A three-layer PET structure erasable whiteboard and its preparation process

Abstract

The present invention relates to the technical field of polyethylene terephthalate, and discloses a three-layer PET structure erasable whiteboard and a preparation process thereof. The three-layer PET structure erasable whiteboard consists of a wear-resistant modified PET upper layer, a PET middle layer and a PET lower layer, with EVA hot melt adhesive between each PET layer. Polyethylene terephthalate and dispersant-modified titanium dioxide are melt-extruded, granulated, and compression-molded to obtain a wear-resistant modified PET layer. The sodium sulfonate polyester dispersant contains a large number of sodium sulfonate groups, which can achieve surface modification and dispersion effects on titanium dioxide, thereby improving the dispersibility of titanium dioxide. At the same time, the sodium sulfonate polyester dispersant contains terephthalate structural units similar to PET, so that the modified titanium dioxide has better compatibility with PET polyester and is evenly dispersed in the PET matrix, so that the PET layer exhibits good wear resistance and mechanical properties.

Description

Technical Field

[0001] The invention relates to the technical field of polyethylene terephthalate, in particular to a three-layer PET structured erasable whiteboard and a preparation process thereof. Background Art

[0002] Whiteboards are a common office supply, mainly including enamel boards, glass boards, polyethylene terephthalate boards, etc. Among them, PET polyethylene terephthalate has good mechanical properties, high heat resistance, and light weight. The whiteboards made of it have the advantages of being light and portable. Improving the mechanical strength, wear resistance and other properties of polyethylene terephthalate will help expand its practical application in plastic products such as whiteboards. Titanium dioxide is a common white pigment that is cheap, easy to obtain, non-toxic and pollution-free. It is compounded with plastics such as PET, polypropylene, and polycarbonate to obtain white plastic products. However, titanium dioxide is prone to agglomeration and has poor compatibility with polymer plastic matrices such as PET. Adding it to plastics will affect their mechanical properties. Therefore, the development of high-performance dispersants is a research hotspot. Patent CN103937173B discloses a polyester titanium dioxide masterbatch for label film and its preparation method. Using PET, titanium dioxide, a fluorescent brightener, and a dispersant as raw materials, the masterbatch improves the dispersibility of the titanium dioxide pigment, enhancing the whiteness and brightness of the polyester label film. The invention aims to utilize a sodium sulfonate polyester dispersant to improve the dispersibility and compatibility of titanium dioxide with PET, resulting in a PET material with excellent wear resistance and mechanical properties, and a rewritable whiteboard. Summary of the Invention

[0003] The technical problem solved by the invention is to provide a three-layer PET structure erasable whiteboard with excellent wear resistance and mechanical properties.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: a three-layer PET structure erasable whiteboard, which consists of a wear-resistant modified PET upper layer, a PET middle layer and a PET lower layer, and EVA hot melt adhesive is placed between each PET layer.

[0005] The preparation process of the wear-resistant modified PET layer is:

[0006] (1) Add titanium dioxide to water, disperse it by ultrasonic, then add 2-5% of the mass of titanium dioxide sodium sulfonate polyester dispersant, heat to 60-70 ° C, stir for 2-5 hours, dry and remove water to obtain dispersant-modified titanium dioxide.

[0007] (2) Add 100 parts by weight of polyethylene terephthalate and 2-8 parts by weight of dispersant-modified titanium dioxide into a twin-screw extruder, with the temperature of each section being 210-270°C and the screw speed being 100-150 r / min, melt-extrude and granulate, and then pass through a molding machine for molding at 10-15 MPa and 250-260°C to obtain a wear-resistant modified PET layer.

