JP6558752B2 - Polyolefin recycling method from polyolefin composite materials - Google Patents

Description

  The present invention relates to a method of decomposing and removing a urethane resin from a composite containing a polyolefin resin as a main component, and material recycling only the main component polyolefin resin.

Among the materials that have been used in large quantities as automotive interior parts, the main components are PP, PE, ABS resin (acrylonitrile / butadiene / styrene copolymer synthetic resin), and ASA resin (acrylonitrile / styrene acrylate copolymer). There are many composites such as synthetic resin) and the like lined with urethane foam.
Among these materials, polyolefin resins such as PP and PE are lightweight plastics and at the same time have excellent mechanical properties and molding processability, and thus are widely used as automobile materials.
A single component resin material is used for the substrate using this polyolefin resin, and if it is recovered purely, it can be easily reused as a raw material, so-called material recycling is possible, and the added value is high. However, the substrates used for automotive interior parts are composites that are difficult to separate because there are many parts in which urethane foam with excellent cushioning properties is strongly fused. This is the current situation.
As a method for treating such a urethane resin, Patent Literature 1 and Patent Literature 2 are also disclosed as techniques relating to chemical recycling in which the composition is converted by a chemical reaction and then recycled.

JP-A-54-70377 JP-A-10-310663

However, the conventional techniques described in Patent Document 1 and Patent Document 2 are originally reused by decomposing the urethane resin by a chemical recycling method and recovering it as a raw material compound or a derivative thereof for producing the urethane resin. It is not intended to recycle the substrate itself to which the urethane resin is adhered or fused.
In the invention disclosed in Patent Document 1 and Patent Document 2, since the urethane resin is decomposed with high-temperature and high-pressure water at 200 to 370 ° C., recovery is impossible because the temperature exceeds the melting point of the polyolefin as the substrate. There was a problem.

  The present invention has been made in response to such a conventional situation, and chemically removes subcomponents other than polyolefin, in particular urethane, from a composite containing polyolefin as a main component. The purpose is to provide a recycling method that can be recycled for various uses.

In order to achieve the above object, a polyolefin recycling method from a polyolefin composite material according to claim 1 comprises a base material mainly composed of a polypropylene resin in a polyolefin, and a foam shape bonded or incorporated in the base material. A composite material having a fibrous or thin-film urethane resin and having a urethane resin content of 20 wt% or less is immersed in an aqueous NaOH solution having a concentration of 10 wt% to 25 wt% and 150 ° C. to 160 ° C. Then, the urethane resin is decomposed, and the insoluble polypropylene resin of the base material is extracted.
In the polyolefin recycling method from the polyolefin composite material having the above structure, the content of the urethane resin in the composite material is 20% by weight or less, that is, the content of the material mainly composed of the polypropylene resin of the base material is 80% by weight or more. Thus, only the urethane resin is decomposed even at 150 ° C. to 160 ° C., which is lower than the melting point of the polypropylene resin, by reducing the load on the NaOH aqueous solution and making it a high concentration NaOH aqueous solution of 10 wt% to 25 wt%. Works.

The polyolefin recycling method from the polyolefin composite material according to claim 2 is a group comprising a polypropylene resin as a main component of a polyolefin and containing an ABS (acrylonitrile butadiene styrene) resin or an ASA (acrylonitrile styrene acrylate) resin. 20% by weight to 25% by weight of a composite material having a material and a urethane resin in the form of a foam, fiber or thin film bonded or incorporated in the base material, the content of the urethane resin being 5% by weight or less It is immersed in an aqueous NaOH solution having a concentration by weight of 130 ° C. to 150 ° C. to decompose the urethane resin and extract the insoluble polyolefin resin, ABS resin or ASA resin of the base material.
In the polyolefin recycling method from the polyolefin composite material having the above structure, the content of the urethane resin in the composite material is 5% by weight or less, that is, the content of the material containing the polypropylene resin as the main component and containing the ABS resin or the ASA resin. By setting the weight to 95% by weight or more, the load on the NaOH aqueous solution is reduced, and by setting the NaOH aqueous solution at a high concentration of 20% by weight to 25% by weight, the melting point of the polypropylene resin, ABS resin, and ASA resin is 130 or less. It acts so as to decompose only the urethane resin even at 150 ° C.-150 ° C.

