Talc-silica master granule and method for preparing the same

Abstract

The application provides a talcum powder-wollastonite master batch and a preparation method thereof, and belongs to the technical field of the preparation of master batches for biodegradable plastics. The talcum powder-wollastonite master batch is prepared by using modified talcum powder, modified wollastonite powder, polylactic acid, an antioxidant, stearic acid and a lubricant as raw materials, and by using a talcum powder-wollastonite processing production line and master batch production equipment in combination, and directly producing the master batch finished product from the talcum powder and wollastonite raw ore in one station. The talcum powder-wollastonite master batch has excellent mechanical properties, the preparation method reduces dust pollution in the powder packing, powder transportation and loading and unloading processes, and saves process energy consumption.

Description

Technical Field

[0001] This invention relates to the field of preparation technology of masterbatch for biodegradable plastics, and particularly to a talc-wollastonite masterbatch and its preparation method. Background Technology

[0002] The application of biodegradable plastics has become a trend. Previously used plastic products, due to their non-degradability or slow degradation rate, have posed a significant environmental pollution problem after disposal. With increasing public awareness of environmental protection, biodegradable plastic products are gaining popularity. Coupled with increasing environmental protection efforts and government policies, biodegradable plastics have attracted widespread research in recent years, and a number of manufacturers have emerged in the market. Biodegradable plastics refer to plastics that can be degraded by microorganisms in nature. Ideally, biodegradable plastics should not only be completely decomposed by environmental microorganisms but also possess excellent performance characteristics. Currently, plastic products are mainly used in supermarkets for shopping bags, disposable lunch boxes, mulch films, and agricultural films. Due to their high frequency of use, biodegradability is essential; otherwise, it will cause serious "white pollution" problems. Some provinces have already issued relevant policies requiring the use of biodegradable products.

[0003] Food delivery has become an integral part of the catering industry, leading to a continuous increase in demand for disposable lunch boxes. Disposable lunch boxes are currently common biodegradable plastic products. However, due to the relatively late start of this field, there are few domestic manufacturers producing such biodegradable disposable lunch boxes, and improvements are needed in both technology and raw material optimization. Since lunch boxes are inherently linked to the catering industry, environmental requirements are even higher whenever food is involved. Currently, manufacturers struggle to solve the dust problem caused by powder fillers such as calcium carbonate and talc used in the production process, frequently facing excessive dust levels in production workshops, making it difficult for their food-grade lunch boxes to pass environmental impact assessments. Converting powder into masterbatch is currently the ideal way to achieve dust-free production; on the other hand, with the increasing prevalence of disposable use, existing technologies are placing higher demands on the mechanical properties of lunch boxes. How to improve the mechanical properties of lunch boxes while ensuring they meet weight standards is also a current challenge. Summary of the Invention

[0004] The purpose of this invention is to provide a talc-wollastonite masterbatch and its preparation method, which solves the technical problems of poor environmental protection in the production process of biodegradable plastic products and insufficient mechanical properties of biodegradable plastic products in the prior art.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] The present invention provides a talc-wollastonite masterbatch, which is composed of the following components in parts by weight: 45-55 parts polylactic acid, 25-35 parts modified talc, 12-16 parts modified wollastonite, 0.5-2 parts antioxidant, 2-4 parts stearic acid, and 2-4 parts lubricant.

[0007] Furthermore, the number-average molecular weight of the polylactic acid is 100,000 to 150,000.

[0008] Furthermore, the antioxidant includes one or more of butylated hydroxyanisole, tert-butyl-4-hydroxyanisole, and β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester;

[0009] The lubricant includes one or more of calcium stearate, glyceryl stearate, and PE wax.

[0010] This invention provides a method for preparing the above-mentioned talc-wollastonite masterbatch, comprising the following steps:

[0011] Step 1): The raw talc ore is crushed to obtain talc powder, which is then mixed with coconut oil to obtain modified talc powder; the raw wollastonite ore is crushed to obtain wollastonite powder, which is then mixed with coconut oil to obtain modified wollastonite powder.

[0012] Step 2): Mix modified talc, modified wollastonite, polylactic acid, antioxidant, stearic acid and lubricant. The resulting mixture is extruded and pelletized to obtain talc-wollastonite masterbatch.

