Bio-based sustained and controlled release coating material master batch capable of being naturally degraded in soil and preparation of bio-based sustained and controlled release coating material master batch

Abstract

The invention discloses a bio-based sustained and controlled release coating material master batch capable of being naturally degraded in soil and preparation of the bio-based sustained and controlled release coating material master batch, and belongs to the technical field of environment-friendly agricultural materials. The master batch is prepared from high-crystallinity PHB, PHBV, superfine talcum powder, nano silicon dioxide, a hydrophobic filler, an organosilane coupling agent, a diisocyanate cross-linking agent, a plasticizer and a functional additive through raw material pretreatment, membrane material mixing, melt plasticizing, underwater pelletizing, low-temperature drying, screening and packaging, the particle size of particles is 2-3 mm, the melt index is 8-15 g / 10 min, and the contact angle is larger than or equal to 90 degrees; according to the invention, through synergistic innovation of the formula, '25-day micro-release + 30-day / 70-day accurate release 'is realized, nitrogen and phosphorus non-point source pollution is reduced, the saturated water resistance is excellent, and the fertilizer is completely biodegraded in soil within 100 days and has no environmental residue; the degradable film-coated master batch is simple in preparation process, controllable in cost, suitable for an existing fertilizer film-coating production line, capable of coating various fertilizer core materials and suitable for various crops such as rice, fruits, vegetables and tobaccos, solves the problems that a traditional film-coated master batch is non-degradable, single in release period and poor in water resistance, and has wide application and popularization prospects.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental protection type reducing agricultural nitrogen, phosphorus and micro-plastic non-point source pollution, in particular to a bio-based slow / controlled release fertilizer coating material master batch which can be naturally degraded in soil and a preparation method and application thereof, and especially suitable for zero micro-release demand in saturated water environment of rice seedbed, and can accurately realize multiple nutrient release periods such as 30 days, 70 days or 90 days. BACKGROUND

[0002] The core of slow / controlled release fertilizer is coating material, and traditional coating master batch mostly uses petroleum-based materials such as polyethylene (PE), polyurethane (PU) or PBAT, which can achieve certain controlled release effect, but has two key defects: one is non-biodegradable or non-degradable under natural conditions, which will cause soil and environmental white pollution in long-term use, and does not meet the agricultural green development policy; the other is poor water resistance, which is easy to absorb water and penetrate in saturated water environment such as rice seedbed, resulting in early release of nutrients and seedling burn, and cannot meet the demand of "micro-release in seedbed and long-term stable fertilizer supply in field". Although the existing bio-based coating material (such as single PHA-based) solves the degradation problem, it still has the following shortcomings: 1) single release period, which cannot adapt to the nutrient demand of different crops (short-term field crops and long-term fruit trees); 2) poor water resistance under saturated conditions, and the film layer is easy to absorb water, swell and crack; 3) high cost of formula (such as using pure hydrophobic fumed silica and PCL plasticizer), which limits the scale promotion; 4) complex preparation process, and poor compatibility with existing fertilizer coating production line. Therefore, it is an urgent need in the current agricultural environmental protection material field to develop an environmental protection type slow / controlled release coating master batch with the characteristics of "bio-based full degradation, saturated water resistance, customizable release period, controllable cost and suitable for scale production". SUMMARY

[0003] (I) Technical problems to be solved In view of the defects of the existing coating master batch such as non-degradability, poor saturated water resistance, single release period and high cost, the present application provides a bio-based slow / controlled release fertilizer coating material master batch which can be naturally degraded in soil, and realizes "25-day zero release + 30-day / 70-day accurate release" through formula synergistic innovation and process optimization, and balances environmental protection, practicality and economy.

