Binder system for powder injection molding compound

Abstract

Binder system for a powder injection molding compound, in particular a metal and / or ceramic powder injection molding compound, comprising - at least one polymer and - at least one hydroxybenzoic acid fatty alcohol ester and - at least one fatty acid, wherein the binder system comprises at least a first hydroxybenzoic fatty alcohol ester and a second hydroxybenzoic fatty alcohol ester, wherein the fatty alcohol of the second hydroxybenzoic fatty alcohol ester has a shorter carbon chain length than the fatty alcohol of the first hydroxybenzoic fatty alcohol ester, wherein the first hydroxybenzoic fatty alcohol ester is a fatty alcohol with a carbon chain length of ≥ 20 to ≤ 24 carbon atoms and the second hydroxybenzoic fatty alcohol ester is a fatty alcohol with a carbon chain length of ≥ 14 to ≤ 18 carbon atoms, and wherein the weight fraction of the second hydroxybenzoic fatty alcohol ester of the binder system is less than, in particular less than or equal to, half the weight fraction of the first hydroxybenzoic fatty alcohol ester of the binder system.

Description

State of the art

[0001] One method for shaping complex metallic components is metal injection molding (MIM). To create a moldable mass, known as a feedstock, metal powder is mixed with binder components.

[0002] Polyamides are often used as polymeric binder components.

[0003] The document DE 10 2008 054 615 A1 describes a process for producing an ester from a hydroxybenzoic acid and a fatty alcohol for use in a binder system for powder injection molding, as well as a corresponding binder system.

[0004] From US 2011 / 0294935 A1 a process is known for producing an ester of a hydroxybenzoic acid and a fatty alcohol for use in a binder system for powder injection molding, in which a transesterification of an ester of hydroxybenzoic acid and a lower alcohol is carried out using the fatty alcohol.

[0005] Quaternary ammonium compounds of the esterquat type and a process for their preparation are known from DE 10 2010 029 610 A1.

[0006] EP 1 881 025 A1 describes the use of polyethylene glycol esters and fatty acids of the formula R 1 -CO-O-(CH2CH2-O) n -OC-R 2 described, where the residues R 1 and R 2independently of one another represent alkyl groups having 7 to 23 carbon atoms, which may be saturated or unsaturated, linear or branched, and n represents a number in the range from 2 to 50, as lubricants in the processing of thermoplastics.

[0007] From DE 10 2009 008 685 A1 a method for producing a component by injection molding is known.

[0008] From US 2009 / 0160105 A1 a process for producing a shaped body based on a molding compound is known. Disclosure of the invention

[0009] The present invention relates to a binder system for a powder injection molding compound, for example a metal and / or ceramic powder injection molding compound, in particular a metal powder injection molding compound, which comprises at least one polymer and at least one hydroxybenzoic acid fatty alcohol ester.

[0010] A fatty alcohol can be understood in particular as a saturated or unsaturated, linear or branched, monohydric primary alcohol with a carbon chain length of ≥ 8 carbon atoms to ≤ 24 carbon atoms.

[0011] In order to improve the homogeneity and processability of the powder injection molding compound, the binder system comprises in particular at least one fatty acid.

[0012] A fatty acid can be understood in particular as a saturated or unsaturated, linear or branched carboxylic acid with a carbon chain length of ≥ 8 carbon atoms to ≤ 24 carbon atoms.

[0013] The addition of fatty acids can advantageously improve the dispersion properties of the binder system and thus the homogeneity of the powder injection molding compound, reduce the tendency toward segregation at deflections and the flow front, and lower the viscosity. Overall, this also allows for a more homogeneous distribution of the powder injection molding compound in the cavity of the injection mold. Furthermore, the addition of fatty acids can reduce the holding pressure during the powder injection molding process. In particular, the addition of fatty acids makes it easy to adjust the melting range of the binder system. For example, it has been shown that the addition of fatty acids can lower and broaden the melting range.By lowering and broadening the melting range, the powder injection molding compound solidifies more slowly and evenly in the cavity of the injection molding tool, which has a particularly beneficial effect on the roundness of bores or the roundness of rotationally symmetrical components themselves.

