A method for rapidly detecting the weather resistance of titanium dioxide in a PVC system

Abstract

The application discloses a kind of fast detection titanium dioxide in PVC system weather resistance method, comprising the following steps: S1.PVC resin, plasticizing modifier, mixed uniformly, to obtain masterbatch;S2.respectively take the masterbatch, titanium dioxide to be measured, not weatherable pigment, stabilizer, mixed uniformly;Then forming preparation is test sample;S3.the part of the test sample is covered, then isolated air is aged and handled, visual observation or measurement is not covered and the color difference of covered place.The application is more suitable for the use system of PVC product, is more environmentally friendly on the basis of guaranteeing test accuracy;Add not weatherable pigment in formula, shorten test time;By pre-mixed masterbatch, reduce operation error, improve test efficiency;Compared with rhodamine, acid solubility and other test methods, more suitable for the specific formula system of downstream PVC product.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of titanium dioxide detection, and particularly relates to a method for rapidly detecting weather resistance of titanium dioxide in a PVC system. BACKGROUND

[0002] Titanium dioxide (TiO2) pigment is an important component for ensuring the weather resistance of PVC profiles. It can absorb ultraviolet light to reduce the discoloration of resin inside the profile due to light and oxygen aging, and it can also cover the discoloration of PVC through scattering and refraction of visible light. There is a significant difference between general specification titanium dioxide and weather-resistant specification titanium dioxide in terms of weather resistance of PVC profiles. The acid solubility method is generally used to evaluate the compactness of TiO2 surface coating and its weather resistance grade.

[0003] However, the acid solubility method is not suitable for titanium dioxide base materials, and it cannot effectively simulate the state in the PVC system. The issuance and implementation of the lead ban also make PVC profiles, pipes and other products no longer add lead salt stabilizers. The detection formula proposed by the applicant (patent CN201910552021.7) which takes lead salt stabilizer as the core is no longer applicable to the current industry. Therefore, a new method for rapidly detecting the weather resistance of titanium dioxide in the PVC system is urgently needed. SUMMARY

[0004] The purpose of the present application is to provide a method for rapidly detecting the weather resistance of titanium dioxide in a PVC system to solve the problems of the prior art.

[0005] The purpose of the present application is achieved by the following technical solution:

[0006] A method for rapidly detecting the weather resistance of titanium dioxide in a PVC system, comprising the following steps:

[0007] S1. Preparation of masterbatch: 80-120 parts of PVC resin, 10-13 parts of plasticizing modifier, and 10-13 parts of plasticizing modifier are mixed uniformly to obtain a masterbatch;

[0008] S2. Test sample preparation: the masterbatch, the titanium dioxide to be tested, the non-weather-resistant pigment, and the stabilizer are mixed uniformly; the amount of the titanium dioxide to be tested, the non-weather-resistant pigment, and the stabilizer is 4-8%, 4-8%, and 2-4% of the mass of the masterbatch, respectively; the stabilizer is a calcium-zinc stabilizer; and then the test sample is prepared by molding;

[0009] S3. Weather resistance test: part of the test sample is covered, then aged in isolation from air, and the color difference between the uncovered and covered parts is observed or measured to characterize the weather resistance.

[0010] Preferably, the weather-resistant pigment is one or a mixture of one or more selected from the group consisting of: yellow pigment, molybdenum chromium red, zinc chromium yellow, red lead or titanium dioxide base without inorganic coating treatment.

[0011] The plasticizing modifier comprises 2-3 parts by weight of ACR and 8-10 parts by weight of CPE.

[0012] Preferably, in the calcium-zinc stabilizer in step S2, the mass percentage of calcium is 3.0-3.5%, and the mass percentage of zinc is 4.0-4.5%.

[0013] Preferably, the forming step in step S2 is to first roll the sheet and then hot-press form.

[0014] Preferably, the rolling temperature is 175-190 DEG C, the rolling distance is 0.1-0.4 mm, the speed is 5-25 rpm, and the rolling time is 2.5-5 min.

