JPH02206628A - Surface-treated alumina filler and resin composition containing the same - Google Patents

Abstract

PURPOSE:To obtain the subject material giving a composite material having excellent mechanical properties without causing remarkable loss of transparency when filled in an organic resin by surface-treating an alumina filler with a specific carboxylic acid compound and specifying the particle diameter, the specific surface area and the refractive index of the filler. CONSTITUTION:The objective material having particle diameter of 0.005-0.1mum, specific surface area of 30-300m<2>/g and refractive index of 1.6-1.7 is produced by surface-treating an alumina filler with an aromatic carboxylic acid compound containing polymerizable double bond (e.g. 4-methacryloxyethyl trimellitic anhydride). The surface-treatment of alumina filler with the above aromatic carboxylic acid compound is carried out e.g. by charging an alumina filler into a mixer such as Henschel mixer and adding a carboxylic acid compound to the filler under heating and stirring. The amount of the carboxylic acid compound is preferably 5-50 pts.wt. per 100 pts.wt. of the alumina filler.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to surface-modified alumina fillers.

Specifically, the present invention relates to an ultrafine alumina filler surface-modified using an aromatic carboxylic acid having a polymerizable double bond. The present invention also relates to a composition comprising the filler and an organic resin. The composition has various uses as reinforced plastics and adhesives.

It is useful as a coating agent, printing ink, composition for biological hard tissue (composition for vocal medicine), electromagnetic shielding agent, etc.

(Prior Art) Alumina is widely used in the industrial field, and is particularly useful as a filler for organic resins.

By the way, when used for such purposes, fillers are usually subjected to surface treatment. In this case, silane-based, titanium-based, zircoaluminate-based, phosphoric acid ester-based, carboxylic acid-based, etc. are known to be used as surface treatment agents, but among these, carboxylic acid-based surface treatment agents are particularly effective. It is known that

For example, JP-A-61. -162535 has the general formula (R1 is hydrogen or an alkyl group having 1 to 4 carbon atoms, 12 is an alkylene group having 1 to 6 carbon atoms, X is COO or O, and n is 1 or 2). A coupling agent for alumina shown in is disclosed, and it is stated that the particle size of the target alumina powder is 0.1 to 60 IJrn.
9ss), p. 445-459, there is a similar description by the same authors.

Japanese Patent Publication No. 60-3431 describes the general formula % (where ii is an alkylene group having 2 to 6 carbon atoms, i9 is a halogen-substituted derivative thereof, or a polyoxyethylene group or a polyoxypropylene group, & is a phenylene group or 7
An inorganic filler adsorbed and coated with a carboxylic acid compound represented by a tyrene group or an alkylene group or alkenylene group having 1 to 10 carbon atoms is disclosed. but,
In this document, there is no specific mention of the use of alumina (aluminum fermentation) as an inorganic filler.

However, if the surface-treated alumina filler described in the above-mentioned known documents is filled into an organic resin to produce a composite material, significant inconveniences may occur depending on the application.For example, the above-mentioned When filled with filler, the composite material becomes opaque.As a result, it is unsuitable for applications that require transparency, such as composite resins for dental restorations that require translucent beauty similar to natural teeth. .

Moreover, when filled into a photopolymerizable composition, curing by light irradiation becomes difficult. Furthermore, composite materials using coarse alumina fillers with a particle size of 0, IIIxn or more have another drawback in that their mechanical strength (particularly compressive strength) is inferior to that of silica fillers.

An object of the present invention is to provide an alumina filler that does not cause significant opacity even when filled into an organic resin and can provide a composite material with excellent mechanical strength. Another object of the present invention is to provide a resin composition filled with such an alumina filler.

(Means for Solving the Problems) In order to achieve the above object, the present inventors have repeatedly studied alumina fibers that have been surface-treated with a carvone-dispersed surface treatment agent. The present invention was completed after recognizing that the desired objective could be achieved by a combination of a carboxylic acid compound and an alumina filler having a limited particle size and refractive index.

