JP3122275B2 - Cellulose-based fine powder and production method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cellulose fine powder suitable as a filler for a resin molded product and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, attempts have been made to impart surface characteristics close to those of natural wood to synthetic resin moldings to make the surfaces of various furniture, decorative panels, and daily necessities like natural wood. I have. In order to obtain such a wood-like resin product similar to natural wood, it is necessary to add a required amount of wood flour when molding a synthetic resin molded product in order to obtain a wood-like appearance by coloring in a color tone similar to wood. Pigments corresponding to the desired color tone are added to the forming resin material to obtain a resin molded product having a color tone and texture close to the target natural wood.

[0003] Here, as the wood powder added to the formed resin material, wood powder obtained by directly pulverizing wood into fine powder by a dry pulverizer or a wet pulverizer is generally used. Also, in order to improve the dispersibility at the time of compounding with the resin, and as an improved so that no acid gas is generated in the molding machine at the time of resin molding, a hardening treatment of the surface and the like with phenol or urea resin was performed. Particle board surface polishing powders are known. The main characteristic of the particle board surface polishing powder is that it has a fine particle shape with few cilia on the surface and good lubricity. Further, since it is fine and has good lubricity, it is a wood powder having a good dispersibility and mixing property with respect to a powdery resin raw material.

[0004]

However, wood flour obtained by directly pulverizing wood into fine powder has poor pulverizing efficiency regardless of whether it is obtained by a dry pulverizer or a wet pulverizer. Even after the pulverization for a long time, there was a problem that a large amount of wood powder having a large particle diameter remained in the pulverized powder. In addition, this wood flour does not form a granular shape, and as shown in FIG. 5, most of the wood flour is fibrous. Even if the particle diameter measured on the short diameter side is several microns, the long diameter side is long like a cilia, For this reason, when used in combination with a resin, the wood powder often becomes entangled with each other to form an agglomerated state, which is disadvantageous in that the wood powder is not uniformly dispersed in the resin material. Further, since the particle size of the pulverized wood powder is extremely varied, a molded resin product is liable to cause molding distortion and the like, and has a disadvantage that the mechanical strength is partially different. Therefore, wood obtained by directly pulverizing wood into a fine powder due to such inconveniences has limitations in blending, color, and quality control in blending it with a resin material.

On the other hand, the surface polishing powder of the particle board does not have uniform wood characteristics due to the difference in the material characteristics of the particle board, and further, the particle size is reduced due to the difference in the cutting means, for example, the mesh of the sandpaper used. Since the diameter is likely to vary, a resin molded product itself containing the same cannot have a uniform woody appearance.

[0006] Further, such surface polishing powder, and also wood powder obtained from the above-mentioned pulverizer, have a high water content due to its own hygroscopicity. When the resulting mixed material is molded by adding to the mixture, poor molding occurs due to the moisture in the wood flour,
There is a disadvantage that the strength of the molded product cannot be sufficiently obtained.

[0007]

Means for Solving the Problems Claim 1 of the present invention
The means for solving the above-mentioned problem is that the cellulose fine powder described above is subjected to a grinding treatment, the inorganic pigment is supported on the surface, and the water content is adjusted to 3.0% by weight or less. In the method for producing cellulosic fine particles according to claim 2, the coarsely pulverized material of the cellulosic material is ground, and the obtained ground particles having been ground together with the inorganic pigment are charged into a ball mill. The object of the present invention is to carry out the supporting treatment so that the finely ground particles having been subjected to the grinding treatment are loaded with the inorganic pigment in a biting state, and that the water content of the obtained inorganic pigment-carrying cellulosic fine particles is dried to 3% by weight or less. And

[0008]

According to the first aspect of the present invention, since the cellulose-based particles carrying the pigment are ground to form granular rather than fibrous particles, the conventional wood can be directly processed. What is pulverized into fine powder is fibrous, so when mixed and dispersed, the fibrous parts become entangled and become dumpling-like or cotton-like. Because of the dispersion, the fine particles themselves carrying the pigment also have extremely good dispersibility in the forming resin. In addition, since the cellulosic fine particles are not fibrous but granular, there is very little expansion and contraction caused by adsorbing or releasing water (including moisture) and solvents as in conventional fibrous wood flour. Become. further,
Since the water content is 3% by weight or less, even if this is directly added to and mixed with the resin and the resulting mixed material is molded, occurrence of molding defects or the like due to moisture in the fine powder particles is prevented.

