Environment-friendly sodium polyacrylate rodenticide and preparation method thereof

Abstract

This invention discloses an environmentally friendly sodium polyacrylate rodenticide and its preparation method, belonging to the field of agricultural pest control technology. The rodenticide uses sodium polyacrylate granules as the core material and a biodegradable ternary blend of polylactic acid, poly(3-hydroxybutyrate), and ethyl cellulose as the coating matrix. A uniform and dense coating layer of 5-10 μm is formed on the surface of the core material using a fluidized bed bottom spraying process. The rodenticide provided by this invention maintains over 92% disintegration activity within 15 days in a high-humidity accelerated aging test, significantly extending its effective period compared to uncoated samples. Simultaneously, the coating layer has moderate hardness, allowing environmental moisture to penetrate and activate the expansion properties of sodium polyacrylate only after micro-cracks are created by rodent gnawing, achieving targeted rodent control. The entire system is biodegradable, balancing environmental friendliness, long-lasting effect, and storage and transportation stability. It overcomes the limitations of humidity on the application scenarios of sodium polyacrylate rodenticides, and the process is stable and controllable, suitable for industrial-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of agricultural pest control, specifically relating to an environmentally friendly sodium polyacrylate rodenticide and its preparation method. Background Technology

[0002] Rodent infestations are a significant biological hazard affecting agricultural production, grain storage, and urban public health. They not only cause reduced grain yields and damage to facilities but also spread various zoonotic diseases, seriously threatening agricultural production safety and public health security. Currently, most rodenticides on the market are anticoagulant chemical rodenticides. Although they are fast-acting, they have many problems, such as easy development of resistance, accidental poisoning by humans and animals, secondary poisoning that harms natural enemies, and environmental pollution.

[0003] Sodium polyacrylate, as a superabsorbent polymer, can kill rodents through physical action: after being ingested by rodents, it rapidly absorbs water and swells in the digestive tract, blocking the intestines and causing death. It boasts advantages such as no resistance, no toxicity, no secondary poisoning, and environmental friendliness, and its applications are already publicly disclosed in existing technologies. However, this type of rodenticide has a fatal technical flaw: sodium polyacrylate itself has extremely strong hygroscopic properties. When applied in high-humidity environments (such as the rainy season in the south, sewers, damp grain warehouses, and farms), it will absorb moisture and swell prematurely before being ingested by rodents, completely losing its rodent-killing activity. Its effective period is extremely short, making it unsuitable for long-term stable use in high-humidity environments, severely hindering the widespread application of this type of environmentally friendly rodenticide.

[0004] Existing coating modification technologies for superabsorbent polymers mostly use non-degradable polymer materials. While these can achieve a certain degree of moisture barrier effect, they pose environmental pollution problems and do not meet the requirements for the development of environmentally friendly pesticides. On the other hand, biodegradable coating materials often suffer from poor interfacial bonding, easy peeling of the coating layer, and unsuitable hardness. The interfacial bonding between existing biodegradable polymer coating systems and polar sodium polyacrylate core materials is insufficient, and the coating layer is prone to peeling and delamination during transportation and application, leading to the failure of the moisture barrier structure. At the same time, excessive hardness will cause rodents to refuse to chew, thus failing to achieve the desired effect; while excessive hardness will easily lead to damage during transportation and application, resulting in the loss of the moisture barrier effect. In addition, existing coating technologies cannot achieve "targeted water control," that is, complete moisture barrier and activation when not chewed, and rapid water penetration to activate the activity after chewing, making it difficult to balance long-term effectiveness and efficacy.

[0005] Therefore, developing a sodium polyacrylate rodenticide that is environmentally friendly and biodegradable, has long-lasting stability in high humidity environments, excellent interfacial bonding, targeted efficacy, and is compatible with rodent gnawing characteristics is a technical challenge that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned deficiencies in existing technologies, the present invention aims to provide an environmentally friendly sodium polyacrylate rodenticide that completely solves the problem of premature deterioration of sodium polyacrylate rodenticides in high humidity environments through a specific biodegradable ternary blend coating system and a precise fluidized bed coating process.

