JPH10219303A - Composition for injection molding inorganic powder and sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the novel composition for injection molding an inorg. powder with less defects and high in product yield and a sintered compact. SOLUTION: This composition for injection molding an inorg. powder consists of an inorg. powder, 1-30 pts.wt. of an ethylene-vinyl acetate copolymer, based on 100 pts.wt. of the inorg. powder, 1-30 pts.wt. of low-density PE resin and 1-30 pts.wt. of a glyceride wax. The sintered compact is obtained by injection molding the composition, debindering and then sintering the compact obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composition for injection molding of an inorganic powder and a sintered body.

[0002]

2. Description of the Related Art Conventionally, a sintered product obtained by a powder metallurgy method has been produced based on a production method in which a metal powder or a ceramic powder as a molding composition is pressed and then sintered. . However, with this molding method, it was difficult to manufacture a product having a three-dimensionally complicated shape or a product having a thin portion such as a knife edge portion.

[0003] In order to solve the above-mentioned disadvantages of the powder metallurgy method, an injection molding composition comprising an inorganic powder and an organic binder is injection-molded into a mold having a desired shape. After the body is preheated and degreased, a method of obtaining the final sintered product through the sintering process is presented.For example, a wide range of products including general industrial machinery parts, electrical products, tools, precision machinery parts, medical equipment, etc. It has been adopted as a useful method in the field.

[0004]

In order to obtain a final sintered product from the composition for injection molding, it is necessary to use (1)
Good properties such as dimensional accuracy of the injection molded article, (2) variation in weight of the injection molded article, (3) degreasing property of the injection molded article, and (4) reusability of sprue (supply trough) and runners. Is required.

[0005] However, the conventional injection molding composition not only has large dimensional accuracy and weight variation, but also has many molding defects such as sink marks and cracks in the molded product, especially when large-sized thick-walled products are manufactured. There is a problem, and there is also a problem that blistering and sinking are likely to occur due to gasification of the organic binder during degreasing. Furthermore, these methods also have a problem that the density of the sintered body is apt to be insufficient, which causes a reduction in the commercialization rate. An object of the present invention is to solve the above problems and to provide a novel inorganic powder injection molding composition and a sintered body having few defects and a high productization rate.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted various studies to solve the above problems and achieve the above object. As a result, the inorganic powder and a specific amount of ethylene vinyl acetate copolymer as an organic binder were obtained. The inventors have found that the object can be achieved by forming a composition comprising the coalesced resin, a specific amount of a low-density polyethylene resin and a specific amount of a glycerin fatty acid ester wax, and have completed the present invention. That is, the first embodiment of the present invention comprises an inorganic powder,
Inorganic powder injection molding comprising 1 to 30 parts by weight of an ethylene vinyl acetate copolymer, 1 to 30 parts by weight of a low density polyethylene resin, and 1 to 30 parts by weight of a glycerin fatty acid ester wax based on parts by weight. When the inorganic powder is a metal powder, the inorganic powder is a metal powder and 100 parts by weight of the metal powder, respectively.
5 parts by weight of an ethylene vinyl acetate copolymer, 1 to 30 parts by weight of a low-density polyethylene resin, and 1 to 15 parts by weight of a glycerin fatty acid ester-based wax, and the inorganic powder is a ceramic powder. In some cases, ceramic powder, 10 to 25 parts by weight of ethylene vinyl acetate copolymer, 1 to 30 parts by weight of low density polyethylene resin, and 8 to 25 parts by weight with respect to 100 parts by weight of the ceramic powder. And a glycerin fatty acid ester wax.

Further, a second embodiment of the present invention relates to an inorganic powder, 1 to 30 parts by weight of an ethylene-vinyl acetate copolymer with respect to 100 parts by weight of the inorganic powder, and 1 to 30 parts by weight. Parts by weight of a low-density polyethylene resin, and 1 to 30 parts by weight of a glycerin fatty acid ester-based wax, after molding an inorganic powder injection molding composition by injection molding, after debinding the molded body,
It is characterized by a sintered body obtained by sintering.