[0014] In one embodiment, the binder system comprises at least one fatty acid that has a shorter or equal carbon chain length than the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length. In particular, the binder system can comprise at least one fatty acid that has a shorter carbon chain length than the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length. For example, the binder system can comprise at least one fatty acid that has a shorter or equal, in particular shorter, carbon chain length than the average carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or than the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system individually.For example, the binder system may comprise one or more fatty acids which on average or even all have a smaller or the same, in particular smaller, carbon chain length than the average carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or than the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system individually.

[0015] The carbon chain length of the at least one fatty acid, for example of a fatty acid or of at least one fatty acid, optionally also of several fatty acids or even of all fatty acids, for example by at least 2 carbon atoms, for example by at least 3 carbon atoms or by at least 4 carbon atoms, for example by at least 5 carbon atoms or by at least 6 carbon atoms, can be shorter than the carbon chain length of the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length, optionally also than the average carbon chain lengths of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or even than the carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system in detail.Optionally, the carbon chain length of the at least one fatty acid, for example of at least one fatty acid, optionally also of several fatty acids or even of all fatty acids, for example by a maximum of 8 carbon atoms, for example by a maximum of 7 carbon atoms or by a maximum of 6 carbon atoms, can be shorter than the carbon chain length of the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length, optionally also than the average carbon chain lengths of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or even than the carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system in detail.

[0016] The structure of the at least one shorter-chain or equally long, in particular shorter-chain, fatty acid can be particularly similar to the structure of the fatty alcohol. For example, both the at least one shorter-chain or equally long, in particular shorter-chain, fatty acid and the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester can be saturated or unsaturated, or linear or branched, in particular saturated and optionally linear. By using one or more fatty acids with a shorter or equal carbon chain length compared to the fatty alcohol ester and optionally a similar structure, the melting range of the binder system can advantageously be shifted to lower temperatures and also broadened.By using one or more fatty acids with a shorter carbon chain length and possibly a similar structure compared to the fatty alcohol ester, the melting range of the binder system can be advantageously shifted and broadened particularly effectively towards lower temperatures.

[0017] In one embodiment, the at least one fatty acid has a carbon chain length of ≥ 14 carbon atoms to ≤ 24 carbon atoms. For example, the at least one fatty acid can have a carbon chain length of ≥ 14 carbon atoms to ≤ 22 carbon atoms, in particular of ≥ 14 carbon atoms or ≥ 15 carbon atoms or ≥ 16 carbon atoms or ≥ 17 carbon atoms to ≤ 22 carbon atoms or ≤ 21 carbon atoms or ≤ 20 carbon atoms or ≤ 19 carbon atoms or ≤ 18 carbon atoms, for example of ≥ 16 carbon atoms or ≥ 17 carbon atoms to ≤ 22 carbon atoms or ≤ 20 carbon atoms or ≤ 19 carbon atoms, for example of 18 carbon atoms.

[0018] In particular, the at least one fatty acid may be a saturated carboxylic acid, for example a saturated and linear carboxylic acid.

[0019] For example, the at least one fatty acid may be selected from the group consisting of behenic acid (C 22 H 44 O2, docosanoic acid), heneicosanoic acid (C 21 H 42 O2), arachidic acid (C 20 H 40 O2, eicosanoic / icosanoic acid), nonadecanoic acid (C 19 H 38 O2), stearic acid (C 18 H 36 O2, octadecanoic acid), heptadecanoic acid (C 17 H 34 O2), palmitic acid (C 16 H 32 O2, hexadecanoic acid), pentadecanoic acid (C 15 H 30 O2), myristic acid (C 14 H 28 O2, tetradecanoic acid) and mixtures thereof.

[0020] It is possible that the binder system comprises only one fatty acid, for example whose carbon chain length is in a range of ≥ 16 carbon atoms and ≤ 20 carbon atoms, in particular of ≥ 17 carbon atoms and ≤ 19 carbon atoms, for example 18 carbon atoms.

