KR100250376B1 - Heat-sensitive recording papers comprising amorphous silica-type filler - Google Patents

Abstract

PURPOSE: Provided is a heat-sensitive recording paper, which contains an amorphous silica filler having excellent handling property, processability and dispersion property, and shows low ground fogging and improved image concentration. CONSTITUTION: The heat-sensitive recording paper is coated with a silica filler comprising amorphous silica in an amount of 5 to 60 wt% on the solid content basis. The amorphous silica has an average primary particle diameter(D1) of 100 to 270 nm as determined by a scanning electron microscope, an apparent specific gravity of 0.24 to 0.55 g/cm¬3, a specific surface area of 200 to 500 m¬2/g, a silica elementary particle diameter(DO) of 5 to 15 nm, and an agglomeration degree(DA) defined as the ratio of D1/DO of 10 to 50.

Description

Heat sensitive recording paper containing amorphous silica type filler {HEAT-SENSITIVE RECORDING PAPERS COMPRISING AMORPHOUS SILICA-TYPE FILLER}

The present invention provides amorphous silica fillers, more particularly excellent handleability and processability, when added to a resin film, excellent dispersibility, transparency and anti-sticking properties, and the surface is not scratched even when the films are rubbed together. A non-crystalline silica type filler that provides a resin film having excellent scratch-resistant properties.

The present invention also relates to a filler for heat-sensitive recording paper, and more particularly to forming a vivid image without blur on the bottom of the heat-sensitive recording paper, and to heat-sensitive recording paper without depositing residue on the heat head. The present invention relates to an amorphous silica filler for thermosensitive recording paper which is excellently applied to a phase.

(Explanation of Prior Art)

Amorphous silica type fillers include so-called dry silica and wet silica, and are used for paint, information recording paper, rubber, resin molded products and other uses according to their properties.

The amorphous silica exhibits a wide variety of properties depending on the preparation method. In particular, wet-method amorphous silica exhibits a wide variety of properties when changing conditions such as concentration, temperature, pressure, time and reaction method in the step of neutralizing alkali silicate with acid.

For example, silica hydrogels obtained by gelatinizing a silica sol formed by neutralizing an alkali silicate with an acid in a short time (spraying with a gaseous medium) (Japanese Patent Publication No. 13834/1973, Japanese Patent Publication No. 16049 / 1988), and hydrated silica gel having a water content of 20 to 50% by weight, obtained by washing the acid-cured silica hydrogel with acid to obtain a silica hydrogel having a pH of 2.5 to 5, followed by drying and grinding Japanese Patent Publication No. 1764/1990) is known.

In addition to the above-mentioned amorphous silica, fine inorganic particles have been widely used as an anti-sticking agent for resin films. For example, a method of adding fine powdered silica in which silanol groups on the surface of silica are substituted with oleophilic groups to resin to improve transparency and anti-sticking (Japanese Patent Publication No. 41099/1974), biaxially Method of improving the anti-sticking property by adding zeolite particles to an undrawn polypropylene film (Japanese Patent Publication No. 16134/1977), and having a specific specific gravity of 0.1 to 0.2 g / cm ³ and specific surface area An elongated polypropylene film (Japanese Patent Publication No. 58170/1988) has been proposed, in which fine powder silica having a) of 150 m ² / g or less is added to improve transparency, slippage and anti-sticking properties.

In addition, thermal recording paper has been used in facsimile machines, printers, data information exchanges, computer terminals, measuring instruments and copiers using thermal heads, heat pens, infrared lamps or lasers as heat sources. A recording layer contains in the binder a colorant such as a pigment and a color coupler such as phenol, which exhibits color upon high temperature contact with the colorant.

When recording on thermally sensitive recording paper by heat, the recording head portion is brought into contact with the recording layer. At this time, the components in the recording layer are melted and sticky, resulting in sticking to the recording head portion, resulting in an adhesive phenomenon. In order to avoid the above problem, various fillers were included in the recording layer. However, when amorphous silica was put into the recording layer as a filler for thermosensitive recording paper, the surface activity of the silica promoted the reaction between the leuco pigment and the phenol, resulting in ground coloration (that is, blurred background).

In order to avoid the above problems, the present inventors include fine particulate amorphous silica having a secondary particle size distribution in which particles having a particle size of 4 μm or less are contained in an amount of 90% by weight or more of the total weight as measured by centrifugal sedimentation. In addition, Japanese Patent Publication No. 1030/1990 has proposed a filler for thermosensitive recording paper having a BET specific surface area of 10 to 100 m ² / g and a bulk density of 0.14 to 0.30 g / ml. .

(Summary of invention)

It is an object of the present invention to provide amorphous silica type fillers with excellent handleability, processability and dispersibility and less damage to the apparatus due to friction. In addition, the present invention imparts excellent anti-blocking property (AB property) to the resin film, exhibits excellent dispersibility and transparency, and provides excellent scratch resistance to the film surface, even when the films are rubbed together. Provided is an amorphous anti-sticking agent for a resin film that is not scratched, and provides a thermoplastic resin film using the anti-sticking agent.

Amorphous silica has been widely used as an anti-sticking agent for resin films, because the resin film mixed with amorphous silica shows excellent anti-sticking properties and transparency. However, insufficient dispersibility and film defects such as fisheyes and voids still remained. Therefore, there has been a need for a method of eliminating the defect and further improving the anti-sticking properties and transparency.

The reason why a film mixed with amorphous silica exhibits improved anti-sticking is that amorphous silica particles distributed on or near the surface of the film create a gap between the film surface. However, when the films are rubbed with each other, the film surface is scratched by the polishing of amorphous silica. In particular, the higher the anti-sticking property of amorphous silica, the greater the tendency of the film to be scratched by friction.

Furthermore, the conventional amorphous silica used in the above-mentioned applications is in the form of fine powder with a small apparent specific gravity and bulky, and is difficult to handle because it is a powder. In addition, the amorphous silica is so large in volume that it lacks processability and dispersibility when mixed with the resin.

The inventors have studied the experimental law between the specific surface area and the surface hardness of amorphous silica, and found that as the specific surface area increases, the Mohs hardness increases, and as the specific surface area decreases, the Mohs hardness decreases. Moreover, amorphous silica having a large specific surface area includes particles having the shape of broken glass pieces and the shape of pointed blades. This is because for amorphous silicas with a large specific surface area, the particle size (herein referred to as the minimum unit particle size) becomes very fine when the soluble silicic acid component is liberated in the silicic form, and the minimum unit particles are aggregated together to form gel-like particles. Because it forms.

However, according to the AB properties and transparency of the film, it is necessary to use amorphous silica having a relatively specific surface area for the resin film, which causes a disadvantage that the device is damaged by friction during the production of the resin film, and the film products are mutually When rubbed, the film surface was scratched, lowering the commercial value of the product. Therefore, satisfactory amorphous silica that can be used as an anti-sticking agent for resin films has not been obtained until now.