[0008] The method and equipment applied to the production of such a composition or a sintered body are not particularly limited, and the methods and equipment conventionally applied to this kind of production can be applied. Things.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The injection molding composition of the present invention is characterized by using a mixed organic binder of an ethylene-vinyl acetate copolymer, a low-density polyethylene resin and a glycerin fatty acid ester wax with respect to an inorganic powder. is there.

The sinterable inorganic powder used in the present invention includes metal powder or ceramic powder. Examples of the metal powder include titanium, titanium-cobalt alloy, titanium-iron alloy and the like. Titanium-based fine powder, iron-based fine powder such as iron-silicon, carbonyl iron, molybdenum-based fine powder such as molybdenum, molybdenum-silicon-based, copper-based fine powder such as copper, copper-nickel, etc., SUS316L , SUS440, SUS
630 or the like; tungsten, a tungsten-based powder such as a tungsten-copper-based powder; and various metal fine powders such as an aluminum-lithium-based fine powder. Various ceramic fine powders such as fine powder, zirconia fine powder, silicon carbide fine powder, silicon nitride fine powder, barium titanate fine powder and the like can be mentioned.

The preferred particle size of these metal fine powders and ceramic fine powders is 50 μm or less on average, and particularly preferably 20 μm or less on average. If the average particle size exceeds 50 μm, the strength after sintering, dimensional stability, etc. are deteriorated, so that the effects of the present invention cannot be obtained. However, if it is less than 0.1 μm, it is expensive, so the lower limit is 0.1 μm.

As the ethylene-vinyl acetate copolymer, various commercially available ethylene-vinyl acetate copolymers having various molecular weights and vinyl acetate copolymerization ratios can be used. However,
The resin preferably has a melt viscosity of 10 g / 10 min or more in terms of a melt flow rate value according to JIS K6760, more preferably 50 g / 10 min or more, most preferably 100 g / 10 min or more. The one having a better effect is obtained. However, when the value is less than 10 g / 10 min, not only injection molding becomes difficult, but also the weight variation and dimensional variation after degreasing increase remarkably.
The effect of the present invention cannot be obtained.

The vinyl acetate copolymerization rate of the ethylene-vinyl acetate copolymer used in the present invention is preferably 30% or less. This is because if the copolymerization ratio exceeds 30%, it is difficult to obtain the effects of the present invention because the molding temperature is remarkably lowered and rubber-like elasticity is exhibited. The copolymerization ratio is preferably as small as possible, but if it is 5% or less, defects during molding are likely to appear, and the lower limit is 5%.

The amount of the ethylene-vinyl acetate copolymer added is
The amount is preferably in the range of 1 to 30 parts by weight based on 100 parts by weight of the inorganic powder.
In the case of 5 parts by weight, and in the case of ceramic powder, the range is preferably 10 to 25 parts by weight or less. This is because if the addition amount is less than 1 part by weight, the effect of the present invention cannot be obtained because a remarkable decrease in melt viscosity is caused.
If the amount exceeds 30 parts by weight, deformation and dimensional change after sintering become remarkable, and a desired product cannot be stably obtained.

These resins may have the above-mentioned desired melt viscosity after molding the composition. For example, two or more kinds of high-viscosity products, low-viscosity products deviating from the appropriate range of the melt flow rate value, and proper products may be used. May be used by adjusting the melt flow rate value to an appropriate range.

As the low-density polyethylene resin used in the present invention, commercially available resins having various molecular weights can be used. However, the melt viscosity of these resins is preferably a resin having a characteristic of 10 g / 10 min or more in terms of a melt flow rate value according to JIS K6760, more preferably 50 g / 10 min or more, most preferably 100 g / 10 min or more. The one having the characteristic of (1) can obtain a better effect. However, if the value is less than 10 g / 10 min, not only injection molding becomes difficult, but also the weight variation and dimensional variation after degreasing significantly increase, so that the effects of the present invention are obtained. Cannot do it.

The amount of the low-density polyethylene resin is preferably in the range of 1 to 30 parts by weight based on 100 parts by weight of the inorganic powder, 3 to 15 parts by weight when the inorganic powder is metal powder, and 3 to 15 parts by weight when the ceramic powder is used. Is more preferably in the range of 10 to 25 parts by weight or less. This is because if the addition amount is less than 1 part by weight, the effect of the present invention cannot be obtained because of a remarkable decrease in melt viscosity. If the addition amount exceeds 30 parts by weight, deformation after sintering or This is because the dimensional change becomes remarkable and a desired product cannot be obtained stably.

