KR20130001566A - Method of foaming recycled crosslinked polymeric resins via supercritical decrosslinking reaction and form materials manufactured by the same - Google Patents

Abstract

PURPOSE: A manufacturing method of a foam product is provided to manufacture a foam product with uniform foam cells from waste crosslinked plastics. CONSTITUTION: A manufacturing method of a foam product comprises: a step of obtaining a recycled polyolefin resin by the supercritical decrosslinking reaction of waste plastics; a step of mixing 100 parts by weight of a base resin which comprises the recycled polyolefin resin, 1-10 parts by weight of a foaming agent, and 0.2-5 parts by weight of a crosslinking agent; and a step of foaming the mixture at 170 deg. C or more. The waste crosslinked plastic is a crosslinked polyolefin-based copolymer. The base resin comprises 10-100 weight% of the recycled polyolefin resin.

Description

Method of foaming recycled crosslinked polymeric resins via supercritical decrosslinking reaction and form materials manufactured by the same}

The present invention relates to a method for producing a foamed molding product using a recycled polyolefin resin obtained by a supercritical decrosslinking reaction, wherein the recycled polyolefin resin obtained by a supercritical decrosslinking reaction as a governing resin is 10 to 100 based on the total weight of the control resin. It relates to a process for producing a foamed molding from the weight percent, and to a foamed molding produced.

The present invention relates to a supercritical decrosslinking reaction of waste crosslinked plastics to obtain a recycled polyolefin resin and to a method for producing a foamed molding using the same.

Foams of olefin copolymers such as polyethylene and polypropylene, which are polyolefin resins, have excellent elasticity, flexibility, wear resistance, chemical resistance, and electrical insulation, and are widely used in building materials, automotive interior materials, electric and electronic component materials, and general merchandise.

In addition, crosslinked plastics having a polymer chain structure of a network type cross-linked therein from the crosslinking reaction of polyolefins occupy a large portion in various fields of our lives such as small ship materials, structural materials for automobiles and aerospace, and sporting goods. It is used. However, these crosslinked plastics have the properties of insoluble and infusible due to the crosslinked structured polymer chains. For this reason, when the waste crosslinked plastic is to be recycled, a low molecular weight wax produced by high-temperature pyrolysis or simply crushed and pulverized is partially used, and an appropriate recycling method has not been developed yet.

On the other hand, as a method for recycling the waste crosslinked plastics, since the waste crosslinked plastics are not self-molding, a method of forming by adding a small amount of plastic having a moldability is mainly used. However, even if a part of the plastic having a formability is used, when trying to manufacture a foam molding from the waste cross-linked plastic, the problem that the uniform foaming is not possible due to the cross-linking structure formed in the waste cross-linked plastic still is not solved. .

Unrecycled waste crosslinked plastics create many environmental problems. From this point of view, the demand for the development of a new technology for recycling the waste crosslinked plastic, which is mostly incinerated, is an urgent task to be prevented from environmental pollution.

In general, supercritical fluids are materials in the supercritical region with no boundary between gas and liquid above the critical point of hot and high pressure in the vapor pressure curves of temperature and pressure. Low surface tension, low viscosity, high diffusion rate and liquid It is known as a reaction medium having all the advantages such as excellent solubility. In particular, as a supercritical fluid, water and methanol cut the polymer chain at a high temperature and high pressure state above its critical point (water; 374.22 ° C 22MPa, methanol; 240 ° C 7.93MPa), and therefore, JP-A-2005-281429, 2004- 161983, 2003-96233, 2001-253968, 2001-98107), European Patent 0897783A2, Korean Patent 10-0733941, 10-0728087 and is used in the recycling process of the waste crosslinked plastic.

Recently, in particular, as a part of the low carbon green growth project, a technique of using waste crosslinked plastics for the production of foam moldings has emerged as a means for implementing a resource recycling structure. However, the foam molding process is very sensitive to the type, amount and reaction conditions of the reactants. Therefore, it is not easily conceivable to use recycled waste resin in the manufacturing process of foam moldings. Moreover, the use of waste crosslinked plastics in the manufacture of foam moldings has not been attempted to date.

Therefore, the present inventors have studied a method for recycling waste crosslinked plastics and using them in the manufacture of foam moldings.

It is an object of the present invention to make it possible to use waste crosslinked plastic, which is difficult to recycle, in the production of foam moldings.

To this end, the present invention is to provide a method for obtaining a recycled polyolefin resin having a molecular weight close to the original polyolefin resin before the crosslinking reaction by a supercritical decrosslinking reaction process from the waste crosslinked plastics, and using it in the foam molding production process.

The present invention comprises the steps of supercritical decrosslinking reaction of the cross-linked plastics to obtain a recycled polyolefin resin; Mixing 100 parts by weight of the governing resin including the recycled polyolefin resin, 1 to 10 parts by weight of the blowing agent and 0.2 to 5 parts by weight of the crosslinking agent; And foaming the mixture at a temperature of 170 ° C. or higher.

