Full-biodegradable mulching film for corn for seed production and preparation method of full-biodegradable mulching film

Abstract

The invention relates to the technical field of high polymer materials, and discloses a fully biodegradable mulching film for corn for seed production and a preparation method thereof, the fully biodegradable mulching film comprises the following components by weight: 65-75 parts of polylactic acid, 4-6 parts of modified polyester, 8-12 parts of biomass charcoal, 2-3 parts of acetyl tributyl citrate, and 0.4-0.5 part of an antioxidant 1010; the preparation method of the modified polyester comprises the following steps: synthesizing an intermediate 1 by taking 2-hydroxyadipaldehyde and hydroxylamine hydrochloride as raw materials, and then esterifying, oxidizing and curing to obtain the modified polyester. The full-biodegradable mulching film for the corn for seed production has relatively good tensile property and degradable effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high molecular materials, in particular to a kind of full biodegradable mulching film for seed corn and preparation method thereof. BACKGROUND

[0002] In the field of agricultural production, mulching film covering technology can effectively improve soil temperature, reduce soil water evaporation and inhibit weed growth, thereby increasing grain yield, and has become a key technical means in the process of seed corn planting. Traditional mulching film is mostly made of non-degradable high molecular materials such as polyethylene. Such mulching film is difficult to decompose in the natural environment after completing the use cycle, and will remain in the soil for a long time, forming "white pollution". However, most mulching films are made of polyethylene and polypropylene materials. Non-degradable plastics have a huge threat to the ecological environment and human survival. The synthesis of biomass-based composite materials from natural biomass waste has attracted much attention. To solve the pollution problem of traditional mulching film, the market mulching film made of single polylactic acid has biodegradability, but its brittleness is high, the tensile resistance is poor, and it is easy to break due to external force during use. It cannot provide stable protection for the whole growth period of seed corn. Therefore, developing a full biodegradable mulching film with excellent mechanical properties, controllable degradation rate and suitable for the growth characteristics of seed corn is the key to solving the problem. SUMMARY

[0003] Technical problems to be solved In view of the defects of the prior art, the present application provides a full biodegradable mulching film for seed corn and a preparation method thereof, which has good degradability and tensile effect.

[0004] Technical scheme

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a full biodegradable mulching film for seed corn, comprising the following components by weight: 65-75 parts by weight of polylactic acid, 4-6 parts by weight of modified polyester, 8-12 parts by weight of biomass charcoal, 2-3 parts by weight of acetyl citric acid tributyl ester, 0.4-0.5 parts by weight of antioxidant 1010. The preparation method of the modified polyester is as follows: 2-hydroxyhexanedial and hydroxylamine hydrochloride are used as raw materials to synthesize intermediate 1, and then esterification, oxidation and curing are carried out to obtain the modified polyester.

[0006] Further, the preparation method of the modified polyester is as follows: S1. Add 2-hydroxyhexanedialdehyde, hydroxylamine hydrochloride, and potassium carbonate to 90-100 mL of 75% (v / v) aqueous ethanol solution. Stir at room temperature until no carbon dioxide is released, then magnetically stir for 4-6 h. After the reaction is complete, remove the solvent by rotary evaporation. Dissolve the crude product in 90-100 mL of distilled water and heat to 55-60 °C. Cool and filter, then vacuum dry at 75-80 °C for 20-25 h. After the reaction is complete, intermediate 1 is obtained. S2. Add intermediate 1 and linoleic acid to a reaction flask containing N,N-dimethylformamide solvent, stir and mix, continue to add p-toluenesulfonic acid catalyst, react at 80-90℃ for 7-8h, after which add 1mol / L sodium hydroxide solution to adjust pH to neutral, distill under reduced pressure, wash, dry, and obtain trioleate compound. S3. Add the trioleate compound, strong acid cation exchange resin, and acetic acid to a reaction flask containing N,N-dimethylformamide solvent, heat to 55-60℃, slowly add hydrogen peroxide, react for 6-8 hours, distill under reduced pressure after the reaction is completed, wash, and dry to obtain epoxy intermediate 2. S4. Add 3,3'-dithiodipropionic acid to epoxy intermediate 2, heat to 150-155℃, then cool, and continue to add 4-methylhexahydrophthalic anhydride and triethanolamine. Mix evenly, cure at 110-120℃ for 1-2 hours, cure at 120-140℃ for 1-2 hours, and vacuum dry to obtain modified polyester.