These resins may have the above-mentioned desired melt viscosity after the molding of the composition. For example, two or more kinds of high-viscosity products, low-viscosity products deviating from the appropriate range of the melt flow rate value, and proper products. May be used by adjusting the melt flow rate value to an appropriate range.

The mixing ratio of these two resins, that is, the ethylene vinyl acetate copolymer and the low density polyethylene resin, is preferably such that the ethylene vinyl acetate copolymer contains 5 to 50% by weight based on the total amount of both resins. . If the proportion of the ethylene-vinyl acetate copolymer is more than 50% by weight, defects at the time of degreasing become remarkable, and if it is less than 5% by weight, defects at the time of molding tend to occur, which is not preferable. More preferably, it is a ratio containing 10 to 30% by weight of the ethylene-vinyl acetate copolymer with respect to the total amount of both resins.

Further, as the glycerin fatty acid ester wax used in the present invention, commercially available waxes can be used, for example, glycerin monolaurate, glycerin monopalmitate, glycerin monopalmitate, glycerin monostearate. , Glycerin monooleate, glycerin monooleate, glycerin monobehenate, glycerin monocaprylate,
Glycerin monocaprate, glycerin monolinoleate, glycerin monoricinoleate, glycerin monoadipate, glycerin monosebacinate, glycerin dilaurate, glycerin dipalmirate, glycerin dipalmitate, glycerin distearate, glycerindiolate, glycerin dioleate Glycerin dibehenate, glycerin dicaprylate, glycerin dicaprate, glycerin dilinoleate, glycerin diricinolate, glycerin diadipate, glycerin disebacinate, and the like.Other than these, various saturated fatty acids, unsaturated fatty acids, As long as it is an ester conjugate of a fatty acid such as a chain fatty acid or a branched fatty acid and glycerin, it is not particularly limited, and may be used alone or as a mixture of two or more.

The amount of the glycerin fatty acid ester wax to be added is 1 to 100 parts by weight of the inorganic powder.
The range is preferably 30 parts by weight, more preferably 1 to 15 parts by weight when the inorganic powder is a metal powder and 8 to 25 parts by weight when the inorganic powder is a ceramic powder. This is because if the addition amount is less than 1 part by weight, the melt viscosity significantly decreases, the mold releasability of the molded product decreases,
Since the effects of the present invention cannot be obtained because of the variation in density of the molded article and the decrease in the strength of the molded article after degreasing, when added in more than 30 parts by weight, the moldability is significantly reduced, This is because the molding stability and the strength of the green molded body are impaired, and the effects of the present invention cannot be obtained.