Preferably, the waste crosslinked plastic is a crosslinked polyolefin-based copolymer.

Preferably, the supercritical decrosslinking reaction of the waste crosslinked plastic is carried out in a reaction medium of water, ethanol or methanol under a reaction temperature in the range of 360 to 400 ° C. and a reaction pressure in the range of 5 to 30 MPa.

Preferably, the governing resin comprises recycled polyolefin resin in the range of 10 to 100% by weight.

Preferably, the blowing agent is azodicarbonamide.

Preferably, the crosslinker is dicumylperoxide.

The present invention also provides a foamed molded article produced from the above production method.

According to the present invention, a foamed molded article including a uniform foamed cell can be manufactured from waste crosslinked plastic that is difficult to recycle.

Accordingly, the present invention is not only recycled, but also incinerated, environmentally friendly disposal of cross-linked plastics causing various environmental problems, as well as the production of industrially useful materials, such as foam molding of polyolefin resin, thereby realizing a resource cyclic structure To bring.

1 is a cross-sectional SEM photograph of the foam molding prepared in Example 1. FIG.
Figure 2 is a cross-sectional SEM photograph of the foam molding prepared in Example 4.

The present invention relates to a method of producing a recycled polyethylene resin by obtaining a recycled polyethylene resin by removing the degree of crosslinking of the waste crosslinked plastic by a supercritical decrosslinking reaction.

Specifically, the present invention comprises the steps of supercritical decrosslinking the waste crosslinked plastics to obtain a recycled polyolefin resin; Mixing 100 parts by weight of the governing resin including the recycled polyolefin resin, 1 to 10 parts by weight of the blowing agent and 0.2 to 5 parts by weight of the crosslinking agent; And foaming the mixture at a temperature of 170 ° C. or higher, and to a foam molding produced therefrom.

Decrosslinking Reaction of Waste Crosslinked Plastics

The said waste crosslinked plastics are obtained by the crosslinking reaction of normal olefin type copolymers, such as a crosslinked polyethylene and a crosslinked polypropylene, for example. In order to obtain a recycled polyolefin resin suitable for use as a dominant resin of a foam molding from these waste crosslinked plastics, in the present invention, a supercritical fluid is used as a reaction solvent to undergo a decrosslinking reaction. As the "supercritical fluid", water, ethanol or methanol can be used.

The supercritical decrosslinking reaction of the closed crosslinked plastics is preferably carried out at "supercritical fluid conditions" at reaction temperatures ranging from 360 to 400 and reaction pressures ranging from 5 to 30 MPa. In addition, the reaction time can be progressed from 1 minute to 10 minutes.

The degree of crosslinking of the recycled polyolefin resin obtained from the decrosslinking reaction of the waste crosslinked plastic is controlled by reaction conditions such as reaction temperature, pressure and time. In the present invention, the reaction conditions of the decrosslinking reaction are adjusted so that a recycled polyolefin resin having a crosslinking degree in the range of 0 to 15% is obtained for use in preparing the foamed molding.

On the other hand, most preferably it is to reduce the crosslinking degree of the waste crosslinked plastic to 0%. By this reaction, a recycled polyolefin resin having a molecular weight close to that of the original polyolefin resin before the crosslinking reaction can be obtained.

Manufacture of foam moldings

The present invention provides a method for producing a foamed molded article characterized in that the recycled polyolefin resin obtained above is used in a dominant resin for producing a foamed molded article.

The recycled polyolefin resin may be used alone or as a dominant resin of a foam molding, or may be used by mixing with a polyolefin of a new material before the crosslinking reaction.

At this time, preferably 10 to 100% by weight of the recycled polyolefin resin based on the total weight of the governing resin can be used. The amount of recycled polyolefin resin used in the control resin may be adjusted according to the degree of crosslinking.

Next, 1 to 10 parts by weight of the blowing agent and 0.2 to 5 parts by weight of the crosslinking agent are added to 100 parts by weight of the resin, followed by mixing using a mixer, a compressor, or a kneader.

The blowing agent is a compound for foaming the control resin, 1 to 10 parts by weight based on 100 parts by weight of the control resin to uniformly foam the control resin including the recycled polyolefin resin. If the blowing agent is used in an amount less than the above range does not occur uniform foaming over the entire amount of the governing resin, when used in an amount exceeding the above range may cause unstable foaming due to excessive foaming in a short time and having an appropriate size There is a problem that the foam cell is not formed.

In the present invention, azodicarbonamide is preferably used as the blowing agent, but is not limited thereto.

The crosslinking agent is preferably a peroxide-based radical initiation reaction crosslinking agent having excellent crosslinking properties of polyolefin, and more preferably a dicumyl peroxide crosslinking agent.

