Method for preparing polypropylene coating material through non-chemical degradation

Abstract

The invention discloses a method for preparing a polypropylene coating material through non-chemical degradation, which comprises the following steps: firstly, uniformly mixing polypropylene powder B and a compound additive to obtain a mixture, then adding the mixture, the polypropylene powder A and polyethylene into an extruder for melting, mixing, extruding, cooling, blow-drying, pelletizing, screening, blending and drying to obtain coating-grade polypropylene; feeding the polypropylene powder A, the mixture and polyethylene according to the mass ratio of (13-16): (2-4): (2-5); the addition amount of the compound additive is 1000 to 2300 ppm. Compared with a traditional degradation method, the method has the advantages that no chemical degradation agent exists, the production temperature control range is wide, and compared with a coating material prepared through a chemical degradation method, the melt index is stable, and the glossiness is high (gt; 130%), the haze is low (lt); 3.5%) and bonding strength (gt; the invention provides a change for the production and material using mode (PP / PE mixing and film coating) of the existing polypropylene coating material, and solves a series of problems of degradation agent residue, non-uniform PP / PE mixing, large fluctuation of production working conditions, non-uniform film coating and the like.

Description

Technical Field

[0001] The invention relates to the technical field of polymer production, in particular to a method for preparing a polypropylene coating material without chemical degradation. Background Art

[0002] Coating grade polypropylene (PP) is a resin used to coat the surface of plastic woven bags, non-woven fabrics and other objects. Due to its good fluidity, film-forming properties, adhesion, corrosion resistance, waterproof and moisture-proof properties and stable processing performance, it is widely used in woven bags, BOPP coating, automotive decoration, medical protection and food packaging.

[0003] At present, the main methods for producing coating-grade polypropylene resins are: hydrogen adjustment method and chemical degradation method. The hydrogen adjustment method is a method of regulating the melt index of the product by controlling the amount of hydrogen added. The coating materials produced by the hydrogen adjustment method are mainly foreign copolymer-grade polypropylene, such as F3990 of Japan Zinc Co., Ltd., PP9412 of Singapore, and coating special materials of Samsung in South Korea. Its products have the advantages of strong process adaptability and excellent coating film composite performance. However, imported materials have the problems of high price and tight supply.

[0004] The chemical degradation method usually involves adding a peroxide degradation agent to the polymer granulation unit. The degradation agent is decomposed by heat in the extruder to produce free radicals that attack the tertiary carbon atoms on the polypropylene molecular chain and attack and take away the hydrogen atoms on it, causing the polypropylene molecular chain to break, thereby obtaining a resin with a low molecular weight and a high melt index.

[0005] At present, the new catalyst technology used in the production of coating-grade polypropylene in China is not yet mature, and there is no special material for copolymerized polypropylene coating, so the production of coating-grade polypropylene is still mainly based on chemical degradation. However, the chemical degradation method has problems such as strict temperature control, small temperature difference range, residual or uneven distribution of degradation agent, large fluctuation of product melt index, poor stability of upstream and downstream processing, yellowish coating resin particles, strong odor, and poor transparency and gloss of the coating film.

[0006] During downstream coating, the polypropylene coating produced by chemical degradation usually needs to be mixed with low-density polyethylene (PE), that is, PP / PE mixed coating. The PE content is usually 10-25%. There are problems caused by a series of raw materials and mixing materials, such as unstable coating quality, large process fluctuations, low adhesion between the film and the cloth base, strong product odor and poor gloss.

[0007] Therefore, there is an urgent need to develop a polypropylene coating material and production method that is simple, easy to produce and regulate, has excellent product performance and stable quality, and does not require the addition of PE mixed coatings downstream.

[0008] The information disclosed in the background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0009] The purpose of the present invention is to provide a method for preparing a polypropylene coating material by non-chemical degradation in order to solve the above technical problems. The polypropylene coating material obtained by the method can be coated independently without adding PE mixed material for coating. The obtained polypropylene coating material has the characteristics of good fluidity, strong adhesion, excellent mechanical properties and high transparency.