It is still another object of the present invention to provide a filler for thermosensitive recording paper which does not exhibit ground fogging, exhibits excellent antifouling adhesion, and is capable of forming a high concentration of images.

Still another object of the present invention is to provide a filler for thermosensitive recording paper which can form a high concentration dispersion during coating operation, which facilitates the coating operation and reduces the manufacturing cost.

That is, the fine particulate amorphous silica shown in Japanese Patent Publication No. 1030/1990 is an excellent solution to the problems associated with thermally sensitive recording paper, but the particle size is fine, which greatly increases the viscosity of its coating solution. Therefore, when the amorphous silica is used as a coating filler, the coating operation should be performed by selecting a condition that uses a low concentration of the filler in the coating solution than when using calcium carbonate or baked kaolin. Moreover, it takes a long time to dry, and there is a problem in terms of coating operation and recording paper production cost.

According to the present invention, the average particle diameter (D1) of the first particles observed by the scanning electron microscope is 100 to 270 nm, and the apparent specific gravity (JIS K 6220.6.8 method) is 0.24 to 0.55 g / cm ³ _{, which is obtained by the} BET method. Specific surface area by 200 to 500 m ² _/ g, the minimum diameter of silica particles (* DO) is 5 to 15nm calculated from the BET method specific surface area, (average diameter (D1) of the first particles): (minimum silica unit Amorphous silica type fillers having an agglomeration degree (DA) of 10 to 50, defined by the ratio of particle diameter (DO)), as well as fillers for thermosensitive recording paper are provided.

In addition, the present invention provides a thermoplastic resin film prepared by mixing 0.01 to 5 parts by weight of the amorphous silica as an anti-sticking agent per 100 parts by weight of the thermoplastic resin.

According to the present invention, there is provided a thermosensitive recording paper obtained by adding an amount of the above amorphous silica as a filler into a thermosensitive recording layer composition of a thermosensitive recording paper known per se as a filler.

Figure 1 is a scanning electron micrograph (20,000 times magnification) showing the particle structure of the amorphous silica-type filler (amorphous silica-type filler) of the present invention.

Figure 2 is a scanning electron micrograph (20,000 times magnification) showing the particle structure of a conventional amorphous silica filler (Comparative Example 2).

3 is a scanning electron micrograph (20,000 times magnification) showing the particle structure of a conventional amorphous silica filler (Comparative Example 3).

Figure 4 is a diagram showing the relationship between the dispersion and viscosity of the filler in water, curve A is using the amorphous silica of the present invention (Example 1), curve B is baked kaolin (baked kaolin) As used, curve C uses conventional amorphous silica (Comparative Example 2), and curve D uses light calcium carbonate.

Hereinafter will be described with respect to amorphous silica having a variety of particle size, the measurement method and the term definition is as described below.

When the BET method specific surface area (m ² / g) is represented by SA and the minimum elementary particle size (nm) is represented by DO, the silica minimum unit particle diameter (DO) is calculated from the equation SA = 2727 ÷ DO. . The specific surface area of amorphous silica particles depends on the diameter of the smallest basic particle, ie the diameter of the smallest particle when the amorphous silica particles are precipitated with free silicic acid. The minimum unit particles of the amorphous silica are mainly spherical, and do not exist alone, and their presence cannot be confirmed by a conventional electron microscope.

Average diameter (D1) of 1st particle | grains: The diameter of individual particle | grains was measured from the scanning electron micrograph of amorphous silica, and their number average value was found. It consists of the smallest unit particles agglomerated or coagulated and refers to the smallest particle diameter of amorphous silica that can be detected through an electron microscope.

Diameter D2 of the second particle: The median diameter, based on the volume of amorphous silica measured by the couter counter method. It refers to the diameter of the amorphous silica particles composed of the coagulum of the first particles, which can exhibit an aspect as powder particles.

The amorphous silica of the present invention has an average size (D1) of the first particles of 100 to 270 nm, a BET method specific surface area of 200 to 500 m ² / g, and a cohesion degree (DA) of 10 to 1 defined as D1 / DO. The outstanding feature is that it is 50.

1 is a scanning electron micrograph showing the particle structure of the amorphous silica used in the present invention, from which the average diameter of the first particles of the amorphous silica used in the present invention is 100 to 270nm, the amorphous silica is It can be seen that it has a distinct particle shape (appearance) and a uniform particle structure. It can also be seen that the first particles are symmetrically distributed.

The amorphous silica of the present invention is a discontinuous particle (see FIG. 2), in which the silica minimum unit particles are finer than those of the present invention and have an obscure agglomeration, which is not observed as a so-called uniform particle by a conventional electron microscope, or It has a particle structure fundamentally different from conventional amorphous silica, which is observed continuously as a homogeneous gel form (see FIG. 3).

In the present invention, the BET method specific surface area is defined in the range of 200 to 500 m ² / g. Because if the specific surface area is 200 m ² / g or less, the adhesion resistance is lost and film defects such as silver and voids are caused, and if the specific surface area is more than 500 m ² / g, the cloudy phenomenon of the film is intensified and the gloss is Reduced and lost transparency and a large amount of scratching of the film by friction, even if the powder is post-treated, it becomes difficult to fit the average diameter of the first particles into the area of the invention.

Amorphous silicas having a BET method specific surface area of 200 to 500 m ² / g are known. However, the main feature of the present invention is that the cohesion degree DA of the silica minimum unit particles is 10 to 50, and the average diameter D1 of the first particles is 100 to 270 nm.

The film in which the cohesion degree DA and the average diameter D1 of the first particles according to the present invention are maintained in the above range shows not only excellent anti-sticking property but also excellent resistance to scratches caused by friction when the films are rubbed with each other. The above fact will be easily understood by the examples and comparative examples which will be described later.

By fixing the cohesiveness DA and the average diameter D1 of the first particles within the above range, it is possible to additionally form a vivid thermally sensitive image which is maintained at a high level on the thermally sensitive recording paper without ground blur, and the coating step is performed. During the process, the resistance to friction of the device can be greatly improved. This fact can be easily confirmed from FIG. 1 showing the particle structure of the amorphous silica of the present invention and from FIG. 3 showing the particle structure of the conventional amorphous silica with glassy particles.

Due to this novel particle structure, the amorphous silica used in the present invention does not form a glassy gel: large silica particles having a diameter of the first particles are caused by very fine silica particles acting as nuclei and acting as binders. Agglomerates, thereby exhibiting a relatively large apparent specific gravity and BET method specific surface area and a small oil-sucking amount of 50 to 120 ml / 100 g.

Therefore, the amorphous silica of the present invention has a particle structure composed of large first particles despite its large BET method specific surface area. Thus, for example, when dispersed in water, the dispersion shows very low viscosity.

