Method for preparing antibacterial and antiseptic food packaging material

Abstract

The present invention relates to the technical field of packaging materials, and discloses a preparation method of an antibacterial and antiseptic food packaging material, the antibacterial and antiseptic food packaging material includes 100 parts by weight of polyvinyl alcohol, 2-15 parts by weight of cross-linked β-cyclodextrin inclusion thyme oil, and 1-1.5 parts by weight of propylene glycol. The hyperbranched polymer cross-linked β-cyclodextrin of the present invention contains a three-dimensional hyperbranched dendritic molecular chain, has a higher inclusion amount for thyme oil, thereby including more active ingredients such as thymol and carvacrol, and is added to the polyvinyl alcohol film packaging material, significantly improving the antibacterial and antiseptic properties of the packaging material. The hyperbranched polymer cross-linked β-cyclodextrin contains a flexible polyether hyperbranched molecular chain, which has a certain toughening effect on polyvinyl alcohol, and is conducive to improving the elongation at break and the toughness of the polyvinyl alcohol film packaging material.

Description

Technical Field

[0001] The invention relates to the technical field of packaging materials, in particular to a method for preparing an antibacterial and antiseptic food packaging material. Background Art

[0002] Polyvinyl alcohol (PVA) is non-toxic, biodegradable, has excellent film-forming properties, and boasts superior mechanical properties. It is widely used in packaging materials, adhesives, pharmaceuticals, and textile printing and dyeing. To enhance the antimicrobial properties of PVA and expand its practical application in food packaging, it is often necessary to add antimicrobial agents, such as natural and inorganic antimicrobials, to the PVA film.

[0003] Thyme oil, an essential oil extracted from thyme, contains significant amounts of thymol, carvacrol, and eucalyptol. It possesses strong antimicrobial properties, exhibiting excellent inhibitory and antibacterial activity against bacteria and fungi, including Escherichia coli and Staphylococcus aureus. This has led to its widespread application in food packaging films and plastic wrap. For example, the paper "Preparation and Antimicrobial Activity of PLA / PBAT / Essential Oil Active Packaging Materials" describes the use of thyme oil and lemon essential oil as raw materials to improve the UV resistance and antibacterial properties of PLA / PBAT films, demonstrating their potential as active packaging materials. β-cyclodextrin, with its unique hydrophobic cavity structure, exhibits excellent inclusion properties for compounds such as drugs and essential oils. Increasing the amount of β-cyclodextrin encapsulating plant essential oils and expanding its practical application in antimicrobial and antiseptic packaging films is a hot topic. Summary of the Invention

[0004] (1) Technical problem to be solved: The present invention provides an antibacterial and antiseptic food packaging material with good mechanical properties and excellent antibacterial properties.

[0005] (II) Technical Solution: A method for preparing an antibacterial and antiseptic food packaging material:

[0006] (1) Add 100 parts by weight of glycerol glycidyl ether to a solvent, and dropwise add a solution containing 50-68 parts by weight of N,N'-dimethyldiamine compound while stirring. After stirring for reaction, remove the solvent by vacuum distillation, wash with ethanol, and dry to obtain a hydroxy hyperbranched polymer. The reaction formula is:

[0007] .

[0008] (2) Add 100 parts by weight of hydroxy hyperbranched polymer and 200-500 parts by weight of β-cyclodextrin to N,N-dimethylformamide solvent, stir, then dropwise add 30-80 parts by weight of diisocyanate compound, stir and react in nitrogen atmosphere, filter, wash with ethanol, and dry to obtain hyperbranched polymer cross-linked β-cyclodextrin.

[0009] (3) Add 25-60 parts by weight of thyme oil to ethanol, stir, then add water and 100 parts by weight of hyperbranched polymer cross-linked β-cyclodextrin, stir for inclusion, filter, refrigerate the product, then wash with water and ethanol in sequence, and dry to obtain cross-linked β-cyclodextrin inclusion thyme oil.