[0015] Preferably, the hot-press forming temperature is 160-180 DEG C.

[0016] Preferably, the thickness of the test sheet is 1-2 mm.

[0017] Preferably, in step S3, the air isolation is achieved by adding water or sealing the package with transparent material.

[0018] Preferably, in step S3, the aging treatment is achieved by using a xenon lamp, an ultraviolet lamp or exposure to sunlight at a temperature above 25 DEG C for 3-5 h.

[0019] Preferably, in step S3, the color difference meter is used to test the color difference DE of the test sheet at the unshielded and shielded positions, and the calculation formula is as follows:

[0020]

[0021] Wherein, L1 is the lightness of the test sheet at the unshielded position, L0 is the lightness of the test sheet at the shielded position, a1 is the red-green value of the test sheet at the unshielded position, a0 is the red-green value of the test sheet at the shielded position, b1 is the yellow-blue value of the test sheet at the unshielded position, and b0 is the yellow-blue value of the test sheet at the shielded position.

[0022] The calcium-zinc stabilizer is used to replace the banned lead salt stabilizer, which is more suitable for the use system of PVC products, is more environmentally friendly on the basis of ensuring test accuracy, and makes the sample produce more obvious color change in a short time of aging treatment, thereby shortening the test time; the pre-prepared mixed master batch reduces the operation error and improves the test efficiency; compared with the rhodamine and acid solubility test method, the method is more suitable for the specific formula system of downstream PVC products. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 are hue pictures of different titanium dioxide samples provided in Example 2 after xenon lamp aging treatment. DETAILED DESCRIPTION

[0024] The method for rapidly detecting the weather resistance of titanium dioxide in a PVC system provided by the present application comprises the following steps:

[0025] S1. Preparation of a masterbatch: 80-120 parts of PVC (polyvinyl chloride) resin, 10-13 parts of a plasticizing modifier, are mixed uniformly to obtain a masterbatch; the mixing can be carried out in a high-speed mixer, and the mixing time is preferably 10-20 min; the PVC resin can be a resin with a grade of SG-3, SG-5, SG-8, etc.

[0026] S2. Preparation of a test sample: the masterbatch, the titanium dioxide to be tested, the non-weatherable pigment, and the stabilizer are mixed uniformly; the amounts of the titanium dioxide to be tested, the non-weatherable pigment, and the stabilizer are 4-8%, 4-8%, and 2-4% of the mass of the masterbatch, respectively; the stabilizer is a calcium-zinc stabilizer; then a test sample is prepared by molding; the non-weatherable pigment herein mainly refers to a pigment with a lower weather resistance than the titanium dioxide to be tested; preferably, the non-weatherable pigment is one or a mixture of more than one selected from the following pigments: cadmium yellow, molybdenum-chromium red, zinc-chromium yellow, red lead, or titanium dioxide base without inorganic coating treatment.

[0027] S3. Weather resistance test: part of the test sample is covered, and then aging treatment is carried out in an air-tight manner; the color difference between the uncovered part and the covered part is observed visually or measured; the degree of change in hue is used to represent the weather resistance; the greater the color difference, the poorer the weather resistance. Preferably, the covered area is half of the area of the test sample, which facilitates comparison.

[0028] The plasticizing modifier can improve the plasticizing performance of the PVC resin; preferably, 2-3 parts by weight of ACR (acrylic copolymer) and 8-10 parts by weight of CPE (chlorinated polyethylene) are used; the ACR can promote the melting and plasticizing of the PVC resin, reduce the temperature in the molding process, improve the melt strength, and improve the appearance quality of the product, without reducing the rigidity of the rigid PVC; the CPE, as a toughening agent, can improve the impact resistance of the PVC product. However, the plasticizing modifier is generally an organic substance, and it is not easy to mix uniformly with other components in the PVC resin system.