And the polyolefin recycling method from the polyolefin composite material which is the invention according to claim 3 is a base material mainly composed of polyethylene resin in polyolefin, and a foam, fiber or A composite material having a thin film-like urethane resin and having a urethane resin content of 5 wt% or less is immersed in an aqueous NaOH solution having a concentration of 20 wt% to 25 wt% and 120 ° C. to 130 ° C. After decomposing the urethane resin, the viscous urethane decomposition product adhering to the polyethylene resin surface is removed by washing with a water-soluble dilute acid or an organic solvent, and the insoluble polyethylene resin of the base material is extracted. It is what.
In the polyolefin recycling method from the polyolefin composite material having the above configuration, the content of the urethane resin in the composite material is 5% by weight or less, that is, the content of the material mainly composed of the polyethylene resin of the base material is 95% by weight or more. Thus, only the urethane resin is decomposed even at 120 ° C. to 130 ° C., which is below the melting point of the polyethylene resin, by reducing the load on the NaOH aqueous solution and making the NaOH aqueous solution at a high concentration of 20 wt% to 25 wt%. Works. However, there is a possibility that the urethane resin cannot be completely decomposed with a 120 ° C.-130 ° C. NaOH aqueous solution, and in this case, it adheres to the substrate as a viscous urethane decomposition product. Therefore, the water-soluble dilute acid or organic solvent acts to wash away this viscous material.
The reason why there is a range of 120 ° C. to 130 ° C. below the melting point of the polyethylene resin is that the melting point varies depending on the grade of polyethylene and the like.

Furthermore, the polyolefin recycling method from the polyolefin composite material which is the invention according to claim 4 is the polyolefin recycling method from the polyolefin composite material according to any one of claims 1 to 3, wherein the foam shape, When the content of the urethane resin in the form of a fiber or thin film exceeds 20% by weight, the base material and the urethane resin are crushed and separated in specific gravity in water or in an air stream to lower the content of the urethane resin. It is immersed in the NaOH aqueous solution.
In the polyolefin recycling method from the polyolefin composite material having the above structure, when the content of the urethane resin exceeds 20% by weight, the specific gravity separation distributes the crushed lighter urethane resin on the water or in the upper layer in the airflow, and the substrate The base material containing the polyolefin as a main component is distributed in the lower layer in water or in an air stream so as to adjust the content of the urethane resin.

  In the polyolefin recycling method from the polyolefin composite material according to claim 1 of the present invention, only the urethane resin bonded or incorporated into the base material can be decomposed without melting the polypropylene resin constituting the base material. It is also possible to recycle while maintaining the current shape and size. Furthermore, since a urethane resin that is limited in content but cannot be easily separated can be decomposed, recovery processing after decomposition is also easy.

  Further, in the polyolefin recycling method from the polyolefin composite material according to claim 2 of the present invention, the urethane resin bonded or incorporated into the base material without melting the polypropylene resin, ABS resin or ASA resin constituting the base material Therefore, it is possible to recycle the substrate while maintaining the current shape and size of the substrate.

  And in the polyolefin recycling method from the polyolefin composite material according to claim 3 of the present invention, only the urethane resin bonded or incorporated in the base material can be decomposed without melting the polyethylene resin constituting the base material. It is also possible to recycle while maintaining the current state of the shape and size of the substrate.

  And in the polyolefin recycling method from the polyolefin composite material according to claim 4 of the present invention, even if the content of the urethane resin in the form of foam, fiber or thin film exceeds 20% by weight, the specific gravity is separated. The content of the urethane resin can be adjusted, and the recycling method according to any one of claims 1 to 3 can be performed. However, since specific gravity separation is performed after crushing, the shape of the base material cannot be recycled while maintaining the current size and the like, and can be recycled depending on the state of the crushed base material.