[0013] Furthermore, in step 1), the talc powder has a particle size of 1000-1500 mesh, and the amount of coconut oil added is 0.8-1% of the mass of the talc powder.

[0014] The mixing is carried out under stirring at a speed of 3000–3600 r / min.

[0015] Furthermore, in step 1), the particle size of the wollastonite powder is 600-800 mesh, and the amount of coconut oil added is 0.8-1% of the mass of the wollastonite powder.

[0016] The mixing is carried out under stirring at a speed of 3000–3600 r / min.

[0017] Furthermore, in step 2), the mixing is carried out under stirring, with a stirring speed of 1000-1200 r / min and a stirring time of 3-8 min;

[0018] The temperature of the mixture is 120–130°C;

[0019] The extrusion is carried out in an extruder with a rotation speed of 650-750 r / min and a feeding speed of 45-50 r / min;

[0020] The extruder includes 10 working sections, each with an independent temperature of 170–185°C, and a die head temperature of 180–190°C.

[0021] Furthermore, in step 2), the pelleting is carried out using a water ring hot cutting process, and the length of the resulting masterbatch is 3-5 mm.

[0022] Technical effects of the present invention:

[0023] This invention uses closed, continuous production equipment to directly produce masterbatch from raw ore, reducing dust pollution during intermediate powder packaging, transportation, and loading / unloading, and saving process energy consumption;

[0024] After modification, the coconut oil modifier coated on the surface of talc and wollastonite powder not only acts as a lubricant at high temperatures, which is beneficial for processing, but also improves the compatibility between the powder and the matrix resin compared to the method of directly mixing unmodified powder, modifier and resin.

[0025] A masterbatch was prepared by combining wollastonite powder with high aspect ratio and talc powder, and then applied to the production of lunch boxes. The needle-like structure of wollastonite increases the toughness of the lunch box, and together with the lamellar structure of talc powder, it forms a loose network structure. Compared with the prior art, the masterbatch of this invention, when used to produce lunch boxes of the same weight, increases the thickness while reducing the density of the lunch box, thereby further increasing the strength of the lunch box. Detailed Implementation

[0026] The present invention provides a talc-wollastonite masterbatch, which is composed of the following components in parts by weight: 45-55 parts polylactic acid, 25-35 parts modified talc, 12-16 parts modified wollastonite, 0.5-2 parts antioxidant, 2-4 parts stearic acid, and 2-4 parts lubricant.

[0027] In this invention, based on parts by weight, polylactic acid is preferably 48-52 parts, more preferably 50 parts; modified talc is preferably 27-33 parts, more preferably 30 parts; modified wollastonite is preferably 13-14 parts, more preferably 13.5 parts; antioxidant is preferably 1-1.8 parts, more preferably 1.5 parts; stearic acid is preferably 2.5-3.5 parts, more preferably 3 parts; and lubricant is preferably 2.5-3.5 parts, more preferably 3 parts.

[0028] In this invention, the number-average molecular weight of the polylactic acid is 100,000 to 150,000, preferably 120,000.

[0029] In this invention, the polylactic acid has a melting point of 175°C and a glass transition temperature of 60°C.

[0030] In this invention, the antioxidant includes one or more of butylated hydroxyanisole, tert-butyl-4-hydroxyanisole, and octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, preferably butylated hydroxyanisole, tert-butyl-4-hydroxyanisole, or octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, more preferably butylated hydroxyanisole or tert-butyl-4-hydroxyanisole, and even more preferably butylated hydroxyanisole;

[0031] The lubricant includes one or more of calcium stearate, glyceryl stearate and PE wax, preferably calcium stearate, glyceryl stearate or PE wax, more preferably calcium stearate or glyceryl stearate, and even more preferably calcium stearate.

[0032] This invention provides a method for preparing the above-mentioned talc-wollastonite masterbatch, comprising the following steps:

[0033] Step 1): The raw talc ore is crushed to obtain talc powder, which is then mixed with coconut oil to obtain modified talc powder; the raw wollastonite ore is crushed to obtain wollastonite powder, which is then mixed with coconut oil to obtain modified wollastonite powder.