[0029] The application replaces the lead salt stabilizer in the prior art with a calcium-zinc stabilizer in the PVC resin test system, and adds a weathering-resistant pigment to the system. The calcium-zinc stabilizer can prevent the decomposition, yellowing and release of HCl gas of PVC resin during high-temperature processing. It replaces the lead salt stabilizer in the prior art, is more environmentally friendly, has better compatibility with the PVC system, and has better test accuracy. However, the calcium-zinc stabilizer does not have the effect of reacting with titanium white to generate gray substances under the presence of light and water to accelerate the test as the lead salt stabilizer does. Therefore, the application adds a weathering-resistant pigment, which can cause a relatively obvious color change of the sample after a short aging treatment, thereby shortening the test time.

[0030] PVC, ACR and CPE are organic polymers and are not easy to mix uniformly, which affects the test accuracy. Therefore, the application first pre-mixes the modifier (ACR and CPE) and PVC, mixes them uniformly through high-speed stirring, and obtains a mixed masterbatch for standby. By pre-preparing the mixed masterbatch, the operation error can be reduced and the test efficiency can be improved. Then, the titanium white powder to be tested, the stabilizer and the weathering-resistant pigment are mixed to prepare a test sample. Since the weathering-resistant pigment is added, the color of the test sample can quickly change after a short aging treatment, thereby reducing the test time. In addition, the application selects to cover a part of the test sample for testing. The test sample covered does not undergo photocatalysis and can be directly compared with the test sample not covered, which is more convenient and fast. In the prior art, rhodamine experiments and acid solubility experiments are used to characterize the weather resistance of titanium white. The rhodamine experiment simulates the photocatalytic effect of titanium white after being exposed to light in a liquid. The acid solubility experiment tests the coating integrity of inorganic silicon and aluminum of titanium white by acidolysis. Both methods infer the weather resistance of titanium white from the experimental results. However, in specific applications, titanium white powder and PVC resin are processed by hot melt blending. The weather resistance is affected by many factors, and the above methods cannot directly reflect the weather resistance of downstream products. Therefore, the application directly combines titanium white powder and the PVC system to prepare a test sample, and characterizes the weather resistance of titanium white powder by color difference change. Compared with the rhodamine and acid solubility test methods, the application is more suitable for the specific formulation system of downstream PVC products.

[0031] The calcium-zinc stabilizer in step S2 is synthesized by using a special compounding process with calcium salt, zinc salt, lubricant, antioxidant and the like as main components. Preferably, the mass percentage of calcium is 3.0-3.5%, and the mass percentage of zinc is 4.0-4.5%.

[0032] Preferably, the forming step S2 is first rolling down the sheet by roller milling, and then hot-pressing forming. Through the dispersion effect of roller milling, the titanium dioxide to be tested can be fully mixed and dispersed uniformly with PVC resin and other raw materials, and then hot-pressing forming into a test sample sheet of a certain thickness for convenient observation and test of color difference change. The thickness of the film layer is also an important factor affecting the accuracy of the color difference meter test, and the thickness is preferably 1-2 mm.

[0033] Preferably, the roller milling temperature is 175-190°C, the roller spacing is 0.1-0.4 mm, the speed is 5-25 rpm, and the roller milling time is 2.5-5 min.

[0034] Preferably, the hot-pressing forming temperature is 160-180°C.

[0035] Preferably, the air isolation in step S3 is achieved by adding water or by placing the test sample sheet in a transparent and airtight self-sealing bag.

[0036] Preferably, the aging treatment in step S3 is achieved by xenon lamp aging treatment, ultraviolet lamp irradiation or outdoor exposure (above 25°C sunny day), and the treatment time is 3-5 h.

[0037] Preferably, step S3 uses a color difference meter to test the color difference ΔE of the test sample sheet at the unshielded and shielded positions, and the color difference ΔE calculation formula is as follows:

[0038]

[0039] Wherein, L1 is the lightness of the test sample sheet at the unshielded position, L0 is the lightness of the test sample sheet at the shielded position, a1 is the red-green value of the test sample sheet at the unshielded position, a0 is the red-green value of the test sample sheet at the shielded position, b1 is the yellow-blue value of the test sample sheet at the unshielded position, and b0 is the yellow-blue value of the test sample sheet at the shielded position.