[0008] Preferably, the preparation process of the sodium sulfonate polyester dispersant is:

[0009] (1) Add terephthaloyl chloride and 3-hydroxypropionic acid to tetrahydrofuran, stir, then add sodium carbonate aqueous solution dropwise, stir and react at 20-25°C for 3-5 hours, concentrate under reduced pressure, filter, wash with water and dry, then add to thionyl chloride, stir and react at 60-70°C for 4-5 hours, concentrate under reduced pressure and dry to obtain 3,3'-(terephthalate)dipropionyl chloride. The reaction formula is:

[0010]

[0011] (2) Add 3,3'-(terephthalate)dipropionyl chloride, sodium ethylenediamine ethanesulfonate, and an acid binding agent to N,N-dimethylformamide, stir and react at 20-35°C for 12-18 hours, add ethanol to dilute, filter, wash with ethanol, and dry to obtain a sodium sulfonate polyester dispersant. The reaction formula is:

[0012]

[0013] Preferably, the mass of 3-hydroxypropionic acid and sodium carbonate in (1) is 88-97% and 103-115% of the mass of terephthaloyl chloride.

[0014] Preferably, in (2), the mass of sodium ethylenediaminesulfonate and the acid-binding agent are 84-102% and 54-64% of the mass of 3,3'-(terephthalate)dipropionyl chloride.

[0015] Preferably, the acid binding agent is triethylamine or pyridine

[0016] The technical effect of the present invention is that 3,3'-(terephthalate) dipropionyl chloride and sodium ethylenediamine ethanesulfonate are subjected to an amidation polymerization reaction to obtain a novel sodium sulfonate polyester dispersant. The molecular chain of the novel sodium sulfonate polyester dispersant contains a large number of sodium sulfonate groups, which can interact with the surface of titanium dioxide, thereby achieving surface modification and dispersion of the titanium dioxide, and significantly improving the dispersion performance of the titanium dioxide. At the same time, the sodium sulfonate polyester dispersant contains terephthalate structural units similar to PET, so that the modified titanium dioxide has better compatibility with PET polyester and is evenly dispersed in the PET matrix, so that the PET layer exhibits a lower wear value, higher impact strength and tensile strength, and has excellent wear resistance and mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of a three-layer PET erasable whiteboard. DETAILED DESCRIPTION

[0018] To further understand the present invention, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] Sodium ethylenediamine ethanesulfonate was prepared according to the method of the journal "Organic Chemistry", Vol. 29, No. 6, 2009, 904-908, in the document "Synthesis and Characterization of Sodium Ethylenediamine Ethylene Sulfonate".

[0020] Add ethylenediamine to a flask, add 28.5% sodium hydroxide solution by mass, heat to 80°C, add sodium 2-chloroethanesulfonate (molar ratio to ethylenediamine is 1:1), react for 4 hours, separate the layers, take the upper yellow viscous material, purify and dry to obtain sodium ethylenediamine ethanesulfonate. The structural formula is as follows:

[0021]

[0022] Example 1

[0023] (1) To 400 mL of tetrahydrofuran, 20 g of terephthaloyl chloride and 19.4 g of 3-hydroxypropionic acid were added, and after stirring, 130 mL of an aqueous solution containing 23 g of sodium carbonate was added dropwise. The mixture was stirred at 20° C. for 5 h, concentrated under reduced pressure, filtered, washed with water, and dried. The mixture was then added to 220 mL of thionyl chloride, stirred at 60° C. for 4 h, concentrated under reduced pressure, and dried to obtain 3,3'-(terephthalate)dipropionyl chloride.

[0024] (2) Add 5 g of 3,3'-(terephthalate)dipropionyl chloride, 44 g of sodium ethylenediamineethanesulfonate, and 2.7 g of acid-binding agent pyridine to N,N-dimethylformamide, stir and react at 25°C for 18 h, add ethanol to dilute, filter, wash with ethanol, and dry to obtain a sodium sulfonate polyester dispersant.

[0025] (3) Add 40 g of titanium dioxide to 600 mL of water, disperse by ultrasonic, then add 1.1 g of sodium sulfonate polyester dispersant, heat to 65 ° C and stir for 2 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0026] (4) Add 1 kg of polyethylene terephthalate and 20 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 10 MPa and 60°C to obtain a wear-resistant modified PET layer.