In the composition of the present invention, in addition to the ethylene-vinyl acetate copolymer, the low-density polyethylene resin and the glycerin fatty acid ester-based wax, a plasticizer, a wax and the like commonly used in this type of composition are used. Further additions can be made. As the plasticizer, for example, dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DB)
P), di- (2-ethylhexyl) phthalate (DO
P), di-n-octyl phthalate (DnOP), diisooctyl phthalate (DIOP), diisobutyl phthalate (DIDB), diheptyl phthalate (DH)
P), diphenyl phthalate (DPP), diisodecyl phthalate (DIDP), ditridecyl phthalate (D
TDP), diundecyl phthalate (DUP), di (heptyl, noryl, undecyl) phthalate, benzyl phthalate, butyl benzyl phthalate (BBP), diisononyl phthalate (DINP), other various di-normal alkyl phthalates, alkyl benzyl phthalates (ABP), Dimethoxyethyl phthalate, dibutoxyethyl phthalate, dimethylcyclohexyl phthalate, dimethyl isophthalate (DMIP), di- (2-
Ethylhexyl) tetrahydrophthalate (DOT
P), phthalic acid-based plasticizers, such as ethylphthalylethyl glycolate (EPEG), and glycolic acid-based plasticizers, such as butylphthalylbutyl glycolate (BPBG); dibutyl adipate (DBA); dimethyl adipate (DMA) ), Di- (2-ethylhexyl) adipate (DOA), diisodecyl adipate (DIDA),
Diisobutyl adipate (DIBA), di (n-octyl, n-decyl) adipate, diisonoritsu adipate (DINA), benzyl octyl adipate, dibutyl diglycol adipate, di-n-alkyl adipate (DSA), di-n-alkyl (C6, C8, C10)
Adipate plasticizers such as adipate, di- (butoxyethoxyethyl) adipate, di (n-hexyl n-octyl n-decyl) adipate, di- (2-ethylhexyl) azelate (DOZ), di-n-hexyl Azelate (DNNZ), dimethyl azelate, dibenzyl azelate, dibutoxyethyl azelate (DBE
Azelaic acid plasticizers such as Z), di-n-butyl sebacate (DBS), di- (2-ethylhexyl) sebacate (DOS), dimethyl sebacate (DMS) sebacic acid plasticizer, di-2-ethylhexyl deca Dodecanoic acid-based plasticizers such as Nethioate (DODN) and 2-acid dimethyldodecane, di-n-butylmalate (DBM), dimethylmalate (DMM), diethylmalate (DEM), and di- (2- Maleic plasticizers such as ethylhexyl) malate (DOM) and di-n-butylfumarate (DBF); fumaric acid such as di- (2-ethylhexyl) fumarate (DOF) and di-n-butylfumarate Plasticizer, tri- (2-ethylhexyl) trimellitate (TOTM), tri-n-octyl trimellitate Triisodecyl trimellitate, tri-isooctyl trimellitate (TIOTM), higher alcohol trimellitate, trimellitic acid plasticizers such as linear trimellitate, triethyl citrate (TE
C), tri-n-butyl citrate, acetyl triethyl citrate, acetyl tri-n-butyl citrate (ATBC), acetyl tri- (2-ethylhexyl)
Citrate plasticizers such as citrate, monomethyl itaconate (MMI), monobutyl itaconate (MBI),
Itaconic acid-based plasticizers such as dimethyl itaconate (DMI), dibutyl itaconate (DBI), and di- (2-ethylhexyl) itaconate; oleic acid such as butyl oleate, glyceryl monooleate (GMO), and polyethylene glycol 200 monooleate And ricinoleic acid-based plasticizers such as methyl acetyl ricinoleate (MAR) and butyl acetyl ricinoleate (BAR).

As the wax, paraffin wax such as paraffin wax, microcrystalline wax, liquid paraffin, polyethylene wax of various molecular weights, montanic acid wax, stearic acid,
Fatty acid waxes such as hydroxystearic acid and complex stearic acid, hardened oils, stearamide, oxystearamide, oleylamide, erucylamide, laurylamide, partimineamide, behenamide, methylolamide, methylenebisstearamide, ethylenebisstearamide Amide, ethylenebisoleylamide, ethylenebislauramide, stearyloleylamide, N-
Fatty acid amide wax such as stearyl erucamide, N-oleyl palmitoamide, aliphatic or aromatic alcohol fatty acid ester wax, complex ester wax, higher alcohol wax, higher alcohol complex wax, glycerin fatty acid ester Wax, long-chain aliphatic compound, nonionic ester-based activator, low molecular weight polypropylene, block copolymer of ethylene oxide and propylene oxide, perfluoroalkyl betaine,
Examples include perfluoroalkylethylene oxide adducts, synthetic organic acid ester derivatives, nonionic activators, fatty acid diethanolamide, and the like.

[0024] The amount of these additives may be in the range commonly used in this type of composition.
20 parts by weight and wax may be added in the range of 1 to 20 parts by weight.

The composition of the present invention can be produced by appropriately selecting the above-mentioned components, blending them in a predetermined blending ratio, and uniformly kneading the mixture. The kneading method is not particularly limited. For example, using a universal mixing stirrer, a Banbury mixer or a pressure kneader, a single-screw or twin-screw extruder, or an appropriate device such as a kneading roll, at 120 to 180 ° C. By kneading for 30 to 120 minutes, a granulated composition in which the inorganic powder and the organic binder are uniformly mixed can be obtained.

