Injection molding feedstock of stainless steel powder modified by anionic and cationic surfactants and preparation method thereof

Abstract

The present invention relates to an injection molding feedstock and a preparation method for cationic and anionic surfactant-modified stainless steel powder, belonging to the technical field of metal powder injection molding. The injection molding feedstock is prepared by kneading cationic surfactant-modified stainless steel powder, anionic surfactant-modified stainless steel powder, a skeleton polymer, and polyethylene glycol. The density of the green compact prepared from the injection molding feedstock is 5.30 - 5.49 g / cm<supgt;3< / supgt>, and the flexural modulus is 2480 - 2950 MPa. The operation steps for preparing the injection molding feedstock are as follows: (1) modifying stainless steel powder with a cationic surfactant; (2) modifying stainless steel powder with an anionic surfactant; (3) kneading the two kinds of stainless steel powders modified with cationic and anionic surfactants prepared in steps (1) and (2), polymethyl methacrylate, and polyethylene glycol in a kneader to obtain the injection molding feedstock of the present invention. In the present invention, each component cooperates with each other to achieve the purpose of improving the properties of the green compact on the premise of ensuring good fluidity of the feedstock.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal powder injection molding, and particularly relates to a metal injection molding feedstock composed of stainless steel powder modified with cationic and anionic surfactants and a polymer binder, and a preparation method thereof. Background Art

[0002] Metal Injection Molding (MIM) is a new type of near-net shape forming technology of powder metallurgy formed by introducing modern plastic injection molding technology into the field of powder metallurgy. Metal Injection Molding (MIM) not only has the advantages of fewer process steps, no cutting or less cutting, and high economic benefits in the conventional powder metallurgy process. At the same time, it overcomes the main disadvantages of uneven material quality, low mechanical properties, difficulty in forming thin walls, and complex structures in the traditional powder metallurgy process. It is suitable for mass production of small, precision, three-dimensional shape complex and metal parts with special requirements. Metal Injection Molding (MIM) technology has been widely applied in the fields of consumer electronics, automobiles, medical devices, etc.

[0003] Nowadays, Metal Injection Molding (MIM) mainly focuses on the following research directions: studying the influence of the interaction between modified powder and binder on injection molding; the influence of the particle size and shape of metal powder on injection molding; studying the influence of the viscosity and ratio of the binder on injection molding; however, the application of the interaction between metal powders in metal injection molding is less studied. In metal injection molding, common problems such as poor compatibility between powder and binder, high feedstock viscosity, and low powder loading result in low green body strength, showing voids, bubbles, and even serious cracks and collapses after debinding, making it impossible to meet the precision and shape retention performance requirements of the parts. Therefore, studying the surface modification of stainless steel powder with anionic and cationic surfactants and exploring the application of the electrostatic interaction between the modified powders in metal injection molding have a positive impact on metal injection molding. Summary of the Invention

[0004] To solve the common problems of poor compatibility between powder and binder and low green body strength in metal injection molding, the present invention provides an injection molding feedstock of stainless steel powder modified with cationic and anionic surfactants, and also provides a preparation method for the injection molding feedstock.

[0005] An injection molding feedstock of stainless steel powder modified with cationic and anionic surfactants is made by mixing 115.5 - 120.3 g of stainless steel powder modified with cationic surfactant, 115.5 - 120.3 g of stainless steel powder modified with anionic surfactant, 13.4 - 15.1 g of the skeleton polymer polymethyl methacrylate, and 5.3 - 6.1 g of polyethylene glycol through mixing and kneading.

[0006] The injection molding feed material has a melt index of 34.0 to 40.9 g / 10 min under the test conditions of a temperature of 190° C. and a load of 2.16 kg. The density of the green body prepared using the injection molding feed material is 5.30 to 5.49 g / cm 3 , the flexural modulus is 2480~2950MPa.

[0007] The preparation steps of an injection molding feedstock for anionic and cationic surfactant-modified stainless steel powder are as follows:

[0008] (1) Preparation of cationic surfactant-modified stainless steel powder

[0009] (1.1) Stir 32 g of a cationic surfactant and 150 ml of ethanol thoroughly until dissolved to obtain a cationic surfactant solution.

[0010] (1.2) 8 kg of stainless steel powder was added to a high-speed mixer. When the temperature was 130-150°C, the cationic surfactant solution obtained in step (1) was added and mixed evenly. The mixture was added in three portions, each adding 60 ml. The mixture was mixed at a speed of 800 rpm for 1 hour and vacuum dried to obtain cationic surfactant-modified stainless steel powder.

