Environment-friendly and low-exudation triacetate cellulose film and preparation method thereof

Abstract

An environmentally friendly, low-leaching cellulose triacetate (TAC) membrane comprises a three-layer or higher laminated structure. The raw materials include cellulose, plasticizer, leaching-resistant UV absorber, leaching-prone UV absorber, and organic solvent. The preparation method is as follows: S1, preparing a steel strip layer, an intermediate layer, and an air layer for the TAC membrane, forming corresponding sizing solutions; S2, extruding the three-layer sizing solutions and evenly spreading them onto a stainless steel strip to form a liquid film, which is then formed through multi-layer casting. The liquid film is placed in a drying oven for preliminary drying, and when its moisture content reaches 25 wt%, it is peeled off from the steel strip and enters the transition and post-drying stages; S3, edge trimming, balancing, embossing, and winding yield the TAC membrane. This invention employs a multi-layered, differentiated layout of UV absorbers and precise process control, significantly reducing UV absorber leaching; it uses an environmentally friendly UV absorber system with low halogen content; the raw materials are readily available and low-cost; the process is compatible with existing production lines and is easy to mass-produce.

Description

Technical Field

[0001] This invention belongs to the field of cellulose triacetate film technology, specifically relating to an environmentally friendly, low-permeation cellulose triacetate film and its preparation method. Background Technology

[0002] Cellulose triacetate (TAC) film is widely used in polarizers due to its excellent optical, mechanical, and processing properties. Polarizers are made by multi-layering TAC and PVA films. Polarizers have diverse applications, including as protective films for liquid crystal displays and in the manufacture of polarized sunglasses, polarized sun hats, and other products.

[0003] Polarized sunglasses TAC films can be categorized by function into colored TAC films, UV-protective TAC films, and blue-light-blocking TAC films, among which UV-protective TAC films are the most basic and crucial material. Ultraviolet radiation is generally classified into UVA, UVB, and UVC bands based on absorption wavelength. UVA bands can cause cataracts and are widely used in polarized sunglasses TAC films. UVB bands primarily serve as skin protection, while UVC bands are largely absorbed by the ozone layer and rarely reach the Earth's surface. Therefore, polarized sun hats need to absorb both UVA and UVB bands, often requiring a large amount during use. This can cause UV absorbers to leach out, accumulating on the surface of the TAC film and the production system, affecting product quality.

[0004] The invention patent with publication number CN119866461A points out that due to excessive UV addition, precipitation is severe in 60μm membranes. Using UV absorbers with an oxazole structure and sulfur content can reduce precipitation while protecting UV absorbers such as benzotriazole, triazine, and benzophenone. However, oxazole-structured UV absorbers are expensive and virtually unavailable in the domestic market, hindering their widespread application in TAC membranes. Furthermore, commercially available UV absorbers primarily absorb UVA bands with limited protection against UVB bands, or TAC membranes that combine both UV and UV absorption properties often require excessive amounts of UV absorbers. After adding large amounts, the UV absorber has poor permeability in TAC membranes. Furthermore, with the continuous tightening of global environmental control requirements, the EU has further upgraded its regulatory standards for prohibited substances in products. Benzotriazole UV absorbers such as UV326, UV327, UV328, and UV329 have all been included in the list of prohibited substances, gradually reducing the number of UV absorbers suitable for TAC membranes. Current technical methods mainly focus on the protection of UV absorbers and cellulose modification in TAC membranes. The raw material structure is complex, making it difficult to achieve absorption of the full UV spectrum and permeation resistance in TAC membranes, and industrial production is also quite difficult. Summary of the Invention

[0005] To address the problems raised in the background technology, this invention studies and designs an environmentally friendly, low-permeation cellulose triacetate membrane and its preparation method. The purpose is to provide an environmentally friendly, low-permeation cellulose triacetate membrane with a halogen content ≤500ppm, a prohibited substance content below the detection limit, <3 precipitation strips on the TAC membrane surface, and an oily or solid permeation of less than 5mg / ㎡*7 days on the guide shaft surface, and its preparation method.