[0010] (4) Add 100 parts by weight of polyvinyl alcohol to water, heat and stir to dissolve, then add 2-15 parts by weight of cross-linked β-cyclodextrin-encapsulated thyme oil and 1-1.5 parts by weight of propylene glycol, stir and vacuum degas, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0011] Preferably, the solvent in (1) is tetrahydrofuran or 1,4-dioxane.

[0012] Preferably, in (1), the time for adding the solution of the N,N'-dimethyldiamine compound dropwise is controlled to be 2-3 hours, the temperature during the stirring reaction is 40-50°C, and the reaction time is 2-4 hours.

[0013] Preferably, the N,N'-dimethyldiamine compound is N,N'-dimethylethylenediamine, N,N'-dimethyl-1,3-propylenediamine or N,N'-dimethyl-1,4-butanediamine.

[0014] Preferably, the diisocyanate compound is hexamethylene diisocyanate or isophorone diisocyanate.

[0015] Preferably, the temperature during the stirring reaction in (2) is 75-85° C., and the reaction time is 2-4 h.

[0016] Preferably, the temperature during the inclusion in (3) is 40-55°C and the time is 3-6 hours.

[0017] (3) Technical effect of the present invention: A ring-opening polymerization reaction is carried out using propylene glycol glycidyl ether and N,N'-dimethyldiamine compound to obtain a dendritic hydroxyl hyperbranched polymer, which is then cross-linked with β-cyclodextrin and a cross-linking agent diisocyanate compound. The obtained hyperbranched polymer cross-linked β-cyclodextrin contains a three-dimensional hyperbranched dendritic molecular chain. At the same time, the side chain of the hydroxyl hyperbranched polymer contains a large number of hydroxyl groups. Hydroxyl groups are introduced into the hyperbranched polymer cross-linked β-cyclodextrin, forming hydrogen bond interactions with the hydroxyl groups of active ingredients such as thymol and carvacrol in thyme oil, so that the cross-linked β-cyclodextrin contains more active ingredients such as thymol and carvacrol. Antibacterial components, such as thymol and carvacrol, are included in the cross-linked β-cyclodextrin. When added to the polyvinyl alcohol film packaging material, the antibacterial and antiseptic properties of the packaging material are significantly improved.

[0018] The invention adds a hyperbranched polymer cross-linked β-cyclodextrin to polyvinyl alcohol. The cross-linked β-cyclodextrin contains flexible polyether hyperbranched molecular chains, which have a certain toughening effect on the polyvinyl alcohol film, thereby improving the elongation at break and toughness of the polyvinyl alcohol film packaging material. The resulting polyvinyl alcohol film packaging material has excellent practical applications in food packaging, preservation, and antiseptic properties. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] The polyvinyl alcohol model 1788 in the embodiments of the present invention was purchased from Xi'an Tianzheng Pharmaceutical Excipients Co., Ltd. Thyme oil was purchased from Hubei Xinghengye Technology Co., Ltd.

[0021] Example 1:

[0022] (1) Add 5 g of glycerol glycidyl ether to 40 mL of tetrahydrofuran solvent, heat to 40 ° C, and add 40 mL of tetrahydrofuran solution containing 2.5 g of N, N'-dimethylethylenediamine dropwise while stirring. Control the addition time to 3 h. After the addition is completed, continue stirring and react for 3 h. Remove the solvent by distillation under reduced pressure, wash with ethanol, and dry to obtain a hydroxyl hyperbranched polymer.

[0023] (2) Add 2 g of hydroxy hyperbranched polymer and 4 g of β-cyclodextrin to 80 mL of N,N-dimethylformamide solvent, stir and then add 0.6 g of hexamethylene diisocyanate dropwise. Heat to 80 °C in a nitrogen atmosphere, stir and react for 2 h, filter, wash with ethanol, and dry to obtain hyperbranched polymer cross-linked β-cyclodextrin.