[0027] Example 2

[0028] (1) To 300 mL of tetrahydrofuran, 20 g of terephthaloyl chloride and 17.6 g of 3-hydroxypropionic acid were added, and after stirring, 110 mL of an aqueous solution containing 20.6 g of sodium carbonate was added dropwise. The mixture was stirred at 25° C. for 3 h, concentrated under reduced pressure, filtered, washed with water, and dried. The mixture was then added to 220 mL of thionyl chloride, stirred at 70° C. for 5 h, concentrated under reduced pressure, and dried to obtain 3,3'-(terephthalate)dipropionyl chloride.

[0029] (2) Add 5 g of 3,3'-(terephthalate)dipropionyl chloride, 4.2 g of sodium ethylenediamineethanesulfonate, and 2.7 g of acid-binding agent pyridine to N,N-dimethylformamide, stir and react at 35°C for 12 h, add ethanol to dilute, filter, wash with ethanol, and dry to obtain a sodium sulfonate polyester dispersant.

[0030] (3) Add 40 g of titanium dioxide to 600 mL of water, disperse by ultrasonic, then add 0.8 g of sodium sulfonate polyester dispersant, heat to 65 ° C and stir for 2 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0031] (4) Add 1 kg of polyethylene terephthalate and 35 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 100 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 15 MPa and 255°C to obtain a wear-resistant modified PET layer.

[0032] Example 3

[0033] (1) 5 g of 3,3'-(terephthalate)dipropionyl chloride (prepared in Example 1), 5.1 g of sodium ethylenediamine ethanesulfonate, and 3.2 g of triethylamine, an acid-binding agent, were added to N,N-dimethylformamide. The mixture was stirred at 20°C for 18 h, diluted with ethanol, filtered, washed with ethanol, and dried to obtain a sodium sulfonate polyester dispersant.

[0034] (2) Add 40 g of titanium dioxide to 800 mL of water, disperse by ultrasonic, then add 2 g of sodium sulfonate polyester dispersant, heat to 70 ° C and stir for 4 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0035] (3) Add 1 kg of polyethylene terephthalate and 50 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 10 MPa and 260°C to obtain a wear-resistant modified PET layer.

[0036] Example 4

[0037] (1) Add 40 g of titanium dioxide to 700 mL of water and disperse by ultrasonication. Then add 1.7 g of sodium sulfonate polyester dispersant (prepared in Example 1). Heat to 60 ° C. and stir for 5 h. Dry and remove water to obtain dispersant-modified titanium dioxide.

[0038] (2) Add 1 kg of polyethylene terephthalate and 65 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 15 MPa and 260°C to obtain a wear-resistant modified PET layer.

[0039] Example 5

[0040] (1) Add 40 g of titanium dioxide to 70 mL of water, disperse by ultrasonication, then add 1.4 g of sodium sulfonate polyester dispersant (prepared in Example 1), heat to 70 ° C and stir for 3 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0041] (2) Add 1 kg of polyethylene terephthalate and 80 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 100 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 15 MPa and 250°C to obtain a wear-resistant modified PET layer.

[0042] Comparative Example 1

[0043] (1) Add 1 kg of polyethylene terephthalate and 20 g of titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 10 MPa and 60°C to obtain a wear-resistant modified PET layer.

[0044] Comparative Example 2

[0045] (1) Add 40 g of titanium dioxide to 600 mL of water, disperse by ultrasonic, then add 1.1 g of sodium dodecylbenzenesulfonate, heat to 65 ° C and stir for 2 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0046] (2) Add 1 kg of polyethylene terephthalate and 20 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 10 MPa and 60°C to obtain a wear-resistant modified PET layer.

