Printing ink cleaning solution, application thereof and treatment method of printing ink on surface of polymer

Abstract

The invention discloses an ink cleaning solution. The printing ink cleaning solution comprises the following components in parts by weight: 9-41 parts of polyvinyl alcohol, 9-21 parts of an oxidizing agent and 50-80 parts of a polar solvent, the number-average molecular weight of the polyvinyl alcohol is 2.5-3.5 thousand; the oxidizing agent is a mixture of pypocholoride and percarbonate. Furthermore, the invention discloses a method for treating the printing ink on the surface of the polymer by adopting the printing ink cleaning solution. The ink cleaning solution provided by the invention has excellent removal and cleaning effects on oil-based ink on the surface of a polymer, and the cleaned regenerated polymer has better whiteness.

Description

Technical Field

[0001] The invention belongs to the technical field of recycled plastics, and more specifically relates to an ink cleaning liquid and an application thereof and a method for treating ink on a polymer surface. Background Art

[0002] After printing and drying, a highly adhesive ink film will form on the surface of the plastic packaging film (such as PP, PE). This ink layer is mainly polyurethane and / or acrylic oil-based inks. Such oil-based inks have strong adhesion to the plastic packaging film and are insoluble in water and cannot be dissolved in ordinary water-soluble cleaning agents. Therefore, they are more difficult to remove than conventional water-soluble inks. If the oil-based ink layer on the surface of the plastic packaging film is not removed and the packaging film is directly recycled and granulated, the appearance of the prepared particles will be seriously affected, and only black recycled products can be produced.

[0003] At present, the method of removing oily ink is to soak the plastic packaging film in an organic solvent, dissolve the oily ink layer again and clean it, dry the completely cleaned film and then recycle it. The advantage of this method is that the oily ink is thoroughly cleaned, the regenerated particles have a good appearance, and high-quality products can be produced. However, using organic solvents to dissolve the oily ink layer has the safety risks of volatile toxicity, flammability and explosion; in addition, after using organic solvents to remove the oily ink, a large amount of organic solvent will remain on the surface of the film, and the organic solvent is insoluble in water, so it is difficult to completely remove it with clean water. It is also necessary to use a detergent to clean it, and then rinse it with clean water. The process is cumbersome and consumes a lot of water. Therefore, how to remove the ink as environmentally friendly and efficiently as possible and prepare recycled plastics with better appearance has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] In view of the above existing technical problems, the primary purpose of the present invention is to provide an ink cleaning liquid that can remove ink in an environmentally friendly and efficient manner, has an excellent removal and cleaning effect on oily ink on the surface of polymers, and the regenerated polymer after cleaning has good whiteness.

[0005] The second object of the present invention is to provide a method for preparing an ink cleaning solution.

[0006] The third object of the present invention is to provide use of an ink cleaning liquid in removing ink from a polymer surface.

[0007] A fourth object of the present invention is to provide a method for treating ink on a polymer surface.

[0008] A fifth object of the present invention is to provide a recycled polymer.

[0009] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0010] The present invention claims protection for an ink cleaning liquid, which comprises, by weight: 9-41 parts of polyvinyl alcohol, 9-21 parts of an oxidant, and 50-80 parts of a polar solvent;

[0011] The number average molecular weight of the polyvinyl alcohol is 25,000-35,000;

[0012] The oxidant is a mixture of hypochlorite and percarbonate.

[0013] Polyvinyl alcohol is non-toxic and harmless, and is a polar substance. It has good compatibility with polar inks such as polyurethane or acrylic, but is incompatible with non-polar polyethylene. It is easy to remove polar inks such as polyurethane or acrylic from the polyethylene surface. The inventor further found through research that when the amount of polyvinyl alcohol in the ink cleaning solution is low, on the one hand, the surface of the polymer film cannot be fully infiltrated; on the other hand, its compatibility with polar inks such as polyurethane or acrylic deteriorates, thereby making the cleaning and removal effect worse. When the amount of polyvinyl alcohol is high, it is easy to precipitate in polar solvents. Furthermore, the inventor found through research that when the molecular weight of polyvinyl alcohol is within the above-mentioned specific range, the viscosity of polyvinyl alcohol is low, which is more conducive to the dissolution of oil-based inks.

