JPH05261735A - Recovery of polyvinylidene chloride resin from laminated molded article - Google Patents

Abstract

PURPOSE:To enhance the yield of a product and eliminate the incineration problem of waste by roughly and finely grinding waste under a specific grinding condition and treating secondary ground matter with a surfactant. CONSTITUTION:A laminated molded article containing a polyvinylidene chloride resin is roughly ground by a grinding blade whose shearing velocity is 1X10<3>-4X10<4>sec<-1>. Next, the obtained primary ground matter is finely ground by a grinding blade whose shearing velocity is 1X10<4>-3X10<5>sec<-1>. The obtained secondary ground matter is treated in an aqueous medium containing a surfactant to settle and separate the polyvinylidene chloride resin. By this method, the expensive polyvinylidene chloride resin can be simply separated and recovered from the laminated molded article in a high yield of 90% or more. Therefore, the waste laminated molded article can be reutilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering polyvinylidene chloride resin from a laminated molded product.

[0002]

2. Description of the Related Art Polyvinylidene chloride resins have excellent oxygen barrier properties, and therefore, polyvinylidene chloride resins are combined with other plastic materials such as polyolefins and polyethylene terephthalates to form a laminated structure. However, it is often used as a packaging film, a sheet-like material, a container, or the like. Conventionally, it has been practiced to collect and use the resin component of a laminated molded product, but the polyvinylidene chloride resin is expensive and easily decomposed by heat, causing discoloration or Since black foreign matter is likely to occur, it is desired to separate and collect the polyvinylidene chloride resin in the laminated molded product using the polyvinylidene chloride resin. Conventionally, as a method of recovering a resin component from a laminated molded article, (1) a method of recovering each resin layer in a film state from a laminated film material, for example, by heating a laminated sheet or film with a heating roll or the like. , A method for separating an oxygen gas barrier resin layer from another resin layer (Japanese Patent Laid-Open No. 2-13
1907) or a method in which each resin layer is peeled from the laminated film by applying a shearing force in heated water or air (JP-A-63-202409), and (2) a laminated molded article. After crushing, a method of recovering each resin, for example, a method of heat shrinking a used multilayer plastic bottle, mechanically crushing, and then separating a plurality of plastic materials by a specific gravity separation method (JP-A-1-14)
No. 8517), a method of pulverizing a laminated molded product under heating using residual heat at the time of production, and then collecting by resin by a specific gravity separation method (Japanese Patent Laid-Open No. 55-95525), heating the laminated molded product. After crushing with a shear crusher in the state of being kept, it is separated by the difference in specific gravity (Japanese Patent Laid-Open No. 53-79975).
Etc. are known.

[0003]

In recent years, a technique has been developed in order to improve the adhesive strength between the layers of the laminate from the viewpoint of improving the performance of the laminate molded product, and as a result, a polyvinylidene chloride resin layer is contained. It has become increasingly difficult to separate and collect polyvinylidene chloride-based resins from laminated moldings. None of the above-mentioned conventional methods is sufficient as a method for separating a polyvinylidene chloride resin from a laminated molded product containing a polyvinylidene chloride resin layer. For example, the method of recovering each resin layer in the state of a film from a laminated film material can be applied only to a laminated molded article that can be peeled into a film shape, and it is necessary to pulverize it for reuse. Further, in the method of crushing the laminated molded product and separating and recovering each resin, clogging of the screen occurs during crushing, or when it is applied to a laminated molded product containing a polyvinylidene chloride resin layer,
There is a problem that the polyvinylidene chloride-based resin remains in the state of being attached to the pulverized product and cannot be separated. Therefore, it has heretofore been considered that it is impossible to efficiently separate and collect the polyvinylidene chloride resin from the laminated molded product containing the polyvinylidene chloride resin layer. The present invention is
This is done in view of the above-mentioned actual situation in the conventional technique. Therefore, an object of the present invention is to provide a method for recovering a polyvinylidene chloride resin that can efficiently separate a polyvinylidene chloride resin from a laminated molding containing a polyvinylidene chloride resin layer.

