JP7383093B1 - How to recycle silicone coated resin base material - Google Patents

Abstract

The present invention provides a method for separating a silicone resin as a depolymerized product from a resin base material coated with a silicone resin such as silicone rubber, and recovering and recycling both the resin base material and the depolymerized product of the silicone resin. [Solution] A method for recovering a depolymerized product of a coated silicone resin and a resin base material from a resin base material coated with a silicone resin, the method comprising: (A) tetraalkylammonium salt: 0.01% by mass or more; 30% by mass, (B) organic solvent: 70% by mass to 99.99% by mass. . [Selection diagram] None

Description

The present invention relates to a method for recycling silicone coated resin substrates.

Conventionally, silicone-coated resin base materials, which are obtained by coating the surface of a resin base material with curable silicone rubber to form a cured film, have excellent heat resistance, weather resistance, flame retardancy, and the like. Therefore, it is suitable for applications such as automobile airbag base fabrics, tent curtain coatings, and cable coatings for electric wires. These applications require strong adhesion between the silicone rubber coating material and the resin base material. Examples of such methods include applying a primer to the base material and adding an internal adhesive to silicone rubber.

On the other hand, silicone polymers consume a large amount of electricity during production, particularly during the electrical reduction process from silica (silicon dioxide) to metallic silicon, resulting in the emission of a large amount of CO ₂ . Therefore, from the perspective of reducing environmental impact, it is strongly desired to recover and recycle silicone monomers from discarded silicone rubber to reduce _CO2 emissions. However, as mentioned above, the silicone rubber coating material and the resin base material are often strongly adhered to each other. Therefore, it is not easy to separate the silicone rubber coating material and the resin base material and to collect and recycle both materials.

As a method for dissolving silicone rubber, a silicone dissolving solution containing phosphonitrile chloride and a linear polysiloxane having a degree of polymerization of 10 to 50 is disclosed (Patent Document 1). With this method, silicone rubber can be selectively dissolved without causing swelling of other plastic members. However, it is necessary to use phosphonitrile chloride, which is extremely toxic, and there are concerns about health damage to the surrounding area and environmental burden.

Further, as another dissolution method, a solubilizer for silicone rubber is disclosed in which a tetraalkylammonium fluoride and an inorganic base capable of bonding with hydrogen ions are dissolved in an organic solvent (Patent Document 2). This method allows the silicone rubber to be dissolved without corroding the metal piece. However, it is necessary to dissolve an inorganic base capable of bonding with hydrogen ions in an organic solvent, which limits the types of solvents that can be used. Furthermore, this document only specifies the dissolution rate of the silicone resin and its corrosivity to metal pieces, and the effects on other plastic base materials and recovery of the silicone polymer are unclear.

In addition, as a method for separating silicone rubber from a resin base material, a silicone-coated base fabric for air bags, which is a PA66 base fabric coated with silicone, is dissolved in a strong alkaline solution containing a tertiary amine, an anionic surfactant, and sodium hydroxide. A method of mixing and separating the two in a container is disclosed (Patent Document 3). However, this method requires long-term treatment with a strongly alkaline aqueous solution with a pH of 13 or higher, and there is concern that damage to the dissolution equipment may occur. Furthermore, this method cannot be used for resin base materials that cannot withstand strong alkalinity.

Another method is to mix a PA66 base fabric with a silicone coated base fabric for air bags in a solution containing an alkylbenzenesulfonic acid and a saturated hydrocarbon with a flash point of 70°C or higher, and then separate the mixture. It has been disclosed (Patent Document 4). However, this method requires the use of a strongly acidic solution, and there are concerns about corrosion of equipment and damage to the health of workers. Furthermore, this method cannot be used for resin base materials that cannot withstand strong acidity.

Special Publication No. 2014-524941 Special table 2015-505886 publication JP 2017-124553 Publication JP2022-073181A

The present invention has been made in view of the above circumstances, and involves separating the silicone resin as a depolymerized product from a resin base material coated with a silicone resin such as silicone rubber, and depolymerizing the resin base material and the silicone resin. The aim is to provide a way to collect and recycle both materials.

In order to solve the above problems, the present invention
A method for recovering a depolymerized product of a coated silicone resin and a resin base material from a resin base material coated with a silicone resin, the method comprising:
(A) Tetraalkylammonium salt: 0.01% by mass to 30% by mass,
(B) Organic solvent: 70% by mass to 99.99% by mass,
Provided is a method for recycling a silicone-coated resin substrate, which includes the step of immersing a resin substrate coated with the silicone resin in a silicone solution consisting of the following.

