A method for preparing a latent microcapsule platinum catalyst

Abstract

This invention discloses a method for preparing a latent microcapsule platinum catalyst. A random copolymer of methyl methacrylate and butyl methacrylate prepared by atom transfer radical polymerization is used as the wall material, and Karstedt catalyst (a silicone rubber curing agent) is used as the core material. The encapsulated latent platinum catalyst is obtained by solvent evaporation. The microcapsule platinum catalyst obtained by this invention is a white solid powder with small particle size and high particle size concentration. It exhibits good compatibility with silicone rubber after mixing. The microcapsule wall material is composed of a random copolymer of methyl methacrylate and butyl methacrylate. The softening temperature and time of the microcapsule wall material can be controlled by adjusting the polymerization ratio of the two materials. It can be stably stored at room temperature for more than 12 weeks. Heating to 100°C completely cures the silicone rubber component within 1 hour. It exhibits high catalytic activity and controllable reaction, and can be used for the preparation of single-component addition-type liquid silicone rubber.

Description

Technical Field

[0001] This invention relates to latent catalysts and their preparation methods. Specifically, it relates to a method for preparing a latent microcapsule platinum catalyst. Background Technology

[0002] Silicone rubber is renowned for its excellent electrical insulation, crosslinking process with no byproduct release, minimal shrinkage, and ability to maintain outstanding electrical properties under harsh conditions. Compared to similar materials such as epoxy resins and polyurethane potting compounds, addition-cure liquid silicone rubber generates less heat during curing, resulting in good shock absorption and cushioning effects, while also exhibiting excellent heat resistance, cold resistance, weather resistance, and superior adhesion. These characteristics make addition-cure liquid silicone rubber exhibit superior performance in the encapsulation or potting of electronic components and electrical equipment.

[0003] Currently, two-component addition-type liquid silicone rubber dominates the market; however, problems such as air bubbles, long vulcanization times, and slow curing speeds arise during its mixing process, reducing production efficiency. To address these issues, the use of microcapsule catalysts has become a feasible and economical method. The silicone rubber curing agent is encapsulated within the microcapsule wall material, thus preventing direct contact with the silicone rubber under storage conditions and physically isolating it to inhibit the curing reaction. When curing is required, the microcapsules rupture by increasing temperature or pressure, releasing the internal core curing agent, thereby completing the curing reaction.

[0004] Silicone used in electronic packaging or potting for electronic circuits and precision microelectronic circuits suffers damage or aging during high-temperature curing, thus requiring lower molding temperatures, typically below 100°C. Therefore, the wall material of the microencapsulated platinum catalyst needs a low softening point temperature. When the temperature rises to 100°C, the platinum can flow out quickly, acting as a catalyst. Some studies have used polystyrene, polymethyl methacrylate, and polyurethane as wall materials, but these also have drawbacks. For these common polymers, their glass transition temperatures are generally high, exceeding 100°C, resulting in high softening points. This often requires higher temperatures and longer heating times for the internal core material to flow out smoothly and quickly. Therefore, existing technologies and methods still need improvement and development.

[0005] Microencapsulation technology refers to the process of encapsulating a specific active substance with a film-forming material using a particular method, creating microspheres with a core-shell structure. The particle size is typically in the micrometer range, mostly tens of micrometers, and varies depending on the preparation method and conditions. The encapsulation effect of microcapsules creates a physical barrier between the internal substance and the external environment. Once the shell is subjected to external forces, causing it to rupture or soften and collapse, the internal substance is released or diffuses out, reacting with the external substance. The unique core-shell structure provides protection for the internal core material, preventing it from being affected by the external environment. The release of the core material can be controlled by methods such as pressurization or heating. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a method for preparing a latent microencapsulated platinum catalyst. The microencapsulated platinum catalyst has a microcapsule wall material composed of a random copolymer P (MMA-co-BMA) of methyl methacrylate and butyl methacrylate synthesized by ATRP. By controlling the copolymerization ratio of the two, the glass transition temperature of the copolymer is controlled, thereby controlling the softening point of the wall material. This aims to solve the problems of excessively high softening points and long softening times in existing microencapsulated platinum catalysts, which prevent the platinum catalyst from flowing out in a timely manner.