[0004]

A method for recovering a polyvinylidene chloride resin from a laminated molded product according to the present invention is a laminated molded product containing a polyvinylidene chloride resin layer having a crushing blade shear rate of 1 × 10 ³ to. Primary crushing step of roughly crushing under the condition of 4 × 10 ⁴ sec ⁻¹ , and secondary crushing of the obtained primary crushed product under the condition that the shearing speed of the crushing blade is 1 × 10 ^{4 to} 3 × 10 ⁵ sec ^−1. The method is characterized by including a pulverization step, a surfactant treatment step of treating the obtained secondary pulverized product in a surfactant-containing aqueous medium, and a separation and recovery step of precipitating and separating the polyvinylidene chloride resin.

The present invention will be described in detail below. As the laminated molded product to be treated in the present invention, any form such as a film-shaped product, a sheet-shaped product, and a thick parison can be used, and as a layer constitution, a polyvinylidene chloride resin layer is included, and two or more layers are included. As long as it is a laminated molded product having the above layer structure, any one can be applied. Examples of the resin constituting the polyvinylidene chloride-based resin layer in the laminated molded product include polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, vinylidene chloride-acrylic acid ester copolymer, and the like. Examples of the resin constituting the resin layer laminated with the polyvinylidene chloride resin layer include polyethylene, polypropylene, polybutene- (1), poly-4-methylpentene-
(1), polyolefins such as polyisobutylene, α-olefin copolymers such as ethylene-propylene copolymer, olefin-vinyl acetate copolymers such as ethylene-vinyl acetate copolymer, olefin-ethyl acrylate copolymer , Ionomers and the like.

(Primary crushing step) In order to recover the polyvinylidene chloride resin from the above-mentioned laminated molded article, the laminated molded article is first roughly crushed in the primary crushing step. In the primary crushing process, a crusher having a crushing blade that rotates at a high speed is used, but the shearing speed of the crushing blade is 1 × 10 ³ to 4 × 1.
It is necessary to be 0 ⁴ sec ^-1 , preferably 1
It is in the range of x10 ⁴ to 4x10 ⁴ sec ^-1 . When the shearing speed of the crushing blade becomes higher than 4 × 10 ⁴ sec ⁻¹ during coarse crushing, the crushed material is welded, gelled, decomposed, and the screen is clogged to hinder the crushing ability. Like On the other hand, the shear rate of the crushing blade is 1 × 10
^If it is smaller than ³ sec ^-1 , the laminated molded product will not be crushed and the crushing ability will be reduced, which will hinder the separation and collection. Further, it is desirable to perform the coarse pulverization so that the outlet temperature of the pulverizer does not rise above 50 ° C. In the present invention,
The primary pulverized product obtained by coarse pulverization is 2 to 10 mmφ
It is desirable to have a size that can pass through the screen.

When the laminated molded product is formed of a stretched film, the primary crushed product is subjected to the secondary crushing process,
Hot water treatment is desirable. The hot water treatment is carried out by immersing the primary pulverized product in hot water of 90 to 100 ° C. for 3 minutes or more, whereby the difference in shrinkage ratio of each resin constituting the laminated molded product causes Strains and cracks in the ground occur, making it easy to separate.