With such a recycling method, it becomes possible to recover the resin base material and convert the silicone resin into its depolymerized product with high efficiency.

As the tetraalkylammonium salt of the component (A), it is preferable to use a tetraalkylammonium salt whose counter ion is a fluoride ion or a hydroxide ion.

Such a tetraalkylammonium salt functions better as a catalyst.

As the component (A), it is preferable to use a tetraalkylammonium salt whose alkyl groups are independently alkyl groups having 1 to 4 carbon atoms.

Such a tetraalkylammonium salt functions even better as a catalyst.

As the component (B), it is preferable to use one or more organic solvents selected from the group of saturated aliphatic hydrocarbons, aromatic hydrocarbons, ether compounds, carbonyl compounds, and alcohol compounds.

Such an organic solvent acts better as a swelling agent for the silicone resin that was coated and as a solvent for the tetraalkylammonium salt.

It is preferable to use a synthetic fiber woven fabric as the resin base material.

In the recycling method of the present invention, woven fabrics made of synthetic fibers can be recovered.

The synthetic fiber woven fabric is preferably a base fabric made of nylon 66 (PA66) or polyethylene terephthalate (PET) for airbags.

Such a recycling method is suitable as a method for recycling woven fabric for airbags.

According to the present invention, by immersing a silicone coated resin base material in a silicone solution containing a tetraalkylammonium salt and an organic solvent, the resin base material and silicone rubber (silicone resin) are separated, and the base material is recovered and recycled. Furthermore, it becomes possible to convert silicone resin into a depolymerized product of silicone resin with high efficiency.

There has been a need for a recycling method that efficiently recovers both the depolymerized product of the coated silicone resin and the resin base material from the resin base material coated with silicone resin.

In order to achieve the above object, the present inventors conducted various studies and found that the resin base material and the silicone resin were separated by immersing the silicone coated resin base material in a solution consisting of a tetraalkylammonium salt and an organic solvent. , it is possible to collect and recycle the resin base material. Furthermore, it has been discovered that silicone resins such as silicone rubber can be converted into depolymerized silicone resins with high efficiency, and the present invention has been completed. Examples of the depolymerized product include cyclic organopolysiloxanes having about 3 to 20 silicon atoms. Among them, octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) are silicone monomers that can be converted into silicone polymers by polymerization using an appropriate catalyst. , is a useful precursor for silicone polymers.

That is, the present invention
A method for recovering a depolymerized product of a coated silicone resin and a resin base material from a resin base material coated with a silicone resin, the method comprising:
(A) Tetraalkylammonium salt: 0.01% by mass to 30% by mass,
(B) Organic solvent: 70% by mass to 99.99% by mass,
This is a method for recycling a silicone-coated resin substrate, which includes the step of immersing a resin substrate coated with the silicone resin in a silicone solution consisting of the following.

<Silicone solution>
The silicone solution used in the present invention is
(A) Tetraalkylammonium salt: 0.01% by mass to 30% by mass,
(B) Organic solvent: 70% by mass to 99.99% by mass,
It is a silicone solution consisting of.

Each component of the silicone solution used in the present invention will be explained in detail below.

[A component]
Component (A) is a tetraalkylammonium salt and acts as a decomposition (depolymerization) catalyst for siloxane bonds (-O-Si-O-).

In the tetraalkylammonium salt, the four alkyl groups are preferably independently alkyl groups having 1 to 4 carbon atoms, and more preferably all four are the same alkyl group. Further, as the counter ions, halide ions such as chloride ions, bromide ions, and fluoride ions, and hydroxide ions are preferable, and fluoride ions and hydroxide ions are more preferable.

Specific examples of tetraalkylammonium salts include fluoride ion salts such as tetramethylammonium fluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride, tetraisopropylammonium fluoride, and tetrabutylammonium fluoride, and tetramethylammonium hydroxy Examples include hydroxide ion salts such as tetraethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetraisopropylammonium hydroxide, and tetrabutylammonium hydroxide. Particularly preferred are tetrabutylammonium fluoride, tetramethylammonium fluoride, and tetrabutylammonium hydroxide.