[0007] To achieve the above objectives, the present invention discloses the following technical solutions: In a first aspect, the present invention provides an environmentally friendly sodium polyacrylate rodenticide, comprising a core material and a biodegradable coating layer covering the surface of the core material; The core material is sodium polyacrylate particles with a particle size of 150-200μm; The matrix of the coating layer is a ternary blend of polylactic acid (PLA), poly(3-hydroxybutyrate) (PHB) and ethyl cellulose (EC), wherein the mass ratio of polylactic acid, poly(3-hydroxybutyrate) and ethyl cellulose is (3-5):(1-2):1; the thickness of the coating layer is 5-10 μm.

[0008] Preferably, the coating layer accounts for 8%-15% of the total mass of the rodenticide.

[0009] Preferably, the sodium polyacrylate particles have a water absorption ratio of ≥300 times.

[0010] Preferably, the poly(3-hydroxybutyrate) has a number-average molecular weight of 5-200,000 Da.

[0011] Secondly, the present invention provides a method for preparing the environmentally friendly sodium polyacrylate rodenticide described in the first aspect, comprising the following steps: S1. Preparation of coating solution: Weigh polylactic acid, poly(3-hydroxybutyrate) and ethyl cellulose in a mass ratio of 3-5:1-2:1, add them to chloroform solvent, stir until completely dissolved, and obtain a uniform coating solution for later use. S2. Core material preheating treatment: Select sodium polyacrylate particles with a particle size of 150-200μm, place them in a fluidized bed, and preheat them until the particle temperature stabilizes at 40℃, so that the particles are in a uniform fluidized state. S3. Fluidized bed bottom spray coating: Maintain the fluidized bed inlet air temperature at 45℃ and set the atomization pressure at 0.5MPa. Atomize and spray the coating solution prepared in S1 onto the surface of the fluidized sodium polyacrylate particles. After spraying, continue fluidized drying to remove residual solvent, cool and discharge to obtain an environmentally friendly sodium polyacrylate rodenticide with a coating thickness of 5-10μm.

[0012] Preferably, in step S1, the solid content of the coating solution is 8%-12%, and the dissolution process is carried out at 25-30°C in the dark, with stirring at 300-500 rpm for 3-5 hours until the polymer is completely dissolved.

[0013] Preferably, in step S2, the inlet air temperature for preheating is 40°C, the fluidizing air velocity is 0.8-1.2 m / s, and the preheating time is 15-20 min.

[0014] Preferably, in step S3, the feed rate of the coating solution is 2-4 mL / min, and the fluidization air velocity is maintained at 0.8-1.2 m / s during the spraying process.

[0015] Preferably, in step S3, after the spraying is completed, the coating is continued to be fluidized and dried at an air inlet temperature of 45°C for 10-15 minutes until the residual amount of chloroform is ≤10ppm.

[0016] The beneficial effects of this invention are: 1. This invention is the first to use a ternary blend of polylactic acid, poly(3-hydroxybutyrate), and ethyl cellulose as the coating matrix. The PHB molecular chain contains a large number of polar ester groups, which can form stable intermolecular hydrogen bonds with the carboxyl and hydroxyl groups on the surface of sodium polyacrylate core material. This solves the problems of poor compatibility and weak bonding between the coating system and the core material interface. At the same time, PHB has excellent compatibility with PLA and EC, which can make the ternary blend coating layer form a uniform and continuous phase structure, further enhancing the interfacial adhesion. 2. Polylactic acid, poly(3-hydroxybutyrate), and ethyl cellulose are all hydrophobic and biodegradable polymers. When the three are blended in a specific ratio, the resulting coating layer has a higher density, is free of pinholes and defects, and can completely isolate moisture in the environment, preventing the core material sodium polyacrylate from absorbing moisture, swelling, and becoming inactive in advance without being eaten, thus achieving long-term activation. Detailed Implementation

[0017] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0018] Unless otherwise specified, the experimental methods used in the specific embodiments are all conventional methods; the materials and reagents used are all commercially available unless otherwise specified; and the percentages mentioned in the specific embodiments are all mass percentages unless otherwise specified.