It is a conceptual diagram which shows the process of the polyolefin recycling method from the polyolefin composite material which concerns on the 1st Embodiment of this invention. It is a conceptual diagram which shows the process of the polyolefin recycling method from the polyolefin composite material which concerns on the 2nd Embodiment of this invention. It is a conceptual diagram which shows a part of process of the polyolefin recycling method from the polyolefin composite material which concerns on the 3rd Embodiment of this invention. It is a graph which shows the relationship between the reaction temperature in NaOH aqueous solution (20 weight%) with respect to urethane foam, and a decomposition rate. It is a photograph showing a state in which the urethane foam is completely decomposed and the PP board is exposed as a result of holding the PP board backed with urethane foam by a NaOH aqueous solution (20 wt%) at 160 ° C. for 0 hour. 6 is an IR spectrum photograph of the surface of the recovered PP plate shown in FIG. 5. It is the IR spectrum photograph of the surface of PP board collect | recovered after hold | maintaining for 1 hour with 150 degreeC NaOH aqueous solution (20 weight%) with respect to PP board backed with urethane foam. It is the IR spectrum photograph of the surface of PP board collect | recovered after hold | maintaining for 1 hour with 140 degreeC NaOH aqueous solution (20 weight%). This is a photograph showing a state in which a part of urethane foam is mixed with the PP board without being decomposed as a result of being held for 0 hours with a 120 ° C NaOH aqueous solution (20% by weight) against the PP board lined with urethane foam. is there. It is IR spectrum photograph of the viscous substance adhering to the surface of PP board collect | recovered after hold | maintaining with 140 degreeC NaOH aqueous solution (20 weight%) for 1 hour. It is a photograph which shows the crushing piece of PP board backed by about 14 weight% urethane foam. 12 is a photograph showing PP-rich crushed pieces obtained as water as a result of specific gravity separation of the crushed pieces shown in FIG. 11 on water. FIG. 12 is a photograph showing urethane-rich crushed pieces obtained as a result of separation of the crushed pieces shown in FIG. 11 by specific gravity on water. It is the IR spectrum photograph of the surface after wash-removing the viscous thing which remained on PP board collect | recovered after hold | maintaining for 1 hour with 130 degreeC NaOH aqueous solution (20 weight%) with acetone. At 140 ° C. of aqueous NaOH (20 wt%) is an IR spectrum photograph of the surface after washing off the remaining viscous material to PP plate were collected after 0 hour hold at _1% H 2 SO _4.

Below, the polyolefin recycling method from the polyolefin composite material which concerns on the 1st Embodiment of this invention is demonstrated based on FIG. FIG. 1 is a conceptual diagram showing the steps of a method for recycling polyolefin from a polyolefin composite material according to the first embodiment of the present invention.
In FIG. 1, in step S <b> 1, a composite waste material including a base material mainly composed of PP (polypropylene) and a urethane resin bonded or incorporated in the base material is 130 ° C. to 160 ° C. which is equal to or lower than the melting point of the polypropylene resin. The urethane resin is decomposed by immersing in an aqueous alkaline solution such as an aqueous NaOH solution. If the content of the urethane resin is 20% by weight or less with respect to the entire composite waste, the load of the alkaline aqueous solution is reduced, so that it can be sufficiently decomposed with an aqueous NaOH solution having a concentration of 10% to 25% by weight at about 150 ° C. Furthermore, if the content of the urethane resin is set to about 5% by weight, even if it is 130 ° C., it can be completely decomposed quickly within one hour.
In this embodiment, the material to which the urethane resin adheres may include a polypropylene resin as a single component as a base material, but may include an ABS resin or an ASA resin. When other resins are contained in this manner, the melting point may be lower than that of polypropylene resin, so the temperature of an alkaline aqueous solution such as NaOH needs to be adjusted. In the case of ABS resin or ASA resin, the melting point is lower than that of polypropylene resin, so it is necessary to lower it to a range of about 130 ° C. at a temperature lower than 150 ° C. Moreover, even if PET (polyethylene terephthalate) resin is included as an accessory component in addition to the urethane resin, the urethane resin and the PET are made from a composite material based on a polypropylene resin or the like as long as the total amount is 20 wt% or less with the urethane resin. The resin can also be decomposed, and therefore the substrate can be recycled.