[0007] This invention discloses a latent microcapsule platinum catalyst comprising a core material and a wall material; the core material is a Karstedt catalyst with silicone rubber curing agent, and the wall material is a random copolymer of methyl methacrylate and butyl methacrylate prepared by atom transfer radical polymerization.

[0008] The microcapsules are macroscopically white solid powders with smooth surfaces and a particle size of 1–30 μm.

[0009] The core material accounts for 10-40% of the total mass of the microcapsule.

[0010] The preparation method of the random copolymer of methyl methacrylate and butyl methacrylate includes the following steps: methyl methacrylate, butyl methacrylate, ethyl 2-bromoisobutyrate, N,N,N',N,N"-pentamethyldiethylenetriamine and toluene solvent are placed in a reaction flask, the flask is sealed, and the system is subjected to a freezing-vacuuming-thawing operation with liquid nitrogen, repeated three times. Then, nitrogen gas is introduced, and cuprous bromide is added through the top opening of the flask under nitrogen protection. After sealing the reaction flask, vacuuming is continued for 2 minutes. After thawing, the system is placed in an oil bath at 110°C and heated for 12 hours. Then, the reaction is stopped by freezing with liquid nitrogen. The copper compound is removed by filtration with alumina. The solution is concentrated by rotary evaporator, and the solution is added dropwise to methanol to precipitate the product. The product is filtered and vacuumed to obtain the final white powder product.

[0011] The molar ratio of methyl methacrylate to butyl methacrylate is 10:(1-4). The molar ratios of methyl methacrylate to ethyl 2-bromoisobutyrate, N,N,N',N,N"-pentamethyldiethylenetriamine, and cuprous bromide are (100-300):(1-4):(1:4):(1-3), and the amount of toluene solvent used is 10-50 mL.

[0012] The preparation method of the latent microcapsule platinum catalyst of the present invention is as follows: First, a random copolymer P (MMA-co-BMA) of methyl methacrylate and butyl methacrylate is synthesized by atom transfer radical polymerization (ATRP). The MMA-co-BMA copolymer and the Karstedt catalyst in a mass ratio of 1:1 to 4:1 are added to 10 to 50 mL of organic solvent for dissolution. The resulting oil phase is dispersed in 50 to 100 mL of aqueous phase containing 0.5 to 5 wt% emulsifier and 0.5 to 5 wt% stabilizer. After emulsification and dispersion by mechanical stirring for 30 to 60 min, the resulting emulsion is kept at a constant heating temperature and mechanically stirred for 4 to 8 h until the oil phase evaporates completely.

[0013] The emulsifier is sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, Span 60 or Tween 80; the stabilizer is polyvinyl alcohol 17-92 or gelatin; and the organic solvent is dichloromethane or chloroform.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. The method for preparing the latent microencapsulated platinum catalyst provided by the present invention, wherein the microencapsulated platinum catalyst has no catalytic activity at room temperature, has a long storage time at room temperature, and has good compatibility with silicone rubber raw materials. It can be dispersed and sheared at high speed during processing. When the temperature is raised to 100°C, it has rapid catalytic activity and can be used for the preparation of low-temperature molding single-component addition-curing liquid silicone rubber.

[0016] 2. The microencapsulated platinum catalyst has a wall material composed of a random copolymer P (MMA-co-BMA) of methyl methacrylate and butyl methacrylate synthesized by atom transfer radical polymerization (ATRP). The softening point of the wall material can be controlled by changing the copolymerization ratio of the two, resulting in a faster thermal deformation reaction rate and higher curing efficiency when the specified temperature is reached. 3. The preparation method provided by this invention is simple, easy to control, and has stable yield and product performance. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the microcapsule platinum catalyst in Example 1 of the present invention;

[0018] Figure 2The infrared spectra of the microcapsule platinum catalyst in Example 1 (left) and Comparative Example 1 (right) of the present invention;

[0019] Figure 3 The results of thermogravimetric analysis (TGA) of the microcapsule platinum catalyst in Example 1 (left) and Comparative Example 1 (right) of this invention are shown. Detailed Implementation

[0020] The present invention will be further described below with reference to the embodiments.