[0006] The technical solution of this invention: An environmentally friendly, low-permeation cellulose triacetate membrane comprises a laminated structure of three or more layers. The raw materials for preparing the cellulose triacetate membrane include: cellulose, plasticizer, leaching-resistant ultraviolet absorber, leaching-prone ultraviolet absorber, and organic solvent.

[0007] Preferably, the laminated structure is a three-layer structure, consisting of a steel strip layer, an intermediate layer, and an air layer, which together form a uniform and transparent cellulose triacetate film through the action of multi-layer casting.

[0008] Preferably, the cellulose has an acetyl substitution degree of 60.1%, a degree of polymerization of 295, is purchased from Sichuan Push Cellulose Acetate Co., Ltd., model number H12590, and has a cellulose binding acid content of 59.0%-62.5%.

[0009] Preferably, the amount of cellulose is 85-99 parts, and the amount of plasticizer is 1-15 parts. The plasticizer is a phthalate, a citrate, or a polyester polyol.

[0010] Preferably, the easily exudable ultraviolet absorber is added to the middle layer of the cellulose triacetate membrane at an amount of 0.5%-5.0%.

[0011] Preferably, the efflorescence-resistant ultraviolet absorber is added to at least the steel strip layer and the air layer, with an addition amount of 0.5%-2.0%.

[0012] Preferably, the organic solvent is a mixture of dichloromethane and methanol in a weight ratio of 95:5. The amount of organic solvent added ensures that the cellulose, plasticizer, leaching-resistant ultraviolet absorber, and leaching-easy ultraviolet absorber in the raw materials are mixed evenly, and the solid content of the mixture is 15wt%-22wt%.

[0013] Preferably, the easily exudable ultraviolet absorber is a high-efficiency, environmentally friendly, liquid, low-melting-point ultraviolet absorber with a melting point below 50°C and primarily absorbing ultraviolet rays in the 280nm-340nm range, mainly absorbing UVB wavelengths. This ultraviolet absorber has good biocompatibility with the human body. The easily exudable ultraviolet absorber is one or a combination of ethylhexyl salicylate, octocrylene, ethylhexyl methoxycinnamate, homosalyl ester, and 2-hydroxy-4-n-octyloxybenzophenone.

[0014] Preferably, the efflorescence-resistant ultraviolet absorber is one or more of 2,2'-methylenebis(4-tert-octyl-6-benzotriazole phenol), 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole, and avobenzone.

[0015] A method for preparing an environmentally friendly, low-permeation cellulose triacetate membrane is as follows: S1. Prepare the steel strip layer, intermediate layer and air layer of the cellulose triacetate membrane to form the corresponding cotton glue solution; S2. After the three layers of cotton glue solution (steel strip layer, intermediate layer, and air layer) are extruded, they are evenly spread onto the stainless steel strip to form a liquid film. The liquid film is formed by multi-layer casting. The liquid film is placed in a drying oven for preliminary drying. When its moisture content is 25wt%, it is peeled off from the steel strip and enters the transition section and post-drying section. S3. Trimming, balancing, embossing, and winding yields a cellulose triacetate film, ensuring that the moisture content of the final cellulose triacetate film is reduced to below 2.5 wt%.

[0016] Preferably, the preparation method of the triacetate cellulose ester membrane steel strip layer and air layer in S1 is as follows: a mixed solvent is added to the reaction vessel, that is, a mixed solvent prepared by cellulose, plasticizer, leaching-resistant ultraviolet absorber, dichloromethane and methanol is added under stirring at a speed of 50-100 rpm to obtain cotton glue solution a.

[0017] Preferably, the leaching-resistant ultraviolet absorber is added in two ways: at the source, that is, after dissolving in the above-mentioned reactor, it is added at the source to obtain the corresponding cotton glue solution for the steel strip layer and the air layer; or online, that is, the leaching-resistant ultraviolet absorber is added with some plasticizer, cotton glue and other viscosity modifiers through online pipeline and added together with the main material through a static mixer to obtain the corresponding cotton glue solution for the steel strip layer and the air layer.

