Modified raw lacquer and preparation method thereof

Abstract

The invention discloses modified raw lacquer and a preparation method thereof. The modified raw lacquer contains modified urushiol shown in a formula (I) and is prepared by performing esterification reaction on dialkyl phosphonyl chloride and urushiol in an inert atmosphere. The modified raw lacquer has excellent flame retardant property. The preparation method is simple in process, the grafting rate reaches up to 82%, and the method is suitable for the fields of furniture, handicrafts, buildings, chemical engineering and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of natural polymer coating flame-retardant modification technology, especially to a kind of modified raw lacquer by chemical grafting diethyl hypophosphite group and imparting raw lacquer high efficient flame-retardant performance and its preparation method. BACKGROUND

[0002] Raw lacquer (also known as Chinese lacquer) is known as "King of Coatings" due to its excellent corrosion resistance, aging resistance, high temperature resistance and decorative properties. It has been used in furniture, handicrafts, architecture and chemical industry for more than 8,000 years. However, the limiting oxygen index (LOI) of raw lacquer is only about 17.9%, which belongs to flammable materials, and seriously limits its application in high fire safety requirements.

[0003] The research on raw lacquer flame retardant is currently mainly focused on two major technical routes of physical blending flame retardant and chemical modification. The physical blending method is the most widely used method at present, which is simple to operate and low in cost by directly adding flame-retardant components into the raw lacquer matrix; the chemical modification method can obtain more durable flame-retardant effect by introducing flame-retardant elements through changing the molecular structure of raw lacquer, but the process is complex.

[0004] In terms of physical blending, intumescent flame-retardant system is the most concerned. This system is usually composed of acid source (such as ammonium phosphate), gas source (such as melamine) and carbon source (such as pentaerythritol), which can form a porous carbon layer on the surface of the material during combustion, playing a role in heat insulation, oxygen insulation and smoke suppression. The nitrogen-phosphorus intumescent flame retardant developed by the team of Minjiang University can improve the limiting oxygen index of raw lacquer film from 17.9% to more than 29% by compounding melamine derivatives (FR-1) with phosphoric acid ethylenediamine salt (FR-2) at a specific ratio, reaching the standard of difficult flammable materials. The flame retardant can promote the crosslinking of raw lacquer molecules into carbon during combustion, and the formed carbon layer can effectively block the transmission of heat and combustible gas.

[0005] In terms of chemical modification, lacquer phenolic reactive flame retardant is a research hotspot. Lacquer phenol, as the main active ingredient of raw lacquer (content 50-70%), provides the possibility for chemical modification through the hydroxyl group on the benzene ring and the double bond of the side chain.

[0006] Phosphate ester flame retardant is an important phosphorus-based flame retardant, which is highly concerned in halogen-free flame retardant field due to its high efficiency, low smoke and low toxicity. Phosphate ester flame retardant is still an important choice in many polymer materials due to its balanced flame-retardant performance, plasticizing effect and relatively environmentally friendly characteristics. SUMMARY

[0007] The purpose of the present application is to provide a kind of flame-retardant modified raw lacquer and its preparation method, by chemical grafting diethyl hypophosphite group to lacquer phenol molecule, the main component of raw lacquer, significantly improving the flame-retardant performance of raw lacquer, and the process is simple, the grafting rate is high, the environment is friendly, and it is suitable for industrial production.

[0008] The flame-retardant modified raw lacquer of the present application is characterized in that the modified raw lacquer contains structural units shown in formula (I): Formula (I), wherein: R1, R2 are each independently selected from C1-C6 alkyl, preferably C1-C4 alkyl, more preferably methyl, ethyl, propyl or butyl; the propyl and butyl can be straight chain or branched; R1 and R2 can be the same or different.

[0009] A method for preparing modified lacquer phenol, characterized in that it comprises the following steps: dissolving lacquer phenol and acid-binding agent in an organic solvent under inert atmosphere, and adding dropwise a solution of dialkyl phosphinic chloride for esterification to obtain modified lacquer phenol; the alkyl is C1-C4 alkyl.

[0010] The acid-binding agent is triethylamine, sodium carbonate, potassium carbonate, sodium bicarbonate.

[0011] The inert atmosphere is nitrogen or argon, and the reaction temperature is preferably 60±2℃.

[0012] The use of the flame-retardant modified raw lacquer in the fields of furniture, handicrafts, architecture and chemical industry.

[0013] The use of a raw lacquer containing modified lacquer phenol in the fields of furniture, handicrafts, architecture and chemical industry.

[0014] The reaction equation of lacquer phenol with dialkyl phosphinic chloride: R1 and R2 are each independently selected from C1-C6 alkyl.