[0011] (2) Preparation of anionic surfactant modified stainless steel powder

[0012] (2.1) Thoroughly stir 32 g of anionic surfactant and 200 ml of acetone until dissolved to obtain an anionic surfactant solution.

[0013] (2.2) 8 kg of stainless steel powder was added to a high-speed mixer. When the temperature was 130-150°C, the anionic surfactant solution obtained in step (1) was added and mixed evenly. The mixture was added in three portions, each adding 70 ml. The mixture was mixed at a speed of 800 rpm for 1 hour and vacuum dried to obtain anionic surfactant-modified stainless steel powder.

[0014] (3) Preparation of injection molding feed

[0015] 115.5-120.3 g of cationic surfactant-modified stainless steel powder, 115.5-120.3 g of anionic surfactant-modified stainless steel powder, 13.4-15.1 g of backbone polymer polymethyl methacrylate and 5.3-6.1 g of polyethylene glycol are added to an internal mixer. The mixing conditions are: internal mixer speed of 50-80 rpm, temperature of 160-190° C., and time of 15-30 min to obtain injection molding feed of anionic and cationic surfactant-modified stainless steel powder.

[0016] Further preparation operation technical scheme is as follows:

[0017] In step (1), the cationic surfactant is one of 1-alkyl-3-methylimidazolium n-alkylsulfonate, 1-dodecyl-3-methylimidazolium chloride, and 1-hexadecyl-3-methylimidazolium bromide.

[0018] In step (2), the anionic surfactant is one of sodium hexadecyl sulfate, sodium dodecylbenzenesulfonate, and sodium stearoyl lactate.

[0019] In step (3), the molecular weight of the polyethylene glycol is 1500.

[0020] The beneficial technical effects of the present invention are reflected in the following aspects:

[0021] (1) In the present invention, stainless steel powder is modified with anionic and cationic surfactants respectively. These two surfactants can effectively wet the stainless steel powder, thereby changing the surface properties of the stainless steel powder, reducing the surface energy of the stainless steel powder, and promoting the selected skeleton polymer and polyethylene glycol to be uniformly coated on the stainless steel powder.

[0022] (2) The stainless steel powder modified with the cationic surfactant has a large amount of positive charges on its surface, and the stainless steel powder modified with the anionic surfactant has a large amount of negative charges on its surface. See Figure 2 . During the preparation of the feedstock, electrostatic interaction occurs between the two types of stainless steel powders. The stainless steel powders are more closely connected through electrostatic forces, so that less polymer can fill the gaps between the powders, effectively improving the powder volume loading. On the premise of ensuring good fluidity of the feedstock, the density of the feedstock can be increased, the mechanical properties of the green body can be improved, the thermal debinding shrinkage can be reduced, and the dimensional accuracy of the product can be improved.

[0023] (3) The powder volume loading of the injection molding feedstock of the stainless steel powder prepared by the present invention is 62-65%. Its melt index is 34.0-40.9 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green body is 5.30-5.49 g / cm 3 , and the flexural modulus of the green body is 2480-2950 MPa. The components in the present invention cooperate with each other to achieve the purpose of improving the properties of the green body on the premise of ensuring good fluidity of the feedstock. Brief Description of the Drawings

[0024] Figure 1 It is a process flow chart of the preparation of an injection molding feedstock composed of stainless steel powder modified with anionic and cationic surfactants and a binder.

[0025] Figure 2 It is a schematic diagram of the interaction between stainless steel powders modified with anionic and cationic surfactants. Detailed Embodiments

[0026] The sources of the materials used in the following examples are described as follows:

[0027] In addition to the raw materials used in the present invention, all of them can be purchased on the market. For example, the stainless steel powder used in the present invention is produced by Sandvik Osprey in the UK, polyethylene glycol is produced by Sinopharm Group, and the cationic surfactant is produced by Qingdao Aolike New Materials Co., Ltd. The rest of the raw materials are common materials that are well-known and publicly used, and there are various manufacturers and procurement methods.