(Secondary pulverizing step) The primary pulverized product or the hot water-treated product obtained as described above is then finely pulverized in the secondary pulverizing step. In the secondary crushing process,
A crusher with a crushing blade that rotates at high speed is used,
The shear rate of the crushing blade needs to be 1 × 10 ^{4 to} 3 × 10 ⁵ sec ⁻¹ , and preferably 1 × 10 ^{5 to} 3 ×.
The range is 10 ⁵ sec ⁻¹ . When the shearing speed of the crushing blade becomes greater than 3 × 10 ⁵ sec ⁻¹ during fine crushing,
Similar to the case of the primary crushing process, film welding, gelation, decomposition, etc. occur, and the screen becomes clogged, which impairs the crushing ability. If the shear rate of the crushing blade is less than 1 × 10 ⁴ sec ^-1 , the primary crushed product will not be crushed and the crushing ability will decrease. The fine pulverization in the secondary pulverization step may be performed in air, but may be performed in water. Further, it is desirable that the secondary pulverized product obtained by fine pulverization is performed so that the outlet temperature of the pulverizer does not rise above 50 ° C. Secondary crush is 1
It is desirable to carry out so that the particle diameter is less than or equal to mmφ, preferably less than or equal to 0.5 mmφ.

(Surfactant treatment step) The obtained secondary pulverized product is then treated in a surfactant-containing aqueous medium. The treatment with the surfactant can be performed by, for example, an apparatus equipped with a stirrer. That is, an aqueous medium containing a surfactant may be placed in the separation / collection device, the secondary pulverized product may be placed therein, and the mixture may be slowly stirred by a stirrer. The surfactant to be used at that time is not particularly limited, but may be one having a surface tension of 50 dyne / cm or less, preferably 35 dyne / cm or less. For example, anionic activators such as higher fatty acid alkali salts, linear alkylbenzene sulfonate alkali salts, alkyl sulfate alkali salts, alkyl sulfonate alkali salts, etc., nonionic activity such as polyethylene glycol alkyl ethers, polyethylene glycol fatty acid esters, sorbitan fatty acid esters, etc. Agents etc. can be used. In the present invention, a water-soluble medium such as alcohol or acetone may be present in the aqueous medium in a small amount, but it is preferably not present in order to improve the separation efficiency. (Separation and Recovery Step) The secondary pulverized product treated with the surfactant as described above is then separated and recovered due to the difference in specific gravity. This separation / recovery step may be carried out continuously in the apparatus treated with the surfactant, or may be carried out by moving to another separation / collection apparatus. By leaving the secondary pulverized product treated as described above, the fine particles of polyvinylidene chloride resin having a high specific gravity settle, while the resin particles having a low specific gravity such as polyolefin float. Therefore, after the separation of the two is completed, the suspended matter in the supernatant is
For example, the fine particles of polyvinylidene chloride which have been removed by suction and the like may be collected.

[0010]

The operation of the present invention will be described with reference to the drawings. Figure 1
[Fig. 3] is a schematic view for explaining a state in which a laminated molded product is crushed. For example, a case of a laminated film having a three-layer structure composed of a polyolefin film such as polyethylene, a polyvinylidene chloride film, and a polyolefin film such as polypropylene will be described as an example. First, in the primary crushing step, the laminated film is roughly crushed to form a primary crushed product composed of the polyolefin film 1, the polyvinylidene chloride film 2 and the polyolefin film 3 (FIG. 1 (a)). The primary crushing process is effective in reducing shearing heat during fine crushing in the secondary crushing process, shortening the residence time in the crusher, and preventing gelation, decomposition, and welding of the secondary crushed product. .. Further, when the coarse pulverization is performed in the primary pulverization step, the primary pulverized product can be stably supplied to the pulverizer in the secondary pulverization step, and the fine pulverization can be efficiently performed. The primary pulverized product is subjected to hot water treatment as desired, but this causes shrinkage of the primary pulverized product, which causes ground cracks on the surface of the polyolefin film due to the difference in shrinkage ratio, and the primary pulverized product is easily separated (Fig. 1). (B)). The primary pulverized product is then finely pulverized in the secondary pulverization process. In the secondary pulverization process, not only shearing force but also mechanical effect of air or water due to high speed rotation, that is, cavitation action due to vortex flow is added. Peeling between the polyolefin layer and the polyvinylidene chloride layer occurs at an accelerated rate, and the polyvinylidene chloride becomes fine particles (FIG. 1 (c)). In the obtained secondary crushed product, fine-grained polyvinylidene chloride particles 2a are attached to the surfaces of the crushed polyolefin crushed pieces 1a and 3a having a relatively large size. Next, the secondary ground product is treated with a surfactant. When the secondary pulverized product is put into water, the polyvinylidene chloride particles are retained in the state of being adhered to the surface of the polyolefin pulverized piece, and the polyvinylidene chloride particle is difficult to separate from the surface of the polyolefin pulverized piece, but the surface activity is reduced. By performing the treatment with the agent, the polyvinylidene chloride particles can be separated from the ground polyolefin particles. Polyvinylidene chloride generally has a specific gravity of about 1.7, while polyolefins such as polyethylene and polypropylene have a specific gravity of about 0.87 to 0.97, so that the polyvinylidene chloride separated in the secondary pulverized product is The particles 2a settle, while the polyolefin crushed pieces 1a and 3a float. Therefore, it becomes possible to separate and collect the polyvinylidene chloride particles due to the difference in specific gravity.