[0024] (3) Add 2.5 g of thyme oil to 30 mL of ethanol, stir, then add 50 mL of water and 10 g of hyperbranched polymer cross-linked β-cyclodextrin. Heat to 55°C and stir for 3 h. Filter and refrigerate the product at 4°C for 24 h. Then wash with water and ethanol in sequence and dry to obtain cross-linked β-cyclodextrin-encapsulated thyme oil. Weigh and calculate the inclusion amount W of thyme oil. W = (m1-m2) / m2. m1 is the mass of cross-linked β-cyclodextrin-encapsulated thyme oil, and m2 is the amount of hyperbranched polymer cross-linked β-cyclodextrin used.

[0025] (4) Add 100g of polyvinyl alcohol to 800mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 2g of cross-linked β-cyclodextrin-encapsulated thyme oil and 1.5g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0026] Example 2:

[0027] (1) Add 5 g of propylene glycol glycidyl ether to 40 mL of 1,4-dioxane solvent, heat to 40 °C, and add 40 mL of 1,4-dioxane solution containing 3.4 g of N,N'-dimethyl-1,4-butanediamine dropwise while stirring. Control the addition time to 3 h. After the addition is complete, continue stirring and react for 4 h. Remove the solvent by distillation under reduced pressure, wash with ethanol, and dry to obtain a hydroxyl hyperbranched polymer.

[0028] (2) Add 2 g of hydroxy hyperbranched polymer and 6 g of β-cyclodextrin to 100 mL of N,N-dimethylformamide solvent, stir and then add 0.9 g of hexamethylene diisocyanate dropwise. Heat to 75 °C in a nitrogen atmosphere, stir and react for 4 h, filter, wash with ethanol, and dry to obtain hyperbranched polymer cross-linked β-cyclodextrin.

[0029] (3) Add 3.5 g of thyme oil to 30 mL of ethanol, stir, then add 80 mL of water and 10 g of hyperbranched polymer cross-linked β-cyclodextrin. Heat to 40°C and stir for 6 h. Filter and refrigerate the product at 4°C for 24 h. Then wash with water and ethanol in sequence and dry to obtain cross-linked β-cyclodextrin-encapsulated thyme oil. Weigh and calculate the inclusion amount W of thyme oil. W = (m1-m2) / m2. m1 is the mass of cross-linked β-cyclodextrin-encapsulated thyme oil, and m2 is the amount of hyperbranched polymer cross-linked β-cyclodextrin used.

[0030] (4) Add 100g of polyvinyl alcohol to 900mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 6g of cross-linked β-cyclodextrin-encapsulated thyme oil and 1g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0031] Example 3:

[0032] (1) Add 5 g of propylene glycol glycidyl ether to 40 mL of 1,4-dioxane solvent, heat to 50 °C, and add 50 mL of 1,4-dioxane solution containing 2.5 g of N,N'-dimethylethylenediamine dropwise while stirring. The addition time is controlled to 2 h. After the addition is completed, continue stirring and react for 2 h. Remove the solvent by distillation under reduced pressure, wash with ethanol, and dry to obtain a hydroxyl hyperbranched polymer.

[0033] (2) Add 2 g of hydroxy hyperbranched polymer and 8 g of β-cyclodextrin to 120 mL of N,N-dimethylformamide solvent, stir, and then add 1.3 g of isophorone diisocyanate dropwise. Heat to 85 °C in a nitrogen atmosphere, stir and react for 3 h, filter, wash with ethanol, and dry to obtain hyperbranched polymer cross-linked β-cyclodextrin.

[0034] (3) Add 4.8 g of thyme oil to 30 mL of ethanol, stir, then add 60 mL of water and 10 g of hyperbranched polymer cross-linked β-cyclodextrin. Heat to 45°C and stir for inclusion for 5 h. Filter and refrigerate the product at 4°C for 24 h. Then wash with water and ethanol in sequence and dry to obtain cross-linked β-cyclodextrin-encapsulated thyme oil. Weigh and calculate the inclusion amount W of thyme oil. W = (m1-m2) / m2. m1 is the mass of cross-linked β-cyclodextrin-encapsulated thyme oil, and m2 is the amount of hyperbranched polymer cross-linked β-cyclodextrin used.