[0021] The synthesis method of P(MMA-co-BMA) with a copolymerization ratio of 10:1: 10g of methyl methacrylate, 1.42g of butyl methacrylate, 0.1g of ethyl 2-bromoisobutyrate, 0.173g of N,N,N',N,N"-pentamethyldiethylenetriamine, and 16mL of toluene solvent were placed in a reaction flask. The flask was sealed, and the system was subjected to a freezing-vacuuming-thawing operation with liquid nitrogen three times. Then, nitrogen gas was introduced, and 0.143g of cuprous bromide was added through the top opening of the flask under nitrogen protection. The reaction flask was sealed, and vacuuming was continued for 2 minutes. After thawing, the system was heated in an oil bath at 110℃ for 12 hours. The reaction was then stopped by freezing with liquid nitrogen. The copper compounds were removed by filtration with alumina. The solution was concentrated using a rotary evaporator, and the solution was added dropwise to methanol to precipitate the product. The product was filtered and vacuumed to obtain the final white powder product.

[0022] The synthesis method of P(MMA-co-BMA) with a copolymerization ratio of 10:2: 20g of methyl methacrylate, 5.68g of butyl methacrylate, 0.2g of ethyl 2-bromoisobutyrate, 0.346g of N,N,N',N,N"-pentamethyldiethylenetriamine, and 30mL of toluene solvent were placed in a reaction flask. The flask was sealed, and the system was subjected to a freezing-vacuuming-thawing operation with liquid nitrogen three times. Then, nitrogen gas was introduced, and 0.286g of cuprous bromide was added through the top opening of the flask under nitrogen protection. The reaction flask was sealed, and vacuuming was continued for 2 minutes. After thawing, the system was heated in an oil bath at 110℃ for 16 hours. The reaction was then stopped by freezing with liquid nitrogen. The copper compounds were removed by filtration with alumina. The solution was concentrated using a rotary evaporator, and the solution was added dropwise to methanol to precipitate the product. The product was filtered and vacuumed to obtain the final white powder product.

[0023] The synthesis method of P(MMA-co-BMA) with a copolymerization ratio of 10:3: 15g of methyl methacrylate, 6.39g of butyl methacrylate, 0.15g of ethyl 2-bromoisobutyrate, 0.261g of N,N,N',N,N"-pentamethyldiethylenetriamine, and 25mL of toluene solvent were placed in a reaction flask. The flask was sealed, and the system was subjected to a freezing-vacuuming-thawing operation with liquid nitrogen three times. Then, nitrogen gas was introduced, and 0.215g of cuprous bromide was added through the top opening of the flask under nitrogen protection. The reaction flask was sealed, and vacuuming was continued for 2 minutes. After thawing, the system was heated in an oil bath at 110℃ for 12 hours. The reaction was then stopped by freezing with liquid nitrogen. The copper compounds were removed by filtration with alumina. The solution was concentrated using a rotary evaporator, and the solution was added dropwise to methanol to precipitate the product. The product was filtered and vacuumed to obtain the final white powder product.

[0024] The synthesis method of P(MMA-co-BMA) with a copolymerization ratio of 10:4: 10g of methyl methacrylate, 5.68g of butyl methacrylate, 0.1g of ethyl 2-bromoisobutyrate, 0.173g of N,N,N',N,N"-pentamethyldiethylenetriamine, and 16mL of toluene solvent were placed in a reaction flask. The flask was sealed, and the system was subjected to a freezing-vacuuming-thawing operation with liquid nitrogen three times. Then, nitrogen gas was introduced, and 0.143g of cuprous bromide was added through the top opening of the flask under nitrogen protection. The reaction flask was sealed, and vacuuming was continued for 2 minutes. After thawing, the system was heated in an oil bath at 110℃ for 12 hours. The reaction was then stopped by freezing with liquid nitrogen. The copper compounds were removed by filtration with alumina. The solution was concentrated using a rotary evaporator, and the solution was added dropwise to methanol to precipitate the product. The product was filtered and vacuumed to obtain the final white powder product.

[0025] Example 1: A microcapsule catalyst was prepared using P(MMA-co-BMA) with a copolymerization ratio of 10:1 as the wall material, sodium dodecyl sulfate as the emulsifier, dichloromethane as the solvent, and polyvinyl alcohol as the stabilizer.

