A plastic-based pH test reference material, its preparation method and application

Abstract

The present invention discloses a plastic-based pH test reference material, its preparation method and application, relating to the technical field of pH test. The present invention provides a plastic-based pH test reference material, which comprises the following components in parts by weight: 40-85 parts of an olefin polymer, 5-50 parts of a pH regulator, and 5-10 parts of a compatibilizer; wherein, the pH regulator is at least one of an acidic pH regulator and a basic pH regulator; the acidic pH regulator is at least one of phosphoric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate, and the basic pH regulator is at least one of sodium hydroxide, potassium hydroxide, and a strong base weak acid salt of potassium / sodium. The present invention provides a uniform and stable plastic-based pH test reference material, filling the blank in this field of the market.

Description

Technical Field

[0001] The present invention relates to the technical field of pH value testing, in particular to a plastic-based pH value testing reference material, a preparation method thereof, and an application thereof. Background Art

[0002] The pH value is one of the performance parameters of materials. The country has formulated a series of standards to standardize the pH value testing, and the pH value testing has covered fields such as industry, agriculture, medicine, environmental protection, and scientific research. During the pH value testing process of solid samples, it is often necessary to use media such as water to disperse the samples, and the pH value of the sample is obtained by measuring the pH value in the aqueous solution. Water will contact with carbon dioxide in the air to generate carbonic acid, thereby reducing the pH value of the aqueous solution and affecting the test results. At present, the reference materials for pH value testing on the market are mainly standard buffer solutions for pH meter calibration, which are made by configuring various pH primary reagents into different concentrations.

[0003] Polyethylene, as a general-purpose plastic, is widely used in fields such as daily necessities, construction, and the automotive manufacturing industry. At present, there is no plastic-based reference material for pH value testing. At present, there are requirements for testing the pH of textiles (GB / T32610 Technical Specification for Daily Protective Masks) and other plastic materials, but the testing process is easily interfered by water of different grades; due to the characteristic aggregated state structure of polymers, when there are acid-base groups, the process of testing pH is generally achieved by soaking to realize the migration of acid-base substances, and then the pH is tested; most of the existing pH standard solutions are solutions, and there are few reference materials for plastic matrices. The actual working conditions of the migration of acid-base substances in the polymer system cannot be simulated during the testing process, such as the influence of background CO2 and the influence of matrix water, etc.; it is necessary to develop a plastic-based reference material for pH determination of similar matrices. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to overcome the deficiencies of the above-mentioned prior art and provide a plastic-based pH value testing reference material.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is: a plastic-based pH value testing reference material, comprising the following components in parts by weight: 40-85 parts of an olefin polymer, 5-50 parts of a pH value regulator, and 5-10 parts of a compatibilizer; wherein, the pH value regulator is at least one of an acidic pH value regulator and a basic pH value regulator; the acidic pH value regulator is at least one of phosphoric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate, and the basic pH value regulator is at least one of sodium hydroxide, potassium hydroxide, and a strong base weak acid salt of potassium / sodium; the compatibilizer is a carboxylic anhydride grafted polyolefin compatibilizer.

[0006] The present invention provides a plastic-based pH test reference material by melting and dispersing an acid-base regulator and a polymer plastic aggregate at high temperature, filling the gap in this field of the market.

[0007] Preferably, the strong base weak acid salts of potassium / sodium are at least one of dipotassium hydrogen phosphate, disodium hydrogen phosphate, and sodium bicarbonate, and the olefin polymers are at least one of polypropylene, polyethylene, and polystyrene.

[0008] Preferably, when the pH value of the plastic-based pH test reference material is 2-4, the pH value regulator is a mixture of phosphoric acid, potassium dihydrogen phosphate, and / or sodium dihydrogen phosphate, and the molar ratio of phosphoric acid, potassium dihydrogen phosphate, and / or sodium dihydrogen phosphate is: phosphoric acid, potassium dihydrogen phosphate, and / or sodium dihydrogen phosphate = (1-2):(1-2);

[0009] When the pH value of the plastic-based pH test reference material is 6-8, the pH value regulator is a mixture of an acidic pH value regulator and a basic pH value regulator. The acidic pH value regulator is at least one of potassium dihydrogen phosphate and sodium dihydrogen phosphate, and the basic pH value regulator is at least one of dipotassium hydrogen phosphate and disodium hydrogen phosphate; wherein, the molar ratio of potassium dihydrogen phosphate and / or sodium dihydrogen phosphate, dipotassium hydrogen phosphate and / or disodium hydrogen phosphate is: potassium dihydrogen phosphate and / or sodium dihydrogen phosphate: dipotassium hydrogen phosphate and / or disodium hydrogen phosphate = (0.2-2):(0.2-2);