Referring to FIG. 4 showing the relationship between the filler concentration in water and the viscosity, a typical amorphous silica filler (specific surface area 60 m ² _/ g, apparent specific gravity 0.18 g / m ³ ) is about 30% by weight. Viscosity increases rapidly in the vicinity of the dispersion concentration in water, showing increased viscosity. On the other hand, the fillers of the present invention slowly increase in viscosity with respect to the concentration of dispersion in water. Therefore, the filler of the present invention can be provided in the form of a low viscosity but high concentration dispersion solution and improves the efficiency in coating operation and reduces the energy cost required to evaporate water.

As described above, the amorphous silica of the present invention has a small diameter of the second particles of 1 to 5 탆, preferably 1 to 2.5 탆, and is very thick and exhibits excellent dispersing properties. Therefore, the amorphous silica of the present invention can be used as a coloring recording layer of undercoating or thermosensitive paper to obtain a coated surface having excellent smoothness.

Furthermore, the first particles are hardly aggregated, and the diameter of the second particles measured by the counter counter method is 1 to 5 탆, and the dispersibility of the amorphous silica into the resin is excellent. Moreover, silver spots or voids do not appear in the formed film, and the appearance of the film is excellent.

Moreover, when the amorphous silica of the present invention was used for thermally sensitive recording papers, even if the oil suction amount was as small as 50 to 120 ml / 100 g, it showed satisfactory effects on preventing scum adhesion and adhesion, and also on thermal heads. The consistency is also maintained. To date, amorphous silica has had a high oil suction amount (100 ml / 100 g or more), but at present, since the heat sensitive recording paper has a three-layer structure including an undercoating layer, a very high oil suction amount is not necessary. That is, when using a pigment having an oil absorption as large as 200 ml / 100g in the undercoat layer, the binder required for the colored layer is absorbed in a large amount when applying the thermosensitive coating solution. The amorphous silica of the present invention moderately absorbs oil, does not over absorb the binder, and helps to increase the surface strength of thermosensitive recording paper. Furthermore, the use of the amorphous silica of the present invention in the undercoat layer or the colored layer of the thermosensitive paper of the two-layer structure and the thermosensitive paper of the three-layer structure exhibits anti-sticking or anti-sticking effect.

In addition, the amorphous silica of the present invention has a very small pore diameter even though the specific surface area measured by the BET method is about 200 to 500 m ² / g, thereby making it possible to obtain thermally sensitive recording paper without cloudiness of the ground. For example, white carbon or gel type silica with a large specific surface area exhibits surface cloudiness at the time of or after the preparation of a thermosensitive coating solution, since the leuco dye molecule is solid. This is because they penetrate into relatively large pores acting as an acid-type developer. On the other hand, the amorphous silica of the present invention has a peculiar particle structure and a small amount of oil suction despite the relatively large specific surface area of the BET method. Therefore, it is thought that the amorphous silica of the present invention does not absorb leuco dye molecules because the diameter of the pores is very small.

In addition, the relationship between the surface hardness and the specific surface area of amorphous silica is experimentally known, and the amorphous hardness of amorphous silica having a large specific surface area is 2 or more. According to the above relationship, it is considered that the amorphous silica of the present invention has a large specific surface area, is rich, has a high hardness, and rubs the heat head. However, as can be clearly seen in FIG. 1, the amorphous silica of the present invention is present in a very round and cornerless agglomerate group in appearance and does not rub the heat head. Moreover, the amorphous silica of the present invention is high in purity and does not corrode the heat head.

Regarding the above-described first particle structure, the amorphous silica of the present invention has the additional feature that the surface area of the BET method is relatively large, but the oil suction amount is as small as 50 to 120 ml / 100 g. When the filler or pigment is mixed into the resin, the specific surface area is usually reduced to make the surface wet well, and the apparent specific gravity is increased to make the filling volume smaller and easier to mix. The amorphous silica of the present invention has a high apparent specific gravity, a small oil suction amount, can be used in high concentration as a thermally sensitive recording layer composition, and enables the production of a coating solution that can be advantageously used even when the amount of the binder is small. It can be mixed into and evenly dispersed.

An important feature of the amorphous silica of the present invention is that the apparent specific gravity (JIS K 6220. 8. 8 method) is in the range of 0.24 to 0.55 g / cm ³ . The diameter of the first particles of amorphous silica having a large apparent specific gravity is uneven (amorphous silica made by precipitation). On the other hand, the apparent specific gravity of the amorphous silica having a small diameter of the first particles is 0.2 g / cm ³ or less. However, the amorphous silica of the present invention is denser than conventional amorphous silica made by precipitation and has an apparent specific gravity equivalent to amorphous silica made by gel process. The amorphous silica of the present invention is compact and not likely to be a powder, exhibits excellent handleability, easy mixing into a resin, and excellent processability. Moreover, the powder particles are dense and do not easily scatter in the air and do not deteriorate the working environment.

The present invention will be described in detail based on the following preferred examples.

Amorphous silica

The amorphous silica of the present invention has an average diameter of the first particles (measured by a scanning electron microscope) of 100 to 270 nm, and an average diameter of the second particles (measured by a counter counter method) of 1 to 5 탆, preferably 1.5. To 4.5 μm, most preferably 1.8 to 3 μm, with an apparent specific gravity (JIS K 6220. 6. 8. method) of 0.24 to 0.55 g / cm ³ , preferably 0.27 to 0.5 g / cm ³ , most preferably 0.3 to 0.45 g / cm ³ , oil suction amount (JIS K 5105 method) is 50 to 120 ml / 100g, preferably less than 100ml / 100g, most preferably less than 80ml / 100g, by BET method The specific surface area SA is 200 to 500 m ² / g, and the cohesion degree DA defined by the ratio of (average diameter D1 of the first particles) ÷ (silica minimum unit particle diameter (DO)) is 10 to 50, Preferably it is 15-45, Most preferably, it is 20-40.

Manufacturing method

Although not limited to the method described below, the amorphous silica of the present invention is prepared by a method that falls between a conventional gelling method and a precipitation method, and more specifically, an aqueous solution of an acidic sol and salt in the presence of sodium silicate under specific conditions. It is prepared by reacting. In preparing the amorphous silica of the present invention, it is first necessary to prepare an acidic silica sol having a pH of 0.2 to 2.5 of the adjusted amount of silica used in the reaction and a concentration of 3 to 20% by weight of silica calculated as SiO ₂ . There is.

The acidic silica sol is obtained by adding 20 to 70% by weight of an aqueous sodium silicate solution of 10% by weight of the total weight of sodium silicate to 10 to 60% by weight of an aqueous hydrochloric acid or sulfuric acid solution while stirring, so that the pH after the reaction is within the above-mentioned range. Then, the acidic silica sol was dissolved in a salt solution such that the content of silica calculated as SiO ₂ was 10 to 100% by weight, and the resultant was added to the aqueous sodium silicate solution with stirring at a temperature of 5 to 90 ° C. to obtain a silica hydrogel of the present invention. .