[0040] Example 1

[0041] Take 100 parts of PVC resin (resin grade SG-5), 2.5 parts of ACR (acrylic copolymer) and 9 parts of CPE (chlorinated polyethylene) by weight, and pre-mix them for 15 min by a high-speed mixer to prepare a master batch.

[0042] Take 50 g of the above master batch, 4 g of titanium dioxide to be tested, 2 g of calcium-zinc stabilizer and 2 g of titanium dioxide base material (without coating treatment) and mix them uniformly. Set the temperature of the two-roll mill to 180°C, the roller spacing to 0.3 mm and the speed to 20 rpm. After the roller temperature stabilizes, pour the pre-mixed material into the rollers to start roller milling for 3 min and then roll down the sheet. Hot-pressing forming by a vulcanizing machine to prepare a uniform color sheet with a thickness of 1 mm.

[0043] Comparative Example 1

[0044] Take 100 g of PVC resin (resin grade SG-5), 4 g of titanium white powder to be tested, 2 g of calcium zinc stabilizer, mix uniformly, set the temperature of the double roller mill to 180℃, the roller spacing is 0.3mm, and the speed is adjusted to 20rpm; after the roller temperature is stable, pour the premixed material into the roller gap and start the roller processing for 3 minutes, then take out the sheet; through the vulcanizing machine hot pressing, prepare a uniform color sheet with a thickness of 1mm.

[0045] Comparative Example 2

[0046] Take 50 g of masterbatch (same as Example 1), 4 g of titanium white powder to be tested, 2 g of calcium zinc stabilizer, mix uniformly, set the temperature of the double roller mill to 180℃, the roller spacing is 0.3mm, and the speed is adjusted to 20rpm; after the roller temperature is stable, pour the premixed material into the roller gap and start the roller processing for 3 minutes, then take out the sheet; through the vulcanizing machine hot pressing, prepare a uniform color sheet with a thickness of 1mm.

[0047] Put the samples prepared in Example 1 and Comparative Examples 1-2 into the same water tank (a, b, c are three different grades of titanium white), cover half of each sample with a cover, and then put it into a xenon lamp for aging treatment (blackboard temperature 65℃, 0.51W / m 2 ), observe and measure the color difference of the uncovered and covered parts at different test times, the results are shown in Table 1.

[0048] Prepare samples according to the downstream PVC profile production formula using a, b, and c three different grades of titanium white, and perform a conventional xenon lamp aging experiment (blackboard temperature 65℃, 0.51W / m 2 ), the results are shown in Table 2.

[0049] Table 1 Weather resistance of samples prepared by different treatment methods

[0050]

[0051] Table 2

[0052]

[0053] From Table 1, it can be seen that using the method provided in the present application, the color change occurs significantly after 4h of testing in the xenon lamp, while Comparative Examples 1-2 do not add weather-resistant pigments (titanium white base), even if the test time is extended to 48h, the color difference change is not achieved, thus proving that the present application can significantly shorten the test time.

[0054] From Table 2, it can be seen that the weather resistance test results of the method provided in the present application and the weather resistance test results of the conventional PVC product are consistent in trend, the weather resistance of titanium white a is greater than that of titanium white b, which is greater than that of titanium white c, proving that the test method provided in the present application can accurately characterize the weather resistance of titanium white. From Table 2, it can also be seen that the conventional PVC product weather resistance test needs more than 2000h, and there is no obvious change in color difference within the test time of less than 2000h, further proving that the test method provided in the present application can quickly test the weather resistance of titanium white.

[0055] Example 2

[0056] Take 100 parts of PVC resin (resin grade SG-5), 3 parts of ACR (acrylic copolymer), and 10 parts of CPE (chlorinated polyethylene), and pre-mix them for 20 minutes by a high-speed mixer to prepare a masterbatch.