[0026] 2 g of P(MMA-co-BMA) and 1 g of Karstedt catalyst were dissolved in 40 mL of dichloromethane. The resulting oil phase was added to 100 mL of an aqueous solution containing 1 wt% sodium dodecyl sulfate and 1 wt% polyvinyl alcohol 17-92. The mixture was dispersed at 1000 rpm for 1 h to form a homogeneous and stable emulsion. The emulsion was then placed in an oil bath at a constant temperature of 40 °C and stirred at 300 rpm for 4 h until the dichloromethane was completely evaporated. The emulsion was then centrifuged, washed five times with anhydrous ethanol, and dried in a vacuum drying oven at 40 °C for 24 h to obtain the product.

[0027] Figure 1The image shown is a scanning electron microscope image of the microcapsule platinum catalyst in Example 1 of this invention. It can be seen that the prepared microcapsule platinum catalyst has a complete morphology and distinct particles. The average particle size of the microcapsules is about 7 μm, and it has a distinct hollow structure.

[0028] Example 2: A microcapsule catalyst was prepared using P(MMA-co-BMA) with a copolymerization ratio of 10:2 as the wall material, sodium dodecyl sulfate as the emulsifier, dichloromethane as the solvent, and polyvinyl alcohol as the stabilizer.

[0029] 1 g of P(MMA-co-BMA) and 0.5 g of Karstedt catalyst were dissolved in 30 mL of dichloromethane. The resulting oil phase was added to 100 mL of an aqueous solution containing 2 wt% sodium dodecyl sulfate and 1 wt% polyvinyl alcohol 17-92. The mixture was dispersed under mechanical stirring at 1000 rpm for 1 h to form a homogeneous and stable emulsion. The resulting emulsion was then placed in an oil bath at a constant temperature of 40 °C and stirred at a mechanical stirring intensity of 300 rpm for 4 h until the dichloromethane was completely evaporated. The emulsion was then centrifuged, washed five times with anhydrous ethanol, and dried in a vacuum drying oven at 40 °C for 24 h to obtain the product.

[0030] Example 3: A microcapsule catalyst was prepared using P(MMA-co-BMA) with a copolymerization ratio of 10:3 as the wall material, sodium dodecylbenzenesulfonate as the emulsifier, chloroform as the solvent, and polyvinyl alcohol as the stabilizer.

[0031] 1 g of P(MMA-co-BMA) and 1 g of Karstedt catalyst were dissolved in 20 mL of chloroform. The resulting oil phase was added to 80 mL of an aqueous solution containing 3 wt% sodium dodecylbenzenesulfonate and 1 wt% polyvinyl alcohol 17-92. The mixture was dispersed at 1000 rpm for 1 h to form a homogeneous and stable emulsion. The emulsion was then placed in an oil bath at a constant temperature of 40 °C and stirred at 300 rpm for 4 h until the dichloromethane was completely evaporated. The emulsion was then centrifuged, washed five times with anhydrous ethanol, and dried in a vacuum drying oven at 40 °C for 24 h to obtain the product.

[0032] Example 4: A microcapsule catalyst was prepared using P(MMA-co-BMA) with a copolymerization ratio of 10:2 as the wall material, sodium dodecylbenzenesulfonate as the emulsifier, dichloromethane as the solvent, and gelatin as the stabilizer.

[0033] 2 g of P(MMA-co-BMA) and 1 g of Karstedt catalyst were dissolved in 40 mL of dichloromethane. The resulting oil phase was added to 100 mL of an aqueous solution containing 3 wt% sodium dodecylbenzenesulfonate and 0.5 wt% gelatin. The mixture was dispersed at 1000 rpm for 1 h to form a homogeneous and stable emulsion. The emulsion was then placed in an oil bath at a constant temperature of 62 °C and stirred at 300 rpm for 4 h until the chloroform was completely evaporated. The emulsion was then centrifuged, washed five times with anhydrous ethanol, and dried in a vacuum drying oven at 40 °C for 24 h to obtain the product.

[0034] Example 5: A microcapsule catalyst was prepared using P(MMA-co-BMA) with a copolymerization ratio of 10:1 as the wall material, sodium dodecylbenzenesulfonate as the emulsifier, chloroform as the solvent, and gelatin as the stabilizer.

