1、UDC 667.621 : 661.728.892 : 001.4 : 620.1 D EUTS C H E N O R M June 1981 Binders for paints and varnishes Ce1 lu lose et hers Testing I 55952 Bindemittel fr Anstrichstoffe; Celluloseether; Prfung As it is current practice in standards published by the International Organization for Standardization (
2、ISO), the comma has been used throughout as a decimal marker. The symbol % used in this standard for specifying concentrations of solutions means the percentage concentration by mass (percentage by weight). Unless otherwise specified, the reagents shall be of ,analytical reagent“ grade and the refer
3、ence temperature for the density of liquids shall be 20 OC. Solutions of reagents for which no solvent is specified shall be solutions in distilled water or water of equivalent purity. In the descriptions of analytical processes also, water means distilled water or water of equivalent purity. 1 Fiel
4、d of application The test methods specified in this standard apply to cellulose ethers as defined in clause 3, when they are used for paints and varnishes. 2 Designation of method The method of testing cellulose ethers (A) shall be designated as follows: Test DIN 55952 -A 4.2.2 Hydroxyethyl cellulos
5、e (HEC) This includes the hydroxyethyl ether of cellulose and its mixed ethers of the alkyl hydroxyethyl cellulose type, if they are soluble in hot water. 4.2.3 Methyl cellulose (MC) This includes the methyl ether of cellulose and also, on the basis of their common properties, the alkyl hydroxy- alk
6、yl celluloses, if they are insoluble in hot water. 5 Common symbols 3 Concept Cellulose ethers are the water soluble alkyl, hydroxy- alkyl or carboxyalkyl ethers of cellulose. They are prod- uced by etherification, part of the hydroxyl groups in the cellulose being substituted by one or more etherif
7、ying agents. The ethers produced are either simple ethers or mixed ethers with different degrees of substitution. 4 Classification of cellulose ethers 4.1 Conspectus Cellulose ethers lonogenic A Nonionogenic cellulose ethers (CMC) cellulose ethers Cold water soluble and hot water soluble Cold water
8、soluble cellulose ethers cellulose ethers (HEC) (MC, MC-mixed ethers) 4.2 Types 4.2.1 Sodium carboxymethyl cellulose (CMC) This includes the sodium sait of the glycolic acid ether of cellulose and mixed ethers containing this, for example of the type of the carboxymethyl hydroxyethyl or carboxymethy
9、l hydroxypropyl celluloses, if their ionogenic character is predominant. Table 1. Symbol MHEC Cellulose ether I suWause Ethyl hydroxyethyl cellulose 4.2.2 Hydroxyethyl cellulose I 4.2.2 Methyl cellulose 1 4.2.3 Methyl hydroxyethyl cellulose 1 4.2.3 I MHPC I Methyl hydroxypropyl cellulose 1 4.2.3 6 S
10、ampling A representative sample shall be taken from the product to be tested, as specified in DIN 53242 Part 1 (Pre- liminary standard) and Part 4. 7 Identification of cellulose ethers The specified tests will allow sufficiently accurate quali- tative identification of the cellulose ethers specified
11、 in clause 5. 7.1 Apparatus 7.1 .I Test tube, 16 cm long Continued on pages 2 to 5 Beuth Verlag GrnbH. Berlin 30, has exclusive sale rights for German Standards (DIN-Normen) 06.84 DIN 55 952 Engl. Price group 6 Sales No. 0106 Page 2 DIN 55 952 Cellulose ether CMC MHECIEHEC HEC MC MHPC 7.1.2 Filter p
12、aper 7.1.3 Silicone oil bath as specified in DIN 12 877 (at present at the stage of draft), with stirrer and thermostat 7.1.4 Ice bath 7.1.5 Water bath as specified in DIN 12 877 (at present at the stage of draft) Test No. 1 No. 2 No. 3 No. 4 No. 5 (subclause 7.3.1) (subclause 7.3.2) (subclause 7.3.