[0035] (4) Add 100g of polyvinyl alcohol to 900mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 10g of cross-linked β-cyclodextrin-encapsulated thyme oil and 1g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0036] Example 4:

[0037] (1) Add 5 g of glycerol glycidyl ether to 50 mL of tetrahydrofuran solvent, heat to 45 ° C, and add 50 mL of tetrahydrofuran solution containing 2.9 g of N, N'-dimethyl-1,3-propylenediamine dropwise while stirring. The addition time is controlled to 3 h. After the addition is completed, continue stirring and react for 4 h. Remove the solvent by distillation under reduced pressure, wash with ethanol, and dry to obtain a hydroxyl hyperbranched polymer.

[0038] (2) Add 2 g of hydroxy hyperbranched polymer and 10 g of β-cyclodextrin to 150 mL of N,N-dimethylformamide solvent, stir and then add 1.6 g of hexamethylene diisocyanate dropwise. Heat to 80 °C in a nitrogen atmosphere, stir and react for 4 h, filter, wash with ethanol, and dry to obtain hyperbranched polymer cross-linked β-cyclodextrin.

[0039] (3) Add 6 g of thyme oil to 30 mL of ethanol, stir, then add 80 mL of water and 10 g of hyperbranched polymer cross-linked β-cyclodextrin. Heat to 55°C and stir for 6 h. Filter and refrigerate the product at 4°C for 24 h. Then wash with water and ethanol in sequence and dry to obtain cross-linked β-cyclodextrin-encapsulated thyme oil. Weigh and calculate the inclusion amount W of thyme oil. W = (m1-m2) / m2. m1 is the mass of cross-linked β-cyclodextrin-encapsulated thyme oil, and m2 is the amount of hyperbranched polymer cross-linked β-cyclodextrin used.

[0040] (4) Add 100g of polyvinyl alcohol to 900mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 15g of cross-linked β-cyclodextrin-encapsulated thyme oil and 1.5g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0041] Comparative Example 1:

[0042] (1) Add 100g of polyvinyl alcohol to 800mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 1.5g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry into a film to obtain food packaging material.

[0043] Comparative Example 2:

[0044] (1) Add 5 g of ethylene glycol diglycidyl ether to 40 mL of tetrahydrofuran solvent, heat to 40 ° C, and add 40 mL of tetrahydrofuran solution containing 2.5 g of N, N'-dimethylethylenediamine while stirring. The addition time is controlled to 3 h. After the addition is completed, continue stirring and react for 3 h. Remove the solvent by distillation under reduced pressure, wash with ethanol, and dry to obtain a hydroxyl polymer.

[0045] (2) Add 2 g of hydroxy polymer and 4 g of β-cyclodextrin to 80 mL of N,N-dimethylformamide solvent, stir, and then dropwise add 0.6 g of hexamethylene diisocyanate. Heat to 80 °C in a nitrogen atmosphere, stir and react for 2 h, filter, wash with ethanol, and dry to obtain cross-linked β-cyclodextrin.

[0046] (3) Add 2.5 g of thyme oil to 30 mL of ethanol, stir, then add 50 mL of water and 10 g of cross-linked β-cyclodextrin. Heat to 55°C and stir for 3 h. Filter and refrigerate the product at 4°C for 24 h. Then wash with water and ethanol in sequence and dry to obtain cross-linked β-cyclodextrin-encapsulated thyme oil. Weigh the product and calculate the encapsulation amount W of thyme oil. W = (m1 - m2) / m2. m1 is the mass of cross-linked β-cyclodextrin-encapsulated thyme oil, and m2 is the amount of cross-linked β-cyclodextrin used.