The content of the tetraalkylammonium salt as component (A) is 0.01% to 30% by mass, preferably 0.05% to 20% by mass, based on the total amount of the organic solvent as component (B). Preferably it is 0.1% by mass to 10% by mass. When the blending amount is lower than 0.01% by mass, the silicone resin may not be sufficiently decomposed, and when it is higher than 30% by mass, the cost increases and is economically disadvantageous.

Component (A) may be used alone or in combination of two or more.

[B component]
Component (B) is an organic solvent and acts as a swelling agent for the silicone resin coated on the resin base material and as a solvent for the component (A).

Component (B) is a linear or branched organic solvent such as hexane, heptane, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane, icosane, normal paraffin, isoparaffin, etc. Aromatic carbonization of saturated aliphatic hydrocarbons, benzene, toluene, dimethylbenzene, trimethylbenzene, ethylbenzene, diethylbenzene, triethylbenzene, propylbenzene, dipropylbenzene, tripropylbenzene, isopropylbenzene, diisopropylbenzene, triisobutylbenzene, etc. Hydrogen, linear or branched saturated aliphatic ketone compounds such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, diisobutyl ketone, alicyclic ketone compounds such as cyclopentanone, cyclohexanone, etc. , methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, propyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, etc. ester compounds, dialkyl ether compounds such as diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dipentyl ether, dihexyl ether, dioctyl ether, glycol ether compounds such as diethylene glycol dimethyl ether, diethylene glycol diethyl ether, polyethylene glycol dimethyl ether, diethylene glycol diethyl ether, etc. , alicyclic ether compounds such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane, aliphatic alcohols such as methanol, ethanol, propanol, butanol, isopropyl alcohol, isobutanol, tertiary butyl alcohol, secondary butyl alcohol, and 2-ethylhexanol. Among them, saturated aliphatic hydrocarbons, aromatic hydrocarbons, ether compounds, carbonyl compounds, and alcohol compounds are particularly preferred. Specifically, preferred organic solvents include decane, dodecane, tetrahydrofuran, toluene, isopropanol, and diethylene glycol dimethyl ether.

The organic solvent of component (B) can be any organic solvent selected from the above group, but preferably has a boiling point of 50°C to 300°C, more preferably 60°C to 250°C, and more preferably 65°C to 200°C. It is. When the boiling point is 50°C or higher, the volatility of the organic solvent is low and there is no increase in environmental burden or deterioration of workability.If the boiling point is 300°C or lower, the solvent can be removed by distillation from the solution after the dissolution process It is easy to collect and recycle.

The content of component (B) is 70% by mass to 99.99% by mass based on the total amount of component (A) and the tetraalkylammonium salt.

In addition, the said (B) component may be used individually or may use 2 or more types together.

<Dissolution conditions>
A resin substrate coated with silicone resin is immersed in the prepared silicone solution. At this time, it is preferable to cut the resin base material coated with silicone resin into a size that can be easily stirred. There are no particular restrictions on the size, thickness, condition, etc. of the silicone coating resin base material, but when it is cut into pieces with a side size of 1 mm to 500 mm, preferably 2 mm to 300 mm, more preferably 5 mm to 100 mm, it can be stirred with a stirring blade or the like. This is suitable because it is easy to use. Of course, the base material may be immersed as it is without being cut.

At this time, simply immersing the silicone coated fabric in the dissolving solution will dissolve the silicone coated fabric sufficiently, but stirring with a stirring blade such as a dynamic mixer, stirring with a stirring bar such as a magnetic stirrer, shaking treatment with a shaker, ultrasonic wave treatment, etc. Treatments are effective in improving the dissolution rate, and stirring using a dynamic mixer or magnetic stirrer is particularly preferred.

Although there is no particular restriction on the weight ratio of the dissolving liquid and the silicone coated resin base material, it is preferable to use an amount of the dissolving liquid that completely immerses the silicone coated resin base material.

The dissolution temperature is not particularly limited as long as it is below the boiling point of the organic solvent used, but it is 10°C to 150°C, preferably 15°C to 100°C, more preferably 20°C to 80°C. If the temperature is 10° C. or higher, the dissolution rate of the silicone resin will not become extremely slow, and if the temperature is 150° C. or lower, the damage to the resin base material will not increase.

The dissolution time varies depending on the weight ratio of the silicone coating base fabric and the dissolving liquid, stirring conditions, and temperature conditions, and it is preferable to select an appropriate time. Usually, the time is 0.2 minutes to 120 minutes, preferably 0.5 minutes to 90 minutes, and more preferably 1 minute to 60 minutes.

