Ex-ante control
Ex-ante control is the detection and control of raw materials to avoid the occurrence of quality problems. To truly achieve ex-ante control, we must strictly follow certain national behaviors or enterprise standards to carefully inspect each batch of raw materials, and do not use non-compliant raw materials .
The indicators and testing methods required by national standards for thinners, glues, films, inks and other raw materials are as follows:
(1) Detection of thinner
The diluent refers to the solvent used in the compounding process, namely ethyl acetate, toluene, acetone and methyl ethyl ketone.
â‘ Indicator: The water content should not exceed 0.2%, and the total purity should not be less than 99% (according to GB3728-91).
â‘¡Control method: use gas chromatograph, nitrogen gas as carrier gas, thermal conductivity cell detector, peak height and concentration to plot, get the working curve, then under the same conditions each batch of solvent sampling to make the corresponding peak height to get the concentration.
â‘¢ Specific operation:
A. Gas chromatograph: report chamber temperature 250 ℃, detection chamber temperature 200 ℃, column chamber temperature 150 ℃, with polymer porous beads as column packing;
B. Distillation and purification of analytical reagents by chemical methods. (Different purification methods for various solvents);
C. Use the purified solvent and water to prepare standard solvents with hydration of 0.02%, 0.05%, 0.1%, 0.15%, 0.2%;
The injection volume is 0.1ml, and under certain bridge current and attenuation, the response peak of water is obtained. The peak height of water is plotted against the concentration to obtain the working curve;
D. Each batch of raw materials is sampled, and the same sample is injected under the same conditions. The peak height is used to obtain the corresponding concentration in the working curve and compared with the standard;
E. Each start-up test must make a working curve, regardless of whether the conditions are the same as before;
F. Similarly, prepare a solution with a purity of 100%, 99.8%, 99.5%, 99.2%, and 99%. The injection volume is 0.1ml. The peak height of the measured diluent is obtained. The peak height is plotted against the concentration to obtain the working curve. Then, the peak height is also obtained by sampling, and the corresponding concentration is obtained according to the working curve.
(2) Control of polyurethane glue
â‘ Polyurethane adhesives have different uses and there is no common testing standard, but there are common testing methods;
â‘¡Solid content: GB2793-81, using thermal weightlessness method to test the content of non-volatile matter in polyurethane adhesive.
Specific operation: Take 3 clean and dry watch glass, each accurately weighs about 2.00g, and record it as M1, put it in the 80 ℃ drying oven and bake for 2-3 hours, weigh it and record it as M2, the ratio of two weighings M2 / M1 × 100% is the solid content.
③Viscosity: According to GB279481, measure the viscosity at 25 ° C with a rotary viscometer. The specific operation is: the sample glue with a constant temperature of more than 0.5 hours under the condition of 25 ℃, according to the viscosity provided by the supplier, select the appropriate rotary viscometer rotor for testing.
â‘£Acidity: According to GB / 1 1458-83, it is measured with a glass electrode acidity meter, and its PH value can also be detected with precision test paper.
The specific operation is: ignit the activated glass electrode in the sample chamber and titrate to the acidity at the end point.
⑤NCO value: According to the detection method of polyisocyanate, the NCO value of the curing agent is detected by chemical titration.
The specific operations are:
A. Preparation of reaction solution: analytically pure hexahydropyridine: acetone = 1:50;
B. Weigh about 2.00g of curing agent into 250ml Erlenmeyer flask pre-added with 10ml acetone;
C. Add 25ml reaction solution and let stand for 15 minutes;
D. Then add 20ml of absolute ethanol and 7 drops of bromide blue indicator;
E. Titrate with 0.5ml / L ethanol solution to the end;
F. At the same time, make a blank experiment to get the NCO value.
(3) Membrane detection
â‘ Indicators: transparency, uniformity, etc. can be determined by visual inspection;
â‘¡ Evaporation aid: GB100488, its content is detected by gas chromatography, and it can also be qualitatively judged by smell after heating according to actual production needs;
â‘¢Surface tension: The corona-treated film is tested with a dyne pen, but the dyne pen is not very accurate after a long time of use, and can be tested with a potion.
The specific operation is: use analytical pure formamide and ethylene glycol ether in a certain proportion to obtain a potion, and determine whether the film meets the requirements according to whether it is continuous on the film.