[0047] Comparative Example 3

[0048] (1) 5 g of 3,3'-(terephthalate)dipropionyl chloride (prepared in Example 1), 44 g of N,N'-dimethylethylenediamine, and 2.7 g of pyridine as an acid binder were added to N,N-dimethylformamide, and the mixture was stirred at 25°C for 18 h. Ethanol was added to dilute the mixture, filtered, washed with ethanol, and dried to obtain a polyester dispersant.

[0049] (2) Add 40 g of titanium dioxide to 600 mL of water, disperse by ultrasonic, then add 1.1 g of polyester dispersant, heat to 65 ° C and stir for 2 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0050] (3) Add 1 kg of polyethylene terephthalate and 20 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 10 MPa and 60°C to obtain a wear-resistant modified PET layer.

[0051] Comparative Example 4

[0052] (1) To N,N-dimethylformamide, 5 g of terephthaloyl chloride (prepared in Example 1), 44 g of sodium ethylenediamine ethanesulfonate, and 2.7 g of an acid-binding agent, pyridine, were added and stirred at 25° C. for 18 h. Ethanol was added for dilution, the mixture was filtered, washed with ethanol, and dried to obtain a sodium sulfonate dispersant.

[0053] (2) Add 40 g of titanium dioxide to 600 mL of water, disperse by ultrasonic, then add 1.1 g of sodium sulfonate dispersant, heat to 65 ° C and stir for 2 h, dry and remove water to obtain dispersant-modified titanium dioxide.

[0054] (3) Add 1 kg of polyethylene terephthalate and 20 g of dispersant-modified titanium dioxide into a twin-screw extruder. The temperatures of each section are 210°C, 230°C, 260°C, 270°C, 270°C, and 270°C. The screw speed is 150 r / min. Melt extrusion and granulation are performed. Then, the mixture is passed through a molding machine and molded at 10 MPa and 60°C to obtain a wear-resistant modified PET layer.

[0055] With reference to the method of GB / T 17657-2013, the wear resistance of the wear-resistant modified PET layer was tested, and the abrasion value F was calculated according to the following formula: F = (m1-m2) / R×100, where F is the abrasion value (mg / 100r), m1 is the mass of the specimen before abrasion (mg), m2 is the mass of the specimen after abrasion (mg), and R is the number of abrasion revolutions (r).

[0056] The whiteness value of the wear-resistant modified PET layer was tested by an integrating sphere spectrophotometer using the reflection method at a test temperature of 25°C.

[0057] The impact strength of the wear-resistant modified PET layer was tested according to GB / T 1043.1-2008.

[0058] The tensile strength of the wear-resistant modified PET layer was tested according to GB / T 1040.1-2018 method.

[0059] The test results are shown in Table 1.

[0060] Table 1: Test results

[0061]

[0062] The wear-resistant modified PET layers of Examples 1-5 exhibit low abrasion values ​​(F), high impact strength and tensile strength, and excellent wear resistance and mechanical properties. This is because the sodium sulfonate polyester dispersant's molecular chain contains a large number of sodium sulfonate groups, which can interact with the titanium dioxide surface, thereby modifying and dispersing the titanium dioxide surface and significantly improving its dispersibility. Furthermore, the sodium sulfonate polyester dispersant contains terephthalate structural units similar to those of PET, which improves the compatibility of the modified titanium dioxide with the PET polyester and allows for uniform dispersion in the PET matrix, resulting in excellent wear resistance and mechanical properties for the PET layer.

[0063] The titanium dioxide in Comparative Example 1 has not been surface modified, has poor dispersibility, poor compatibility with PET, is prone to agglomeration, and has a large abrasion value F of the PET layer, and low impact strength and tensile strength.

[0064] In Comparative Example 2, common sodium dodecylbenzene sulfonate was used to modify the surface of titanium dioxide. The resulting PET layer had a larger abrasion value F, and its impact strength and tensile strength were lower than those of the other examples. This may be because sodium dodecylbenzene sulfonate has poor compatibility with PET and cannot improve the compatibility between titanium dioxide and PET.

