JPH04224902A - Method for forming wood flour and wood flour and wood flour paint - Google Patents

Abstract

PURPOSE:To prevent cracks and pinholes from being caused on a formed film of paint without detriment to the spreadability of paint by applying cooking or steaming treatment and forcibly drying treatment, as a subsequent step, to the raw material of ground wood flour prior to pulverization processing. CONSTITUTION:A raw material of wood flour is charged into a treating chamber of a rotary cylinder, and a lid is closed to constitute an enclosed treatment space. In this enclosed state, steam is continuously fed into the enclosed treatment space for 30 minutes so as to maintain the internal pressure at 1.9kg/cm<2> and the temperature at 120 deg.C in the enclosed treatment space. The raw material of wood flour is then dehydrated, and drying is carried out by a forcibly drying method until the moisture content becomes within 10%, generally within 8%. After the raw material of wood flour to which steaming treatment and drying treatment have been applied is pulverized continuously for two hours by using a ball mill 1, the pulverized wood flour is classified by using a classifying machine so that the particle size at a classification point becomes 5mum, and 90 to 100% of the total amount of the pulverized wood flour is classified to have the particle size under 5mum. By using the wood flour thus obtained, base coating paint and face coating paint can be prepared.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining fine wood powder, wood powder as aggregate for resin molding whose particle size is 16 μm or less, and a paint containing fine wood powder.

0002

[Prior Art] Attempts have been made to eliminate distortion that occurs during molding by incorporating finely ground wood flour into molding resin, as well as to provide hardness and hygroscopicity to molding resin. Ta. Most of the wood flour used as aggregate for conventional resin molding has been improved to improve its dispersibility when blending into the resin, and to prevent wood acid gas from being generated in the molding machine during resin molding. The typical wood powder used was particle board surface polishing powder that had been hardened with urea resin. The main reason for using such particle board surface polishing powder is that the particle board surface polishing powder is fine and has a "grain" shape with few cilia. That is, by this type of surface polishing method of particle board, fine powder can be easily obtained, and the powder has good slipperiness, and the wood powder has good dispersion and blending properties for powder-like resin raw materials. was.

On the other hand, the method of directly pulverizing wood into fine powder has poor pulverization efficiency, regardless of whether it is pulverized using a dry pulverizer or a wet pulverizer.
Despite the long pulverization process, a large amount of wood flour with a large particle size remains in the pulverized powder, which is disadvantageous. In addition, the obtained crushed wood powder does not have a "granular" shape, and most of it is fibrous, and even if the particle size measured on the short diameter side is several microns, the long diameter side becomes long like cilia. It had some inconveniences. When such conventional wood flour is blended with resin and used, the wood flour often becomes entangled with each other and creates an agglomerated state, which has the disadvantage that it is not uniformly dispersed in the resin material. Furthermore, since the particle size of the pulverized wood powder varies greatly, molded resin products tend to suffer from molding distortions, and the mechanical strength of the product tends to vary depending on the part. Furthermore, due to the irregularity of the grains and the cilia-like shape characteristics, it was not suitable as an aggregate for forming thin resin coatings such as paints or films.

0004

[Problems to be Solved by the Invention] Utilization of the above-mentioned particle board surface polishing powder, which has been developed from this point of view, has the advantage that this surface polishing powder has a granular shape rather than a ciliated shape, and is easier to disperse and blend into resin materials. have. However, the particle size of particle board surface polishing powder varies depending on the material characteristics of the particle board to be polished and the cutting method, such as the mesh of the sandpaper used, and furthermore, it has the disadvantage that it does not have uniform wood characteristics. was there. Furthermore, the surface polishing powder of this type of particle board mainly has a hardened portion of urea-based resin, and has the disadvantage that the moisture absorption and desorption properties and texture peculiar to wood powder are extremely deteriorated.