[0047] (4) Add 100g of polyvinyl alcohol to 800mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 2g of cross-linked β-cyclodextrin-encapsulated thyme oil and 1.5g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0048] Comparative Example 3:

[0049] (1) Add 4 g of β-cyclodextrin to 80 mL of N,N-dimethylformamide solvent, stir, and then dropwise add 0.6 g of hexamethylene diisocyanate. Heat to 80 °C in a nitrogen atmosphere, stir and react for 2 h, filter, wash with ethanol, and dry to obtain cross-linked β-cyclodextrin.

[0050] (2) Add 2.5 g of thyme oil to 30 mL of ethanol, stir, then add 50 mL of water and 10 g of cross-linked β-cyclodextrin. Heat to 55°C and stir for 3 h. Filter and refrigerate the product at 4°C for 24 h. Then wash with water and ethanol in sequence and dry to obtain cross-linked β-cyclodextrin-encapsulated thyme oil. Weigh the product and calculate the encapsulation amount W of thyme oil. W = (m1 - m2) / m2. m1 is the mass of cross-linked β-cyclodextrin-encapsulated thyme oil, and m2 is the amount of cross-linked β-cyclodextrin used.

[0051] (3) Add 100g of polyvinyl alcohol to 800mL of water, heat to 95℃, stir to dissolve, cool to 60℃, then add 2g of cross-linked β-cyclodextrin-encapsulated thyme oil and 1.5g of propylene glycol, stir and degas in vacuum, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

[0052] Table 1

[0053]

[0054] The antibacterial properties of packaging materials were tested using the oscillation method. The test bacteria were Escherichia coli, Staphylococcus aureus, and Candida albicans.

[0055] Take 10mL of concentration 10 5 An activated bacterial suspension containing 100 cfu / mL of activated bacteria was added to a sterile test tube. The packaging material sample was then added, with the packaging material from Comparative Example 1 serving as a blank control. The suspension was shaken in a constant-temperature incubator at 37°C for 24 hours at a rate of 200 rpm. The bacterial suspension was then diluted 10-fold with PBS buffer. 1 mL of the diluted suspension was transferred to an agar medium and incubated in a constant-temperature incubator at 37°C for 24 hours. Colony counts were performed after incubation. Each sample was tested three times, and the average value was taken. The antibacterial rate, Q, was calculated.

[0056] Q = (BC) / B × 100%. B is the number of colonies in the blank group after incubation. C is the number of colonies in the experimental group after incubation.

[0057] Table 2

[0058]

[0059] With reference to ISO527-3-2018, a universal material testing machine was used to test the tensile properties of packaging materials. The sample size was 100 mm × 10 mm, the clamp distance was 50 mm, and the tensile rate was 5 mm / min.

[0060] Table 3

[0061]

[0062] After testing, it was found that the hyperbranched polymer cross-linked β-cyclodextrin prepared in each embodiment using hydroxyl hyperbranched polymer, β-cyclodextrin, and diisocyanate compound as raw materials has a higher inclusion capacity for thyme oil. This is because the hydroxyl hyperbranched polymer contains a three-dimensional hyperbranched dendritic molecular chain, which generates a three-dimensional spatial cross-linked network structure after cross-linking reaction with β-cyclodextrin and diisocyanate, and has a higher inclusion capacity for thyme oil. At the same time, the side chain of the hydroxyl hyperbranched polymer contains a large number of hydroxyl groups. The hydroxyl groups are introduced into the hyperbranched polymer cross-linked β-cyclodextrin, forming hydrogen bond interactions with active ingredients such as thymol and carvacrol in thyme oil, so that the cross-linked β-cyclodextrin includes more active ingredients and antibacterial components such as thymol and carvacrol. When added to the polyvinyl alcohol film packaging material, the antibacterial and antiseptic properties of the packaging material are significantly improved. In addition, adding an appropriate amount of hyperbranched polymer cross-linked β-cyclodextrin can improve the elongation at break of the packaging material to a certain extent. This may be because the hyperbranched polymer cross-linked β-cyclodextrin contains flexible polyether hyperbranched molecular chains, which have a certain toughening effect on polyvinyl alcohol, which is beneficial to improving the elongation at break and toughness.

