste plastic containing a natural fiber-based filler;

Preparing a fibrous pulverized product by grinding natural fibers, synthetic fibers, wood, or paper;

Preparing a starch nanocomposite by mixing and drying ceramic nanoparticles having an average size of 2 to 20 nm with an aqueous starch solution; And

It provides a method for producing a recycled polymer composition comprising the step of melt-extruding a mixture comprising the materials prepared in each step.

Waste plastics containing natural fiber fillers used in the present invention can be collected from various sources such as automobile interior parts, household goods, industrial parts, and the like. Matrix polymers used in waste plastics are mainly polypropylene, polyethylene, PVC, ABS, nylon, or polymer alloys in combination thereof. According to the present invention, the collected waste plastic is pulverized to a size of 1 to 15 nm using a mechanical method, and the pulverized product is mixed with excess water in a water bath to remove impurities containing coating fragments and the like, followed by drying and regeneration. Plastic can be prepared.

The starch nanocomposite in the present invention may be prepared by mixing and drying ceramic nanoparticles having an average size of 2 to 20 nm with an aqueous starch solution. Ceramic nanoparticles in the present invention can be used as a product provided in the form of powder or colloidal solution. The ceramic nanoparticles may be mixed in an aqueous solution of starch and mixed at a nano level by a dispersion method such as ultrasonic waves. Starch may be attached to a surface of the nanoparticles to prevent aggregation of nanoparticles. In this case, low molecular weight alcohols such as ethanol may be added to the starch aqueous solution to improve dispersion characteristics or to facilitate drying.

The ceramic nanoparticles may be one of nanodiamonds, nano zinc oxides, nano aluminum oxides, nano iron oxides, or a combination thereof. If the average size of the ceramic nanoparticles is 2nm or less, there may be a problem that the nanoparticles aggregate with each other in the melt extrusion step. On the other hand, when the average size of the ceramic nanoparticles is 20nm or more, since the surface area per unit weight is greatly reduced, it is necessary to increase the amount of ceramic nanoparticles used to supplement the physical properties of the recycled polymer composition. As a result, the melt processability of the recycled polymer composition is lowered, and the production cost thereof is increased, making it difficult to obtain economical efficiency.

When the starch nanocomposite is mixed into a mixture of waste plastic and fibrous pulverized and melt extruded in an extrusion apparatus, ceramic nanoparticles having an average size of 2 to 20 nm act on the molten polymer chain to prevent the melt state of the polymer from being non-Newtonian. It can be transformed from the fluid to a state close to the Newtonian fluid, thereby acting to increase the compatibility between the matrix polymer and the fibrous mill. In addition, a considerable amount of the ceramic nanoparticles of the starch nanocomposite is adsorbed on the surface of the fibrous filler in the regenerated polymer composition together with the starch adsorbed on the surface and increases the affinity between the fibrous filler and the matrix polymer, It can enhance the reinforcing effect. In addition, ceramic nanoparticles having an average size of 2 to 20 nm may be dispersed in the matrix polymer to function as nucleating agents. The thermal and regeneration of the recycled polymer composition may be induced by causing nano-level crystallization of the matrix polymer during the cooling process after melt extrusion. It can serve to improve mechanical properties.

The starch nanocomposite may contain 80 to 99.9 wt% of starch and 0.1 to 20 wt% of ceramic nanoparticles. If the content of the ceramic nanoparticles is lower than 0.1 wt%, the nanoparticle content in the finally produced regenerated polymer composition may be too low, so that the improvement of physical properties including improvement of the melt processing property may be insignificant. The dispersing effect of the particles can be reduced.

