JPH0418498A - Leather powder and production thereof - Google Patents

Abstract

PURPOSE:To obtain the subject superfine leather powder low in impurity content by crushing a leather powder as the raw material and carrying out drying, degreasing, swelling, etc., subsequently carrying out drying, pulverization and classification and then repulverizing the resultant pulverized powder. CONSTITUTION:A leather powder as the raw material is crushed, dried and degreased using a solvent and remaining solvent is then removed followed by water washing, dehydration and swelling by steam. Dryness, pulverization and classification between a fine powder and a coarse powder are subsequently carried out and the resultant fine powder is then repulverized to obtain the objective leather powder having >=85wt.% cortex component, <=2wt.% oil and fat component, <=0.5% total amount of Na<+> ion and Ca<+> ion extractable in water, <=7mum average particle size D50 and <=3mum standard deviation of particle size. The resultant leather powder is used by blending with a resin and can be utilized for an article such as a coating material, a leather, a film, a sheet, a fiber or a molding.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a leather powder and a method for producing the same, particularly an ultrafine leather powder with few impurities and a method for producing the same. (paint film), leather (synthetic leather,
It can be used for products such as artificial leather), films, sheets, fibers, and molded products.

[Background technology]

In order to obtain natural leather-like coatings, films, sheets, fibers (threads), etc., various resins are mixed with leather powder and coated or molded. In the past, the leather powder used here was made by coarsely crushing animal leather powder raw materials such as shaving waste using a crushing means such as a hammer crusher.

However, with such a simple mechanical grinding means, the powders become entangled with each other and become flocculent or lumpy, resulting in only coarse leather powder being obtained. If the particle size of leather powder is large,
Each application is subject to various limitations (for example, coating thickness, surface roughness, thread breakage, etc.), which hinders commercialization.

Therefore, in recent years, various methods and apparatuses for producing fine leather powder have been proposed.

For example, in JP-A-63-156552, coarsely ground leather powder raw material is swollen with steam (called steam steaming).
The method of drying and pulverizing the
In No. 8, after coarsely crushing the leather powder raw material, it is steamed, dried, finely crushed,
JP-A No. 63-286499 discloses a device for degreasing leather powder raw materials with a solvent, steam steaming, drying,
A method of comminution is disclosed.

In addition, the fine leather powder obtained in this way is actually synthesized into molded products as a fine powder with a particle size of 40 μm or less in JP-A No. 63-233828, and as a fine powder with a particle size of 30 μm or less in JP-A No. 1-314789. Used for leather.

[Problem to be solved by the invention]

However, since the fine leather powder obtained by the above method contains a considerable amount of particles with a particle size of 10 μm or more, it is unsuitable for inclusion in thin films, paints, and fibers. That is, for thin films, the particle size is generally 5 to 200 μm, but for surface coatings such as synthetic leather, in which a synthetic resin layer containing leather powder is formed on the surface of the base material, the particle size is 5 to 30 μm.
Furthermore, for paints and fibers, a particle size of 10 μm or less is generally required, and it is preferable to have a particle size as small as possible.

In addition, regarding impurities other than collagen that are normally found in leather itself, for example, the amount and type of impurities have not been considered, so when making various products, during long-term use or storage, humidity, heat, etc. There is a problem in that impurities bleed out on the surface due to the influence of the above, resulting in deterioration of the product's appearance and performance such as color fastness.

An object of the present invention is to provide a leather powder and a method for producing the same, which can produce thin films, paints, fibers, etc., and which can reduce deterioration of product appearance and performance over time.

[Means to solve the problem]

The present invention aims to achieve the above object by focusing on the fact that the above-mentioned problems with conventional leather powder can be solved by re-finely refining fine leather powder and reducing impurities in the leather itself. It is.

That is, the leather powder of the present invention has a cortex content of 85 wt% or more, an oil content of 2 wt% or less, and water-extractable Na+ ions and C.
The total amount of a2+ ions is 0.5 wt% or less, the average particle size D50 is 7 μm or less, and the standard deviation of the particle size is 3
It is composed of micrometers or less.