[0010] The object of the present invention is achieved through the following technical solution, and the specific steps are as follows:

[0011] The following steps are involved:

[0012] (1) The polypropylene powder B and the compound additive are mixed to obtain a mixture, and the mixture, the polypropylene powder A, and the polyethylene are weighed by a loss-in-weight scale and simultaneously added to a twin-screw extruder for melting, mixing, and extrusion;

[0013] (2) drawing the sample extruded in step (1) and cooling and crystallizing it;

[0014] (3) drying, pelletizing and screening the cooled material strips in step (2);

[0015] (4) blending and drying the qualified products in step (3) to obtain a polypropylene coating material;

[0016] Polypropylene powder A, mixed material and polyethylene are mixed in a mass ratio of 7-14:1-3:1-5;

[0017] The amount of compound additive added is 1000-2300ppm.

[0018] Preferably, the polypropylene powder A, the mixed material and the polyethylene are mixed in a mass ratio of 13:2:5.

[0019] Preferably, the polypropylene powder A, the mixed material and the polyethylene are mixed in a mass ratio of 13:3:4.

[0020] Preferably, the melt index of polypropylene powder A is 60 g / 10 min; and the melt index of polypropylene powder B is 3 g / 10 min.

[0021] Preferably, the product grade of polypropylene powder A is any one of M600E, H9018, M065E, M60T, PPR-M55-S, PPH-M600N, and S980 powder;

[0022] The product brand of polypropylene powder B is any one of L5E89, 1102K, PPH-T035, S003G, and T30S powder.

[0023] Preferably, the polyethylene is low-density polyethylene; the melt index of the polyethylene is 5 to 10 g / 10 min; and the product grade of the polyethylene is any one of 1C7A, 1C10A, 950, LB7500, LD251, and 2426H.

[0024] Preferably, the compound additive consists of 1 part by weight of a primary antioxidant Irganox 1010, 2 parts by weight of a secondary antioxidant Irgafos 168, 0.5 parts by weight of Utranox 622 and 1 part by weight of calcium stearate.

[0025] Preferably, the temperature of the desalted water used is 25-30°C.

[0026] Preferably, the mixing method used for the cyclic mixing is O-type pneumatic conveying to drive the sample to circulate in the homogenization bin, the mixing time is 3 to 5 hours, and the drying temperature is 70 to 90°C.

[0027] Compared with the prior art and existing polypropylene coating materials, the beneficial effects of the present invention mainly include:

[0028] (1) The present invention provides a method for preparing a polypropylene coating material by non-chemical degradation, which develops a new coating material production method (i.e., non-chemical degradation method) that is different from the traditional method (chemical degradation method), and provides a new idea and method for the production of polypropylene coating materials by melt extrusion, and thus has important significance in the field of polypropylene coating materials.

[0029] (2) The polypropylene coating prepared by non-chemical degradation can replace the PP / PE mixed coating material method, that is, independent coating material, which provides a change in the material method of polypropylene coating and can solve the problems of mixing and coating. The peel strength of the coating product can reach more than 4N, the melt index can be >30g / 10min, the glossiness can be >130%, the haze can be as low as less than 2%, and the yellow index is negative, which means that the yellowing problem of the obtained material can be effectively reduced. The comprehensive performance is better than the polypropylene coating and PP / PE mixed material produced by traditional chemical degradation method.

[0030] (3) The unique advantages of the method of preparing polypropylene coating materials by non-chemical degradation are: first, there is no chemical degradation agent, the upstream and downstream processing temperature is wide, the production process control is simple, and it is conducive to continuous and stable production operation; second, it avoids the uneven distribution and residue of chemical degradation agents in traditional methods, and the large fluctuation of product melt index and unstable production conditions caused by inconsistent resin degradation degree;

[0031] (4) The melting point and crystallization point of the polypropylene coating prepared by this method are lower than those prepared by the chemical degradation method. The processing temperature can be lowered (about 20°C) during coating, thus saving electricity and reducing product energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention provides the appearance pictures of the polypropylene coating prepared in Example 6 and Comparative Example 1. Among them, a is Example 6; b is Comparative Example 1.

[0033] Figure 2 Provided are mechanical property test diagrams of polypropylene coating materials prepared in Example 6, Comparative Example 1 and Comparative Example 2 of the present invention;

[0034] Figure 3 The present invention provides the melting point and crystallization temperature curves of the polypropylene coating prepared in Example 6, Comparative Example 1 and Comparative Example 2. Wherein, Figure a): heating curve; Figure b): cooling curve. DETAILED DESCRIPTION

[0035] The technical solution provided by the present invention is explained and illustrated in detail below in conjunction with specific embodiments and drawings.