[0018] Preferably, the preparation method of the cellulose triacetate membrane intermediate layer in S1 is as follows: an organic solvent is added to a reaction vessel, and cellulose and plasticizer are added and mixed under stirring at 50-100 rpm to obtain the corresponding cotton glue solution for the intermediate layer, namely cotton glue solution b; Preferably, the easily exudable ultraviolet absorber is added in the following manner: the easily exudable ultraviolet absorber and the main cotton glue solution b are added online separately through a static mixer, or the easily exudable ultraviolet absorber is premixed with a portion of the diluted cotton glue solution b and the plasticizer to obtain a premixed liquid, and the premixed liquid is added online together with the main cotton glue solution b through a static mixer to improve the mixing efficiency of the easily exudable ultraviolet absorber and the main cotton glue solution b.

[0019] Preferably, the total thickness of the cellulose triacetate membrane is 80μm-300μm, the thickness of the intermediate layer accounts for 50% or more of the total thickness, the thickness of the steel strip layer and the air layer are the same or different, and the thickness of the steel strip layer and the air layer accounts for 10%-40% of the total thickness of the TAC membrane, respectively.

[0020] The cotton glue solution described in this application is a homogeneous solution formed by dissolving cellulose triacetate in an organic solvent.

[0021] The beneficial effects of this invention are as follows: This invention employs a multi-layered, differentiated layout of UV absorbers, coupled with precise control of corresponding process parameters. The resulting cellulose triacetate membrane exhibits fewer than 3 surface precipitates, and the amount of oily or solid permeate on the guide shaft surface is less than 5 mg / m² * 7 days. This effectively ensures the shielding effect of UVA and UVB band UV absorbers while significantly reducing UV absorber precipitation, thus solving the problem of product quality degradation caused by precipitation. The use of an environmentally friendly UV absorber system results in cellulose triacetate membranes with halogen content ≤ 500 ppm and prohibited substance content below the detection limit, meeting increasingly stringent global environmental regulatory requirements and broadening the product's application and market scope. It abandons the expensive and domestically unavailable oxazole-structured UV absorbers, opting instead for conventional environmentally friendly absorbers. The simple formulation requires no complex modification, significantly reducing raw material costs and making it suitable for large-scale application. The multi-layer casting process is easy to operate, requiring no major modifications to existing production lines. The process parameters are easily controllable and highly reproducible, overcoming the shortcomings of traditional technologies such as complex raw material structures and difficulties in industrial production, making it suitable for large-scale industrial production. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the cellulose triacetate membrane in this invention.

[0023] The structure consists of: 1. steel strip layer, 2. intermediate layer, and 3. air layer. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] The cellulose triacetate membrane in this embodiment of the invention comprises a three-layer structure, consisting of a steel strip layer 1, an intermediate layer 2, and an air layer 3. The steel strip layer 1, the air layer 3, and the intermediate layer 2 form a uniform and transparent cellulose triacetate membrane through multilayer casting.

[0026] Example 1 Cellulose triacetate: 90 parts Plasticizer: 5 parts sucrose benzoate Effusion-resistant UV absorber: 1 part of 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol) Easily exudable UV absorbers: 2 parts ethylhexyl salicylate, 2 parts octocrylene Ethylhexyl salicylate and octocrylene, which are easily exuded ultraviolet absorbers, are added together with the main cotton adhesive solution b through a static mixer to prepare an intermediate layer. The exudation-resistant ultraviolet absorber 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol) is added at the source to form the corresponding steel strip layer and air layer (added on the steel strip surface and air surface respectively). After the three layers of cotton adhesive solution (steel strip layer, intermediate layer, and air layer) are extruded, they are evenly spread on the stainless steel strip to form a liquid film. The liquid film is formed by multi-layer casting. The liquid film is placed in a drying oven for preliminary drying. When its moisture content is 25wt%, it is peeled off from the steel strip and enters the transition section and post-drying section. Edge trimming, balancing, embossing, and winding are performed to obtain a cellulose triacetate film. Finally, the moisture content of the cellulose triacetate film is reduced to below 2.5wt%.