Natural fiber-based fillers contained in the waste plastic according to the present invention include hemp, cotton, silk, pulp and the like. However, the content of the natural fiber-based filler in the waste plastic is very diverse depending on the collection source, the waste plastic that can be applied to the present invention is preferably a natural fiber-based filler content of 5 to 60% by weight. For example, when the content of the natural fiber-based filler is 5% by weight or less, even if the conventional general recycling technology is applied, the deterioration of physical properties is not large, and the economical benefits due to recycling are not large. On the other hand, when the content of the natural fiber-based filler exceeds 60% by weight, there is a high risk of carbonization during processing such as melt extrusion, injection molding remarkably decreases, and the properties of the extrudate cooling and water absorption in the processing process There is a problem that it is difficult to compensate for the degradation.

The recycled polymer composition prepared according to the present invention may be prepared by further adding a fibrous pulverized product to the waste plastic containing the natural fiber filler. The fibrous pulverized product may be prepared by pulverizing natural fibers, synthetic fibers, wood, or paper to a size dispersible in the molten polymer. Meanwhile, in order to prepare a more inexpensive regenerated polymer composition, the fibrous pulverized product may be prepared by separating and regenerating only the fibrous material among waste automobile interior parts, waste household goods, waste clothes, or discarded industrial parts separately.

The mixing ratio of the waste plastic and the fibrous pulverized product may be arbitrarily adjusted according to the physical properties required according to the content of the natural fiber filler included in the waste plastic and the use of the recycled polymer composition. For example, it is natural that the lower the content of the natural fiber filler of the waste plastic, or the higher the content of the fiber filler content of the recycled polymer composition, the higher the mixing ratio of the fibrous pulverized powder to the waste plastic.

The recycled plastic, the fibrous pulverized product, and the starch nanocomposite powder prepared according to the above method may be mixed in a Henschel mixer and melt-extruded as a strand through a conventional extrusion apparatus to prepare a recycled polymer composition. The regenerated polymer composition according to the present invention may be prepared by mixing and melt extruding only regenerated plastic and starch nanocomposite, but considering that the natural fiber content in the regenerated plastic may show a large variation depending on the collection source, It is advantageous to stabilize the physical properties of the recycled polymer composition to a certain level by optionally adding fibrous grounds. Preferred compounding examples thereof include 50 to 90% by weight of recycled plastics, 9.9 to 49.9% by weight of fibrous ground products, and 0.1 to 10% by weight of starch nanocomposites.

The operating temperature of the extrusion apparatus in the melt extrusion step of the present invention is preferably 180 ~ 240 ℃. Below 180 ° C., the matrix polymer such as polypropylene may not be sufficiently melted, and thus the fiber filler may not be uniformly mixed with the matrix polymer. If the temperature exceeds 240 ° C., the fiber filler or matrix polymer may be carbonized or modified by high temperature. Physical properties of the recycled polymer composition may be significantly reduced.

In the present invention, in addition to recycled plastics prepared from waste plastics containing natural fibers, an inexpensive plastic raw material such as polypropylene or polyethylene can be added at any ratio and melt-extruded to increase the content of the matrix polymer in the recycled polymer composition. Of course. In addition, matrix polymers having poor compatibility with each other may exist in accordance with each collection source of waste plastics, and a conventional compatibilizer may be additionally added for the purpose of improving compatibility therebetween. Examples of the compatibilizer suitable for the present invention include maleic acid-modified polypropylene, silane-based compounds, epoxy-modified polyvinyl compounds and the like. In addition, the recycled polymer composition according to the present invention may further contain various additives such as antioxidants, colorants, mold release agents, lubricants, light stabilizers, rubbers, and the amount of these additives used depends on various factors including the desired end use and properties. It can be adjusted and applied accordingly.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example  1: preparation of recycled plastic

Residual scraps of the interior parts of scrapped cars were collected, ground to an average size of 10-20 mm, washed with water, and dried in a hot air dryer to prepare recycled plastics. As a result of dissolving the recycled plastic with an organic solvent to separate the matrix polymer and the fibrous material, the matrix polymer of the recycled plastic has polypropylene as a main component, and the component of the fibrous material is natural hemp fiber, the content of which is the total weight of the recycled plastic. It was found that 25% by weight.