[0034] Step 2): Mix modified talc, modified wollastonite, polylactic acid, antioxidant, stearic acid and lubricant. The resulting mixture is extruded and pelletized to obtain talc-wollastonite masterbatch.

[0035] In this invention, in step 1), the particle size of the talc powder is 1000-1500 mesh, preferably 1200-1400 mesh, more preferably 1300 mesh, and the amount of coconut oil added is 0.8-1% of the mass of the talc powder, preferably 0.9%.

[0036] The mixing is carried out under stirring at a speed of 3000-3600 r / min, preferably 3200-3400 r / min, and more preferably 3300 r / min.

[0037] In this invention, in step 1), the particle size of the wollastonite powder is 600-800 mesh, preferably 700 mesh, and the amount of coconut oil added is 0.8-1% of the mass of the talc powder, preferably 0.9%.

[0038] The mixing is carried out under stirring at a speed of 3000-3600 r / min, preferably 3200-3400 r / min, and more preferably 3300 r / min.

[0039] In this invention, the talc powder ore is preferably a high-purity talc powder ore with a whiteness of ≥92% and a silicon content of ≥65%. The crushing process involves first coarsely crushing the ore into small stones with a diameter of ≤6cm, and then grinding it into talc powder using the Yifeng dry grinding method.

[0040] In this invention, the wollastonite ore is preferably a high-purity wollastonite ore with a whiteness of ≥91% and a silica content of ≥53%. The crushing process involves first coarsely crushing the ore into small pieces with a diameter of ≤6cm, and then grinding it into wollastonite powder using an air jet mill.

[0041] In this invention, the modification of talc and wollastonite is carried out in a high-speed mixer, and the coconut oil is preferably heated to a liquid state of 40-60°C.

[0042] In this invention, in step 2), the mixing is carried out under stirring, the stirring speed is 1000-1200 r / min, preferably 1100 r / min, and the stirring time is 3-8 min, preferably 5 min;

[0043] The temperature of the mixture is 120–130°C, preferably 125°C;

[0044] The extrusion is carried out in an extruder with a rotation speed of 650-750 r / min, preferably 700 r / min, and a feeding speed of 45-50 r / min, preferably 48 r / min.

[0045] The extruder includes 10 working sections, wherein the temperature of each of the 10 working sections is independently 170-185°C, preferably 172-180°C, more preferably 175°C, and the die head temperature is 180-190°C, preferably 185°C.

[0046] In this invention, in step 2), the pelleting is carried out using a water ring hot cutting process, and the length of the resulting masterbatch is 3-5 mm, preferably 4 mm.

[0047] In this invention, in step 2), after the material is mixed evenly in a high-speed mixer, it is conveyed to another silo. The outlet of the silo containing the mixture is connected to the feed silo of a twin-screw extruder. After the mixture is fed into the extruder silo by an automatic weighing and batching system, it is extruded and pelletized by the extruder.

[0048] In this invention, the processing, modification and masterbatch production equipment for talc powder ore and wollastonite ore are used in combination. The production from ore to masterbatch is closed, and there is no need for powder packaging and transportation in between, which can avoid dust pollution.

[0049] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0050] Example 1

[0051] Talc ore with a whiteness of 92% and a silicon content of 65% was coarsely crushed and ground to obtain 1000-mesh talc powder. The talc powder was mixed with coconut oil at a temperature of 40℃ and an addition amount of 0.8wt% (based on talc powder), and stirred evenly at a speed of 3000 r / min to obtain modified talc powder. Wollastonite ore with a whiteness of 92% and a silicon dioxide content of 54% was coarsely crushed and ground to obtain 600-mesh wollastonite powder. The wollastonite powder was mixed with coconut oil at a temperature of 40℃ and an addition amount of 0.8wt% (based on wollastonite powder), and stirred evenly at a speed of 3000 r / min to obtain modified wollastonite powder.