When the temperature of the aqueous NaOH solution is low, the reaction does not proceed and it is necessary to further reduce the load. Therefore, the content of the urethane resin needs to be reduced to 5% by weight or less with respect to the entire composite waste material. On the contrary, the concentration of the NaOH aqueous solution needs to be increased from 20% by weight to 25% by weight.
The alkali used in the first embodiment is not particularly limited, but NaOH is suitable in consideration of cost and alkali strength. The concentration of the aqueous NaOH solution is as high as 10% by weight or more as described above, and preferably 15 to 25% by weight. Such a high concentration is because the urethane resin is rapidly decomposed even at a low temperature. Further, the immersion time in the NaOH aqueous solution is processed in a short time within 1 hour.
When the base material of the composite waste material in the first embodiment includes ABS resin or ASA resin other than PP resin, the concentration of the NaOH aqueous solution is 20 wt% to 25 wt% as described above while lowering the temperature. %.
When immersed in an aqueous alkali solution in this way, an insoluble matter due to a base material such as PP and an alkaline decomposition solution containing a decomposed urethane resin as a soluble component are separated.
Thereafter, the insoluble matter due to the base material having a resin composition such as PP is washed in step S2 to remove the alkaline aqueous solution, and further dehydrated, and then pelletized again in step S3 and subjected to raw material recycling. Of course, if the shape and size of the base material are maintained, step S3 may be adopted as an option because it may be recyclable as a raw material without re-pelletizing in step S3.

On the other hand, an alkaline decomposition solution containing a decomposed urethane resin as a soluble component is repeatedly used as an alkaline reaction solution at 130 ° C. to 160 ° C.
In step S4, in order to maintain the quality of the alkaline reaction solution, a part is extracted, and Ca (OH) ₂ (calcium hydroxide) is added and filtered. This Ca (OH) ₂ has a function of returning Na ₂ CO ₃ (sodium carbonate) generated by the absorption of CO ₂ (carbon dioxide) in the air to the original NaOH and incomplete decomposition of the urethane resin. It works by adsorbing the viscous material that can be made to facilitate filtration.
The solid content separated by filtration is disposed as sludge in step S5, and the filtrate is added with NaOH to maintain the quality (concentration) of the alkaline reaction solution in step S6, and the alkali reaction solution is adjusted by adjusting the NaOH concentration. Return to.
In the polyolefin recycling method from the polyolefin composite material according to the first embodiment configured as described above, the temperature is equal to or lower than the melting point of the polypropylene resin, and the polypropylene resin is the main component in the high-concentration alkaline aqueous solution. By immersing the composite waste material containing urethane resin bonded or incorporated in the base material and the base material, the polypropylene resin does not melt and the urethane resin is decomposed and removed in the state of waste material Or since it can be pelletized again and collected, it can be recycled as a raw material, not as a fuel.

Next, a method for recycling polyolefin from a polyolefin composite material according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 is a conceptual diagram showing the steps of a method for recycling a polyolefin from a polyolefin composite material according to the second embodiment of the present invention.
In FIG. 2, in step S1, a composite waste material containing a base material mainly composed of PE and a urethane resin bonded or incorporated in this base material is added with a 120 ° C.-130 ° C. NaOH aqueous solution that is equal to or lower than the melting point of the polyethylene resin. The urethane resin is decomposed by immersing it in an aqueous alkali solution.
In this embodiment, since it is a base material in which polyethylene is used as the polyolefin, the temperature for decomposing the urethane resin must be lowered to 120 ° C. to 130 ° C. as compared to the first embodiment. Accordingly, the reactivity of the aqueous NaOH solution, which is an alkaline aqueous solution, decreases, so the content of the urethane resin must be reduced to 5% by weight or less with respect to the total composite waste, and the concentration of the aqueous NaOH solution is further reduced from 20% to 25% by weight. % Must be high.
However, the urethane resin still often does not completely decompose and often remains attached to the PE resin as a viscous product. Therefore, in the first embodiment, the alkaline aqueous solution is simply washed as step S2, but this is not the case. In the embodiment, as step S2a, a step of washing and dehydrating a viscous product of urethane resin with a diluted water-soluble dilute acid such as sulfuric acid or citric acid or an organic solvent such as acetone is provided.
Other processes after step S3 are the same as those in the first embodiment.