[0021] In another embodiment, however, the binder system comprises at least two fatty acids. This advantageously allows a particularly broad melting range to be achieved.

[0022] The at least two fatty acids can also be from the group consisting of behenic acid (C 22 H 44 O2, docosanoic acid), heneicosanoic acid (C 21 H 42 O2), arachidic acid (C 20 H 40 O2, eicosanoic / icosanoic acid), nonadecanoic acid (C 19 H 38 O2), stearic acid (C 18 H 36 O2, octadecanoic acid), heptadecanoic acid (C 17 H 34 O2), palmitic acid (C 16 H 32 O2, hexadecanoic acid), pentadecanoic acid (C 15 H 30 O2), myristic acid (C 14 H 28 O2, tetradecanoic acid) and mixtures thereof.

[0023] It has been found that it is advantageous if the binder system comprises at least two fatty acids, in which case their average carbon chain length is less than or equal to, in particular less than, the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length.

[0024] In a specific embodiment, the binder system therefore comprises at least two fatty acids whose average carbon chain length is less than or equal to the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length. In particular, the binder system can comprise at least two fatty acids whose average carbon chain length is less than the carbon chain length of the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length.For example, the binder system can comprise at least two fatty acids whose average carbon chain length is less than or equal to, in particular less than, the average carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or even less than or equal to, in particular less than, the carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system individually.

[0025] The average carbon chain length of the fatty acids can be, for example, at least 2 carbon atoms, for example at least 3 carbon atoms or at least 4 carbon atoms, shorter than the carbon chain length of the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length, optionally also than the average carbon chain lengths of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or even than the carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system in detail.Optionally, the average carbon chain length of the fatty acids can be, for example, by a maximum of 8 carbon atoms, for example by a maximum of 7 carbon atoms or by a maximum of 6 carbon atoms, shorter than the carbon chain length of the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length, optionally also than the average carbon chain lengths of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system or even than the carbon chain length of the fatty alcohols of all hydroxybenzoic acid fatty alcohol esters contained in the binder system in detail.

[0026] For example, the binder system may comprise at least two fatty acids whose average carbon chain length is in a range of ≥ 16 carbon atoms and ≤ 20 carbon atoms, in particular ≥ 17 carbon atoms and ≤ 19 carbon atoms, for example 18 carbon atoms.

[0027] It has been found to be advantageous if the binder system comprises palmitic acid and / or behenic acid and / or stearic acid.

[0028] In particular, the binder system can comprise stearic acid, palmitic acid, palmitic acid and behenic acid, palmitic acid and stearic acid, or stearic acid and behenic acid. These fatty acids or fatty acid combinations have proven particularly advantageous for a low-melting, broad-melting binder system and for achieving good roundness in round components.

[0029] Palmitic acid has proven particularly advantageous for lowering the melting temperature.

[0030] In a further embodiment, the binder system therefore comprises, in particular at least, palmitic acid.

[0031] However, if the binder system comprises only one fatty acid, it has proven advantageous if this fatty acid has a carbon chain length in the range of ≥ 17 carbon atoms and ≤ 19 carbon atoms. For example, the binder system can comprise nonadecanoic acid, stearic acid, or heptadecanoic acid, especially stearic acid, as the sole fatty acid.

[0032] In a further embodiment, the fatty acid weight fraction of the binder system is lower than the hydroxybenzoic acid fatty alcohol ester weight fraction of the binder system. This has proven particularly advantageous for ensuring good dispersion of the components of the powder injection molding compound and achieving a homogeneous distribution of the components of the powder injection molding compound in the melt. For example, the fatty acid weight fraction of the binder system can be less than or equal to half, in particular less than or equal to one-third, of the hydroxybenzoic acid fatty alcohol ester weight fraction of the binder system.

[0033] In a further embodiment, the at least one hydroxybenzoic acid fatty alcohol ester has a carbon chain length of ≥ 14 carbon atoms to ≤ 24 carbon atoms.