[0036] Example

[0037] Unless otherwise specified in the following examples, the detection methods used are all existing methods, and the materials used are all commercially available products.

[0038] The compound additive used in the following examples consists of 1 part by weight of a primary antioxidant Irganox 1010, 2 parts by weight of a secondary antioxidant Irgafos 168, 0.5 parts by weight of Utranox 622 and 1 part by weight of calcium stearate.

[0039] Example 1 Preparation of polypropylene coating material

[0040] (1) adding polypropylene powder B and compound additives into a high-speed mixer at a mass ratio of 99.1:0.9, and mixing at a speed of 2000 rpm for 3 minutes to obtain a uniform mixture of polypropylene B and additives;

[0041] (2) The mixed sample is transported to the storage tank of loss-in-weight scale 2, and the polypropylene powder A is transported to the storage tank of loss-in-weight scale 1 through the ground feeding station. The feeding mass ratio of loss-in-weight scale 1 and loss-in-weight scale 2 is set to 4:1. The raw materials enter the twin-screw extruder through the same feeding funnel for melting, mixing and extrusion;

[0042] (3) The extruded material strips are cooled with desalted water (25-30°C) and blown dry; finally, pelletized, screened, transported to a mixing bin for cyclic blending for 3 hours, and dried (70°C) to obtain coating-grade polypropylene.

[0043] The melting index of the polypropylene powder A used is 60 g / 10 min, and the product brand of the polypropylene powder A is M065E; the melting index of the polypropylene powder B is 3 g / 10 min, and the product brand of the polypropylene powder B is L5E89.

[0044] The polypropylene coating obtained by the method provided by the present invention has a melt index reduced by about 25g / 10min, a yellow index reduced to <0, a melting point and a crystallization temperature reduced by about 5°C, and a peel strength increased by nearly 3N compared with Comparative Example 1. The comparison results are specifically shown in Table 2.

[0045] Example 2 Preparation of polypropylene coating material

[0046] (1) adding polypropylene powder B and compound additives into a high-speed mixer at a mass ratio of 98.2:1.8, and mixing at a speed of 2000 rpm for 3 minutes to obtain a uniform mixture of polypropylene B and compound additives;

[0047] (2) The mixed material is transported to the storage tank of loss-in-weight scale 2, and at the same time, polypropylene powder A and polyethylene are fed through the ground feeding station and transported to the storage tanks of loss-in-weight scale 1 and loss-in-weight scale 3; the mass ratio of the materials discharged from loss-in-weight scale 1 (polypropylene powder A), loss-in-weight scale 2 (mixed material) and loss-in-weight scale 3 (polyethylene) is set to 8:1:1, and the raw materials enter the twin-screw extruder through the same feeding funnel for melting, mixing and extrusion;

[0048] (3) The extruded material strips are cooled with desalted water (25-30°C) and blown dry; finally, pelletized, screened, transported to a mixing bin for cyclic blending for 5 hours, and dried (90°C) to obtain coating-grade polypropylene.

[0049] The melting index of the polypropylene powder A used is 60g / 10min, and the product brand of the polypropylene powder A is M065E; the melting index of the polypropylene powder B is 3g / 10min, and the product brand of the polypropylene powder B is L5E89; the melting index of the polyethylene is 7g / 10min, and the product brand of the polyethylene is 1C7A.

[0050] Compared with Comparative Example 2 and Example 1, with the decrease of polypropylene B content and the increase of polyethylene content, the peel strength of the coating material is significantly improved (>3N), the melt index is slightly increased (>30g / 10min), and the tensile strength is slightly reduced, but they are all higher than the chemical degradation coating grade PP / PE mixed coating material, the highest melting point and crystallization temperature are about 6°C lower than the PP / PE mixed coating material, and the yellow index is still <0.

[0051] Example 3 Preparation of polypropylene coating material

[0052] The difference from Example 2 is that polypropylene powder B and compound additives are added to the high speed mixer at a mass ratio of 98.8:1.2; the feeding ratio of loss-in-weight scale 1, loss-in-weight scale 2 and loss-in-weight scale 3 is set to 14:3:3 to obtain coating-grade polypropylene.

[0053] Compared with Example 2, the peel strength of the product obtained in Example 3 is increased to 3.7N, the melt index, tensile strength, melting point and crystallization temperature are not much different, and the yellow index is increased. Therefore, the content of polypropylene A is reduced, the content of polypropylene B and polyethylene is increased, the adhesion of the coating is enhanced, and the transparency and glossiness tend to decrease.