Next, a method for recycling polyolefin from a polyolefin composite material according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 is a conceptual diagram showing a part of a process of a polyolefin recycling method from a polyolefin composite material according to a third embodiment of the present invention.
In the present embodiment, in the composite waste material of the base material and the urethane resin such as PP or PE as the main component and the urethane resin, when the urethane resin is contained in an amount exceeding 20% by weight with respect to the composite waste material, the first described above. The step of reducing the content of the urethane resin is added so that the polyolefin recycling method from the polyolefin composite material according to the second embodiment or the second embodiment can be adopted.
Therefore, in FIG. 3, two steps of step S0a and step S0b are added to the previous stage of step S1, but thereafter, the steps described in FIG. 1 or FIG. 2 continue.
In FIG. 3, step S0a is a crushing process. First, a composite waste material of polyolefin such as PP or PE and urethane resin is crushed. After that is the specific gravity separation step of Step S0b. Since the foam-like urethane resin is lighter than PP and PE, it is possible to select specific gravity by water or wind power. Therefore, the composite waste material crushed in water or in the air stream is introduced, and the urethane resin that collects in the upper surface of the water or in the upper layer of the air current and the polyolefin resin that collects in the water or in the lower layer of the air current are separated by specific gravity, so It is possible to adjust the amount.
Thus, the polyolefin recycling method from the polyolefin composite material according to the first embodiment and the polyolefin according to the second embodiment are provided by providing the crushing step and the specific gravity separation step as a pre-step of the step of immersing in an alkaline aqueous solution. The content of the urethane resin can be adjusted to be suitable for carrying out the polyolefin recycling method from the composite material. What is necessary is just to adjust step S1 and the recycling process after it, adjusting to content of an appropriate urethane resin according to content of the kind of polyolefin resin contained in a base material, other ABS resin, ASA resin, etc.

  Examples of a method for recycling polyolefin from a polyolefin composite material according to the present embodiment will be described below with reference to the drawings.

In Example 1, the test which calculates | requires the relationship between the reaction temperature in NaOH aqueous solution with respect to the urethane foam backed by PP board, and a decomposition rate was implemented.
First, a PP plate lined with about 14% by weight of urethane foam was crushed using a 10 mmφ screen. A photograph of the fragment is shown in FIG. The part that appears white is urethane foam, and the part that appears black is PP as the base material.
150 g of the crushed material is put into a 1000 ml pressure vessel, 500 ml of 20 wt% NaOH aqueous solution is added, and the temperature is raised to a predetermined temperature (temperature indicated on the horizontal axis) at a heating rate of 80 to 100 ° C./h. As soon as it arrived, the heater power was turned off, “holding for 0 hours”, cooled, the inside was recovered, and the weight was measured to calculate the decomposition rate. In addition, a “1 hour hold” experiment was performed in which the sample was held at a predetermined temperature for 1 hour under the same conditions.

The result of the decomposition rate with respect to the reaction temperature is as shown in FIG.
In FIG. 4, the plot points of the decomposition rate when held for 20 hours with a 20% by weight NaOH aqueous solution are indicated by circles, and the plot points of the decomposition rate when held for 1 hour are indicated by square marks.
When the reaction temperature is 160 ° C., the decomposition rate is 100% when held for 0 hours, and when the reaction temperature is 150 ° C., the decomposition rate is 100% when held for 1 hour. Further, when the reaction temperature is about 130 ° C., the decomposition rate is about 40% between 0 hour holding and 1 hour holding, but there is not much difference, but at higher reaction temperatures, the decomposition rate when holding for 1 hour is almost the same. It is about 15% higher.