<Silicone resin>
The silicone resin of the resin base coated with the silicone resin used in the present invention is, for example, an addition-curing silicone rubber, a radical-curing silicone rubber, a condensation-curing silicone rubber, or an ultraviolet-curing silicone rubber, which has a siloxane bond. It is applicable to all silicone rubbers. Furthermore, even if it contains hydrophobic silica, hydrophilic silica, iron oxide, ultramarine blue, silicone resin, carbon black, glass beads, resin balloons, diatomaceous earth, metal oxide powder, metal powder, or metal hydroxide powder as a filler. Become adaptable. Further, it is also possible to include reaction control agents, antioxidants, adhesion aids, adhesion promoters, plasticizers, flame retardants, etc. as additives.

<Resin base material>
Examples of the resin base material include acrylonitrile-butadiene-styrene (ABS) resin, polycarbonate (PC) resin, polyurethane (PU) resin, polystyrene (PS) resin, acrylic resin, polyethylene terephthalate (PET) resin, polybutylene terephthalate ( PBT) resin, polyphenylene oxide (PPO) resin, polyphenylene sulfide (PPS) resin, polysulfone (PSU) resin, nylon 6 (PA6) resin, nylon 66 (PA66) resin, polyphthalamide (PPA) resin, polyimide (PI) ) resins, etc. Among these, PA66 or PET is preferable.

In addition, it is preferable to use a synthetic fiber woven fabric as the resin base material, and it is more preferable that the synthetic fiber woven fabric is a base fabric made of nylon 66 (PA66) or a base fabric made of polyethylene terephthalate (PET) for airbags. preferable.

The coated silicone resin can be depolymerized by immersing the resin base material coated with the silicone resin in the above silicone solution. Preferred specific examples of the resulting depolymerized product include D4 to D6. Therefore, the depolymerized product of the coated silicone resin and the resin base material can be recovered and recycled from the resin base material coated with the silicone resin.

EXAMPLES The present invention will be specifically described below using Examples and Comparative Examples, but these Examples do not limit the present invention in any way.

<Preparation of silicone solution>
Components (A) and (B) were mixed at 25° C. for 5 minutes in the proportions shown in Tables 1 to 4 to prepare.

<Preparation of silicone coating resin base material>
KEG-2052T-A/B (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a heat addition-curing liquid silicone coating material, was coated at 25 g/m ² on PA66 base fabric (210 denier) and PET base fabric (495 denier), A silicone-coated base fabric was created by placing it in a drying oven at 200°C for 1 minute and curing it by heating.

<Example/Comparative example>
The silicone coated base fabric was cut into approximately 5 mm square pieces, and 1.0 g was weighed into a 20 mL eggplant flask. Thereafter, 10.0 g of each of the prepared solutions and a stirrer were placed in an eggplant flask equipped with a cooling tube, and heated at 60° C. for 30 minutes using an oil bath while stirring with a magnetic stirrer. After heating, the fabric samples were allowed to cool to room temperature and washed with ion-exchanged water and acetone.The silicone-coated surface was measured by IR, and the state of silicone removal was observed using an optical microscope. confirmed. In addition, the content of D4 to D6 in the remaining solution was measured by headspace GC using the method described below.

<IR measurement method>
IR was measured on the silicone-coated surface using the following equipment and conditions.
Equipment: Spectrum65 FT-IR spectrometer
(Manufactured by Perkin Elmer)
Measurement range: 4,000-550cm ^-1
Number of measurements: 8 times The case where the peak of Si-CH ₃ near 2950 cm ^-1 was detected was evaluated as "x", and the case where it was not detected was evaluated as "○". The results are shown in Tables 1 to 4.

<Surface observation using an optical microscope>
The surface of the silicone-coated surface was observed using an optical microscope using the following equipment and conditions.
Equipment: LEXT OLS5000 (manufactured by Olympus Corporation)
Magnification: 235x Observed with an optical microscope, and for the item "Removal of silicone resin", if silicone resin remains, it is evaluated as "x", and if no silicone resin is found, it is evaluated as "○". Table 1 ~ 4. In addition, regarding the item "condition of base fabric," the case where dissolution of the threads constituting the base fabric was observed was evaluated as "x", and the case where no dissolution was observed was evaluated as "○". The results are shown in Tables 1 to 4.