â‘£Ink: Due to the different printing conditions of the ink, the required pigments, binders and solvents of the ink are also different, so the control of the ink is different, but in general, the acidity, viscosity and chromaticity can be several In terms of, according to the needs of manufacturers.
In addition to the detection and control of raw materials, the pre-control also has an operation process and proper use, such as:
A. The production of retort-resistant composite bags requires the use of retort-resistant ink glue and film. If ordinary ink, glue or film is used, the quality requirements of the compound bag will naturally not be met. But these inks, glues or films are not unqualified raw materials and need to be used appropriately. A similar situation is that some manufacturers use external printing ink to represent the internal printing ink, and use isopropyl alcohol as the thinner of the internal printing ink. Because the film printed by the Liyin ink is compounded, and isopropyl alcohol contains active hydrogen, it will consume the effective group in the curing agent-isocyanate group (NGO). Causes poor adhesion and dry glue.
B. Glue preparation and guarantee: When using two-component polyurethane, it is necessary to mix the main agent, curing agent and diluent in a certain proportion and a certain order. If the compound is not prepared according to the proper ratio, the hydroxyl groups in the main agent and the isocyanate groups in the curing agent cannot react in proportion, resulting in incomplete reaction and affecting the bonding strength. If the main agent is mixed first Mixing with curing agent and adding thinner may cause surface quality problems after compounding. Therefore, the order of mixing cannot be changed. You must first add the thinner to the main agent or curing agent, and then dilute the main agent or curing agent to mix the two together. When the concentration is large, the reaction speed is much faster. After dilution, the reaction speed becomes slow, so that excessively large molecular clusters are not locally formed. Similarly, if the prepared glue is not used up within 8 hours, and it is not sealed and stored frozen, when mixed with glue, the surface quality of the composite product will also appear. The above two examples are given to illustrate: the use of suitable raw materials, the correct operation process and the raw materials that meet the standards complement each other, and together form the cornerstone of excellent products.
Post-mortem inspection and analysis
Ex-ante control is the behavior before printing and compounding, and ex-post testing and analysis is to detect and analyze the compound product, the purpose is to sub-inspect whether the product is qualified, as well as to analyze the unqualified product, draw experience, and ensure the integrity of the product rate.
Test method for finished products. For composite manufacturers, the testing of finished products should include the measurement of the peel strength and heat seal strength of the composite film and bag, the detection of the residual solvent content of the composite film and the comprehensive analysis of quality problems.
(1) Peeling strength and heat sealing strength of the composite bag: due to the different end use of the composite film bag, its index is different. The method is tested with an electronic tensile machine according to GB8808-88. For the composite film, it is cut into 15 × 200mm slim After stripping 5mm, use an electronic tension machine to gradually increase the tensile force to carry out the peeling test. The heat sealing strength of the composite wire is cut into 15 × 100mm thin strips and the same test is performed.
(2) The residual solvent content of the composite membrane: according to GB1004-88, the content is not more than 10mg / m2.
A. The hydrogen turret detector uses nitrogen as the carrier gas, the room temperature of the gas is 120-150 ℃, the temperature of the column chamber should not be lower than 80 ℃, and the difference between the two room temperatures should not be lower than 50 ℃;
B. Take 1ml and 2ml of solvent, put them in a 500ml conical flask with a silicone stopper preheated at 80 ℃ for 30 minutes, and heat at 80 ℃ for 30 minutes;
C. Take a 1ml sample and inject it to obtain a solvent peak;
D. Plot the peak height against the quality to get the standard curve;
E. Quickly cut the 0.2m2 composite membrane into a 500ml Erlenmeyer flask at 80 ℃ for a minute, and cap the silicone plug. Heat at 80 ° C for 30 minutes. Take a 1ml sample and inject it to obtain a solvent peak;
F. Find the corresponding mass on the standard curve.
(3) Comprehensive analysis of composite membrane quality problems: Using the above instruments and methods, combined with observation phenomena, you can make correct judgments on quality problems and find out the correct cause.
Frank Green Coffee Cup,Coffee Cups With Lids,Best Reusable Coffee Cup,Travel Coffee Cup
Shantou oudaya packaging co ltd , https://www.imloudaya.com