Binder for firing and method for manufacturing the same

Abstract

This improves the decomposition performance and printability of conventional binder compositions for firing. [Solution] A binder composition for firing containing an acrylic polymer (A) and ethylcellulose (B), wherein the acrylic polymer (A) is synthesized using a polyfunctional initiator in the presence of ethylcellulose (B).

Description

Technical Field

[0001] The present invention relates to a binder composition for firing and a method for producing the same.

Background Art

[0002] Binders for firing used to form fired bodies of inorganic powders are used in many fields. For example, they are used in the processes of creating electrodes, conductor wirings, multilayer capacitors, etc. in various electronic devices. In order to obtain a desired shape in the printing process when obtaining these electronic devices, a composition containing a binder is used. Thereafter, upon heating when sintering the inorganic powder, the binder undergoes thermal decomposition and does not remain in the electronic component.

[0003] Such binders for firing are desired to be thermally decomposed during firing without leaving residues. Furthermore, when used in the field of electronic devices, they often go through a printing process and are desired to have excellent printing characteristics.

[0004] In recent years, various electronic components have been miniaturized, so an improvement in printing performance is required. Furthermore, since the temperature during firing is desired to be lowered, a binder composition for firing that is excellent in thermal decomposability and has less residue is desired.

[0005] Patent Document 1 describes a binder composition for firing obtained by polymerizing a monofunctional acrylic monomer and a polyfunctional acrylic monomer in the presence of ethyl cellulose. Patent Documents 2 and 3 describe an inorganic particle dispersion paste containing ethyl cellulose and an acrylic polymer. Patent Document 4 describes that in a viscosity index improver, polymerization is carried out using a polyfunctional initiator.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

[0007] The present invention aims to improve the decomposition performance and printability of conventional binder compositions for firing. [Means for solving the problem]

[0008] The present invention relates to a binder composition for firing containing an acrylic polymer (A) and ethylcellulose (B), characterized in that the acrylic polymer (A) is synthesized using a polyfunctional initiator in the presence of ethylcellulose (B).

[0009] The above-mentioned binder composition for firing preferably has a mass ratio of acrylic polymer (A) to ethyl cellulose (B) in the range of (A):(B) = 95:5 to 60:40. The above-mentioned acrylic polymer (A) preferably has a weight-average molecular weight of 300,000 to 1,000,000 and a glass transition temperature in the range of -10 to 40°C. When polymerizing the above acrylic polymer (A) in the presence of ethylcellulose, it is preferable that it is polymerized by suspension polymerization.

[0010] The present invention also relates to a method for producing a binder composition for firing, characterized by comprising the step of polymerizing acrylic monomers by suspension polymerization in the presence of ethyl cellulose (B) using a polyfunctional initiator. [Effects of the Invention]

[0011] The binder composition for firing according to the present invention has superior decomposition and printing performance compared to conventional products. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below. Traditionally, ethylcellulose has been used as a binder for firing in the printing industry. However, this method has been problematic due to the generation of ethylcellulose residue during firing. To address this issue, attempts are being made to use acrylic polymers in combination with ethylcellulose, which tend to produce less residue.

[0013] However, the use of acrylic polymers tended to degrade printing performance. To improve this, the use of acrylic polymers polymerized in the presence of ethylcellulose was also considered. Even with such compositions, it was not possible to achieve a high level of both thermal decomposition performance and printing performance.

[0014] In binders for firing that contain acrylic polymers, increasing the molecular weight of the acrylic polymer can improve printing performance. However, when using polyfunctional monomers to create a resin with a high molecular weight, it is necessary to use a relatively large amount of polyfunctional monomers, which can negatively affect thermal decomposition performance.

[0015] Focusing on this point, the present invention uses a polyfunctional initiator to produce a resin with a high molecular weight. When a polyfunctional initiator is used, a relatively small amount can be used to efficiently increase the molecular weight. Therefore, it is possible to achieve a high level of balance between printability and thermal decomposition properties.

[0016] Furthermore, in the present invention, it is preferable that the acrylic polymer is obtained by suspension polymerization. Polymers obtained by suspension polymerization are also preferable because they have a higher molecular weight compared to those obtained by solution polymerization in an organic solvent. The components of this invention will be described in detail below.