[0004] (II) Technical scheme To achieve the above-mentioned purpose, the present application adopts the following technical scheme: A bio-based slow / controlled release coating master batch, the core formula is composed of high-crystalline PHB, PHBV, ultra-fine talcum powder, nano-silicon dioxide, hydrophobic filler, organic silane coupling agent, diisocyanate crosslinking agent, plasticizer and functional additive, and each component synergistically acts: 1. Core substrate synergistic design: High crystallinity PHB (crystallinity ≥ 70%) provides excellent water resistance and anti-degradation, PHBV improves film layer flexibility, and the blending of the two solves the problem of single PHA-based film layer brittleness; at the same time, by adjusting the PHB / PHBV ratio, the late degradation rate of the film layer can be precisely controlled (the higher the PHB ratio, the slower the degradation, and the longer the release period); 2. Hydrophobic filler innovation: Using a "hydrophobic fumed silica + hydrophobic talc powder mixed system" or "pure hydrophobic fumed silica", both of which utilize fumed silica to fill the film layer voids and improve density, and through the use of hydrophobic talc powder, the cost is reduced by 60% compared to pure fumed silica, and the film layer's saturation water resistance is synergistically enhanced (contact angle ≥ 90°), avoiding water penetration; 3. Cost-effective plasticizer replacement: PEG-6000 replaces high-priced PCL, PEG-6000 has excellent compatibility with PHA, can reduce the melting temperature (120-145°C), avoid the decomposition of fertilizer core materials (such as urea) during coating, and at the same time, the cost is reduced by more than 50%; 4. Precise control of functional additives: Starch-based degrading agent (30-day release period) provides carbon source for microorganisms, accelerating the late disintegration of the film layer; food-grade calcium carbonate (70-day release period) slightly adjusts the pH of the film layer, delaying microbial activity, achieving customized release period, and both are biocompatible materials, not affecting degradation; The preparation method adopts a large-scale process of "pretreatment-mixing-melt extrusion-underwater granulation-low temperature drying", which does not require complex equipment and has strong compatibility with existing fertilizer coating production lines. The finished product is a 2-3mm cylindrical particle, which is easy to store and use.

[0005] (Three) Beneficial effects 1. Environmentally friendly and degradable: The entire biobased formula is completely degraded in soil within 55-85 days, leaving no residue, in line with green agricultural policies; 2. Excellent saturation water resistance: Contact angle ≥ 90° at 25°C, zero release (release rate ≤ 5%) under saturated water environment for rice seedbed for 25 days, film layer has no swelling and no damage; 3. Customizable release period: Precise realization of "25-day zero release + 30-day release" (for short-term crops) or "25-day zero release + 70-day release" (for long-term crops), cumulative release rate ≥ 90%, daily fluctuation ≤ ±1%, reducing nitrogen and phosphorus surface pollution; 4. Controllable cost: By replacing high-priced raw materials with hydrophobic talc powder and PEG-6000, the cost of large-scale production per ton is 3000-5000 yuan lower than that of existing biobased master batches; 5. Strong adaptability: Can coat various core materials such as urea, compound fertilizer, and organic fertilizer, the master batch and core material ratio is 1:8~1:10, compatible with existing melt extrusion coating production lines, without the need for equipment modification. DETAILED DESCRIPTION

[0006] Example 1 (30-day release period: 25-day micro-release + 30-day release) Raw material formula (weight parts) High crystallinity PHB (crystallinity ≥ 70%) 52 parts, PHBV 38 parts, 2000 mesh superfine talc powder 36 parts, nano silicon dioxide (20-50 nm) 0.6 parts, hydrophobic fumed silica 0.27 parts + hydrophobic talc powder 0.63 parts, organosilane coupling agent (KH-570) 1.2 parts, MDI 0.4 parts, PEG-6000 0.28 parts, starch-based degradation agent 0.6 parts; Preparation method (1) Raw material pretreatment: powder raw material was vacuum dried at 105°C for 2h, with a moisture content of 0.2%; (2) Film material mixing: all raw materials were added according to the formula and stirred at 1000 rpm for 18 min; (3) Melt plasticization: the temperature of the double screw extruder was 120°C in zone 1, 125°C in zone 2, and 130°C in zone 3, with a screw speed of 120 rpm; (4) Underwater pelletization: the water temperature was 22°C, and the particle size was 2.5 mm; (5) Low-temperature drying: 40°C drying for 1h, with a moisture content of 0.4%; (6) Screening and packaging: 2-3 mm screen mesh screening, finished product; Example 2 (70-day release period: 25-day micro-release + 70-day release) Raw material formula (weight parts) High crystallinity PHB (crystallinity 70%) 78 parts, PHBV 22 parts, 2000 mesh superfine talc powder 35 parts, nano silicon dioxide (20-50 nm) 0.7 parts, hydrophobic fumed silica 0.9 parts, organosilane coupling agent (KH-570) 1.3 parts, MDI 0.65 parts, PEG-6000 0.29 parts, food-grade calcium carbonate 0.4 parts; Preparation method (1) Raw material pretreatment: powder raw material was vacuum dried at 105°C for 2h, with a moisture content of 0.3%; (2) Film material mixing: all raw materials were added according to the formula and stirred at 1000 rpm for 20 min; (3) Melt plasticization: the temperature of the double screw extruder was 130°C in zone 1, 135°C in zone 2, and 145°C in zone 3, with a screw speed of 100 rpm; (4) Underwater pelletization: the water temperature was 25°C, and the particle size was 2.8 mm; (5) Low-temperature drying: 40°C drying for 1h, with a moisture content of 0.5%; (6) Screening package: 2-3 mm screen, finished product; Comparative Example 1 (traditional PE-based film coating masterbatch) Raw materials: PE 90 parts, talcum powder 10 parts, calcium stearate 0.5 parts, preparation method same as Example 1 (extrusion temperature 160-170℃); Comparative Example 2 (single PHA-based film coating masterbatch without functional additives) Raw materials: PHB 80 parts, PHBV 20 parts, hydrophobic fumed silica 1 part, MDI 0.5 parts, preparation method same as Example 1.