[0019] I. Raw materials used in the examples Sodium polyacrylate resin granules: agricultural grade superabsorbent resin, deionized water absorption ratio ≥300 times, commercially available; Polylactic acid (PLA): Number average molecular weight 100,000 Da, commercially available; Ethyl cellulose (EC): ethoxylate content 48%-49.5%, commercially available; Poly(3-hydroxybutyrate) (PHB): a biodegradable polyester, commercially available; chloroform: analytical grade reagent.

[0020] II. An environmentally friendly sodium polyacrylate rodenticide The specific method for preparing the rodenticide is as follows: S1. Preparation of coating solution Accurately weigh polylactic acid, poly(3-hydroxybutyrate) and ethyl cellulose according to the preset mass ratio (3-5):(1-2):1, add them to chloroform solvent, and stir at 300-500 rpm for 3-5 hours at 25-30℃ in the dark until the polymer is completely dissolved, to obtain a uniform transparent coating solution with a solid content of 8%-12%, and seal it in the dark for later use.

[0021] S2, Core material preheating treatment Sodium polyacrylate particles with a diameter of 150-200μm are screened using a standard sieve, accurately weighed, and placed in the material chamber of the fluidized bed bottom spraying equipment. The inlet air temperature is set to 40℃, the fluidization air velocity is 0.8-1.2m / s, and the fluidization preheating is started for 15-20 minutes to stabilize the particle temperature at 40℃ and ensure that the particles are in a uniformly dispersed fluidized state without agglomeration or dead zones.

[0022] S3, Fluidized bed bottom spray coating preparation Maintain the fluidized bed inlet air temperature at 45℃, set the atomization pressure to 0.5MPa, and the peristaltic pump feed rate to 2-4mL / min. The coating solution prepared in S1 is uniformly atomized and sprayed onto the surface of continuously fluidized sodium polyacrylate particles through a bottom spray gun. During the spraying process, the fluidization state is monitored in real time, and the fluidization air velocity is adjusted to avoid particle agglomeration and ensure uniform deposition of the coating layer. After spraying, maintain an inlet air temperature of 45℃ and a fluidization air velocity of 0.8-1.2m / s, and continue fluidizing and drying for 10-15 minutes to allow the residual chloroform to completely evaporate (residual amount ≤10ppm); then turn off the heating, keep the fluidized state and cool to room temperature, and discharge the material to obtain an environmentally friendly sodium polyacrylate rodenticide with a coating thickness of 5-10μm.

[0023] III. Examples and Comparative Examples 1. Example 1 The environmentally friendly sodium polyacrylate rodenticide of this embodiment has a core material of sodium polyacrylate particles with a particle size of 150-200μm, and a coating matrix of PLA, PHB and EC in a mass ratio of 4:1:1. The coating thickness is 8μm and the coating accounts for 10% of the total mass; wherein PHB has a number average molecular weight of 100,000 Da.

[0024] The preparation method is as follows: S1. Preparation of coating solution: Weigh 400g PLA, 100g PHB and 100g EC in a mass ratio of 4:1:1, add them to 5400g chloroform solvent, stir at 400rpm for 3.5h at 25℃ in the dark until the polymer is completely dissolved, and obtain a uniform transparent coating solution with a solid content of 10%. Seal and protect from light for later use. S2. Core material preheating treatment: 5400g of sodium polyacrylate particles with a particle size of 150-200μm are screened and placed in the material chamber of the fluidized bed bottom spraying equipment. The inlet air temperature is set to 40℃, the fluidization air velocity is 1.0m / s, and the preheating is carried out for 18min to stabilize the particle temperature at 40℃ and put it into a uniform fluidized state. S3. Fluidized bed bottom spray coating: Maintain the fluidized bed inlet air temperature at 45℃, set the atomization pressure to 0.5MPa, and the peristaltic pump feed rate to 3mL / min. Atomize and spray the coating solution onto the surface of the fluidized sodium polyacrylate particles. Maintain the fluidization air velocity at 1.0m / s during the spraying process to avoid particle agglomeration. After spraying, maintain the inlet air temperature at 45℃ and continue fluidizing and drying for 12min to remove residual chloroform (residual amount ≤8ppm). Then turn off the heating, fluidize and cool to room temperature, and discharge to obtain the target rodenticide Example 1.