[0052] 50 parts of polylactic acid resin with a number average molecular weight of 100,000, 30 parts of modified talc, 14 parts of modified wollastonite, 1 part of butylated hydroxyanisole, 2 parts of stearic acid, and 3 parts of glyceryl stearate were added to a high-speed mixer and mixed at 1000 r / min for 5 min. The resulting mixture at 120°C was then fed into a twin-screw extruder with a speed of 700 r / min, a feed speed of 50 r / min, and a die head temperature of 180°C (the temperatures of the 10 working zones of the twin-screw extruder are: Zone 1 175°C, Zone 2 175°C, Zone 3 175°C, Zone 4 175°C, Zone 5 175°C, Zone 6 180°C, Zone 7 180°C, Zone 8 185°C, Zone 9 180°C, and Zone 10 180°C). The mixture was then pelletized using a hydrothermal ring cutting process to obtain talc-wollastonite masterbatch with a length of 3 mm.

[0053] Example 2

[0054] Talc ore with a whiteness of 93% and a silicon content of 67% was coarsely crushed and ground to obtain 1000-mesh talc powder. The talc powder was mixed with coconut oil at a temperature of 60℃ and an addition amount of 1wt% (based on talc powder), and stirred evenly at a speed of 3600 r / min to obtain modified talc powder. Wollastonite ore with a whiteness of 93% and a silicon dioxide content of 56% was coarsely crushed and ground to obtain 800-mesh wollastonite powder. The wollastonite powder was mixed with coconut oil at a temperature of 60℃ and an addition amount of 1wt% (based on wollastonite powder), and stirred evenly at a speed of 3600 r / min to obtain modified wollastonite powder.

[0055] 50 parts of polylactic acid resin with a number average molecular weight of 150,000, 30 parts of modified talc, 14 parts of modified wollastonite, 1 part of butylated hydroxyanisole, 2 parts of stearic acid, and 3 parts of PE wax were added to a high-speed mixer and mixed at 1100 r / min for 8 min. The resulting mixture at 130°C was then fed into a twin-screw extruder with a speed of 650 r / min, a feed speed of 45 r / min, and a die head temperature of 190°C (the temperatures of the 10 working zones of the twin-screw extruder were: Zone 1 175°C, Zone 2 175°C, Zone 3 175°C, Zone 4 175°C, Zone 5 175°C, Zone 6 180°C, Zone 7 180°C, Zone 8 185°C, Zone 9 180°C, and Zone 10 180°C). The mixture was then pelletized using a hydrothermal ring cutting process to obtain talc-wollastonite masterbatch with a length of 5 mm.

[0056] Example 3

[0057] Talc ore with a whiteness of 92% and a silicon content of 65% was coarsely crushed and ground to obtain 1500-mesh talc powder. The talc powder was mixed with coconut oil at a temperature of 50℃ and an addition amount of 0.8wt% (based on talc powder), and stirred evenly at a speed of 3000 r / min to obtain modified talc powder. Wollastonite ore with a whiteness of 92% and a silicon dioxide content of 55% was coarsely crushed and ground to obtain 800-mesh wollastonite powder. The wollastonite powder was mixed with coconut oil at a temperature of 50℃ and an addition amount of 0.8wt% (based on wollastonite powder), and stirred evenly at a speed of 3000 r / min to obtain modified wollastonite powder.

[0058] 55 parts of polylactic acid resin with a number average molecular weight of 150,000, 35 parts of modified talc, 16 parts of modified wollastonite, 2 parts of tert-butyl-4-hydroxyanisole, 4 parts of stearic acid, and 4 parts of calcium stearate were added to a high-speed mixer and mixed at 1200 r / min for 5 min. The resulting mixture at 120℃ was then fed into a twin-screw extruder with a speed of 750 r / min, a feed speed of 50 r / min, and a die head temperature of 180℃ (the temperatures of the 10 working zones of the twin-screw extruder are: Zone 1 170℃, Zone 2 173℃, Zone 3 175℃, Zone 4 175℃, Zone 5 178℃, Zone 6 180℃, Zone 7 180℃, Zone 8 185℃, Zone 9 180℃, and Zone 10 180℃). The mixture was then pelletized using a hydrothermal ring cutting process to obtain talc-wollastonite masterbatch with a length of 3 mm.