[0015] The method for preparing the flame-retardant modified lacquer phenol comprises the following steps: a) Raw lacquer pretreatment: centrifuging, filtering and dehydrating natural raw lacquer to obtain dehydrated raw lacquer; b) Lacquer phenol extraction: extracting the dehydrated raw lacquer with acetone / n-hexane, drying and concentrating to obtain lacquer phenol with a purity of ≥90%; c) Esterification reaction: dissolving the lacquer phenol obtained in step b) and an acid-binding agent in anhydrous organic solvent under inert atmosphere, adding dropwise a solution of diethyl phosphinic chloride, heating and reacting for a period of time; d) Post-treatment: filtering, concentrating, ice water precipitation, centrifuging, washing and vacuum drying the reaction liquid obtained in step c) to obtain light yellow modified lacquer phenol; e) Coating preparation: dissolving the modified lacquer phenol obtained in step d) in acetone to prepare a base, coating the base on the surface of a substrate, and curing to obtain a flame-retardant raw lacquer coating.

[0016] The acid-binding agent in step c) is selected from one or more of triethylamine, sodium carbonate, potassium carbonate and sodium bicarbonate.

[0017] The organic solvent in step c) is selected from one or more of ethyl acetate, acetone, tetrahydrofuran, dichloromethane, chloroform, and acetone.

[0018] The inert atmosphere in step c) is nitrogen or argon.

[0019] The heating reaction temperature in step c) is preferably 60±2℃.

[0020] The reaction time in step c) is 2-10 hours.

[0021] A fire-retardant raw lacquer and a preparation method thereof: taking anhydrous impurity-removed natural raw lacquer, adding an organic solvent under an inert gas condition, dissolving an acid-binding agent in the organic solvent, and adding a solution of dialkyl phosphinic chloride dropwise to perform esterification reaction to obtain modified lacquer phenol; the alkyl group is a C1-C4 alkyl group.

[0022] The acid-binding agent is triethylamine, sodium carbonate, potassium carbonate, or sodium bicarbonate.

[0023] The inert atmosphere is nitrogen or argon, and the reaction temperature is preferably 60±2℃.

[0024] The fire-retardant modified raw lacquer is used in the fields of furniture, handicrafts, buildings, and chemical industry.

[0025] The specific steps are as follows: Raw lacquer pretreatment: taking anhydrous impurity-removed natural raw lacquer, performing coarse filtration with a copper sieve to remove visible impurities such as branches and insects. The filtered raw lacquer is subjected to dehydration treatment, and when the liquid changes from milky white to transparent brown, it indicates that the dehydration is completed.

[0026] Reaction system preparation: connect a three-necked flask to a nitrogen gas inlet system, continuously introduce nitrogen gas for 10 minutes to replace air, and maintain a slight positive pressure. Add anhydrous natural raw lacquer and anhydrous toluene to the flask, and start stirring (40-50 revolutions per minute) to disperse the raw lacquer. Slowly add triethylamine, adjust the pH to 9-10, and provide an alkaline environment for the subsequent reaction.

[0027] Modified reaction process: dissolve diethyl phosphinic chloride in anhydrous toluene, slowly add it through a constant-pressure dropping funnel, control the dropping speed to maintain the reaction temperature at 60±2℃, and continue the reaction after the addition is completed. During the reaction, the reaction progress is monitored by thin layer chromatography (TLC).

[0028] Post-treatment process: after the reaction is completed, cool to room temperature, add dilute hydrochloric acid to neutralize the excess triethylamine, and then wash with deionized water 3 times until neutral. Dry the organic phase with anhydrous sodium sulfate, remove toluene through a rotary evaporator, and obtain viscous modified raw lacquer.

[0029] The application can produce the following beneficial effects: The present application aims to provide a fire-retardant modified raw lacquer and a preparation method thereof, which significantly improves the fire-retardant performance of the raw lacquer by chemically grafting diethyl hypophosphite groups onto the lacquerin molecules of the main component of the raw lacquer, and is simple in process, high in grafting rate, environment-friendly, and suitable for industrial production.

[0030] Compared with traditional blending modification, the present application grafts phosphate groups onto lacquerin through chemical modification, which is stable in structure, strong in weather resistance, and high in stability.

[0031] The modified raw lacquer prepared by the present application has good fire-retardant performance and has wide application in the fields of furniture, handicrafts, buildings and chemical industry. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Reaction equation of the present application DETAILED DESCRIPTION

[0033] The examples of the present application are described in detail below.