That is, 1 the present invention is surface-treated using an aromatic carboxylic acid compound having at least one polymerizable double bond in the molecule, and the particle size range is greater than or equal to o, oos and less than 0, llln, Is the specific surface area between 30 and 300? and a resin composition containing the alumina filler.

One of the features of the present invention is that the particle size and refractive index of alumina are limited. The reason for this is to avoid opacity when filling the organic resin as described above.

Alumina, which is widely used in industry, is usually α-
This refers to alumina, and the refractive index of α-alumina is 1.
76 to 1.768. On the other hand, the refractive index of general-purpose resins is usually in the range of 1.40 to 1.65, and in resins in which α-alumina is dispersed, light scattering due to the difference in refractive index is large. This results in significant opacity.

The present inventors came up with the idea of using s Its η, θ type alumina for γ, δ, X%, which has a lower refractive index than the α-type,
It has been found that transparency can be maintained if the refractive index is in the range of 1.60 to 1.70. It is essential that the A/I/ONA used in the present invention has a refractive index in the range of 1.60 to 1.70, and there are no particular restrictions on the crystal form. Therefore, as long as the refractive index is within the range of 1.60-1.70, each crystal phase of ρ, η, and θ may be present alone in γ, δ, χ, or these crystal phases may be present alone. In o'l, which may contain a mixture of phases, it is also permissible for a small amount of α-phase to coexist.

In addition to the difference in refractive index between the filler and the resin matrix, the transparency of the composite material also depends on the particle size of the filler. That is, when the wavelength of light and the particle size are close to each other, the scattering of light increases, and conversely, the farther apart they are, the less the scattering of light decreases. That is, visible light region Q, 4. ctrn ~ 0.71 IPn, even if there is a difference in refractive index between the filler and the matrix.

It is possible to reduce the degree of light scattering and maintain transparency. Therefore, the Aldensu filler used in the present invention has a particle size range of o, oos to less than 0.1/a, and a specific surface area of 30 to 300 yV? Those within this range are preferably used. When the particle size is 0.11XQ, increasing the number of particles close to the visible region is not preferable because the transparency decreases beyond the permissible limit. On the other hand, if the number of particles having a particle size smaller than 0.005 mm increases, the viscosity of the resin composition increases significantly, resulting in a disadvantage that the filling resistance of the resin composition decreases. An alumina filler having a particle size of 0.005 to 0.05 gn is particularly preferred since it provides a resin with better transparency.

By the way, the refractive index of the alumina filler is determined using the Atsube refraction needle and the DIs (5890-96A) of the sodium vapor lamp.
Measurement is carried out using the immersion method using as a light source. Identification of crystal phase is X
This can be achieved by comparing the diffraction pattern of the - line with known data described, for example, on pages 27-28 of "Catalyst Handbook by Element" (edited by the Catalyst Society, published by Jihe Shokan, 1967). The particle size range can be easily determined by electron microscopic observation, and the specific surface area can be measured according to the BET method.

The alumina used in the present invention is obtained by a method of heating an alumina hydrated gel obtained by vapor-phase combustion of aluminum chloride, hydrolysis of an organic aluminum salt, or spark discharge in aluminum water at 400 to 1000°C.

As the carboxylic acid surface treatment agent used for the above-mentioned alumina filler, aromatic carboxylic acid compounds having at least one polymerizable double bond among the compounds that appear in known literature have a particularly large surface treatment effect. Useful.

The aromatic carbo/acid compound referred to here refers to the following general formula % [where n is an integer from 1 to 3, and when -COOH is bonded to adjacent positions, a carboxylic acid anhydride is formed. You may do so. In addition, -COOH may be in the form of an acid...rogenide -COX (where X is F, α, Br or engineering)] Compounds having one or more structural units represented by the following in the molecule: It is about.

A polymerizable double bond is a general formula (n is an integer of 2 to 20) [Here, R1, R2, R3 and R4 are hydrogen atoms, atoms,
・Rogen atoms represent organic groups] This means an olefinic double bond expressed as:

Specific examples of such aromatic carboxylic acid compounds include the following.