[0063] In Comparative Example 2, ethylene glycol diglycidyl ether and N,N'-dimethylethylenediamine were reacted to obtain a hydroxyl polymer that was a linear molecular chain and did not contain a three-dimensional hyperbranched dendritic molecular chain. In Comparative Example 3, cross-linked β-cyclodextrin was prepared without adding a hydroxyl hyperbranched polymer. The cross-linked cyclodextrin obtained did not form a good three-dimensional cross-linked network structure, and the inclusion amount of thyme oil was low, resulting in poor antibacterial properties of the polyvinyl alcohol film packaging material.

Claims

1. A method for preparing an antibacterial and antiseptic food packaging material, characterized in that: The preparation method is: (1) Add glycerol glycidyl ether to the solvent, add dropwise a solution containing N,N'-dimethyldiamine compound while stirring, stir and react, distill under reduced pressure, wash, and dry to obtain a hydroxy hyperbranched polymer; (2) Adding a hydroxy hyperbranched polymer and β-cyclodextrin to an N,N-dimethylformamide solvent, adding a diisocyanate compound dropwise after stirring, stirring and reacting in a nitrogen atmosphere, filtering, washing, and drying to obtain a hyperbranched polymer cross-linked β-cyclodextrin; (3) adding thyme oil to ethanol, stirring and then adding water, cross-linking the hyperbranched polymer with β-cyclodextrin, stirring for inclusion, filtering, refrigerating the product at low temperature, washing, and drying to obtain cross-linked β-cyclodextrin inclusion thyme oil; (4) Add 100 parts by weight of polyvinyl alcohol to water, heat and stir to dissolve, then add 2-15 parts by weight of cross-linked β-cyclodextrin-encapsulated thyme oil and 1-1.5 parts by weight of propylene glycol, stir and vacuum degas, pour the solution into a mold, cast and dry to form a film, and obtain an antibacterial and antiseptic food packaging material.

2. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: The solvent in (1) is tetrahydrofuran or 1,4-dioxane.

3. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: The amount of glycerol glycidyl ether used in (1) is 100 parts by weight, and the amount of N,N'-dimethyldiamine compound is 50-68 parts by weight.

4. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: In the step (1), the time for dripping the solution of the N,N'-dimethyldiamine compound is controlled to be 2-3 hours, the temperature during the stirring reaction is 40-50°C, and the reaction time is 2-4 hours.

5. The method for preparing the antibacterial and antiseptic food packaging material according to claim 4, characterized in that: The N,N'-dimethyldiamine compound is N,N'-dimethylethylenediamine, N,N'-dimethyl-1,3-propylenediamine or N,N'-dimethyl-1,4-butanediamine.

6. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: The amount of the hydroxy hyperbranched polymer in (2) is 100 parts by weight, the amount of β-cyclodextrin is 200-500 parts by weight, and the amount of the diisocyanate compound is 30-80 parts by weight.

7. The method for preparing the antibacterial and antiseptic food packaging material according to claim 6, characterized in that: The diisocyanate compound is hexamethylene diisocyanate or isophorone diisocyanate.

8. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: The temperature during the stirring reaction in (2) is 75-85°C, and the reaction time is 2-4 hours.

9. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: The temperature during the inclusion in step (3) is 40-55°C and the time is 3-6 hours.

10. The method for preparing the antibacterial and antiseptic food packaging material according to claim 1, characterized in that: The hyperbranched polymer cross-linked β-cyclodextrin in (3) is 100 parts by weight, and the amount of thyme oil is 25-60 parts by weight.

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