[0028] Example 1

[0029] See Figure 1 , and the preparation operation steps of an injection molding feedstock of stainless steel powder modified by anionic and cationic surfactants are as follows:

[0030] (1) Preparation of stainless steel powder modified by cationic surfactant

[0031] (1.1) Weigh 32 g of 1-dodecyl-3-methylimidazolium chloride and stir it thoroughly with 150 ml of ethanol until dissolved to obtain a 1-dodecyl-3-methylimidazolium chloride solution;

[0032] (1.2) Add 8 kg of 17-4PH stainless steel powder to a high-speed mixer. When the temperature reaches 150 °C, add the 1-dodecyl-3-methylimidazolium chloride solution obtained in step (1.1), mix evenly, and add it in three portions, 60 ml each time; mix at 800 rpm for 1 h and dry in vacuum for 6 h to obtain stainless steel powder modified by cationic surfactant.

[0033] (2) Preparation of stainless steel powder modified by anionic surfactant

[0034] (2.1) Weigh 32 g of sodium stearoyl lactate and stir it thoroughly with 200 ml of acetone until dissolved to obtain a sodium stearoyl lactate solution;

[0035] (2.2) Add 8 kg of 17-4PH stainless steel powder to a high-speed mixer. When the temperature reaches 150 °C, add the anionic surfactant solution obtained in step (2.1), mix evenly, and add it in three portions, 70 ml each time; mix at 800 rpm for 1 h and dry in vacuum for 6 h to obtain stainless steel powder modified by anionic surfactant.

[0036] (3) Preparation of injection molding feedstock

[0037] 120.285 g of 1-dodecyl-3-methylimidazolium chloride modified stainless steel powder, 120.285 g of sodium stearoyl lactate modified stainless steel powder, 13.447 g of polymethyl methacrylate and 5.372 g of polyethylene glycol 1500 were added to a mixer, and the mixing conditions were: mixer speed 50 rpm, temperature 175 °C, mixing time 20 min, to obtain an injection molding feedstock of anionic and cationic surfactant modified stainless steel powder.

[0038] The powder volume loading of the injection molding feedstock prepared in Example 1 was 64 vol%, the melt index was 40.1 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green compact prepared with the injection molding feedstock was 5.42 g / cm 3 , and the flexural modulus of the green compact was 2923 MPa.

[0039] Example 2

[0040] See Figure 1 , and the preparation operation steps of an injection molding feedstock of anionic and cationic surfactant modified stainless steel powder are as follows:

[0041] (1) The steps for preparing the cationic surfactant modified powder are as follows:

[0042] (1.1) Weigh 32 g of 1-alkyl-3-methylimidazolium n-alkylsulfonate and stir it with 150 ml of ethanol until dissolved to obtain a 1-alkyl-3-methylimidazolium n-alkylsulfonate solution;

[0043] (1.2) Add 8 kg of 17-4PH stainless steel powder to a high-speed mixer. When the temperature is 150 °C, add the 1-alkyl-3-methylimidazolium n-alkylsulfonate solution obtained in step (1.1) and mix evenly. Add it in three portions, 60 ml of 1-alkyl-3-methylimidazolium n-alkylsulfonate solution each time; mix at 800 rpm for 1 hour and vacuum dry for 6 h to obtain the cationic surfactant modified stainless steel powder.

[0044] (2) The steps for preparing the anionic surfactant modified stainless steel powder are as follows:

[0045] (2.1) Weigh 32 g of sodium dodecylbenzenesulfonate and stir it with 200 ml of acetone until dissolved to obtain a sodium dodecylbenzenesulfonate solution;

[0046] (2.2) Add 8 kg of 17-4PH stainless steel powder into a high-speed mixer. When the temperature reaches 150 °C, add the sodium dodecylbenzenesulfonate solution obtained in step (2.1), mix evenly, and add it in three portions, with 70 ml of the solution added each time. Mix at a rotation speed of 800 rpm for 1 h and then dry in vacuum for 6 h to obtain an anion surfactant-modified stainless steel powder.

[0047] The steps for preparing an injection molding feedstock are as follows:

[0048] Add 118.407 g of 1-alkyl-3-methylimidazolium n-alkylsulfonate-modified stainless steel powder, 118.407 g of sodium dodecylbenzenesulfonate-modified stainless steel powder, 13.853 g of polymethyl methacrylate, and 5.531 g of polyethylene glycol into a kneader. The kneading conditions are: the rotation speed of the kneader is 50 rpm, the temperature is 175 °C, and the kneading time is 20 min to obtain an injection molding feedstock of an anion and cation surfactant-modified stainless steel powder.