[0034] In particular, the at least one hydroxybenzoic acid fatty alcohol ester may be an ester of a saturated fatty alcohol, for example a saturated and linear fatty alcohol. For example, the at least one hydroxybenzoic acid fatty alcohol ester may be selected from the group consisting of hydroxybenzoic acid lignoceryl ester (C 31 H 54 O3), behenyl hydroxybenzoate (C 29 H 50 O3), hydroxybenzoic acid arachidyl ester (C 27 H 46 O3), hydroxybenzoic acid stearyl ester (C 25 H 42 O3), hydroxybenzoic acid palmityl ester (C 23 H 38 O3), hydroxybenzoic acid myristyle ester (C 21 H 34 O3) and mixtures thereof.

[0035] In particular, the binder system may comprise one or more hydroxybenzoic acid fatty alcohol esters prepared as described in the document DE 10 2008 054 615 A1.

[0036] Preferably, the binder system comprises at least one hydroxybenzoic acid fatty alcohol ester whose fatty alcohol has a carbon chain length of ≥ 14 carbon atoms to ≤ 22 carbon atoms, in particular of ≥ 14 carbon atoms to ≤ 20 carbon atoms, for example of ≥ 14 carbon atoms, or for example ≥ 15 carbon atoms or ≥ 16 carbon atoms or ≥ 17 carbon atoms, to ≤ 20 carbon atoms, or for example ≤ 19 carbon atoms or ≤ 18 carbon atoms or ≤ 17 carbon atoms or ≤ 16 carbon atoms.

[0037] By using a hydroxybenzoic acid fatty alcohol ester with a short-chain fatty alcohol, the melting range of the powder injection molding compound can be advantageously reduced and broadened. This allows for lower holding pressure during the powder injection molding process. It also allows the powder injection molding compound to solidify more slowly in the cavity of the injection molding tool, which has a particularly beneficial effect on the roundness of the resulting round components.

[0038] In a further embodiment, the binder system comprises at least two hydroxybenzoic acid fatty alcohol esters, for example, with fatty alcohols of different carbon chain lengths. This advantageously also allows a particularly broad melting range to be achieved.

[0039] Within the scope of one embodiment of this embodiment, the binder system comprises at least a first hydroxybenzoic acid fatty alcohol ester and a second hydroxybenzoic acid fatty alcohol ester, wherein the fatty alcohol of the second hydroxybenzoic acid fatty alcohol ester has a shorter carbon chain length than the fatty alcohol of the first hydroxybenzoic acid fatty alcohol ester. The fatty alcohols of the first and second hydroxybenzoic acid fatty alcohol esters can, in particular, have a similar structure. For example, both the fatty alcohol of the first hydroxybenzoic acid fatty alcohol ester and the fatty alcohol of the second hydroxybenzoic acid fatty alcohol ester can be saturated or unsaturated, or linear or branched, in particular saturated and optionally linear.By using a hydroxybenzoic acid fatty alcohol ester whose fatty alcohol—compared to the fatty alcohol of the other hydroxybenzoic acid fatty alcohol ester—has a shorter carbon chain length and, if appropriate, a similar structure, the melting range of the binder system can be advantageously shifted particularly effectively toward lower temperatures and broadened. This, in turn, can cause the powder injection molding compound to solidify more slowly in the cavity of the injection mold, which has a particularly beneficial effect on the roundness of the round components produced from it.

[0040] For example, the first hydroxybenzoic acid fatty alcohol ester can comprise a fatty alcohol with a carbon chain length of ≥ 20 carbon atoms to ≤ 24 carbon atoms, and the second hydroxybenzoic acid fatty alcohol ester can comprise a fatty alcohol with a carbon chain length of ≥ 14 carbon atoms to ≤ 20, in particular of ≥ 14 carbon atoms to ≤ 18, for example, of ≥ 14 carbon atoms to ≤ 16, for example, of 14 carbon atoms. This combination has proven particularly advantageous for a low-melting and broad-melting binder system and thus for achieving good roundness of round components.