Here, it is important to sufficiently stir the solution so that the pH after the reaction is 5 to 8, preferably 6 to 7.

Moreover, the method of preparing the silica hydrogel of the present invention is not limited to the above-described method, but after adding the salt to 10 to 300% by weight of the SiO ₂ content by the method of preparing the acidic silica sol, the pH after the reaction is The remaining sodium silicate aqueous solution may be added so that it becomes 5-8.

Thereafter, the silica hydrogel was filtered, washed with water using a conventional method, dried at a temperature of 120 ° to 400 °, and classified as necessary to obtain the product of the present invention.

The SiO ₂ content of the amorphous silica obtained according to the invention is 90 to 96% by weight, preferably 91 to 95% by weight (when dried at a temperature of 150 ° C.).

The amorphous silica filler used in the present invention is prepared by the method described above. When the acid silica sol is neutralized or salted to obtain amorphous silica, this is called sedimentation-method silica, and when sodium silicate is neutralized to obtain amorphous silica, it is referred to as gel-method silica. Name it. It can be said that the amorphous silica of the present invention consists of both the precipitated silica and the gel silica. Typically, precipitated silica and gel silica are mixed with each other in the form of elemental particles. However, for those skilled in the art, a hybrid particle structure in which amorphous silica is in the form of nuclear particles in which one or both of the precipitated and gel silicas are in the form of nuclear particles, which are covered with a coating (coating) of precipitated silica or gel silica. It is obvious that it may have.

When the amorphous silica of the present invention is used as an anti-sticking agent for resins, lubricants, antistatic agents, plasticizers, nucleating agents, antifogants, ultraviolet absorbers, antioxidants, insecticides, fungicides, paints, coloring agents, pharmaceuticals and the like simultaneously with resin molding The organic components of can be introduced or mixed. Furthermore, the amorphous silica can be used in admixture with other inorganic fillers. In addition to the aforementioned organic components, fillers may also be surface treated prior to various metal salt soaps, waxes, resins, surfactants, lubricants, various binders or inorganic oxides.

The content of the organic and inorganic components used for inflow or mixing or surface treatment should be 0.1 to 30% by weight, preferably 1 to 10% by weight relative to amorphous silica.

Application example

The amorphous silica of the present invention can be applied to the following resin molded articles to provide transparency, slippage and anti-sticking properties: Various stretches, for example, propylene homopolymer or ethylene-propylene copolymer, which is a crystalline propylene copolymer Various thermoplastic resins such as these; High density, medium density and low density or linear low density polyethylene; Olefin resins such as ion crosslinked olefin copolymers, ethylene-vinyl acetate copolymers, and ethylene-acrylic acid ester copolymers; Thermoplastic polyesters such as polyethylene terephthalate and polybutylene terephthalate; Polyamide resins such as 6-nylon, 6,6-nylon and 6,8-nylon; Chlorine-containing resins such as vinyl chloride and vinylidene chloride; Polycarbonate; And sulfones.

When the amorphous silica of the present invention is used in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the thermoplastic resin, preferably 0.1 to 5 parts by weight per 100 parts by weight of the thermoplastic resin, the above object can be achieved.

Moreover, using the above-mentioned properties, the amorphous silica of the present invention is known per se as a filler for thermosensitive recording paper in an amount of 5 to 60% by weight, preferably 20 to 40% by weight based on the solid component. It can be included in the thermosensitive recording layer composition.

In the above composition, examples of the leuco pigment used as the colorant include triphenylmethane type leuco pigment, fluoran type leuco pigment, spiroran type leuco pigment, rhodamine lactam type leuco pigment, auramin type leuco pigment, and phenolriazin leuco. Pigments and the like, and may be used alone or in combination of two or more of them.

As coloring binders, such as bisphenol A, bisphenol F, or 2,6-dioxybenzoic acid can be used, which are solid at room temperature and melt upon heating.

As auxiliary components, silicates well known as fillers such as calcium carbonate, baked kaolin, aluminum hydroxide and aluminum silicates, calcium silicates and magnesium silicates can additionally be used and mixed into the silica of the present invention.

In addition, the binder may be a water-soluble resin or a resin that can be dispersed in water, for example, starch, cyanomethyl starch, carboxyl starch, carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, water-soluble acrylic resin , Vinylmethyl-ether copolymer, sodium alginate, SBR latex, NBR latex, or ethylene-vinyl acetate copolymer.

In addition, mixing of various waxes such as fatty acids, fatty acid amides, carnauba wax, polyethylene wax, or organic bases such as alkanolamines as a sensitizing agent can prevent coloring.

A dispersion solution in which leuco pigment is dispersed in a binder solution, and a dispersion solution in which phenol is dispersed in a binder solution are prepared, and then coated on paper or synthetic paper to produce a thermosensitive recording layer. The amorphous silica filler of the present invention can be premixed with the phenolic dispersion solution, and additionally prepared a dispersion solution in which the amorphous silica filler is dispersed in the binder solution and mixed with the two dispersion solutions for thermosensitive recording. You can even create a layer.

Moreover, the amorphous silica of the present invention can be mixed with the thermosensitive recording layer or can be used as an undercoat layer used for the thermosensitive recording layer. As apparent from the scanning electron micrograph of Fig. 1, the filler for thermosensitive recording paper of the present invention has an appearance close to a spherical shape with a uniform particle diameter. Therefore, when the filler is used as the undercoat layer, the surface becomes uniform, thereby improving the smoothness of the upper recording layer.

In addition, the amorphous silica of the present invention can be mixed with various paints, adhesives, and coating resin compositions to be used in various fields, and can be mixed with fillers in pharmaceuticals, foodstuffs, agrochemicals and pesticides.

Moreover, when the amorphous silica filler of the present invention is used in combination with calcium carbide, it can be used as a polishing agent for tracing paper, a substrate power stabilizer, a substrate power improver for synthetic paper, a color enhancer for diazo photo paper, and an adhesive for ink. Can be applied as a coated top layer.

Example

The present invention will be described in detail by the following examples. Here, the properties of the amorphous silica of the present invention were tested, and the anti-sticking agent and filler for thermosensitive recording paper were tested and evaluated in the manner described below.

(1) Specific surface area by BET-method

Nitrogen gas-adsorption amount (cc / g) adsorbed on the surface of the sample as a single molecule layer was measured using an automatic BET specific surface area measuring apparatus (manufactured by Carlo-Ebra Co., Sortomatic Series 1800) and the BET specific surface area was It was calculated from surface area (SA) = 4.35 x Vm (m ² / g).

(2) Average second particle diameter (medium diameter)

The particle diameter is measured from 50% of the volume distribution on the particle size cumulative curve obtained by the Couter Counter method (Couter Electronics Co., USA, Model TA-II).