In addition, the method for producing leather powder of the present invention includes coarsely pulverizing the leather powder raw material, drying, degreasing with a solvent, removing residual solvent, washing with water, dehydration, swelling treatment with steam, drying, pulverizing, fine powder and coarse powder. After carrying out each step of classification, there is a step of re-pulverizing the fine powder to an average particle size D50 of 7 μm or less, and a step of re-pulverizing the fine powder with an average particle size D50 of 7 μm or less, and dividing the fine powder with D50 of 7 μm or less
It is constructed by performing a step of classifying and removing fine powders of m or less.

In the leather powder of the present invention, the characteristic values such as the cortical content are limited for the following reasons.

1) Cortex content of 85 wt% or more: High cortical content means a small amount of impurities, and at the same time, it is an important substance that improves the surface condition and touch feeling of products mixed in leather, paint, etc. It means to be a factor. In other words, the surface condition of the product can be improved more efficiently with a smaller amount of powder when the amount of cortical material is larger.

2) Oil and fat content: 2wt% or less (preferably 0.5wt% or less) The oil and fat content present in animal leather deteriorates due to heat, etc., resulting in bad odor, coloring, and deterioration of surface texture due to bleed-out (sticky, slimy, etc.). It causes a shiny feeling). Therefore, the lower the oil and fat content, the better.

3) Free ions extractable with water (Na”, Ca”)
Total amount of less than 0.5 wt%: If the amount of free ions extracted by water among the impurities polished in leather raw materials is large, when it is made into a product, it will be affected by humidity and heat, and the salt ( For example, Nacl, Na2
SO4, Ca5O*, etc.) bleed out, leading to deterioration of product appearance. In addition to the cations of Na" + Ca2+, free ions that can be extracted with water include Cl"
-, SO, "- anions exist, but the ones that bleed out are only in the form of salts of the counter ions of these ions, so the amount of cations Na +
and Ca2+.

4) Average particle size [150≦7μm and standard deviation σ≦3μm
m: Particle size is a decisive factor for thin-walled products, and if the particle size is large, it will lead to defects due to poor dispersion and deterioration of surface texture (roughness, unevenness). On the other hand, the smaller the particle size, the better the dispersion, and a product with less product defects (voids, thread breakage, etc.) and a surface condition with a good touch feel can be obtained. Furthermore, a small standard deviation means that there are few large particles mixed in in the distribution.

Furthermore, the method for measuring the above characteristic values is as follows.

A) Cortex and oil/fat content: JIS K6550-1976 r Leather Test Method” 6,
7 and 6.4.

B) Free ions extractable with water (Na”, Ca”)
Total amount: 10 g of dry leather powder is stirred in 1001 nl of pure water all day and night to extract free ions in the leather powder. Na in the extract
+Ca''+ is determined by atomic absorption spectrometry and determined as the amount extracted from leather powder.

C) Distribution of average particle size and standard deviation: Several tens of micrometers of leather powder was dispersed in 100 methanol, and the particle distribution was measured using a Coulter Counter (manufactured by Coulter Electronics). Find the deviation.

Note that the density range of leather powder is usually 0.38 to 0.43 g/
cc (after drying leather powder at 120℃ for 2 hours, JIS K6
721). If the density is too large, the particle size will increase and exceed the predetermined average particle size of 7 μm, while if the density is too small, the leather powder will become fibrous or have many loose hairs, making it uniform with the synthetic resin. This is because it may become difficult to disperse.

Next, the method for producing leather powder according to the present invention as described above is carried out in a first manner.
This will be explained in detail according to the manufacturing process diagram in the figure.

Note that the dotted lines or inside the dotted lines in the figure indicate improvements in the method of the present invention.

First, in order to facilitate fine pulverization in the subsequent process, the leather powder raw material is coarsely pulverized to a particle size of about 10 mm or less using a pulverizer such as a show crusher, cutter mill, or hammer crusher. The coarsely crushed leather powder thus obtained usually contains 40 to 60 wt% of water. Note that shaving waste leather, floor leather, etc. can be used as the raw material for the leather powder.