[0010] When the pH value of the plastic-based pH test reference material is 9-10, the pH value regulator is a basic pH value regulator, and the basic pH value regulator is a mixture of sodium hydroxide and / or potassium hydroxide, and sodium bicarbonate; the molar ratio of sodium bicarbonate, potassium hydroxide, and / or sodium hydroxide is: sodium bicarbonate: potassium hydroxide and / or sodium hydroxide = (2-4):1;

[0011] When the pH value of the plastic-based pH test reference material is 11-13, the pH value regulator is a basic pH value regulator, and the basic pH value regulator is a mixture of sodium hydroxide and / or potassium hydroxide, dipotassium hydrogen phosphate, and / or disodium hydrogen phosphate. The molar ratio of sodium hydroxide and / or potassium hydroxide, dipotassium hydrogen phosphate, and / or disodium hydrogen phosphate is: sodium hydroxide and / or potassium hydroxide: dipotassium hydrogen phosphate and / or disodium hydrogen phosphate = (0.5-2):(0.5-2).

[0012] After a large number of experiments and explorations, the applicant found that there are some phase structures in the polymer chains of plastics. The pH value acid or base regulators, as small solid or liquid molecules with small sizes, can be dispersed in the phase structures. In addition, the theoretical pH range can be calculated through the dissociation constants of the acid-base regulators; pH standard substances with different ranges are prepared by adding a certain proportion of acid-base regulators; when the acidic pH value regulator or the alkaline pH value regulator is selected with the above specific components and weight ratios, the prepared plastic-based pH value test standard substance is more uniform and stable.

[0013] Preferably, the compatibilizer is a carboxylic anhydride grafted polyolefin compatibilizer; more preferably, the compatibilizer is at least one of maleic anhydride grafted POE and maleic anhydride grafted polypropylene. In the present invention, the carboxylic anhydride grafted polyolefin compatibilizer is selected. Other types of compatibilizers such as imide type and isocyanate type belong to reactive types, and some of them have certain toxicity and poor compatibility with this system, so they are not selected. According to the properties and polarities of acids and bases, maleic anhydride grafted POE or maleic anhydride grafted polypropylene is added as the compatibilizer in the present invention to improve the binding force between the acid-base regulator and the resin and improve the stability.

[0014] Preferably, the plastic-based pH value test standard substance further comprises 0.2-0.8 parts by weight of a dispersant, 0.2-0.6 parts by weight of a light stabilizer, and 0.2-0.6 parts by weight of an antioxidant.

[0015] Preferably, the dispersant is at least one of white mineral oil and paraffin; the light stabilizer is at least one of benzotriazole light stabilizers and hindered amine light stabilizers; the antioxidant is at least one of hindered phenol antioxidants and phosphite antioxidants.

[0016] In addition, the present invention provides a preparation method of the plastic-based pH value test standard substance, comprising the following steps:

[0017] (1) Weigh various raw materials according to the ratio;

[0018] (2) Add the various raw materials in step (1) into a mixer and mix evenly to obtain a mixed material;

[0019] (3) Add the mixed material obtained in step (2) into a twin-screw extruder for extrusion granulation to obtain the plastic-based pH value test standard substance.

[0020] Preferably, in step (2), the mixing time in the mixer is 3-5 min; in step (3), the temperature of the first zone of the twin-screw extruder is 90-100 °C, the temperature of the second zone is 160-190 °C, the temperature of the third zone is 200-210 °C, the temperature of the fourth zone is 205-210 °C, the temperature of the fifth zone is 190-200 °C; the residence time is 1-2 min, and the pressure is 10-15 Mpa.

[0021] Furthermore, the present invention provides an application of the plastic-based pH test reference material in the pH test of solid substances.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention provides a uniform and stable plastic-based pH test reference material, filling the gap in this field of the market. Specific Embodiments

[0023] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0024] In the embodiments, unless otherwise specified, the experimental methods used are all conventional methods, and the materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels; the antioxidants, dispersants, compatibilizers, and light stabilizers used in the embodiments and comparative examples of the present invention are exactly the same.

[0025] The raw materials used in the embodiments and comparative examples are described as follows, but are not limited to these materials:

[0026] Olefin polymer 1: HDPE, grade 5000S, manufacturer: Lanzhou Petrochemical;

[0027] Olefin polymer 2: PP, model HP500N, manufacturer: CNOOC and Shell Petrochemical Company Limited, Huizhou;

[0028] pH regulator

[0029] Acidic pH regulator:

[0030] Phosphoric acid, potassium dihydrogen phosphate, and sodium dihydrogen phosphate are all commercially available ordinary products;

[0031] Sulfuric acid and nitric acid are all commercially available ordinary products;

[0032] Alkaline pH regulator:

[0033] Sodium hydroxide, potassium hydroxide, dipotassium hydrogen phosphate, disodium hydrogen phosphate, and sodium bicarbonate are all commercially available ordinary products;