(3) first particle diameter

The particle diameter (nm) in the limited field of view image is determined by calculating the average first particle diameter using a scanning electron microscope WET-SEM (WS-250) (manufactured by Akashi Beam Technology Co., Japan).

(4) elemental particle diameter

It is evident by RK Iler * that the following relationship exists between the BET specific surface area SA (m ² / g) and the elemental particle diameter DO (nm) and calculates DO (nm) from the SA = 2727 / DO relationship.

* Ralph K. Iler, Colloidal Chemistry of Silica and Silicates, Cornell University Press, 1955.

(5) cohesion (DA)

The degree of aggregation DA of the silica element particles constituting the first particles is defined by the following general formula.

DA = (average first particle diameter (DI)) ÷ (silica element particle diameter (DO))

(6) oil-suction

The oil suction amount is measured in accordance with JIS K 5101-19, which is used specifically for the pigment test method.

(7) pH value

The pH value is measured in accordance with JIS K 5101-24A, which is used specifically for the pigment test method.

(8) apparent specific gravity

The apparent specific gravity (g / cm ³ ) is measured in accordance with JIS K 6220.6.8, which is used specifically for the formulation test of rubber.

(9) Preparation of Film

Unstretched Polypropylene Film (C-PP Film)

C-PP films have two types of polymers: homopolymers of propylene such as crystalline propylene polymers (melt flow rate (MFR) = 1.8 g / 10 min, isotactic index II = 96.0) and ethylene-propylene random air Coalescing (melt flow rate MFR = 6.5 g / 10 min, isotactic index II = 97.0, ethylene content = 4.0 mol wt%, DSC melting point = 140 ° (according to ASTM D-3417)) is obtained under the following conditions: .

The amorphous silica powder is added as an anti-sticking agent (hereinafter referred to as AB agent) in an amount of 0.15 parts per 100 parts of the propylene polymer. At the same time 0.15 parts of 2,6-di-t-butyl paracresol and 0.1 part of calcium stearate are added as antioxidants and the mixture is remixed for 3 minutes at 1000 rpm with a Henschel mixer. The mixture is then dissolved and pelletized with a single screw extractor having a diameter of 65 mm. The pellet is extracted with an ab ejector with a diameter of 35 mm with T-dies at 230 ° to obtain an undrawn film (film sample F-1) with a thickness of 25 μm.

Polypropylene film stretched by double axis (O-PP film)

The amorphous silica powder is added in an amount of 0.15 parts per 100 parts of the propylene homopolymer (melt flow rate MFR = 1.8 g / 10 min, isotactic index I.I. = 96.0), which is a crystalline propylene polymer as AB agent. At the same time, 0.1 part of 2,6-di-t-butyl paracresol and calcium stearate are added as antioxidants and the mixture is mixed for 3 minutes at 1000 rpm with a Henschel mixer. The mixture is then dissolved and pelletized with a single screw extractor having a diameter of 65 mm. The pellets are extracted with a 35 mm diameter extractor with T-dies at 230 ° C. to obtain a film similar to a sheet 1250 μm thick. The film was stretched five times in a vertical direction at 115 ° C. using a double-axis stretching machine having a diameter of 115 mm, and then stretched ten times in a transverse direction in a tenter oven at 170 ° C. to obtain a thickness of 25 μm. A biaxially pulled film is obtained (film sample F-2).

Nylon film (O-NY film)

Using amorphous silica powder as an AB agent, an amount of 5 parts per 94 parts of 6-nylon powder is added (particle diameter of 300 mesh or smapper, specific gravity = 1.14, melting point = 220 ° C). At the same time 1 part of ethylene bis-stearylamide is added as a dispersant and the complex is mixed for 3 minutes at 1000 rpm with a Henschel mixer. The mixture was dissolved at 260 ° C. using a 65 mm diameter single screw extractor to obtain a master pellet containing 5 parts of AB. 2 parts of master pellets and 98 parts of 6-nylon pellets containing no AB agent are mixed together to obtain pellets containing 0.1 part of AB agent. The mixed pellet is then dissolved, extracted with a 35 mm diameter extractor with a T-dice and solidified on a cooling roll at 40 ° C. to obtain an undrawn film with a thickness of 140 μm. The film was pulled three times in both axial directions simultaneously in the vertical and transverse directions at a stretching temperature of 120 ° C. using a 115 mm diameter dual axis drawing molder, and then stretched in both axes having a thickness of 15 μm by heat fixing at 190 ° C. Obtained (Film Sample F-3).

(10) Aspect of the film

Fisheyes or voids appearing on the surface of a 20 cm X 20 cm size film are visually observed and evaluated based on the following criteria.

◎: No silver spot or void is observed

○: Silver spots or voids were observed on an area of about 10% or less of the entire film.

(Triangle | delta): A silver point or a void is disperse | distributed on about 50% of the whole film.

X: The silver point or the void has a large amount of about 50% or more of the entire film.

(11) scratch resistance on film surface

After the production according to the manufacturing method wound film (200 m / roll) about 20 m / min. It solves 3 times at the speed of and evaluates based on the following criteria.

(Circle): Very little or no scratch degree.

(Triangle | delta): A scratch is recognized clearly, but is not disperse | distributed to the whole surface.

X: There are many scratches which cannot use a film practically.

(12) Haze (%) of film

Turbidity is measured according to the method of ASTM-D 1003-61 using a direct read turbidity meter (manufactured by Suga Testing machine Co., Japan, directly read-type haze meter).

(13) static friction coefficient

The static coefficient of friction (μs) and the coefficient of dynamic friction (μd) are measured using a slop measuring instrument (manufactured by Nippon Rigaku Kogyo Co., Japan) in accordance with ASTM-D 1894 under the following conditions.

Film Sample F-1: 23 ° C, 40 ° C × 3 Days

Film Sample F-2: 40 ° C, × 1 Day

Film Sample F-3: RH (relative humidity) 65%, RH 85%

(14) Anti-sticking (AB Castle: g / cm)

The two pieces of film are overlapped with each other to have a contact area of 10 cm ² , sandwiched between two glass plates, and left at 40 ° C. for 24 hours under a load of 50 g / cm ² . After standing, the upper and lower films are separated from each other to obtain the highest load. Measure using a friction coefficient measuring device manufactured by (Japan).

Film Sample F-1: 50 ° C × 7 Days

Film Sample F-2: 50 ° C x 30 Days

(15) Evaluation of thermosensitive paper

(Recording paper production)

One part of amorphous silica having the properties shown in Table 1 was dispersed for 5 minutes at 2000 rpm using a disperser in 4 parts of water as a filler. To the mixture, 3 parts of Solution A, 6 parts of Solution B, 6 parts of Solution C, and 3 parts of Solution D described below are added, followed by sufficient mixing to prepare a coating solution for thermosensitive recording paper. In the following solutions A, B, C and D, using a magnetic ball as the grinding media, grinding with Paint Conditioner Model 5410 (Red Devil Inc.), the average particle size of the fine particles in the solution 3 μm ( It is smaller than the Couter Counter method.