[0041] In particular, the binder system may comprise two or more hydroxybenzoic acid fatty alcohol esters whose fatty alcohols have an average carbon chain length in a range of ≥ 16 carbon atoms and ≤ 20 carbon atoms, in particular of ≥ 17 carbon atoms and ≤ 19 carbon atoms, for example of 18 carbon atoms.

[0042] Preferably, the weight fraction of the second hydroxybenzoic acid fatty alcohol ester of the binder system is lower than the weight fraction of the first hydroxybenzoic acid fatty alcohol ester of the binder system. This advantageously ensures good demoldability of the component from the cavity. For example, the weight fraction of the second hydroxybenzoic acid fatty alcohol ester of the binder system can be less than or equal to half, in particular less than or equal to one-third, for example less than or equal to one-quarter or one-fifth, of the weight fraction of the first hydroxybenzoic acid fatty alcohol ester of the binder system.

[0043] In particular, the weight fraction of the first hydroxybenzoic acid fatty alcohol ester can be ≥ 80 wt.% to ≤ 99.9 wt.% and the weight fraction of the second hydroxybenzoic acid fatty alcohol ester can be ≥ 0.1 wt.% to ≤ 20 wt.%, based on the total weight of the hydroxybenzoic acid fatty alcohol esters of the binder system.

[0044] The polymer weight fraction of the binder system may, in particular, also be less than the hydroxybenzoic acid fatty alcohol ester weight fraction of the binder system. For example, the polymer weight fraction of the binder system may also be less than or equal to two-thirds, optionally less than or equal to half, of the hydroxybenzoic acid fatty alcohol ester weight fraction of the binder system.

[0045] In a further embodiment, the at least one polymer comprises a polyamide. In particular, the at least one polymer can be a polyamide or a polyamide blend, or a polyamide (block) copolymer. For example, the at least one polymer can be a copolyamide 612, a blend of polyamide 11 and polyamide 12, or a polyether block amide (PEBA).

[0046] The hydroxybenzoic acid fatty alcohol ester(s) can, in principle, be fatty alcohol esters of ortho-hydroxybenzoic acid, meta-hydroxybenzoic acid, or para-hydroxybenzoic acid, or a mixture of these hydroxybenzoic acids. In particular, the hydroxybenzoic acid fatty alcohol ester(s) can be fatty alcohol esters of ortho-hydroxybenzoic acid, para-hydroxybenzoic acid, or a mixture of these hydroxybenzoic acids.

[0047] With regard to further technical features and advantages of the binder system according to the invention, reference is hereby explicitly made to the explanations in connection with the powder injection molding compound according to the invention, the exemplary embodiments and the figures.

[0048] A further subject matter of the present invention is a powder injection molding compound (feedstock), for example a metal and / or ceramic powder injection molding compound, in particular a metal powder injection molding compound, which comprises a binder system according to the invention and at least one metal powder and / or at least one ceramic powder, in particular at least one metal powder.

[0049] In one embodiment, the powder injection molding compound comprises, based on the total weight of the powder injection molding compound, ≥ 70 wt.% to ≤ 99 wt.% metal and / or ceramic powder, in particular metal powder, and ≥ 1 wt.% to ≤ 30 wt.% binder system.

[0050] In particular, a metal powder injection molding compound can comprise, based on the total weight of the powder injection molding compound, ≥ 90 wt.% to ≤ 99 wt.% metal powder and ≥ 1 wt.% to ≤ 10 wt.% binder system.

[0051] A ceramic powder injection molding compound can in particular comprise, based on the total weight of the powder injection molding compound, ≥ 70 wt.% to ≤ 90 wt.% ceramic powder and ≥ 10 wt.% to ≤ 30 wt.% binder system.