[0014] Furthermore, the present invention adopts a mixture of hypochlorite and percarbonate as an oxidant. On the one hand, the oxidizing effect of this specific combination of oxidants can have a good oxidative decomposition effect on the toner in the oil-based ink, thereby achieving the effect of color removal and bleaching; in addition, the oxidative decomposition of the oil-based ink by this specific combination of oxidants can also accelerate the dissolution of the oil-based ink in polyvinyl alcohol, thereby greatly improving the removal effect of the oil-based ink.

[0015] The present invention uses a combination of polyvinyl alcohol with a specific molecular weight and an oxidant of a specific combination, which can play a good synergistic role and has an excellent cleaning and removal effect on the oily ink on the polymer surface. In addition, the polyvinyl alcohol and the oxidant are both soluble in water and can be easily cleaned by water in the subsequent rinsing process, thereby avoiding residues and the use of subsequent cleaning agents, and reducing water consumption and processing costs.

[0016] Specifically, the amount of the polyvinyl alcohol can be 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, 22 parts, 24 parts, 26 parts, 28 parts, 30 parts, 32 parts, 34 parts, 36 parts, 38 parts, etc., or an interval range formed by any of the above values, such as 22-30 parts, 26-34 parts, etc., and the present invention is not limited thereto. The amount of the oxidant can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, 19 parts, 20 parts, etc., or an interval range formed by any of the above values, such as 7-11 parts, 9-15 parts, etc., and the present invention is not limited thereto. The amount of the polar solvent may be 53 parts, 57 parts, 59 parts, 61 parts, 63 parts, 65 parts, 67 parts, 69 parts, 71 parts, 73 parts, 75 parts, 77 parts, 79 parts, etc., or an interval range formed by any of the above values, such as 57-61 parts, 59-67 parts, etc., but the present invention is not limited thereto.

[0017] Specifically, the ink cleaning solution includes, by weight: 20-40 parts of polyvinyl alcohol, 10-20 parts of oxidant, and 50-70 parts of polar solvent.

[0018] Specifically, the number average molecular weight of the polyvinyl alcohol can be 26,000, 27,000, 28,000, 29,000, 30,000, 31,000, 32,000, 33,000, 34,000, etc., or an interval range formed by any of the above values, such as 27,000-31,000, 29,000-33,000, etc., and the present invention is not limited thereto. Specifically, the test standard or method for the number average molecular weight of the polyvinyl alcohol: viscosity test.

[0019] Preferably, the hypochlorite is one or more of sodium hypochlorite and calcium hypochlorite; and / or the percarbonate is sodium percarbonate.

[0020] Preferably, the mass ratio of the hypochlorite to the percarbonate is 1:(0.5-3); further preferably, the mass ratio of the hypochlorite to the percarbonate is 1:(0.8-2); more preferably, the mass ratio of the hypochlorite to the percarbonate is 1:(1-1.5).

[0021] Preferably, the polar solvent is water.

[0022] Furthermore, the present invention seeks to protect the use of the above-mentioned ink cleaning solution in removing ink from the surface of a polymer.

[0023] Specifically, the polymer surface ink is an oily ink; more specifically, the oily ink is an oily ink such as polyurethane and / or acrylic. The ink cleaning liquid provided by the present invention has an excellent cleaning and removal effect on oily inks such as polyurethane and / or acrylic.

[0024] Furthermore, the present invention claims protection for a method for preparing an ink cleaning liquid, which is obtained by uniformly mixing polyvinyl alcohol, an oxidant and a polar solvent.

[0025] Preferably, the temperature for uniform mixing is 80-100°C.

[0026] Furthermore, the present invention claims a method for treating ink on a polymer surface, comprising the following steps:

[0027] S1. Mix the polymer with ink and the ink cleaning solution and stir at ≥90°C;

[0028] S2. The stirred material is filtered and rinsed to obtain a regenerated polymer.

[0029] In the present invention, when the polymer with ink and the ink cleaning liquid are mixed, the temperature of the mixed elution needs to be controlled to be ≥ 90°C. At this temperature, the ink cleaning liquid has better solubility for the ink, and thus has a better elution effect. The stirred material is then filtered. During the friction process of the filter press, the oily ink is removed from the surface of the material and removed together with the ink cleaning liquid. The ink cleaning liquid remaining on the surface of the polymer is then rinsed to remove it, and the regenerated polymer can be obtained.