[0007] Furthermore, in S1, the ratio of 2-hydroxyhexanedialdehyde, hydroxylamine hydrochloride, and potassium carbonate is 12-16 mmol: 30-40 mmol: 3.12-3.15 g.

[0008] Furthermore, in S2, the ratio of intermediate 1, linoleic acid, and p-toluenesulfonic acid catalyst is 14-16 mmol: 45-50 mmol: 0.01-0.02 g.

[0009] Furthermore, in S3, the ratio of trioleate compound, strong acid cation exchange resin, acetic acid, and hydrogen peroxide is 12-15 mmol: 0.03-0.04 g: 0.11-0.12 g: 14-18 g.

[0010] Further, in S4, the ratio of 3,3'-dithiodipropionic acid, epoxy intermediate 2,4-methylhexahydrophthalic anhydride, and triethanolamine is 10-12 mmol: 10-15 mmol: 10-15 mmol: 0.04-0.05 mmol.

[0011] Furthermore, the cooling temperature in S4 is 85-90°C.

[0012] Furthermore, the preparation method of the fully biodegradable mulch film for seed corn is as follows: polylactic acid, modified polyester, biochar, tributyl acetylacetate, and antioxidant 1010 are added to a high-speed mixer and mixed at 120-130℃ for 16-20 minutes to obtain a mixture; the mixture is fed into a twin-screw extruder for granulation, the extrusion temperature is controlled at 160-180℃, and the screw speed is 30-50 r / min to obtain masterbatch; the masterbatch is fed into a blown film machine, the blown film temperature is set at 150-170℃, and a mulch film with a thickness of 0.012-0.015 mm is produced.

[0013] Beneficial technical effects The mulch film of this invention uses polylactic acid as the main base material, compounded with modified polyester and biochar biodegradable components, realizing the biodegradability of the material. After the seed corn is harvested, the mulch film can gradually decompose into carbon dioxide and water in the natural environment. The biochar is made from biomass raw materials such as crop straw, sawdust, manure and agricultural and forestry waste. After degradation, there are no toxic or harmful substances left behind, solving the problem of "white pollution" of soil caused by traditional polyethylene mulch film. Long-term use can improve soil structure, maintain the soil ecological balance in the seed corn planting area, and conform to the concept of green and sustainable agricultural development.

[0014] In the reaction steps of the modified polyester, the trioleate compound is oxidized to obtain epoxy intermediate 2, and then 3,3'-dithiodipropionic acid and 4-methylhexahydrophthalic anhydride are introduced to obtain the modified polyester. The introduced dynamic disulfide bond can effectively promote the degradation of epoxy resin through "low bond energy easy breakage and dynamic exchange promoting decomposition", which solves the problem of difficult degradation of traditional epoxy resin.

[0015] The introduction of modified polyester effectively improves the brittleness of polylactic acid. The molecular chains in the modified polyester cross-link with the polylactic acid molecular chains, while the flexible segments contained in it (such as the long-chain structure of linoleic acid) can enhance the toughness of the material. On the other hand, the addition of biochar not only provides good rigid support for the mulch film, but also disperses evenly in the substrate, reduces stress concentration, and further improves the tensile properties of the material. Attached Figure Description

[0016] Figure 1 This is the reaction route of the trioleate compound in Example 1. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific embodiments.

[0019] Hydroxylamine hydrochloride, Shanghai Titan Technology Co., Ltd. Strong acid cation exchange resin: Type 732 strong acid styrene cation exchange resin. Polylactic acid has a number-average molecular weight of 50,000 Da and an intrinsic viscosity of 0.7 dL / g, operating conditions: 25℃. Biochar, Henan Straw Charcoal Industry. Acetic acid mass fraction 3%, hydrogen peroxide mass fraction 60%.