[0017] (Acrylic polymer) The acrylic polymer in the present invention is obtained by polymerization in the presence of ethyl cellulose. When the acrylic polymer is polymerized in the presence of ethyl cellulose, the two polymers are better compatible than in the case of normal mixing, and the characteristics of both are well expressed. Also, it is preferable in terms of excellent stability. As a result, particularly excellent effects can be obtained when used as a binder for firing.

[0018] The polymerization of the acrylic polymer needs to be polymerization using a polyfunctional initiator. This is preferable in that a resin composition excellent in both decomposition performance and printing performance can be obtained.

[0019] The polyfunctional initiator is not particularly limited, and 1,1-bis(1,1-dimethylethylperoxy)cyclohexane, 1,1-bis(tert-hexylperoxy)cyclohexane, 1,4-bis[(t-butylperoxy)isopropyl]benzene, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, 2,2-bis[4,4-bis(isobutylperoxy)cyclohexyl]propane, 3,3’,4,4’-tetrakis(tert-butylperoxycarbonyl)benzophenone, etc. can be used.

[0020] The amount of the polyfunctional initiator used is not particularly limited, and it is preferably 0.1 to 1.0% by mass based on the mass of the monomer used as a raw material for the acrylic polymer. It is preferable in that the above-mentioned object can be sufficiently achieved within the above range. If the amount of the polyfunctional initiator used exceeds the above range, the molecular weight of the polymer may become small, and there is a risk that the desired performance cannot be obtained.

[0021] The lower limit of the amount of the polyfunctional initiator used is more preferably is 0.05% by mass, and even more preferably 0.1% by mass. The upper limit of the amount of the polyfunctional initiator used is more preferably 1% by mass, and even more preferably 0.5% by mass.

[0022] The monomers constituting the above-mentioned acrylic polymer are not particularly limited, and various monofunctional acrylic monomers can be used. The monofunctional acrylic monomers are not particularly limited, but examples include methyl methacrylate, hydroxyethyl methacrylate, butyl methacrylate, isobutyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, ethyl methacrylate, glycerin monomethacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 1,4-cyclohexanedimethanol monoacrylate, 2-hydroxy-2-methylpropyl methacrylate, and polypropylene glycol monomethacrylate (n≒4~13), which can be used alone or in combination of two or more.

[0023] In the present invention, polyfunctional acrylic monomers with two or more functions may be used, provided that they do not adversely affect performance. However, if the amount of polyfunctional acrylic monomer used is too large, it may adversely affect the thermal decomposition performance. For this reason, even when used, the amount used is preferably 1.0% by mass or less.

[0024] The acrylic polymer (A) of the present invention is preferably obtained by suspension polymerization. Acrylic polymers obtained by suspension polymerization are high molecular weight polymers, and since the polymer can be obtained in powder form, they are preferable in that they do not require a specific type of solvent for use.

[0025] The acrylic polymer (A) described above preferably has a weight-average molecular weight in the range of 300,000 to 1,000,000. This range suppresses phase separation between polymers, leading to improved binder stability. It also contributes to higher viscosity of the binder, which is preferable as it improves printing properties.

[0026] The lower limit of the molecular weight is more preferably 300,000, and even more preferably 340,000. The upper limit of the molecular weight is more preferably 1,000,000, and even more preferably 800,000.

[0027] The above acrylic polymer (A) was obtained by polymerization in the presence of ethyl cellulose (B). This method is preferable because it improves the compatibility between the polymers, leading to improved printing properties and storage stability.

[0028] In the polymerization of such an acrylic polymer (A), it is preferable to use ethylcellulose (B) in a proportion of 5 to 40% by mass relative to the total amount of (A) and (B). This proportion is preferable because it allows the physical properties of ethylcellulose to be exhibited while maintaining the high degradability characteristic of acrylics, as the acrylic polymer is the main component, and thus provides high performance as a binder. In the above ratio, the lower limit of the amount of ethylcellulose (B) is more preferably 5% by mass, and even more preferably 20% by mass. The upper limit of the amount of ethylcellulose (B) is more preferably 30% by mass, and even more preferably 40% by mass. The suspension polymerization method described above is not particularly limited and is carried out using a general surfactant.