[0030] Preferably, in step S1, the polymer is a polymer film, and its size is 10mm*10mm-100mm*100mm. Further preferably, its size is 10mm*10mm-50mm*50mm. The ink cleaning liquid provided by the present invention is more suitable for polymer films. Under the above preferred size, the ink cleaning liquid has a better cleaning and removal effect on the oily ink on the surface of the polymer film. More specifically, the length and width of the polymer film can be 10mm, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, 80mm, 90mm, 100mm, etc., respectively, or the interval range formed by any combination of the above length and width values, and the present invention is not limited thereto.

[0031] More specifically, the polymer film can be cut into the above-mentioned sizes by cutting. Compared with breaking the polymer film into appropriate sizes, the cutting method can avoid the problem of softening and curling of the polymer film due to friction heat during the breaking process, thereby covering the ink and avoiding affecting the cleaning efficiency of the subsequent ink cleaning solution. If the size of the polymer film is too small, it will affect the subsequent dehydration step, and the polymer film is easy to leak from the dehydrator.

[0032] Preferably, in step S1, the mass ratio of the polymer with ink to the ink cleaning solution is 100:(20-60). Further preferably, the mass ratio of the polymer with ink to the ink cleaning solution is 100:(30-50).

[0033] Preferably, in step S1, the stirring speed is ≥500 rpm, and the stirring time is 30-60 min. More specifically, the stirring speed is 800-1000 rpm.

[0034] Preferably, in step S1, stirring is performed at 90-100°C.

[0035] Preferably, in step S2, the screw compression ratio of the filter pressing is 8-10, the rotation speed is 200-300 rpm, and the filter pressing is ≥3 times.

[0036] Preferably, in step S2, water is used for rinsing. More specifically, the mass ratio of material to water is 1:(3-10), the number of washing times is ≥2 times, and the washing time is ≥5 minutes.

[0037] Furthermore, the present invention claims a recycled polymer obtained by the above-mentioned treatment method. The recycled polymer prepared by the present invention can be subsequently used in the preparation of plastic particle packaging materials and chemical raw material packaging materials, such as plastic particle packaging bags, fertilizer packaging bags, etc.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention uses a combination of polyvinyl alcohol with a specific molecular weight and an oxidant of a specific combination, which can play a good synergistic role and has an excellent cleaning and removal effect on the oily ink on the surface of the polymer. In addition, the polyvinyl alcohol and the oxidant are both soluble in water and can be easily cleaned by water in the subsequent rinsing process, which greatly avoids the use of residues and subsequent cleaning agents, reduces water consumption, processing costs and improves processing efficiency. The present invention avoids the use of organic solvents and can remove the oily ink on the surface of the polymer in an environmentally friendly and efficient manner. DETAILED DESCRIPTION

[0040] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0041] The raw materials of the embodiments and comparative examples are as follows:

[0042] Waste plastic film 1, polyethylene film material for printing ink, packaging bags for nylon particles, and the ink is acrylic oil-based ink.

[0043] Waste plastic film 2, polyethylene film material for printing ink, packaging bags for fertilizers, the ink is polyurethane oil-based ink.

[0044] Polyvinyl alcohol 1, molecular weight 25,000, PVOH-0588, Chongqing Chuanwei Chemical Co., Ltd., China.

[0045] Polyvinyl alcohol 2, molecular weight 30,000, PVOH-0599, Changchun Chemical Industry, Taiwan, China.

[0046] Polyvinyl alcohol 3, molecular weight 35,000, PVOH-103, Japan Cole Li Co., Ltd.

[0047] Polyvinyl alcohol 4, molecular weight 120,000, PVOH-1788, Chongqing Chuanwei Chemical Co., Ltd., China.

[0048] Oxidant 1, sodium hypochlorite, commercially available.

[0049] Oxidant 2, sodium percarbonate, commercially available.

[0050] Oxidant 3, hydrogen peroxide, commercially available.

[0051] Unless otherwise specified, all parallel examples and comparative examples are the same commercially available products.

[0052] Example 1

[0053] (1) The waste plastic film 1 is cut horizontally and vertically on a cutting machine to cut into film fragments with a size of 10*10 mm.