Solution A: 1 part of 3-dibutylamino-6-7-anilinofluorane

5% polyvinyl alcohol5 parts

Solution B: Bisphenol A 1 part

5% polyvinyl alcohol5 parts

Solution C: 1 part stearic acid amide

5% polyvinyl alcohol5 parts

Solution D: 1 part zinc stearate

5% polyvinyl alcohol5 parts

45 g / cm ² of paper (paper for PPC) is coated with a coating rod with a coating solution for heat sensitive recording paper prepared under the above mentioned conditions with a coating amount of about 6 g / m ² (based on dry weight).

The thermally sensitive recording paper obtained as above is evaluated for ground fouling, dynamic coloring properties, and anti-sticking effect.

In order to separately verify the characteristics of the filler, the dispersion system of amorphous silica in water is further evaluated by its viscosity characteristics.

(Evaluation of thermal sensitivity sheet)

(1) Ground fouling

The obtained thermal recording paper was left indoors for 72 hours, and the concentration of ground contaminants naturally occurring on the coated surface was measured using Fuji standard Densitometer Fugi Photofilm Co. (manufactured by Fuji standard Densitometer Fugi Photofilm Co., Japan). do. At the same time, the soil contamination level is evaluated according to the following criteria.

(Circle): Ground pollution concentration is less than 0.13, and it is hardly recognized.

(Triangle | delta): Ground contamination concentration is larger than 0.13 or less than 0.20, and contamination is recognized slightly.

X: The soil contamination concentration was greater than 0.20, and the soil was so noticeable that the recording paper could not be used.

(2) Dynamic coloring property

Using the thermosensitive printing apparatus TH-PMD (manufactured by Okura Denki Co., Japan), the obtained thermosensitive recording paper was subjected to a printing voltage of 24 V, a pulse period of 2 mses, a printing pulse width of 0.5 to 1.5 mesc, and a heat of 2.651 Ω. Recorded under the condition of head resistance, the color sensitivity is evaluated according to the following criteria and the completed concentration (pulse width, 1.5 msec) is measured using Fuji Standard Danishitomi FDS-103.

(Circle): The dynamic coloring sensitivity curve of the coloring density with a pulse width (0.5-1.5 msec) rises rapidly, and the completed density is 1.37 or more.

(Triangle | delta): The dynamic pigmentation sensitivity curve of the pigment | dye concentration with a pulse width (0.5-1.5 msec) raises comparatively sharply, and the completed density is larger than 1.3, but smaller than 1.37 and comparatively low.

X: The dynamic coloring sensitivity curve of the coloring concentration with a pulse width (0.5-1.5 msec) rises slowly, and the completed concentration is below 1.30.

(3) Preventing adhesion of tailings

The thermally sensitive recording paper thus obtained was printed in dark black using NTT FAX-510T, and the tailings attached to the thermal head after printing were visually observed. In addition, 1 cm × 1 cm solid black squares are arranged up and down and left and right while maintaining a gap of 3 mm to prepare test pattern paper and print them on the thermal recording paper to print white paper (non-printing) along the direction in which the recording paper moves. Observe the small black spots (dispersion of tailings) on the tailings that appear on the surface. The adhesion prevention effect of tailings is evaluated according to the following evaluation criteria.

(Circle): Adherence of tailings is not recognized at all on a heat head, and dispersion of tailings is not recognized even on the printed surface.

(Triangle | delta): The adhesion of tailings on a thermal head is recognized slightly, and the dispersion of tailings is recognized a little on the printed surface.

X: The adhesion of the tailings on the heat head is clearly recognized, and the dispersion of the tailings is also clearly recognized on the surface.

In order to verify the characteristics of amorphous silica as a filler, the viscosity of the aqueous dispersion was measured under the following conditions and the results are shown in FIG. 4.

Using a high speed disperser, the amorphous silica is dispersed in the tap water in a 1 liter beaker at 2,000 rpm for 5 minutes at room temperature so that the amorphous silica concentration is 20%, 30% and 50% by weight. The viscosity of the dispersed slurry is measured at 20 ° C. using a type B viscometer (manufactured by Tokyo Keiki Seizosho Co.).

Example 1

Sodium silicate solution (specific gravity 1.29, the composition _{3.3SiO 2 · Na 2 O · nH} 2 O) , and 13%, according to using a sulfuric acid solution having a concentration of preparing a non-crystalline silica, 1 of the sodium silicate solution according to the method mentioned for the first time Acid silica sol was prepared using the / 2 amount.

50% of the total reaction amount of sodium silicate solution was flowed into the sulfuric acid solution with stirring for 2 hours while maintaining the temperature lower than 20 ° C to obtain an acid silica sol having pH 7.0. Then, NaCl was added to the remaining 50% sodium silicate solution so that the weight ratio of SiO ₂ : NaCl was 1: 1, and the acid silica sol solution obtained above was added with stirring for 5 hours or more. The silica slurry obtained at pH 6.5 was filtered and washed, and the silica cake obtained was dried at 110 ° to 350 ° C., pulverized and classified to give 1.8 μm, 2.7 μm, and 3.5 μm (Samples 1, 2 and 3). Amorphous silica having an average second particle diameter was obtained. The obtained amorphous silica particles exhibited the characteristics as shown in Table 1, and the resin film sample F-1 using amorphous silica particles as the AB agent was evaluated as shown in Tables 2 and 3, and the sample F- 2 was evaluated as shown in Table 4 and Sample F-3 was evaluated as shown in Table 5. The amorphous silica obtained was 93.5 wt%, calculated as SiO ₂ under conditions dried at 150 ° C.

Example 2

Acid silica sol was prepared in the same manner as in Example 1 using hydrochloric acid as the inorganic acid, and amorphous silica was obtained by the method described below using the sol.

A sodium silicate solution corresponding to 33% of the total reaction amount was flowed into a hydrochloric acid solution (concentration 14%, specific gravity 1.07) while stirring at a temperature of 20 ° C. or lower to obtain an acid silica sol having a pH of 0.3. NaCl was then added to the remaining 67% sodium silicate solution so that the weight ratio of SiO ₂ : NaCl was 1: 0.1 and the mixture was heated to 60 ° C. The obtained acid silica sol solution was flowed while stirring the mixture for 4 hours or more. From the silica slurry obtained at pH 7.2, amorphous silica having an average second particle diameter of 2.18 μm was obtained in the same manner as in Example 1 (Sample 4). The amorphous silica obtained as described above exhibited the characteristics shown in Table 1, and the resin film sample F-1 using the amorphous silica as the AB agent was evaluated as shown in Tables 2 and 3, and the sample F -2 was evaluated as shown in Table 4, and sample F-3 was evaluated as shown in Table 5.