[0029] Through this polymerization, a mixture of (A) and (B) can be obtained as a powdery precipitate. Therefore, by mixing this mixture with other necessary components, a binder composition for calcination can be obtained.

[0030] The firing binder composition of the present invention can be prepared by mixing it with inorganic powder and other necessary components to create a firing composition. Such a firing composition can be prepared by firing it after various molding processes to produce a fired product.

[0031] Particularly preferable is to print the ink composition using known printing methods, and then decompose the binder by firing to form a ceramic molded product. This method allows the product to be used in the manufacture of electrodes, conductive wiring, multilayer capacitors, and the like in various electronic devices.

[0032] Ink compositions used for such purposes may contain other components in addition to the polymers described above. Other components that can be included include solvents, inorganic powders, dispersants, plasticizers, lubricants, and the like.

[0033] (solvent) The solvents that can be used in the above ink composition are not particularly limited, and examples include butyl carbitol, butyl carbitol acetate, terpineol, dihydro terpineol, dihydro terpinyl acetate, texanol, benzyl alcohol, ethylene glycol, butyl glycol, 1,4-butanediol, hexyl acetate, dipropylene glycol, tripropylene glycol, propylene glycol monomethyl ether, and propylene glycol monomethyl ether.

[0034] In such an ink composition, the firing binder composition of the present invention is preferably blended in a proportion of 3 to 10% by mass relative to the total amount of the ink composition. Adding it within this range is preferable because it allows for the acquisition of appropriate printing characteristics.

[0035] As the inorganic powders mentioned above, appropriate powders are used depending on the application. For example, as inorganic powders, gold, silver, copper, nickel, palladium, ITO, alumina, zirconia, titanium oxide, barium titanate, aluminum nitride, silicon nitride, boron nitride, various glass powders, inorganic phosphors, graphite powder, solder powder, etc., are used individually or in combination of two or more types.

[0036] The ratio of the firing binder composition to the inorganic powder in the firing paste is adjusted as appropriate so as to maintain good applicability of the firing paste and good properties of the various elements obtained by sintering the firing paste. For example, it is preferable that the ratio of inorganic powder to 100 parts by mass of the firing binder composition is in the range of 20 parts by mass to 4000 parts by mass.

[0037] When the firing paste is used, it is first applied to the appropriate object. The application method is not particularly limited, but examples include screen printing, dispensing, and doctor blade methods. According to this embodiment, the application properties of the firing paste are improved, a coating of a certain thickness is easily formed, and the so-called stringing phenomenon is less likely to occur during application.

[0038] Next, if necessary, the firing paste is heated, causing the solvent in the paste to volatilize and some or all of the binder, which is an acrylic polymer and ethyl cellulose, to decompose and be removed. Further firing of the firing paste removes any remaining binder and sintersects the inorganic powder. This forms appropriate elements such as electrodes and conductive wiring. [Examples]

[0039] The present invention will be described in detail below based on the following examples. However, the present invention is not limited to the following examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0040] Example 1: Preparation of Binder Composition A 1L flask equipped with a stirrer, condenser, thermometer, and nitrogen gas inlet was prepared. Deionized water was added to the flask and a surfactant was dissolved. Acrylic monomer, initiator, and chain transfer agent were added to this deionized water to obtain a monomer dispersion solution. Simultaneously, nitrogen was blown into the upper part of the liquid to remove oxygen from the system. Next, ethyl cellulose was added to this dispersion solution and heated to 60°C using an oil bath, and stirred to dissolve the ethyl cellulose in the monomer. After dissolution and dispersion, the system was heated to 90°C and the polymerization reaction was carried out for 4 hours. The obtained polymer was washed with deionized water and dried to obtain polymer beads. The obtained polymer beads were dissolved in various solvents, and the resulting resin solutions were used for evaluation.