(n is an integer of 2 to 20) υ (n is an integer of 2 to 20) (n is an integer of 2 to 20) CH3 CH3 CH11 Hs -OCH2CHCH2-α-C-CI-hH3 The above carboxylic acid The method of modifying the surface of alumina filler (hereinafter untreated filler may be written as ^) using a compound is a common method for surface treatment of powder using a surface treatment agent. It can be carried out using methods known in the art, and can be roughly divided into wet methods and dry methods.

In the wet method, an alumina filler tube and a carboxylic acid compound are suspended in a slurry form in an appropriate amount of a solvent such as water, alcohol, hexane, benzene, toluene, xylene, etc., and thoroughly stirred. However, the optimal values for the conditions such as the solvent used, reaction temperature, reaction time, etc. vary depending on the combination of the alumina filler (^) and the carboxylic acid compound, but they can be easily found by an engineer of the relevant fractionator. After stirring for a predetermined period of time, the solvent is removed by distillation under reduced pressure, filtration, freeze drying, or the like to complete the surface treatment.

In this case, it is desirable to include a heating step in any of the processing steps. Heating is with alumina filler (6),
It is conceivable that this may be carried out while stirring the slurry consisting of the carboxylic acid compound and the solvent, or while the solvent is being distilled off. In some cases, the solvent may be further heated after distillation. In particular, heating in a suspended state with a solvent improves dispersibility.
The heating temperature for uniform surface treatment of the filler is 5.
Bonding at 0°C may cause a reaction.

Alternatively, an alkali metal salt, ammonium salt, or the like of the carboxylic acid compound may be used to react with the inorganic surface in a desalination reaction using the above-mentioned wet treatment method.

In the dry method, alumina filler (N) is placed in a mixer such as a Henschel mixer or a pump blender, and while stirring, the carboxylic acid compound is added as is or diluted with an appropriate solvent and sprayed. At this time, it is possible to stir while heating. Desirable. This method is suitable for processing large quantities of filler.

In any of the above treatment methods, the amount of carboxylic acid compound used for the alumina filler is preferably at least an amount that can cover most of the surface of the alumina filler with a monomolecular film of the carboxylic acid compound. This food is BET. It is possible to estimate from the value of the specific surface area of the alumina filler measured by the method etc. For example, as the particle size of the alumina filler decreases, the amount of carboxylic acid compound required increases. In the present invention, 1 to 100 parts by weight, more preferably 5 to 50 parts by weight, per 100 parts by weight of alumina filler.
Parts by weight are used. However, the optimum amount of the carboxylic acid compound to be used is determined based on experiments so that the desired physical properties of the resulting composition are maximized.

The amount of carboxylic acid compound attached to the alumina filler 4 is determined by elemental analysis of the surface-treated alumina filler.
It can be estimated by infrared analysis, etc.

By the way, it is also possible to obtain a composition by mixing a predetermined amount of the carboxylic acid compound into an organic resin and kneading alumina filler without surface treatment into the mixture. However, this method Compared to the method of the present invention, which uses alumina filler that has been surface-treated in advance, this method is undesirable because it is inferior in terms of filler dispersibility, the amount of filler packed into the organic resin, and the mechanical strength of the resulting composition.

In the composition of the present invention comprising the alumina and organic resin of the present invention surface-modified by the method described above, examples of the resin used include polyolefin resins such as polyethylene, polypropylene, polystyrene, and polyvinyl chloride, and polyvinyl chloride. General thermoplastic resins such as resin, polyacetal, and ABC resin can be mentioned. In this case, the resin is melted using a general mixing machine, and then the alumina filler of the present invention is added, mixed, and molded.

Furthermore, the alumina filler of the present invention is kneaded as an organic resin with a polymerizable monomer to provide a polymerizable composition. The polymerizable monomer used in this case is appropriately selected depending on the use of the composition, but one that can be copolymerized with the carboxylic acid compound used as a surface treatment agent is used, and usually (meth)acrylate monomer [ The notation "(meth)acrylate" means both methacrylate and acrylate] is used.