[0005] From this point of view, we have developed a finely ground wood powder that retains the properties of natural wood, a method for grinding wood powder with a high yield that has such features, and a method for producing wood powder that has such features. An object of the present invention is to provide a paint containing wood powder having the following properties.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a method for forming wood flour according to the invention of claim 1, in which a coarse wood powder obtained by crushing raw material wood such as hemlock or lauan is used. A process of boiling or steaming the pulverized raw material wood powder, and processing the raw material wood flour, which has been subjected to this boiling or steaming treatment so that nignin, tannins, resins, etc. can be separated from cellulose. A drying process in which the moisture content is forcibly dried until it becomes 10 wt% or less, and the raw material wood powder subjected to this drying process is crushed and classified by dry crushing means,
It consists of a pulverization step to produce fine wood powder with a particle size of 16 μm or less.

[0007] Next, the wood flour according to the invention of claim 2 has a particle size of 16 μm or less, and has a water content of 5 μm or less.
It is adjusted and configured so that it is less than wt%, and in particular,
The composition of wood powder is suitable for use in combination with resin. Furthermore, the paint according to the invention of claim 3 has a particle size of 16 μm.
In addition, the composition includes wood flour having a moisture content of 5 wt% or less. Next, the wood powder paint according to the invention of claim 4 has a particle size of 16 μm based on the solid content of the vehicle.
150wt of wood flour with a moisture content of 5wt% or less
% to 300 wt %. Furthermore, the wood powder paint according to the invention of claim 5 has a particle size of 16 μm or less and a water content of 5 w based on the solid content of the vehicle.
It has a composition in which less than t% of wood flour is blended in a range of 15wt% to 25wt%.

[0008]

[Effect] The coarsely ground raw material wood powder is boiled or steamed before the grinding process, followed by a forced drying process, and the moisture content at the time it is made into fine wood powder is 10w. %, the raw material wood powder is structurally brittle and has good breakability during pulverization. The particle size of the wood powder contained in the paint is 16 μm or less,
Since the water content is 5 wt% or less, the spreadability as a paint is not inhibited, and the film functions to prevent cracks, pinholes, etc. from occurring in the formed film.

[0009]

[Embodiment] A typical embodiment of the present invention will be described in detail below. The raw material wood powder used as the object to be crushed may be any type of coniferous wood or leaf wood such as hemlock or lauan. Raw material wood powder is prepared by mechanically crushing these trees or chips to have a particle size finer than 150 mesh, particularly to a particle size of 120 mesh or less. Necessary pretreatment is applied to such raw material wood powder. This pretreatment of the raw material wood powder, which usually contains lignin, tannins, pigments, resins, etc., is carried out to bleach or remove unnecessary substances. A typical example of bleaching is to convert lignin into soluble chlorinated lignin using chlorine, dissolve and remove it with alkali, and bleach the pigment and residual lignin using salsa flour. If it is necessary to increase the whiteness while leaving as much lignin as possible, single-stage bleaching is performed using hydrogen oxide, sodium peroxide, hypochlorite, dithionite, or the like.

[0010] The raw wood powder prepared in this way is put into a rotating cylinder. This rotary cylinder has a jacket attached to cover the circumferential surface of the cylinder, and a processing chamber for feeding raw wood powder, which becomes a sealed processing space when the lid is closed. Raw material wood powder is introduced into the processing chamber of this rotary cylinder, and the lid is closed to create a sealed processing space. Steam is continuously supplied to this sealed processing space for 30 minutes, and the internal pressure of the sealed processing space is reduced to 1. .9kg/cm2 and maintain a temperature of 120°C. At this time, the processing conditions in the sealed processing chamber are maintained by supplying steam into the jacket surrounding the sealed processing chamber of the rotating cylinder and heating this sealed processing chamber from the outside. is preferable. Further, it is preferable that the steaming treatment of the raw material wood powder in the sealed processing chamber is performed while the raw material wood powder in the sealed processing chamber is rotated and agitated by the rotation of a rotary cylinder.