[0007] Performance test The masterbatch and slow-release fertilizer coated with urea of Examples 1-2 and Comparative Examples 1-2 were tested, and the results are as follows: Test item Example 1 (30D masterbatch) Example 2 (70D masterbatch) Comparative Example 1 (PE-based) Comparative Example 2 (single PHA-based) Masterbatch melt index (g / 10 min) 13.2 9.8 20.5 11.5 Masterbatch contact angle (°) 92.5 96.3 85.7 88.2 Saturation water release rate in 25 days (%) 3.1 2.8 15.6 8.9 Target period cumulative release rate (%) 92.3 (26-55 days) 91.7 (26-95 days) 88.5 (26-60 days) 75.3 (26-80 days) Soil degradation rate (180 days, %) 100 100 0 82.5 Biuret content after coating (%) 0.25 0.28 0.85 0.42 Cost per ton of masterbatch (yuan) 24935 28798 8500 32000 Test method explanation 1. Melt index: determined according to GB / T 3682-2018 (190℃, 2.16kg); 2. Contact angle: determined by contact angle measuring instrument (25℃, deionized water); 3. Release rate: saturated water immersion test (25℃) + soil simulation release test, detected by ultraviolet spectrophotometry; 4. Degradation rate: soil burial test (25℃, soil moisture content 60%), calculated by weight method; 5. Biuret content: determined by colorimetry according to GB / T 2441.2-2010.

[0008] Explanation of specific embodiments The core innovation of the present application is "high crystallinity PHB / PHBV blending system + hydrophobic filler combination + precise control of functional additives", through the synergy of formula proportion and process parameters, two customized release periods are realized. The test results of Examples 1-2 show that the masterbatch of the present application is significantly better than the traditional PE-based masterbatch (Comparative Example 1) and the single PHA-based masterbatch (Comparative Example 2) in terms of saturated water resistance, release accuracy and degradability, and has lower cost and stronger adaptability. Comparative Example 1 cannot meet the demand of green agriculture due to its non-degradability and poor water resistance; Comparative Example 2 has limited practicality due to the uncontrollable release period and incomplete degradation without functional additives; the above examples can be understood as exemplary, and cannot be understood as a limitation of the present application, and the changes, modifications, replacements and modifications of the above examples by ordinary skilled in the art are within the protection scope of the present application.

Claims

1. A bio-based slow controlled release film coated master batch, characterized in that, consists of the following raw materials by weight: high crystalline polyhydroxybutyrate (PHB) 50-80 parts, polyhydroxybutyrate-valerate copolymer (PHBV) 20-40 parts, 2000 mesh superfine talc powder 30-40 parts, nano-silicon dioxide (20-50 nm) 0.5-0.8 parts, hydrophobic filler 0.8-1 part, organosilane coupling agent (KH-570) 1.0-1.5 parts, diisocyanate crosslinking agent 0.3-0.7 parts, plasticizer 0.2-0.3 parts, functional additive 0.3-0.8 parts; - the crystallinity of the high crystalline PHB is ≥70%; - the hydrophobic filler is hydrophobic fumed silica, or a mixed system of hydrophobic fumed silica and hydrophobic talc powder (mixed mass ratio 1:1~3:7); - the plasticizer is tributyl citrate or polyethylene glycol 6000 (PEG-6000); - the functional additive is starch-based degrading agent or food-grade calcium carbonate; - the coated master batch is a 2-3 mm cylindrical particle, the melt index is 8-15 g / 10 min (190°C, 2.16 kg), the contact angle with water at 25°C is ≥90°, and the nutrient release rate in 25 days in a saturated water environment of rice seedling bed is ≤5%.