The amorphous silica obtained was 91.4 wt%, calculated as SiO ₂ under conditions dried at 150 ° C.

Example 3

An acid silica sol was prepared in the same manner as in Example 1 using hydrochloric acid as the inorganic acid and amorphous silica was obtained by the method described below using the sol. Sodium silicate solution corresponding to 67% of the total reaction amount was flowed into the hydrochloric acid solution (concentration 14%, specific gravity 1.07) while stirring at a temperature lower than 20 ° C. for at least 2.5 hours to obtain an acid silica sol having a pH of 1.4. Then the remaining sodium silicate

NaCl was added to 33% of the solution so that the weight ratio of SiO ₂ : NaCl was 1: 2.5, and the acid silica sol solution obtained above was added while stirring the mixed solution for at least 5 hours. From the silica slurry obtained at pH 7.1, amorphous silica having an average second particle diameter of 2.8 μm was obtained in the same manner as in Example 1 (Sample 5) (Sample 5). The amorphous silica obtained as described above exhibited the properties as shown in Table 1, and the resin film sample F-1 using the amorphous silica as the AB agent was evaluated as shown in Tables 2 and 3, and the sample F- 2 was evaluated as shown in Table 4 and Sample F-3 was evaluated as shown in Table 5.

The amorphous silica obtained was 94.6 wt%, calculated as SiO ₂ under conditions of heating at 150 ° C.

Example 4

In preparing amorphous silica, a concentrated acid silica sol solution was obtained continuously according to the method described below, and then the NaCl-containing sodium silicate solution and the acid silica sol solution were continuously contacted and reacted under heating conditions to form amorphous silica. Obtained. An acid silica sol was prepared according to the method described below using the same sodium silicate solution and sulfuric acid solution (concentration 40%, specific gravity 1.25) as in Example 1. Sodium silicate solution and sulfuric acid solution in an amount equivalent to 50% of the total reaction amount were continuously supplied at a temperature lower than 25 ° C by using a device capable of accommodating a volume ratio of 4: 1, and rapidly shear-stirred to give acid silica sol (pH 2.1) was obtained continuously. NaCl was added to the remaining 50% sodium silicate solution so that the weight ratio of SiO ₂ : NaCl was 1: 2.

Sodium silicate solution and acid silica sol solution obtained according to the above method were continuously fed and reacted together at 60 ° C. with rapid shear-stirring to obtain amorphous silica, amorphous silica having an average second particle diameter of 2.2 μm. (Sample 6) and amorphous silica (Sample 7) having an average second particle diameter of 4.1 μm was obtained in the same manner as in Example 1. Amorphous silica obtained as above

The particles exhibited the characteristics shown in Table 1. The amorphous silica particles obtained as described above showed the characteristics shown in Table 1, and the resin film sample F-1 using amorphous silica particles as the AB agent showed the properties evaluated in Tables 2 and 3, and the sample F- 4 shows Table 4 and Sample F-3 shows the properties as evaluated in Table 5.

The amorphous silica obtained was 92.8 wt%, calculated as SiO ₂ under 150 ° C. heating conditions.

Comparative Example 1

The film was tested and evaluated in the same manner as in Example 1 using amorphous silica sample H1, commercially available product A (Mizusawa Kagaku Kogyo Co., Japan, Japan) having an average second particle diameter of 1.7 μm.

Comparative Example 2

The film was tested and evaluated in the same manner as in Example 1 using amorphous silica sample H2 which is commercially available B (Fuji Debison Co., produced, Japan) having an average second particle diameter of 2.1 μm.

Comparative Example 3

The film was tested and evaluated in the same manner as in Example, using amorphous silica sample H3, commercially available B (produced by Fuji Debison Co.), with an average second particle diameter of 3.1 μm.

As in the above examples, amorphous silica particles obtained in Comparative Examples 1,2 and 3 exhibited the characteristics shown in Table 1, and the resin film F-1 using amorphous silica particles as the AB agent is shown in Table 2 In Table 3, Sample F-2 was evaluated as shown in Table 4 and Sample F-3 as shown in Table 5.

Examples 5 and 6

Using the amorphous silica particles of Samples 1 and 6 obtained in Examples 1 and 4 as fillers for thermosensitive recording paper, thermosensitive recording paper was produced according to the above-described recording paper manufacturing method. Ground contamination, dynamic coloring properties, and anti-sticking effect were evaluated. The results are shown in Table 6.

Comparative Example 4-6

Recording paper was prepared in the same manner as in Example 5 using amorphous silica particles of Samples H1-H3 used in Comparative Examples 1-3 as fillers for thermosensitive recording paper. The results are shown in Table 6.

Properties of Amorphous Silica Particles Example Comparative example Sample number One One One 2 3 4 4 One 2 3 One 2 3 4 5 6 7 H1 H2 H3 pH 7.14 7.15 7.14 7.50 7.8 6.7 6.72 6.98 7.98 3.90 Oil-Aspirated Amount (ml / 100g) 86 83 76 92 98 70 63 162 263 106 Specific surface area (m ² / g) 370 376 386 315 280 465 465 55 288 704 An apparent specific gravity (g / cm _³⁾ 0.321 0.342 0.376 0.286 0.272 0.43 0.523 0.188 0.138 0.506 Average second particle diameter (μm) 1.8 2.7 3.5 2.1 2.8 2.2 4.1 1.7 2.1 3.1 Average first particle diameter D1 (nm) 180 180 180 150 200 250 250 80 9.8 * ∞ Elemental particle diameter DO (nm) 7.4 7.3 7.1 8.7 9.7 5.9 5.9 49.6 9.4 3.8 Cohesion (D1 / DO = DA) 24.4 24 25.5 17.3 20.5 42.7 42.7 1.61 1.04 ∞ *: Average particle diameter from which coarse particles were removed as shown in FIG.

Film Sample F1 Evaluation Example Comparative example Sample number One One One 2 3 4 4 One 2 3 One 2 3 4 5 6 7 H1 H2 H3 Turbidity (%) 2.5 2.6 2.8 2.5 2.7 2.5 3.2 2.5 2.7 2.9 Glossiness (%) 97 95 95 96 95 96 93 97 95 93 Slippery * silence/ 0.65 0.68 0.70 0.65 0.70 0.63 0.72 0.60 0.65 0.65 dynamic /0.51 /0.53 /0.55 /0.50 /0.56 /0.50 /0.58 /0.50 /0.50 /0.55 Slip * 2 silence/ 0.31 0.33 0.34 0.29 0.34 0.28 0.36 0.27 0.30 0.33 dynamic /0.27 /0.29 /0.30 /0.26 /0.30 /0.25 /0.32 /0.24 /0.26 /0.29 Adhesion Prevention (g / cm) * 3 Good Good Good Good Good Good Good 0.25 Good Good Scratch resistance ○ ○ △ ○ ○ ○ ○ ○ △ × Appearance of film ◎ ◎ ○ ◎ ◎ ◎ ○ × × ◎ * 1: 23 ° C x 1 day, * 2: 40 ° C x 3 days, * 3: 50 ° C x 7 days