According to the method for producing cellulosic fine particles according to the second aspect, since the supporting treatment of the inorganic pigment is performed by a ball mill, the drying of the cellulosic fine particles is performed simultaneously with the supporting treatment by the frictional heat generated in the processing. Then, the moisture content of the fine powder obtained thereby is adjusted to 3% by weight or less.

[0010]

Hereinafter, the present invention will be described in detail. The cellulosic fine particles according to claim 1 of the present invention are obtained by subjecting a cellulosic material such as wood, bacas, rice straw or the like to a coarse pulverization process, grinding the obtained cellulosic coarse particles, and further polishing an inorganic pigment. It is obtained by adjusting the water content to not more than 3.0% by weight while being supported on the surface of the crushed cellulosic powder particles. The fine particles are formed, and the pigment is carried on the surface in a biting state.

In order to obtain such fine particles, first, as a coarse pulverizing process, a material previously formed into chips or the like is pulverized by mechanical impact crushing to adjust the particle size to about 100 to 150 μm. Here, a particle size of 10
The reason for adjusting the particle diameter to 0 to 150 μm is that if the particle diameter is less than 100 μm, the grinding treatment described below is not sufficiently performed, and it becomes difficult to obtain independent particles in a non-fibrous form.
If it exceeds 50 μm, it takes a long time for the grinding treatment, and the treatment efficiency is impaired. In addition, for mechanical pulverization, for example, an impeller mill (IMP-250; manufactured by Seisin Corporation) is preferably used.

Next, the coarse particles thus obtained are ground to obtain fine ground particles having a predetermined particle size range, for example, 70 μm or less. Here, the grinding process means a process having both a grinding process and a polishing process. Even if the grinding process and the polishing process are performed simultaneously, the grinding process is performed after the grinding process is performed. It may be a two-step process. In other words, the grinding treatment referred to here is a grinding treatment for converting a coarsely crushed material into a finely crushed material as described later, and the finely crushed powder particles are entangled in a fiber state, and the surface thereof is covered with cilia. This refers to a process in which a polishing process of polishing the surface so as to reduce the amount of cilia on the surface from the shape of the granular material in the state in which the particles are in a state of being performed is combined. Such grinding treatment is preferably performed by, for example, a ball mill shown in FIG. This ball mill is provided with a cooling jacket 2 on the peripheral wall of a mill body 1 which is open to the atmosphere. Cooling water is supplied from a supply pipe 8 into the cooling jacket 2 and discharged from a drain pipe 9 to circulate the cooling water. Then, the temperature in the mill body 1 is set to a preset temperature, for example, 8
The temperature is set to 0 ° C. or lower.

Here, a motor 5 is provided on the top of the mill body 1, and a rotor 4 for stirring the balls 3 in the mill body 1 is provided on the bottom of the motor 5. The rotor 4 is rotated by the drive of the motor 5, and agitates the ball 3 and the material to be ground to bring them into mechanical contact. Further, an outlet 7 which is opened and closed by a valve 6 is provided at a lower portion of the conical shape of the mill body 1.
The material to be ground after the grinding processing can be discharged.

The ball 3 loaded in the mill body 1 of the ball mill is a ceramic ball having an outer diameter of 3 mm to 5 mm,
In particular, it is preferable to use zirconia or alumina ceramic balls, and it is preferable to avoid using metal balls such as stainless steel and steel. This is because, in the case of balls made of metal such as stainless steel or steel, there is a risk that ground cellulose powder such as wood powder may bind to the surface of the balls, or may cause deterioration of the ground powder due to heat generated by contact between the metal balls. Also, fragments of metal balls may be generated, and the fragments may be carried on the surface of the pulverized cellulose and may be different from desired fine powder particles. The dry ball mill may be a closed type or an open-to-atmosphere type. When the closed type ball mill is employed, it is preferable to use an inert gas such as nitrogen gas filled in the mill.