[0035] 1 g of P(MMA-co-BMA) and 0.5 g of Karstedt catalyst were dissolved in 20 mL of chloroform. The resulting oil phase was added to 60 mL of an aqueous solution containing 2 wt% sodium dodecylbenzenesulfonate and 2 wt% gelatin. The mixture was dispersed at 600 rpm for 1 h to form a homogeneous and stable emulsion. The emulsion was then placed in an oil bath at a constant temperature of 62 °C and stirred at 400 rpm for 3 h until the chloroform was completely evaporated. The emulsion was then centrifuged, washed five times with anhydrous ethanol, and dried in a vacuum drying oven at 40 °C for 24 h to obtain the product.

[0036] Performance testing: 20g of vinyl silicone oil with a viscosity of 2000mPa.s, 2g of hydrogen-containing silicone oil with a hydrogen content of 0.36% and 0.1g of the product of the above example were mixed evenly using a high-speed homogenizer to obtain a one-component addition-type silicone rubber composition. The composition was stored at room temperature, and its latency and curing time of silicone rubber under heating at 100°C were observed.

[0037] Comparative Example 1: Microcapsule catalysts were prepared using PMMA wall material, sodium dodecyl sulfate as emulsifier, dichloromethane as solvent, and polyvinyl alcohol as stabilizer.

[0038] 2 g of PMMA and 1 g of Karstedt catalyst were dissolved in 40 mL of dichloromethane. The resulting oil phase was added to 100 mL of an aqueous solution containing 1 wt% sodium dodecyl sulfate and 1 wt% polyvinyl alcohol 17-92. The mixture was dispersed at 1000 rpm for 1 h to form a homogeneous and stable emulsion. The emulsion was then placed in an oil bath at a constant temperature of 40 °C and stirred at 300 rpm for 4 h until the dichloromethane was completely evaporated. The emulsion was then centrifuged, washed five times with anhydrous ethanol, and dried in a vacuum drying oven at 40 °C for 24 h to obtain the product.

[0039] 20g of vinyl silicone oil with a viscosity of 2000mPa.s, 2g of hydrogen-containing silicone oil with a hydrogen content of 0.36%, and 0.1g of PMMA were mixed evenly using a high-speed homogenizer to obtain a silicone rubber composition. The composition was stored at room temperature to observe whether it could cure and its room temperature latency.

[0040] Comparative Example 2: 20g of vinyl silicone oil with a viscosity of 2000mPa.s, 2g of hydrogen-containing silicone oil with a hydrogen content of 0.36% and 0.1g of P(MMA-co-BMA) with a copolymerization ratio of 10:1 were mixed evenly using a high-speed homogenizer to obtain a silicone rubber composition. The composition was stored at room temperature to observe whether it could cure and its room temperature latency.

[0041] Comparative Example 3: 20g of vinyl silicone oil with a viscosity of 2000mPa.s, 2g of hydrogen-containing silicone oil with a hydrogen content of 0.36, 0.05g of Karstedt catalyst and 0.1g of inhibitor were mixed evenly using a high-speed homogenizer to obtain a silicone rubber composition. The composition was stored at room temperature to observe whether it could cure and its room temperature latency.

[0042] The implementation effect of the experimental example:

[0043]

[0044] The experimental results above show that silicone rubber components with only P(MMA-co-BMA) added lack curing ability, while silicone rubber components with only Karstedt catalyst and inhibitor added undergo immediate curing and lack latent properties. Single-component silicone rubber components composed of P(MMA-co-BMA) and PMMA polymer wall materials encapsulating Karstedt catalyst in a copolymer ratio of 10:1-10:4 all exhibit latent properties. However, the microcapsule catalyst silicone rubber component prepared with PMMA wall material cannot be completely cured within 1 hour at 100℃, requiring 90 minutes of heating for complete curing. This is because the glass transition temperature and softening point of PMMA wall material are relatively high, making it difficult to release the internal catalyst during heating. In contrast, the copolymer P(MMA-co-BMA), due to the introduction of soft-chain polybutyl methacrylate into the polymethyl methacrylate segment, lowers the overall glass transition temperature of the polymer, allowing for faster curing and more complete curing at 100℃. Meanwhile, the implementation results from the experimental examples show that the microcapsule catalysts prepared by P(MMA-co-BMA) copolymers can achieve a latency of 10 weeks or more at room temperature, with the longest reaching 12 weeks, which is basically the same as the room temperature latency of microcapsule catalysts prepared by PMMA.