FIG. 5 is a photograph showing a state in which the PP plate is exposed as the remaining part after the urethane foam is completely decomposed after being held for 0 hours by a 160 ° C. NaOH aqueous solution. It can be understood that the whole is a black color of PP itself and the urethane foam is completely decomposed.
As shown in the photograph of FIG. 5, it was possible to completely decompose the urethane foam at 160 ° C. FIG. 6 shows an IR spectrum (infrared absorption spectrum) obtained by measuring the surface of the recovered product by the ATR method. FIG. 7 is an IR spectrum of the surface of the recovered product after being completely decomposed after being held for 1 hour with a 150 ° C. NaOH aqueous solution.
According to these figures, large absorption of 2800 cm ^-1, can be identified as PP in no significant absorption in addition to two absorption around 1400,1500cm ^-1. In addition, although 800-1200cm < ^-1 > has a small absorption, it has confirmed that it has overlapped with the absorption of the feeler centering on 1000cm < ^-1 > here.
Therefore, both FIG.6 and FIG.7 have obtained the result which becomes only PP, and it turns out that the urethane foam is decomposed | disassembled completely.

FIG. 8 is a diagram showing an IR spectrum on the surface of the PP plate recovered after being held for 1 hour with a 140 ° C. NaOH aqueous solution. That differ from the absorption by PP observed in FIGS. 6 and 7 than 8, it can be seen that the absorption is out near portion and 1500 cm ^-1, for example 3300 cm ^-1. It can be understood that substances other than PP having an amino group are detected by such absorption, and the urethane foam remains without being completely decomposed.
FIG. 9 is a photograph of the PP plate held for 0 hour at 120 ° C., which is lower than the decomposition treatment received by the PP plate whose IR spectrum is shown in FIG. It can be well understood that urethane that looks whitish as shown in the photograph of FIG. 9 remains without being completely decomposed.
This remaining urethane was the original resin itself and could not be completely removed even by washing with warm water. Therefore, it is considered difficult to recycle the PP plate as it is. Moreover, the viscous material produced | generated by the insufficient decomposition | disassembly of urethane has adhered to the surface of PP board shown by this FIG. Although this viscous material is of a level that cannot be visually confirmed, it is sticky when touched by hand, so its formation can be confirmed.
FIG. 10 is an IR spectrum of the viscous material dissolved and separated from the PP plate shown in FIG. 9 with acetone. That is, since it is an IR spectrum obtained by analyzing the viscous material itself by the transmission method, it is not affected by the PP plate. Therefore, although absorption similar to that of the PP plate is observed at 2800 cm ⁻¹ as in FIGS. 6 and 7, this is infrared absorption of the viscous material.

Next, as Example 2, the crushed pieces of the PP plate lined with about 14% by weight of urethane foam shown in FIG. 11 were separated by specific gravity on water.
FIG. 12 shows an underwater portion having a urethane content of about 5%, and FIG. 13 shows a water portion of almost the entire amount of urethane foam. Thus, it can isolate | separate into the crushing piece which floats on water and the crushing piece which stays in water according to content of each urethane foam of the crushing piece of PP board backed with the urethane foam which is lightweight compared with PP.
Therefore, when the content of the urethane foam is high, it is possible to separate the specific gravity as a crushed piece, and then to reduce the content of the urethane foam and to perform a decomposition treatment using an alkaline aqueous solution such as an aqueous NaOH solution.

Next, as Example 3, the same treatment as in Example 1 was performed on the water sample of about 5% of the urethane foam separated in Example 2. Specifically, it was kept for 1 hour with a 120 ° C. aqueous NaOH solution (20 wt%). As a result, the viscous substance remained, but the urethane could be decomposed and removed. Similarly, a slightly viscous substance remained at 130 ° C., but it was decomposable to a recyclable level. Further, even at low concentration NaOH (5% and 10%), the urethane could be completely removed if it was kept at 150 ° C. for 1 hour.
Table 1 summarizes the test results of Example 1 and Example 3.
The urethane decomposition level shown in this table is determined by analysis of an IR spectrum obtained by measuring the surface of the recovered PP plate by the ATR method.
What is indicated by a double circle is a level at which no urethane was detected, and the circle is a level at which absorption is observed around 3400 cm -1, but there is almost no contact with a viscous material. . In addition, the triangular mark clearly has a viscous substance attached, and a large absorption is also observed in IR. However, it can be completely removed by washing with a dilute acid or an organic solvent, so there is no problem even if it is recycled. Further, the viscous material at that level is such that even if it is on the surface of the PP surface, it can be visually recognized that the gloss is only to some extent, and it cannot be understood even if a photograph is taken. However, since the urethane is not decomposed and remains in its original state and cannot be removed by washing with dilute acid or acetone (organic solvent), the cross mark is at a level that cannot be recycled.