[0025] Example 2 The environmentally friendly sodium polyacrylate rodenticide of this embodiment has a core material of sodium polyacrylate particles with a particle size of 150-200μm, and a coating layer matrix of PLA, PHB and EC in a mass ratio of 5:2:1. The coating layer has a thickness of 10μm and accounts for 12% of the total mass; wherein PHB has a number average molecular weight of 150,000 Da.

[0026] The preparation method is as follows: Preparation of S1 coating solution: Weigh 500g PLA, 200g PHB and 100g EC in a mass ratio of 5:2:1, add them to 7200g chloroform solvent, stir at 350rpm for 4h at 28℃ and in the dark until the polymer is completely dissolved, and obtain a uniform coating solution with a solid content of 10%. Seal and protect from light for later use. S2. Core material preheating treatment: 6000g of sodium polyacrylate particles with a particle size of 150-200μm are screened and placed in the material chamber of the fluidized bed bottom spraying equipment. The inlet air temperature is set to 40℃, the fluidization air velocity is 1.2m / s, and the preheating is carried out for 20min to stabilize the particle temperature at 40℃ and put it into a uniform fluidized state. S3. Fluidized bed bottom spray coating: Maintain the fluidized bed inlet air temperature at 45℃, set the atomization pressure to 0.5MPa, and the peristaltic pump feed rate to 2.5mL / min. Atomize and spray the coating solution onto the surface of the fluidized sodium polyacrylate particles. Maintain the fluidization air velocity at 1.2m / s during the spraying process to avoid particle agglomeration. After spraying, maintain the inlet air temperature at 45℃ and continue fluidizing and drying for 15min to remove residual chloroform (residual amount ≤7ppm). Then turn off the heating, fluidize and cool to room temperature, and discharge to obtain the target rodenticide Example 2.

[0027] Example 3 The environmentally friendly sodium polyacrylate rodenticide of this embodiment has a core material of sodium polyacrylate particles with a particle size of 150-200μm, and a coating matrix of PLA, PHB and EC in a mass ratio of 3:1:1. The coating thickness is 5μm and the coating accounts for 8% of the total mass; wherein PHB has a number average molecular weight of 80,000 Da.

[0028] The preparation method is as follows: S1. Preparation of coating solution: Weigh 300g PLA, 100g PHB and 100g EC in a mass ratio of 3:1:1, add them to 3600g chloroform solvent, stir at 500rpm for 3h at 30℃ in the dark until the polymer is completely dissolved, and obtain a uniform coating solution with a solid content of 10%. Seal and protect from light for later use. S2. Core material preheating treatment: 4600g of sodium polyacrylate particles with a particle size of 150-200μm are screened and placed in the material chamber of the fluidized bed bottom spraying equipment. The inlet air temperature is set to 40℃, the fluidization air velocity is 0.8m / s, and the preheating is carried out for 15min to stabilize the particle temperature at 40℃ and put it into a uniform fluidized state. S3. Fluidized bed bottom spray coating: Maintain the fluidized bed inlet air temperature at 45℃, set the atomization pressure to 0.5MPa, and the peristaltic pump feed rate to 4mL / min. Atomize and spray the coating solution onto the surface of the fluidized sodium polyacrylate particles. Maintain the fluidization air velocity at 0.8m / s during the spraying process to avoid particle agglomeration. After spraying, maintain the inlet air temperature at 45℃ and continue fluidizing and drying for 10min to remove residual chloroform (residual amount ≤9ppm). Then turn off the heating, fluidize and cool to room temperature, and discharge to obtain the target rodenticide Example 3.

[0029] Comparative Example 1 The uncoated sodium polyacrylate particles, with a particle size of 150-200 μm, are the same as the core material used in Example 1, without any coating treatment.

[0030] Comparative Example 2 The pure PLA-coated sodium polyacrylate rodenticide has the same core material as in Example 1, and the coating layer is pure PLA with a thickness of 8 μm. The preparation method is completely the same as in Example 1 except that the coating solution is a trichloromethane solution of pure PLA.

[0031] Comparative Example 3 The pure EC-coated sodium polyacrylate rodenticide has the same core material as in Example 1, and the coating layer is pure EC with a thickness of 8 μm. The preparation method is completely consistent with Example 1 except that the coating solution is a chloroform solution of pure EC.