[0020] Example 1

[0021] A method for preparing a fully biodegradable mulch film for seed corn production is as follows: S1. 12 mmol of 2-hydroxyhexanedialdehyde, 30 mmol of hydroxylamine hydrochloride and 3.12 g of potassium carbonate were added to 90 mL of 75% ethanol aqueous solution. The mixture was stirred at room temperature until no carbon dioxide was released. The mixture was then magnetically stirred for 4 h. After the reaction was completed, the solvent was removed by rotary evaporation. The crude product was dissolved in 90 mL of distilled water and heated to 55 °C. The mixture was then cooled and filtered. The product was then vacuum dried at 75 °C for 20 h. After the reaction was completed, intermediate 1 was obtained. S2. Add 14 mmol of intermediate 1 and 45 mmol of linoleic acid to a reaction flask containing 50 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.01 g of p-toluenesulfonic acid catalyst, and react at 80 °C for 7 h. After the reaction is completed, add 1 mol / L sodium hydroxide solution to adjust the pH to neutral, distill under reduced pressure, wash, and dry to obtain the trioleate compound. S3. Add 12 mmol of trioleate compound, 0.03 g of strong acid cation exchange resin and 0.11 g of acetic acid to a reaction flask containing 50 mL of N,N-dimethylformamide solvent, heat to 55 °C, slowly add 14 g of hydrogen peroxide, react for 6 h, distill under reduced pressure after the reaction is completed, wash and dry to obtain epoxy intermediate 2. S4. Add 10 mmol of 3,3'-dithiodipropionic acid to 10 mmol of epoxy intermediate 2, heat to 150°C, then cool to 85°C, add 10 mmol of 4-methylhexahydrophthalic anhydride and 0.04 mmol of triethanolamine, mix well, cure at 110°C for 1 h, cure at 120°C for 1 h, and vacuum dry to obtain modified polyester. S5. Add 65 parts by weight of polylactic acid, 4 parts by weight of modified polyester, 8 parts by weight of biochar, 2 parts by weight of tributyl acetylacetic acid, and 0.4 parts by weight of antioxidant 1010 to a high-speed mixer and mix at 120°C for 16 minutes to obtain a mixture. Feed the mixture into a twin-screw extruder for granulation, control the extrusion temperature at 160°C and the screw speed at 30 r / min to obtain masterbatch. Feed the masterbatch into a blown film machine, set the blown film temperature at 150°C, and produce a finished mulch film with a thickness of 0.012 mm.

[0022] Example 2

[0023] A method for preparing a fully biodegradable mulch film for seed corn production is as follows: S1. 16 mmol of 2-hydroxyhexanedialdehyde, 40 mmol of hydroxylamine hydrochloride and 3.15 g of potassium carbonate were added to 100 mL of 75% ethanol aqueous solution. The mixture was stirred at room temperature until no carbon dioxide was released. The mixture was then magnetically stirred for 6 h. After the reaction was completed, the solvent was removed by rotary evaporation. The crude product was dissolved in 100 mL of distilled water and heated to 60 °C. The mixture was then cooled and filtered. The product was then vacuum dried at 80 °C for 25 h. After the reaction was completed, intermediate 1 was obtained. S2. Add 16 mmol of intermediate 1 and 50 mmol of linoleic acid to a reaction flask containing 55 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.02 g of p-toluenesulfonic acid catalyst, and react at 90 °C for 8 h. After the reaction is completed, add 1 mol / L sodium hydroxide solution to adjust the pH to neutral, distill under reduced pressure, wash, and dry to obtain the trioleate compound. S3. Add 15 mmol of trioleate compound, 0.04 g of strong acid cation exchange resin and 0.12 g of acetic acid to a reaction flask containing 60 mL of N,N-dimethylformamide solvent, heat to 60 °C, slowly add 18 g of hydrogen peroxide, react for 8 h, distill under reduced pressure after the reaction, wash and dry to obtain epoxy intermediate 2. S4. Add 12 mmol of 3,3'-dithiodipropionic acid to 15 mmol of epoxy intermediate 2, heat to 155°C, then cool to 90°C, add 15 mmol of 4-methylhexahydrophthalic anhydride and 0.05 mmol of triethanolamine, mix well, cure at 120°C for 2 h, cure at 140°C for 2 h, and vacuum dry to obtain modified polyester; S5. Add 75 parts by weight of polylactic acid, 6 parts by weight of modified polyester, 12 parts by weight of biochar, 3 parts by weight of tributyl acetylacetate, and 0.5 parts by weight of antioxidant 1010 to a high-speed mixer and mix at 130°C for 20 minutes to obtain a mixture. Feed the mixture into a twin-screw extruder for granulation, control the extrusion temperature at 180°C and the screw speed at 50 r / min to obtain masterbatch. Feed the masterbatch into a blown film machine, set the blown film temperature at 170°C, and produce a finished mulch film with a thickness of 0.015 mm.