[0027] The intermediate layer accounts for 60% of the total thickness of the TAC membrane, the steel strip layer accounts for 20% of the thickness of the TAC membrane, and the air layer accounts for 20% of the thickness of the TAC membrane.

[0028] The organic solvent used is a mixture of dichloromethane and methanol in a mass ratio of 95:5, which accounts for 85 parts in the cotton glue solution system.

[0029] Example 2 Cellulose triacetate: 88 parts Plasticizer: 8 parts triethylene glycol diisooctanoate Effusion-resistant UV absorber: Avobenzone 1.0 part Easily exudable ultraviolet absorber: 1.5 parts of homosalate and 1.5 parts of 2-hydroxy-4-n-octyloxybenzophenone.

[0030] Easily exuding UV absorbers, such as homosalate and 2-hydroxy-4-n-octyloxybenzophenone, are added together with the main cotton glue solution through a static mixer to prepare an intermediate layer. Eluent-resistant UV absorbers, such as avobenzone, are added at the source to form corresponding steel strip layers and air layers (added on the steel strip surface and air surface respectively). The three layers of cotton glue solution—steel strip layer, intermediate layer, and air layer—are extruded and evenly spread onto a stainless steel strip to form a liquid film. This liquid film is formed through multi-layer casting and is initially dried in a drying oven. When its moisture content reaches 25 wt%, it is peeled off from the steel strip and enters the transition and post-drying stages. Edge trimming, balancing, embossing, and winding yield a cellulose triacetate film. Finally, the moisture content of the cellulose triacetate film is reduced to below 2.5 wt%.

[0031] The intermediate layer accounts for 80% of the total thickness of the TAC membrane, the steel strip layer accounts for 10% of the thickness of the TAC membrane, and the air layer accounts for 10% of the thickness of the TAC membrane.

[0032] The organic solvent used is a mixture of dichloromethane and methanol in a mass ratio of 95:5, which accounts for 80 parts in the cotton glue solution system.

[0033] Example 3 Cellulose triacetate: 90 parts Plasticizers: 2.5 parts sucrose benzoate, 2.5 parts triethylene glycol diisooctanoate Effusion-resistant UV absorber: 1.5 parts of 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole Easily exudable ultraviolet absorber: 1.5 parts ethylhexyl salicylate, 2.0 parts homosalate.

[0034] Easily exudable UV absorbers: Ethylhexyl salicylate, homosalate, and the main cotton swab solution are added together to prepare the intermediate layer; the exudable UV absorber 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole is added at the source on both the steel strip and air surfaces to form corresponding steel strip and air layers (added on the steel strip and air surfaces respectively). After the three layers of cotton swab solution (steel strip, intermediate layer, and air layer) are extruded, they are evenly spread onto the stainless steel strip to form a liquid film. The liquid film is formed by multi-layer casting and is placed in a drying oven for preliminary drying. When its moisture content is 25wt%, it is peeled off from the steel strip and enters the transition section and post-drying section; edge trimming, balancing, embossing, and winding are performed to obtain the cellulose triacetate film. Finally, the moisture content of the cellulose triacetate film is reduced to below 2.5wt%.

[0035] The intermediate layer accounts for 70% of the total thickness of the TAC membrane, the steel strip layer accounts for 15% of the TAC membrane thickness, and the air layer accounts for 15% of the TAC membrane thickness.

[0036] The organic solvent used is a mixture of dichloromethane and methanol in a mass ratio of 95:5, which accounts for 80 parts in the cotton glue solution system.

[0037] Comparative Example 1 Cellulose triacetate: 92 parts Plasticizer: Triphenyl phosphate 5.0 parts UV absorber: 2 parts of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 1 part of 2-[2-hydroxy-3,5-bis(1,1-dimethylpropylphenyl)]-2H-benzotriazole.

[0038] The above formula is added at the source to prepare a uniform cotton glue solution, which is then cast in a single layer on a steel belt, dried, wound up, and formed into a film.

[0039] Comparative Example 2 Cellulose triacetate: 90 parts Plasticizers: Triphenyl phosphate 3.5 parts, Triethylene glycol diisooctanoate 2.5 parts UV absorber: 4 parts of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole.