[0011] The processing conditions of the steaming treatment carried out here vary depending on the properties of the input wood powder caused by the species of wood and the input amount, and the processing time is correlated with the chamber pressure and processing temperature in the processing chamber. placed in a relationship. Generally, when the above-mentioned processing conditions are increased, the crushability, which will be explained later, is said to be good commensurate with the increased processing conditions.
It was found that the yield per hour of finely pulverized powder under m was good. It is assumed that this steaming step loosens the bonds between lignin and other fiber-binding substances, cellulose, and hemicellulose, and loosens the structure of cellulose to form loosely bonded fibrils.

[0012] In particular, in a method in which the raw material wood powder in the sealed processing chamber is heated from inside the processing chamber and the outside using a jacket around the outer periphery of the rotating cylinder, the moisture contained in the raw material wood powder in the heated part of the processing chamber is heated. At the same time, the raw wood powder in the heated part is moved to the non-heated part by rotational agitation, rapidly condensing on the heated surface of the wood powder, and the wood powder contains The action of inducing cooling contraction of moisture occurs continuously, which loosens the bonds between lignin and other fiber-binding substances, cellulose, and hemicellulose, and shifts the cellulose structure itself to a state of loose fibrillar bonding.

[0013] The raw material wood powder may be put into a pressure cooker and subjected to a boiling treatment without such a steaming treatment. Even in this case, it is preferable to set the pressure inside the pot so that the temperature inside the pot is around 120° C., and to perform the boiling treatment for 30 minutes or more. In addition, in this boiling process, the gauge containing the raw material wood powder is placed in the pressure cooker and boiled sufficiently, then taken out of the pot and rapidly cooled. The yield when crushing the powder is said to be good.

[0014] The raw material wood flour that has been subjected to the steaming or boiling treatment in this manner is subjected to a draining treatment. This draining treatment may be forcibly performed by a de-squeezing method or a centrifugal separation method, which can shorten the processing time of the next step of drying treatment and has a positive effect on the yield of the raw material wood powder when it is crushed. The raw wood powder is dried by forced drying until the moisture content is within 10 wt%, generally within 8 wt%. The drying treatment for this raw material wood powder is preferably carried out until the moisture content of this raw material wood powder becomes low, preferably 5w.
The drying treatment is performed until the concentration is t% or less, more preferably 3wt% or less. One of the drying methods is to stop the supply of steam to the sealed processing chamber of the rotary cylinder used for steaming the raw material wood powder, and to rotate the rotary cylinder while supplying steam only to the jacket part. The structure is such that the overhumidified air generated in the sealed processing chamber is vented, and the drying processing can be performed in succession to the steaming processing described above. In addition, hot air is blown into the gauge of the raw material wood powder taken out from the pressure cooker to remove the water contained in the raw wood powder, which is continuous with the boiling process in the pressure cooker. It can be a drying process.

[0015] The dried raw material wood powder is pulverized to a particle size of 80 to 150 mesh, preferably 120 mesh or less. The raw material wood powder is pulverized so that the pulverized particle size is 16 μm or less and the moisture content is 5 wt % or less. The pulverized particle size is indicated by the particle size measured on the minor axis side of the pulverized powder, and the pulverized powder preferably has a uniform particle size of 10 μm or less, more preferably 5 μm or less. In addition, from the viewpoint of crushing efficiency and mixing use with resin after crushing, it is preferable that the moisture content of the crushed wood flour is 5 wt% or less, preferably 3 wt% or less, and the moisture content should be as close to 0 as possible. Preferably, it is ground.