[0034] If the specific experimental steps or conditions are not specified in the examples, the operation or conditions can be carried out according to the conventional experimental steps described in the literature in the art. If the reagents or instruments are not specified by the manufacturer, they are conventional reagent products that can be obtained by purchase.

[0035] Experimental materials and equipment Main raw materials Raw lacquer raw material: natural raw lacquer (lacquerin content ≥ 65%, China Mao Ba Lacquer) Modifier: diethyl phosphine chloride (purity ≥ 98.5%), Jiangsu Lisi New Material Co., Ltd. Solvent: anhydrous tetrahydrofuran (THF, 4Å molecular sieve drying), acetone, toluene Acid binding agent: triethylamine (TEA, 99.5%) Instrument equipment Reaction device: 250mL three-necked flask (equipped with mechanical stirring, constant pressure dropping funnel, thermometer and reflux condenser) Purification system: rotary evaporator, vacuum drying oven, high-speed centrifuge (5000rpm) Characterization equipment: Fourier transform infrared spectrometer (FTIR) Inductively coupled plasma emission spectrometer (ICP-OES) Flame-retardant test equipment: Limiting oxygen index instrument (LOI) Cone calorimeter (35kW / m 2 ) Vertical burning tester (UL-94) I. Preparation method of modified urushiol Step 1: Extraction and purification of urushiol Raw lacquer pretreatment: The raw lacquer is centrifuged at 3000 rpm for 10 minutes to remove large particles such as branches and leaves; it is then filtered through a 450-mesh nylon filter to further separate the fine particles; the filtrate is stirred and dehydrated at 25°C for 8 hours to reduce the water content to below 8%.

[0036] Urushiol extraction: Mix 20g of dehydrated raw lacquer with 140mL of acetone and extract with ultrasonic assistance (300W power, 3 minutes); filter to remove lacquinone and polysaccharide precipitate, concentrate the filtrate under reduced pressure at 35℃; extract the concentrate with hexane / water (1:1, v / v), collect the organic phase, and dry with anhydrous sodium sulfate.

[0037] Storage conditions: Place the purified urushiol in a brown glass bottle, purge with nitrogen, and store at -20℃ for later use; before use, test the purity by HPLC (≥90%).

[0038] Step 2: Esterification reaction of diethylphosphonic chloride with urushiol Add 15 g of purified urushiol, 15 mL (100 mmol) of triethylamine acid-binding agent, and 60 mL of anhydrous THF to a dry three-necked flask, and purge with nitrogen. Dissolve 14.1 g of diethylphosphonic chloride in 15 mL of anhydrous THF and place the solution in a constant-pressure dropping funnel; control the dropping rate at 1 mL / min and maintain the reaction temperature at 25 ± 2 °C. Slowly raise the temperature to 60 °C and continue the reaction for 12 hours, monitoring the reaction progress by TLC (developing solvent: petroleum ether / ethyl acetate = 3:1) until the reaction is complete. Cool the reaction solution to room temperature, filter to remove triethylamine hydrochloride; concentrate the filtrate under reduced pressure to 1 / 3 of its original volume, add 150 mL of ice water to precipitate the product; centrifuge (4000 rpm, 10 min), wash the precipitate three times with deionized water; dry under vacuum at 50 °C to constant weight to obtain pale yellow modified urushiol.

[0039] Step 3: Preparation of Flame-Retardant Raw Lacquer Coating Dissolve 12g of modified urushiol in 28mL of acetone to prepare a base material.

[0040] Structural characterization and performance testing Chemical structure characterization The infrared spectra of urushiol before and after modification were tested using the KBr pellet method; the modified urushiol was measured at 1230 cm⁻¹. 1 A characteristic P=O peak appears nearby, at 1070 cm⁻ 1 The presence of a PO stretching vibration peak nearby confirms the formation of a diethyl hypophosphite structure. No characteristic peaks were observed at the aforementioned positions in either unmodified or modified urushiol.

[0041] Phosphorus content determination: The phosphorus content of the modified urushiol was determined by ICP-OES to be 9.65%. The content of phosphorus element also indicates the formation of diethyl hypophosphite structure.

[0042] Grafting rate calculation according to phosphorus content: Grafting rate (%) = (measured phosphorus content / theoretical phosphorus content) x 100%, the grafting rate is about 82.05% (wherein the urushiol is calculated according to the average molecular weight of 318).

[0043] Comparison of structure characterization data of urushiol before and after modification Flame retardant performance test According to GB / T2406-80, the limiting oxygen index (LOI) was tested, wherein the sample size was 100mm x 10mm x 3mm. The LOI of unmodified raw lacquer was about 18% (flammable), and after modification, it increased to more than 28% (difficult to burn).