[0040] The above formula is added at the source to prepare a uniform cotton glue solution, which is then cast, dried, wound, and film-formed on a steel belt.

[0041] Comparative Example 3 Cellulose triacetate: 92 parts Plasticizers: 2.0 parts triethylene glycol diisooctyl ester, 3.0 parts trioctyl citrate UV absorber: 3 parts of 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole.

[0042] The above formula is added at the source to prepare a uniform cotton glue solution, which is then cast, dried, wound, and film-formed on a steel belt.

[0043] The performance of the TAC membranes prepared in Examples 1-3 and Comparative Examples 1-3 was tested, and the test results are shown in Table 1.

[0044] The performance characterization test method is as follows: 1. Deposition lines on the surface of the TAC membrane: The observation was conducted through online inspection, with the number of TAC film rolls being 1000m. The test environment temperature was 25-30℃ and the humidity was 40%-60%.

[0045] 2. Oily precipitation: To determine whether the exudate is oily or solid, after 7 days of operation of the TAC membrane, a layer of oil-absorbing paper, degreased cotton, or other medium (or a certain amount of polar solvent) is applied evenly to the guide shaft with severe exudation. The content of oily and solid exudates adhering to the guide shaft after 7 days of operation is then tested using the weight gain method.

[0046] 3. Halogen value test The halogen value of the TAC membrane was tested using X-ray fluorescence spectrometry. The TAC membrane used for testing was composed of multiple layers stacked together, and the total thickness of the TAC membrane was greater than 2.0 cm. The total halogen content was also tested.

[0047] Table 1. Performance test results of TAC membranes prepared in Examples 1-3 and Comparative Examples 1-3 The production process of this invention is simple. The cellulose triacetate membrane adopts a multi-layer structure, and the raw material formulation of the cellulose triacetate membrane uses a novel environmentally friendly UV absorber, which is not only low in cost but also effectively ensures the shielding effect of UVA and UVB band ultraviolet absorbers, while significantly reducing the precipitation of UV absorbers, making it suitable for industrial production. As shown in Table 1, the halogen content of the cellulose triacetate membrane prepared by this invention is ≤500ppm, and the content of prohibited substances is 0. In contrast, the halogen values ​​of Comparative Examples 1-3 are significantly higher due to the presence of halogen-based ultraviolet absorbers, and the content of prohibited substances is also high. In the precipitation experiment of the cellulose triacetate membrane prepared by this invention, the number of precipitation lines on the surface of the cellulose triacetate membrane is <3, and the amount of oily and solid substances on the guide shaft surface is less than 5mg / ㎡*7 days. In contrast, the number of precipitation lines on the surface of the cellulose triacetate membrane in Comparative Examples 1-3 is >3, and the amount of oily and solid substances on the guide shaft surface is ≥15 mg / ㎡*7 days.

Claims

1. An environmentally friendly, low-permeation cellulose triacetate membrane, characterized in that: The cellulose triacetate membrane comprises a laminated structure with three or more layers. The raw materials for its preparation include: cellulose, plasticizer, leaching-resistant ultraviolet absorber, leaching-easy ultraviolet absorber, and organic solvent.

2. The environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 1, characterized in that: The laminated structure is a three-layer structure, consisting of a steel strip layer, an intermediate layer, and an air layer. The steel strip layer, air layer, and intermediate layer form a uniform and transparent cellulose triacetate film through multi-layer casting. The total thickness of the cellulose triacetate film is 80μm-300μm. The thickness of the intermediate layer accounts for 50% or more of the total thickness. The thickness of the steel strip layer and the air layer may be the same or different. The thickness of the steel strip layer and the air layer each account for 10%-40% of the total thickness of the cellulose triacetate film.