Next, in order to facilitate degreasing (removal of fats and oils) in a subsequent step, this water-containing coarse powder is dried until the moisture content is approximately 20 to 30 wt%.

This dry coarse powder is then degreased using a suitable solvent. Here, n-hexane, benzine, methyllene chloride, acetone, ethyl acetate, toluene, etc. can be used as the degreasing solvent.

Subsequently, in order to remove residual solvent in the coarse powder, the coarse powder after degreasing is heat treated. Since steam is usually used as the heat source for safety reasons, this process is also called steam purging. Other heat sources that can be used include heated nitrogen and heated air.

Next, in the past, it has been known to perform a humidity conditioning process to facilitate fine pulverization in the subsequent process, but in the present invention, free ions (Na+, Ca'') in the leather are extracted and removed, and In order to maintain a certain level of moisture in the coarse powder, a water washing process and a dehydration process by filtration are performed instead of the humidity conditioning process.It is effective to repeat this series of water washing operations several times in a batch process.For example, after removing the solvent, Supply a certain amount of water to the coarse powder,
After stirring for a desired time and bubbling with air if necessary, dehydration is usually repeated several times, preferably 3 to 4 times. At this time, it depends on the amount of water supplied to the coarse powder, but if enough water is supplied, the extraction rate will hardly improve even if the extraction is repeated 5 times or more, and the extraction rate will hardly improve even if the extraction is performed 3 times or more than 4 times. Extraction rate may be obtained. Dehydration is usually performed by filtration (draining or draining) for ease of operation, but other methods such as centrifugal dehydration may also be used.

The amount of water supplied per 1@ is preferably at least 7 times (by weight) the amount of the coarse powder. If it is less than 6 times, there will be a shortage of water due to the bulk density.
The extraction effect is poor because the coarse powder is not fully immersed in water. The higher the amount of water, the higher the amount of extraction per batch, which is advantageous.
There are limitations on the capacity of the washing container and on the dehydration time, so it is actually more effective to repeat the washing operation using the minimum amount of water required for immersion. Therefore, continuous water washing operation requires a large amount of water and is not advantageous, but it is possible.

The water temperature may be room temperature, preferably 30°C or lower. Even if the water temperature is raised further, the extraction rate will hardly change. On the other hand, extraction at high temperatures is undesirable because it causes collagen deterioration.

Through the above series of water washing operations, the total amount of free Na" ions and Ca" + ions (dry weight equivalent) was reduced to 0.5
A water-containing coarse powder having a water content of usually 65 to 70% can be obtained when the amount is less than wt%. Conventionally, the humidity conditioning process was carried out by replenishing the coarse powder after removing the solvent with water until the water content reached 65 to 70%, but in the present invention, the coarse powder is finally Since it usually retains 65 to 70% moisture, the humidity control process can be virtually eliminated just by checking this moisture content.

Here, the reason why a predetermined amount of water is retained or supplied to the coarse powder is as follows. That is, in a dry state, even if pulverization is performed after steam steaming in the next step, pulverization will not proceed.

However, when steam-cooked coarse powder that contains water and is swollen, it is partially denatured by heat, and when dried, it becomes compact and hard, making it easier to crush and pulverize.

Next, in order to facilitate fine pulverization in the subsequent process, the coarsely crushed leather powder after dehydration is subjected to a swelling treatment (steam cooking) with steam while stirring. Note that the conditions for the swelling treatment may be the same as conventional ones, such as a steam temperature of 100 to 130° C. and a steam pressure of 1 to 2.5 kg/cffl G.

Subsequently, in order to facilitate fine pulverization in the subsequent step, the coarsely crushed leather powder after the swelling treatment is dried until the moisture content is approximately 3 wt % or less. This drying step is usually performed by combining preliminary drying using a dryer and main drying using a vacuum dryer. The temperature conditions for preliminary drying and main drying may be the same as before.
For example, 90-100°C and 30-45°C (vacuum drying), respectively.