Example  2: Fibrous Crushed  Ready

Fibrous pulverized products were prepared by collecting various types of industrial filters, parts, materials, etc., made of natural fibers, synthetic fibers, wood, or paper, and then grinding them to an average size of 2 mm.

Example  3: Preparation of Starch Nanocomposites

Starch nanocomposites were prepared by obtaining nano zinc oxide powder having an average size of 10 nm from NanoLead Co., Ltd., into an aqueous starch solution, dispersing by applying ultrasonic waves, and drying the powder by hot air drying. Nano zinc oxide content in the dried starch nanocomposite powder was adjusted to 5.0% by weight.

Example  4: play Polymer  Preparation of the composition

2 kg of the recycled plastic, 1 kg of polypropylene, 1100 g of the fibrous pulverized product, 300 g of the starch nanocomposite, 100 g of maleic acid modified polypropylene, and 60 g of zinc stearate were mixed and mixed with a Henschel mixer, using a general extrusion apparatus. It melt-extruded by the diameter of 20-30 mm thickness at the temperature of ° C. The extrudate was cooled through a cooling roll, cut into 50-70 mm lengths, immersed in a cooling water tank for about 20-30 seconds, then subjected to a cooling process through air, and then ground to a size of 2-3 mm to prepare a recycled polymer composition. .

Comparative example  1: Regeneration Without Starch Nanocomposites Polymer  Preparation of the composition

2 kg of the recycled plastic, 1 kg of polypropylene, 1100 g of the fibrous ground product, 100 g of maleic acid modified polypropylene, and 60 g of zinc stearate were mixed in a Henschel mixer, and the starch nanocomposite was not used using the same method as in Example 4. Recycled polymer composition was prepared.

Test Example  1: play Polymer  Measurement of the mechanical properties of the composition

Specific Gravity, Izod Impact Strength, Tensile Strength, Elongation at Break, Flexural Strength, Using Specimens Made by Injection Molding the Crushed Polymer Compositions of Example 4 and Comparative Example 1 The hardness was measured. Mechanical properties were measured and averaged for 7 specimens of each type, and the results are shown in Table 1 below.

play Polymer  Specific gravity and mechanical properties of the composition importance
(g / cm ³ ) Impact strength
(Kgfcm / cm) The tensile strength
(Kgf / cm ² ) Elongation at break
(%) Flexural strength
(Kgf / cm ² ) Flexural modulus
(Kgf / cm ² ) Hardness
(R scale) Example 4 0.989 3.6 263 41 387 27325 99.7 Comparative Example 1 0.982 2.2 227 16 340 22699 89.8

Referring to Table 1, the recycled polymer composition of Example 4 prepared using starch nanocomposites tended to have a slightly increased specific gravity compared to Comparative Example 1 prepared without using starch nanocomposites, but overall mechanical properties It has been shown to improve.

Claims (4)

Pulverizing waste plastics containing natural fiber fillers, followed by washing and drying to prepare recycled plastics;
Preparing a fibrous pulverized product by grinding natural fibers, synthetic fibers, wood, or paper;
Preparing a starch nanocomposite by mixing and drying ceramic nanoparticles having an average size of 2 to 20 nm with an aqueous starch solution; And
Mechanically mixing the materials prepared in each step and then extruding the melt;
Method for producing a recycled polymer composition comprising a.
The method of claim 1, wherein the starch nanocomposite contains 80 to 99.9 wt% of starch and 0.1 to 20 wt% of ceramic nanoparticles.
The method of claim 2, wherein the polymer composition comprises 50 to 90% by weight of recycled plastic, 9.9 to 49.9% by weight of fibrous ground material, and 0.1 to 10% by weight of starch nanocomposite.
The method of claim 1, wherein after the melt-extruded step, the extrudate is cooled through a cooling roll, cut into 50-70 mm lengths, and deposited in a cooling water tank for 20-30 seconds, followed by a cooling process through air, and then 2-3 mm. The method of producing a recycled polymer composition further comprising the step of grinding to size.