[0052] In a further embodiment, the binder system comprises, based on the total weight of the powder injection molding compound, ≥ 0.1 wt.% to ≤ 5 wt.% of polymers, ≥ 0.1 wt.% to ≤ 10 wt.% of hydroxybenzoic acid fatty alcohol esters, and ≥ 0.1 wt.% to ≤ 5 wt.% of fatty acids. In particular, the binder system can comprise, based on the total weight of the powder injection molding compound, ≥ 1 wt.% to ≤ 3 wt.% of polymers, 2 wt.% to ≤ 6 wt.% of hydroxybenzoic acid fatty alcohol esters, and ≥ 0.5 wt.% to ≤ 2 wt.% of fatty acids.

[0053] Such binder systems or powder injection molding compounds are particularly easy to process and have proven advantageous for the production of round components with good roundness.

[0054] With regard to further technical features and advantages of the powder injection molding compound according to the invention, reference is hereby explicitly made to the explanations in connection with the binder system according to the invention, the exemplary embodiments and the figures.

[0055] Furthermore, the present invention relates to a molded part which is produced using a binder system according to the invention or from a powder injection molding compound according to the invention, in particular by means of powder injection molding, for example by means of metal and / or ceramic powder injection molding.

[0056] In particular, the molded part can be a rounded or round component. For example, the molded part can be a valve body or a multi-hole valve.

[0057] With regard to further technical features and advantages of the molded part according to the invention, reference is hereby explicitly made to the explanations in connection with the binder system according to the invention, the powder injection molding compound according to the invention, the exemplary embodiments and the figures. Examples of implementation

[0058] Further advantages and advantageous embodiments of the inventive objects are illustrated by the exemplary embodiments and drawings and explained in the following description. It should be noted that the exemplary embodiments and drawings are merely descriptive and are not intended to limit the invention in any way.

[0059] To investigate the influence of fatty acids on the properties of powder injection molding compounds and injection-molded parts, valve bodies were manufactured from several powder injection molding compounds of comparable composition. Each powder injection molding compound contained a metal powder, a polyamide, a hydroxybenzoic acid fatty alcohol ester, and optionally one or more fatty acids.

[0060] It was found that the powder injection molding compounds containing fatty acids were more homogeneous than the fatty acid-free powder injection molding compounds and could advantageously be injection molded with lower holding pressure. Furthermore, the powder injection molding compounds containing fatty acids achieved a more homogeneous distribution of the powder injection molding compound in the cavity of the injection mold, which had a positive effect on the quality of the manufactured valve bodies.

[0061] To investigate the influence of different fatty acids or fatty acid mixtures on compositions containing hydroxybenzoic acid fatty alcohol esters, a hydroxybenzoic acid fatty alcohol ester and one or more fatty acids were weighed and mixed as indicated in Table 1. The weight percentages in Table 1 refer to the total weight of the components of the respective composition. Table 1: Compositions containing hydroxybenzoic acid fatty alcohol esters Nr. Hydroxybenzoic acid fatty alcohol esters (22 C) Behenic acid (22 C) Stearic acid (18 C) Palmitic acid (16 C) 0 100% by weight - - - 1 91% by weight 9 wt.% - - 2 76% by weight - 24% by weight - 3 76% by weight - - 24% by weight 4 76% by weight 12 wt.% 12 wt.% - 5 76% by weight - 12 wt.% 12 wt.% 6 76% by weight 12 wt.% - 12 wt.%

[0062] Compositions 0 to 6 were melted in high-walled preparation vials on a hot plate and cooled again with agitation. The melting ranges were then examined using differential scanning calorimetry (DSC). The results of the DSC are shown in Table 2. The results of the DSC are also shown in Fig.1 is shown in the form of a bar chart. Table 2: DSC results of the compositions given in Table 1 composition Melting range Nr. of [°C] up to [°C] Δ [K] 0 72,6 78,7 6,1 1 69,6 76,7 7,1 2 67,1 74,6 7,5 3 56 74,7 18,7 4 57 74,8 17,8 5 50 74,3 24,3 6 48 74,4 26,4

[0063] Table 2 and Fig. 1 show that the melting range 1 of the behenic acid-containing composition No. 1 is slightly widened and shifted towards lower temperatures compared to the melting range 0 of the fatty acid-free composition No. 0.