Further, the obtained injection molding composition is injection-molded into a predetermined shape at a molding temperature of 80 to 120 ° C. and a mold temperature of 20 to 40 ° C. to obtain a green molded body. First, after inserting into a degreasing furnace, the temperature is raised at 5 to 20 ° C./h in a reducing atmosphere, maintained at a maximum temperature of 300 to 450 ° C. for 60 to 120 minutes, and then naturally cooled to obtain a primary degreased body. After the obtained primary degreased body is inserted into a sintering furnace, the temperature is increased in a vacuum atmosphere at 2.5 to 20 ° C./h, and the temperature is maintained at 500 to 700 ° C. for 30 to 60 minutes. After maintaining at the maximum temperature of 1200 to 1800 ° C. for 60 to 120 minutes, the final sintered body can be obtained by natural cooling.

The method and apparatus used at this time can be the methods and apparatuses that are usually employed.

[0028]

Next, an embodiment of the present invention will be described.

The types of materials used in Examples and Comparative Examples are as shown below.

A: Inorganic powder • Metal powder (1) Stainless alloy, SUS316L (trade name: MHTSUS316LH, manufactured by Mitsubishi Steel Corporation) • Metal powder (2) Carbonyl iron (trade name: Carbonyl iron, manufactured by ISP) • Ceramics Powder zirconia (trade name: TZ-3
B: Ethylene-vinyl acetate copolymer resin-EVA resin (1) Ethylene-vinyl acetate copolymer resin (trade name: Ultracene 681, manufactured by Tosoh Corporation, vinyl acetate copolymerization ratio: 20%) , MFR = 350) EVA resin (2) Ethylene-vinyl acetate copolymer resin (trade name: Ultracene 530, manufactured by Tosoh Corporation, vinyl acetate copolymerization ratio 6%, MFR = 75) C: polyethylene resin ・ PE resin low Density polyethylene resin (trade name: Sumikasen G808, manufactured by Sumitomo Chemical Co., Ltd.) D: Glycerin fatty acid ester-based wax ・ WAX (1) Glycerin monostearate (trade name: Riquemar S-100, manufactured by Riken Vitamin Co., Ltd.) ・ WAX (2) Glycerin monobehenate (trade name:
E: Other wax (paraffin wax)-PWAX (trade name: paraffin wax 125, manufactured by Nippon Seiro Co., Ltd.) (Example 1) 1) Mixing and preparation of composition As shown in Table 1, EV was added to 100 parts by weight of the metal powder (1).
A resin (1), 1 part by weight, low-density polyethylene resin, 3 parts by weight, and WAX (1), 4 parts by weight, were added and mixed by heating at 150 ° C. for 40 minutes using a universal mixing and stirring machine manufactured by Aikosha. By continuing the mixing and stirring for 1 hour while gradually cooling, a granular composition was obtained.

2) Injection molding method The obtained composition was subjected to an injection molding machine (model: JSW25SS2) manufactured by Nippon Steel Works Co., Ltd. to have a diameter of 20 mm × 20 mm.
mmH columnar test molded product, molding temperature 80-120
And a mold temperature of 20 to 40 ° C. to obtain a green molded body.

3) Primary degreasing method The obtained green compacts are arranged in a SUS container, buried with alumina powder having an average particle size of about 25 μm, inserted into a degreasing furnace, and then subjected to 20 ° C./h in a nitrogen stream atmosphere. And maintained at a maximum temperature of 450 ° C. for 60 minutes, and then naturally cooled to obtain a primary degreased body.

4) Secondary degreasing and sintering After removing the obtained primary degreased body from alumina powder, the primary degreased body is again aligned on an alumina plate, inserted into a sintering furnace, and then placed in a vacuum atmosphere at 10 ° C. / After heating at 700 ° C. for 60 minutes and maintaining at a maximum temperature of 1350 ° C. for 120 minutes, the final sintered body was obtained by natural cooling.

5) Evaluation Method (1) Evaluation of Moldability The 20 green molded articles obtained as described above were visually evaluated for appearance (4 points of sink marks, depressions, surface roughness, and cracks), and were evaluated for defects. Classification was made as follows according to the expression rate.