Next, in order to facilitate re-pulverization in the subsequent process, the coarsely crushed leather powder after drying is processed using a Victory mill, ball mill, colloid mill, etc.
Finely pulverize using a dry pulverizer such as a jet mill, roller mill, or hammer mill until the average particle size is approximately 50 μm.

Next, for the same reason, the obtained finely pulverized leather powder is processed into a fine powder (for example, average particle size D5) using a gravity classifier; an inertial classifier;゜-30 μm or less) and coarse powder (
For example, D50" (60 μm or more) is classified. Coarse powder can be recycled to the pulverization process as necessary.

The above fine grinding and classification process itself is the same as before, but
In the present invention, the fine powder is further pulverized until the D50 is 1 μm or less, and the fine powder with a D50 of 2 μm or less is classified and removed from the fine powder with a D50 of 7 μm or less. . The re-pulverization step can be carried out using a jet mill, a colloid mill, or the like that is suitable for pulverization among the dry pulverizers described above. Further, the classification step can be carried out using a classifier as described above.

In the above method, a series of water washing operations were performed after the degreasing step, but this water washing operation can also be performed before degreasing or after pulverization. However, if the degreasing solvent is hydrophobic before degreasing, it will repel water and will be difficult to penetrate, which is undesirable. In the case of hydrophilic solvents, this is a problem (although it is possible to do so.On the other hand, washing with water after pulverization is practically the only way to separate and remove the water, but it is difficult to filter and tends to form lumps when drying. After pulverization, washing with water and simultaneous dehydration and degreasing using a highly volatile hydrophilic solvent in the filtration process will make filtration somewhat easier and drying easier.

The ultrafine leather powder of the present invention obtained as described above is pre-dried and then blended with various resins to form a synthetic resin 2 mixed with the leather powder 1 of the present invention as shown in FIG. 2(A). , to make leather (synthetic leather, artificial leather) by adhering it to a predetermined thickness on a base material 3 such as cloth, or as a paint containing the leather powder 1 of the present invention as shown in FIG. 2(B), A coating film 4 of a predetermined thickness is formed on the surface of the molded product 5. Further, as shown in FIG. 2(C), a synthetic resin 2 blended with the leather powder 1 of the present invention is spun into a product such as a fiber. Note that the blending ratio is usually in the range of 10 to 99 wt% of resin and 90 to 1 wt% of leather powder.

〔Example〕

The present invention will be explained below with reference to Examples and Test Examples (Application Examples).

Example 1 (Production of water-washed leather powder with chrome tanning D5゜≦7μm) Lump 12 of chrome tanned cowhide waste leather (shaving base)
00kg was crushed using a crusher (manufactured by Hosokawa Micron), and the shape of the original shaving waste leather (max: 1 cm width x 1
After loosening the leather into pieces (2 cm long), the leather is sequentially fed into a coarse crusher (hammer mill manufactured by Odate Co., Ltd., capacity: 600 kg/hr) to produce coarsely crushed leather powder with a particle size of about 10 mm or less. The moisture content of this coarse powder was 40 to 60 wt%.

Next, 350 kg of this wet coarsely crushed leather powder is placed in a vacuum dryer and dried until the moisture content becomes 20 to 30 wt%. Subsequently, 270 kg of this dry coarsely crushed leather powder was put into a degreasing machine, and while feeding n-hexane at 1001/min, the mixture was stirred for 1 hour and 15 minutes, extracted, degreased, and filtered. The residual oil and fat content in the obtained coarse defatted powder was 0.5 wt% or less.

Next, the remaining solvent in this defatted coarsely crushed leather powder was heated at 130'C.
Purge with 2 kg/cnf G steam until the solvent (hexane) odor disappears.

The same degreaser is replenished with 2 liters of water at room temperature, and after stirring for 30 minutes, the water is drained by filtration. This batch water washing operation is carried out four times in total to remove free ions such as metal ions and water-soluble components in the waste leather. Crushed leather powder after filtration and draining is 65-70wt%
contained water.

Next, without adjusting the humidity, it is transferred to a steam steamer and steamed for 45 minutes at 1306 C and 2 kg/cnf G steam while stirring.

