JP4292195B2 - Recycling method for plastic waste - Google Patents

Description

  The present invention improves the physical properties of plastic materials in which various types of plastic materials are mixed, and in particular, recycles plastic waste materials that recycle many types of plastic materials and plastic waste materials to form plastic molded products with a certain mechanical strength. The present invention relates to a molding method.

Table 1 shows the results of analysis of components of plastic waste materials such as bottles, plastic containers such as trays, and plastic packaging materials such as films that are discharged as garbage from ordinary households.

  Each component varies depending on the city and time of collection, but plastic waste generally discharged as garbage is mainly composed of polypropylene and polyethylene as described above, and contains about 11% by weight of polystyrene, These three types of plastics account for 89% (weight) or more. Such plastic waste material is called “containable material” because it is mainly collected for the purpose of recycling plastic containers.

By the way, there are various methods for treating plastic waste containing many types of plastic materials, such as the thermal recycling method that burns as fuel, the chemical recycling method that returns to the raw material, and the new plastic molding material. There are material recycling laws to be used. Among these, the material recycling law is the most desirable treatment method from the viewpoint of resource saving, energy saving, economic efficiency, and environmental measures.
However, since the plastic waste is a mixture of many types of plastic materials with different properties, the conventional material recycling method causes phase separation between dissimilar materials when molding a molded product. There is a problem that the use as a product is limited because the impact strength is significantly reduced.

In addition, as shown in the following Patent Document 1 or the like, known stabilizers and modifiers that have been added to plastics in the past, metal deactivators, flame retardants, etc. are added to plastic waste materials, It has been considered to mix a so-called virgin material such as polyethylene with plastic waste material, but these methods have a problem in that the cost becomes high and sufficient mechanical strength cannot be achieved.
JP 2005-23190 A

  Accordingly, the present invention aims to provide a method for recycling plastic waste material that can overcome the drawbacks of the above-described conventional reforming materials and easily form a molded product having excellent mechanical strength with plastic waste material. .

For this purpose, the invention of the method for recycling molding of plastic waste material according to claim 1 is characterized in that the plastic waste material is composed of many kinds of plastic containers and plastic packaging materials that are discharged as garbage from general households. The main component is polyethylene, and polystyrene is contained in a lower proportion than both main components. These three components occupy 89% (weight) or more, while the modifiers are polystyrene and polybutadiene. 2 to 3 parts by weight of a fine powder made of calcium carbonate having an average particle size of 0.1 to 0.5 μm per 1 part by weight of the styrene thermoplastic elastomer copolymerized with Is added in a ratio of 1 to 20 parts by weight with respect to 100 parts by weight of the plastic waste material. At the same time, the plastic waste material is mixed and stirred by rotating the screw and blade of the mixing machine at high speed by turning it into a rotary blade type mixing machine, and the plastic waste material that has been melted by self-heating due to friction and turned into a gel state is molded It is formed into a predetermined shape by moving to a mold and applying pressure .
Further, the invention of the method for recycling molding of plastic waste material according to claim 2 is characterized in that the plastic waste material is composed of various kinds of plastic containers and plastic packaging materials discharged as garbage from general households, Polyethylene is the main component, and polystyrene is contained in a lower proportion than these two main components, and these three components account for 89% (weight)% or more, while the modifier is polystyrene and polyethylene. A mixture of 2 to 3 parts by weight of a fine powder made of calcium carbonate having an average particle size of 0.1 to 0.5 μm with respect to 1 part by weight of a styrene-based thermoplastic elastomer copolymerized with polybutylene, The plastic waste material is added at a ratio of 1 to 20 parts by weight with respect to 100 parts by weight of the plastic waste material. The plastic waste material was mixed and stirred by rotating the screw and blade of the mixing machine together with the modifier into a rotating blade type mixing machine, and melted by self-heating due to friction at that time to become a gel state. The plastic waste material is molded into a predetermined shape by moving to a mold and pressurizing .

  By adding the modifier according to the present invention to plastic waste, the mechanical strength of the molded product is improved. In addition, because it can be modified at low cost, it promotes material recycling of plastic waste. For this reason, a resource recycling society is realized, which helps to protect the global environment.