[0032] Comparative Example 4 The PLA / EC binary blend coated sodium polyacrylate rodenticide has the same core material as in Example 1. The coating matrix is ​​a binary blend of PLA:EC = 4:1, and the coating thickness is 8 μm. The preparation method is completely consistent with Example 1 except that the coating solution is a binary blend solution of PLA and EC.

[0033] Comparative Example 5 The PLA / PHB binary blend coated sodium polyacrylate rodenticide has the same core material as in Example 1. The coating matrix is ​​a binary blend of PLA:PHB = 4:1, and the coating thickness is 8 μm. The preparation method is completely consistent with Example 1 except that the coating solution is a binary blend solution of PLA and PHB.

[0034] IV. Test Examples 1. Interface integration performance testing Take a circular sheet of sodium polyacrylate with a thickness of 1-2 mm and a diameter of 3 cm. Spray the coating matrix corresponding to Examples 1-3 and Comparative Examples 2-5 onto the surface of the circular sheet. The film thickness is 8 μm. This is used to simulate the coating matrix coating the surface of sodium polyacrylate microparticles. Then, the interfacial adhesion between the coating layer and the core material is tested using the method of "GB / T 9286-2021 Paint and Varnish Film Cross-cut Test". The adhesion level is divided into 0-5, with level 0 being the best (no peeling) and level 5 being the worst (large-area peeling). A certain amount of rodenticide samples from Examples 1-3 and Comparative Examples 2-5 were taken respectively, and a simulated vibration test was conducted (vibration frequency 3Hz, amplitude 20mm, vibration time 2h) to test the integrity rate of the coating layer of the samples after vibration (the proportion of particles without detachment or peeling), simulating the integrity rate of the coating layer of the rodenticide under transportation and other environments. The results are shown in Table 1.

[0035] Table 1 Interface Integration Performance Test Results Sample number Cross-cut adhesion rating Coating integrity rate after vibration test Example 1 Level 0 99.6% Example 2 Level 0 99.8% Example 3 Level 1 98.7% Comparative Example 2 Level 4 62.3% Comparative Example 3 Level 3 75.1% Comparative Example 4 Level 2 82.5% Comparative Example 5 Level 2 84.2% Experimental conclusion: The interfacial adhesion between the ternary blend coating system and the sodium polyacrylate core material of this invention reaches level 0-1, which is far superior to the binary coating system and the single-component coating system. After vibration test, the integrity rate of the coating layer is close to 100%, which completely solves the defects of poor interfacial bonding and easy peeling of the existing coating system, and greatly improves the storage and transportation stability of the product.

[0036] 2. High Humidity Accelerated Aging Activity Retention Rate Test Test conditions: a constant temperature and humidity chamber with a temperature of 30℃ and a relative humidity of 90%±5% to simulate a high humidity application environment.

[0037] Test method: The samples of Examples 1-3 and Comparative Examples 1-5 were placed in a constant temperature and humidity chamber and samples were taken at 0 days, 3 days, 7 days and 15 days respectively. The water absorption swelling ratio of the samples was tested. The activity retention rate was calculated based on the swelling ratio at 0 days. The results are shown in Table 2.

[0038] Table 2 Results of Activity Retention Rate in High Humidity Accelerated Aging Test Sample number 0-day activity retention rate 3-day activity retention rate 7-day activity retention rate 15-day activity retention rate Example 1 100% 99.2% 97.8% 95.3% Example 2 100% 99.5% 98.2% 96.1% Example 3 100% 98.5% 96.3% 92.7% Comparative Example 1 100% 12.3% 0% 0% Comparative Example 2 100% 85.6% 62.4% 38.7% Comparative Example 3 100% 90.2% 78.5% 52.1% Comparative Example 4 100% 98.7% 96.2% 93.5% Comparative Example 5 100% 97.2% 93.5% 88.4% Experimental conclusion: The samples of this invention, after being placed in a high humidity environment for 15 days, all maintained an activity retention rate of over 92%, which is not only far superior to uncoated samples and single-component coated samples, but also superior to binary blend coated samples. The moisture-proof and activity-locking performance has been further upgraded, solving the problem of premature inactivation under high humidity environment.