[0054] (2) 100 parts of film fragments were placed in a high-speed stirring pot, 50 parts of ink cleaning solution were added, high-temperature steam was introduced to make the mixing temperature reach 90°C, and the mixture was stirred at a speed of 1000 rpm for 60 minutes.

[0055] In terms of weight, the ink cleaning liquid includes: 30 parts of polyvinyl alcohol 1, 10 parts of oxidant, and 60 parts of water; the oxidant includes oxidant 1 and oxidant 2 in a mass ratio of 1:1; the preparation method of the ink cleaning liquid is: add polyvinyl alcohol 1 to water, stir continuously at 90°C until completely melted, and then add oxidant 1 and oxidant 2 and stir until completely melted.

[0056] (3) The material stirred in step (2) was added into a screw filter press for extrusion, with a screw compression ratio of 10, a rotation speed of 300 rpm, and filter pressing for 3 times.

[0057] (4) The material extruded in step (3) is placed in clean water for rinsing, the ratio of material to clean water is 1:5, and the film is washed twice, the washing time is 10 minutes, and the surface moisture of the film fragments is removed by a horizontal dehydrator to obtain a clean recycled plastic film.

[0058] Example 2

[0059] The difference between Example 2 and Example 1 is that in step (2), polyvinyl alcohol 2 is used.

[0060] Example 3

[0061] The difference between Example 3 and Example 1 is that in step (2), polyvinyl alcohol 3 is used.

[0062] Example 4

[0063] The difference between Example 4 and Example 1 is that in step (2), the ink cleaning solution comprises, by weight: 20 parts of polyvinyl alcohol 1, 10 parts of oxidant, and 70 parts of water.

[0064] Example 5

[0065] The difference between Example 5 and Example 1 is that in step (2), the ink cleaning solution comprises, by weight: 40 parts of polyvinyl alcohol 1, 10 parts of oxidant, and 50 parts of water.

[0066] Example 6

[0067] The difference between Example 6 and Example 1 is that in step (1), the film is cut into pieces with a size of 50*50 mm.

[0068] Example 7

[0069] The difference between Example 7 and Example 1 is that in step (1), the film is cut into pieces with a size of 100*100 mm.

[0070] Example 8

[0071] The difference between Example 8 and Example 1 is that in step (2), the ink cleaning solution comprises, by weight: 10 parts of polyvinyl alcohol 1, 10 parts of oxidant, and 80 parts of water.

[0072] Example 9

[0073] The difference between Example 9 and Example 1 is that in step (2), the ink cleaning solution comprises, by weight: 20 parts of polyvinyl alcohol 1, 20 parts of oxidant, and 60 parts of water.

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 1 is that in step (2), polyvinyl alcohol 4 is used.

[0076] Comparative Example 2

[0077] The difference between Comparative Example 2 and Example 1 is that in step (2), high-temperature steam is introduced so that the mixing temperature is 80°C.

[0078] Comparative Example 3

[0079] The difference between Comparative Example 3 and Example 1 is that in step (2), the ink cleaning solution does not contain polyvinyl alcohol.

[0080] Comparative Example 4

[0081] The difference between Comparative Example 4 and Example 1 is that in step (2), the ink cleaning solution does not contain an oxidant.

[0082] Comparative Example 5

[0083] The difference between Comparative Example 5 and Example 1 is that in step (2), the ink cleaning solution does not contain polyvinyl alcohol and oxidant.

[0084] Comparative Example 6

[0085] The difference between Comparative Example 6 and Example 1 is that in step (2), oxidant 1 is used to replace the combination of oxidant 1 and oxidant 2.

[0086] Comparative Example 7

[0087] The difference between Comparative Example 7 and Example 1 is that in step (2), oxidant 2 is used to replace the combination of oxidant 1 and oxidant 2.

[0088] Comparative Example 8

[0089] The difference between Comparative Example 8 and Example 1 is that in step (2), the oxidant includes oxidant 1 and oxidant 3 in a mass ratio of 1:1.

[0090] Test Case

[0091] The recycled plastic film materials obtained by the treatment in the above-mentioned embodiments and comparative examples were tested according to the following test methods.

[0092] (1) Ink removal rate: Take 200 g of the washed recycled plastic film, manually select the recycled plastic film containing residual ink, and weigh W. Ink removal rate = (1-W / 200) × 100%.