[0024] Example 3

[0025] A method for preparing a fully biodegradable mulch film for seed corn production is as follows: S1. 14 mmol of 2-hydroxyhexanedialdehyde, 35 mmol of hydroxylamine hydrochloride, and 3.14 g of potassium carbonate were added to 97 mL of 75% ethanol aqueous solution. The mixture was stirred at room temperature until no carbon dioxide was released, and then magnetically stirred for 5 h. After the reaction was completed, the solvent was removed by rotary evaporation. The crude product was dissolved in 95 mL of distilled water and heated to 58 °C. After cooling and filtration, the product was vacuum dried at 76 °C for 24 h to obtain intermediate 1. S2. Add 15 mmol of intermediate 1 and 47 mmol of linoleic acid to a reaction flask containing 53 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.01 g of p-toluenesulfonic acid catalyst, and react at 85 °C for 8 h. After the reaction is completed, add 1 mol / L sodium hydroxide solution to adjust the pH to neutral, distill under reduced pressure, wash, and dry to obtain the trioleate compound. S3. 13 mmol of trioleate compound, 0.035 g of strong acid cation exchange resin and 0.11 g of acetic acid were added to a reaction flask containing 55 mL of N,N-dimethylformamide solvent. The mixture was heated to 58 °C and 16 g of hydrogen peroxide was slowly added dropwise. The reaction was carried out for 7 h. After the reaction was completed, the mixture was distilled under reduced pressure, washed and dried to obtain epoxy intermediate 2. S4. Add 11 mmol of 3,3'-dithiodipropionic acid to 13 mmol of epoxy intermediate 2, heat to 153°C, then cool to 87°C, add 13 mmol of 4-methylhexahydrophthalic anhydride and 0.04 mmol of triethanolamine, mix well, cure at 115°C for 2 h, cure at 130°C for 2 h, and vacuum dry to obtain modified polyester; S5. Add 70 parts by weight of polylactic acid, 5 parts by weight of modified polyester, 10 parts by weight of biochar, 2.5 parts by weight of tributyl acetylacetate, and 0.4 parts by weight of antioxidant 1010 to a high-speed mixer and mix at 125°C for 18 minutes to obtain a mixture. Feed the mixture into a twin-screw extruder for granulation, with the extrusion temperature controlled at 170°C and the screw speed at 40 r / min to obtain masterbatch. Feed the masterbatch into a blown film machine, set the blown film temperature to 160°C, and produce a finished mulch film with a thickness of 0.014 mm.