Next, the coarsely crushed leather powder after steaming was pre-dried in a dryer maintained at 90°C for 3 hours until the moisture content was 30 to 40% by weight, and then dried in a vacuum dryer at 45°C for 8 hours to reduce the moisture content to 1.
190 kg of dry coarsely crushed leather powder of less than wt% is obtained.

Next, this was pulverized using a Fine Victory Mill (manufactured by Hosokawa Micron Corporation) at 1700 rpm for 2 hours.

Subsequently, this was classified using a cyclone classifier to obtain 35 kg of fine leather powder with an average particle size of 50 to about 30 μm and D50.
= Obtain 155 kg of coarse leather powder with a diameter of about 60 μm.

Incidentally, the coarse leather powder having a D50'' of about 60 μm was circulated to the above-mentioned pulverization step.

Furthermore, 35 kg of this D50” approximately 30 μm leather powder was milled using a jet mill (manufactured by Seishin Enterprise Co., Ltd.) at an air pressure of 8 kg.
/ crj G, air flow rate of 10 rrr/min, and processing amount of 20 kg/Hr, the powder is re-pulverized until the total amount becomes D5°≦7 μm.

Finally, this was classified using a cyclone (manufactured by Seishin Enterprise Co., Ltd.) to produce 33.25kg of ultrafine leather powder with a diameter of 50≦7μm and ultrafine leather powder with a diameter of 5°-2μm or less (bag filter).
Medium) Obtain 1.75 kg.

Because there are few free ions released, only two times are required. ), and in the re-pulverization process, fine leather powder with D50 = approximately 30 μm is
The same method as in Example 1 was repeated except that D50
23.75 kg of ultrafine leather powder of ≦7 μm is obtained. In addition,
Aldehyde tanned products are more difficult to grind than chrome tanned products, and the yield of fine powder with D50 = approximately 30 μm is 25 kg.
Therefore, the amount used was reduced compared to Example 1. 0SO = yield of approximately 60 μm coarse powder is 165 kg
There were many. The amount of ultrafine leather powder with D50≦2 μm in the bag filter is 1.25 kg.

Comparative Example 1 Chrome-tanned cowhide waste leather (same as the raw material in Example 1), which is a raw material for leather powder, was used without any treatment.

Aldehyde-tanned cowhide scraps (shaving scraps) were used instead of chrome-tanned cowhide scraps, and the batch was washed twice and removed by water washing. Leather (same raw material as in Example 2) was used without any treatment.

A fine leather powder of approximately 30 μm was produced.

Comparative Example 3 Crushed leather powder after steam purging (leather powder raw material is chrome-tanned cowhide scraps) is directly transferred to a steamer without washing with water, and the moisture content of this coarse powder becomes 65 to 70 wt%. After replenishing water and controlling the humidity, the same method as in Example 1 was repeated, except that steaming was performed, and re-pulverization and subsequent steps were omitted. = Fine leather powder of approximately 30 μm was produced.

-Yo'm1 The coarsely crushed leather powder after steam purging (the raw material for the leather powder is aldehyde tanned cowhide scraps) is transferred to the steamer as it is without washing with water, and the moisture content of this coarse powder is 65 to 70 wt%.
The same method as in Example 2 was repeated, except that water was added and the humidity was adjusted until steaming was carried out, and re-pulverization and subsequent steps were omitted. D6° Comparative Example 5 The fine leather powder of D50 obtained in Comparative Example 3 was re-pulverized using a jet mill in the same manner as in Example 1, and then classified using a cyclone to produce ultrafine leather powder of D5 [1578 m]. did.

Comparative Example 6 The fine comparative powder with a D50 of approximately 30 μm obtained in Comparative Example 4 was re-pulverized using a jet mill in the same manner as in Example 1, and then classified using a cyclone to produce an ultrafine leather powder with a D50≦7 μm.

Table 1 shows the properties of the comparative powder obtained as described above.

Further, details regarding the particle size distribution in Table 1 are shown in Table 2.

The touch feeling was also good.