[0044] Conical calorimetric test: Thermal radiation power 35kW / m 2 , sample size 100mm x 100mm x 3mm. The pHRR of modified urushiol decreased by more than 50%, and the THR decreased by more than 40%.

[0045] According to GB / T2408-2008, the vertical burning test (UL-94) was tested, wherein the sample size was 125mm x 13mm x 3mm. The modified urushiol reached V-0 level, and the unmodified urushiol reached V-2 level.

[0046] Table 1: Comparison of flame retardant performance of raw lacquer before and after modification Test item Flame retardant mechanism analysis Phosphorus element generates phosphoric acid substances during combustion, catalyzing the dehydration of urushiol to form carbon, and forming a dense carbon layer. PO· free radicals produced by thermal decomposition can capture H· and OH· free radicals in the combustion chain reaction, interrupting the combustion reaction.

[0047] II. Preparation method of flame-retardant modified raw lacquer 1. Raw lacquer pretreatment Take 200g of natural raw lacquer, and coarsely filter it with a 120 mesh copper sieve to remove visible impurities such as branches and insects. After filtering, the raw lacquer is dehydrated. When the liquid changes from milky white to transparent brown, it indicates that the dehydration is complete.

[0048] 2. Preparation of reaction system Three necked flask was connected to nitrogen gas inlet system, nitrogen gas was continuously introduced for 10 minutes to replace air, and maintained a slight positive pressure. 100 g of anhydrous natural raw lacquer and 100 mL of anhydrous toluene were added to the flask, and stirring was started (40-50 rpm) to disperse the raw lacquer. Triethylamine was slowly added dropwise to adjust the pH to 9-10 to provide a basic environment for the subsequent reaction.

[0049] 3. Modification reaction process Diethyl phosphine chloride (65 g) was dissolved in 20 mL of anhydrous toluene and slowly added dropwise through a constant pressure dropping funnel, controlling the dropwise speed to maintain the reaction temperature at 60±2℃. After the addition was completed, the temperature was raised to 70-80℃ and the reaction was continued for 3-4 hours. During this period, the progress of the reaction was monitored by thin layer chromatography (TLC).

[0050] 4. Post-treatment process After the reaction was completed, it was cooled to room temperature, and the excess triethylamine was neutralized by adding dilute hydrochloric acid, and then washed with deionized water 3 times until neutral. The organic phase was dried with anhydrous sodium sulfate, and then toluene was removed by a rotary evaporator to obtain a viscous modified raw lacquer.

[0051] According to GB / T 2408-2008, vertical burning test (UL-94) was tested: sample size 125 mm x 13 mm x 3 mm. The modified raw lacquer reached V-0 level, and the unmodified raw lacquer reached V-2 level.

[0052] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A fire-retardant modified raw lacquer, characterized in that, The modified raw lacquer contains modified urushiol represented by formula (I): Formula (I), wherein: R is R1, R2 are each independently selected from C1-C6 alkyl.

2. The flame-retardant modified raw lacquer according to claim 1, characterized in that, R1and R2are each independently selected from C1-C4 alkyl.

3. The flame-retardant modified raw lacquer according to claim 2, characterized in that, R1and R2are each independently selected from methyl, ethyl, propyl or butyl, the propyl or butyl being linear or branched.

4. A method for preparing a modified urushiol according to claim 1, characterized by, comprising the steps of: under inert atmosphere, dissolving anhydrous urushiol and acid binding agent in organic solvent, adding dropwise a solution of dialkyl phosphinic chloride to carry out esterification reaction to obtain modified urushiol; the alkyl is C1-C6 alkyl.

5. The production method according to claim 4, characterized by, the acid binding agent is selected from one or more of triethylamine, sodium carbonate, potassium carbonate, sodium bicarbonate.

6. The production method according to claim 4, characterized by, the organic solvent is selected from one or more of ethyl acetate, acetone, tetrahydrofuran, dichloromethane, chloroform, acetone.

7. The method of any one of claims 4-6, wherein the method further comprises, the inert atmosphere is nitrogen or argon, and the reaction temperature is preferably 60±2℃.

8. Use of the flame-retardant modified raw lacquer according to any one of claims 1-3 or the modified urushiol prepared by the method according to any one of claims 4-7 in the field of furniture, handicraft, architecture and chemical industry.

9. A modified urushiol prepared by the method according to any one of claims 4-7.

10. Use of a raw lacquer comprising the modified urushiol prepared by the method according to any one of claims 4-7 in the field of furniture, handicraft, architecture and chemical industry.

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