In addition to these, there are also esters with monohydric or dihydric alcohols such as α-cyanoacrylic acid, crotonic acid, cinnamic acid, sorbic acid, maleic acid, and itaconic acid, and (meth)acrylamides such as N-isobutylacrylamide. , vinyl esters of carboxylic acids such as vinyl acetate, vinyl ethers such as butyl vinyl ether,
Mono N-vinyl compounds such as N-vinylpyrrolidone, styrene derivatives, and the like may also be used.

An example of a (meth)acrylate monomer is methyl (
meth)acrylate, lauryl(meth)acrylate,
Monofunctional (meth)acrylates such as dimethylaminoethyl (meth)acrylate, triethylene glycol di(meth)acrylate, 1,10-decanediol di(
meth)acrylate, bispheno-#A di(meth)acrylate, 2,2-bis[(meth)acryloyloxypolyethoxyphenyl]propa7.2.2-bis(4-
(3-methacryloxy-2-hydroxypropoxy)7
Enylpropane (sometimes called Big-GMA)
Bifunctional (meth)acrylates such as, trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate
List of tetrafunctional (meth)acrylates such as acrylate, pentaerythritol tet 2(meth)acrylate, adduct of 1 mol of 2,2.4-)dimethylhexamethylene diisocyanate and 2 mol of glycerin di(meth)acrylate. Can be done. These monofunctional and polyfunctional (
Meth)acrylates may be used alone or in combination of two or more.

In the composition of the present invention, the mixing ratio of the surface-modified alumina filler and the organic resin varies greatly depending on the application, but usually the surface-treated alumina filler is 1 part by weight to 900 parts by weight per 100 parts by weight of the organic resin. More preferably, it is in the range of 10 parts by weight to 400 parts by weight.

In the composition of the present invention, in addition to the alumina filler,
Furthermore, it is also possible to add other fillers as necessary. The filler may be either inorganic or organic, and examples of the inorganic filler include quartz, amorphous silica,
Examples include inorganic fillers containing silica as a main component, such as borosilicate glass.

These fillers are used after surface treatment with a hasilane coupling agent in advance. On the other hand, examples of organic fillers include polymer powders such as polymethyl methacrylate, polyvinyl chloride, and polystyrene, and organic-inorganic composite fillers as disclosed in JP-A-56-49311. When a polymerizable monomer is used as the organic resin, the composition of the present invention can be heated to 100°C or higher or subjected to an operation of applying energy from the outside, such as by irradiating it with an electron beam. It can be converted into a molded product by polymerization and curing, but polymerization and curing are often facilitated by adding a polymerization initiator.

The polymerization initiator used in the present invention is not particularly limited and may be any known one, but is usually selected in consideration of the polymerizability of the polymerizable monomer and the polymerization conditions. For example, when (meth)acrylate is polymerized by heating, organic peroxides such as benzoyl peroxide (referred to as BPO) and cumene hydroperoxide, and compounds such as 2,2-azobisisobutyronitrile are preferably used. It will be done.

On the other hand, when performing room temperature polymerization, benzoyl peroxide/dimethylaniline system, organic sulfine Wl/:(
In addition to oxidation-reduction initiators such as those based on amines and peroxides (or their salts), tributylborane, organic sulfinic acids, and the like are also suitably used.

On the other hand, when photopolymerization is performed by irradiation with visible light, α
Preferred are oxidation-reduction systems such as -diketone/tertiary amine, α-diketone/aldehyde, α-diketone/mercaptan. α-diketones include can-7-arkynones, 2.
Tertiary amines such as 3-pentanedione and benzyl include N,N-dimethylaminoethyl methacrylate, N
, N-dimethylami7benzoic acid ether, etc.; aldehydes include laurylaldehyde, p-octyloxybenzaldehyde, etc.; mercaptans include thiosalicylic acid, 2-mercaptobenzoxazole, etc. Furthermore, an α-diketone/organic peroxide/reducing agent system in which an organic peroxide is added to these oxidation-reduction systems is also preferably used.