[0011]

【Example】

Example 1 An ethylene-vinyl acetate copolymer film having a thickness of 13 μm, a polyvinylidene chloride film having a thickness of 8 μm, and an ionomer (ethylene-methacrylic acid copolymer) film having a thickness of 31 μm were respectively used as an ethylene-ethyl acrylate copolymer. Polyvinylidene chloride was recovered by using a laminated film having a polyvinylidene chloride content of 23% by weight, which was laminated via an adhesive layer having a thickness of 1 μm. First, a primary crusher (UG03-223-360XRFX, provided with a 3 mmφ screen was used for the above laminated film.
Coarse crushed by Horai Co., Ltd. As the crushing condition, the clearance between the fixed blade and the rotary blade: 0.3 mm,
The shear rate of the rotary blade was set to 1.46 × 10 ⁴ sec ^−1, and the conditions were such that the temperature inside the duct of the primary pulverizer was maintained at 50 ° C. or lower. The primary pulverized product that passed through the 3 mmφ screen was then immersed in hot water at 95 ° C. for 3 minutes and then dried. Next, the hot water treated product is a secondary pulverizer (mesh mill HA-2542-3) provided with a 0.5 mmφ screen.
0, manufactured by Horai Co., Ltd., and pulverized.
As the crushing condition, the clearance between the fixed blade and the rotary blade: 0.
13 to 0.15 mm, and the shear rate of the rotary blade is 2 × 10
The temperature in the duct of the secondary crusher is set to ⁵ sec ^-1
It was carried out under the condition that the temperature was kept at 5 ° C or lower and the room temperature was kept at 20 ° C or lower. The crushing capacity was 27 kg / hr. 0.
The average particle size of the polyvinylidene chloride particles in the secondary pulverized product that passed through the 5 mmφ screen was about 0.25 mm, and the average particle size of the polyolefin particles was 0.40 mm. Next, 3 kg of the obtained secondary pulverized product was added to pure water 160
The mixture was placed in a separation / collection device equipped with a stirrer containing 1 liter, and 64 cc of sodium alkylbenzenesulfonate was added as a surfactant, followed by stirring for 3 minutes. After the stirring was stopped, the separated suspended matter was sucked and removed, the precipitate was extracted from the lower side, dehydrated by a centrifuge, and then dried to recover the desired polyvinylidene chloride in the form of fine particles. The recovery rate of polyvinylidene chloride was 92.5%. The recovery rate is 5% fuming nitric acid containing 1.5 g of silver nitrate.
0.2 g of the recovered product was placed in ml, and the mixture was heated and decomposed at 300 ° C. for 10 hours in an oven, and the formed precipitate was filtered, dried, and measured for chlorine by the Carius method.