In this ball mill, the balls 3
Is adjusted to be in the range of 90 ° C. to 120 ° C. and the room temperature of the mill body 1 is adjusted not to exceed 80 ° C. The drying process is also performed at the same time. Here, regarding the temperature control of the balls 3 to be used, the capacity of the mill body 1, the amount of the balls 3 put into the mill body 1,
This is performed by adjusting the stirring speed, the amount of cooling by the cooling jacket 2 provided on the peripheral surface of the mill body 1, and the like, based on the material and dimensions of the mill and the charging temperature, amount, and moisture content of the charged pulverized material.

The surface temperature of the ball 3 varies depending on the target material.
It is preferable to set the temperature within the range of from 120 ° C to 120 ° C from the viewpoint of grinding efficiency. However, when a long time is required for grinding, the temperature is preferably from 90 ° C to 100 ° C from the viewpoint of preventing explosion.
If there is a risk of explosion during grinding,
It is preferable that the oxygen concentration in the mill body 1 be within 15%, in which case, for example, a method of continuously supplying nitrogen gas into the ball mill may be adopted.

According to the grinding treatment by such a ball mill, the internal temperature of the mill body 1 rises due to the frictional heat generated by the rotation of the balls 3, while the cooling water circulated through the cooling jacket 2 causes the mill body 1 By adjusting the internal temperature and the surface temperature of the ball 3 to the above ranges,
The raw material is ground and dried under strong heating conditions at the same time as drying, whereby the particle size is adjusted to a desired range, for example, 100 μm or less, and the water content is adjusted to 3.0% by weight or less. It is done. Further, according to this treatment, the ball 3 comes into contact with the raw material pulverized material charged in a coarse powder state, whereby the raw material pulverized material in contact with the ball 3 is pulverized into a finely pulverized material, and the surface of the material is pulverized. Is polished into fine particles having a surface with very few cilia.

That is, when the raw material pulverized material comes into contact with the surface of the ball 3, it is mechanically crushed and abraded to be pulverized.
Since the polishing is performed and the heating and drying are performed at the same time, the water content is efficiently removed. Further, since the fibers in the pulverized raw material are rapidly cooled when separated from the ball 3, the fibers in the raw material pulverized material are rapidly dried by being repeatedly subjected to heating and cooling. The portion is efficiently ground by the ball 3, and as a result, ground cellulose-based fine particles having an independent particle shape with little cilia on the peripheral surface are obtained.
Then, the cellulosic fine powder particles thus obtained are classified, and the particle size in a desired range (for example, 1 to 10 μm, 1 to 10 μm,
0-20 μm, 20-50 μm, 50-100 μm) to obtain the cellulose-based fine particles of the present invention for supporting a white inorganic pigment.

The grinding of the raw material pulverized material can be performed by using, for example, a pulverizer 30 as shown in FIG. 2 instead of the ball mill shown in FIG. This crusher 30
Is based on the principle of stone thinning.
The grinding and polishing processes, that is, the grinding process, are performed by rotating one of the grindstones 31 at a high speed after the raw material pulverized material is put between them with a predetermined gap therebetween.

Here, the grinding stone 31 is a dish-shaped one whose inner surface is gradually inclined upward or downward as it goes to the center, and these are designed so that the center is wide and the peripheral is narrow. They are used by being arranged facing each other. These grindstones 31 have a donut plate shape with a mounting hole 32 formed in the center as shown in FIG. 3, and have a large number of feed grooves 33 formed on the inner surface thereof. The feed groove 33 is for smoothly guiding the workpiece in the radial direction of the grindstone 31 by the centrifugal force generated by the rotation of the grindstone 31.

In order to grind the raw material pulverized material by such a pulverizer 30, the raw material pulverized material is put between the central portions of the two grindstones 31, and then one of the grindstones 31 is moved at a high speed. Rotate. Then, the raw material pulverized material is subjected to centrifugal force, impact force, shearing force and the like between the two grindstones 31 and 31 and is gradually pulverized.
Is moved to the radially outer peripheral side along ..., and in the process, it is pulverized by receiving an impact force and a shearing force, and its peripheral surface (surface) is polished, resulting in the same as that obtained by a ball mill. This is a finely ground cellulose-based fine powder having an independent particle shape with little cilia on the peripheral surface after being ground.