[0041] (Manufacturing of ink compositions) Ni paste was prepared by adding 46% ultrafine Ni powder (JFE Minerals Corporation, NFP201S), 4.6% TiBaO3 (Sakai Chemical Industry Co., Ltd., KZM-100) as a co-material, 45.8% terpineol as a solvent, 0.6% dispersant (Kyoeisha Chemical Co., Ltd., Flownon G-700), and 3.0% binder, and dispersing them using a three-roll mill (EXAKT Corporation, model number: EXAKT80E).

[0042] The binder and ink compositions obtained in this manner were evaluated according to the following criteria. The results are shown in Table 1 below.

[0043] (Evaluation method) (Weight average molecular weight) Measurements were performed using a GPC instrument (Shodex, model number: GPC101) with a column (LF-804) and THF as the developing solvent. Molecular weight was measured in polystyrene equivalent.

[0044] (compatibility) The calcination binder was dissolved in terpineol at a solid content of 20%, and after standing, the appearance was evaluated. A clear, unclouded solution was marked with ○, a solution with cloudiness with △, and a solution that was completely separated with ×.

[0045] (Long term stability) The calcination binder was dissolved in terpineol at a solid content of 20%, and the solution was left at room temperature for one month and then at 50°C for 24 hours. The appearance of the solution was then measured for any changes. A circle (○) indicated no change, a triangle (△) indicated turbidity, and a cross (×) indicated complete separation.

[0046] (Coating property) Using an applicator (BEVS, model number: 1803 / 80 / 4), 5g of the sample was applied to a glass plate (100mm x 200mm x 1mm). The coating was then dried at 130°C for 3 hours, and the appearance of the coating after drying was visually inspected and evaluated. A uniform coating surface without any dents or unevenness was marked with ○, while defects such as dents or unevenness were marked with ×.

[0047] (pyrolysis temperature) A differential thermal analyzer (Rigaku Corporation, model number TG-DTA8122) was used to measure the weight change of the firing binder while heating it from room temperature to 500°C at a heating rate of 10°C / min under a nitrogen atmosphere. Based on the measurement results, a weight loss rate of 95% or more of the firing binder was evaluated as ○, and less than 95% as ×.

[0048] (viscosity) Measurements were taken using an E-type viscometer (Antonpaar, model number: MCR-302) at a temperature of 25°C and a rotation speed of 6 rpm. The unit is expressed in mPa·s.

[0049] (Stringability) A cylindrical measuring jig with a radius of 0.5 mm was impregnated 3 mm into a firing binder solution using a rheometer (manufactured by Sun Chemical Co., Ltd., model number: CR-500DX). The distance at which the string broke was measured when the jig was then pulled up at 600 mm / sec. A result of ○ was given if the string broke within 5 mm, △ if it broke between 5 and 10 mm, and × if it broke more than 10 mm.

[0050] (Ni paste viscosity) Viscosity was measured using an E-type viscometer (Antonpaar, model number: MCR-302) at 25°C and a rotation speed of 10 rpm. The unit is expressed in mPa·s.

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] [Table 4]

[0055] From the results shown in Tables 1-4 above, the binder composition for firing according to the present invention exhibits excellent thermal decomposition and printability. [Industrial applicability]

[0056] The firing binder composition of the present invention can be suitably used as a binder when preparing printing inks for metals and ceramics such as electronic components and capacitors (LTCC).

Claims

1. A binder composition for firing containing an acrylic polymer (A) and ethylcellulose (B), A binder composition for firing, characterized in that the acrylic polymer (A) is synthesized using a polyfunctional initiator in the presence of ethyl cellulose (B).

2. The firing binder composition according to claim 1, wherein the mass ratio of the acrylic polymer (A) to the ethyl cellulose (B) is in the range of (A):(B) = 95:5 to 60:

40.

3. The acrylic polymer (A) has a weight-average molecular weight of 300,000 to 1,000,000 and a glass transition temperature in the range of -10 to 40°C, as described in claim 1 or 2.

4. The binder composition for firing according to claim 1 or 2, wherein the acrylic polymer (A) is polymerized by suspension polymerization in the presence of ethyl cellulose.

5. A method for producing a binder composition for firing, characterized by comprising the step of polymerizing acrylic monomers by suspension polymerization in the presence of ethyl cellulose (B) using a polyfunctional initiator.

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