<Measurement of D4-D6 amount by headspace GC (HS-GC)>
To the solution after dissolution, 10.0 g of a 1,000 ppm heptane-toluene solution was added as an internal standard and mixed for 1 minute at 25°C. Thereafter, filtration was performed using a membrane filter, and 5 μL of the filtrate was measured into a HS-GC vial using a 10 μL microsyringe, and HS-GC was measured under the following conditions.

GC device: GC-2030 (manufactured by Shimadzu Corporation)
Headspace sampler: HS-20 (manufactured by Shimadzu Corporation)
Column: HP-5MS (manufactured by Agilent Technologies)
Vial heating conditions: 120°C/10 minutes Carrier gas: Helium Detector: FID

After the analysis, the chromatogram peak areas of D4 to D6 and heptane, which is an internal standard, were measured, and the content of D4 to D6 was calculated from the following formula, and the results were rounded to the nearest 100 and are shown in Tables 1 to 4. .

Content rate of D4 to D6 (ppm) = (GC total area of D4 to D6 / GC area of heptane) × 2.59 × {(solvent + heptane-toluene solution weight (g)) / coating base fabric weight (g) }×500 (ppm)
2.59: FID detection intensity conversion coefficient for heptane and D4 to D6 500: Concentration of internal standard (heptane)

<Change in mass of resin base material>
PA66 base fabric (210 denier) and PET base fabric (495 denier) were each cut into approximately 5 mm squares, and 1.0 g was weighed into a 20 mL eggplant flask. Thereafter, 10.0 g of each of the prepared solutions and a stirrer were placed in an eggplant flask equipped with a cooling tube, and heated at 60° C. for 30 minutes using an oil bath while stirring with a magnetic stirrer. After the heating process was completed, it was allowed to cool to 25°C, and the obtained base fabric sample was washed with ion-exchanged water and acetone, and then dried in a dryer at 100°C for 1 hour. Thereafter, the mass of the obtained sample was measured, the mass change rate was calculated, and the results were rounded to the second decimal place and are shown in Tables 1 to 4.

In Examples 1 to 19, the silicone polymer was efficiently recovered as a depolymerized product of D4 to D6 silicone without damaging the PA66 base fabric and the PET base fabric. The recovered D4 to D6 can be recycled into silicone polymers by polymerization using an appropriate catalyst. Further, the separated PET base fabric or PA66 base fabric can be recycled as a resin plate or thread by thermally melting it. On the other hand, in Comparative Examples 1 to 5, the silicone resin coating material and the resin base material could not be separated, and D4 to D6 could hardly be recovered. Furthermore, in Comparative Examples 6 and 7, the PET base fabric was damaged and the amount of recovered D4 to D6 was also small.

Note that the present invention is not limited to the above embodiments. The above-mentioned embodiments are illustrative, and any embodiment that has substantially the same configuration as the technical idea stated in the claims of the present invention and has similar effects is the present invention. covered within the technical scope of

Claims (6)

A method for recovering a depolymerized product of a coated silicone resin and a resin base material from a resin base material coated with a silicone resin, the method comprising:
(A) Tetraalkylammonium salt: 0.01% by mass to 30% by mass,
(B) Organic solvent: 70% by mass to 99.99% by mass,
1. A method for recycling a silicone-coated resin substrate, comprising the step of immersing a resin substrate coated with the silicone resin in a silicone solution comprising: 2. The silicone coated resin base material according to claim 1, wherein the tetraalkylammonium salt of the component (A) is a tetraalkylammonium salt whose counter ion is a fluoride ion or a hydroxide ion. How to recycle. 2. The method for recycling a silicone coated resin substrate according to claim 1, wherein a tetraalkylammonium salt whose alkyl group is independently an alkyl group having 1 to 4 carbon atoms is used as the component (A). 2. The method according to claim 1, wherein as the component (B), one or more organic solvents selected from the group of saturated aliphatic hydrocarbons, aromatic hydrocarbons, ether compounds, carbonyl compounds, and alcohol compounds are used. How to recycle silicone coated resin base materials. 2. The method for recycling a silicone coated resin base material according to claim 1, wherein a woven fabric of synthetic fiber is used as the resin base material. 6. The method for recycling a silicone coated resin base material according to claim 5, wherein the synthetic fiber woven fabric is a base fabric made of nylon 66 (PA66) or polyethylene terephthalate (PET) for airbags.