The cellulose fine powder obtained in this manner is also classified in the same manner as in the case of using a ball mill, and adjusted to a desired particle size.
The cellulose-based fine powder of the present invention for supporting an inorganic pigment. As the inorganic pigment to be supported, titanium oxide, lithopone, white carbon, white pigments such as calcium carbonate, and various pigments such as brown pigments such as iron oxide can be used.In particular, titanium oxide which is a white pigment, This is preferable because it has excellent heat resistance and the like. The particle size of the inorganic pigment is adjusted to be sufficiently smaller than the above-mentioned cellulose-based fine powder particles.

As a method for supporting the inorganic pigment on the cellulose-based fine particles, mixed particles of the cellulose-based fine particles and the inorganic pigment are put into a ball mill as shown in FIG. By doing so, the inorganic pigment particles are supported on the peripheral surface of the cellulose fine powder particles. According to such a carrying process by the ball mill method, as described above, frictional heat is generated in the course of the process. Therefore, the temperature control condition of the balls 3 used, that is, the capacity of the mill body 1 and the inside of the mill body 1 The amount of the ball 3 to be thrown, the material of the ball 3,
Dimensions and input temperature and amount of input pulverized material, water content,
Further, an appropriate range such as a stirring speed and a cooling amount by the cooling jacket 2 provided on the peripheral surface of the mill body 1 is determined in advance by an experiment or the like, and is processed under the determined appropriate conditions. That is, the water content of the obtained inorganic pigment-supported cellulose fine powder can be adjusted to 3% by weight or less.

By carrying out such a supporting treatment, the inorganic pigment particles 10 are supported in a biting state on the peripheral surface of the cellulose-based fine particles 11 as shown in FIG.
The upper limit of the amount of the inorganic pigment to be carried is the amount of the inorganic pigment that overlaps the peripheral surface of the cellulose fine powder as base particles and covers the peripheral surface. Is appropriately determined according to the conditions.

The pigment-carrying cellulosic fine particles thus obtained have a color tone substantially the same as the color tone of the inorganic pigment, and agglomeration is observed in both the manufacturing process and the storage process of the supported fine particles. I couldn't. Also,
Since the pigment-carrying cellulose-based fine particles are subjected to attrition treatment and adjusted to have a water content of 3% by weight or less, when they are added to a resin to obtain a molded article,
Prior to this, it can be added as it is without performing a drying treatment, and since the water content is small, it is possible to prevent molding defects and strength reduction due to moisture.

Further, the conventional wood flour has a high moisture content due to its own hygroscopicity, and when the wood flour is to be dried, the wood flour itself is extremely flammable. On the other hand, in the case of the inorganic pigment-carrying cellulose-based fine particles of this example, drying is simultaneously performed in the production process, and the water content is adjusted to 3.0% by weight or less. It does not require subsequent drying, and is therefore extremely excellent as an additive used for resin molding.

The pigment-carrying cellulosic fine particles are mixed with a resin, and extruded or injection-molded to obtain a desired shape, for example, various decorative boards such as a peripheral edge of a house, a baseboard, furniture, and an interior member of a vehicle. By shaping into a plate shape such as a shape, a woody shaped body very close to the texture of natural wood can be obtained. In other words, in the molded body molded in this way, since the cellulose-based fine particles carrying the pigment have been ground, the conventional wood is directly fibrillated into fine powder to form a fiber. Unlike the surface, there is little cilia on the surface and it becomes granular,
Therefore, if the surface of the molded body does not stand, it has a good touch.

(Production Example) A ground material is ground by a ball mill shown in FIG.
m, an average particle size of 50 μm, and a water content of about 6% by weight. Next, the obtained wood flour and titanium oxide having an average particle size of 5 μm are again put into a ball mill, and various conditions, specifically, a stirring speed and a cooling amount by a cooling jacket 2 provided on a peripheral surface of the mill body 1 are measured. By changing, the loading treatment of titanium oxide on wood flour was performed under different drying conditions. The water content of each of the obtained wood flours was examined, and those having a water content of 5% by weight, 4% by weight, 3% by weight, and 2% by weight were selected.