Finally, the mixed mixture is foamed at 170 ° C. or higher to complete the preparation of the foam molding of the present invention.

In particular, the recycled polyolefin resin prepared by the decrosslinking reaction in the present invention is characterized by having a molecular weight close to the original polyolefin resin level before the crosslinking reaction. Therefore, according to the present invention, even when only the recycled polyolefin resin is used without the addition of a new polyolefin resin as the governing resin in the production of the foam molding, it is possible to manufacture the foam molding having excellent physical properties.

Hereinafter, examples will be given in order to describe the present invention in detail. However, it should not be understood that the present invention is limited thereto.

Example 1

Closed bridge  Plastic Decrosslinking  reaction

In the continuous process supercritical extruder with a crosslinking degree of 65% polyethylene resin (D) of 40 mm and L / D = 36 as waste crosslinked plastic, using methanol as the reaction solvent, a reaction pressure of 8 MPa and 370 ° C. The crosslinking reaction was carried out by standing at the reaction temperature for 2 minutes to obtain a recycled polyolefin resin.

Manufacture of foam moldings

100 parts by weight of the recycled polyolefin resin, 2 parts by weight of azodicarbonamide blowing agent, 0.2 parts by weight of dicumylperoxide crosslinking agent and 1.6 parts by weight of ZnO were added as a dominant resin, and these were mixed at 130 ° C. using a kneader. Next, the mixture was foamed under high pressure at 170 ° C. and 14 MPa to prepare a foam molding.

[Example 2]

A foamed molding was prepared in the same manner as in Example 1 except that the content of the crosslinking agent was 0.6 parts by weight in the foam molding of Example 1.

[Example 3]

A foamed molding was prepared in the same manner as in Example 1, except that the content of the crosslinking agent was used in an amount of 1 part by weight in the foam molding of Example 1.

Example 4

In Example 1, except that 50 parts by weight of recycled polyolefin resin and 50 parts by weight of polyolefin (LDPE 5316, Hanwha Chemical) were used instead of 100 parts by weight of recycled polyolefin resin as the dominant resin in the manufacturing process of the foam molding. In the same manner, foam moldings were prepared.

[Example 5]

A foamed molding was prepared in the same manner as in Example 4, except that the content of the crosslinking agent was 0.6 parts by weight in the foam molding of Example 4.

[Example 6]

A foam molding was prepared in the same manner as in Example 4, except that the crosslinking agent was used in an amount of 1 part by weight in the foam molding of Example 4.

[Property evaluation]

Visual observation of foaming rate and cell shape

The foaming rate was calculated by measuring the density of the foamed moldings prepared in Examples 1-6. Also, the foam cell shape was visually observed. The results are shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Control 100 parts by weight of recycled polyolefin resin 50 parts by weight of recycled polyolefin resin + 50 parts by weight of new polyolefin Crosslinking agent content (parts by weight) 0.2 0.6 One 0.2 0.6 One Foaming rate (%) 750 650 450 650 600 500 Cell geometry Good Good Good Good Good Good

SEM scanning

On the other hand, the cross-section of each of the molded foam prepared in Examples 1 and 4 by scanning electron microscopy (SEM). The results are shown in FIGS. 1 and 2.

According to Table 1, when the crosslinked reaction of the waste crosslinked plastics by the supercritical process according to the present invention, a recycled polyolefin resin was obtained, and a foamed molded article was prepared by using it alone or mixed with a new polyolefin resin as a dominant resin. , It can be confirmed that the foamed molded product produced has a good foaming rate and a shape of the foaming cell. In addition, it can be seen in Figure 1 and 2 the foam cell shape uniformly formed in the foam molding.

As described above, the present invention has been described in detail, and it will be apparent to those skilled in the art that these specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (7)

Supercritical decrosslinking reaction of the waste crosslinked plastics to obtain a recycled polyolefin resin;
Mixing 100 parts by weight of the governing resin including the recycled polyolefin resin, 1 to 10 parts by weight of the blowing agent and 0.2 to 5 parts by weight of the crosslinking agent; And
Foaming the mixture at a temperature of at least 170 ° C. In claim 1,
The waste crosslinked plastic is a cross-linked polyolefin-based copolymer production method characterized in that In claim 1,
The supercritical decrosslinking reaction of the waste crosslinked plastics is carried out in a reaction medium of water, ethanol or methanol, under a reaction temperature in the range of 360 to 400 ° C. and a reaction pressure in the range of 5 to 30 MPa. In claim 1,
The control resin manufacturing method of the foamed molded article characterized in that it comprises a recycled polyolefin resin in the range of 10 to 100% by weight In claim 1,
The blowing agent is a method for producing a foamed molding, characterized in that azodicarbonamide In claim 1,
The crosslinking agent is a manufacturing method of the foamed molding, characterized in that dicumyl peroxide A foam molding formed from the process according to any one of claims 1 to 6.

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