[0045] Figure 2The images show the infrared spectra of the microcapsule platinum catalysts in Example 1 (left) and Comparative Example 1 (right) of this invention. The successful synthesis of the microcapsule platinum catalyst was confirmed by observing the characteristic infrared peaks appearing in the core material (Karstedt catalyst), wall material (P(MMA-co-BMA) and PMMA), and the microcapsule as a whole.

[0046] Figure 3 The thermogravimetric analysis (TGA) results for the microencapsulated platinum catalysts in Example 1 (left) and Comparative Example 1 (right) of this invention are shown. The Karstedt catalyst mainly loses weight in the temperature range of 500-700°C, while P(MMA-co-BMA) and PMMA decompose at lower temperatures of 350-400°C. The thermal decomposition curves of the microencapsulated catalysts exhibit two distinct phases: the first phase occurs at 350-450°C, corresponding to the weight loss of P(MMA-co-BMA) and PMMA; the second phase occurs at 400-700°C, attributed to the thermal decomposition of the Karstedt catalyst. By evaluating the percentage of weight loss in the relevant segments of the TGA curves, the approximate content of the core material in the microencapsulated platinum catalyst can be calculated.

[0047] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A latent microencapsulated platinum catalyst characterized by: The core material is a silicon rubber curing agent Karstedt catalyst, and the wall material is a random copolymer of methyl methacrylate and butyl methacrylate prepared by atom transfer radical polymerization; The preparation method of the random copolymer of methyl methacrylate and butyl methacrylate comprises the following steps: placing methyl methacrylate, butyl methacrylate, ethyl 2-bromoisobutyrate, N,N,N',N,N"-pentamethyldiethylenetriamine and toluene solvent in a reaction bottle, sealing the bottle, and repeating the freezing-vacuumizing-thawing operation three times, then passing nitrogen, adding cuprous bromide through the opening of the bottle under nitrogen protection, sealing the reaction bottle and continuing to vacuumize for 2 min, thawing the system and placing it in an oil bath at 110℃ for heating for 12 h; then stopping the reaction by freezing with liquid nitrogen, removing the copper compounds by filtration with aluminum oxide, concentrating the solution by a rotary evaporator, then dropping the solution into methanol to precipitate the product, filtering and vacuumizing, and the final white powder product is obtained; The molar ratio of methyl methacrylate and butyl methacrylate is 10: (1-4); the molar ratio of methyl methacrylate, ethyl 2-bromoisobutyrate, N,N,N',N,N"-pentamethyldiethylenetriamine and cuprous bromide is (100-300):(1-4):(1:4):(1-3), and the amount of toluene solvent used is 10-50 mL.

2. The latent microencapsulated platinum catalyst according to claim 1, wherein: The microcapsule is a white solid powder in macroscopic view, and the smooth microcapsule has a particle size of 1-30 μm.

3. The latent microencapsulated platinum catalyst according to claim 1, wherein: The core material accounts for 10-40% of the mass of the entire microcapsule.

4. A process for the preparation of the latent microencapsulated platinum catalyst according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: The wall material copolymer and Karstedt catalyst with a mass ratio of 1:1-4:1 are added to 10-50 mL of an organic solvent for dissolution, the obtained oil phase is dispersed into 50-100 mL of an aqueous phase containing 0.5-5 wt% of an emulsifier and 0.5-5 wt% of a stabilizer, mechanical stirring and emulsification are performed for 30-60 min, then the obtained emulsion is kept at the same heating temperature, and mechanical stirring is performed for 4-8 h until the oil phase is almost volatilized.

5. The method of claim 4, wherein: The organic solvent is dichloromethane or chloroform.

6. The method of claim 5, wherein: The emulsifier is one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, Span 60 or Tween 80; and the stabilizer is polyvinyl alcohol 17-92 or gelatin.

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