JP3709014B2 - Method for recovering monomer from waste acrylic resin - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for recovering a monomer from a waste material of an acrylic resin.
[0002]
[Prior art]
In recent years, there has been a strong demand for recycling plastic waste from the standpoints of global environmental protection and resource saving. Various methods are used to recycle plastic waste, but the most effective method is dry distillation, that is, in the absence of oxygen, the plastic is thermally decomposed and reduced to low molecular weight monomers for reuse. To be done.
[0003]
Acrylic resins mainly composed of methyl methacrylate can recover the raw material monomers constituting the resin by dry distillation in a high yield, and conventionally monomer recovery by dry distillation has been performed.
[0004]
However, plastic products manufactured using monomers recovered from acrylic resin waste by conventional methods have a slight yellowish color, so they are suitable for products in fields where extremely high transparency is required. It was difficult to use the recovered monomer.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to recover the monomer which improves the drawbacks of the above prior art and enables the production of a highly transparent plastic product when recovering the monomer from the waste acrylic resin mainly composed of methyl methacrylate. It is to provide a method.
[0006]
[Means for Solving the Problems]
The above-mentioned object of the present invention is to thermally decompose acrylic resin waste into a gaseous state by dry distillation, then liquefy the gaseous thermally decomposed product, and then recover the liquefied thermally decomposed product as a monomer by distillation purification. In addition, when adding polyvalent amine to the liquefied thermal decomposition product in advance, 5 to 30% by weight of water is added and mixed thoroughly, and then the aqueous layer is separated and removed, and the oil layer is distilled and purified. This is achieved by a method of recovering monomers from waste acrylic resin.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The acrylic resin waste material used in the present invention is composed of a methyl methacrylate homopolymer or a copolymer of 80% by weight or more of methyl methacrylate and 20% by weight or less of alkyl methacrylate or alkyl acrylate. The thing to which the physical property improving agent or the coloring agent was added is also included.
[0008]
The acrylic resin waste material as a raw material of the present invention is pulverized to an appropriate size as necessary before the carbonization treatment. When a masking material such as protective paper or protective film is attached to the acrylic resin waste material, in the present invention, there is no problem even if the carbonization treatment is performed as it is. Monomers recovered by the prior art not according to the present invention exhibit a yellowish color particularly when subjected to dry distillation treatment in the presence of a masking material and impair transparency.
[0009]
In general, dry distillation is performed by charging the above-mentioned raw material into a kettle and heating to a temperature of 350 to 500 ° C. in an inert gas atmosphere in the absence of substantially oxygen as necessary. The gaseous thermal decomposition product is taken out from the kettle and then condensed and liquefied by a heat exchanger type cooler or the like.
[0010]
Then, on the liquefied thermal decomposition is carried out in advance added pressure Shi distillation purification polyamine. The amount of polyamine added is preferably in the range of 10 to 10,000 ppm. Examples of the polyvalent amine used include ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine and the like. Among these, ethylenediamine, diethylenetriamine and triethylenetetramine are preferable. If the amount of polyvalent amine added is too small, sufficient effects cannot be obtained. On the other hand, when the amount is too large, it is difficult to separate and remove from the monomer during distillation purification.
[0011]
As a method of adding a polyvalent amine to the liquefied thermal decomposition product, it is added before distillation . That is, it is added into the distillation column. Preferably, a method of adding a polyvalent amine in advance before distillation is employed. The monomer recovered by this preferred method is further improved in transparency quality.
[0012]
In order to add polyvalent amine to the liquefied pyrolysis product in advance, add 5 to 30% by weight of water to the liquefied thermolysis product and mix well, and then separate and remove the aqueous layer with a decanter or the like. It is desirable to purify the oil layer composed of the remaining thermal decomposition product by distillation.
[0013]
When a polyvalent amine is added to the thermally decomposed product, a precipitate is generated. Therefore, the subsequent operation is facilitated by dissolving and removing water by adding water. Moisture contained in the thermal decomposition product in a saturated state is removed during distillation purification.
[0014]
In order to prevent polymerization during operation, distillation purification is usually carried out at a reduced pressure in a reduced pressure state of 100 to 500 mmHg. The distillation can be carried out batchwise or continuously. The apparatus used for distillation purification is not particularly limited, but an apparatus equipped with a multistage distillation column is preferably used.
[0015]
【Example】
Hereinafter, the present invention will be described specifically by way of examples.