When photopolymerizing by ultraviolet irradiation, 2,4,6-dolimethylpenzoyldiphenylphosphine oxide,
In addition to benzoin methyl ether, benzyl dimethyl ketal, 2-methylthioxanthone, and the like, the above visible light photopolymerization initiators are also suitably used.

The appropriate amount of these polymerization initiators to be added is in the range of 0.01 to 10 g based on the polymerizable monomer.

(Examples) Next, the present invention will be explained by examples, but the present invention is not limited to these examples. The definitions and measurement methods of various quantities in the following Examples are summarized at the end of the text.

Example 1 Average particle size 0.02 sits, BET specific surface area to y
t, alumina powder with a refractive index of 1.65 (alkinium oxide CO manufactured by Nippon Aerosil Co., Ltd. The crystal phase of this product is a mixture of δ phase and θ phase) 20f, 4-methacryloxyethyl trimellitic anhydride (see below) (hereinafter referred to as 4-, META) A mixture of 42 and 350 d of toluene was heated under reflux for 2 hours.

Next, the alumina powder was recovered by centrifugation, and 2
After drying for 4 hours, it was further dried at 90°C for 2 hours to completely remove toluene.

Elemental analysis of this surface-modified filler revealed that 88.3% of ash remained, il, 7% of 4...M
It was found that ETA was deposited on the filler surface.

On the other hand, 2,2-bis(methacryloyloxypolyethoxyphenyl)globan (with an average of 2,6 ethoxy groups in the molecule)
70tli, which is called D-2゜6E)
h-lyethylene glycol dimethacrylate (hereinafter 3)
G) and 1 part by weight of benzoyl peroxide were mixed and dissolved to obtain a polymerizable monomer composition.

100 parts by weight of the surface-modified alumina filler and 100 parts by weight of the polymerizable monomer composition were mixed to obtain a polymerizable composition. This composition was polymerized and cured by heating at 130° C. for 30 minutes.

The results of measuring the compressive strength and transparency (ΔL) are shown in Table 1. Comparative Example 1 α-Alumina powder 10 f, 4-MIETA 012f and Ace) with an average particle size of 0.4 μm and a BET specific surface area of 5.5 u 10sII'! ii Acetone was then distilled off using an evaporator to obtain a surface-modified filler. Table 1 also shows the results of a similar evaluation of a composition v4 produced using this filler and the same polymerizable monomer composition as in Example 1 and at the same composition ratio.

Table 1 Example 2 In the polymerizable monomer composition used in Example 1, instead of 1 part by weight of benzoyl peroxide as a polymerization initiator, 0.7 part by weight of Farquinone and 4-N,N-dimethyl were added. A photopolymerizable monomer composition was prepared by adding 1.0 parts by weight of ethyl aminobenzoate. Using this and the surface-modified filler of Example 1, a photopolymerizable composition was prepared with the composition ratio of Example 1. This composition (paste form) was poured into a 10-layer plate with a thickness of 4 ssi holes. The bottle was placed in a mold, the upper part was pressed against a slide glass, and in this state, light was irradiated for 90 seconds using a xenon lamp (Kurturer 31J Denta color XS). When the cured product was removed from the mold and the cure depth was measured, it was found that it had been cured to the bottom, and the cure depth was 10- or more.

Comparative Example 2 A composition having the composition ratio of Example 1 was prepared using the polymerizable monomer composition of Example 2 and the surface-modified filler of Comparative Example 2, and the same curing test as in Example 2 was conducted. Do the hardening #! When I measured the degree, it was only 1.2 cm.

Examples 3 to 11 and Comparative Examples 3 to 5 In Example 1, the surface treatment agent shown in Table 2 was used instead of 4-META to modify the surface of alumina powder. The compressive strength and transparency of a composition using these fillers (prepared with the composition ratio of Example 1) were measured, and the results are listed in Table 2.