[0065] In Comparative Example 3, 3,3'-(terephthalate) dipropionyl chloride and N,N'-dimethylethylenediamine were used for polymerization reaction. The obtained polyester dispersant did not contain sulfonic acid groups and could not effectively disperse the surface of titanium dioxide. As a result, the dispersibility and compatibility of titanium dioxide in PET were poor, the abrasion value F of the PET layer was large, and the impact strength and tensile strength were low.

[0066] In Comparative Example 4, a sodium sulfonate dispersant was obtained by polymerization reaction of terephthaloyl chloride and sodium ethylenediamineethanesulfonate, which effectively dispersed the titanium dioxide surface. However, the abrasion value F of the PET layer was large, and the impact strength and tensile strength were lower than those of the other examples. This may be because the sodium sulfonate dispersant does not contain terephthalate structural units and has poor compatibility with PET, making it difficult to effectively improve the compatibility between titanium dioxide and PET.

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A three-layer PET structure erasable whiteboard, characterized in that: The three-layer PET erasable whiteboard consists of a wear-resistant modified PET upper layer, a PET middle layer and a PET lower layer, and EVA hot melt adhesive is placed between each PET layer; The preparation process of the wear-resistant modified PET upper layer is: (1) Add titanium dioxide to water, disperse by ultrasonic, then add sodium sulfonate polyester dispersant, heat to 60-70°C, stir for 2-5h, dry and remove water to obtain dispersant-modified titanium dioxide; (2) adding 100 parts by weight of polyethylene terephthalate and 2-8 parts by weight of dispersant-modified titanium dioxide into a twin-screw extruder, melt-extruded, granulated, and then compression-molded by a molding machine to obtain a wear-resistant modified PET upper layer; The preparation process of the sodium sulfonate polyester dispersant is: (1) Add terephthaloyl chloride and 3-hydroxypropionic acid to tetrahydrofuran, stir, then add dropwise a sodium carbonate aqueous solution, stir and react at 20-25° C. for 3-5 hours, concentrate under reduced pressure, filter, wash with water, and then dry, then add to thionyl chloride, stir and react at 60-70° C. for 4-5 hours, concentrate under reduced pressure, and dry to obtain 3,3'-(terephthalate)dipropionyl chloride; the mass of the 3-hydroxypropionic acid is 88-97% of the mass of the terephthaloyl chloride; the mass of the sodium carbonate is 103-115% of the mass of the terephthaloyl chloride; (2) Adding 3,3'-(terephthalate) dipropionyl chloride, sodium ethylenediamine ethanesulfonate, and an acid binding agent to N,N-dimethylformamide, adding ethanol to dilute after the reaction, filtering, washing with ethanol, and drying to obtain a sodium sulfonate polyester dispersant; the mass of the sodium ethylenediamine ethanesulfonate is 84-102% of the mass of the 3,3'-(terephthalate) dipropionyl chloride; the mass of the acid binding agent is 54-64% of the mass of the 3,3'-(terephthalate) dipropionyl chloride.

2. The three-layer PET structure erasable whiteboard according to claim 1, characterized in that: The mass of the sodium sulfonate polyester dispersant is 2-5% of the mass of titanium dioxide.

3. The three-layer PET structure erasable whiteboard according to claim 1, characterized in that: The temperature of each section of the twin-screw extruder is 210-270° C., and the screw speed is 100-150 r / min; the pressure during compression molding is 10-15 MPa, and the temperature is 250-260° C.

4. The three-layer PET structure erasable whiteboard according to claim 1, characterized in that: The acid binding agent in (2) is triethylamine or pyridine.

5. The three-layer PET structure erasable whiteboard according to claim 1, characterized in that: In the preparation process of the sodium sulfonate polyester dispersant, the reaction in (2) is stirred at 20-35° C. for 12-18 hours.

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