[0016]
[ Reference Example 1 ]
3 mm-thick acrylic plate consisting of 95% by weight methyl methacrylate and 5% by weight n-butyl acrylate with kraft protective paper affixed, and a 3 mm thick acrylic plate consisting of methyl methacrylate homopolymer with a polyethylene film affixed Were pulverized and mixed at a weight ratio of 1: 1. Next, 3 kg of the pulverized mixture was charged into a stainless steel dry distillation kettle with an inner diameter of 30 cm and a height of 50 cm, the inside of the kettle was sufficiently replaced with nitrogen gas, the kettle wall temperature was raised to 430 ° C., and the generated gas was cooled and liquefied. As a result, about 2.8 kg of a carbonized distillate was obtained.
[0017]
Next, after adding 5000 ppm of triethylenetetramine to the dry distillation liquid, it was charged in a glass old-type 30-stage distillation column having an inner diameter of 46 mm and distilled under reduced pressure of 300 mmHg. The reflux ratio was 3. After cutting 5% by weight of the first fraction, the product was collected and finally distillation was terminated leaving 15% by weight of high-boiling products. When the obtained product was analyzed by gas chromatography, high purity methyl methacrylate having a purity of 99.8% was obtained. When the number of colors (Hazen) of this product was measured according to JIS-K-4101, it was as good as 10.
[0018]
[ Reference Example 2 ]
Two distillation columns similar to those used in Reference Example 1 were connected to assemble a continuous distillation apparatus. The first low boiler removal tower supplies the raw material (dry distillation liquid) in the 20th stage from the bottom, and the subsequent high boiler removal tower supplies the bottoms of the low boiler removal tower in the 10th stage from the bottom. I made it. The dry distillation liquid obtained in the same manner as in Reference Example 1 was supplied to the low boiler removal column at a rate of 1.2 Kg / h and distilled at 300 mmHg. The reflux ratio was 3, and the distillate cut rate was 5%. At the same time, diethylenetriamine diluted 10-fold with methyl methacrylate was supplied to the dry distillation liquid supply stage at a ratio of 3000 ppm to the dry distillation liquid. On the other hand, the bottoms of the low boiler removal tower was further supplied to the high boiler removal tower and distilled at 200 mmHg. Distillation was continued for 3 hours. The reflux ratio was 2, and the product was obtained at a yield of 85% from the top of the column. When this product was analyzed by gas chromatography, high purity methyl methacrylate having a purity of 99.8% was obtained. When the number of colors (Hazen) of this product was measured, it was as good as 8.
[0019]
[ Reference Example 3 ]
The procedure was the same as in Reference Example 2 , except that the method for adding the polyvalent amine was changed. As a method for adding the polyvalent amine, 3000 ppm of triethylenetetramine was added to the dry distillation solution in advance, and triethylenetetramine diluted 10-fold with methyl methacrylate was added to the feed supply stage of the high boiler removal column at 200 ppm relative to the feed supply. Supplied in proportion. When the distillation was carried out continuously for 10 hours, the operation was stopped due to filter clogging provided at the outlet of the raw material supply pump to the low boiler removal column. When the product thus obtained was analyzed by gas chromatography, high purity methyl methacrylate having a purity of 99.8% was obtained. The number of colors (Hazen) of this product was measured and found to be 3 and good.
[0020]
[Example 1 ]
Thoroughly mixed with 15% water was added 3000ppm in advance carbonization solution triethylenetetramine in Reference Example 3, except that supply only after standing layer of the oil layer in low boilers removal column is as in Reference Example 3 The same was done. Distillation was carried out continuously for 30 hours, but it was able to operate smoothly without clogging the filter. When the product thus obtained was analyzed by gas chromatography, high purity methyl methacrylate having a purity of 99.8% was obtained. When the number of colors (Hazen) of this product was measured, it was as good as 2.
[0021]
【The invention's effect】
According to the present invention, it becomes possible to recover monomers that enable the production of plastic products having extremely high transparency from acrylic resin waste materials, promote the effective use of waste materials discharged from factories, etc. It contributes to the protection of the global environment.

Claims (1)

Acrylic resin waste is thermally decomposed in a gaseous state by dry distillation, and then the gaseous thermal decomposition product is liquefied, and then the liquefied thermal decomposition product is purified by distillation to recover the monomer. The monomer is removed from the acrylic resin waste material by adding 5 to 30% by weight of water to the polyamine in advance and mixing the mixture thoroughly, separating and removing the aqueous layer, and distilling and purifying the oil component layer. How to recover.