[0054] Example 4 Preparation of polypropylene coating material

[0055] The difference from Example 2 is that the material feeding ratio of loss-in-weight scale 1, loss-in-weight scale 2 and loss-in-weight scale 3 is set to 7:1:2, and coating-grade polypropylene is obtained.

[0056] Compared with the product obtained in Example 3, the content of polypropylene B is reduced, the content of polyethylene is increased, there is no significant difference in the fluidity, peel strength, tensile strength, melting point and crystallization temperature of the coating material, and the yellowness index is increased to -0.2.

[0057] Example 5 Preparation of polypropylene coating material

[0058] The difference from Example 2 is that polypropylene powder B and compound additives are added to the high speed mixer at a mass ratio of 98.8:1.2; the feeding ratio of loss-in-weight scale 1, loss-in-weight scale 2 and loss-in-weight scale 3 is set to 13:3:4 to obtain coating-grade polypropylene.

[0059] Compared with Example 4, the content of polypropylene A is reduced, the content of polypropylene B is increased, the melt index and yellow index of the coating are reduced to 25.3 g / 10 min and -1.3 respectively, while the peel strength is increased to 4.2 N, and the tensile strength, melting point and crystallization temperature have no obvious changes.

[0060] Example 6 Preparation of polypropylene coating

[0061] The difference from Example 2 is that the material feeding ratio of loss-in-weight scale 1, loss-in-weight scale 2 and loss-in-weight scale 3 is set to 13:2:5, and coating-grade polypropylene is obtained.

[0062] Compared with Example 2 and Example 4, as the content of polypropylene A decreases and the polyethylene content increases from 10% to 25%, the peel strength of the polypropylene coating prepared by the non-chemical degradation method shows an increasing trend, the yellow index is <0, and the melt index remains in the range of -29.9-32.1g / 10min.

[0063] Example 7 Preparation of polypropylene coating

[0064] The difference from Example 6 is that the polypropylene powder B and the compound additive are added into the high speed mixer at a mass ratio of 99:1.

[0065] Compared with Example 6, when the content of the compounding agent additive is reduced to 1000 ppm, the yellowness index of the coating material increases significantly and is >0.

[0066] Example 8 Preparation of polypropylene coating

[0067] The difference from Example 6 is that the polypropylene powder B and the compound additive are added into the high speed mixer at a mass ratio of 98.5:1.5.

[0068] Compared with Example 7, when the content of the compounding agent additive is increased to 1500 ppm, the yellowness index of the coating material is reduced, but still >0.

[0069] Example 9 Preparation of polypropylene coating

[0070] The difference from Example 6 is that the polypropylene powder B and the compound additive are added into the high speed mixer at a mass ratio of 97.3:2.3.

[0071] Compared with Examples 6 to 8, as the content of the compounding agent additive increases, the yellowness index of the coating material shows a downward trend. When the content of the compounding agent is ≥1800ppm, the yellowness index is <0.

[0072] Comparative Example 1

[0073] The polypropylene coating material is prepared by the traditional chemical degradation method, which is the mainstream in the domestic market. The specific method process can refer to the preparation method disclosed in Example 1 of Chinese invention patent CN116554739B.

[0074] Comparative Example 2

[0075] The product obtained in Comparative Example 1 was mixed with PE at a mass ratio of 75:25 to obtain a PP / PE coating material.

[0076] Comparative Example 2 The preparation method of Example 6 requires mixing the obtained polypropylene coating material with PE, which has a series of problems such as uneven local mixing, unstable melt index between batches of polypropylene coating material produced by degradation method, residual chemical degradation agent, uneven coating film and large fluctuation of working conditions. Therefore, the performance stability of the PP / PE coating material obtained by Comparative Example 2 cannot be guaranteed. However, since Example 6 of the present invention does not need to mix the materials again, and the processing depth and uniformity in the preparation stage are more guaranteed, the obtained product can achieve independent coating and stable quality. Table 1 shows the proportion of components for preparing polypropylene coating material.