[0059] Comparative Example 1

[0060] Talc ore with a whiteness of 92% and a silicon content of 65% was coarsely crushed and ground to obtain 1250-mesh talc powder; wollastonite ore with a whiteness of 92% and a silicon dioxide content of 54% was coarsely crushed and ground to obtain 600-mesh wollastonite powder.

[0061] 50 parts of polylactic acid resin with a number average molecular weight of 100,000, 30 parts of talc, 14 parts of wollastonite, 1 part of butylated hydroxyanisole, 2 parts of stearic acid, and 3 parts of glyceryl stearate were added to a high-speed mixer and mixed at 1000 r / min for 5 min. The resulting mixture at 120°C was then fed into a twin-screw extruder with a speed of 700 r / min, a feed speed of 50 r / min, and a die head temperature of 180°C (the temperatures of the 10 working zones of the twin-screw extruder are: Zone 1 175°C, Zone 2 175°C, Zone 3 175°C, Zone 4 175°C, Zone 5 175°C, Zone 6 180°C, Zone 7 180°C, Zone 8 185°C, Zone 9 180°C, and Zone 10 180°C). The mixture was then pelletized using a hydrothermal ring cutting process to obtain talc-wollastonite masterbatch with a length of 3 mm.

[0062] Comparative Example 2

[0063] Talc ore with a whiteness of 92% and a silicon content of 65% was coarsely crushed and ground to obtain 1250 mesh talc powder. The talc powder was mixed with coconut oil at a temperature of 40℃ and an addition amount of 1wt% (based on talc powder). The mixture was stirred evenly at a speed of 3000r / min to obtain modified talc powder.

[0064] 50 parts of polylactic acid resin with a number average molecular weight of 100,000, 44 parts of modified talc, 1 part of butylated hydroxyanisole, 2 parts of stearic acid, and 3 parts of glyceryl stearate were added to a high-speed mixer and mixed at 1200 r / min for 5 min. The resulting mixture at 120℃ was then fed into a twin-screw extruder with a speed of 700 r / min, a feed speed of 50 r / min, and a die head temperature of 180℃ (the temperatures of the 10 working zones of the twin-screw extruder are: Zone 1 175℃, Zone 2 175℃, Zone 3 175℃, Zone 4 175℃, Zone 5 175℃, Zone 6 180℃, Zone 7 180℃, Zone 8 185℃, Zone 9 180℃, and Zone 10 180℃). The mixture was then pelletized using a hydrothermal ring cutting process to obtain talc masterbatch with a length of 3 mm.

[0065] The masterbatches obtained from Examples 1-2 and Comparative Examples 1-2 were used to produce disposable biodegradable lunch boxes. A chemical foaming injection molding process was employed. The masterbatches and 0.8 wt% of a composite modified foaming agent (mass ratio AC180:ZnO:Zn(St)2 = 6:1:1) were mixed evenly and added to an injection molding machine. The operating parameters of the injection molding machine were: injection volume 102g, injection speed 65cm. 3 / sec, with an injection pressure of 160MPa, injection molded specimens of the same specifications were obtained. The tensile and flexural properties of the specimens were tested according to national standards GB / T1040.1-2006 and GB / T9341-2008, respectively. Table 1 shows the test results of various properties of the injection molded specimens produced from the masterbatches obtained in Examples 1-2 and Comparative Examples 1-2.

[0066] Table 1. Performance test results of samples obtained from the production of masterbatches in Examples 1-2 and Comparative Examples 1-2.

[0067]

[0068] As shown in Table 1, the tensile and flexural strengths of the samples in Comparative Example 1 are lower than those in Examples 1 and 2, indicating that the mechanical properties of the lunchbox can be improved after modification with talc and wollastonite powder. The tensile and flexural strengths of the samples in Comparative Example 1 are higher than those in Comparative Example 2, indicating that the addition of wollastonite can improve the mechanical properties of the lunchbox. From the perspective of density, Comparative Examples 1-2 are higher than those in Examples 1-2. The use of wollastonite with a high aspect ratio and needle-like structure in combination with flake talc can construct a loose network structure. For the production of a fixed quantity of lunchboxes, the density of the lunchbox is reduced while the thickness is increased, which further increases the strength of the lunchbox.