3. The environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 1, characterized in that: The cellulose has an acetyl substitution degree of 60.1%, a degree of polymerization of 295, and a cellulose bound acid content of 59.0%-62.5%, with the amount of cellulose used being 85-99 parts; the plasticizer is 1-15 parts, and the plasticizer is a phthalate, citrate, or polyester polyol; the organic solvent is a mixture of dichloromethane and methanol in a weight ratio of 95:5, and the amount of organic solvent added ensures that the cellulose, plasticizer, leaching-resistant ultraviolet absorber, and leaching-easy ultraviolet absorber in the raw materials are mixed evenly, and the solid content of the mixture is 15wt%-22wt%.

4. The environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 2, characterized in that: The easily exudable ultraviolet absorber is added to the middle layer of the cellulose triacetate membrane at a concentration of 0.5%-5.0%; the resistant ultraviolet absorber is added to at least the steel strip layer and the air layer at a concentration of 0.5%-2.0%.

5. The environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 1, characterized in that: The easily exudable ultraviolet absorber is a highly efficient, environmentally friendly absorber with a melting point below 50℃, primarily absorbing ultraviolet rays in the 280nm-340nm range, mainly absorbing UVB wavelengths. It is a liquid, low-melting-point ultraviolet absorber. The easily exudable ultraviolet absorber is one or more of the following: ethylhexyl salicylate, octocrylene, ethylhexyl methoxycinnamate, homosalyl ester, and 2-hydroxy-4-n-octyloxybenzophenone. The resistant to exudation ultraviolet absorber is one or more of the following: 2,2'-methylenebis(4-tert-octyl-6-benzotriazolephenol), 2-(2'-hydroxy-3',5'-dicumylphenyl)benzotriazole, and avobenzone.

6. A method for preparing an environmentally friendly, low-permeation cellulose triacetate membrane, characterized in that: Includes the following steps: S1. Prepare the steel strip layer, intermediate layer and air layer of the cellulose triacetate membrane to form the corresponding cotton glue solution; S2. After the three layers of cotton glue solution (steel strip layer, intermediate layer, and air layer) are extruded, they are evenly spread onto the stainless steel strip to form a liquid film. The liquid film is formed by multi-layer casting. The liquid film is placed in a drying oven for preliminary drying. When its moisture content is 25wt%, it is peeled off from the steel strip and enters the transition section and post-drying section. S3. Trimming, balancing, embossing, and winding yields a cellulose triacetate film, ensuring that the moisture content of the final cellulose triacetate film is reduced to below 2.5 wt%.

7. The method for preparing an environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 6, characterized in that: The preparation method of the triacetate cellulose ester membrane steel strip layer and air layer in S1 is as follows: a mixed solvent is added to the reaction vessel, that is, a mixed solvent prepared by adding cellulose, plasticizer, leaching-resistant ultraviolet absorber, dichloromethane and methanol is added under stirring at a speed of 50-100 rpm to obtain cotton glue solution a.

8. The method for preparing an environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 7, characterized in that: There are two ways to add the leaching-resistant ultraviolet absorber: source addition, that is, after dissolving in the above-mentioned reactor, it is added at the source to obtain the corresponding cotton glue solution for the steel strip layer and air layer; or online addition, that is, the leaching-resistant ultraviolet absorber is added with a portion of plasticizer and cotton glue through online pipeline addition, and is added together with the main material through a static mixer to obtain the corresponding cotton glue solution for the steel strip layer and air layer.

9. The method for preparing an environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 6, characterized in that: The preparation method of the intermediate layer of the cellulose triacetate membrane in S1 is as follows: add organic solvent to the reaction vessel, add cellulose and plasticizer under stirring at 50-100 rpm to prepare the corresponding cotton glue solution for the intermediate layer, namely cotton glue solution b.

10. The method for preparing an environmentally friendly, low-permeation cellulose triacetate membrane as described in claim 9, characterized in that: The method of adding the easily exudable ultraviolet absorber is as follows: the easily exudable ultraviolet absorber and the above-mentioned main cotton glue solution b are added online separately through a static mixer, or the easily exudable ultraviolet absorber, a portion of the diluted cotton glue solution b, and the plasticizer are premixed to obtain a premixed liquid, and the premixed liquid and the main cotton glue solution b are added online through a static mixer to improve the mixing efficiency of the easily exudable ultraviolet absorber and the main cotton glue solution b.

Images