[0034] Ethylenediamine and calcium hydroxide are all commercially available ordinary products;

[0035] Compatibilizer 1: maleic anhydride grafted POE, grade GR216, manufacturer: The Dow Chemical Company, USA;

[0036] Compatibilizer 2: ethylene-methyl acrylate EMA AX8900, manufacturer: Arkema, France;

[0037] Dispersant: white oil, at 40 °C, kinematic viscosity 4-5 (cSt), commercially available;

[0038] Light stabilizer: hindered amine light stabilizer, HALS-944, commercially available;

[0039] Antioxidant: Antioxidant 1: hindered phenol antioxidant 1010 (pentaerythritol tetrakis [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate]); Antioxidant 2: phosphite antioxidant 168 (tris [2,4-di-tert-butylphenyl] phosphite), commercially available;

[0040] Examples 1-15 and Comparative Examples 1-5

[0041] The components and parts by weight of the plastic-based pH value test reference materials of Examples 1-15 and Comparative Examples 1-5 are shown in Tables 1, 2, and 3. Among them, the preparation method of the plastic-based pH value test reference materials in the examples and comparative examples includes the following steps:

[0042] (1) Weigh various raw materials according to the ratio;

[0043] (2) Add the various raw materials in step (1) into a mixer and mix evenly to obtain a mixed material; among them, the mixing time in the mixer is 3-5 min;

[0044] (3) Add the mixed material obtained in step (2) into a twin-screw extruder for extrusion granulation to obtain the plastic-based pH value test reference material; among them, the temperature of the first zone of the twin-screw extruder is 90-100 °C, the temperature of the second zone is 160-190 °C, the temperature of the third zone is 200-210 °C, the temperature of the fourth zone is 205-210 °C, and the temperature of the fifth zone is 190-200 °C; the residence time is 1-2 min, and the pressure is 10-15 Mpa.

[0045] Table 1

[0046]

[0047]

[0048] Table 2

[0049]

[0050]

[0051] Table 3

[0052]

[0053] Performance test

[0054] Homogeneity test - pH value test:

[0055] Reagents: Sodium chloride solution (10 g / L, pH (7.0 ± 0.2));

[0056] Apparatus: pH meter, accurate to 0.001 pH unit, with temperature compensation function;

[0057] Test procedure: Add (10 ± 0.5) g of the plastic-based pH test reference material prepared in the examples and comparative examples of the present invention and (50 ± 2) mL of sodium chloride solution into a flask, cover the lid, place it on an oscillator and shake for (60 ± 5) min, then let it stand for (5 - 10) min; Transfer the solution in the flask to a clean beaker and measure the pH value of the extract with a pH meter;

[0058] The tolerance of the pH reference material of the present invention is required to be ±0.01;

[0059] The test results are shown in Table 4 - 6:

[0060] Table 4

[0061] pH value Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 1 2.794 3.215 2.416 2.793 2.856 2.521 4.112 2 2.796 3.214 2.413 2.794 2.854 2.523 4.113 3 2.795 3.213 2.415 2.795 2.855 2.524 4.117 Range of extreme values 0.002 0.002 0.003 0.002 0.002 0.003 0.005 Whether the requirements are met Yes Yes Yes Yes Yes Yes Yes

[0062] Table 5

[0063]

[0064] Table 6

[0065]

[0066]

[0067] Conclusion: The extreme value differences of the samples in the examples of the present invention are all less than 0.01, and they are relatively uniform and stable.

[0068] Stability verification

[0069] Stability is another important parameter for measuring reference materials. When examining whether there are differences between the average values of two groups of data, the independent sample t-test method can be used to evaluate the stability of the reference material. If the relationship between the statistic t and ta at the significance level a and the degree of freedom f = n1 + n2 - 2 is t < ta(f), it is considered that the characteristic quantity value of the reference material has not changed significantly, otherwise it is considered that the characteristic quantity value of the reference material has changed significantly. The time intervals for the test process are 0 months, 1 month, 3 months, and 6 months. At each time point, 6 samples are randomly selected, and each sample is measured in parallel 2 times. The results of measuring the plastic-based pH reference material are shown in Table 5, calculate the t value of the test data statistics, and look up the critical value t 0.05(11) , if t < t 0.05(11) , it indicates that the content value of the sample has not changed significantly, and the prepared plastic-based pH reference material is stable. The statistical value t is obtained by the following formula;

[0070] To ensure the accuracy of the average value and the standard deviation, n ≥ 6. If t < the critical value t of the significance level a (usually a = 0.05) with degrees of freedom n - 1 a(n-1) , there is no significant difference between the average value and the standard / reference value, and the test and recording results of each product are shown in Table 7-9 below;

[0071]

[0072] In the formula: - The average value of n measurements;

[0073] μ - The standard / reference value;

[0074] n - The number of measurements;

[0075] S - The standard deviation of the results of n measurements.