Next, 30 parts by weight of each of the obtained four types of supported fine particles are mixed with 100 parts by weight of the vinyl chloride resin, and further, known additives are mixed and mixed.
Extrusion molding is performed using the obtained two types of mixed powder, and the width is 60
mm, a thickness of 7 mm, and a length of 10 m were obtained.
Observation of the obtained board material by visual inspection revealed that wood chips having a water content of 5% by weight were partially chipped or the like and were insufficient as a product. Also,
In the case of using 4% by weight of wood flour, no chipping or the like was observed, but a small amount of the flour entered the surface, making it difficult to produce a product.

On the other hand, in the case of using wood flour having a water content of 3% by weight and 2% by weight, chipping is of course not observed, moldability is good, and the surface is soft and sticky when touched. It was confirmed that there was no wood texture. Further, using a plate material obtained by using wood powder having a water content of 3% by weight and 2% by weight, one side and the side end face in the length direction are subjected to a grinding treatment with a baffle to roughen the treated surface. On the surface. Next, the surface subjected to the grinding treatment was further embossed with a punch and a die to form a grain-like uneven pattern.

Then, a general paint prepared in advance is applied to the embossed surface of the plate material with a spray gun to clarify the grain pattern, and then the excess paint on the painted surface is removed by a roll wrapped with a nonwoven fabric or the like. I wiped it off. further,
A urethane-based or acrylic-based paint was applied to the painted surface with a spray gun, a flow coater, or the like, subjected to a top coat treatment, and cut into a length of 5 m to obtain two types of baseboards. Each of the obtained baseboards had a clear woodgrain pattern, moderate color unevenness, and had a surface layer very close to that of natural wood due to matting. In addition, since the painted surface was soft and non-sticky, it had sufficient woodiness.

[0032]

As described above, the cellulose-based fine particles according to the first aspect of the present invention are obtained by subjecting the cellulose-based particles carrying a pigment to a grinding treatment to form granular fine particles instead of fibrous particles. Since conventional wood is directly fibrillated into fine powder, it is fibrous, and when mixed and dispersed, the fibrous parts become entangled to form a dumpling or cotton. Since the particulate fine particles are dispersed in an independent state, the fine powder particles carrying the pigment itself have extremely good dispersibility in the resin. Also, because the cellulose-based fine particles are not fibrous but granular,
Like conventional fibrous wood flour, the expansion and contraction caused by adsorbing or releasing water (including moisture) and solvent is extremely reduced. Furthermore, since the water content is 3% by weight or less, even if this is directly added to and mixed with the resin and the resulting mixed material is molded, the occurrence of molding defects or the like due to moisture in the cellulose-based fine powder particles may occur. Can be prevented.

According to a second aspect of the present invention, the inorganic pigment is supported by a ball mill to perform a drying process simultaneously with the supporting process, so that the water content of the resulting fine powder is adjusted to 3% by weight or less. It is. Therefore, since the conventional wood flour itself has a hygroscopic property, its moisture content is high,
In addition, when it is tried to dry it, the wood powder itself is extremely flammable, and it is very difficult to dry it because there is a risk of dust explosion. In contrast, in this manufacturing method, drying is performed simultaneously in the manufacturing process. Thus, the method does not require subsequent drying, and thus is a safe and highly productive method.

[Brief description of the drawings]

FIG. 1 is a fragmentary front view of an open type ball mill.

FIG. 2 is a schematic configuration diagram showing an example of a crusher used for a grinding process.

FIG. 3 is a plan view showing an example of a grindstone of the crusher shown in FIG. 2;

FIG. 4 is a cross-sectional view showing a state where a cellulose-based fine particle inorganic pigment used in the present invention is supported.

FIG. 5 is an enlarged view showing conventional wood flour obtained by directly pulverizing wood into fine powder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mill body 3 Ball 10 Inorganic pigment particle 11 Cellulose-based fine particle 30 Crusher

Claims (2)

(57) [Claims] 1. Cellulose-based fine particles having been subjected to attrition treatment and having an inorganic pigment supported on the surface thereof, wherein the water content is adjusted to 3.0% by weight or less. Fine powder. 2. A coarsely crushed cellulosic material is ground, and the resulting finely ground fine particles are put into a ball mill together with an inorganic pigment, and are ground by the ball mill. A method for producing cellulosic fine particles, wherein the inorganic particles are carried in a state of being bitten by the fine particles, and the water content of the obtained inorganic pigment-carrying cellulosic fine particles is dried to 3% by weight or less.