Next, as a sample in which a viscous substance remains as Example 4, a crushed piece of a PP plate lined with 15% by weight of urethane foam was prepared by holding in a 20% by weight NaOH aqueous solution at 130 ° C. for 1 hour, and then acetone. Washed with.
As a result, the IR spectrum of the sample surface was as shown in FIG. 14, and the viscous substance was completely removed. Even when methanol was used instead of acetone, it could be completely removed in the same manner. That is, it was easily removed using an organic solvent that is safe and easy to use.

Furthermore, as Example 5, the result of washing a sample prepared under conditions different from the sample of Example 4 using dilute acid will be described.
A sample was prepared by holding a crushed piece of a PP plate lined with 15% by weight of urethane foam in a 5% by weight aqueous NaOH solution at 150 ° C. for 1 hour. When the sample was washed with 0.2% sulfuric acid, 1% sulfuric acid, and 2.5% citric acid, an IR spectrum equivalent to that in Example 4 (FIG. 15) was obtained, and the viscous substance could be completely removed. The weight loss (weight ratio of viscous substance) at this time was about 0.7%.

  Finally, as Example 6, since corrosion of a stainless steel container may become a problem during cleaning with dilute acid, a corrosive test was conducted using stainless steel (SUS304). Specifically, as a result of immersing a SUS304 plate having a thickness of 0.93 mm × 20 mm × 50 mm in 0.2 %% sulfuric acid, 1% sulfuric acid, and 2.5% citric acid, the weight decreased after 300 hours at 23 ° C. As shown in Table 2, it was found that the cleaning can be performed in a container made of SUS304 at less than 0.01%.

  As described above, the invention described in the first to fourth aspects of the present invention is a method of melting a polyolefin in a composite material including a base material having a polyolefin resin composition and a urethane resin bonded or incorporated in the base material. It is possible to provide a method for recycling a separable polyolefin without causing it to occur, and it can be used for an efficient method for recycling a plastic composite material.

Claims (3)

  Among polyolefins, it has a base material mainly composed of polypropylene resin, and a foam-like, fibrous or thin-film-like urethane resin bonded or incorporated in this base material, and the content of the urethane resin is 20% by weight or less. The composite material is immersed in a NaOH aqueous solution having a concentration of 10% to 25% by weight and 150 ° C. to 160 ° C. to decompose the urethane resin and extract the insoluble polypropylene resin of the base material. A method for recycling polyolefins from polyolefin composites.   Of a polyolefin, a polypropylene resin as a main component, a base material containing an ABS (acrylonitrile butadiene styrene) resin or an ASA (acrylonitrile styrene acrylate) resin, and a foam, fiber, or thin film that is bonded or incorporated into the base The urethane resin is immersed in an aqueous NaOH solution having a concentration of 20% to 25% by weight and 130 ° C. to 150 ° C. A method for recycling polyolefin from a polyolefin composite material, comprising decomposing and extracting insoluble polyolefin resin and ABS resin or ASA resin of the base material.   It has a base material mainly composed of polyethylene resin among polyolefins, and a foam-like, fiber-like or thin-film-like urethane resin bonded or incorporated in this base material, and the content of the urethane resin is 5% by weight or less. The composite material is immersed in an aqueous NaOH solution having a concentration of 20% to 25% by weight and 120 ° C. to 130 ° C. to decompose the urethane resin, and then the viscous urethane decomposition product attached to the polyethylene resin surface is obtained. A method for recycling polyolefin from a polyolefin composite material, which comprises removing the insoluble base polyethylene resin by washing with a water-soluble dilute acid or an organic solvent and removing the insoluble base material.