From this point of view, it is preferable to use a dry ball mill, which mainly performs grinding, to grind the raw material wood powder. When pulverizing with this dry ball mill, care must be taken not to increase the humidity inside the mill, and especially to prevent the temperature inside the mill from increasing. When the raw material wood powder is crushed by such a dry ball mill, the temperature inside the crusher rises rapidly during the crushing process, and there is a risk of an explosive explosion. A cooling jacket 2 is provided, and cooling water is constantly supplied to the cooling jacket 2, so that the temperature inside the mill is 80°C or less, preferably 70°C.
The grinding operation is carried out so that the temperature is below 0°C. The raw material wood powder in the mill is rapidly heated by the heat of friction between the balls 3 in the mill or between the balls 3 and the raw material wood powder, and the water contained in the raw material wood powder is removed, allowing continued pulverization. The moisture content is reduced to 5 wt% or less, further to 3 wt% or less. The ball mill shown here has a motor 5 with a rotor 4 in the upper part of the mill body 1, and is a batch type with an opening at the top and has an outlet 7 opened and closed by a valve 6 in the conical lower part. The structure is designed to avoid the risk of a violent explosion by releasing the atmosphere. Further, reference numeral 8 indicates a cooling water supply pipe to the jacket 2, and reference numeral 9 indicates a drain pipe thereof, which are designed to be constantly cooled so that the temperature inside the mill does not reach the explosive temperature range. Furthermore, the ball 3 used here is a ceramic ball with a diameter of 3 mm to 5 mm, avoiding the use of stainless steel balls that may cause explosive explosions.

[0017] Instead of such an air-open type ball mill, a closed type ball mill may be used to pulverize the raw material wood powder. When grinding raw material wood powder using this closed type ball mill, it is preferable to set the oxygen concentration in the mill to 15% or less and the temperature in the mill to 80° C. or less. The ball mill shown in FIG. 2 is an example of the ball mill shown in FIG.
A lid 10 is attached to the ball mill, the crushing chamber is isolated from the atmosphere, and the air inside the ball mill is extracted from the pipe 11. Nitrogen gas is sealed into the mill from the pipe 12 to create an inert, sealed atmosphere inside the mill. used as Furthermore, as another method, the raw material wood powder may be pulverized while maintaining the oxygen concentration in the mill at 15% or less by continuously supplying nitrogen gas into the ball mill.

The wood flour thus pulverized is classified to obtain wood flour to be used having the required particle size. Figure 3
The classifier is based on gravity classification, in which unclassified wood flour input from arrow Y is centrifuged by the rotation of rotor 13, classified wood flour is vacuumed out from arrow W, and coarse wood flour that does not meet the classification conditions is removed. Take out the powder from the arrow X. In addition, even in this air volume classification, there is a risk of explosion of minute wood powder inside the classifier, so nitrogen gas is continuously supplied into the classifier from arrow N, and the oxygen concentration inside the classifier is kept within 15% for classification. do. In the classifier shown in FIG. 3, a 0.4KW motor 14 is used to drive the rotor 13 at a speed of 800 to 1000R. P
．． The wood powder was classified while being rotated by M and nitrogen gas was supplied at 200 liters/minute from the arrow N to obtain the classified wood flour shown in Table 1 below.

[0019]

[Table 1]

It should be noted that the ball mill shown in FIG.
．． Using a ball mill with a capacity of 4 liters and 2.4 liters of 3 mm zirconia diameter ceramic balls loaded into the ball mill, the raw material wood powder that had been subjected to the steaming and drying treatment was continued to be pulverized for 2 hours.
Using the classifier shown in Figure 3 above, the particle size at the classification point is 5μ.
When classified into m, the total amount of crushed wood powder was 90w.
t% to 100wt% was under 5 μm. On the other hand, when dry wood flour that has not been subjected to steaming or boiling treatment is crushed and classified under the same conditions, more than 60 wt% of the total amount of crushed wood flour remains as coarse wood flour with a diameter exceeding 5 μm, and the crushing yield is low. It was extremely bad. In addition, when the raw material wood flour subjected to the above-mentioned steaming treatment was crushed and classified under the same conditions as above with a water content of 12 wt%, 50 wt% or more of the total amount of crushed wood flour was found to be coarse wood flour exceeding 5 μm. However, difficulties were observed in terms of pulverization yield.

[0021] In the steaming treatment of the raw material wood powder, efficient steaming treatment and decolorization treatment can be achieved by impregnating the raw material wood flour with a 5% aqueous solution of sodium silicate.