[0076] Table 7

[0077]

[0078] Table 8

[0079]

[0080] Table 9

[0081]

[0082] Conclusion: The critical value t a(11) = 1.796. The t values of the products in each example are all less than the critical value, indicating that each product has good stability, which is similar to the results in Table 4.

[0083] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A plastic-based pH test reference material, characterized in that, It comprises the following components in parts by weight: 40 - 85 parts of an olefin polymer, 5 - 50 parts of a pH regulator, and 5 - 10 parts of a compatibilizer; wherein, the pH regulator is at least one of an acidic pH regulator and a basic pH regulator; the acidic pH regulator is at least one of phosphoric acid, sodium dihydrogen phosphate, and potassium dihydrogen phosphate, and the basic pH regulator is at least one of sodium hydroxide, potassium hydroxide, and a strong base weak acid salt of potassium / sodium; the compatibilizer is maleic anhydride grafted POE or maleic anhydride grafted polypropylene.

2. For the plastic-based pH test reference material according to claim 1, when the pH value of the plastic-based pH test reference material is 2-4, the pH regulator is a mixture of phosphoric acid, potassium dihydrogen phosphate and / or sodium dihydrogen phosphate, and the molar ratio of phosphoric acid, potassium dihydrogen phosphate and / or sodium dihydrogen phosphate is: phosphoric acid: potassium dihydrogen phosphate and / or sodium dihydrogen phosphate = (1-2):(1-2); When the pH value of the plastic-based pH test reference material is 6-8, the pH regulator is a mixture of an acidic pH regulator and a basic pH regulator. The acidic pH regulator is at least one of potassium dihydrogen phosphate and sodium dihydrogen phosphate, and the basic pH regulator is at least one of dipotassium hydrogen phosphate and disodium hydrogen phosphate; wherein, The molar ratio of potassium dihydrogen phosphate and / or sodium dihydrogen phosphate to dipotassium hydrogen phosphate and / or disodium hydrogen phosphate is: potassium dihydrogen phosphate and / or sodium dihydrogen phosphate : dipotassium hydrogen phosphate and / or disodium hydrogen phosphate = (0.2 - 2) : (0.2 - 2); When the pH value of the plastic-based pH test reference material is 9 - 10, the pH regulator is a basic pH regulator, and the basic pH regulator is a mixture of sodium hydroxide and / or potassium hydroxide and sodium bicarbonate; the molar ratio of sodium bicarbonate to potassium hydroxide and / or sodium hydroxide is: sodium bicarbonate : potassium hydroxide and / or sodium hydroxide = (2 - 4) : 1; When the pH value of the plastic-based pH test reference material is 11 - 13, the pH regulator is a basic pH regulator, and the basic pH regulator is a mixture of sodium hydroxide and / or potassium hydroxide and dipotassium hydrogen phosphate and / or disodium hydrogen phosphate, and the molar ratio of sodium hydroxide and / or potassium hydroxide to dipotassium hydrogen phosphate and / or disodium hydrogen phosphate is: sodium hydroxide and / or potassium hydroxide : dipotassium hydrogen phosphate and / or disodium hydrogen phosphate = (0.5 - 2) : (0.5 - 2).

3. The plastic-based pH test reference material according to claim 1, characterized in that, The plastic-based pH test reference material further comprises 0.2 - 0.8 part by weight of a dispersant, 0.2 - 0.6 part by weight of a light stabilizer, and 0.2 - 0.6 part by weight of an antioxidant.

4. The plastic-based pH test reference material according to claim 3, characterized in that, The dispersant is at least one of white oil and paraffin; the light stabilizer is at least one of benzotriazole light stabilizers and hindered amine light stabilizers; the antioxidant is at least one of hindered phenol antioxidants and phosphite antioxidants.

5. A preparation method of the plastic-based pH test reference material according to any one of claims 1-4, characterized in that, It comprises the following steps: (1) Weigh various raw materials according to the ratio. (2) Add the various raw materials in step (1) into a mixer and mix evenly to obtain a mixed material. (3) Add the mixed material obtained in step (2) into a twin-screw extruder for extrusion granulation to obtain the plastic-based pH test reference material.

6. The preparation method of the plastic-based pH test reference material according to claim 5, characterized in that, In step (2), the mixing time in the mixer is 3 - 5 min; in step (3), the temperature of the first zone of the twin-screw extruder is 90 - 100 °C, the temperature of the second zone is 160 - 190 °C, the temperature of the third zone is 200 - 210 °C, the temperature of the fourth zone is 205 - 210 °C, the temperature of the fifth zone is 190 - 200 °C; the residence time is 1 - 2 min, and the pressure is 10 - 15 Mpa.

7. Application of the plastic-based pH test reference material according to any one of claims 1-4 in the pH test of solid substances.

Images