13、3) (subclause 7.3.4) (subclause 7.3.5) + - - - - - - + + + + - - - - - - + + + + + + - 7.2 Reagents 7.2.1 Manganese sulfate (MnSO4 . H201, powdered 7.2.2 96 % sulfuric acid 7.2.3 Iced water 7.2.4 5 % aluminium sulfate solution 7.2.5 10 % ammonia solution 7.2.6 20 % diethanol amine solution 7.2.7 10
14、% acetic acid 7.2.8 5 % copper sulfate solution 7.2.9 Ninhydrin reagent Dissolve 3 g of ninhydrin (2,2-Dihydroxy indandion-(I ,311 in 10 ml of a 4,55% aqueous solution of sodium pyro- su If i te. 7.2.10 5 % sodium nitroprusside (sodium nitro penta- cyano ferrate-111) solution 7.2.1 1 70 % sulfuric a
15、cid 7.2.12 1 %tannin solution 7.2.13 1 molh hydrochloric acid 7.2.14 20 % sodium hydroxide solution 7.3 Procedure 7.3.1 Coagulation by heat (test No. 1) Sprinkle 2 g of the sample while stirring, into 100 ml of water heated to 90 OC, continue stirring while the mixture cools to room temperature and
16、then top it up to 200 ml with iced water. Once it has completely dissolved, heat 100 ml of this solution in a water bath. Table 2. Identification methods In the presence of EHEC, MC or MC mixed ethers, the solution becomes turbid or a flocculant precipitate is produced at temperatures above 50 OC, w
17、hich disappears again on cooling. 7.3.2 Precipitation by tannin (test No. 2) Add five drops of 10% acetic acid and about the same volume of a 1 % tannin solution to 5.0 ml of the solution as prepared for test No. I. In the presence of EHEC, HEC, MC, MHEC and MHPC, yellowwhite flocculation occurs, wh
18、ich is soluble in a 10% ammonia solution. 7.3.3 Reaction on sodium nitroprusside (test No. 3) Mix about 39 of the sample in the test tube with 29 of powdered manganese sulfate. Insert 2 cm deep into the test tube a strip of filter paper that has previously been dipped into a solution freshly prepare
19、d as follows: Mix 1 part by volume of 20 % diethanol amine solution and 11 parts by volume of 5% sodium nitroprusside solution. Adjust the pH value of the mixture to 9,5 by adding hydrochloric acid. Then dip the test tube 8 cm deep into the silicone oil bath, heated to 190 to 200C. If HEC, MHEC/EHEC
20、 or MHPC are present, the filter paper will turn a clear blue colour within 15 minutes. Carry out a blanc test in the same manner without samples. 7.3.4 Coloration by ninhydrin (test No. 4) Dissolve about 0.2 g of the sample completely in 15 ml of 70% sulfuric acid. Stir this solution into 100ml of
21、iced water and top up to 250ml with iced water. Thoroughly mix 1 ml of this solution, whilst intensively cooling it, in drops with 8 ml of 96% sulfuric acid in a test tube, heat it for exactly three minutes in a boiling water bath and then cool it immediately in an ice bath. At room temperature, car
22、efully add 0.6 ml of freshly prepared ninhydrin reagent and shake the mixture thoroughly. Leave the solution to stand at 25C and observe it over a period of 100 minutes. If MHPC is present, violet coloration will occur within this time, otherwise the mixture will be pink coloured. Carry out a blanc
23、test in the same manner without sample. - negative reaction DIN 55952 Page 3 7.3.5 Precipitation reaction (test No. 5) Dilute 2,5 ml of solution prepared as for test No. 1, with the same quantity of water and then add, drop by drop, 1 ml of 5% alumininium sulfate solution or 5% copper sulfate soluti
24、on. If CMC is present, there will be a white or bright blue precipitate that is soluble in an excess of 20% sodium hydroxide solution or an excess of 1 O % ammonia solu- tion. 8 Average degree of substitution of CMC The average degree of substitution (DS) of CMC shall be determined by the copper met
25、hod. 8.1 Summary of method The copper method can be used for testing CMC in solu- tions of virtually any viscosity. Salts resulting from the production of CMC do not interfere with the method. The product may be in any solid form (very fine powder, powder, granules) or in an aqueous solution. The co