Example 2 Polyvinylidene chloride was recovered in the same manner as in Example 1 except that the hot water treatment after the coarse pulverization by the primary pulverizer was omitted. In that case, the recovery rate is 90.1
%Met.

Comparative Example 1 The same procedure as in Example 1 was carried out except that no surfactant was added in separating the secondary ground product. In that case, the polyvinylidene chloride hardly precipitated, and the recovery rate was only 3.0%. Comparative Example 2 The same procedure as in Example 1 was carried out except that the hot water treatment after the coarse pulverization by the primary pulverizer was omitted and the surfactant was not added when separating the secondary pulverized product. In that case, the polyvinylidene chloride hardly sedimented and the recovery rate was only 1.0%. Comparative Example 3 In Example 1, when hot water treatment was performed without performing primary pulverization and then secondary pulverization was performed, the object to be pulverized gelled,
It was not possible to decompose to obtain a pulverized product that passed through a 0.5 mmφ screen. Comparative Example 4 The same process as in Example 1 was carried out except that the secondary pulverization was not performed in Example 1. The recovery rate of polyvinylidene chloride was 5.0%. Comparative Example 5 In Example 1, the secondary pulverization was carried out at a shear rate of the rotary blade of 7.
When the same treatment was carried out except that the screen was set to 2 × 10 ⁵ sec ⁻¹ and a 1.3 mmφ screen was used, gelation and welding of the secondary pulverized product occurred, and the pulverization processing capacity was 10.3 kg.
/ Hr.

Example 3 Polyethylene film, polyvinylidene chloride film,
A polyvinylidene chloride was recovered by using a laminated parison having a three-layer structure of an ionomer (ethylene-methacrylic acid copolymer) film and having a thickness of 620 μm and containing 20% by weight of polyvinylidene chloride. First, the above laminated parison was roughly crushed under the same crushing conditions as in Example 1 except that a 5 mmφ screen was used. The primary pulverized product that passed through the 5 mmφ screen was supplied to the secondary pulverizer and finely pulverized under the same pulverization conditions as in Example 1 to obtain a secondary pulverized product. When treated with a surfactant in the same manner as in Example 1 and separated, the recovery of polyvinylidene chloride was 96.0%.

[0015]

As described above, according to the present invention, coarse pulverization and fine pulverization are performed under the specific pulverization conditions as described above, and the secondary pulverized product is treated with a surfactant. The vinylidene resin can be easily separated and recovered in a high yield of 90% or more. Therefore, since the discarded laminated molded product can be reused, the product yield is improved, the problem of incineration of the waste is solved, and it is also beneficial in terms of environmental problems.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining states in primary pulverization, hot water treatment, and secondary pulverization in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Polyolefin film 1a ... Polyolefin crushed piece 2 ... Polyvinylidene chloride film 2a ... Polyvinylidene chloride particles 3 ... Polyolefin film 3a ... Polyolefin crushed piece

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Claims (3)

[Claims] 1. A laminated molding containing a polyvinylidene chloride resin layer having a crushing blade with a shear rate of 1 × 10 ³ to 4 × 10 ⁴ s.
Primary crushing step of coarsely crushing under the condition of ec ⁻¹ , and the obtained primary crushed product has a shear rate of a crushing blade of 1 × 10 ^{4 to} 3 × 10 ⁵ s.
a secondary pulverizing step of finely pulverizing under the condition of ec ⁻¹ , a surfactant treating step of treating the obtained secondary pulverized product in a surfactant-containing aqueous medium, and precipitating a polyvinylidene chloride resin.
A method for recovering a polyvinylidene chloride resin from a laminated molded article, which comprises a separation and recovery step of separating. 2. The method according to claim 1, wherein the primary pulverized product passes through a screen of 2 to 10 mmφ and the secondary pulverized product passes through a screen of 1 mmφ or less. 3. The method according to claim 1, wherein the primary pulverized product is treated with hot water and then finely pulverized.