Film Sample F1 Evaluation Example Comparative example Sample number One One One 2 3 4 4 One 2 3 One 2 3 4 5 6 7 H1 H2 H3 Turbidity (%) 2.0 2.6 3.2 2.0 2.8 2.0 3.6 2.1 2.9 2.6 Glossiness (%) 110 100 96 110 100 110 97 120 100 96 Slippery * silence/ 0.30 0.35 0.45 0.32 0.39 0.32 0.48 0.27 0.41 0.37 dynamic /0.26 /0.32 /0.37 /0.27 /0.31 /0.27 /0.37 /0.24 /0.32 /0.32 Slip * 2 silence/ 0.13 0.20 0.27 0.12 0.22 0.15 0.27 0.12 0.12 0.24 dynamic /0.12 /0.18 /0.25 /0.11 /0.20 /0.14 /0.25 /0.11 /0.11 /0.23 Adhesion Prevention (g / cm) * 3 1.25 1.00 0.36 1.26 0.95 1.15 0.32 2.95 1.26 1.29 Scratch resistance ○ ○ △ ○ ○ ○ △ ○ △ × Appearance of film ◎ ◎ ○ ◎ ○ ◎ ○ × × ◎ * 1: 23 ° C x 1 day, * 2: 40 ° C x 3 days, * 3: 50 ° C x 7 days

Film Sample F1 Evaluation Example Comparative example Sample number One One One 2 3 4 4 One 2 3 One 2 3 4 5 6 7 H1 H2 H3 Turbidity (%) 1.0 1.1 1.3 1.0 1.3 1.0 1.4 1.1 1.3 1.4 Glossiness (%) 143 139 135 140 139 140 133 143 135 133 Slippery * silence/ 0.52 0.51 0.48 0.52 0.51 0.45 0.45 0.58 0.51 0.51 dynamic /0.52 /0.50 /0.47 /0.52 /0.50 /0.43 /0.43 /0.55 /0.50 /0.49 Adhesion Proof (g / cm) Good Good Good Good Good Good Good 0.13 0.05 Good Scratch resistance ○ ○ △ ○ ○ ○ △ ○ △ × Appearance of film ◎ ◎ ○ ◎ ○ ◎ ○ ◎ × × * 1: 40 degrees Celsius * 1 day, * 2: 50 degrees Celsius * 30 day

Film Sample F1 Evaluation Example Comparative example Sample number One One One 2 3 4 4 One 2 3 One 2 3 4 5 6 7 H1 H2 H3 Turbidity (%) 1.6 2.1 2.8 1.7 2.2 1.7 2.8 5.0 2.4 2.2 Glossiness (%) 143 139 135 140 139 145 135 152 140 135 Slippery * silence/ 0.36 0.42 0.50 0.35 0.51 0.36 0.53 0.51 0.39 0.43 dynamic /0.35 /0.40 /0.45 /0.35 /0.47 /0.35 /0.44 /0.40 /0.37 /0.40 Slipperiness * 2 silence/ 0.46 0.51 0.57 0.45 0.58 0.50 0.55 0.57 0.60 0.68 dynamic /0.43 /0.47 /0.47 /0.42 /0.50 /0.48 /0.47 /0.47 /0.55 /0.62 Scratch resistance ○ ○ △ ○ ○ ○ △ ○ △ × Appearance of Nfilm ◎ ◎ ○ ◎ ○ ◎ ○ ○ × × * 1: 25 ° C x R.H. 65% * 2: 25 ° C x R.H. 85%

Example Comparative example Sample number 5 6 4 5 6 One 6 H1 H2 H3 Properties of Amorphous Silica Particles pH 7.14 6.70 6.98 7.96 3.90 Dispersibility (μm) below 10 below 10 15-20 12-16 9-12 Average particle diameter (㎛) 1.8 2.2 1.7 2.1 3.1 Average first particle diameter D1 (nm) 180 250 80 9.8 * ∞ Oil-Aspirated Amount (ml / 100g) 86 70 162 263 106 Specific surface area (m ² / g) 370 465 55 288 704 An apparent specific gravity (g / cm _³⁾ 0.321 0.430 0.183 0.139 0.506 Calculated first particle diameter (nm) 7.37 5.86 49.58 9.46 3.8 Cohesive (D1 / DO) 24.4 42.66 1.61 1.03 ∞ Evaluation of thermosensitive recording paper Ground Pollution Degree evaluation ○ ○ ○ × × density 0.12 0.12 0.11 0.32 0.36 Dynamic coloring properties Evaluation of pigmentation sensitivity ○ ○ ○ ○ ○ Completed concentration 1.40 1.38 1.40 1.41 1.41 Preventing adhesion of tailings ○ ○ ○ ○ ○ Viscosity Viscosity (CPS) of 20wt% aqueous dispersion slurry 5 5 10 260 Not distributed Viscosity (CPS) of 30wt% aqueous dispersion slurry 7 6 113 Not distributed Not distributed Viscosity (CPS) of 50wt% aqueous dispersion slurry 35 30 Not distributed Not distributed Not distributed *: Value only for particles with measurable diameter

The amorphous silica filler of the present invention exhibits excellent properties in terms of handleability, processability, dispersibility and abrasion resistance, and is transparent and scratch-resistant without, for example, fisheyes or voids when added as an anti-sticking agent. A resin film can be obtained. Due to the above characteristics, the above-mentioned amorphous recording paper used as a heat-sensitive recording paper filler suppresses cloudiness of the ground and increases the concentration of the phase, and because the filler dispersed in the aqueous solution yields a very low viscosity, It is possible to apply a coating solution, which provides good abrasion resistance to the instrument during the coating step.

Claims (3)

The average particle diameter (D1) of the 1st particle observed with the scanning electron microscope was 100-270 nm, the apparent specific gravity (JIS K 6220 method) is 0.24 to 0.55 g / cm <^3> , and the specific surface area by BET method is 200-500 m. ² / g, silica element particle diameter (DO) calculated from the specific surface area of the BET method is 5 to 15 nm, defined as the ratio of (average first particle diameter (D1)) ÷ (silica element particle diameter (DO)) A thermally sensitive recording paper coated by using an amorphous silica filler having a cohesiveness (DA) of 10 to 50 as an solid component in an amount of 5 to 60% by weight. The method of claim 9, A thermosensitive recording paper, characterized in that the average diameter of the second particles by the counter counting method is 1 to 5 m, and the oil-suction amount (JIS K 5101 method) is 50 to 120 ml / 100 g. The method of claim 9, And a viscosity of the water-soluble dispersion slurry containing 50% by weight of the amorphous silica is 100 cps or less.