[0064] Table 2 and Fig. 1 also show that by adding stearic acid instead of behenic acid, the melting range 2 of the stearic acid-containing composition No. 2 could be slightly broadened and shifted towards lower temperatures compared to the melting range 1 of the behenic acid-containing composition No. 1.

[0065] Furthermore, Table 2 and Fig.1, that by adding palmitic acid, which has a significantly shorter carbon chain length (C16) than the fatty alcohol of the ester (C22), the melting range of the palmitic acid-containing composition No. 3 could be significantly broadened and shifted to significantly lower temperatures.

[0066] Table 2 and Fig. 1 further show that by adding a fatty acid combination, namely behenic acid and stearic acid in composition No. 4, an effect comparable to that of composition No. 3 containing palmitic acid can be achieved.

[0067] The data shown in Table 2 and Fig.The melting ranges of composition No. 5 containing stearic acid and palmitic acid and composition No. 6 containing behenic acid and palmitic acid, illustrated in Figure 1, show that a particularly strong reduction in the melting temperature and a particularly strong broadening of the melting range can be achieved by using a fatty acid combination in which - compared to the carbon chain length of the fatty alcohol of the ester (C22), one fatty acid has a significantly shorter carbon chain length (palmitic acid = C16) and the other fatty acid has a slightly shorter (stearic acid = C18) or an equally long carbon chain (behenic acid = C22).

[0068] To investigate the influence of hydroxybenzoic acid fatty alcohol ester fatty acid compositions on the properties of powder injection molding compounds and injection-molded parts, compositions Nos. 1 to 6 were each mixed with metal powder and polyamide to form powder injection molding compounds, and valve bodies were manufactured from the resulting powder injection molding compounds by metal powder injection molding (MIM).

[0069] The roundness of the manufactured valve bodies was checked using a coordinate measuring machine (CMM). Table 3: Results of roundness measurements composition Roundness Nr. [µm] 1 49 2 37,5 3 43,5 4 43,9 5 38,5 6 38,9

[0070] The results of the roundness measurements show that the melting temperature reduction and melting range expansion caused by compositions Nos. 1 to 6 prevent premature solidification of the powder injection molding compounds in the cavity of the injection molding tool and thus achieve a more homogeneous distribution of the injection molding compound in the cavity.

[0071] Table 3 shows in particular that good roundness values ​​can be achieved by adding a fatty acid or fatty acid mixture.

[0072] The measurement results for compositions 1 to 3 show that the roundness can be further improved by using the shorter-chain fatty acids stearic acid and palmitic acid in compositions 2 and 3, respectively, instead of the longer-chain behenic acid used in composition 1. The addition of stearic acid to composition 2 shows the most significant effect on the roundness of the components when using only one fatty acid.

[0073] Table 3 further shows that a combination of fatty acids can also improve roundness compared to composition No. 1 containing behenic acid. While the combination of the two fatty acids behenic acid and stearic acid in composition No. 4, with a roundness of 43.9 µm, is significantly better than composition No. 1 containing only behenic acid, the addition of the shorter-chain palmitic acid in composition No. 5 containing stearic acid and palmitic acid and composition No. 6 containing behenic acid and palmitic acid shows an even more pronounced effect on roundness.

[0074] This can be explained by the fact that a lower average carbon chain length of the fatty acids contained in the fatty acid mixture, which in the case of composition No. 4 is 20 carbon atoms, but in the case of compositions Nos. 5 and 6 is 17 carbon atoms and 19 carbon atoms respectively, also appears to have a positive influence on the roundness.

[0075] Overall, a sole or average fatty acid carbon chain length in a range of ≥ 16 carbon atoms to ≤ 20 carbon atoms, especially in a range of ≥ 17 carbon atoms to ≤ 19 carbon atoms, appears to have a beneficial effect on roundness.