This modifier is obtained by mixing 2 to 3 parts by weight of a calcium carbonate fine powder having an average particle size of 0.1 to 0.5 μm with respect to 1 part by weight of a styrenic thermoplastic elastomer. The mixing ratio of the styrene thermoplastic elastomer and the calcium carbonate fine powder is desirable from the viewpoint of cost.
As shown in FIG. 1, the styrenic thermoplastic elastomer has a basic unit structure in which a polystyrene portion (hard segment) and a polybutadiene or polyethylene / polybutylene portion (soft segment) giving soft properties are copolymerized in a block shape. These are represented as SBS and SEBS, respectively. The end blocks of polystyrene aggregate with each other to form ultrafine particles, and these ultrafine particles are uniformly dispersed and play a role corresponding to the cross-linking points of the cross-linked rubber, and thus exhibit properties as an elastic body having a three-dimensional network structure. However, it melts when heated to 140-230 ° C. and exhibits fluidity as a thermoplastic resin. SEBS is obtained by hydrogenating the butadiene portion of SBS to eliminate unsaturated double bonds, and has excellent heat resistance and weather resistance.
In this embodiment, a styrene thermoplastic elastomer commercially available from Aron Kasei Co., Ltd. under the trade name “Elastomer AR-140” is used. Table 2 shows the basic physical properties of this styrenic thermoplastic elastomer.

Further, the fine powder is formed into amorphous particles having an average particle diameter of 0.1 to 0.5 μm and close to a spherical shape by mechanically ultrafine grinding calcium carbonate. Then, it is desirable to subject the fine powder to a re-aggregation preventing treatment with a metal soap.
When mixing the styrenic thermoplastic elastomer and the fine powder, the styrenic thermoplastic elastomer was put in a container heated to about 150 ° C. and the elastomer was melted, and then the fine powder was sufficiently kneaded little by little. The fine powder is uniformly dispersed in the elastomer by charging in about three times while confirming the above. In addition, it is not preferable to add fine powder at a time because uniform dispersion becomes difficult.

  On the other hand, plastic waste materials discharged from general households are crushed into chips of several centimeters to several millimeters by a crusher, and the above modifier is added to 0.01 to 0. It is added at a ratio of 2 parts by weight, and melted as shown below to form a molded product having a predetermined shape.

  Next, means for melt-molding the plastic waste material will be described. In order to melt-mold plastic waste materials, there are a method using a press molding device, a method using an extrusion molding device, and a method using an injection molding device. When using the press molding apparatus, first, the rotary blade type mixing machine shown in FIG. 2 is used. In this rotary blade type mixing machine 1, a spiral screw 5 and a plurality of blades 6 are provided on a rotary shaft 4 of a motor 3 penetrating through a chamber 2, and a discharge port 8 having a shutter 7 is provided at the lower portion of the chamber. The plastic waste material is put into the hopper 9 together with the modifier, and the screw 5 and the blade 6 are rotated at a high speed by driving the motor 3, and these are mixed and stirred, and the plastic waste material is vigorously stirred by the blade 6. The plastic waste material is melted and gelled by self-heating due to friction at the time of collision. The plastic waste material thus in a gel state is taken out by opening the shutter 7. FIG. 3 shows a press molding apparatus 10 composed of a lower mold 10a and an upper mold 10b. A plastic waste material 11 in a gel state is set in the lower mold, and the upper mold 10b is pressed down to prescribe the plastic waste material It can be formed into a shape.

Table 3 shows the effect of improving physical properties by adding a modifier (hereinafter referred to as modifier A) in which 2 parts by weight of the above calcium carbonate fine powder is mixed with 1 part by weight of a styrene thermoplastic elastomer to plastic waste. The results of testing are shown. Table 4 also shows improvement in physical properties by adding a modifier (hereinafter referred to as modifier B), which is a mixture of 3 parts by weight of the above calcium carbonate fine powder to 1 part by weight of a styrene-based thermoplastic elastomer. The result of having tested the effect is shown. In these tests, a square plate having a side length of 200 mm and a thickness of 5 mm was formed by the above press molding (with a surface pressure of 50 kg / cm ² ) and used as a test piece. In Table 3, (1) shows the result of measuring the mechanical strength of a test piece molded without adding any modifier. In Table 3, (2) to (6) show the mechanical strength of the test piece when the addition ratio of the modifier A is 3 to 20 parts by weight with respect to 100 parts by weight of the plastic waste material. Moreover, (7)-(11) in Table 4 shows the mechanical strength of the said test piece when the addition ratio of the modifier B is similarly 3-20 weight part.

  Thus, it was found that the modifier A and the modifier B can greatly improve the mechanical strength of the molded product by adding to the plastic waste, but the modifier A particularly improves the impact strength. It has been found that the effect of improving the tensile strength of the modifier B is remarkable, whereas the effect of improving the tensile strength is remarkable. For this reason, it is desirable to use properly the modifier A and the modifier B depending on the use of the molded product.