[0022] The wood flour obtained by the above method has an extremely small number of ciliary parts compared to conventional wood flour, and is suitable for use in blending with resin. In hemlock wood powder, fine particles were found in the form of needles, while in lauan wood, fine particles in the form of ellipsoids were often observed. Therefore, various resin molded products can be obtained by blending with various resins such as vinyl chloride and using various molding methods. For example, 25 wt % of the wood powder with a diameter under 16 μm obtained above was blended with an ABS resin and extrusion molded to obtain a table assembly leg. The legs of this table are hard and feel close to natural wood, and could be carved. In addition, 15 wt % of the wood powder with a diameter under 5 μm obtained above was blended with vinyl chloride resin to obtain a soft vinyl chloride sheet with a thickness of 2 mm by extrusion molding. The obtained sheet was soft to the touch, had no sticky feeling, and no air bubbles were observed. Furthermore, a curved arm grip was obtained by injection molding by blending 30 wt % of the wood powder with a diameter under 8 μm obtained above in 6 nylon resin. The obtained arm grip was soft to the touch but hard, and there was no molding distortion. Furthermore, the fluidity of the resin during injection was good, unlike when conventional wood flour was mixed in, and the injection pressure could be set low.

[0023] Next, by blending the above-mentioned wood flour into a paint and using it, wood-like surface characteristics can be imparted to various articles. The objects to be coated here include resin moldings, metal moldings, wood moldings, and synthetic leather, all of which can be coated and used. The finer the particle size of the wood powder used here, the more suitable it is for forming a good coating surface. Further, it is preferable to use wood flour that has a high bulk specific gravity and is not ciliated. Furthermore, it is preferable to use wood flour that has been sufficiently dried to prevent pinholes from forming on the coating surface. From this point of view, wood flour used in paints must have a particle size of at least 16 μm or less and a water content of 5 wt% or less. Incidentally, the mixing rate needs to be set individually depending on the properties of the paint, the purpose of application, etc.

[0024] Using the wood powder obtained above, an undercoat paint and a topcoat paint were obtained. The finer the particle size of the wood powder mixed in this paint, the softer it feels on the hand;
The gloss of the coating surface obtained by blending wood powder with a particle size of μm,
There was no difference in hygroscopicity or colorability. The paint used as a sealant as an undercoat has a content of 15% based on the solid content of the vehicle.
0 wt % to 300 wt % wood flour is used. If the wood powder blended into the sealant vehicle is 300 wt % or more based on the solid content of the vehicle, the sealing surface will become crumbly, making topcoating difficult, and the grain of the wood surface will become blurred. This will cause some inconvenience. In addition, if the blending ratio is less than 150 wt% based on the solid content of the vehicle, the sealing effect will be small and the interlayer adhesion with the paint in the next process will be poor. 20
0 wt% wood flour was blended and used as an undercoat.

[0025] Next, as a top coat, the above-mentioned wood flour is preferably blended in an amount of 15 wt% to 25 wt% based on the solid content of the vehicle. If the amount of wood flour added to the solid content of the vehicle is 25 wt% or more, the formed coating film becomes cloudy and loses its transparency. 15wt
% or less, the formed coating film becomes shiny and a completely non-reflective matte coating film cannot be obtained. From this point of view, in this example, 20w of the above wood flour was added to the solid content of the vehicle.
t% was mixed to make a top coat.

[0026] Such a paint was used by applying it to the surface of natural wood. First, apply the undercoat paint to the wood surface with a brush, etc.
Immediately after application, wipe it off to fill in only the holes for conduits etc. on the wood surface and remove any paint adhering to the wood grain. Next, the top coat is applied to the surface that has been sealed with the undercoat. Paints containing such wood powder have the characteristics that they strongly adhere to the conduits or cell spaces on the wood surface when wiped off during undercoating, and are easily wiped off by the wood grain. Compared to undercoat paints containing extender pigments, the adhesion to conduits or cell spaces on wood surfaces is particularly good. It has the characteristics of being covered with. In addition, paints containing such wood powder have good interlayer adhesion between applied coatings, and do not cause problems such as peeling compared to paints containing inorganic extender pigments such as silica. .