20 parts by weight of the leather powder produced in Example 1 and 80 parts by weight of the resin component of the two-component polyurethane paint were stirred and mixed with 100 parts by weight of thinner as a solvent, and this was applied to an ABS resin molded product and dried (solvent evaporation). The temperature is 65°C99
Even in a 24-hour humidity test at 5% RH, no white bleed was observed on the surface of the coating because there were few water-soluble free ions in the leather powder, and the surface condition of the coating was smooth because the particle size of the leather powder was small. The touch feeling was also good.

The vinyl chloride leather that had been given a gravure surface finish with a mixture of 20 parts by weight of the leather powder produced in Example 1 and 80 parts by weight of vinyl chloride resin in an emulsion state was heated at 70°C for 4 hours while supplying water to prevent the leather surface from drying out. No white bleat was observed on the surface of the leather even when the leather powder was maintained at 100 mL, since there were few water-soluble free ions in the leather powder. Moreover, since the leather powder was small, the surface condition of the coating film was smooth and the touch feeling was good.

ABS was prepared in the same manner as in Test Example 1, except that the leather powder produced in Example 2 was used instead of the leather powder produced in Example 1.
-65°C995 when applied to resin molded products and dried.
%RH, 24-hour moisture resistance test, no white bleed was observed on the coating surface due to the small amount of water-soluble free ions in the leather powder, and the surface condition of the coating was smooth due to the small particle size of the leather powder. 20 parts by weight of the leather powder produced in Example 1 and 80 parts by weight of the polyurethane resin are mixed with dimethylformamide as a solvent and stirred, and the artificial leather (or synthetic leather) is treated with Clavia surface treatment and the leather surface dries for 4 hours. Even if the temperature was maintained at 70°C while supplementing with water to prevent this from occurring, no white bleed material was observed on the leather surface because there were few water-soluble free ions in the leather powder. Moreover, since the leather powder was small, the surface condition of the coating film was smooth and the touch feeling was good.

ABS was prepared in the same manner as in Test Example 1, except that the leather powder produced in Comparative Example 3 was used instead of the leather powder produced in Example 1.
When applied to resin molded products and dried, 65°C295%
In the RH and 24-hour moisture resistance test, due to the large amount of water-soluble free ions in the leather powder, white bleed material appeared prominently on the coating surface, resulting in an abnormal appearance of the product. Furthermore, since the particle size of the leather powder was larger than in Example 1, the surface condition lacked smoothness in relation to the coating thickness, and the touch feeling was somewhat poor. In addition,
The same is true for paints and leather, but when analyzing bleat products, crystals of CaSO4, NazSO*, and NaCl were confirmed, and these were found to be components of tanning agents contained in the raw material shaving waste leather. There is.

ABS was prepared in the same manner as in Test Example 1, except that the leather powder produced in Comparative Example 4 was used instead of the leather powder produced in Example 1.
When applied to resin molded products and dried, 65°C295%
In the RH and 24-hour humidity test, since there are not many water-soluble free ions in the leather raw material, the white bleat on the surface of the coating film is not noticeable, and the appearance of the product is inevitably poor. Also, since the particle size of the leather powder was larger than in Example I, the surface condition lacked smoothness and the touch feeling was somewhat poor in relation to the coating thickness.

ABS was prepared in the same manner as in Test Example 1, except that the leather powder produced in Comparative Example 3 was used instead of the leather powder produced in Example 1.
When applied to resin molded products and dried, the temperature is 65°C995%.
In the RH and 24-hour moisture resistance test, white bleat material appeared prominently on the coating surface due to the large amount of water-soluble free ions in the leather powder, resulting in an abnormal appearance of the product. Furthermore, since the particle size of the leather powder was larger than in Example 1, the surface condition exceeded a matte tone and became rough due to the relationship with the coating thickness, resulting in poor touch feeling.

ABS was prepared in the same manner as in Test Example 1, except that the leather powder produced in Comparative Example 4 was used instead of the leather powder produced in Example 1.
When applied to resin molded products and dried, the temperature is 65°C995%.
In the RH and 24-hour moisture resistance test, since there are not many water-soluble free ions in the leather raw material, the white bleat on the surface of the coating film is not noticeable, but the appearance of the product is inevitably poor. Also, since the particle size of the leather powder was considerably larger than in Example 1,
In relation to the coating thickness, the surface condition went beyond matte to rough and the touch feeling was poor.