[0049] The powder volume loading of the injection molding feedstock prepared in Example 2 is 63 vol%, the melt index of the feedstock is 36.5 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green compact prepared with the injection molding feedstock is 5.31 g / cm 3 , and the flexural modulus of the green compact is 2481 MPa.

[0050] Example 3

[0051] Refer to Figure 1 , and the preparation operation steps of an injection molding feedstock of an anion and cation surfactant-modified stainless steel powder are as follows:

[0052] (1) Prepare a cation surfactant-modified stainless steel powder

[0053] (1.1) Weigh 32 g of 1-hexadecyl-3-methylimidazolium bromide and stir it thoroughly with 150 ml of ethanol until dissolved to obtain a 1-hexadecyl-3-methylimidazolium bromide solution;

[0054] (1.2) Add 8 kg of 17-4PH stainless steel powder into a high-speed mixer. When the temperature reaches 150 °C, add the 1-hexadecyl-3-methylimidazolium bromide solution obtained in step (1.1), mix evenly, and add it in three portions, with 60 ml of the 1-hexadecyl-3-methylimidazolium bromide solution added each time. Mix at a rotation speed of 800 rpm for 1 h and then dry in vacuum for 6 h to obtain a cation surfactant-modified stainless steel powder.

[0055] (2) Prepare an anion surfactant-modified stainless steel powder

[0056] (2.1) Weigh 32 g of sodium hexadecyl sulfate and stir it thoroughly with 200 ml of acetone until it dissolves to obtain a sodium hexadecyl sulfate solution;

[0057] (2.2) Add 8 kg of 17-4PH stainless steel powder to a high-speed mixer. When the temperature reaches 150 °C, add the sodium hexadecyl sulfate solution obtained in step (2.1), mix evenly, and add it in three portions, 70 ml of the solution each time; mix at a rotational speed of 800 rpm for 1 h and dry in vacuum for 6 h to obtain an anion surfactant-modified stainless steel powder.

[0058] (3) Prepare an injection molding feedstock

[0059] Add 116.528 g of 1-hexadecyl-3-methylimidazolium bromide-modified stainless steel powder, 116.528 g of sodium hexadecyl sulfate-modified stainless steel powder, 14.240 g of polymethyl methacrylate, and 5.689 g of polyethylene glycol to a mixer. The mixing conditions are: mixer rotational speed 50 rpm, temperature 175 °C, mixing time 20 min to obtain an injection molding feedstock of an anion and cation surfactant-modified stainless steel powder.

[0060] The powder volume loading of the injection molding feedstock prepared in Example 3 of this example is 62 vol%, the melt index of the feedstock is 34.7 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green compact is 5.40 g / cm 3 and the flexural modulus of the green compact is 2527 MPa.

[0061] Comparative Example 1

[0062] Weigh 239.616 g of 17-4PH stainless steel powder without any surfactant modification, 14.273 g of polymethyl methacrylate, and 5.372 g of polyethylene glycol and add them to a mixer. Set the rotational speed of the mixer to 50 rpm, the mixing temperature to 175 °C, and the mixing time to 20 min.

[0063] The powder volume loading of the injection molding feedstock prepared in Comparative Example 1 of this example is 64 vol%, the melt index of the feedstock is 10.5 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green compact is 5.10 g / cm 3 and the flexural modulus of the green compact is 997 MPa.

[0064] Comparative Example 2

[0065] Weigh 235.872 g of 17-4PH stainless steel powder without any surfactant modification, 14.670 g of polymethyl methacrylate, and 5.861 g of polyethylene glycol and add them to a mixer. Set the rotation speed of the mixer to 50 rpm, the mixing temperature to 175 °C, and the mixing time to 20 min.

[0066] The powder volume loading of the injection molding feedstock prepared in Comparative Example 2 is 63 vol%, the melt index of the feedstock is 9.3 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green compact is 5.12 g / cm 3 , and the flexural modulus of the green compact is 872 MPa.

[0067] Comparative Example 3

[0068] Weigh 232.128 g of 17-4PH stainless steel powder without any surfactant modification, 15.066 g of polymethyl methacrylate, and 6.019 g of polyethylene glycol and add them to a mixer. Set the rotation speed of the mixer to 50 rpm, the mixing temperature to 175 °C, and the mixing time to 20 min.