[0076] The fact that an improvement in roundness can also be achieved through fatty acid combinations is particularly advantageous from this perspective, since on the one hand this provides a wider variety of raw materials that can be combined with one another and on the other hand it also allows average chain lengths to be adjusted where the corresponding individual fatty acid would be expensive or difficult to obtain or not producible, which in turn makes it possible to optimize the roundness even more.

Claims

[1] Binder system for a powder injection molding compound, in particular a metal and / or ceramic powder injection molding compound, comprising - at least one polymer and - at least one hydroxybenzoic acid fatty alcohol ester and - at least one fatty acid, wherein the binder system comprises at least a first hydroxybenzoic acid fatty alcohol ester and a second hydroxybenzoic acid fatty alcohol ester, wherein the fatty alcohol of the second hydroxybenzoic acid fatty alcohol ester has a shorter carbon chain length than the fatty alcohol of the first hydroxybenzoic acid fatty alcohol ester, wherein the first hydroxybenzoic acid fatty alcohol ester has a fatty alcohol with a carbon chain length of ≥ 20 carbon atoms to ≤ 24 carbon atoms and the second hydroxybenzoic acid fatty alcohol ester has a fatty alcohol with a carbon chain length of ≥ 14 carbon atoms to ≤ 18 and wherein the weight fraction of the second hydroxybenzoic acid fatty alcohol ester of the binder system is less, in particular less than or equal to half the weight fraction of the first hydroxybenzoic acid fatty alcohol ester of the binder system. [2] Binder system according to claim 1, wherein the binder system comprises at least one fatty acid which has a lower or equal, in particular lower, carbon chain length than the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length. [3] Binder system according to claim 1 or 2, wherein the at least one fatty acid has a carbon chain length of ≥ 14 carbon atoms to ≤ 24 carbon atoms. [4] Binder system according to one of claims 1 to 3, wherein the binder system comprises at least two fatty acids. [5] Binder system according to one of claims 1 to 4, wherein the binder system comprises at least two fatty acids whose average carbon chain length is less than or equal to, in particular less than, the fatty alcohol of the hydroxybenzoic acid fatty alcohol ester with the longest fatty alcohol carbon chain length, in particular wherein the binder system comprises at least two fatty acids whose average carbon chain length is in a range of ≥ 16 carbon atoms to ≤ 20 carbon atoms. [6] Binder system according to one of claims 1 to 5, wherein the binder system comprises behenic acid and / or stearic acid and / or palmitic acid. [7] Binder system according to one of claims 1 to 6, wherein the binder system comprises at least palmitic acid. [8] Binder system according to one of claims 1 to 7, wherein the fatty acid weight fraction of the binder system is less than the hydroxybenzoic acid fatty alcohol ester weight fraction of the binder system. [9] Binder system according to one of claims 1 to 8, wherein the at least one hydroxybenzoic acid fatty alcohol ester has a carbon chain length of ≥ 14 carbon atoms to ≤ 24 carbon atoms. [10] Binder system according to one of claims 1 to 9, wherein the at least one polymer comprises a polyamide, or is polyamide or a polyamide blend or a polyamide copolymer. [11] Powder injection molding compound comprising a binder system according to one of claims 1 to 10 and at least one metal powder and / or at least one ceramic powder, in particular at least one metal powder. [12] Powder injection molding compound according to claim 11, wherein the powder injection molding compound, based on the total weight of the powder injection molding compound, - ≥ 70 wt.% to ≤ 99 wt.% metal and / or ceramic powder, in particular metal powder, and - ≥ 1 wt% to ≤ 30 wt% binder system. [13] Powder injection molding compound according to claim 11 or 12, wherein the binder system, based on the total weight of the powder injection molding compound, - ≥ 0.1 wt% to ≤ 5 wt% of polymers, - ≥ 0.1 wt.% to ≤ 10 wt.% of hydroxybenzoic acid fatty alcohol esters and - ≥ 0.1 wt% to ≤ 5 wt% of fatty acids. [14] Moulded part produced using a binder system according to one of claims 1 to 10 or from a powder injection moulding compound according to one of claims 11 to 13.

Images