26、pper method requires only small sample weights (0,2 to 0,4g) and 6 testscan be carried out simultaneously. The result is obtained after 8 to 9 hours. The CMS shall be precipitated from the aqueous solution of its sodium salt as copper carboxymethyl cellulose (CuCMC) by adding copper sulfate solution
27、. This precip- itate shall be separated, dried and then, after weighing, incinerated to copper oxide. The copper oxide shall be decomposed with potassium disulfate, mixed with pot- assium iodide solution and the resulting iodine titrated with sodium thiosulfate solution. The average substitu- tion l
28、evel shall be calculated from the copper content determined by the iodometric titration. 8.2 Reagents 8.2.1 Potassium disulfate (K2S207). powdered 8.2.2 99 - 100 % acetic acid 8.2.3 Methanol 8.2.4 50 % methanol solution 8.2.5 25 % ammonia solution 8.2.6 25 % hydrochloric acid 8.2.7 Potassium thiocya
29、nate solution Dissolve 2g of potassium thiocyanate (KCNS) in 10ml of water. 8.2.8 Potassium iodide solution Dissolve 5 g of potassium iodide (KI) in 10 ml of water. 8.2.9 Copper sulfate solution Dissolve log of copper sulfate (CuSO4 . 5 H20) in 100 ml of water. 8.2.10 0,5 mol/l ammonia solution 8.2.
30、1 1 1 % starch solution 8.2.12 1 g Cu/l copper standard solution 8.2.13 0,02 mol/l sodium thiosulfate standard solution 8.2.13.1 Determining the titre Pour 50 ml of water in an iodine value measuring flask and add exactly 30,O ml (Vo) of copper sulfate standard solution containing exactly (1 I 0,000
31、1) g of copper per litre, from a pipette capable of being calibrated. Add drops of 25 % ammonia solution to the above solution until it shows a blue coloration as a result of the copper tetramine complex. Then add 5 ml of acetic acid and 10 ml of potassium iodide solution. Leave the solution to stan
32、d for 2 to 3 minutes in the dark in the sealed flask. Titrate with the sodium thiosulfate standard solution, whilst the solution under test is being vigorously shaken or stirred, until the characteristic colour of the iodine has almost disappeared, After adding 10 ml of pottassium thiocyanate soluti
33、on and 3 to 5 ml of starch solution, shake vigorously again and continue titrating until the blue colouring produced just disappears (VI 1. 8.2.13.2 Calculation of the titre Calculate the titre from the following equation: Vo . 1,2708 1= where Vo = 30ml 38,124 Vl Vl =- where Vo is the volume, in ml,
34、 of copper sulfate standard solution initially used (30 ml); VI is the volume, in mi, of sodium thiosulfate solution; 1,2708 = 1 /50 equivalent copper. 8.3 Apparatus 8.3.1 8.3.2 8.33 8.3.4 8.3.5 8.3.6 83.7 8.38 Weighing bottle with lid Analytical balance Heating chamber Desiccator 400 ml low formed
35、beaker 10 ml, 50 ml and 250 ml graduated cylinders Magnetic stirrer with heating Device for Dotentiometric titration, DH meter with glass electrode and reference electrode (see also DIN 19260, DIN 19263, DIN 19264). 8.39 50 ml burette 8.3.10 2 G 2 glass filter crucible 8.3.11 Filter paper, 40 mm in
36、diameter 8.3.12 Vacuum pump with suction bottle 8.3.13 A2 porcelain crucible 8.3.14 300 ml iodine value measuring flask, with conical ground socket 8.3.15 30 ml pipette, capable of being calibrated 8.3.16 Bunsen burner 8.3.17 Muffle furnace Page 4 DIN 55 952 8.4 Procedure Weigh about 0,2g of air dri
37、ed, CMC with a low salt content or 0,25 to 0,4g of industrial CMC into the beaker. The initial sample weight shall be chosen so that the sample contains about 0.2 g of the active substance. Damp the sample with 10 ml of methanol and then add 210 ml of water whilst stirring slowly to start with and l