[0093] (2) Whiteness L value: The cleaned recycled plastic film is extruded into granules at 180°C using a single screw extruder, and then a standard color plate is injection molded at 200°C and placed in a color testing instrument for testing.

[0094] Table 1 shows the test results of various embodiments and comparative examples.

[0095] Table 1

[0096]

[0097]

[0098] As shown in Table 1 above, the ink cleaning solution and the method for treating the ink on the polymer surface provided by the present invention have excellent cleaning and removal effects on the oily ink on the polymer surface, and the regenerated polymer after cleaning has good whiteness and appearance. More specifically, the ink removal rate is ≥92.4%; the L value is ≥83.

[0099] It can be seen from Example 1, Example 4, Example 5 and Example 8 that when the mass concentration of polyvinyl alcohol is 20-40%, it has a better ink removal rate and L value.

[0100] It can be seen from Example 1, Example 6 and Example 7 that when the size of the polymer is between 10*10mm and 50*50mm, the ink cleaning liquid has a better cleaning and removal effect on the oily ink on the surface of the polymer film, and the L value is higher.

[0101] It can be seen from Example 1 and Comparative Example 1 that when the molecular weight of polyvinyl alcohol is high, the viscosity of polyvinyl alcohol is high, which in turn affects its solubility in oil-based ink, resulting in a decrease in ink removal rate and L value.

[0102] It can be seen from Example 1 and Comparative Example 2 that when the temperature of the mixed elution of the polymer with ink and the ink cleaning solution is ≥90°C, the ink cleaning solution has better solubility for the ink and thus has a better elution effect.

[0103] It can be seen from Example 1, Comparative Example 3, Comparative Example 4 and Comparative Example 5 that the technical effect of the present invention can be achieved only when polyvinyl alcohol is combined with a specific oxidant.

[0104] It can be seen from Example 1, Comparative Example 6, Comparative Example 7 and Comparative Example 8 that when a mixture of hypochlorite and percarbonate is used as the oxidant combination of the present invention, a higher ink removal rate and a higher L value can be achieved.

[0105] The foregoing examples are merely illustrative and are used to explain some features of the method of the present invention. The appended claims are intended to require the widest possible range that can be imagined, and the embodiments presented herein are demonstrated by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims are not limited by the selection of examples that illustrate the features of the present invention. Some numerical ranges used in the claims also include sub-ranges therein, and changes in these ranges should also be interpreted as being covered by the appended claims where possible.

Claims

1. An ink cleaning liquid, characterized in that: Calculated by weight, it comprises: 9-41 parts of polyvinyl alcohol, 9-21 parts of oxidant, and 50-80 parts of polar solvent; The number average molecular weight of the polyvinyl alcohol is 25,000-35,000; The oxidant is a mixture of hypochlorite and percarbonate.

2. The ink cleaning liquid according to claim 1, characterized in that: The hypochlorite is one or more of sodium hypochlorite and calcium hypochlorite; and / or The percarbonate is sodium percarbonate.

3. The ink cleaning liquid according to claim 1, characterized in that: The mass ratio of the hypochlorite to the percarbonate is 1:(1-3).

4. The ink cleaning liquid according to claim 1, characterized in that: The polar solvent is water.

5. The method for preparing the ink cleaning solution according to any one of claims 1 to 4, characterized in that: The polyvinyl alcohol, oxidant and polar solvent are mixed evenly to obtain the product.

6. Use of the ink cleaning solution according to any one of claims 1 to 4 in removing ink from the surface of a polymer.

7. A method for treating ink on a polymer surface, characterized in that: The following steps are involved: S1. The polymer with ink and the ink cleaning solution according to any one of claims 1-4 are mixed and stirred at ≥90°C; S2. The stirred material is filtered and rinsed to obtain a regenerated polymer.

8. The processing method according to claim 1, characterized in that: In the step S1, the polymer is a polymer film, and its size is 10mm*10mm-100mm*100mm.

9. The processing method according to claim 1, characterized in that: In the step S1, the mass ratio of the polymer with ink to the ink cleaning solution is 100:(20-60).

10. A recycled polymer, characterized in that The product is prepared by treating with the treatment method described in any one of claims 7 to 9.

Images