[0069] The powder volume loading of the injection molding feedstock prepared in Comparative Example 3 is 62 vol%, the melt index of the feedstock is 11.3 g / 10 min (temperature 190 °C, load 2.16 kg), and the density of the green compact is 5.14 g / cm 3 , and the flexural modulus of the green compact is 1162 Mpa; The comparison of the melt index, the density of the green compact, and the flexural modulus parameters of the injection molding feedstocks prepared in Examples 1-3 and the injection molding feedstocks of Comparative Examples 1-3 is shown in the following table;

[0070]

[0071] As can be seen from the above table, for injection molding feedstocks prepared with the same powder loading, i.e., the same weight of stainless steel powder, under the same process and with the same binder, compared with the injection molding feedstock composed of unmodified stainless steel powder and binder, the melt index of the injection molding feedstock composed of a mixture of cationic surfactant-modified stainless steel powder and anionic surfactant-modified stainless steel powder and binder has increased, and the feedstock density and flexural modulus of the green compact have been improved to a certain extent.

[0072] It is easy for those skilled in the art to understand that the above Examples 1-3 are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An injection molding feedstock of anionic and cationic surfactant modified stainless steel powder, characterized in that: The injection molding feedstock is prepared by mixing 115.5 - 120.3 g of cationic surfactant-modified stainless steel powder, 115.5 - 120.3 g of anionic surfactant-modified stainless steel powder, 13.4 - 15.1 g of the skeletal polymer polymethyl methacrylate, and 5.3 - 6.1 g of polyethylene glycol through kneading; Under the test conditions of a temperature of 190 °C and a load of 2.16 kg, the melt index of the injection molding feedstock is 34.0 to 40.9 g / 10 min, and the density of the green compact prepared from the injection molding feedstock is 5.30 to 5.49 g / cm 3 , and the flexural modulus of the green compact is 2480 to 2950 MPa; The preparation operation steps of the injection molding feedstock are as follows: (1) Preparation of cationic surfactant-modified stainless steel powder (1.1) Stir 32 g of cationic surfactant and 150 ml of ethanol until dissolved to obtain a cationic surfactant solution; (1.2) Add 8 Kg of stainless steel powder to a high-speed mixer. When the temperature is 130 - 150 °C, add the cationic surfactant solution obtained in step (1.1), mix evenly, and add it in three portions, with each portion being 60 ml. Mix at a rotation speed of 800 rpm for 1 h and then perform vacuum drying to obtain cationic surfactant-modified stainless steel powder; (2) Preparation of anionic surfactant-modified stainless steel powder (2.1) Stir 32 g of anionic surfactant and 200 ml of acetone until dissolved to obtain an anionic surfactant solution; (2.2) Add 8 Kg of stainless steel powder to a high-speed mixer. When the temperature is 130 - 150 °C, add the anionic surfactant solution obtained in step (2.1), mix evenly, and add it in three portions, with each portion being 70 ml. Mix at a rotation speed of 800 rpm for 1 h and then perform vacuum drying to obtain anionic surfactant-modified stainless steel powder; (3) Preparation of injection molding feedstock Add 115.5 - 120.3 g of cationic surfactant-modified stainless steel powder, 115.5 - 120.3 g of anionic surfactant-modified stainless steel powder, 13.4 - 15.1 g of the skeletal polymer polymethyl methacrylate, and 5.3 - 6.1 g of polyethylene glycol to a kneader. The kneading conditions are: kneader rotation speed 50 - 80 rpm, temperature 160 - 190 °C, and time 15 - 30 min to obtain an injection molding feedstock of cationic and anionic surfactant-modified stainless steel powder.

2. The injection molding feedstock of a stainless steel powder modified by an anionic and cationic surfactant according to claim 1, characterized in that: In step (1), the cationic surfactant is one of 1-alkyl-3-methylimidazolium n-alkylsulfonate, 1-dodecyl-3-methylimidazolium chloride, and 1-hexadecyl-3-methylimidazolium bromide.

3. The injection molding feedstock of a stainless steel powder modified by an anionic and cationic surfactant according to claim 1, characterized in that: In step (2), the anionic surfactant is one of sodium hexadecyl sulfate, sodium dodecylbenzenesulfonate, and sodium stearoyl lactate.

4. The injection molding feedstock of a stainless steel powder modified by an anionic and cationic surfactant according to claim 1, characterized in that: In step (3), the molecular weight of the polyethylene glycol is 1500.

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