[0077] Table 1

[0078] project Polypropylene A% Polypropylene B% Polyethylene% Compound additives / ppm Example 1 80 20 0 1800 Example 2 80 10 10 1800 Example 3 70 15 15 1800 Example 4 70 10 20 1800 Example 5 65 15 20 1800 Example 6 65 10 25 1800 Example 7 65 10 25 1000 Example 8 65 10 25 1500 Example 9 65 10 25 2300 Comparative Example 1 — — — — Comparative Example 2 — — — —

[0079] Table 2 is the data of polypropylene coating prepared under different conditions

[0080]

[0081]

[0082] Test example:

[0083] 1. Observe the product particles obtained in Example 6 and Comparative Example 1 on a black background. The appearance of the products obtained in Example 6 and Comparative Example 1 is as follows: Figure 1 As shown, Figure 1 a is the product obtained in Example 6, which is whiter and not yellowish, and has better particle uniformity; Figure 1 b is comparative example 1, the product is yellow and fine, and the particles are relatively coarse, indicating that its processing performance and glossiness are poor;

[0084] 2. The mechanical properties of the polypropylene coating prepared in Example 6, Comparative Example 1 and Comparative Example 2 were tested and the results were as follows: Figure 2 shown by Figure 2 It can be seen that although the product of Comparative Example 1 can withstand greater tensile stress under the same tensile strain, the tensile strength of Comparative Example 1 and the PE mixture, that is, Comparative Example 2, is similar to that of Example 6, which shows that the mechanical properties of the present invention have reached the technical level of mainstream materials in the market;

[0085] 3. The melting point and crystallization temperature of the polypropylene coating prepared in Example 6, Comparative Example 1 and Comparative Example 2 of the present invention are detected and the temperature curve is plotted. Figure 3 As shown in a~b. Figure 3 a It can be seen from the heating curve that the highest melting point of Example 6 is about 7°C lower than that of Comparative Examples 1 and 2. The lower melting point is conducive to using a lower processing temperature when coating, saving energy consumption and maintaining the properties of the raw materials;

[0086] Figure 3 b It can be seen from the cooling curve that the highest crystallization temperature of Example 6 is about 10°C lower than that of Comparative Examples 1 and 2. The lower crystallization temperature allows the coating film to have a longer cooling and molding time, which is beneficial to the mutual penetration between the coating and the coated molecules, and better improves the bonding strength between the coating and the base fabric.

[0087] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a polypropylene coating material by non-chemical degradation, characterized in that: The following steps are involved: (1) The polypropylene powder B and the compound additive are mixed to obtain a mixture, and the mixture, the polypropylene powder A, and the polyethylene are weighed by a loss-in-weight scale and simultaneously added to a twin-screw extruder for melting, mixing, and extrusion; (2) drawing the sample extruded in step (1) and cooling and crystallizing it; (3) drying, pelletizing and screening the cooled material strips in step (2); (4) blending and drying the qualified products in step (3) to obtain a polypropylene coating material; Polypropylene powder A, mixed material and polyethylene are mixed in a mass ratio of 7-14:1-3:1-5; The amount of compound additive added is 1000-2300ppm.

2. The method for preparing a polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: Polypropylene powder A, mixed material and polyethylene are mixed in a mass ratio of 13:2:

5.

3. The method for preparing polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: Polypropylene powder A, mixed material and polyethylene are mixed in a mass ratio of 13:3:

4.

4. The method for preparing a polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: The melting index of polypropylene powder A is 60 g / 10 min; the melting index of polypropylene powder B is 3 g / 10 min.

5. The method for preparing polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: The product brand of polypropylene powder A is any one of M600E, H9018, M065E, M60T, PPR-M55-S, PPH-M600N, and S980 powder; The product brand of polypropylene powder B is any one of L5E89, 1102K, PPH-T035, S003G, and T30S powder.

6. The method for preparing polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: The polyethylene is low-density polyethylene; the melt index of the polyethylene is 5 to 10 g / 10 min; the product brand of the polyethylene is any one of 1C7A, 1C10A, 950, LB7500, LD251, and 2426H.

7. The method for preparing a polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: The compound additive consists of 1 part by weight of a primary antioxidant Irganox 1010, 2 parts by weight of a secondary antioxidant Irgafos 168, 0.5 parts by weight of Utranox 622 and 1 part by weight of calcium stearate.

8. The method for preparing polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: The temperature of the desalted water used is 25-30°C.

9. The method for preparing a polypropylene coating material by non-chemical degradation according to claim 1, characterized in that: The mixing method used for cyclic mixing is O-type pneumatic conveying to drive the sample to circulate in the homogenization bin, the mixing time is 3 to 5 hours, and the drying temperature is 70 to 90°C.

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