[0057] Take 50g of the above masterbatch, 3g of titanium white to be tested (9 different grades of products), 1.5g of calcium-zinc stabilizer, and 3g of titanium white base, and mix them uniformly. Set the temperature of the double roller mill to 180℃, the roller spacing to 0.3mm, and the speed to 20rpm. After the roller temperature is stabilized, pour the pre-mixed material into the rollers to start the roll processing for 3 minutes, and then take out the sheet. Through hot pressing by a vulcanizing machine, a uniform color sheet with a thickness of 1mm is prepared.

[0058] Put the sample sheet prepared in Example 2 into the same water tank, cover half of each sample sheet with a cover, and then put it into a xenon lamp (blackboard temperature 65℃, 0.51W / m 2 ) for aging treatment. After 4 hours of visual observation, test the color difference between the uncovered and covered parts, and the results are shown in Table 2. Figure 1

[0059] Figure 1 The first column in Table 2 is the covered sample sheet, and the second column is the uncovered sample sheet.

[0060] The weather resistance is graded as ABCDE, with the smallest color difference being A, slightly worse being B, and so on.

[0061] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to these embodiments once they understand the basic creative concept. Therefore, the appended claims are intended to include the preferred embodiments and all changes and modifications falling within the scope of the present application. Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.​

Claims

1. A method for rapidly detecting the weather resistance of titanium dioxide in a PVC system, characterized in that, The method comprises the following steps: S1. Preparation of the masterbatch: 80-120 parts of PVC resin, 10-13 parts of plasticizing modifier, are mixed uniformly to obtain a masterbatch; the plasticizing modifier comprises 2-3 parts of ACR and 8-10 parts of CPE by weight; S2. Preparation of the test sample: the masterbatch, the titanium white powder to be tested, the weather-resistant pigment, and the stabilizer are mixed uniformly; the amounts of the titanium white powder to be tested, the weather-resistant pigment, and the stabilizer are 4-8%, 4-8%, and 2-4% of the mass of the masterbatch, respectively; the stabilizer is a calcium-zinc stabilizer; then, the test sample is prepared by molding; the weather-resistant pigment is a titanium white powder base without inorganic coating treatment; S3. Weather resistance test: part of the test sample is covered, then is subjected to aging treatment in an air-tight manner, and the color difference between the uncovered part and the covered part is observed visually or measured, so as to characterize the weather resistance.

2. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 1, wherein the calcium-zinc stabilizer in step S2 comprises 3.0-3.5% of calcium by mass percentage and 4.0-4.5% of zinc by mass percentage.

3. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 1, wherein the molding step in step S2 is first rolling down the sheet, and then hot-pressing molding.

4. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 3, wherein the rolling temperature is 175-190°C, the roller spacing is 0.1-0.4 mm, the speed is 5-25 rpm, and the rolling time is 2.5-5 min.

5. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 3, wherein the hot-pressing molding temperature is 160-180°C.

6. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 1, wherein the thickness of the test sample is 1-2 mm.

7. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 1, wherein the air-tight manner in step S3 is water or transparent material sealing packaging.

8. The method for rapidly detecting the weather resistance of titanium white powder in a PVC system according to claim 1, wherein the aging treatment in step S3 is a xenon lamp, an ultraviolet lamp, or a sunny day exposure aging treatment at 25°C or above, and the treatment time is 3-5 h. Step S3 uses a color difference meter to test the color difference ΔE of the test sample at the uncovered part and the covered part, and the calculation formula is as follows: wherein L1 is the lightness of the test sample at the uncovered part, L0 is the lightness of the test sample at the covered part, a1 is the red-green value of the test sample at the uncovered part, a0 is the red-green value of the test sample at the covered part, b1 is the yellow-blue value of the test sample at the uncovered part, and b0 is the yellow-blue value of the test sample at the covered part. ​ ​ ​ ​ ​ 9. The method for rapidly detecting the weather resistance of titanium dioxide in a PVC system according to claim 1, characterized in that, ​ Set 1 ​

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