  In addition, about the addition ratio of these modifiers with respect to a plastic waste material, as shown in this Table 3, Table 4, it is a ratio of 1-20 weight part of modifiers with respect to 100 weight part of plastic waste materials. It is preferable to add, and when the addition ratio of the modifier is 1 part by weight or less, the mechanical strength cannot be improved. Moreover, even if the modifier is added in an amount of 20 parts by weight or more, only an increase in cost cannot be expected.

  Thus, the modifier according to the present invention is a mixture of a thermoplastic elastomer and a fine powder having a particle diameter of less than 1 μm (preferably an average particle diameter of 0.1 to 0.5 μm). Combined with the molten plastic waste material, combined with the thermoplastic elastomer having a three-dimensional network structure, bonds different types of plastics to prevent delamination. For this reason, the physical properties and mechanical strength of the molded product are remarkably improved. For this reason, the use is expanded to an article that requires impact resistance such as a transport pallet, and can be easily recycled to a product with high product value.

  Although this embodiment shows the process of molding by a press molding apparatus, the present invention can be molded not only by a press molding apparatus but also by an injection molding apparatus or an extrusion molding apparatus. FIG. 4 illustrates a screw-type extrusion molding device 15. A hopper 21 is provided on the upper surface of the base of a horizontally placed cylinder 20, and a screw 23 that is rotated by a motor 22 is provided in the cylinder 20. A die 25 in which a material extrusion passage continuing to the die 24 is formed is provided at the tip portion. Reference numeral 26 denotes a band heater provided on the outer periphery of the cylinder. Reference numeral 27 denotes a support roller provided in front of the die 24.

  In this extrusion molding apparatus, a plastic waste material is put into the hopper 21 together with the modifying agent, the plastic waste material is mixed and stirred by turning the screw 23, and the plastic waste material is melted by heating the band heater 26. Then, the plastic waste material in the gel state is extruded from the die 24, and the molded product 28 is supported by the support roller 27 and extracted. Thus, the method by extrusion improves productivity because melting and molding are continuously performed.

The schematic diagram which shows the basic unit structure of the thermoplastic elastomer which comprises the modifier concerning this invention. The longitudinal cross-sectional view of the rotary blade type mixing machine for enforcing the shaping | molding method which concerns on this invention. The longitudinal cross-sectional view of the press molding apparatus for enforcing the shaping | molding method concerning this invention. The longitudinal cross-sectional view of the extrusion molding apparatus for enforcing the shaping | molding method concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotating blade type mixing machine 10 Press molding apparatus 15 Screw type extrusion molding apparatus

Claims (2)

Plastic waste is made up of many types of plastic containers and plastic packaging materials that are discharged as garbage from ordinary households. The main component is polypropylene and polyethylene, and polystyrene is contained in a proportion lower than these two main components. These three components account for 89% by weight or more. On the other hand, the modifier is an average particle based on 1 part by weight of styrene thermoplastic elastomer copolymerized with polystyrene and polybutadiene. It is formed by mixing 2 to 3 parts by weight of fine powder made of calcium carbonate having a diameter of 0.1 to 0.5 μm, and 100 parts by weight of the plastic waste is 1 to 20 parts by weight of the modifier. The plastic waste material is added to the rotary blade type mixing machine together with the modifier to add the screw and blade of the mixing machine. The plastic waste was mixed with stirring by causing high speed rotation, and characterized in that formed into a predetermined shape by pressing by moving the plastic waste which has become a gel state melted to the mold by self-heating due to friction at that time Recycled molding method for plastic waste. Plastic waste is made up of many types of plastic containers and plastic packaging materials that are discharged as garbage from ordinary households. The main component is polypropylene and polyethylene, and polystyrene is contained in a proportion lower than these two main components. These three components account for 89% (by weight) or more, while the modifier is a styrene thermoplastic elastomer copolymerized with polystyrene and polyethylene / polybutylene, based on 1 part by weight. It is formed by mixing 2 to 3 parts by weight of fine powder made of calcium carbonate having an average particle size of 0.1 to 0.5 μm, and the modifier is added to 1 to 20 parts by weight with respect to 100 parts by weight of the plastic waste material. The plastic waste material is added to the rotary blade type mixing machine together with the modifier, and the mixing machine is screened. The plastic waste material is mixed and stirred by rotating the blade at high speed, and the plastic waste material that has been melted by self-heating due to friction at that time and turned into a gel state is moved to a mold and pressed into a predetermined shape. recycling molding method of plastic waste which was characterized by.

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