[0026] Example 4

[0027] A method for preparing a fully biodegradable mulch film for seed corn production is as follows: S1. 12 mmol of 2-hydroxyhexanedialdehyde, 30 mmol of hydroxylamine hydrochloride and 3.12 g of potassium carbonate were added to 90 mL of 75% ethanol aqueous solution. The mixture was stirred at room temperature until no carbon dioxide was released. The mixture was then magnetically stirred for 4 h. After the reaction was completed, the solvent was removed by rotary evaporation. The crude product was dissolved in 90 mL of distilled water and heated to 55 °C. The mixture was then cooled and filtered. The product was then vacuum dried at 75 °C for 20 h. After the reaction was completed, intermediate 1 was obtained. S2. Add 14 mmol of intermediate 1 and 45 mmol of linoleic acid to a reaction flask containing 50 mL of N,N-dimethylformamide solvent, stir and mix, then add 0.01 g of p-toluenesulfonic acid catalyst, and react at 80 °C for 7 h. After the reaction is completed, add 1 mol / L sodium hydroxide solution to adjust the pH to neutral, distill under reduced pressure, wash, and dry to obtain the trioleate compound. S3. Add 15 mmol of trioleate compound, 0.04 g of strong acid cation exchange resin and 0.12 g of acetic acid to a reaction flask containing 60 mL of N,N-dimethylformamide solvent, heat to 60 °C, slowly add 18 g of hydrogen peroxide, react for 8 h, distill under reduced pressure after the reaction, wash and dry to obtain epoxy intermediate 2. S4. Add 12 mmol of 3,3'-dithiodipropionic acid to 15 mmol of epoxy intermediate 2, heat to 155°C, then cool to 90°C, add 15 mmol of 4-methylhexahydrophthalic anhydride and 0.05 mmol of triethanolamine, mix well, cure at 120°C for 2 h, cure at 140°C for 2 h, and vacuum dry to obtain modified polyester; S5. Add 70 parts by weight of polylactic acid, 5 parts by weight of modified polyester, 10 parts by weight of biochar, 2.5 parts by weight of tributyl acetylacetate, and 0.4 parts by weight of antioxidant 1010 to a high-speed mixer and mix at 125°C for 18 minutes to obtain a mixture. Feed the mixture into a twin-screw extruder for granulation, with the extrusion temperature controlled at 170°C and the screw speed at 40 r / min to obtain masterbatch. Feed the masterbatch into a blown film machine, set the blown film temperature to 160°C, and produce a finished mulch film with a thickness of 0.014 mm.

[0028] Comparative Example 1

[0029] The difference between this comparative example and Example 4 is that a trioleate compound was used instead of the modified polyester.

[0030] Comparative Example 2

[0031] The difference between this comparative example and Example 4 is that epoxy intermediate 2 is used instead of modified polyester.

[0032] Performance testing The biodegradability of the mulch films prepared in the examples and comparative examples was tested according to standard GB / T20197-2006, and the average value of 10 test groups was taken. The tensile strength and elongation at break of the mulch films prepared in the examples and comparative examples were tested according to standard ASTM D638, and the average value of 10 test groups was taken.

[0033] Table 1: Tensile properties and biodegradability tests

[0034] As shown in Table 1, Examples 1-4 of the present invention exhibit better biodegradability and tensile strength compared to Comparative Examples 1-2, while also demonstrating better water vapor barrier properties. In Comparative Example 1, although trioleate is easily degraded, its low cross-linking structure leads to rapid degradation in the early stages, causing premature film failure and preventing it from supporting the entire growth period of corn. In Comparative Example 2, epoxy intermediate 2 lacks dynamic disulfide bonds, resulting in a tight cross-linking network that is difficult for microorganisms to disrupt, thus reducing the degradation rate. In Comparative Example 1, the cross-linking structure of trioleate and polylactic acid is not tight, leading to a loose membrane structure and increased water vapor permeation; epoxy intermediate 2 lacks dynamic disulfide bonds, causing the membrane structure to gradually crack over time, further increasing water vapor permeation and preventing soil moisture retention.

[0035] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0037] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A fully biodegradable mulch film for seed corn production, characterized in that, It includes the following components by weight: 65-75 parts polylactic acid, 4-6 parts modified polyester, 8-12 parts biochar, 2-3 parts tributyl acetylacetate, and 0.4-0.5 parts antioxidant 1010. The modified polyester is prepared by using 2-hydroxyhexanedialdehyde and hydroxylamine hydrochloride as raw materials to synthesize intermediate 1, which is then subjected to esterification, oxidation, and curing to obtain the modified polyester.