PVC leather whose surface was finished in the same manner as in Test Example 3 except that the leather powder produced in Comparative Example 3 was used instead of the leather powder produced in Example 1 was soaked in water for 4 hours to prevent the leather surface from drying out. When maintained at 70℃ while replenishing
Due to the large amount of water-soluble free ions in the leather powder, white bleed material appeared on the leather surface, resulting in an abnormal appearance of the product.

Furthermore, since the particle size of the leather powder was larger than in Example 1, the surface condition lacked smoothness and the touch feeling was somewhat poor in relation to the coating thickness.

Artificial leather that had been given a gravure surface finish in the same manner as Test Example 3 except that the leather powder produced in Comparative Example 3 was used instead of the leather powder produced in Example 1 was soaked in water for 4 hours to prevent the leather surface from drying out. If the temperature is maintained at 70℃ without replenishing the
Due to the large amount of water-soluble free ions in the leather powder, white bleed material appeared prominently on the leather surface, resulting in an abnormal appearance of the product. Also, since the particle size of the leather powder was larger than in Example 1, the surface condition lacked smoothness and the touch feeling was somewhat poor in relation to the coating thickness.

ABS was prepared in the same manner as in Test Example 1, except that the leather powder produced in Comparative Example 5 was used instead of the leather powder produced in Example 1.
When applied to resin molded products and dried, the temperature is 65°C995%.
In the RH, 24-hour moisture resistance test, white bleed material appeared significantly on the coating surface due to the large amount of water-soluble free ions in the leather powder, resulting in an abnormal appearance of the product. Furthermore, since the particle size of the leather powder was the same as in Example 1, the surface condition of the coating film was smooth and the touch feeling was good.

After coating and drying the ABS resin molded product,
In a 24-hour humidity test at 5°C, 995% RH, there are not many water-soluble free ions in the leather raw material, so white bleat on the surface of the coating film is not noticeable, and the appearance of the product is inevitably poor. Furthermore, since the particle size of the leather powder was the same as in Example 1, the surface condition of the coating film was smooth and the touch feeling was good.

Table 3 shows details of the results of the above test examples and comparative test examples.

Same as Test Example 1 except that the leather powder produced in Comparative Example 6 was used instead of the leather powder produced in Example 1 [Effects of the Invention] As explained above, according to the production method of the present invention, Since ultra-fine leather with few impurities can be obtained, using this kind of leather powder makes it possible to manufacture thin films, paints, fibers, etc., and also reduces the deterioration of product appearance and performance over time. .

[Brief explanation of drawings]

Figure 1 is a manufacturing process diagram of an example of the leather powder of the present invention, and Figure 2 (A
), (B) and (C) are schematic diagrams of products manufactured using the leather powder of the present invention as leather (synthetic leather, artificial leather), paint (as a coating film), and fiber, respectively. DESCRIPTION OF SYMBOLS 1... Leather powder of this invention, 2... Resin, 3... Base material, 4... Coating film, 5... Molded article.

Claims (2)

[Claims] (1) Cortex content is 85 wt% or more, oil content is 2 wt% or less, total amount of water-extractable Na^+ ions and Ca^2^+ ions is 0.5 wt% or less, and average particle size D_5_
0 is 7 μm or less and the standard deviation of the particle size is 3 μm or less. (2) The leather powder raw material was subjected to the following steps: coarse pulverization, drying, degreasing with a solvent, removal of residual solvent, washing with water, dehydration, swelling treatment with steam, drying, pulverization, and classification into fine powder and coarse powder. After that, the fine powder is further divided into an average particle size D_5_0=7μ
Step of re-pulverizing to below m and the above D_5_0=7 μm
A method for producing leather powder, which comprises performing the step of classifying and removing fine powders of D_5_0=2 μm or less from the following fine powders.