[0039] 3. Bite efficacy test Experimental subjects: Healthy adult SD rats, half male and half female, weighing 200±20g, 10 rats per group.

[0040] Experimental method: The samples of Examples 1-3 and Comparative Examples 2-5 were mixed with the basic rat feed at a mass ratio of 1:1 and placed in the rat cages for free feeding. The feeding status (feeding rate / % = (feed amount - remaining amount) / feed amount × 100%) and mortality of the rats were observed for 7 days. The results are shown in Table 3.

[0041] Table 3 Results of the bite efficacy test Sample number Feed intake rate 7-day mortality rate Example 1 93.7% 100% Example 2 95.1% 100% Example 3 92.2% 100% Comparative Example 2 32.6% 20% Comparative Example 3 45.3% 30% Comparative Example 4 92.5% 100% Comparative Example 5 88.4% 90% Experimental conclusion: The hardness of the ternary blend coating layer of the present invention is adapted to the gnawing characteristics of rodents, and the consumption rate and mortality rate are both excellent, which are superior to the PLA / PHB binary system. While improving the interfacial bonding and moisture barrier properties, it retains excellent targeted efficacy.

[0042] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. An environmentally friendly sodium polyacrylate rodenticide, characterized in that, Includes the core material and a biodegradable coating layer covering the surface of the core material; The core material is sodium polyacrylate particles with a particle size of 150-200μm; The matrix of the coating layer is a ternary blend of polylactic acid, poly(3-hydroxybutyrate) and ethyl cellulose, wherein the mass ratio of polylactic acid, poly(3-hydroxybutyrate) and ethyl cellulose is (3-5):(1-2):1; the thickness of the coating layer is 5-10 μm.

2. The environmentally friendly sodium polyacrylate rodenticide according to claim 1, characterized in that, The coating layer accounts for 8%-15% of the total mass of the rodenticide.

3. The environmentally friendly sodium polyacrylate rodenticide according to claim 1, characterized in that, The sodium polyacrylate particles have a water absorption ratio of ≥300 times.

4. The environmentally friendly sodium polyacrylate rodenticide according to claim 1, characterized in that, The number average molecular weight of the poly(3-hydroxybutyrate) is 5-200,000 Da.

5. A method for preparing an environmentally friendly sodium polyacrylate rodenticide according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of coating solution: Weigh polylactic acid, poly(3-hydroxybutyrate) and ethyl cellulose in a mass ratio of 3-5:1-2:1, add them to chloroform solvent, stir until completely dissolved, and obtain a uniform coating solution for later use. S2. Core material preheating treatment: Select sodium polyacrylate particles with a particle size of 150-200μm, place them in a fluidized bed, and preheat them until the particle temperature stabilizes at 40℃, so that the particles are in a uniform fluidized state. S3. Fluidized bed bottom spray coating: Maintain the fluidized bed inlet air temperature at 45℃ and set the atomization pressure at 0.5MPa. Atomize and spray the coating solution prepared in S1 onto the surface of the fluidized sodium polyacrylate particles. After spraying, continue fluidized drying to remove residual solvent, cool and discharge to obtain an environmentally friendly sodium polyacrylate rodenticide with a coating thickness of 5-10μm.

6. The preparation method according to claim 5, characterized in that, In step S1, the solid content of the coating solution is 8%-12%, and the dissolution process is carried out at 25-30°C in the dark, with stirring at 300-500 rpm for 3-5 hours until the polymer is completely dissolved.

7. The preparation method according to claim 5, characterized in that, In step S2, the inlet air temperature for preheating is 40℃, the fluidizing air velocity is 0.8-1.2m / s, and the preheating time is 15-20min.

8. The preparation method according to claim 5, characterized in that, In step S3, the feed rate of the coating solution is 2-4 mL / min, and the fluidization air velocity is maintained at 0.8-1.2 m / s during the spraying process.

9. The preparation method according to claim 5, characterized in that, In step S3, after the spraying is completed, continue fluidization drying at an air inlet temperature of 45°C for 10-15 minutes until the residual amount of chloroform is ≤10ppm.