0/20 to 2/20 ○ 3/20 to 10/20 Δ 11/20 to 20/20 × (2) Evaluation of degreasing property The degreasing rate% of the obtained 20 green molded bodies was determined.
An average value of {= (molded article-degreased article) / (binder content in molded article) × 100} was obtained, and the appearance (swelling,
(2 points of deformation) were evaluated visually, and classified according to the defect occurrence rate in the same manner as in the above “Evaluation of formability”.

(3) Evaluation of Sinterability The average density of the obtained 20 sintered bodies was calculated by the dimensional weight method. Further, the appearance (two points of blisters and deformation) was visually evaluated, and classified according to the defect occurrence rate in the same manner as in the “formability evaluation method”. Table 2 shows the obtained evaluation results.

(Examples 2 to 11, 18 to 19) Table 1 shows the types and amounts of ethylene vinyl acetate copolymer and glycerin fatty acid ester wax and the amount of low density polyethylene resin added to metal powder (1). The compositions were added in the proportions shown, and processed in the same manner as in Example 1 according to the conditions shown in Table 1 to produce respective compositions and sintered bodies. Various evaluations were performed in the same manner as in Example 1. went.

Table 2 shows the obtained results.

(Examples 12 to 14) Metal powder (2) 10
Except that 0 parts by weight was used and the various conditions shown in Table 1 were used, the same treatment as in Example 1 was performed to produce a composition and a sintered body, and various evaluations were performed as in Example 1. Table 2 shows the obtained results.

(Examples 15 to 17) Ceramic powder 10
Except that 0 parts by weight was used and the various conditions shown in Table 1 were used, the same treatment as in Example 1 was performed to produce a composition and a sintered body, and various evaluations were performed as in Example 1. Table 2 shows the obtained results.

(Comparative Example 1) 4 parts by weight of a PE resin and 4 parts by weight of PWAX were added to 100 parts by weight of a metal powder (1), and treated in the same manner as in Example 1 under various conditions shown in Table 1 to obtain a composition,
A sintered body was manufactured and various evaluations were obtained in the same manner as in Example 1. Table 2 shows the obtained results.

(Comparative Examples 2 to 5) The compositions and sintered bodies were prepared by adding the components at the ratios shown in Table 1 and treating them under the various conditions shown in Table 1 in the same manner as in Example 1. Various evaluations were performed in the same manner as in Example 1. Table 2 shows the obtained results.

From these results, it can be seen that the composition of the present invention has less occurrence of defects even in a large-sized thick deformed product as compared with the conventional one, and a good final sintered product is obtained.

[0044]

[Table 1]

[0045]

[Table 2]

[0046]

According to the present invention, a resin and a wax are combined in a specific ratio with an inorganic powder, so that moldability,
It is excellent in degreasing property and sintering property and can provide a final sintered body having a high product commercialization rate, and a remarkable effect is recognized.

Claims (4)

[Claims] 1. An inorganic powder, 1 to 30 parts by weight of an ethylene vinyl acetate copolymer, 1 to 30 parts by weight of a low-density polyethylene resin, and 100 parts by weight of the inorganic powder.
A composition for injection molding of an inorganic powder, comprising -30 weight parts of a glycerin fatty acid ester wax. 2. When the inorganic powder is a metal powder,
1 to 30 parts by weight of metal powder and 100 parts by weight of the metal powder
The inorganic powder injection according to claim 1, comprising: 1 part by weight of an ethylene vinyl acetate copolymer; 1 to 30 parts by weight of a low density polyethylene resin; and 1 to 15 parts by weight of a glycerin fatty acid ester wax. Molding composition. 3. When the inorganic powder is a ceramic powder, the metal powder and 1 part by weight based on 100 parts by weight of the metal powder are used.
0 to 25 parts by weight of ethylene vinyl acetate copolymer;
The inorganic powder injection molding composition according to claim 1, comprising 30 parts by weight of a low density polyethylene resin and 8 to 25 parts by weight of a glycerin fatty acid ester wax. 4. An inorganic powder, 1 to 30 parts by weight of an ethylene vinyl acetate copolymer, 1 to 30 parts by weight of a low-density polyethylene resin based on 100 parts by weight of the inorganic powder,
After molding an inorganic powder injection molding composition comprising glycerin fatty acid ester-based wax by 30 to 30 parts by weight by injection molding, the molded body is subjected to a binder removal treatment and sintered. Characteristic sintered body.