[0069] As can be seen from the above embodiments, the present invention provides a talc-wollastonite masterbatch and its preparation method. The talc-wollastonite masterbatch of the present invention can be used to prepare disposable plastic products, and the resulting injection-molded samples have superior mechanical properties. When applied to the production of disposable lunch boxes, the talc-wollastonite masterbatch of the present invention is biodegradable, achieving dust-free production. While ensuring that the weight of the lunch box meets the standards, it improves the mechanical properties of the lunch box, solving the technical problems of poor environmental friendliness and insufficient mechanical properties in the production of biodegradable plastic products in the prior art.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A talc-wollastonite masterbatch, characterized by, Consists of the following components by mass fraction: polylactic acid 45-55 parts, modified talc powder 25-35 parts, modified wollastonite powder 12-16 parts, antioxidant 0.5-2 parts, stearic acid 2-4 parts, lubricant 2-4 parts; The modified talc powder is obtained by mixing talc powder and coconut oil, and the modified wollastonite is obtained by mixing wollastonite powder and coconut oil; The particle size of the talc powder is 1000-1500 mesh, and the addition amount of coconut oil is 0.8-1% of the mass of the talc powder; The particle size of the wollastonite powder is 600-800 mesh, and the addition amount of coconut oil is 0.8-1% of the mass of the wollastonite powder; The preparation method of the talc-wollastonite master batch comprises the following steps: Step 1): talc ore is crushed to obtain talc powder, which is then mixed with coconut oil to obtain modified talc powder; wollastonite ore is crushed to obtain wollastonite powder, which is then mixed with coconut oil to obtain modified wollastonite powder; Step 2): mix the modified talc powder, the modified wollastonite powder, the polylactic acid, the antioxidant, the stearic acid and the lubricant, and the obtained mixture is extruded and granulated to obtain the talc-wollastonite master batch.

2. A talc-wollastonite masterbatch according to claim 1, characterized in that, The number average molecular weight of the polylactic acid is 100-150 thousand.

3. A talc-wollastonite masterbatch according to claim 1 or 2, characterised in that, The antioxidant includes one or more of butylated hydroxyanisole, tertiary butyl-4-hydroxyanisole and beta-(3,5-di-tert-butyl-4-hydroxyphenyl) octadecyl propionate; The lubricant includes one or more of calcium stearate, glycerol stearate and PE wax.

4. The method for producing the talc-wollastonite master batch according to claim 2 or 3, characterized by, The method comprises the following steps: Step 1): talc ore is crushed to obtain talc powder, which is then mixed with coconut oil to obtain modified talc powder; wollastonite ore is crushed to obtain wollastonite powder, which is then mixed with coconut oil to obtain modified wollastonite powder; Step 2): mix the modified talc powder, the modified wollastonite powder, the polylactic acid, the antioxidant, the stearic acid and the lubricant, and the obtained mixture is extruded and granulated to obtain the talc-wollastonite master batch.

5. The method of claim 4, wherein the talc-wollastonite masterbatch is prepared by mixing talc and wollastonite in a weight ratio of 1 : 1 to 1 :

3. In step 1), the mixing of the talc powder and the coconut oil is carried out under stirring, and the stirring speed is 3000-3600 r / min.

6. The method of claim 4, wherein the talc-wollastonite masterbatch is prepared by mixing talc and wollastonite in a weight ratio of 1 : 1 to 1 :

3. In step 1), the mixing of the talc powder and the coconut oil is carried out under stirring, and the stirring speed is 3000-3600 r / min.

7. The method of preparing talc-wollastonite master granules according to claim 5 or 6, characterized in that, In step 2), the mixing is carried out under stirring, and the stirring speed is 1000-1200 r / min, and the stirring time is 3-8 min; The temperature of the mixture is 120-130℃; The extrusion is carried out in an extruder, and the speed of the extruder is 650-750 r / min, and the feeding speed is 45-50 r / min; The extruder comprises 10 working sections, wherein the temperature of the 10 working sections is independently 170-185℃, and the head temperature is 180-190℃.

8. The method of claim 7, wherein the talc-wollastonite masterbatch is prepared by a process comprising the steps of: In step 2), the granulation adopts a water ring hot cutting process, and the length of the obtained master batch is 3-5 mm.

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