38、ater stirring rapidly. Once the sample has dissolved, insert the electrodes, calibrated for the pH range 2 to 4. Adjust the pH value of the solution to 1,9 up to 2,O by adding hydrochloric acid in drops. Then add 10 ml of copper sulfate solution whilst stirring. No turbidity or precipitation in the
39、solution shall occur when this is done; if necessary, add some further hydrochloric acid. Then slowly add 0,5 mol/l of ammonia solution from the burette until a pH value of 4,O is obtained. Copper carboxymethyl cellulose will then precipitate as bright blue flocks. Remove the glass electrodes from t
40、he solu- tion and rinse off any adhering precipitate with methanol solution into the beaker. Stir the solution for a further 10 to 15 minutes. If the precipitate is very fine, the solu- tion shall be heated during this period to about 60C. Leave the solution to stand until the precipitate has settle
41、d and the remaining solution is clear. Pour off the remaining solution through the glass filter crucible with the filter paper placed inside it. Then rinse the precipitate on to the glass filter crucible with 50 % methanol solution. Continue washing the precipitate with small portions of 50% methano
42、l until the filtrate is free from chloride and sulfate. Then fill the glass filter crucible with 100% methanol and allow the methanol to act on the precip- itate. If necessary, top up the methanol. Then dry the precipitate by suction. Dry the precipitate for three hours at 100 OC in a heating chambe
43、r. After cooling in the desiccator, weigh the main part of the precipitate consisting of copper carboxy- methyl cellulose in a porcelain crucible (m3) and care- fully incinerate it over a Bunsen burner. To ensure complete incineration, heat the crucible for one hour at (600 2 20) “C in the muffle fu
44、rnace. After cooling, add some potassium disulfate on the tip of a spatula and heat over the Bunsen burner. Decom- position of the copper oxide is complete when a skin forms on the red glowing melt (after about ten minutes). Once the crucible has cooled, add about 10 ml of water to the solidified me
45、lt. Allow a short time for this to take effect and then transfer the melt, which shall come out of the crucible easily, with the least amount of water possible into the iodine value measuring flask. Then dis- solve the melt by boiling. After the solution has cooled to 20 to 25 “C add drops of ammoni
46、a solution until the solution has a blue colour- ing because of the copper tetramine complex. Then add 5 mi of acetic acid and 10 ml of potassium iodide solu- tion, Leave the solution to stand in the dark in the closed flask for two to three minutes. Titrate with the sodium thiosulfate standard solu
47、tion, whilst vigorously shaking or stirring the test solution, until the characteristic colour of the iodine has almost disappeared. After adding 10 ml of potassium rbjo- cyanate solution and 3 to 5 ml of starch solution shake the mixture vigorously again and titrate further until the blue colour pr
48、oduced just disappears (V2). 8.5 Expression of result Calculate the copper content, in %, of the precipitated, dried copper carboxymethyl cellulose from the follow- ing equation: 0,1271 . V2 . t Comer content = m3 where m3 is the initial weight, in g, of the copper carboxy- methyl cellulose sample;
49、t is the titre of sodium thiosulfate standard solution; V2 is the amount, in ml, of sodium thiosulfate stand- ard solution used. Calculate the average substitution level from the copper content, using the following equation: 1,62 . Yo CU 31,77 - ,89 . Yo CU DS - Report the result to two decimal places. 9 Components volatile at 105C (loss on drying) The components volatile at 105 “C shall be determined by the method given in DIN 53 198, the sample being dried for three hours and then weighed after cooling. Note: When determining the cellulose ether content, it is important to tak