[0027] Furthermore, the above-mentioned top coating paint uniformly eliminates gloss on the surface of the coating film, forming a good non-reflective coating film. Furthermore, when applied to the wood surface, the wood grains are clearly visible from any angle. On the other hand, when a matte paint containing a silica-based extender pigment was used, the painted surface became cloudy, the wood grains seemed blurred, and the grain texture of natural wood was lost.

[0028] There are no restrictions on the coating method for the above-mentioned top coat and undercoat, and any coating method such as brush coating, spray coating, electrostatic coating, flow coater coating, etc. is suitable. When the top coat is applied by spraying, it is best to pass the paint containing wood powder through a 200-mesh wire gauze to avoid agglomeration of the wood powder.

[0029] Typical examples of the wood powder-containing paint for wood surfaces include an alkyd resin as the vehicle for the undercoat and a wood flour content of 200 wt%; is a two-component type urethane resin consisting of polyester polyol resin and HMDI polyisocyanate resin, and the weight is 20wt relative to the vehicle.
% of wood flour. Typical formulation examples of this top coating are shown in Table 2. The formulation example in Table 2 is Paint 1 containing 10.70 wt% of the above-mentioned crushed wood flour and 7.20 wt% of the above-mentioned crushed wood powder.
All of them had good interlayer adhesion and were able to form a completely non-reflective matte coating film with a transparent feel.

[0030]

[Table 2]

[0031]

[Effects of the Invention] In the method for forming wood flour according to the present invention, the object to be crushed is prepared by coarsely crushing it, and after the coarsely crushed raw material wood flour is subjected to boiling or steaming treatment, sufficient drying conditions are applied. Since the grinding is carried out under the same conditions as above, the grinding yield is good, and in particular, it is possible to efficiently grind fine wood flour under 16 μm in size. In addition, the wood powder obtained by pulverization has fewer cilia and has acicular or elliptical particles, which do not aggregate with each other and have good dispersibility when used in resins, etc. . Furthermore, paints containing wood powder under 16 μm have good adhesion between layers, and have excellent sealing effects when used as an undercoat, and are transparent and completely non-reflective when used as a topcoat. It has the feature of being able to form a matte surface.

[Brief explanation of the drawing]

FIG. 1 is a cutaway front view of essential parts of an open-type ball mill.

FIG. 2 is a cutaway front view of essential parts of a closed ball mill.

FIG. 3 is a cutaway front view of the main parts of the classifier.

[Explanation of symbols]

1　Mill body 2. Jacket 3 Ball 4 Rotor 5 Motor 6 Valve 7 Ejection port 8 Supply pipe 9 Drain pipe 10 Lid 11 Pipe 12 Pipe 13 Rotor 14 Motor

Claims (5)

[Claims] Claim 1: Boiling or steaming coarsely crushed raw material wood powder, and forced drying of the boiled or steamed raw material wood powder until its moisture content is 10 wt% or less. A method for forming wood powder, comprising: a drying process, and a grinding process, in which the dried raw material wood powder is pulverized and classified by dry grinding to obtain fine wood powder having a particle size of 16 μm or less. 2. Wood flour characterized by having a particle size of 16 μm or less and a moisture content of 5 wt% or less. 3. A wood powder paint characterized by containing wood powder having a particle size of 16 μm or less and a water content of 5 wt % or less. 4. A wood powder paint comprising 150 wt % to 300 wt % of wood flour having a particle size of 16 μm or less and a moisture content of 5 wt % or less based on the solid content of the vehicle. 5. A wood powder coating comprising 15 wt % to 25 wt % of wood flour having a particle size of 16 μm or less and a water content of 5 wt % or less based on the solid content of the vehicle.