2. The fully biodegradable mulch film for seed corn production according to claim 1, characterized in that, The modified polyester is prepared by: S1. Add 2-hydroxyhexanedialdehyde, hydroxylamine hydrochloride, and potassium carbonate to 90-100 mL of 75% (v / v) aqueous ethanol solution. Stir at room temperature until no carbon dioxide is released, then magnetically stir for 4-6 h. After the reaction is complete, remove the solvent by rotary evaporation. Dissolve the crude product in 90-100 mL of distilled water and heat to 55-60 °C. Cool and filter, then vacuum dry at 75-80 °C for 20-25 h. After the reaction is complete, intermediate 1 is obtained. S2. Add intermediate 1 and linoleic acid to a reaction flask containing N,N-dimethylformamide solvent, stir and mix, continue to add p-toluenesulfonic acid catalyst, react at 80-90℃ for 7-8h, after which add 1mol / L sodium hydroxide solution to adjust pH to neutral, distill under reduced pressure, wash, dry, and obtain trioleate compound. S3. Add the trioleate compound, strong acid cation exchange resin, and acetic acid to a reaction flask containing N,N-dimethylformamide solvent, heat to 55-60℃, slowly add hydrogen peroxide, react for 6-8 hours, distill under reduced pressure after the reaction is completed, wash, and dry to obtain epoxy intermediate 2. S4. Add 3,3'-dithiodipropionic acid to epoxy intermediate 2, heat to 150-155℃, then cool, and continue to add 4-methylhexahydrophthalic anhydride and triethanolamine. Mix evenly, cure at 110-120℃ for 1-2 hours, cure at 120-140℃ for 1-2 hours, and vacuum dry to obtain modified polyester.

3. The fully biodegradable mulch film for seed corn production according to claim 2, characterized in that, In S1, the ratio of 2-hydroxyhexanedialdehyde, hydroxylamine hydrochloride, and potassium carbonate is 12-16 mmol: 30-40 mmol: 3.12-3.15 g.

4. The fully biodegradable mulch film for seed corn production according to claim 2, characterized in that, In S2, the ratio of intermediate 1, linoleic acid, and p-toluenesulfonic acid catalyst is 14-16 mmol: 45-50 mmol: 0.01-0.02 g.

5. The fully biodegradable mulch film for seed corn production according to claim 2, characterized in that, In S3, the ratio of trioleate compound, strong acid cation exchange resin, acetic acid, and hydrogen peroxide is 12-15 mmol: 0.03-0.04 g: 0.11-0.12 g: 14-18 g.

6. The fully biodegradable mulch film for seed corn production according to claim 2, characterized in that, In S4, the ratio of 3,3'-dithiodipropionic acid, epoxy intermediate 2,4-methylhexahydrophthalic anhydride, and triethanolamine is 10-12 mmol: 10-15 mmol: 10-15 mmol: 0.04-0.05 mmol.

7. The fully biodegradable mulch film for seed corn production according to claim 2, characterized in that, The cooling temperature in S4 is 85-90℃.

8. A method for preparing a fully biodegradable mulch film for seed corn production as described in any one of claims 1-7, characterized in that, The preparation method of the fully biodegradable mulch film for seed corn is as follows: polylactic acid, modified polyester, biochar, tributyl acetylacetate, and antioxidant 1010 are added to a high-speed mixer and mixed at 120-130℃ for 16-20 minutes to obtain a mixture; the mixture is fed into a twin-screw extruder for granulation, the extrusion temperature is controlled at 160-180℃, and the screw speed is 30-50 r / min to obtain masterbatch; the masterbatch is fed into a blown film machine, the blown film temperature is set at 150-170℃, and a mulch film with a thickness of 0.012-0.015 mm is produced.

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