2. The bio-based slow controlled release film coated masterbatch according to claim 1, wherein, The release period of the master batch is "25 days of zero release + subsequent 30 days of release", and the raw material weight parts at this time are: high crystalline PHB 50-55 parts, PHBV 35-40 parts, hydrophobic filler (hydrophobic fumed silica: hydrophobic talc powder = 3:7) 0.8-1 part, diisocyanate crosslinking agent 0.3-0.5 part, functional additive is starch-based degrading agent 0.5-0.8 part, plasticizer is PEG-6000 0.2-0.3 part.

3. The bio-based slow controlled release film coated masterbatch according to claim 1, wherein, The release period of the master batch is "25 days of zero release + subsequent 70 days of release", and the raw material weight parts at this time are: high crystalline PHB 75-80 parts, PHBV 20-25 parts, hydrophobic filler is pure hydrophobic fumed silica 0.8-1 part, diisocyanate crosslinking agent 0.6-0.7 part, functional additive is food-grade calcium carbonate 0.3-0.5 part, plasticizer is PEG-6000 0.2-0.3 part.

4. The bio-based slow controlled release film coated masterbatch according to claim 1, wherein, The specific surface area of the hydrophobic fumed silica is 150-200 m² / g, and the hydrophobicity is ≥95%; the particle size of the hydrophobic talc powder is ≥2000 mesh, and the hydrophobicity is ≥90%.

5. The bio-based slow controlled release film coated masterbatch according to claim 1, wherein, The diisocyanate crosslinking agent is diphenyl methane diisocyanate (MDI); the degree of polymerization of the starch-based degrading agent is 500-1000, and the particle size of the food-grade calcium carbonate is ≤10 μm.

6. A process for the preparation of a bio-based modified release film coated master batch as claimed in any one of claims 1 to 5, characterized in that, The steps include: (1) Raw material pretreatment: all powder raw materials (superfine talc powder, nano-silicon dioxide, hydrophobic filler, functional additive) are placed in a 105°C vacuum dryer for drying for 2 h, and the water content is controlled to ≤0.3%; (2) Film material mixing: high crystalline PHB, PHBV, pretreated powder raw materials, organosilane coupling agent, diisocyanate crosslinking agent, and plasticizer are added in sequence according to weight parts, and are put into a double-shaft paddle high-speed mixer, stirred at 1000 rpm for 15-20 min, and mixed uniformly; (3) Melting and plasticizing: The mixture is fed into a twin-screw extruder, the barrel temperature is controlled at 120-145℃ (corresponding to 120-130℃ for a 30-day release cycle and 130-145℃ for a 70-day release cycle), the screw speed is 100-120 rpm, and continuous extrusion is carried out after melting and plasticizing. (4) Underwater pelletizing: After the extruded material is extruded through the die head, it is pelletized by an underwater pelletizer with a particle size of 2-3 mm and a pelletizing water temperature of 20-25℃. (5) Low-temperature drying: Place the pelleted masterbatch in a 40℃ hot air circulating dryer and dry for 1 hour, with a moisture content ≤0.5%; (6) Screening and packaging: The unqualified particles are removed by screening through a 1-4mm sieve, and then sealed and packaged to obtain the finished product.

7. The preparation method according to claim 6, characterized in that, In step (3), the barrel temperature of the twin-screw extruder is controlled in zones: Zone 1 120-125℃, Zone 2 125-135℃, Zone 3 130-145℃, and the head temperature is 5-10℃ lower than the temperature of Zone 3.

8. Use of a bio-based controlled release film coated masterbatch according to any one of claims 1 to 5, characterized in that, The masterbatch is used to coat fertilizer core materials (urea, compound fertilizer, organic fertilizer). The mass ratio of masterbatch to core material is 1:8 to 1:

20. Slow-release fertilizer is prepared by melt extrusion coating or fluidized bed spraying process. The slow-release fertilizer is suitable for crops such as rice, fruits and vegetables, tobacco, and Chinese medicinal materials, realizing "zero release in the seedbed + precise fertilization in the field".

9. Use according to claim 8, characterized in that, The coating thickness of the slow-release fertilizer is 0.16-0.22 mm. It is completely biodegradable in the soil within 180 days and leaves no environmental residue.