Example 13 Glass powder (GM-31684, manufactured by Schott) was crushed and classified to obtain powder with an average particle size of 2.3A1rn. A surface-modified glass filler was obtained by a conventional method using 2 parts by weight of γ-methacryloyloxyglobyltrimethoxysilane based on 100 parts by weight of this powder.

Next, 11 parts of D-2,6E 40t as a polymerizable monomer,
25 parts by weight of 3G, 35 parts by weight of an adduct of 1 mole of 2,2.4-toIJ methylhexamethylene diisocyanate and 2 moles of glycerin dimethacrylate, and 2.4.6-1-samethylbenzoyl as a photopolymerization initiator. 1 part by weight of diphenylphosphine oxide was mixed and dissolved to obtain a polymerizable monomer composition.

400 parts by weight of the glass filler, 100 parts by weight of the polymerizable monomer composition, and 150 parts by weight of the surface-modified alumina filler obtained in Example 3 were mixed to obtain a polymerizable composition.

This composition was photopolymerized for 90 seconds using the xenon lamp irradiator used in Example 1, and then heated at 120°C for 20 minutes. The compressive strength of the resulting cured product was measured to be 4620 V-, and the transparency ( The material had a mechanical strength and aesthetic properties suitable for use as a dental composition, particularly as a substitute material for a tooth crown defect. Note that the definitions and measurement methods of various quantities in the examples described above are as shown below.

(1) Average particle size and particle size range For ultrafine powders of 0.1p or less, determination was made by measurement from transmission electron micrographs and conversion from specific surface area measured by BET method. Q.For fillers larger than 11#, use Horiba's automatic particle size distribution analyzer CA.
The measurement was performed using a PA500 model. The measurement principle is a light transmission centrifugal sedimentation method (combined with natural sedimentation).

cii) Pour the compressive strength paste into a cylindrical mold with a diameter of 4W% and a height of 4m,
After polymerization and curing according to the prescribed method, remove from the mold and heat at 37°C.
, immersed in water for 24 hours and tested at a crosshead speed of 2 ta, / mtn using an Instron universal testing machine.
It was measured with Measured values are average values of 10 samples.

(III) Transparency (ΔL) A cured product (disc-shaped with a diameter of 30 mm and a thickness of 0.85 mm) that was polymerized by a predetermined method was used as a sample. Brightness when measuring chromaticity by placing a standard white board behind the test piece using a color difference meter (Nippon Denshoku Σ80 powder)
Ll) and the lightness (L2) when the chromaticity was measured by placing a standard blackboard behind the same test piece, the difference ΔL=Ll−L2 was measured and used as an index of transparency. In this evaluation method, the larger the value of ΔL, the higher the transparency.

(The refractive index of the thick filler was measured by the immersion method using an Atsube refractometer, using the D line of a sodium lamp as a light source, and using short methane, bromonaphthalin, methyl salicylate, etc. in which sulfur was dissolved as a solvent.

(Effects of the Invention) The surface-modified alumina filler of the present invention is contained in an organic resin (the compounded composite material has excellent mechanical strength, gloss, and transparency, and is used not only as an industrial molding material but also as a craft material). It is also useful as a dental material.

Patent applicant RiRashi Co., Ltd.

Claims (2)

[Claims] (1) The surface is treated with an aromatic carboxylic acid compound having at least one polymerizable double bond in the molecule, the particle size range is 0.005 μm or more and less than 0.1 μm, and the specific surface area is 30 μm. or 300 m^2/g and a refractive index of 1
．． An alumina filler characterized by having an alumina filler in a range of 60 to 1.70. (2) surface-treated with an aromatic carboxylic acid compound having at least one polymerizable double bond in the molecule, the particle size range is 0.005 μm or more and less than 0.1 μm;
A resin composition comprising an alumina filler and an organic resin having a specific surface area of 30 to 300 m^2/g and a refractive index of 1.60 to 1.70.